SPECIAL Workshop 2002

Abstracts (see programme)

All abstracts are ordered alphabetically according to the first author.

  1. Arnold, N., Space Plasma Influences on Climate
  2. Bochnicek, J. and J. Lastovicka, Impact of geomagnetic storms on the lower atmosphere at middle latitudes
  3. Füllekrug, M., Remote sensing and characterization of oceanic/african lightning and sprites in their meteorological and lower ionospheric conductivity environment
  4. Inan, U. S., Lightning-driven electrodynamic effects in near-Earth space
  5. Kartalev, M. and V. Papitashvili, A new approach in studying effects of ionospheric currents in the global electric circuit
  6. Kudela, K., On relations of cosmic rays to space weather
  7. Makarova, L. N. and A. V. Shirochkov, Impact of the solar wind variations on the processes in the middle latitude lower atmosphere
  8. Mareev, E. A. and S. V. Anisimov, Monitoring of global, regional and local perturbations of the atmospheric electric circuit as displayed in short-period pulsations and coherent structures of atmospheric electric field.
  9. Mareev, E. A., V. Yu. Trakhtengerts, D. I. Iudin, A. E. Sorokin, E. I. Smirnova, S. S. Davydenko, and N. A. Bogatov, Modeling of electrical structure of thunderclouds and mesoscale convective systems as connected to initiation of intra-cloud, cloud-to-ground and high-altitude discharge phenomena.
  10. Parrot, M., The micro-satellite DEMETER
  11. Price, C., M. Asfur, W. Lyons, and Th. Nelson, Geolocating sprites using an improved ELF/VLF method
  12. Price, C. and M. Asfur, Lightning and climate: the water vapor connection
  13. Kim, V. P., S. A. Pulinets, and V. V. Hegai, The model of enhanced ionization layers in midlatitude nighttime D-region of ionosphere in the presence of anomalous electric fields.
  14. Sátori, G., B. Zieger, and J. Bór, Areal variation of the worldwide thunderstorm activity as shown by Schumann resonances
  15. Shirochkov, A. V., L. N. Makarova, and V. A. Ul'ev, A model evaluation of the ozone density changes caused by various types of corpuscular radiation
  16. Todd, M. C. and D. R. Kniveton, Changes in cloud cover associated with Forbush decreases of galactic cosmic rays
  17. Troshichev, O. A., L. V. Egorova, and V. Ya. Vovk, Influence of the solar wind variations on temperature in the southern polar cap troposphere
  18. Tulunay, Y., E. Tulunay, and E. T. Senalp, The trough based neural network model of the foF2 values
  19. Y. Yair, C. Price, Z. Levin, A. Devir, B. Ziv, and M. Moalem, MEIDEX: An opportunity for coordinated global measurements of TLE from the space shuttle and ground stations

  1. Space Plasma Influences on Climate

    Neil Arnold

    Observations of the interaction between the Sun's and the Earth's atmospheres have been available from the earliest times from aurora. What has been less well understood is how space plasma may also influence the climate system at lower altitudes. We present some of the latest numerical model results that indicate significant non-linear coupling between the middle and upper atmospheres in the winter due to the transport of heat and momentum. In collaboration with a number of groups in the UK and the Danish Meteorological Institute we are developing a micro-satellite mission to investigate these processes in more detail.

  2. Impact of geomagnetic storms on the lower atmosphere at middle latitudes

    Josef Bochnicek(1) and Jan Lastovicka(2)

    1. Geophysical Institute, Bocni II, 14131 Prague, Czech Republic
    2. Institute of Atmospheric Physics, Bocni II, 14131 Prague, Czech Republic

    We propose a new project of the above title. Its objective is to clarify better the observational pattern of geomagnetic storms/activity effects on the lower atmosphere (troposphere and lowermost stratosphere) at the extratropical Northern Hemisphere, to make observational constraints to various suggested mechanisms, and to construct 'scenarios' (or mechanisms). We particularly expect to broaden the results to include not only temperatures and pressure, but also wind fields and maybe other parameters. The role of galactic cosmic rays in geomagnetic storm effects will be further tested observationally. The project is based on analysis of existing and future meteorological (temperature, pressure, wind fields northward of 20N) and ozonesounding (ozone profiles) data from international network. Particularly winter periods will be studied based on case studies and their statistics. We hope this effort allows construct observational constraints to test various suggested mechanisms, as e.g. cloudness variability, electrofreezing and electroscavenging, role of planetary waves, role of ozone changes. The project belongs to Group 1 by 10% and Group 2 by 90%. Participation of other scientists from Group 2 is welcome.

