SPECIAL Workshop 2000

Abstracts (see programme)

All abstracts are ordered alphabetically according to the first author.

  1. Aplin, K. L., and R. G. Harrison; Modern atmospheric ion measurements
  2. Arnold, N.; Space plasma forcing of the winter stratosphere via planetary wave coupling with the thermosphere
  3. Bago, E. P., and C. J. Butler; Sunshine, clouds and cosmic rays
  4. Baranyi, T., and A. Ludmany; Averages of the IMF components of the different type of activities in the GSE system
  5. Bochnícek, J., P. Hejda, and J. Pýcha; Possible geomagnetic and solar activity effects on pressure and wind directions in the winter lower troposphere
  6. Chum, J., J. Vojta, and J. Lastovicka; High Altitude Lightning Observation System - HALOS
  7. Frank-Kamenetsky, A., and G. Burns; Space processes and electrical changes influencing atmospheric layers
  8. Füllekrug, M.; Turning sprites upside down: A proposal
  9. Goldberg, R. A., W. D. Pesnell, and C. H. Jackman; Do precipitating electrons cause long-term changes in atmospheric ozone?
  10. Grewe, V.; Modelling the NOx - Production by lightning and its impact upon the atmosphere
  11. Harrison, R. G., and K. L. Aplin; Atmospheric ion-aerosol interactions
  12. Inan, U. S.; Conjugate purple sprites, relativistic electron curtains, sprite halos, early/fast conductivity changes, and electron precipitation events
  13. Israelsson, S.; Effect of wind on antennas collecting the vertical air-earth electric current
  14. Kristjansson, J. E., and J. Kristiansen; On possible connections between cosmic rays, global cloud cover and climate
  15. Lam, M. M., and A. S. Rodger; The effect of Forbush decreases at South Pole
  16. Lastovicka, J.; Effects of geomagnetic storms and Forbush decreases of cosmic ray flux on total ozone at higher middle latitudes
  17. Mareev, E. A.; Aerosol effects on terrestrial electromagnetic enviroment and their EHD description
  18. Morozova, A. L., and M. I. Pudovkin; Variations of atmospheric pressure during SPE and Forbush-decreases
  19. Morozova, A. L., M. I. Pudovkin, and P. Thejll; Variations of pressure altitudinal profiles at high-latitudinal stations
  20. Neubert, T., T. H. Allin, H. Stenbaek-Nielsen, E. Blanc, M. Füllekrug, and G. Satori, Results from the first European Sprite Observation Campaign
  21. Price, C.; Schumann resonance as an indicator of upper tropospheric water vapor
  22. Price, C.; Observations of ELF sprites from Israel
  23. Pulinets, S. A., K. A. Boyarchuk, V. V. Hegai, and D. R. Shklyar; Ground-atmosphere-ionosphere-magnetosphere coupling conception
  24. Rycroft, M. J.; Some suggested objectives for the SPECIAL meeting in Lindau, 8 to 11 November 2000
  25. Schlegel, K.; Solar and geomagnetic data and data sources for SPECIAL investigations
  26. Schlegel, K.; Solar activity and lightning
  27. Svensmark, H.; Atmospheric ionisation by cosmic rays and Earth's cloud cover.
  28. Tammet, H., and S. Israelsson; Variation of fair weather atmospheric electricity at Marsta Observatory, Sweden, 1993-1998. (Extended abstract available as PDF only.)
  29. Tinsley, B. A.; Electroscavenging and the production of ice in cold clouds and of large condensation nuclei in warm clouds
  30. Tonev, P. T.; Lightning-induced quasi electrostatic fields above equatorial thunderstorms
  31. Troshichev, O. A., E. S. Gorshkov, S. N. Shapovalov, and V. V. Sokolovsky; Influence of the gravitational field variations on processes in animate and inanimate nature
  32. Troshichev, O. A., V. Ya. Vovk, and L. V. Egorova; Disturbances in the wind system above the Antarctic caused by variations of cosmic rays and their relationship to the southern atmospheric oscillations
  33. Troshichev, O. A., L. V. Egorova, and V. Ya. Vovk; variations in temperature and atmospheric pressure in the southern near-pole region: Effects of the galactic cosmic rays, solar protons and interplanetary shocks
  34. Tulunay, Y, E Tulunay, and E T Senalp; Neural network based approach to forecast ionospheric parameters
  35. Turunen, E., Th.Ulich, P. Verronen, and E. Kyrölä; Effects of precipitating high energy particles in the mesosphere: Present and future applications of the Sodankylä Ion Chemistry Model
  36. Tyler, R.; The potential for monitoring the global circuit from ocean straits
  37. Ulich, Th.; Ground-based monitoring of space weather in Finland and Northern Scandinavia
  38. Ulich, Th.; How accurately do we know the lengths of the sunspot cycles?
  39. Ulich, Th., M. Füllekrug, and J. Manninen; Large scale campaign for simultaneous measurements of ionospheric conductivity profiles by ELF receivers, incoherent scatter radars, and riometers in Northern Fenno-Scandia
  40. Zieger, B., and G. Satori; Solar and tropospheric variability effects on Schumann resonances

  1. Modern atmospheric ion measurements

    Karen L. Aplin(1) and R. Giles Harrison(2)

    1. Atmospheric Sciences Research Group, Department of Environmental Sciences, University of Hertfordshire, Hatfield Campus, College Lane, Hatfield, Herts., AL10 9BD UK
    2. Department of Meteorology, The University of Reading, PO Box 243, Earley Gate, Reading, RG6 6BB UK

    There is a long history of laboratory experiments establishing nanometre-sized aerosol formation from air ions, resulting from radiolytic processes [e.g. 1,2]. However, any mechanism of atmospheric aerosol particle formation in the atmosphere at typical atmospheric radioactivity levels remains uncertain. Recent theoretical work suggests that ion-ion recombination, and other electrically enhanced processes can explain observed rates of atmospheric condensation nucleus formation [3]. Measurement of atmospheric ion growth is clearly necessary to corroborate this theory. Since the electrical mobility of ions is inversely related to their mass, then ion mobility spectra can directly monitor ionic growth. A new Programmable Ion Mobility Spectrometer (PIMS) instrument has been developed which can measure ions in two modes, facilitating self-calibration. A new numerical approach to calculate ion mobility spectra has been developed. This exploits the programmable features of the instrument, permitting self-validation of ion mobility spectra, and detection of ion-induced condensation nucleus formation.

    [1] Bricard J. et al, Formation and evolution of nuclei of condensation that appear in air initially free of aerosols J. Geophys. Res., 73, 448 (1968)
    [2] Burke T.P and Scott J.A., The production of condensation nuclei by alpha radiation, Proc. Roy. Irish Acad., 73, A, 151-158 (1973)
    [3] Yu F. and Turco R.P., Ultrafine aerosol formation by ion-mediated nucleation, Geophys. Res. Lett., 27, 883-886 (2000)

  2. Space plasma forcing of the winter stratosphere via planetary wave coupling with the thermosphere

    Neil Arnold

    In the winter months, the middle atmosphere circulation is dominated by dynamical forcing due to the absence of strong diabatic heating. In contrast, the thermosphere experiences considerable perturbations due to energetic particles from the solar wind travelling along open field lines at high magnetic latitudes. Waves propagating upwards from the lower atmosphere are strongly influenced by these changes and through a process related to 'downward control' exert a forcing on the stratosphere. Using a three-dimensional model of the atmosphere between ~10-130 km, several dozen perturbation studies have been carried out. Realistic geomagnetic conditions can bring about changes in the stratosphere comparable to those achieved using variations in ultraviolet flux between solar minimum and solar maximum.

