Speaker
Description
Radio diagnostics of the ionosphere based on measurements using LOFAR and GNSS and their combination, and using data from ionosondes, satellites, incoherent scatter radar, etc. is being used to solve a number of practical (such as ultra-high-precision positioning) and fundamental problems in the physics of ionospheric plasma and coupling in the system Sun-Solar Wind (SSW)-Lithosphere (Earth)-Atmosphere-Ionosphere-Magnetosphere (LEAIM).
(1) We present the results of modelling and comparison with available experimental data on the following aspects of coupling in the LEAIM system and Structures in the Ionospheric Plasma. (i) A linear model of excitation of resonant wave train (RWT) of Atmospheric Gravity Waves (AGW) by the solar terminator is constructed. The main characteristics (wavelength, effective velocity and period) of long-period (about 1 hour) gravity waves correspond to GNSS observations. It is shown that the actual spatial periods determined on the basis of RWT maxima and minima differ by tens of percent, and their values correspond to those determined using GNSS data. The corresponding short-period (of the order of a few mins.) periods were detected on the basis of LOFAR data, with high-frequency electromagnetic wave (HFEMW) emission from Cassiopeia supernova remnant. (ii) Models of resonant ionospheric disturbances/TID, detected using satellite and LOFAR data, are currently being developed. The resonant disturbances in question may be associated with AGW resonators and waveguides present at various altitudes in the atmosphere-ionosphere, as well as with the presence of shear wind in the E and F regions of the ionosphere (in the thermosphere). According to our assumption, the corresponding ionospheric disturbances with periods of the order of the Brunt-Väisälä period are observed by LOFAR, with HFEMW radiation from pulsars.
(2) A fundamental task of ionospheric physics is also to determine the mechanisms that limit the amplitudes of the above-mentioned resonant disturbances. A model for AGW excitation is currently being developed taking into account nonlinear losses that determine amplitude saturation.
(3) Analytical relationships have been obtained that describe the dynamics of the Perkins instability in plasma in the 2.5+1-dimensional approximation (taking into account the integration of the corresponding equations along the direction of the geomagnetic field) and in the presence of AGW. A corresponding numerical model is under development. Test numerical results for the disturbances of the plasma ionospheric layer Es under the influence of the propagating AGW are obtained.
Possible applications of the obtained results and the corresponding prospects for radio diagnostics of ionospheric space weather are discussed.