  3. Remote sensing and characterization of oceanic/african lightning and sprites in their meteorological and lower ionospheric conductivity environment

    Martin Füllekrug

    Institut für Geophysik, Feldbergstr.47, D-60323 Frankfurt/Main, Germany

    Extremely low-frequency magnetic field disturbances from intense positive lightning discharges are compared to the convective cloud cover in central Africa, derived from infrared brightness temperatures recorded on board the geostationary satellite Meteosat during April 1998. The mean diurnal variation of the lightning charge moment is well correlated with the mean diurnal variation of the cloud cover at 11.5 km height and constrains the mean lightning channel length. The daily integrated positive cloud to ground charge transfer exhibits a pronounced day to day variability which is well correlated with the cloud cover at 15.5 km height, related to the charging of the thundercloud 4 hours prior to the maximum cloud to ground charge transfer. The cloud cover area is used to calculate an effective cloud volume which is related to the cloud to ground charge transfer via the charge density. This charge density is used to estimate promising locations for optical sprite observations in the central Congo basin and Cameroon with 69 sprite occurrences during an average night.

    The electrodynamic properties of intense oceanic lightning discharges are compared to intense continental lightning discharges. Particularly intense negative lightning discharges with absolute charge moments >2 kC km occur more often over the oceans than over the continents during April 1998. Intense continental lightning discharges with negative and positive polarity and intense positive oceanic lightning discharges mainly occur in the late evening associated with mesoscale convection. The number of intense negative oceanic lightning discharges increases in the early morning hours, probably associated with the resurgence of mesoscale oceanic convection in coastal areas. The day to day variability of intense negative oceanic lightning discharges exhibits a five day periodicity, possibly related to planetary waves. These results strongly suggest that intense negative oceanic lightning discharges may produce mesospheric breakdown and oceanic sprites.

    The wave propagation speed of seven spherical electromagnetic resonance frequencies in the atmosphere is experimentally determined from twelve years monitoring of natural magnetic field variations in the frequency range 5-50 Hz at Arrival Heights, Antarctica. The derived magnetic field spectra are classified with respect to solar short wave radiation variability determined from the sun's radio flux at 2.8 GHz near Ottawa, Canada. The wave propagation speed exhibits a deviation of 1 % associated with quiet and disturbed solar conditions. This modulation of the wave propagation constant can be explained with a 2.5 km height variability of a global average two scale height ionospheric conductivity profile.


    Umran S. Inan

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

    A fascinating menagerie of complex phenomena have been uncovered during the past decade that collectively indicate that tropospheric thunderstorms and lightning discharges are strongly coupled (electrodynamically) to the overlying upper atmospheric regions, ranging from the mesosphere to the lower ionosphere and extending to the radiation belts. Lightning discharges occurring at cloud altitudes (<20 km) affect the upper atmosphere at altitudes >40 km either via the release of intense electromagnetic pulses (EMPs) and/or the production of intense quasi-static electric (QE) fields at mesospheric altitudes. An average lightning discharge radiates an EMP of ~20 GW peak power, which propagates though the ionosphere and couples into the radiation belts, heating and ionizing the former and precipitating trapped energetic electrons from the latter. In addition, lightning discharges often produce intense transient QE fields of up to ~1 kV/m at 40-80 km altitudes, which for positive cloud-to-ground (CG) discharges is directed downwards, and which can thus avalanche accelerate upward-driven runaway MeV electron beams, producing brief (~1 ms) flashes of gamma radiation, both in the hemisphere of the parent lightning and in the conjugate hemisphere, and possibly contributing to the population of trapped radiation belt particles. A spectacular manifestation of these intense fields is the so-called 'Sprites', large luminous discharges which appear in the altitude range of ~40 km to 90 km. Sprites are produced by the heating of ambient electrons in the mesosphere and lower ionosphere by the intense QE fields which temporarily (for a few to tens of milliseconds) exist at high altitudes following intense lightning flashes. The so-called 'Elves' are optical flashes which last much shorter (<1 ms) than sprites, and are typically limited to 80-95 km altitude, being produced by the heating, ionization, and optical emissions due to the EMPs radiated by both positive and negative lightning discharges. A brief background and a discussion of recent results will be provided.

  5. A new approach in studying effects of ionospheric currents in the global electric circuit

    Monio Kartalev(1) and Vladimir Papitashvili(2)

    1. Institute of Mechanics, Bulgarian Academy of Sciences, Sofia, Bulgaria
    2. Space Physics Research Laboratory, University of Michigan, Ann Arbor, MI, U.S.A.