  3. Sunshine, clouds and cosmic rays

    E. P. Bago and C. J. Butler

    Armagh Observatory

    Our analysis of the new ISCCP D2 cloud data reveals that there is a correspondence between the low cloud cover and the galactic cosmic ray flux. Using several proxies for solar activity and the radiative forcing for the ISCCP cloud types, we estimate the possible impact that such a solar-terrestrial connection may have on climate and find that much of the warming of the past century could be quantitatively accounted for by the direct and indirect effects of solar activity. We have also analysed the behaviour of the available proxies for cloud cover existing for the last century, searching for the cloud cover decrease predicted by the low cloud - cosmic ray flux correlation. The sunshine records and the synoptic cloud records both indicate that the total cloud cover over the oceans has increased during the past century but the evidence for a low cloud decrease is unclear.

  4. Averages of the IMF components of the different type of activities in the GSE system

    T. Baranyi and A. Ludmany

    Heliophysical Observatory of the Hungarian Academy of Sciences, Debrecen, P.O.Box 30, Hungary

    In the previous papers (Baranyi et al. 1998, GRL 25, 2269, and references therein) we studied the tropospheric responses by using the classified events in aa-index and the surface temperature data of several stations on the Earth's northern hemisphere. It was found that the solar particle events originating from the Sun's polar regions affect the troposphere in a way that is opposite to solar particle events from the Sun's active belt regions. On the other hand, there is a 22-year periodicity in which the solar active belt's effects cause opposite tropospheric effects in the alternating dipole cycles, and its sense in a given solar cycle is opposite to that given to the polar effects. Where this phenomenon is detectable depends on the geographic position. The complex behavior found on the eastern side of the Earth's northern hemisphere is reversed on the western side of it, and the separating border lies close to the meridian crossing the magnetic pole. These results imply that the physical mechanism linking the solar and tropospheric changes may be sensitive to the specific spatial conditions and magnetic polarity distributions. The Bz component of the IMF determines the rate of energy transfer: when Bz is negative, considerably more energy penetrates into the near-Earth environment than in the case of Bz positive. But the By component can modulate this process, causing marked asymmetries in magnetospheric convective flow patterns at high latitudes. As the z-component of the electric field is altered due to the reversal of the By component, By is the most plausible candidate for the cause of the reported effects. Tinsley (Space Sci. Rev. 2000) found that the linkage between the solar particles and atmospheric circulation is the change in Jz air-Earth current density in the global electric circuit due to solar wind modulation. On the bases of these results and theoretical expectations we proposed that the magnetic flux ropes coming from the active region belts might have a By component which differs from that of the background IMF. In the present paper we studied the statistical properties of the By and Bz components of the different types of corpuscular events in the GSE system and their dependence on the solar dipole cycles by using the OMNI data.

  5. Possible geomagnetic and solar activity effects on pressure and wind directions in the winter lower troposphere

    J. Bochnícek, P. Hejda, and J. Pýcha

    Geophysical Institute ASCR, Prague 4, Czech Republic

    Distributions of surface air-pressure fields of northern winter troposphere in the years 1952-1998 were analyzed. Composite maps showed, that character of the distribution of those fields depends on the level of geomagnetic/solar activity and that after stratifying the pressure data according to the QBO phases the dependence on the activity level increases. It appears that the distribution of these fields during the QBO-east phase is more closely associated with geomagnetic activity than with solar activity, whereas during the QBO-west phase the effect of both activities is comparable. Composite maps of the wind magnitudes and prevailing directions showed marked differences between high and low levels of activities and east and west phases. The conclusions of Venne and Dartt (J. Climate, 1990) concerning strong northward wind component near Greenland and Iceland during the solar minimum and QBO-west phase were confirmed.

  6. High Altitude Lightning Observation System - HALOS

    Jaroslav Chum, Jaroslav Vojta, and Jan Lastovicka

    Institute of Atmospheric Physics, Bocní II, 141 31 Prague 4, Czech Republic

    The main aim of the development of HALOS system is to detect effects of lightnings in the middle atmosphere and lower ionosphere, particularly simultaneous detection of optical phenomena like red sprites and blue jets on the one hand, and electromagnetic phenomena (VLF/ELF) on the other hand, from one platform (satellite or balloon).

    The following set of instruments would ensure complex observations of the above phenomena:

    1. Analysis of electromagnetic waves:
      • 3-axis DC magnetometer
      • 3-axis search coil magnetometer
      • 3-axis electric field measurement
    2. Optical measurements:
      • Photometers on spectral lines of supposed emissions: neutral N2 at 650-700 nm and 730-780 nm, atomic oxygen at 540-640 nm (557.7, 630, 636.4 nm) - red sprite, N2+ emission at 425-430 nm, N2+ and N2 2PG emissions at 330-400 nm - blue jet
      • Black and white survey camera, record triggered by photometer
    3. Environment characteristics:
      • Temperature measurement
      • Pressure measurement
      • Electric conductivity measurement
      • Wind measurement
    4. Acoustic measurement:
      • Microphone

    The Institute of Atmospheric Physics, Prague has sufficient experience with constructing space instruments. We designed and constructed, among others, five MAGION subsatellites, instruments for electric field measurements, search coil magnetometer, and supporting systems like attitude determination, telemetry and command system. We are also able to ensure the design of photometers and optionally of other instruments.

  7. Space processes and electrical changes influencing atmospheric layers

    A. Frank-Kamenetsky(1), and G. Burns(2)

    1. Arctic and Antarctic Research Institute, St. Petersburg, Russia
    2. Australian Antarctic Division, Kingston, Australia

    Variations in the atmospheric, near-surface vertical electric field measured at the Southern near-pole station Vostok (78.5(S, 107(E, L=75.0) in 1998, 1999 and 2000 have been analyzed in conjunction with changes of the ionospheric electric field and interplanetary magnetic field (IMF). Comparison of 1-minute data on electric field and meteorological observations makes it possible to establish quantitative criteria for "fair weather" conditions. More then 200 days satisfied the "fair weather" conditions have been selected, i.e. days with absence of high winds, falling or drifting snow, clouds, and electric field "pollution" from the station's power plant.

    It is shown that the average diurnal variation of Ez for these days follows the global geoelectric field "fair - weather" diurnal variation, which describes the global electric circuit formed by the thunderstorm activity. The Ez diurnal variation shows strong seasonal dependence: it is maximal in summer but gradually reduces through the equinoctial months and is almost negligible during the austral winter. We demonstrate the direct association of the geoelectric field with the cross polar cap potential difference: Ez at Vostok is strongly affected by variations in IMF Bz component. The IMF Bz effect is mainly seen at dawn (Ez decreases with Bz ) and dusk (Ez increases with Bz). The PC index of magnetic activity, characterizing the general state of the magnetosphere, can be used a proxy for the atmospheric electric field in these time intervals. The influence of By is dominant during geomagnetic daytime hours (1100-1400 UT at Vostok): Ez increases with By in the range from -10 to +10 nT.

