Student Opportunities

Here you will find suggestions for research projects suitable as pro gradu (Master's thesis) topics. All topics can be modified if necessary. Please contact us: together we can find the right topic for your interests!

Living in Sodankylä: The observatory can provide comfortable guest rooms for your short as well as long-term visits to SGO. Please note, that for some topics a permanent presence at SGO is not required, and the work can be done elsewhere. In this case, however, visits to the observatory will be necessary; for all projects we require close co-operation with the respective supervisors. Naturally, all assisting staff of SGO will fully support your project.

Language: All projects can be done in English, most can also be done in Finnish. However, we strongly recommend that those Finnish students write their thesis in English, who aim for a career in industry or research, esp. if they intend to continue towards a doctorate. We invite foreign and exchange students in Finland to work with us.

Contact Us! You can contact us directly by telephone (016-619811), fax (016-619875), or e-mail. If you want to send e-mail, please contact SGO supervisors at firstname.lastname@sgo.fi. Supervisors of the Space Physics Group, Dept of Physical Sciences, University of Oulu, can be reached by e-mail (firstname.lastname@oulu.fi), telephone (08-5531378), or fax (08-5531287).

Fields of Research

• Riometers and Imaging Riometers
• Sodankylä Ion Chemistry Model (SIC)
• Coupling of Atmospheric Layers
• Ionosonde Data Analysis
• Long-term Changes of the Solar-terrestrial Environment
• VLF Studies

Riometers and Imaging Riometers

The Sodankylä Geophysical Observatory operates one of the world's largest networks of receivers for cosmic radio noise, riometers. In addition, data will be available from the Global Riometer Array (GLORIA), which is currently under development. These are used to study the variations of ionospheric properties due to the precipitation of high energy particles. Additionally, in cooperation with University of Lancaster, UK, SGO is also involved in operations of the imaging riometer IRIS at Kilpisjärvi. The imaging riometer is able to make a detailed image of the power of cosmic radio noise in the sky. The image consists of 49 points (7 x 7) which, in an altitude of 90 km, cover an area of 200 km x 200 km. Traditional riometers just monitor the power of cosmic noise using one single receiving antenna, with wide beam.

• Pulsations in energetic electron precitation and their relations to magnetic pulsations during a substorm
  
  Contact: Kalevi Mursula, Esa Turunen
  
  During auroral substorms the precipitating electron flux is variable, often so that the high energy precipitation shows pulsation like features, which can be seen in riometer data. This study is a data oriented treatment of spatial and temporal occurence of such pulsations, seen in the Finnish riometer chain data, with comparison of the found events with magnetic pulsation data available at SGO.
  
  
• The energetic electron precitation and magnetic variations during substorm growth-phase
  
  Contact: Anita Aikio, Esa Turunen
  
  Distinct features of high energy energetic electron precipitation can be seen in riometer data during the auroral substorm growth phase. In Finland we have the IMAGE magnetometer network, jointly operated by SGO and Finnish Meteorological Institute, as a perfect tool to map the magnetic variations during the substorms. The work would include selecting suitable substorms and comparing comparing the precipitation features seen in the Finnish riometer chain data with the magnetometer data.
  
  
• Spatial and temporal structures of high-energy electron precipitation events
  
  Contact: Thomas Ulich, Esa Turunen
  
  In addition to the Finnish riometer chain, several collaborating foreign research institutes run riometers in the auroral zone. One of our closest collaborators is University of Lancaster, which is coordinating an international effort to form a joint data access and visualization system for global riometer data. Parts of the proposed Global Riometer Array data, would be accesible already now. Such data offers mapping of the high energy electron precipitation in a large region, as well as detailed information in restricted areas. The study of spatial and temporal structures of high energy electron precipitation events involves use of a large data base, as well as international collaboration with University of Lancaster.
  
  
• Variations of nitric oxide (NO) concentration at high latitudes
  
  Contact: Carl-Fredrik Enell, Esa Turunen, Thomas Ulich
  
  This is a data oriented study using the SGO riometer chain and support by the SIC model. The electron density in the lower ionosphere is normally governed by the Ly-alpha ionisation of nitric oxide. Thus any estimate of electron density profile during qeophysically quiet times could be used as a proxy for variations of the neutral nitric oxide. The riometers give information about the height integrated electorn density. An important aspect of the variation in nitric oxide concentration would be the excess amount of odd nitrogen produced as a result of auroral activity. The effect should be specially important during dark polar night conditions.
  
  
• Artificial heating of the ionosphere and cosmic radio noise absorption
  
  Contact: Tilmann Bösinger, Esa Turunen, Thomas Ulich
  
  Recent studies have predicted that artificial heating has detectable effects on cosmic radio noise absorption measured by riometers. This prediction has not been experimentally verified yet. The aim of this project is to study past heating experiments and carry out dedicated new measurements using the EISCAT Heating facility and radars in Tromsø, Norway, as well as the imaging riometer (IRIS) at Kilpisjärvi.
  