    A new numerical model of global ionospheric electrostatic potentials (GIEP) has been recently developed and discussed [http://geospace.nat.bg; Kartalev et al., 2001;]. This model utilizes (as outer parameters) the experimental distributions of field-aligned currents or electric potentials high latitudes http://www.sprl.umich.edu/mist/limie.html; Papitashvili and Rich, 2001; Papitashvili et al., 2001]. In the GIEP model, we took into account diurnal and seasonal effects by using realistic 3-D distributions of ionospheric conductivities from 85 to 400 km altitudes provided by the semi-empirical models IRI and MSIS. A new essential feature in the GIEP model is its ability to describe (in several differently chosen approaches) a mutual influence of the conjugate (northern and southern) ionospheres. The model provides 2-D global ionospheric electric potential distributions separately (but self-consistently) for each hemisphere assuming the equipotential geomagnetic field lines. These results permit considering not only the cross-polar potential drop over the northern and southern polar caps, but also the "global potential drop" over middle and low latitudes. Another set of outer (to GIEP model) parameters can be specified by an additional system of atmospheric vertical electric currents applied to the lower ionospheric boundary. Therefore, the global electric circuit can be affected by variations in the magnetospheric field-aligned currents applied to the upper ionosphere boundary in the polar regions. Performance of the GIEP model is demonstrated in a way when the "internally-driven" (due to the interhemispheric potential difference) electric currents (permitted to flow between both hemispheres along geomagnetic field lines) are supposed to be equal at every pair of the conjugate points. We examined correlations between the diurnal/seasonal variations of observed high-latitude near-surface vertical electric fields and the modeled global potential distributions for specified conditions and times. Our analysis shows that these variations of near-surface electric fields may correlate better with the global potentials rather than with the cross-polar potentials.


    Kartalev, M. D., V. O. Papitashvili, V. I. Keremidarska, K. G. Grigorov, and D. K. Romanov, Global distributions of ionospheric electric potentials for variable IMF conditions: Climatology and near-real time specification, Proc. Euro Conf. Solar Cycle and Space Weather, Vico Equense, Italy, 24-29 September 2001, ESA Publ. 477, in press, 2001.

    Papitashvili, V. O., and F. J. Rich, High-latitude ionospheric convection models derived from DMSP ion drift observations and parameterized by the IMF strength and direction, revised for J. Geophys. Res., October 2001.

    Papitashvili, V. O., F. Christiansen, and T. Neubert, A new model of field-aligned currents derived from high-precision satellite magnetic field data, revised for Geophys. Res. Lett., November 2001.

  6. On Relations of Cosmic Rays to Space Weather

    Karel Kudela

    Institute of Experimental Physics, Slovak Acad. Sci., Watsonova 47, 043 53 Kosice, Slovakia

    Based on recent publications a review of the links between the ground based cosmic ray measurements and space weather research is presented. The direct relations include the interaction of high energy particles with the materials of the airplanes, satellites, atmosphere and living cells. The ground level effects of the solar flares and their impact on airplanes are illustrated for the event on April 15, 2001. The indirect relations include the interactions of cosmic rays with IMF inhomogenities in interplanetary space. The cosmic ray anisotropy measured by the networks of neutron monitors and muon telescopes indicate the possible precursors of geomagnetic storms. Importance of cutoff reductions for the entry of cosmic rays into the magnetosphere at medium and low latitudes is shown for the storm on March 31, 2001. Relevance of cosmic ray measurements in real time for the purposes of SPECIAL II network is discussed.

  7. Impact of the solar wind variations on the processes in the middle latitude lower atmosphere

    Makarova L.N and Shirochkov A.V.

    Arctic and Antarctic Research Institute, St.-Petersburg, 199397 Russia

    The data of the multiparameter atmospheric measurements at Wank Mountain in Bavarian Alps (47.30°N; 11.09°E; elevation 1780 m) made during 1972 - 1983 were analysed. Detailed information contained in these data gives a rare opportunity to explore the internal atmospheric processes which cause the atmosphere response to impact of the external disturbing forces. Among the latter factors the solar insolation is assumed to be the main or even the sole source of energy responsible for atmosphere behavior. In this study we explored the atmosphere response to variations of the solar wind energy. Influence of this source of energy affecting the middle atmosphere behavior has not been considered so far.

    The main results of this study could be formulated as following:

    1. Magnitude of atmospheric electric field measured at Wank station crucially depends on the solar wind dynamic pressure and IMF structure: the more the solar wind dynamic pressure the less the magnitude of the electric field.
    2. Relative humidity in the atmosphere increases with the electric field enhancement and, correspondingly, decreases with the solar wind dynamic pressure increase.
    3. Atmospheric temperature as expected, increases with the solar dynamic pressure enhancement and decreases with humidity enhancement.
    4. The solar proton fluxes themselves do not produce any notable effect in middle latitude atmosphere during the solar proton events.
    5. All the above-mentioned effects could be explained in frame work of a modified version of the global electric circuit with external EMF generator driving by the solar wind energy. Electric field produced by the currents in this circuit is directed against corrotation electric field of the Earth. Therefore a residual electric field in the middle latitudes decreases with the solar wind dynamic pressure enhancement.
    6. The results of this study confirm our previous finding that the solar wind energy affects the atmospheric behavior in global scale.