  8. Turning sprites upside down: A proposal

    Martin Füllekrug

    In this talk I want to draw the attention to the possibility of studying possible particle precipitation effects on the Earth's weather by detailed theoretical studies of the inverse process, i.e. particle acceleration from the tropopause to the ionosphere in the context of Sprite generation.

  9. Modelling the NOx - Production by lightning and its impact upon the atmosphere

    Volker Grewe

    DLR-Institut fuer Physik der Atmosphaere, Oberpfaffenhofen, Germany

    Tropospheric ozone is one of the greenhouse gases, which is anthropogenically changed since pre-industrial times. It is produced mainly in the troposphere. One of the most important precursors is NOx. Its sources are poorly known. A natural source, which realeases NOx in the whole atmosphere is lightning. Here we present parametrizations of the horizontal and vertical distribution of lightning, the related 4-dimensional NOx production and the impact on the global NOx and ozone distribution. Calculated flash frequencies, NOx and ozone concentrations will be compared with satellite and aircraft measurements.

  10. Do precipitating electrons cause long-term changes in atmospheric ozone?

    R. A. Goldberg(1), W. D. Pesnell(2), and C. H. Jackman(1)

    1. NASA/Goddard Space Flight Center
    2. Nomad Research, Inc.

    Prior to the launch of UARS, highly-relativistic electron precipitation (HRE) events containing significant fluxes of electrons with E > 100 keV were predicted to deplete stratospheric and mesospheric ozone up to 20%. The chemical signature of an HRE is the depletion of ozone within the magnetically controlled region of deposition and a distinct boundary equatorward of the L=3 magnetic shell. We have searched for these effects in three of the instruments on UARS. High resolution data from CLAES and MLS did not show a definitive effect in the ozone mixing ratio during the May 1992 HRE, the most intense detected by UARS, but those instruments were at the altitude limit of their respective inversion algorithms. Using the multiple viewing angles of HRDI, we can compare mesospheric ozone at similar local solar times before, during, and after the same HRE, removing some of the ambiguity caused by the diurnal cycling. Furthermore, the altitude coverage of HRDI spans the region of maximum predicted ozone depletion and above, allowing a comparison of the measured and predicted altitude profiles. Our analysis demonstrated that ozone in the upper atmosphere does not respond significantly to HRE events. High-energy electrons create ions at altitudes where ozone chemistry is dominated by a diurnal cycle and HOx-catalyzed reactions. Recovery of the ozone depletion caused by an HRE is as close as the next sunset.

  11. Atmospheric ion-aerosol interactions

    R. Giles Harrison and Karen L. Aplin

    Department of Meteorology, University of Reading, P.O. Box 243, Earley Gate, Reading RG6 6BB, U.K.

    There is a substantial amount of laboratory work which shows that ultrafine particle formation can occurs as a result of the production of large quantities of small ions. It is of climatic interest to establish if similar ultrafine particles can be formed in the atmosphere, because of their significance as condensation nuclei [1] and possibly as cloud condensation nuclei [2]. Ionisation in the atmosphere from cosmic sources is ubiquitous but at much smaller intensities than the laboratory studies. Conventional ion-aerosol theory does not allow for a source term of aerosol related to the ion concentrations and expresses small ion concentrations in terms of their removal by aerosol. The are many sources of variability in condensation nuclei (CN) concentrations in the atmosphere occur near the surface. Interactions between surface radioactivity, condensation nuclei and atmospheric ions are investigated here experimentally, and some of the variability in surface CN is found to be related to variations in surface radioactivity.

    [1] Harrison, R. G. (2000) Cloud formation and the possible significance of charge for atmospheric condensation and ice nuclei (in press Space Science Reviews)
    [2] Svensmark, H., and Friis-Christensen, E. (1997) Variations of cosmic ray flux and global cloud coverage - a missing link in solar-climate relationships. J Atmos Solar-Terr Phys 59, pp1225-1232

  12. Conjugate purple sprites, relativistic electron curtains, sprite halos, early/fast conductivity changes, and electron precipitation events

    Umran S. Inan

    Space, Telecommunications and Radioscience (STAR) Laboratory, Stanford University, USA

    A brief background and a discussion of recent results will be provided, many of which were realized in the context of the recent PhD dissertations completed by N. Lehtinen (Mar 2000), M. Johnson (Sept 2000), and C. Barrington-Leigh (Sept 2000), and in the ongoing work Ph.D work of E. Gerken. The work of Lehtinen [2000] indicate that relativistic electron beams driven upward by intense thundercloud fields may populate the radiation belts in the form of trapped electron curtains and may produce detectable effects in the geomagnetically conjugate region, including gamma-rays, optical emissions and ionization changes. Results of high-speed photometric and video imaging measurements, interpreted by Barrington-Leigh [2000] in the context of a numerical model of the generation and propagation of quasi-electrostatic (QE) and electromagnetic (EMP) fields, indicate that the diffuse glows that are often seen to occur above the streamer regions of sprites are not elves produced by the lightning EMP (as was commonly believed previously) but that they are instead produced by QE fields. The work of Johnson [2000] indicates that early/fast conductivity disturbances have lateral extents no less than ~90 km in the 80-90 km altitude range and that oblique (nonducted) whistler waves from lightning discharges can precipitate electrons over large ionospheric regions of ~2000 km in lateral extent. Recent telescopic measurements [Gerken et al., 2000] reveal the existence of highly complex fine structure in sprites, with transverse scales ranging from ~200 m to <40 m, generally consistent with theoretical predictions of streamer structure [Pasko et al., 1998], and indicating the presence of persistent ionization, but also exhibiting a broader variety and spatial scales than expected. We will also present some very recent SAMPEX satellite observations of lightning-induced precipitation of energetic (>150 keV) radiation belt electrons, which appear to be ubiquitously driven by thunderstorms worldwide, indicating that lightning on this planet may be significant in determining the loss rates of energetic electrons in the inner belt and slot regions.

  13. Effect of wind on antennas collecting the vertical air-earth electric current

    Sven Israelsson

    Department of Meteorology, University of Uppsala, Sweden

    The electrodynamics of antennas collecting the fair weather electric air-earth currents are investigated, to find out the effect of the wind and turbulence. A horizontal long-wire antenna, horizontaland vertical flat antennas were considered.

    A model given by Lelwala and Tuomi was tested where a horizontal wind is assumed. The model of a horizontal long-wire antenna consists of a set of equations for the motions of air ions and the solution is found by shooting analytical techniques. The solution shows that the resultant effect of wind on the current collected by the antenna is zero. Further it shows that the conduction current collecting area, which is called the static-current effective area of the wire antenna, is inversely proportional to the speed of air ions. On the other hand, the current is directly proportional to the speed of air ions. These two effects compensate each other to nullify the resultant effect on the current collected by the wire antenna. The idea of a universal effective area of the horizontal long-wire antenna is not valid in the presence of wind since it is a function of the ambient electric field. In this case, the wire antenna should be kept at a considerably high level to avoid the electrode layer near the earth. The horizontal wind speed is considered as constant. The solution can be numerically adapted for the logarithmic vertical wind profile.

  14. On possible connections between cosmic rays, global cloud cover and climate

    Jon Egill Kristjansson and Jørn Kristiansen

    Department of Geophysics, University of Oslo, Norway

    During the 20th century the earth's near-surface temperature rose by about 0.6 degrees, globally averaged. This warming is usually ascribed to a combination of increased concentrations of greenhouse gases in the atmosphere and an increase in solar output, with the former effect becoming dominant in the latter half of the century.

