Effects of the super-powerful tropospheric western Pacific phenomenon of September–October 2018 on the ionosphere over China: results from oblique sounding

Doppler measurements at oblique propagation paths from the city of Harbin, the People's Republic of China (PRC), to 10 high-frequency (HF) radio broadcast stations in the PRC, Japan, Mongolia, and the Republic of Korea captured the response in the ionosphere to the activity of the super typhoon, Typhoon Kong-rey, from 30 September to 6 October 2018. The Harbin Engineering University coherent software-defined radio system generates the database containing the complex amplitudes of the radio signals that have been acquired along 14 propagation paths since 2018. The complex amplitudes are used for calculating the temporal dependences of the Doppler spectra and signal amplitudes, and the Doppler spectra are used to plot the Doppler shift as a function of time, fD(t), for all rays. The scientific objectives of this study are to reveal the possible perturbations caused by the activity of Typhoon Kong-rey and to estimate the magnitudes of wave parameters of the ionospheric plasma and radio signals. The amplitudes, fDa, of the Doppler shift variations were observed to noticeably increase (factor of ∼2–3) on 1–2 and 5–6 October 2018, while the 20–120 min periods, T, of the Doppler shift variations suggest that the wavelike disturbances in the ionosphere are caused by atmospheric gravity waves. The periods and amplitudes of quasi-sinusoidal variations in the Doppler shift, which have been determined for all propagation paths, may be used to estimate the amplitudes, δNa, of quasi-sinusoidal variations in the electron density. Thus, T≈20 min and fDa≈0.1 Hz yield δNa≈0.4 %, whereas T≈30 min and fDa≈0.2 Hz give δNa≈1.2 %. If T≈60 min and fDa≈0.5 Hz, then δNa≈6 %. The periods T are found to change within the 15–120 min limits, and the Doppler shift amplitudes, fDa, show variability within the 0.05–0.4 Hz limits.</p

INFLUENCE OF GLOBAL SEISMIC ACTIVITY ON IONOSPHERE AND NEAR-EARTH ATMOSPHERE PARAMETERS

Subject and Purpose. The catastrophic magnitude of life and monetary losses associated with earthquakes spurs extensive searches for reliable earthquake precursors. It is common knowledge that lithospheric processes have a direct bearing on the state of atmosphere and ionosphere during earthquakes. However, the usual practice is to enquire things in the immediate vicinity of the hypocenter, notwithstanding the global nature of seismic processes. The present work is different as considers the changes of pressure and temperature in the near-Earth atmosphere and the total electron content (TEC) in the ionosphere for world regions at arbitrary distances from hypocenters of strong earthquakes. Methods and Methodology. Employed are the data from the maps of the ionospheric TEC and the maps of the pressure and temperature in the atmospheric surface layer in world regions of 40°N latitude. The quantitative estimates are provided by the superposed epoch analysis for winter seasons between 2012 to 2018. Days of strong earthquakes of the Richter magnitudes within 6.3 to 7.9 are taken for the "zeros" whatever the geographical coordinates of the event. Results. The near-Earth atmosphere pressure P0 shows a decrease for about 5 days before the earthquake and gets elevated for about 5 days after the event. The air temperature T behaves in the opposite way. The TEC shows a sharp increase 2 to 5 days before the earthquake. The typical deviations ΔP0 and ΔT are of up to 2 hPa and 0.3 K, respectively. The TEC deviations, ΔTEC, are within 3 to 4%. Where the longitudes fall on the lithosphere plate boundaries, these deviations are nearly doubled. Also, the magnitude of the effect is higher in the regions where the atmospheric pressure is lower. The established patterns indicate that the gas release from underground plays an important role in the lithosphere-atmosphere and lithosphere-ionosphere interaction effects. In this case, the main part is played by radon fluxes that initiate the near-Earth atmosphere ionization and trigger a whole chain of secondary processes. Conclusions. The results of the work indicate that atmospheric and ionospheric effects caused by lithospheric processes take place at arbitrary distances from strong earthquake hypocenters. Gaseous emissions from underground play an important role as a primary factor of these global effects

