Modeling of the ionosphere dynamics during a magnetic storm requires knowledge of parameter variations in the disturbed thermosphere during the storm. A method to estimate height distributions of temperature and thermosphere composition from satellite density measurements in the upper thermosphere has been proposed. The method description employs data of the SWARM-C satellite measurements during the 17 March 2015 magnetic storm.
Based on numerical model of the ionosphere–plasmasphere coupling, we investigated peculiarities of ion and electron temperature distributions in the ionosphere and plasmasphere due to modification of thermal conductivity coefficients in the regions with highly rarefied plasma.
We carried out comparative analysis of the ionospheric, optic and geomagnetic disturbances observed during night hours of the main phase of the 17–18 March magnetic storm in the East Asian sector. It has been revealed that synchronous peaks of 557.7 and 630.0 nm emission intensity were associated with substorm-like enhancements of the westward electrojet. The strongest two peaks were observed during the shift of electrojet center to the corrected geomagnetic latitude φ’ ~ 55° N.
Based on numerical model of the ionosphere and plasmasphere, we simulated behavior of the ionospheric parameters during the main phase of the 17 March 2015 St. Patrick’s Day geomagnetic storm. It is shown that in the Asian longitudinal sector, the ionospheric response to this magnetic storm was determined by dynamics of the main ionospheric trough, time of the magnetic storm commencement, and duration of the storm main phase.
Intensity variations in red line of atomic oxygen emission were analyzed using the ionosphere-plasmasphere coupling model. These variations were caused by precipitation of energetic electrons from the magnetosphere during the 20 November 2003 geomagnetic storm. The findings were compared to the optical data measured in Geophysical observatory of the ISTP SB RAS (520 N, 1030 E).
A numerical model of the ionosphere has been used to study the dependence of night airglows in red and green lines of atomic oxygen on characteristics of precipitating electrons which can substantially affect conditions in the mid-latitude ionosphere during magnetic storms. It has been established that the precipitations are able to indirectly generate airglow in red and green lines of atomic oxygen by increasing rates of ion formation and heating of thermal electrons, which causes an increase in the rate of dissociative recombination and thermal-electron-collision excitation of the 1D and 1S levels.
We studied the 557,7 and 630-nm atomic oxygen emission responses to the solar wind sharp variations caused by shocks. For the analysis, were used optical and geomagnetic data for the Eastern Siberia and interplanetary magnetic field and solar wind data. The considered emission intensity was found to increase for some cases, whereas, in other cases, there were no responses during sharp variations in solar wind plasma speed and density. The presence or absence of the responses in the emissions was shown to be not related to the disturbance amplitude of the solar wind parameters. We suggested that the emission intensity increase might be caused by electron precipitation from the magnetic trap during the interaction between the solar wind shock and the magnetosphere.
KEYWORDS: Solar radiation models, Solar processes, Wave propagation, X-rays, Ionization, Radio propagation, Absorption, Data modeling, Atmospheric physics, RF communications
The results for modeling of HF radio waves propagation characteristics are given for the periods of solar flares 25.02.2014, 25.10.2013, 13-14.05.2013. The distance–frequency and amplitude-frequency propagation characteristics are calculated on the base of the complex algorithm which includes modules of ionosphere and plasmasphere global models and radio waves propagation model. The results of calculations were compared with experimental data of oblique ionosphere sounding obtained by chirp ionosonde on paths Magadan – Irkutsk, Khabarovsk – Irkutsk and Norilsk – Irkutsk.
The ionospheric response to a geomagnetic disturbance is a complex set of events caused by both the upper atmosphere
and ionosphere parameters and characteristics of the magnetosphere and solar wind. A situation is particularly
complicated during the large geomagnetic storm. We present the results derived from investigating of the ionospheric
response to large geomagnetic storms with the values of index Dst < (-200 ÷ -300nT) observed during two last cycles of
solar activity. Our analysis of the behavior of the ionosphere is based on using the measurements from a network of
ionospheric stations located at different latitudes in the longitudinal sector of 60-150°E. Also there are presented the
results of numerical modeling of ionospheric parameters during the geomagnetic storm on April, 2000δ which show a
good agreement of calculations and measurements. As the results modeling illustrates prolonged negative ionospheric
disturbances observed during geomagnetic storms may be produced by the change of thermosphere composition.
Abrupt decreases of ionization in the F2-layer maximum in afternoon hours have long been observed and associated with
a motion of the main ionospheric trough to the equator during geomagnetic storms. A sudden increase of electron density
followed by its fall is at times observed in afternoon and evening hours. This phenomenon, well-known as the "dusk"
effect, appears during strong storms which commence in early evening hours LT at stations located at subauroral and
middle latitudes. An explanation for abrupt decreases of critical frequencies of F2 layer in afternoon and evening hours
can be the effect of plasma fast convection in a westward direction caused by intense electric fields. The results of the
simultaneous satellite and ground measurements of the effects of fast subauroral ion drifts show that the development of
a narrow band of a westward drift with high velocities causes the intensive depletion of electron density in the F2 layer
for 15-20 min. This is consistent with the fast formation or deepening of the trough in the background ionization. The
purpose of this paper is to investigate peculiarities of this phenomenon in the East-Asian region. Ionospheric storms with
different intensities are examined based on the data of the meridional chain of ionospheric stations located in the region
of East Siberia and China. It has been determined that afternoon troughs can be observed either during the growth and
main phases of strong and moderate storms if their commencements fall on evening hours or during the recovery phase if
they begin some other time. They are mainly observed in the period between equinox and summer. Model calculations of
electron density variations during the storm on April 3-6, 2004 are carried out. It is shown that the location of minimum
and polar wall of afternoon trough coincides with the band of the westward drift in the time sector 13÷17 MLT at
geomagnetic latitudes 55° ÷ 65°.
From September 25 to 27, 1998, a strong geomagnetic storm occurred, during which the planetary index of geomagnetic activity Kp was as high as approximately 8.5, and Dst was approximately -207 nT. During the concerned storm, the Irkutsk Incoherent Scatter Radar measured height-time variations of electron density, electron and ion temperatures and plasma drift line-of-sight velocities. An interpretation of the measurements involved comparing them with results of calculations in terms of a numerical model of the ionosphere and plasmasphere. It was shown that the measured variations of such ionospheric parameters as the electron density, electron and ion temperatures, as well as ion fluxes along the geomagnetic field are reasonably accurately reproduced in model calculations. Furthermore, the ionospheric response to the magnetic storm under consideration was controlled mainly by a disturbance in the composition of the neutral atmosphere. The enhancement of the horizontal wind left the ionospheric response essentially unaffected as a consequence of what occurred in the morning hours when the ion production sources were insufficiently intense.
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