    Recently, Svensmark and Friis-Christensen (SFC) proposed an alternative hypothesis, whereby galactic cosmic rays would regulate global cloud cover and, in turn, global climate. Since the flux of cosmic rays decreases as solar activity increases, the enhanced solar activity over the last 150 years would, according to SFC, have led to a decrease in global cloud cover, and hence a warmer climate. SFC estimated the radiative forcing from this proposed effect to be in the range 0.8 - 1.7 W/m2, as compared to the 2.4 W/m2 or so forcing from the increase in greenhouse gas concentrations.

    We have investigated two aspects of this problem, namely:

    1. Do the large positive correlations between cloud cover and cosmic rays found by SFC hold up when longer time series are used?
    2. Assuming that there were a connection between cosmic rays and clouds, what would the radiative effect be?

    Using the ISCCP D2 dataset, we find that the positive correlations between global cloud cover and cosmic ray flux found by SFC for the period 1984-1990 do not apply to the years 1990-1994. When the cloud cover data are partitioned according to height, only low clouds correlate reasonably well with cosmic rays. This is somewhat surprising, since the ionization caused by cosmic rays drops significantly with decreasing height in the troposphere.

    Comparisons of the ISCCP cloud cover data and measurements of the earth's radiative budget by ERBE seem to suggest that the relationship between cloud cover, cloud radiative forcing is quite complex. For instance, between 1985 and 1989 global and low cloud cover decreased, yet the globally averaged cooling effect of clouds increased. This is contrary to what SFC assumed.

    We have estimated the potential radiative effect of cosmic rays through a coupling with low clouds. The radiative effect over the last 150 years is about 0.3 W/m2, i.e., significantly smaller than that suggested by SFC, but still large enough to be of interest, assuming it is real.

  15. The effect of Forbush decreases at South Pole

    M. M. Lam and A. S. Rodger

    British Antarctic Survey, Madingley Road, Cambridge, UK.

    Egorova et al. (2000) conclude that variations in cosmic rays affect the meteorology at Antarctic station Vostok (78.5S, 106.9E). They find that a Forbush decrease (FD) in galactic cosmic rays is followed by a statistically significant (1) degree of warming at heights below 6 km, (2) reduction in atmospheric pressure at altitudes below 20 km, and (3) rotation in the wind direction at about 7 km altitude.

    We conduct a similar study at South Pole (90.0 S 0E) in order to examine the spatial extent of this phenomenon. We use daily meteorological data from South Pole for the period 1965--1990, during the period of polar night (May--September), in order to exclude the influence of solar radiation. 33 winter FD events are identified using cosmic ray data from South Pole. The values of the isopycnal height, the temperature, wind direction and wind speed associated with FDs are distributed fairly evenly about the mean (calculated from all values), for pressures of 100, 200, 400 and 500 mbar, indicating that there is no perceptable effect of cosmic rays on the local weather at South Pole. We discuss the implications of these findings.

  16. Effects of geomagnetic storms and Forbush decreases of cosmic ray flux on total ozone at higher middle latitudes

    Jan Lastovicka

    Institute of Atmospheric Physics, Bocní II, 141 31 Prague 4, Czech Republic

    A brief review of effects of strong geomagnetic storms on total ozone content, targeted to effects observed near the latitudinal circle of 50oN, shows that at these latitudes geomagnetic-storm related changes in total ozone can at least partly be attributed to storm-related changes in atmospheric circulation. Significant effects of geomagnetic storms on total ozone have been observed only in winter and for strong storms, Ap > 40 or better 60, and only under very specific conditions - high solar activity and the east phase of QBO. This explains some contradictions in older results. The observed effects consist in redistribution of ozone, not in ozone production or loss. They are developed best in European sector and invisible in latitudinal average values.

    The Forbush decreases of cosmic ray flux occur prevailingly together with geomagnetic storms. The effects of Forbush decreases along latitudinal circles 40°N and 50°N are found to occur or to be absent under the same conditions as those of geomagnetic storms. Certain effect occurs only at 50°N (not 40°N), in winter, under conditions of high solar activity and the east phase of the QBO. However, the effects of the analyzed Forbush decreases are weaker than the effects of strong geomagnetic storms.

  17. Aerosol effects on terrestrial electromagnetic enviroment and their EHD description

    Eugene A. Mareev

    Institute of Applied Physics,Russian Academy of Science, 46 Ulyanov str., 603600 Nizhny Novgorod, Russia

    Modification of terrestrial electromagnetic environment due to dusty particles and particularly due to their collective interaction has been a topic of intensive research efforts recently. In the present paper we shortly review different ways of dust (aerosol) particle influence on the terrestrial electromagnetic environment and modern methods of their theoretical treatment. Special attention is paid to the basic ideas and applications of electrohydrodynamic (EHD) description of weakly conducting media with the presence of aerosols and highly charged hydrometeors.

    Electrical implications of active large-scale processes in the atmosphere (severe thunderstorms, dust and snow storms, earthquakes, volcanic eruptions) are of great importance. Recent experimental studies give evidence of particular importance of mesoscale convective systems in the global electric circuit. In this connection we consider the recent results of electric field measurements influenced by such processes, and give some basic physical ideas of their theoretical treatment. In particular, we study the inductive charging of aerosol particles in a weakly conducting medium and note its high efficiency for electric field structures formation. The very spectacular manifestations of permanent electrical activity in the atmosphere as connected to aerosol (hydrometeors) particle implication are related to thunderstorm activity. Some others are coupled to fair weather electricity as the inherent part of the global atmospheric electric circuit. Both them can be properly analyzed under EHD approach.

    During the past decade new results concerning local processes recognition and their influence on the electrical structure of the global electric circuit have been derived. ULF pulsations of electric field and electric current in the surface atmospheric layer were investigated under fair weather conditions. A new method of structural-temporal analysis has been firstly applied to the study of spatio-temporal structures of the electric field. This analysis allowed the quantitative estimations of spatial scales 0.5-1 km and life time not less than 10-20 min for respective elements, which have been called the "aeroelectric structures" (AES). Quasi-periodical sequences and high-amplitude solitary AES have been recognized. Spectra of short period electric field pulsations turned out to be influenced substantially by aerosol particles content.

    Recent studies emphasize an important role of internal gravity wave generation in the lower atmosphere for energy coupling with the upper atmosphere. We consider shortly the problem of gravity wave generation by irregular surface sources and their possible connection to electric processes in the surface atmospheric layer.

    This study is particularly a step to the development of a comprehensive technique for modeling the global, regional and local effects in the global electric circuit.

  18. Variations of atmospheric pressure during SPE and Forbush-decreases

    A. L. Morozova and M. I. Pudovkin

    Institute of Physics, St.Petersburg University, St.Petersburg, Petrodvorets 198504, Russia

    Variations of atmospheric pressure during Solar Proton Events (SPE) and Forbush-decreases of the Galactic Cosmic Rays (GCR) intensity for the 223 USSR meteorological stations are studied. The analysis of the experimental data has shown that character of the atmosphere parameters variations caused by the SPE or Forbush-decreases is quite different and depends on the station location and climatic zone.