  8. Monitoring of global, regional and local perturbations of the atmospheric electric circuit as displayed in short-period pulsations and coherent structures of atmospheric electric field

    E.A.Mareev(1) and S.V.Anisimov(2)

    1. Institute of Applied Physics, Russian Academy of Science, Department of Plasma Physics and Electronics, 46 Ulyanov str., 603950 Nizhny Novgorod, Russia
    2. Borok Geophysical Observatory, Russian Academy of Sciences, Borok, Yaroslavl, 152742. Russia

    The remote sensing of the electric field is necessary for global circuit characterization, thunderstorm electrification study, testing of different theories in the field. Short-period pulsations (10-3 - 1 Hz) of the electric field represent an integral part of atmospheric electric processes found to be important to recognize global components of atmospheric electric circuit activity [Ruhnke et al., 1983] and serve as a sensitive indicator of the boundary layer dynamics, particularly the convective processes and cloud generation. The authors of this project have developed a new method of structural-temporal analysis for these pulsations and applied it to the study of structures of electric field and space charge [Anisimov et al., 1994]. This analysis allowed us to derive particular information on the formation and evolution of aeroelectric structures (AES) and develop a model of aeroelectric structures formation taking into account the occurrence of convective cells with respective turbulent air and space charge density distribution, as well as the cooperative electro-aerodynamic effects in a system of bipolar ions, generated by cosmic rays and radioactivity, and aerosol particles in the terrestrial electric field [Anisimov et al., 1999].

    Recent investigations [Anisimov and Mareev, 2001] show that these pulsations at frequencies 10-2 - 10-1 Hz have a power-law spectrum during fair weather and fog, while the origins of space charge structures in the surface layer are different under different meteorological and geophysical conditions. Revealing a connection of aeroelectric spectra and coherent aeroelectric structures generation to the meteorological parameters and geophysical conditions allows us to promote monitoring of local, global and regional-scale perturbations of the atmospheric electric circuit by means of short period electric field pulsation analysis. The extensive further researches of AES with greater space between the field sensors will be undertaken; the respective database of ground-based electric field and electric current measurements will be created and theoretically analysed. Research of mechanisms of pulsation spectra formation will be continued, including the contribution of convective mechanism. A method of structural-temporal analysis for electric field pulsations is used.

    Stages of study: 1)parameterization of aeroelectric structures in the boundary layer; 2) theory of AES generation development; 3) search for universal spectra of electric field short-period pulsations; 4) theoretical analysis of spectra; 5) simultaneous measurements and spectra analysis of temperature and electric field pulsation; 6) parameterization of convective mechanism for aeroelectric structure formation and evolution, and its global circuit and climate implications.


    Anisimov, S.V. and E.A.Mareev, Aeroelectrical structures in the atmosphere, Doklady Akademy of Sciences, 371, 1, 101-104, 2000.

    Anisimov, S.V., E.A. Mareev and S.S. Bakastov, On the generation and evolution of aeroelectric structures in the surface layer, J.Geophys. Res., 104, D12, 14359-14367, 1999.

    Anisimov, S.V., E.A.Mareev, N.M.Shikhova and E.M.Dmitriev, Mechanisms for the formation of electric field pulsation spectra in the near-surface atmosphere, Radiophysics and Quantum Electronics, 44, 7, 562-577, 2001.

    Anisimov, S.V., S.S.Bakastov and E.A.Mareev, Spatiotemporal structures of electric field and space charge in the surface atmospheric layer, J. Geophys. Res., 99, 10603-10610, 1994.

  9. Modeling of electrical structure of thunderclouds and mesoscale convective systems as connected to initiation of intra-cloud, cloud-to-ground and high-altitude discharge phenomena

    E.A.Mareev, V.Yu.Trakhtengerts, D.I.Iudin, A.E.Sorokin, E.I.Smirnova, S.S.Davydenko, N.A.Bogatov

    Institute of Applied Physics, Russian Academy of Science, Department of Plasma Physics and Electronics, 46 Ulyanov str., 603950 Nizhny Novgorod, Russia