  

Sodankylä Ion Chemistry Model (SIC)

The Sodankylä Geophysical Observatory has created the detailed Sodankylä Ion Chemistry (SIC) Model, for the altitude region from 50 to 150 km. This model is internationally well established as one of the standard computer models of the lower ionosphere. The model is able to calculate both the time behaviour and equilibrium conditions of the ionised and selected neutral constituents.

The existing SIC model can be used to make theoretical investigations of aeronomical problems of the lower ionosphere, for which we have geophysical data available, such as EISCAT incoherent scatter data, or data from the Artificial Periodic Irregularity (API) experiments.

• Modern inverse methods applied to modelling of the ion chemistry of the lower ionosphere
  
  Contact: Markku Lehtinen, Thomas Ulich, Esa Turunen
  
  However, the model would be a much more versatile research tool, if one would employ modern tools of statistical inversion theory for "backwards" applications of SIC, such as determination of temperature, reaction rate constants and the like. Tools for manipulating various parameters as distributions instead of fixed values have been developed in statistical inversion theory and they are known as Markov-Chain Monte Carlo (MCMC) methods.
  The project would include two parts: 1) re-coding the present SIC model utilising the existing tools and 2) showing the benefits of the inversion theoretical approach as compared to the old model, which represents the traditional approach to modelling of the ionospheric chemistry.
  
  
• Sunset-sunrise effects in incoherent scatter radar (EISCAT) data and negative ions in D region
  
  Contact: Esa Turunen, Thomas Ulich
  
  During sunset and sunrise the ionisation of neutral constituents in the atmosphere by solar radiation, as well as dissociation of neutral molecules, is a direct function of the solar zenith angle. The lower the sun is, the more absorption of radiation within a ray path in the upper atmosphere occurs, and the less energy is left for ionisation and dissociation at a given altitude. However, the chemistry of the atmosphere involves different time scales, for different chemical constituents and consequently in the lower ionosphere one observes an asymmetry between sunrise and sunset. This study involves interpreting analysed measurements in the D region by the EISCAT VHF radar with the help of the SIC model, in order to understand the reasons of the sunrise-sunset asymmetry.
  
  
• Metallic ions in the lower ionosphere
  
  Contact: Esa Turunen, Thomas Ulich
  
  Deposition of meteoric material in the upper atmosphere occurs normally at altitudes from 120 -80 km. The metals form both neutral and ionised layers via various dynamical mechanisms. Neutral layers are seen in lidar measurements and the ion layers in radar measurements. Traditionally, the chemistry of the metal layers is studied by decoupling their chemistry from the rest of the atmosphere. Only very recent models in the literature couple the metallic neutral and ion chemistry in the layers. The purpose of this study is to make one step further and investigate what effect a possible coupling of the metal chemistry to other upper atmospheric chemistry would have in modelling of the layers.
  
  
• Negative cluster ions and artificial heating (API) of the lower ionosphere
  
  Contact: Esa Turunen, Carl-Fredrik Enell
  
  The API experiment is a heating experiment where a powerful HF wave is reflected from the F region, generating a standing wave between ground and reflection altitude. This generates an artificial grid pattern in ionosphere, due to periodic disturbances of the electron temperature. When the structure is probed by a radar pulse which uses the same frequency as the heating wave, we get a resonant scattering condition and a signal is seen in the receiver of the probe radar. When the heating is switched off, the signal fades with a characteristic time. This time is related to the physical processes due to which the medium responds to the electron temperature disturbance as electron density change. In this experiment one can study, e.g., the rate of attaching electrons to neutrals in the lower ionosphere.
  Originally negative ions are formed in three-body collisions attaching electrons to oxygen molecules. Further ion-chemistry leads to negative cluster ions. Analysis of API experiments using the SIC model will lead to a quantification of the negative ion population.
  
  
• The role of unknown reaction rates in the ion chemistry of the upper atmosphere
  
  Contact: Carl-Fredrik Enell
  
  The SIC model has a comprehensive reaction scheme, comprising almost 400 reactions. The rate coefficients of these reactions depend on pressure and temperature. However, some of the rates are measured at room temperature and extrapolated whereas others are theoretical estimates. The purpose is to check the sensitivity of the SIC model to uncertainties in the different reaction rates and perturb these to estimate how large the errors are under different geophysical conditions like quiet time or particle precipitation.
  