  19. Variations of pressure altitudinal profiles at high-latitudinal stations

    A. L. Morozova(1), M. I. Pudovkin(1), and P. Thejll(2)

    1. Institute of Physics, St.Petersburg University, St.Petersburg, Petrodvorets 198504, Russia
    2. Solar-Terrestrial Physics Division, Danish Meteorological Institute and Danish Climate Centre

    Variations of altitudinal profiles of atmospheric pressure during Solar Proton Events and Forbush-decreases of the Galactic Cosmic Rays intensity for high-latitudinal (Greenland, Denmark, Iceland, Faeroes, and Jan Mayen) meteorological stations are studied. An analysis of the experimental data has shown significant variations of the troposphere pressure caused by the SPE or Forbush-decreases.

  20. Results from the first European Sprite Observation Campaign

    T. Neubert(1), T.H. Allin(1), H. Stenbaek-Nielsen(2), E. Blanc(3), M. Fuellekrug(4), and G. Satori(5)

    1. Solar-Terrestrial Physics Division, Danish Meteorological Institute
    2. Geophysical Institute, University of Alaska, Fairbanks
    3. Commissariat a l'Energie Atomique ,Laboratoire de Detection et de Geophysique, France
    4. Inst. f. Met. & Geophys, Universitaet Frankfurt/Main, Germany
    5. Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences, Sopron, Hungary

    Results are presented from the first coordinated European campaign for observations of sprites, conducted during the summer of 2000. Optical observations were taken by a low-light-level video camera from the French astronomical observatory, Observatoire Midi-Pyrenees (OMP) located in the Pyrenees close to the border of Spain, and EM observations were taken from several locations in Europe and around the world. The primary objective was to establish if sprites are generated over Europe and to establish the thunderstorm characteristics needed for sprite generation. During the one month campaign, sprites were observed two nights over the Alps and one night over south-eastern France in connection with cold fronts moving in from the Atlantic. Local weather conditions allowed observations approximately half of the nights. Over the Alp region, one night gave 16 sprites, with 1 sprite per 7 min on the average, and the other 12 sprites with 1 per 3 min. For the south-eastern France area, the numbers are 12 sprites and 1 per 5 min. The weather conditions were almost identical during the 3 nights, with the active area forming on the front-side of the cold front. The storms cannot be classified as Mesoscale Convective Systems, and are not of the same magnitude as active systems observed over the US. Even so, sprites seem to be a common occurrence also over Europe. Data from the campaign are presented and related to the meteorological conditions and to the electric properties of the storms as detected by the French lightning detection network.

  21. Schumann resonance as an indicator of upper tropospheric water vapor

    Colin Price

    Department of Geophysics & Planetary Sciences, Tel Aviv University, Israel

    Upper tropospheric water vapor (UTWV) is a key parameter in the global warming debate. If UTWV increases as the climate warms this will result in a positive feedback, enhancing the warming. If however, UTWV concentrations decrease as the climate warms, this will result in a negative feedback thereby reducing the intial warming. Due to very small quantities of UTWV, it is very difficult to monitor long term trends of this parameter. However, since UTWV is transported from the boundary layer to the upper troposphere via deep convective storms, the variability of UTWV may be closely linked to thunderstorm activity around the globe. Using 10 Hz extremely low frequency (ELF) data from Antarctica, it is shown that the globally integrated UTWV is closely linked to the daily and monthly variability of global lightning.

  22. Observations of ELF sprites from Israel

    Colin Price

    Department of Geophysics & Planetary Sciences, Tel Aviv University, Israel

    Over the last two summers (1999 and 2000) we have been involved in extremely low frequency (ELF) measurements in Israel in support of various field campaigns taking place in the United States (SPRITES '99 and STEPS 2000). We have been very successful in locating the ELF transients produced by sprites more than 11,000 km away from our station. We have used both GPS timing and location finding methods to verify our results. During November 1999 we also observed ELF transients associated with sprites and elves over Yugoslavia, observed by a NASA research plane. Finally, in the coming year we will participate in a Space Shuttle experiment to observe sprites, and perhaps blue jets, from space. During this flight the first Israeli astronaut will attempt to image sprites, elves and jets from space while a ground network of ELF sensors will locate and characterise the parent lightnings.

  23. Ground-atmosphere-ionosphere-magnetosphere coupling conception

    S. A. Pulinets, K. A. Boyarchuk, V. V. Hegai, and D. R. Shklyar

    IZMIRAN, Troitsk, Moscow Region, 142092, Russia, E-mail: pulse@izmiran.rssi.ru

    During last 10 years the model of atmosphere-ionosphere coupling based on the quasi- electrostatic vertical atmosphere electric field penetration into the ionosphere was developed at IZMIRAN. The model consist of three parts: 1-electric field generation model, 2-electric field penetration at thermosphere-ionosphere heights, and 3-effects of electric field in the thermosphere- ionosphere. In the first part a model of ion kinetics in a near-ground layer of troposphere is considered. It explains the appearance of strong vertical electric field up to several kV/m near the ground surface. Second part with the help of existing model of atmosphere conductivity vertical distribution makes calculations of penetrated electric field at the heights from 90 up to 1000 km. It explains the transverse to geomagnetic field lines electric field ~1 mV/m at the ionospheric heights as a result of original vertical electric field ~1 kV/m at the ground surface. The third part demonstrates the effects of electron concentration modification over the vertical electric field source. Self-consistence of the model is substantiated by correspondence of the calculated parameters to the measured experimentally. Recently the model was supplemented by effects in magnetosphere (ion composition changes, VLF noises amplification), as well as by near-ground calculations (underwater effects, near-ground generation of ELF-VLF emissions). In present state the complete set of works could be regarded as complete conception of Ground- Atmosphere-Ionosphere-Magnetosphere Coupling based on the quasi-electrostatic vertical electric field effect.

  24. Some suggested objectives for the SPECIAL meeting in Lindau, 8 to 11 November 2000

    Michael J. Rycroft

    As the first phase of the ESF-funded Space Processes and Electrical Changes In Atmospheric Layers Scientific Network draws to a close, the SPECIAL community needs to decide upon its actions for the next phase. It is suggested that:

    1. each of the three constituent groups should prepare a plan for its activities from May 2001 to April 2003,  
    2. these plans should be brought together by the Coordination Committee,
    3. a costed proposal for a two-year extension (from mid-2001) of the life of the Network should be submitted to the ESF, by the deadline of 30 November 2000,  
    4. a week-long European Research Conference (with about 100 attendees) on SPECIAL could be organised, perhaps in conjunction with other bodies / programmes, in 2003,  
    5. the optimal timing for making a proposal for a coherent and fully-fledged ESF Scientific Programme, with individual European nations choosing whether or not to support it financially, should be considered carefully.    

    Let us agree our objectives clearly at the outset, and ensure that we go forward with determination!

  25. Solar and geomagnetic data and data sources for SPECIAL investigations

    Kristian Schlegel

    Max-Planck Institut für Aeronomy, Katlenburg-Lindau, Germany

    Solar and geomagnetic data are vital for studies in the framework of SPECIAL. Important parameters like solar wind speed and density, interplanetary magnetic field, high energy solar proton and electron fluxes, x-ray fluxes and various geomagnetic indices and their possible influence on atmospheric layers are briefly reviewed. Several sources of these data in the internet will be listed and their access described. The sources include lists of major geomagnetic storms and solar flares which facilitate the selection of appropriate events to be studied with SPECIAL.

