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Microwave Response of the Ionosphere


Microwave Response of the Ionosphere to the Solar Flares and Geomagnetic Storms and its Influence on the Weather and Climatic Phenomena

Tech Area / Field

  • PHY-RAW/Radiofrequency Waves/Physics

3 Approved without Funding

Registration date

Leading Institute
Vavilov State Optical Institute (GOI), Russia, St Petersburg

Supporting institutes

  • Scientific Research Radiophysical Institute, Russia, N. Novgorod reg., N. Novgorod


  • National Observatory of Athens / Institute for Space Applications, Greece, Palaia Penteli\nLaboratoire de Planétologie de Grenoble, France, Grenoble\nEuropean Space Agency, The Netherlands, Noordwijk\nUniversity College London / Department of Physics and Astronomy / Atmospheric Physics Laboratory, UK, London\nCanadian Space Agency / Space Science, Canada, QC, Saint-Hubert

Project summary

The purpose of the project is investigation of the influence of ionospheric microwave radiation on the weather and climatic phenomena during solar flares and geomagnetic storms when microwave radiation increases strongly.

This sporadic radio emission of an ionosphere which accompanies solar flares and polar auroras was first observed more than 30 years ago in Radiophysical Research Institute (NIRFI) in former USSR. However an adequate theoretical model which would enable calculation of the spectrum and intensity of this radiation has not been developed till recently.

During the last 10 years the ionospheric microwave radiation has been studied in Vavilov State Optical Institute (SOI).. To explain the origin of this radiation for the first time the highly excited states (Rydberg states) have been introduced into consideration. The Rydberg states of the atmospheric atoms and molecules are excited by the impact of energetic electrons, namely: photoelectrons, secondary electrons and Auger-electrons.

Rydberg excitation is an intermediate stage between a neutral and ionized components of the ionospheric plasma. Rydberg states accumulate a lot of energy and as a result they are able to produce an incredibly large increases of the microwave radiation intensity as a response to the solar flares and magnetic storms. This phenomenon is connected with the following two circumstances:

  • First, because of the selection rules the radiative transitions from the Rydberg states lie mainly in the microwave spectral range,
  • Secondly, the density of energetic ionospheric electrons increases strongly during solar flares due to the increase of the rates of photoionization which is caused by the X-ray and extreme ultraviolet radiation from the Sun. It also increases during magnetic storms due to the increase of the rates of corpuscular ionization which is caused by electrons and protons precipitating to the upper atmosphere from the radiation belts.

Thus experimental data obtained at NIRFI and theoretical models developed in SOI have shown that microwave radiation of the ionosphere is a radioresponse of the ionosphere to the solar flares and geomagnetic storms. All microwave radiation of the ionosphere penetrates freely through the lower atmosphere to surface. On the other hand it is known from experiments (1990) that microwave radiation of low intensity (from solar radio bursts at cm and dm wavelengths) affects at the humidity and transparence of the atmosphere, because microwave radiation of the Sun influences on the formation of the lower atmosphere clusters from water vapor (it can both increase and decrease the association extent). This is important when take into account the condensation mechanism, which dominates in the solar-weather link.

Flux of the ionospheric microwave radiation during solar flare is stronger than the corresponding flux during usual microwave burst at the Sun. This testifies that a microwave radiation of ionosphere, generated as a result of absorption of X-ray and hard UV radiation of solar flare and excitation of the Rydberg states, might contribute to weather phenomena..

The study of this influence on lower atmosphere – on the weather and climatic phenomena: pressure, temperature and humidity, is a matter of urgent interest of the modern natural science.

The main tasks of the project are following:

  • To develop the techniques and instrumentation for measurements of the sporadic microwave radiation (cm and dm wavelengths) of the ionosphere, to confirm their reliability,
  • To carry out measurement of the intensity of sporadic microwave radiation during solar flares and geomagnetic storms,
  • To study processes that determine the spectral distribution of the Rydberg microwave radiation of the ionosphere,
  • To examine the atmosphere absorption properties in connection with the microwave radiation passing from the ionosphere down to the surface,
  • To analyze correlation between parameters of the ionospheric microwave radiation and weather and climatic characteristics during solar flares and geomagnetic storms using retrospective and current data,
  • To develop the proposals to taken into account the contribution of sporadic microwave radiation on the weather and climatic characteristics during variations of solar and geomagnetic activity, including global changes of climate.


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