  

Coupling of Atmospheric Layers

• Effects of solar short-wave radiation

  Contact: Carl-Fredrik Enell

  The Sun's total energy varies only little over a solar cycle and is therefore called the solar constant. However, in the extreme UV and X-ray spectral regions the variation is several orders of magnitude. This affects the composition of the upper atmosphere and therefore also the lower atmosphere due to altered dynamical balance.
  We model the chemical effects of solar short-wave variability for extreme cases and compare the results with local riometer and ionosonde measurements. The aim is to include the results in global models to study the response of the lower atmosphere as well.

Ionosonde Data Analysis

Inversion of Ionograms to Electron Density Profiles

Contact: Thomas Ulich, Markku Lehtinen, Tuomo Nygrén

Vertical sounding of the ionosphere is commonly done using pulsed radars in the frequency range 1-20 MHz. Radar echoes are received from altitudes where local plasma frequency equals the radio wave frequency. The graphical presentation of apparent echo altitude versus frequency of the radio wave is called an ionogram. When knowing how the radio wave travels in the ionosphere, we are able to invert the ionograms to real electron density profiles of the ionosphere.

This work includes as a first step a review of traditional inversion methods like polynomial methods and the POLAN program, which is a widely used standard tool for inversion of digital ionograms. The next step is a redefinition of the physical problem and subsequent coding using Markov-Chain Monte Carlo (MCMC) methods.

Long-term Changes of the Solar-terrestrial Environment

In the field of Solar-Terrestrial Physics we have monitored many important parameters of our space environment for many solar activity cycles, we can look back at more than 40 years of satellite observations, ionosondes are probing the ionosphere since the mid-1930s, radio (light) emissions from the Sun have been measured since more than 100 years, and we can trace back the ever-changing solar activity by means of sunspot numbers until at least 1610.

Nowadays we know that our space environment is not constant: for instance the brightness of the Sun is changing with the 11-year sunspot cycle. Solar-Terrestrial Physics is the study of connections between the Sun and Earth; it links to climatological studies through understanding the atmosphere which is in between us and space. Today we have to learn from past data recordings and understand changes in these data and their effects in order to be able to predict what is going to happen in the future.

• Long-term changes of ionospheric properties observed by the EISCAT incoherent scatter radars
  
  Contact: Thomas Ulich
  
  The European Incoherent Scatter Scientific Association (EISCAT) is now running its radars for about two solar cycles (>20 yrs) and measures, e.g., ion and electron temperature, electron density, and plasma velocity as a function of height (profiles). The task is to study selected past and recent measurements in order to see if and how the ionosphere above Tromsø has changed during these years. This project is suitable for a M.Sc. thesis (12 ov or 20 ov).
  
  
• Response of D-Region Ion Chemistry to a Changing Solar Spectrum
  
  Contact: Thomas Ulich, Esa Turunen, Carl-Fredrik Enell
  
  The task will be to study variations in the Sun's light output, not only the total solar irradiance (wrongly called the "solar constant"), but also the question of how does the solar spectrum change with solar activity with special emphasis on the X-ray and UV parts of the spectrum. The effects of these changes can be studied with the Sodankylä Ion Chemistry (SIC) model by testing a number of typical spectra in combination with selected geophysical conditions of, e.g., high and low solar activity, geomagnetic activity, particle precipitation, solar flares and the like. This study is suitable for students at any level of studies (literature study, research project, M.Sc. thesis, possibly part of Ph.D. thesis).
  
  
• Cosmic ray induced ionization of the troposphere and a possible link to cloud formation
  
  Contact: Ilya Usoskin
  
  A detailed quantitative model of cosmic ray induced ionization of the troposphere has been developed recently within SGO/OY, and the first results suggest for a quantitative link between this ionization and low cloud cover, particularly so in the sea and costal regions. A more detailed study is needed to disentangle local and seasonal effects in the cloud data and to develop a more feasible model, including realistic aerosol loading and seasonal variations. Also, different types of clouds should be studies separately. The project will include literature search, modelling and data analysis in the field of atmospheric physics and cosmic rays. The results are expected to be published in high rank scientific journals.
  
  

VLF Studies

Correlations between VLF waves and magnetic Pc1-Pc3 pulsations

Contact: Tauno Turunen, Jyrki Manninen, Kalevi Mursula

It is known that magnetic Pc3 pulsations can modulate VLF emissions. This is not wave-wave interaction but Pc3 waves affect the generation region of VLF emissions and the intensity of VLF emissions is varying with the period of Pc3 pulsations.

Some effects may exist between magnetic Pc1 pulsations and VLF emissions but this cannot be seen similarly as for Pc3 modulations. There is no evidence for intensity modulation. However, the VLF activity seems to behave in a certain way when simultaneous Pc1 pulsations have been observed.

Magnetic ULF waves are related to the cyclotron resonance of positive ions, and correspondingly VLF waves are generated by the cyclotron resonance of the negative electrons. That is the reason why ULF waves are left-handed polarised and VLF waves are right-handed polarised. So, how it is possible that these two opposite wave type can interact?