  26. Solar activity and lightning

    Kristian Schlegel

    Max-Planck Institut für Aeronomy, Katlenburg-Lindau, Germany

    The influence of solar activity on lightning is a controversial subject. Apart from one clear correlation published 1974 in NATURE there is not much significant evidence. A lightning registration system in Germany run by SIEMENS provides in principle very useful data for such studies. Unfortunately it covers so far only 8 years, i.e. less than one solar cycle. Correlation of solar and geophysical parameters with the number of lightning strokes and their strength have been performed. The results show some interesting results, but they are again not fully conclusive because of the limited time span.

  27. Atmospheric ionisation by cosmic rays and Earth's cloud cover.

    Henrik Svensmark

    Danish Space Research Institute

    Satellite data have revealed a striking correlation between the intensity of galactic cosmic rays (GCR) and low liquid clouds (<3 km). GCR is responsible for nearly all ionisation in the atmosphere below 35 km. However, a direct link between GCR and cloud formation is yet to be unambiguously established and, moreover, the microphysical mechanism is not understood. One mechanism could involve aerosol particles (0.001-1 mu in diameter) and the formation of cloud condensation nuclei (CCN). New numerical results suggest that ion-mediated nucleation of ultra-fine aerosols is the dominating mechanism in the marine boundary layer where low clouds form. A systematic variation in the properties of CCN will affect the cloud droplet distribution  and thereby influence the radiative properties of clouds. An international collaboration called CLOUD has been formed. The intend is to test the cosmic ray cloud link under controlled laboratory conditions in a particle beam at CERN with a cloud chamber.

  28. Variation of fair weather atmospheric electricity at Marsta Observatory, Sweden, 1993-1998

    H. Tammet and S. Israelsson

    (Extended abstract available as PDF only.)

  29. Electroscavenging and the production of ice in cold clouds and of large condensation nuclei in warm clouds

    Brian A. Tinsley

    University of Texas at Dallas

    The formation of clouds produces conductivity gradients in the atmosphere that lie in the path of the ionosphere-earth current density. The conductivity gradients cause layers of space charge density to form, and at cloud tops these deposit hundreds of elementary charges on droplets which are likely to be evaporating. The residual aerosol particles (temporarily) retain the charge as well as coatings of sulphates and organics previously absorbed by the cloud droplets. Numerical models of scavenging of aerosol particles (including these evaporation nuclei) by other cloud droplets show that with only tens of elementary charges on the aerosol particles the electrical forces control the scavenging rates. This process can affect cloud chemistry, condensation nuclei size distributions, and the production of ice. We show that for low level maritime type clouds with their broad droplet size distributions, and cloud temperatures below freezing by about 10°, electroscavenging leads to production rates of ice by contact ice nucleation that exceed those from deposition nucleation. This can affect precipitation rates, latent heat transfer, and winter storm dynamics. For clouds above freezing electroscavenging and repeated cycles of evaporation and condensation can increase the size of condensation nuclei. This can affect droplet size distributions, drizzle production, and cloud cover. The rates depend on the aerosol particle charge, and thus can respond to solar wind/cosmic ray modulation of the global atmospheric electric circuit.

  30. Lightning-induced quasi electrostatic fields above equatorial thunderstorms

    P. T. Tonev

    Central Solar-Terrestrial Influences Laboratory, Bulgarian Academy of Sciences

    The spatial-temporal behaviour of the quasi electrostatic fields (QESF) in milisecond time scale, which follow a lightning discharge and comprise the stratosphere, mesosphere and lower ionosphere above thunderstorms, is theoretically studied. These fields, together with the electromagnetic fields acting in a shorter timescale, are presumably one of the sources of a class of optical phenomena above lightning storms, particularly of red sprites. Therefore the investigation of QESF is useful in order to explain better the mechanisms (runaway electrons, heating) and conditions for realization of such phenomena, as well as of their temporal and spatial distributions. The electrostatic fields are highly sensitive to the atmospheric conductivity and to its anisotropic nature above 70 km. The feature of anisotropy is taken into account in some of the models of QESF, as vertical orientation of the geomagnetic field is assumed in most of them (case of high latitudes). Here we treat the opposite case of the horizontal geomagnetic field lines, which corresponds to equatorial latitudes. An analytical model is proposed based on the reduced (electrostatic) form of the Maxwell equations. Solutions are obtained in an explicite form after accepting a specific presentation of the electric conductivity. Results from this model compared to these for the case of high latitudes show that significant redistribution of QESF takes place, even below the anisotropic region. This is due to the differences in the initial distributions of the free electric charges and the temporal behaviour of the electrostatic fields in both cases. Some features of QESF distributions are demonstrated such as loss of the axial symmetry, as well as of the zonal symmetry (due to the influence of Hall conductivity). The model proposed is the first stage in a theoretical study in which one problem is whether red sprites are sensitive to latitude.

  31. Influence of the gravitational field variations on processes in animate and inanimate nature

    O. A. Troshichev(1), E. S. Gorshkov(1,2), S. N. Shapovalov(1), and V. V. Sokolovsky(1,3)

    1. Arctic and Antarctic Research Institute, St.Petersburg
    2. St.Petersburg Branch of IZMIRAN, St.Petersburg
    3. Institute for Analytical Instrumentation, St.Petersburg

    The biochemical studies carried out at the Russian Antarctic base Mirny in 1996-1997 evidenced that rate of oxidation reaction of the unithiol undergoes rhythmical fluctuations (acceleration and deceleration) correlating with changes in velocity of the forward-rotational movement of the Earth. The similar experiments fulfilled in course of the Antarctic voyage of vessel "Fedorov" showed that fluctuations of the redox rate took place also in the bulk of the ship, in room shielded by numerous steel bulkheads and deck ceilings. The remarkable agreement of the oxidation rate fluctuations with the periodicity of planetary processes determined by gravitational fields of the Sun and Moon made it possible to conclude that rate of the redox reactions in the Earth's biosphere is greatly influenced by change in the space gravitational field [Biophysics, v.//, n 4, 2000]. The conclusion is confirmed while comparing variations of the redox rate (unithiol test) with direct measurements of the gravitational field performed by the precision gravimeter. These comparisons fulfilled under the observatory conditions (Voieikovo, near St.Petersburg) in period from August 1999 to March 2000, included events of solar and lunar eclipses. Simultaneous testing of "sensor for hyper weak fields" (Bondarenko sensor) has been conducted at the same place, and excellent correspondence between the gravitational field variations recorded by the gravimeter, and the readings of the Bondarenko sensor has been found. Basing on this correspondence the Bondarenko sensor has been used as mobile indicator for the gravitational field variations aboard vessel "Fedorov" in course of the vessel's trip to Antarctic in March-June 2000, the precision gravimeter being operated in Voieikovo at the same time. The following results have been obtained:

    • changes in rate of redox reaction (unithiol test) are in a good agreement with the readings of "sensor for hyper weak fields";
    • short-term (some days) regular oscillations of the ozone total content correlate with variations of the gravitational field;
    • periodicity is observed in statistics of number of ß decay of 239Pu, the periods being coincident with the nutational periods of Earth's axis;
    • structure of the gravitational variations depends on latitude.

    These experimental facts are indicative of essential influence of the gravitational field variations on processes in animate and inanimate nature.