    Recent studies gave evidence of connection of intra-cloud, cloud-to-ground and high-altitude discharge initiation to the actual structure of the space charge and electrical field in thunderstorms and mesoscale convective systems (MCS), including multi-layer charge structure of MCS. In particular [Huang et al., 1999] suggested that different types of space charge structures, leading to positive ground flashes, could result in sprite or elve generation respectively. Many results now support the point by Williams [1998] on the positive charge resevoir for sprite-producing lightning. This point is confirmed also by recently obtained theoretical results [Smirnova et al., 2000] on the modeling of lightning generated electric field transitional processes over thunderclouds. A common way to improve modeling of thunderstorm electric structure is the increase of complexity taking into account different charging mechanisms, their different parametrizations and actual cloud dynamics patterns [MacGorman and Rust, 1998]. The authors of this project are developing a supplementary approach, based on the search of main characteristic structural elements of electrification dynamics. In the framework of such an approach we have modeled particularly: fine-scale electrical stratification of the cloud as a result of instability in a multi-flow system of charged particles [Trakhtengerts, 1989; Mareev et al., 1999]; a branched nonstationary conducting network (drainage system) gathering the macroscopic space charge during lightning inception stage [Iudin et al., 1998, 2000]; electric field and current evolution as a solution of a nonlinear diffusion equation for the field strength in a cloud [Mareev and Sorokin, 1999]; runaway electron avalanche [Smirnova et al., 2001]. We have elaborated also the principles of laboratory modeling for the multi-flow system of ionised air and highly charged aerosol particles, and started with the design of a set-up for this experiment [Mareev et al., 1996].

    We are going:

    • to examine noninductive/inductive thunderstorm-charging mechanisms with regard to the electrical filamentation and electrohydrodynamic turbulence in a thundercloud, and to perform laboratory modeling of electrical interaction for multi-flow charged aerosol particles and weakly ionised air;
    • to develop an autowave model of a thunderstorm cloud and reveal a connection between electrical structure of thunderclouds (gross-scale and fine-scale) and initiation of intra-cloud, cloud-to-ground and high-altitude discharge phenomena;
    • to develop a theory of electric discharge in a gas of aerosol particles;
    • to model severe storms and mesoscale convective systems in a global circuit;
    • to develop a fractal approach for the quantitative description of the macroscopic charge gathering within a thundercloud.

    The recently elaborated theory of fine structure generation will be developed in terms of account for different charge transfer mechanism and application for actual thunderstorm cloud and MCS conditions. The experimental modelling of the flow instability is based on the creation of colliding flows of unipolar charged aerosol and unipolar charged air flow, which form the quasineutral nonequilibrium medium to be favourable for an instability realization. The results of this experiment will help to understand the nature of space charge structure formation and lightning discharge development in thunderstorms.


    Smirnova E.I., Mareev E.A. and Chugunov Yu.V., Modeling of electric field transitional processes, Geophys. Res. Lett., V.27, N23. 3833-3836, 2000.

    Mareev E.A., Sorokin, A.E. and V.Yu. Trakhtengerts, Effects of collective charging in a multiflow aerosol plasma, Plasma Physics Reports, 25, N3, 289-300, 1999.

    Mareev, E.A., and A.E.Sorokin, An autowave model of electric field in a thunderstorm, Radiophysics and Quantum Electronics, 39, 797-814, 2001.

    Smirnova, E.I., V.E.Semenov and E.A.Mareev, Analytical model of high-altitude discharge caused by runaway electron avalanche, JASTP, 2001 (submitted).

    Iudin D.I., Trakhtengerts V.Y. Dynamics of electrical discharges in a thunderstorm cloud. In: Proceedings of Intern. Workshop "Strong Microwaves in Plasmas". N. Novgorod, 2 - 9 August 1999. Ed. by A.G. Litvak. V.2, p. 461, 2000.

  10. The Micro-satellite DEMETER

    M. Parrot

    LPCE/CNRS, Orléans, France

    The micro-satellite DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) is a low-altitude satellite (< 800 km with a nearly polar orbit to be launched by CNES in 2003. The scientific objectives of this project are related to the investigation of ionospheric perturbations due to seismic activity, and to the global study of the Earth electromagnetic environment. The payload of DEMETER is composed of several sensors associated to a data processing unit and a large memory in order to record the information all around the Earth independently from a telemetry station. DEMETER will measure electromagnetic waves from DC up to 4 MHz, and plasma parameters. There are two modes: i) a survey mode to record low bit rate data all around the Earth, and ii) a burst mode to record high bit rate data above main seismic regions. The duration of the mission is two years. This poster will describe the scientific objectives of the project, the payload, the operations, and the relations with other satellites and ground-based measurements.

  11. Geolocating Sprites using an improved ELF/VLF method

    Colin Price(1), Mustafa Asfur(1), Walter Lyons(2) and Thomas Nelson(2)

    1. Department of Geophysics and Planetary Sciences, Tel Aviv University, Israel
    2. Yucca Ridge Field Station, FMA Research, Inc., Fort Collins, Colorado, U.S.A.