NEAR-ZONE IONOSPHERIC DISTURBANCES CAUSED BY EXPLOSIVE ERUPTION OF TONGA VOLCANO ON 15 JANUARY 2022

Subject and Purpose. The thermal energy of the Tonga volcano reached 3.9 ·10¹⁸ J, its power amounted to 9.1 ·10¹³ W. The energy and power of the blast waves approached (6.7...7.5) ·10¹³ J and 1011 W, respectively. Ionospheric effects caused by the explosive eruption of the Tonga volcano on January 15, 2022 have received due attention. It was established that the ionospheric disturbances spread over global distances, with the greatest disturbances occurring in the near zone. The aim of the present paper is to describe aperiodic and quasi-periodic disturbances started by the Tonga volcano explosion and occurring in the near ionospheric zone. Methods and Methodology. To detect ionospheric disturbances generated by the volcanic eruption, temporal variations of the total electron content (TEC) in a vertical column in the ionosphere were analyzed. The total error of the TEC estimation did not exceed 0.1 TECU. Results. The quantitative characteristics of ionospheric disturbances caused by the explosive eruption of the Tonga volcano have been obtained. It was proved that the appearance of the ionospheric "hole" was caused directly by the volcanic explosion. With distance away from the volcano, the TEC deficit in absolute values decreased from ~10 to ~2.5 TECU. As that was happening, the time taken to form the ionospheric "hole" increased from ~20 to ~100 min. Three groups of disturbances were observed. One group picks out disturbances having an N-shaped profile and caused by a blast wave with a speed exceeding ~1 000 m/s. Another group includes disturbances with a propagation speed within ~340...620 m/s, which is characteristic of atmospheric gravity waves at ionospheric heights. The last group is specified by the disturbance propagation speed within ~110 to 320 m/s. The disturbances of the kind can be generated by tsunamis, Lamb waves and atmospheric gravity waves. The wave disturbance periods varied within ~ 5 to 20 min, the disturbance amplitudes were within 0.5...1.0 TECU. Conclusions. It has been proven that aperiodic and quasiperiodic ionospheric disturbances in the near zone were caused directly by the explosion of the Tonga volcan

LARGE-SCALE REDUCTIONS IN THE ELECTRON DENSITY OF IONOSPHERIC F-REGION, OBSERVABLE ALONG ROCKET TRAJECTORIES AT LAUNCH

Purpose. The object of the study are electron density depletions (‘holes’) occurring in the ionospheric F-region under the action of rocket exhaust products. The purpose is to present and discuss the results of observations concerning the ionospheric holes that were detected in the course of a number of launches of medium-lift Kosmos vehicles from the Kapustin Yar spaceport. Nei- ther that cosmodrome, nor the rocket type had been subjects of similar analysis before. Design/methodology/approach. The observations at the Kapustin Yar cosmodrome were performed with a portable vertical Doppler sounder. The beats between a reference signal and the one reflected from the ionosphere were subjected to spectral analysis, which allowed identifying the principal mode of the Doppler frequency shift and establishing time dependences of that frequency shift. An ionosonde located nearby was used for monitoring the underlying state of the ionosphere. Findings. The measurements performed with the vertical Doppler sounder near the launch site of the medium-lift Kosmos rocket have allowed obtaining first estimates for the principal parameters of the ionospheric holes arising in the F-region along the vehicle trajectory, as well as for the accompanying quasi-periodic variations in the electron density. The spatial scale sizes of the holes have been found to be in excess of 300 km, while the electron density reductions may attain » 50 %. These results are in agreement with the data obtained by international researchers for effects from heavy- and super heavy-lift launch vehicles. Also, note that the types of propellant differed significantly. The propagation velocity of the hole’s front edge was estimated to be » 140 m/s. The hole formation was accompanied by quasi-periodic variations in the Doppler frequency shift as a result of radar signal scattering from the electron density fluctuations produced by propagating atmospheric gravity- and infrasonic waves. The atmospheric gravity waves showed periods in the range from 7 to 20 minutes, and the infrasonic waves had a period close to 2 min. The amplitudes of quasi-periodic electron density variations were estimated for the two modes to be » 0.3 ¸1.5 % and » 0.02 ¸ 0.03 %, respectively. Conclusions. Medium-lift launch vehicles (mass of a few hundred tons) are capable of forming ionospheric ‘holes’ of several hundred kilometers in size and of reducing the electron density in the F-region by a factor greater than 2