  32. Disturbances in the wind system above the antarctic caused by variations of cosmic rays and their relationship to the southern atmospheric oscillations

    O. A. Troshichev, V. Ya. Vovk, and L. V. Egorova

    Arctic and Antarctic Research Institute, St.Petersburg, Russia

    A long-standing data of wind observations at Russian Antarctic stations Vostok, Leningradskaya, Russkaya, Mirny, Molodyzhnaya have been analyzed with regard to variations of cosmic rays. It is shown that Forbush decrease of galactic cosmic rays strongly affecting the atmospheric temperature and pressure in the near-pole region gives rise to reconstruction of the field of winds above Antarctica. Reconstruction of the wind system in the near-pole region starts at all altitudes (h=0-20 km) simultaneously with the beginning of Forbush decrease. Maximum of changes in the wind system is observed by forth day when wind rotates from W (250±22°) to S (180°) and reaches the maximum of strength. This day coincides statistically with date of the Forbush decrease minimum. The usual East wind typical of the coast stations Russkaya (137°W) and Leningradskaya (159°E) is changed at this time by very intense South wind. On the other hand, it turns out that occurrence of South winds at stations Russkaya and Leningradskaya in April-September of the El Niño years is twice as higher as in the preceding and succeeding years. It is suggested that the relationship between the Forbush decrease occurrence and atmospheric oscillations in the southern ocean area (SOI) takes place.

  33. Variations in temperature and atmospheric pressure in the southern near-pole region: Effects of the galactic cosmic rays, solar protons and interplanetary shocks

    O. A. Troshichev, L. V. Egorova, and V. Ya. Vovk

    Arctic and Antarctic Research Institute, St.Petersburg, Russia

    Daily data of pressure, temperature and wind observations at Antarctic station Vostok in 1981-1991 have been analyzed with regard to the cosmic-rays variations and interplanetary shocks in their passage through the Earth's orbit. Vostok station located at the ice dome in the center of the Antarctic continent is the best-suited place for such an analysis. Indeed, Vostok station is at distance of 1500 km from ocean coast, and the influence of cyclonic activity relatively seldom captures this area. The ice dome is a flat homogeneous plain at height 3.5 km, which is not subjected to local atmospheric vortices. Since Vostok station is close to the geographical pole, the influence of direct solar radiation can be excluded from consideration if periods of polar night (May-September) are examined. As a result of case studies and statistical treatment the following results have been obtained.

    The temperature changes observed in the lower atmosphere of the Southern near-pole region in the course of ordinary Forbush decrease is superposition of effects produced by the interplanetary shock, solar proton event, and Forbush decrease itself. Passage of the interplanetary shocks (sharp increase of density and velocity of the solar wind) related to Forbush decreases (or SP events) on the Earth's orbit gives rise to strong temperature changes in the lower atmosphere (warming at altitudes h<5 km and cooling at h>8 km). This effect reaches maximum within one day and is damped equally quickly. Statistically the passage of interplanetary shocks coincides with the beginning of Forbush decrease. That is way a dramatic temperature effects in the lower atmosphere (warming up to 10° at the ground level) is observed just at the beginning of Forbush decrease. The interplanetary shocks are one day ahead of occurrence of SP fluxes on the Earth's orbit, and the temperature effect produced by the interplanetary shock usually precedes the solar proton events. Forbush decrease itself influences the cooling of lower troposphere and, possibly, warming of the atmosphere at altitudes higher 15 km, the temperature changes being gradual and developed slowly over Forbush decrease. Spikes of solar protons likely produce only insignificant warming of atmosphere at h<5 km during SPE.

    Forbush decrease is accompanied by reduction of atmospheric pressure at all altitudes below 20 km, the magnitude of reduction being maximal at higher altitudes. The solar cosmic rays cause within 0-2 days the increase of atmospheric pressure predominantly at altitudes of 10-15 km, the effect is much more prominent for high-energy protons EP>100 MeV. Influence of the interplanetary shocks on atmospheric pressure is not found.

    Variations of temperature and atmospheric pressure influenced by galactic cosmic rays and solar protons in the Southern near-pole region are principally distinct from those observed between latitudes 50° and 80° in the Northern hemisphere, and other mechanisms are required for their explanation.

  34. Neural network based approach to forecast ionospheric parameters

    Yurdanur Tulunay(1), Ersin Tulunay(2) and Erdem Turker Senalp(2)

    1. Faculty of Aeronautics and Astronautics, Istanbul Technical University, Istanbul, Turkey
    2. Department of Electrical and Electronics Engineering, Middle East Technical University, Ankara, Turkey

    Within each group of the SPECIAL Network objectives, some modeling work is foreseen. It is known that almost all of the processes within the interest of the SPECIAL Network are highly non-linear and also time-varying. In such cases it has been demonstrated by the authors and others that the data driven modeling approach such as neural network (NN) based modeling is very promising [E Tulunay et al, 2000; Y Tulunay et al, 2000a, Y Tulunay et al, 2000b, Kumluca et al, 1999]. For example, by using ionospheric critical frequencies during IMF Bz Southward polarity changes Y Tulunay et al [2000a] demonstrated that forecasting and filling the data gaps are possible by using NN based models.

    It is proposed for the SPECIAL Network that NN based models that are data driven can be adopted for the modeling of physical phenomena under the direct interest of the task. The only basic requirement for this is the availability of representable data for the phenomena.

  35. Effects of precipitating high energy particles in the mesosphere: Present and future applications of the Sodankylä Ion Chemistry Model

    Esa Turunen(1), Thomas Ulich(1,2), Pekka Verronen(3), and Erkki Kyrölä(3)

    1. Sodankylä Geophysical Observatory, Sodankylä, Finland
    2. Space Physics Group, University of Oulu, Oulu, Finland
    3. Finnish Meteorological Institute, Helsinki, Finland

    Roughly 10 years ago a detailed ion chemical scheme, with 55 ions, was formulated and coded as the Sodankylä Ion Chemistry model (SIC) for studies of the lower ionosphere. A major revision of the SIC model was made during the last two years in a collaborative effort of the Sodankylä Geophysical Observatory and the Finnish Meteorological Institute. This revision included adding effects of photodissociation of neutrals, relevant neutral chemistry of nitric oxides, ozone and other related constituents. Furthermore, selected neutral constituents are now explicitly modelled. Our aim is to use the model, together with future and existing satellite and ground-based data (e.g. ENVISAT-1), in order to quantify the effect of precipitating high energy particles on the neutral atmospheric composition. In this paper examples of present and possibilities of future applications of the SIC model are described.

  36. The potential for monitoring the global circuit from ocean straits

    Robert Tyler

    Applied Physics Laboratory, Ocean Physics Department, University of Washington

    Under the historical paradigm of the global circuit (GC), electric charge is removed from the Earth's surface, primarily in low-latitude thunderstorm regions, spreads rather uniformly over the conductive ionosphere, and returns to the Earth's surface as a downward atmospheric electric current with an associated "fairweather" electric field. To close the circuit there must be return currents in the solid earth and oceans that flow from the fairweather regions back to the thunderstorm source regions. It is expected from simple theoretical and numerical results which we will present that these return currents are highly concentrated in the oceans, particularly in certain straits where the electric current density can be six orders of magnitude greater in amplitude than that in the lower atmosphere. From these arguments and others we suggest that these oceanic locations may be the best place to set up stations to monitor the GC. Long-duration, low-noise observations from such monitoring stations are needed to resolve long-standing fundamental questions about the GC processes and to address current studies regarding the role of the GC in the Earth's weather and climate system.