    The majority of sprites, the most common of transient luminous events (TLEs) in the upper atmosphere, are associated with a sub-class of positive cloud-to-ground lightning flashes (+CGs) whose characteristics are slowly being revealed. These +CGs produce extremely low frequency (ELF) and very low frequency (VLF) radiation detectable at great distances from the parent thunderstorm. During the STEPS field program in the United States, ELF/VLF transients associated with sprites were detected in the Negev Desert, Israel, some 11000 km away. Within a two-hour period on 4 July, 2000, all of the sprites detected optically in the United States produced detectable ELF transients in Israel. All of these transients were of positive polarity (representing positive lightning). Using the VLF data to obtain the azimuth of the transients, and the ELF data to calculate the distance between the source and receiver, we remotely determined the position of sprite-forming lightning events with an average locational error of 184 km (error of 1.6%).

  12. Lightning and Climate: The Water Vapor Connection

    Colin Price and Mustafa Asfur

    Department of Geophysics and Planetary Sciences Tel Aviv University, Ramat Aviv, 69978 Israel

    The amplitude of future global warming will depend strongly on how upper tropospheric water vapor (UTWV) changes in response to greenhouse gas forcings. There are arguments in support of both positive and negative water vapor feedbacks. To understand these feedbacks it is necessary to understand how UTWV varies on different spatial and temporal scales. However, monitoring long-term changes in water vapor is very difficult, and no single method is in place, or planned, to deal with this problem. We will present evidence showing the close link between UTWV variability and global and regional lightning activity. Continental deep convective storms that transport large amounts of water vapor into the upper troposphere dominate the variability of global UTWV, while also being the storms that produce the majority of our planet's lightning. Furthermore, integrated global lightning activity can be continuously observed from a single location on the earth's surface via the Schumann Resonances (SR), an electromagnetic phenomenon in the atmosphere produced by global lightning. Therefore, observations of the SR may supply a cheap, convenient method of studying the long-term variability of global UTWV.


    V.P.Kim, S.A.Pulinets, V.V.Hegai

    IZMIRAN, Troitsk, Moscow Region, 142190, RUSSIA

    Theoretical model of possible electron density enhancements in the mid-latitude nighttime D-region ionosphere in the presence of anomalous atmospheric vertical electric field is presented. Such electric fields could appear over giant thunderstorm clouds or within the seismoactive zone few days before the severe earthquake. Electric field penetrating into ionosphere and magnetosphere creates the ducts of ionization with perpendicular size of order 300 km. Effective canalization of the coherent and incoherent VLF emissions takes place. The cyclotron resonance interaction with the energetic particles of radiative belts leads to the pitch-angle diffusion of energetic particles, and due to diffusion the part of the particles fall into the loss-cone and precipitates into the atmosphere. Our model calculations show that the nighttime D-region electron density can considerably increase due to precipitating energetic electrons' ionization of the lower atmosphere. Horizontal size of perturbed electron density area is about 300 km. The perturbation effect is expected to be more prominent if a powerful VLF radiotransmitter operates in the vicinity of an anomalous electric field zone. In this case a very dense ionization layer of daytime D-layer type can be formed at altitudes of the upper nighttime mesosphere resulting in the effect of substantial absorption of HF radiowaves propagating over the earthquake preparation area. Our calculations are supported by the experimental measurements of over horizon propagation of VHF FM broadcast signals in Japan before the strong earthquakes, as well as amplitude and phase anomalies of Omega transmitter signals over epicentral zones of forthcoming earthquakes. These effects could be explained by the formation of enhanced ionization layers in the lower ionosphere. Such ionization is provided by the precipitating particles.


    G. Sátori, B. Zieger and J. Bór

    Geodetic and Geophysical Research Institute, Csatkai u. 6-8. H-9401 Sopron, Hungary

    Long-term Schumann resonance frequency records at Nagycenk (NCK), Hungary have been used to determine areal variations of the worlwide thunderstorm activity on seasonal, annual and interannual time scales. The daily frequency range (DFR) of Schumann resonances (SR) is the band in which the resonance frequency shifts up and down during a day. The DFR is related to the size of the region where the random lightning discharges are distributed. The wider, the region is, the smaller the DFR becomes, and vice versa. The mean size (diameter) of thunderstorm regions can be obtained from the DFR using a calibration curve charcteristic of the SR station at NCK. Monthly means of source diameter were determined from May 1993 up to the present. Annual variations with May-June maxima and November-December minima and semiannual variations with April and October maxima were extracted with a filtering technique. The annual areal variation can be explained by the North-South asymmetry of the land-ocean distribution. The annual and semiannual areal variations show a clear, long term (decadal) modulation which might be attributed to a solar-cycle dependence of the worlwide lightning area.

  15. A model evaluation of the ozone density changes caused by various types of corpuscular radiation

    Shirochkov A.V., Makarova L.N., Ul'ev V.A.

