Ionospheric processes during the 10 June 2021 partial Solar eclipse at Kharkiv

1Chernogor, LF, Garmash, KP
1V.N. Karazin Kharkiv National University, Kharkiv, Ukraine
Kinemat. fiz. nebesnyh tel (Online) 2022, 38(2):3-22
Start Page: Dynamics and Physics of Solar System Bodies
Language: Ukrainian

A solar eclipse provides the researcher with a rare opportunity to follow the dynamics of the Earth (its internal spheres) — atmosphere — ionosphere — magnetosphere system and variations in the geophysical fields over an interval of a few hours. The disturbances in this system, which are caused by different solar eclipses, are significantly different. The parameters of these disturbances depend on the solar eclipse first contact, the state of space weather, season, the phase of the solar cycle, geographic coordinates, and eclipse obscu¬ration. It should be noted that individual solar eclipses show their own characteristics. The purpose of this paper is to analyze the results of ionosonde observations of the ionospheric disturbances that accompanied the 10 June 2021 solar eclipse at the City of Kharkiv. The maximum phase, Mmax, of the solar eclipse at the City of Kharkiv was observed to be ~0.11 (more precisely 0.112), and eclipse obscuration, Amax, to be ~4.4 %. The first contact occurred at 10:42 UT (13:42 LT) and the fourth contact at 12:12 UT (15:12 LT). The maximum phase happened at 11:28 UT (14:28 LT). To study the features of the variations in the virtual heights and the frequencies, we have used the digital ionosonde located at the V. N. Karazin Kharkiv National University Radiophysical Observatory. The state of space weather has been analyzed. During the solar eclipse and over the reference time intervals on 6 and 9 June 2021, the state of space weather was conducive to observing wave disturbances, which is supported by the magnetic activity index Kp ~ 0.3. The measure¬ments of signal amplitude vs. frequency and vs. height taken at vertical incidence have been analyzed and the features of the ionospheric processes that accompanied the partial solar eclipse and were absent on the reference days has been determined. The solar eclipse was accompanied by an enhancement in wave activity in the ionosphere. The wave trains observed near the ionospheric F2 peak height showed periods of 5 min and 14 min and the 0.6 % and 1.25 % amplitudes of the oscillations in the electron density, respectively. At 240 km, the amplitude of the oscillation with 14-min period increased by 3 %. The 14-min period pertains to atmospheric gravity waves, and the 5-min period to waves of electromagnetic nature. A sharp and considerable increase (from 380 to 560 km) in the virtual height was detected around the instant of greatest eclipse. A weak (equal to or less than 3.3 %) decrease in the electron density that lagged behind the maximum phase of the solar eclipse by 12.5 min was revealed. The loss of electrons rate has been estimated to be 1.33*10–3 s–1, and the electron-ion pair production rate to be 3*108 m–3s–1.

Keywords: aperiodic disturbance, ionosonde, ionospheric parameters, ionospheric process features, quasi-periodic disturbance, solar eclipse