    An initial analysis of observations taken for oceanographic purposes in the Strait of Gibaltar and the Denmark Strait show large unexplained electric currents flowing through these straits. Such effects are not seen in similar open-ocean surveys. The steady component of these electric currents indicate electric currents exiting the straits in a manner consistent with the assumption that these are return currents of the GC. The magnitude also shows agreement with results from simple numerical modeling of the GC return currents. This encourages potential use of ocean GC observatories. However, at least the Denmark Strait data also show large variability with electric currents in the strait sometimes flowing in the opposite direction of that of the mean. This suggests that electric currents due to other sources may also be present in these straits potentially raising the challenge of separating the GC components.

  37. Ground-based monitoring of space weather in Finland and Northern Scandinavia

    Thomas Ulich(1,2)

    1. Space Physics Group, Dept. of Physical Sciences, FIN-90014 University of Oulu, Finland
    2. Sodankylä Geophysical Observatory, FIN-99600 Sodankylä, Finland

    The Sodankylä Geophysical Observatory (SGO) is one of the most versatile observatories in the world. The first measurements at Sodankylä took place already during the 1st International Polar Year between 1882 and 1884. Today SGO looks back on a long tradition of ground-based geophysical routine observations, which started in 1914 with the monitoring of the geomagnetic field. In the more recent past, instrument development and research based on the available data have become an essential part of SGO's activities. All activities are tightly linked to those of the Space Physics Group (SPG) at the University of Oulu.

    Since 1968, pulsation magnetometers are in use in Finland. Today, the chain of stations comprises 6 instruments between 60°N and 69°N, as well as one station on Crete, Greece. The instruments are capable of recording ULF waves in the whole Pc/Pi frequency range. SGO has constructed sophisticated VLF receivers, which are operated during campaigns. Fast algorithms for computing polarisation parameters were developed in order to study the link between whistler activity and auroral substorms as well as powerline harmonic radiation. Currently a new instrument measuring the vertical electric field is in test use near Oulu. Preliminary results show that it is able to register at least the lowest three Schumann frequencies. During the IGY in August 1957, the Sodankylä ionosonde started regular half-hourly soundings of the high-latitude ionosphere. The ionograms, which have entirely been scaled by the same person throughout, are used for studies of long-term changes of the ionosphere. Since the mid-1960s, SGO has carried out continuous measurements of cosmic radio noise by riometers in Finland and Northern Scandinavia. Today the network of 9 riometers covers L-values from 3.7 to 13.2 between 62°N and 77°N, and includes the 49-beam imaging riometer IRIS of the University of Lancaster, UK. In the 1980s, SGO became one of the sites of EISCAT, which operates powerful incoherent scatter radars and a heating facility. These observations are complemented every winter by optical observations with all-sky cameras and photometers.

    All of the most important research and development activities at SGO are based on the same fundament: mathematical modelling of measurements and stochastic inversion theory. Exploiting these methods lead to completely new, revolutionary radar measurements, which gradually are being employed by a number of international radar facilities. Scientists of SGO and SPG are leading in the world concerning radar measurements as well as tomographic applications. Currently, a permanent chain of receivers for satellite tomography of the ionosphere is under development. Furthermore, a meteor radar is under construction and will be operational in 2001.

    In the present work, some examples of available data and recent results are presented briefly. SGO welcomes the scientists of SPECIAL to work with these data. Additional information is available on-line at www.sgo.fi.

  38. How accurately do we know the lengths of the sunspot cycles?

    Thomas Ulich(1,2)

    1. Space Physics Group, Dept. of Physical Sciences, FIN-90014 University of Oulu, Finland
    2. Sodankylä Geophysical Observatory, FIN-99600 Sodankylä, Finland

    The sunspot numbers have traditionally been used as a measure for the solar activity. Solar activity, in turn, has been related to the long-term evolution of global temperature and other climate parameters. Esp. the time series of the durations of the Schwabe Cycles correlates well with northern hemispheric air temperatures. The key question is whether this connection dominates over the anthropogenic effects on climate.

    In this work I re-analyse the sunspot cycle lengths using traditional methods and a novel technique based on determining the time ('median time') of half of the integrated sunspot number per cycle. While traditional methods are sensitive to the different estimations of sunspot minima or maxima, the median method is very stable to these differences. Furthermore, possible gaps in the time series of sunspot counts can safely be interpolated with only little effect on the median cycle length.

  39. Large scale campaign for simultaneous measurements of ionospheric conductivity profiles by ELF receivers, incoherent scatter radars, and riometers in Northern Fenno-Scandia

    Thomas Ulich(1,3), Martin Füllekrug(2), Jyrki Manninen(3)

    1. Space Physics Group, Dept. of Physical Sciences, University of Oulu, Finland
    2. Institute of Meteorology and Geophysics, University of Frankfurt, Germany
    3. Sodankylä Geophysical Observatory, Sodankylä, Finland

    Electromagnetic radiation of lighting is partially reflected in the ionosphere. The conductivity of the ionosphere greatly depends on various extra-terrestrial factors, which are commonly summarised as "space weather". The variations of the conductivity lead to temporally variable attenuation of the waves emitted by lightning as well as to changes of their propagation velocities. These can be measured by high-precision ELF receivers and with the aid of numerical models, conductivity profiles can be derived for the ionospheric D region (60-85 km). In order to verify and improve the analytical methods involved, the proposed campaign aims at a simoultaneous measurement of lower ionospheric conductivities with the aid of the EISCAT incoherent scatter radars in Norway, Sweden, and Finland. The results will be compared with measurements of cosmic radio noise absorption by the Finnish Riometer Chain. Furthermore, we will model D-region conductivity by the detailed Sodankylä Ion Chemistry Model (SIC). First tests are planned in conjunction with the Finnish EISCAT Campaign in February 2001. The actual campaign will take place in October 2001.

  40. Solar and tropospheric variability effects on Schumann resonances

    B. Zieger(1,2), and G. Satori(2)

    1. Danish Space Research Institute, Copenhagen, Denmark
    2. Geodetic and Geophysical Research Institute, Sopron, Hungary

    Schumann resonances (SR) are extremely low frequency (ELF) electromagnetic waves produced by lightning discharges and trapped in the Earth-ionosphere waveguide. The SR parameters observed at a single station are controlled by the global lightning activity, which in turn, is related to different climate variables such as surface air temperature, vertical air convection, upper tropospheric water vapour concentration, etc. SR frequencies and amplitudes have been recorded continuously for the vertical electric component at the Nagycenk Observatory, Hungary since May 1993.In the present study, we identify periodicities in Schumann resonance amplitudes and frequencies in the period range from 2 days to one year and discuss their possible origin. The observed intensity and frequency of Schumann resonances depend not only on the source intensity and the source-observer distance but also on the physical parameters of the Earth-ionosphere waveguide. Dynamic spectra of daily SR amplitudes and frequencies were computed for the first three modes and were compared with dynamic spectra of solar wind speed and geomagnetic activity and energetic particle flux. Several periodicities were identified including 109, 74,39,27,20,13.5,10 and 5 days. The most significant correlation between SR parameters and energetic electron flux (or solar wind speed) was found at the periods of 27 and 13.5 days (harmonics of the solar rotation period). This implies a solar influence on the upper boundary of the Earth-ionosphere waveguide, i.e. the ionospheric D region, most probably through energetic particles (MeV protons and electrons).

Last update: 2000-11-03, 1353 UT, by Th.Ulich, editor [e-mail | homepage].