    Arctic and Antarctic Research Institute, St.-Petersburg, 199397 Russia

    There are reliable experimental evidences that some strong proton events (SPE) are accompanied by simultaneous intense precipitation of the relativistic (E>1 MeV) electron fluxes -so called relativistic electron precipitation (REP) events. However, the ionospheric and atmospheric effects caused by such combined geophysical disturbances are analysed by the usual methods: as the results of impact of the sole agent -the solar proton fluxes.

    The purpose of this study is to try to separate effects of two simultaneously existing sources of energization of the middle atmosphere: the solar proton and relativistic electron fluxes and to evaluate importance of each of them. An event of May, 1992 when intense SPE was accompanied by significant increase of relativistic (E>2 MeV) electron precipitation as measured by the GOES-7 detectors. We have used in this study our original 1D photochemical dynamical model of the middle atmosphere (altitude range 10-90 km). This model includes the oxygen, hydrogen, chlorine and bromine component groups which interact with each other in 150 chemical reactions. The model consists of several independent which can evaluate numerically the following parameters: a) atmospheric temperature together with concentration of the main atmospheric components: O2 and N2; b) rate of ionization by the solar proton fluxes; c) rate of photodissociation by the solar EUV radiation; d) concentration of the atmospheric minor components; e) rate of ionization by the relativistic electron fluxes.

    The main results of this study are the following:

    1. There are solar proton events where simultaneous intense precipitations relativistic electron fluxes registered.
    2. Both these ionization agents cause their own ionospheric and atmospheric effects at altitudes of its maximum penetration into atmosphere.
    3. Exact evaluation of the effects of the solar proton and relativistic electron fluxes is important for correct understanding of the disturbances in the middle atmosphere.
    4. Ozone layer in stratosphere (at altitudes of its maximum density) can be affected only by the solar proton and relativistic electron fluxes very hard energetic spectra.

  16. Changes in cloud cover associated with Forbush decreases of galactic cosmic rays

    Martin C. Todd(1) and Dominic R. Kniveton(2)

    1. Department of Geography, University College London (UCL), 26 Bedford Way, London, WC1H 0AP Tel. +44 20 7679 4271 Fax. +44 20 7679 4293
    2. School of Chemistry, Physics and Environmental Science, University of Sussex, Falmer, Brighton, BN1 9QJ, UK

    A controversial issue in climate science is the possible effect of galactic cosmic ray flux (GCR) on clouds. Here, we present the results of a study to quantify the relationship between cloud cover and short-term Forbush decreases (FD) of GCR. FD events represent an interesting sampling base for GCR/cloud studies given that there are no known internal modes of climate variability operating with similar temporal frequency. Using an extensive record of global satellite derived cloud products from the International Satellite Cloud Climatology Project (ISCCP) D1 data series, epoch superposition analysis of a sample of FD events was conducted. Cloud anomalies relative to conditions prior to FD events were derived at a range of spatial scales from global, through 5-degree geomagnetic latitude bands to a global grid with 2.5-degree resolution. Resulting cloud anomalies were tested for significance using a randomised Monte Carlo experiment. The results indicate a small but significant (at 0.001% level) decline in the global proportion of cloud cover (of up to 1.4%) immediately prior to and following FD events. Analysis of data averaged over geomagnetic latitude bands reveals that significant cloud anomalies are concentrated in the high latitudes. These anomalies occur largely in the upper-level cloud, and are particularly pronounced (up to -30%) over Antarctica. In contrast, analysis using a sample of FD events associated with solar proton burst events shows no statistically significant cloud anomalies.


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

    Arctic and Antarctic Research Institute, St.Petersburg, Russia

    Fluxes of galactic cosmic rays altered by solar wind and spikes of solar cosmic rays are usually examined as one possible mechanism of solar activity influencing the Earth-s atmosphere. Analysis of wide set of aerological data from the Antarctic near-pole station Vostok has shown that atmospheric perturbations in the Southern winter polar region are better related with interplanetary shocks that always accompany perturbations in galactic and solar cosmic rays. It is possible that these effects are most obvious at the Vostok station because: (1) Vostok station is located at a flat homogeneous plain at height 3.5 km (ice dome), that is not subjected to local atmospheric vortices; (2) Circumpolar atmospheric circulation, with alone circle covering the whole continent, is typical of Antarctica in the winter season, and Vostok station is close to center of this circle; (3) Vostok station is not exposed to the direct solar radiation in period of polar night in winter season; (4) The catabatic type of atmospheric circulation (i.e. vertical type of circulation) is typical of the central part of Antarctic, where the stratosphere cold air masses go down to ice dome and then flow along the dome surface toward the cost. These features allow the Vostok station location to act like a window into the nature of the nighttime middle atmosphere where solar influences are stronger than in the lower atmosphere.

    The detail analysis of the Vostok data for 1978-1992 made it possible to conclude that dramatic changes of the tropospheric temperature observed in the Southern near-pole region in relation to the interplanetary shocks are caused by sharp changes of the IMF Bz component (and, correspondingly, by fluctuations of the interplanetary electric field) typical of the interplanetary shocks. There is a linear relationship between the value of IMF Bz changes and ground temperature at Vostok station: the larger is leap in the southern Bz the stronger is the warming. The regularity is especially supported by fact that cooling at Vostok is observed in relation with the northward Bz leaps. The effect reaches maximum (warming up to 20 degrees in specific events) within one day and is damped equally quickly. It is particularly remarkable that the tropospheric temperature also responds to daily changes of the IMF Bz component, if these changes are considerable. Linkage between the interplanetary electric field and the temperature variations observed in the southern polar region is regarded as evidence of the strong solar wind influence on global electric circuit acting between the ionosphere and ground.

  18. The Trough Based Neural Network Model of the foF2 Values

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

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

    The mid latitude electron density trough has been investigated by Tulunay extensively since 1968 by using the electron density data returned by the ARIEL3 and ARIEL4 satellites. In the past years starting with the COST238: PRIME Action it has been demonstrated that the abrupt gradients of electron densities in space and time of the trough are directly reflected foF2.

    Thus the performance of HF communications are directly affected. In this work an attempt has been made for the modelling to quantify the influence of the ionospheric mid latitude electron density trough on the ionospheric critical frequency foF2 by using neural networks. Data sets are used from the ground stations that include observations in the trough region. It has been demonstrated that the neural net based approaches are promising in modeling of the ionospheric processes. Data generated by using statistical relationships obtained by the Ariel4 data are used to train the neural network. It has been shown with this work that properly constructed NN-based systems, trained and tested with properly organized data are promising in modeling the complex nonlinear processes, such as the influence of the trough on foF2 values.

  19. MEIDEX: An Opportunity for Coordinated Global Measurements of TLE from the Space Shuttle and Ground Stations

    Yoav Yair(1,2), Colin Price(1), Zev Levin(1), Adam Devir(1), Baruch Ziv(1,2), Meir Moalem(1)

    1. Department of Geophysics and Planetary Sciences, Tel-Aviv University Tel-Aviv, Israel 69978
    2. Open University of Israel, 16 Klausner St., Tel-Aviv, Israel 61392

    The Mediterranean Israeli Dust Experiment (MEIDEX) will be carried out from the space shuttle Columbia, scheduled for the STS-107 flight in summer 2002. The 16 days' mission will be in a 39°-inclination orbit, passing over the major thunderstorm regions on Earth. The primary science instrument is a Xybion IMC-201 image-intensified radiometric camera with 6 narrow band filters, boresighted with a wide-FOV color video camera. Both cameras are mounted on a single-axis gimbal with a cross-track scan of ±22°, inside a pressurized canister sealed with a coated quartz window that is mounted in the shuttle cargo bay. Data will be recorded in 3 digital VCRs and downlinked to the ground. During the night part of the orbit there will be dedicated observations toward the Earth's limb above areas of active thunderstorms, in an effort to image TLEs from space. Observations will consist of a continuous recording of the Earth's limb, from the direction of the dusk terminator towards the night side. While earlier shuttle flights have succeeded in recording several ionospheric discharges by using cargo bay video cameras, MEIDEX offers a unique opportunity to conduct targeted observations with a calibrated, multispectral instrument. The Xybion camera has a rectangular FOV of 14.04(H) x 10.76 (V) degrees, that covers a volume of 466km (H) x 358km (V) at the Earth's limb, 1900km away from the shuttle. The spatial resolution is 665m (H) x 745m (V) per pixel, enabling to resolve some structural features of TLE. Optical observations from space will be conducted with the 665nm filter that matches the observed wide peak centered at 670nm that typifies red sprites, and also with the 380 and 470nm filters to record blue jets. Areas of high convective activity will be forecast by using global aviation SIG maps, and uplinked to the crew before the observation. The astronaut will direct the camera toward areas with lightning activity, observed visually through the windows and on monitors in the crew cabin. Simultaneously with the optical observations from space, dedicated ground measurements will be conducted on a global scale. Two field sites in the Negev Desert in Israel will be used to collect electromagnetic data in the ELF and VLF frequency range. Additional ground stations in Germany, Hungary, USA, Antarctica, Chile, South Africa, Australia, Taiwan and Japan will also record Schumann Resonance and VLF signals. The coordinated measurements from various locations on Earth and from space will enable geo-locating and determining the polarity and charge moment of the parent lightning of the optically observed TLE. The success of the campaign will further clarify the global picture of TLE occurrence.

Last update: 2002-02-11, 1348 UT, by Th.Ulich, editor [e-mail | homepage].