Geomagnetism and Aeronomy最新文献

During the expansion phase of a substorm, the poleward jump of auroras (breakup) and the expansion of the auroral bulge are observed. The expansion is accompanied by a negative magnetic bay under the aurora and a positive magnetic bay at mid-latitudes. The magnitude of the negative bay is characterized by the auroral AL-index. The Mid-Latitude Positive Bay index (MPB-index) was previously proposed in order to characterize the positive bay. In this article, the statistical relationship of the MPB-index with the geomagnetic activity at different latitudes and with the parameters of the solar wind and interplanetary magnetic field is investigated. It is shown that all extremely high values of the MPB-index (above 10 000 nT²) are observed during strong geomagnetic storms (when the Dst-index falls below –100 nT), all extremely strong geomagnetic storms (when the Dst-index falls below –250 nT) are accompanied by extremely high values of the MPB-index. Statistically, the MPB-index increases with increasing geomagnetic activity at any latitude. On average, the MPB-index increases with increasing interplanetary magnetic field magnitudes and any of its components. However, for the Bz-component, large values of the MPB-index are observed at its southward orientation. For the plasma parameters of the solar wind, the MPB-index increases most strongly with the increase of its speed. The dependence on the dynamic pressure and on the value of the E_Y-component of the electric field of the solar wind is also strong. However, the MPB-index weakly depends on the density and temperature of the solar wind.

The discussion about the origin of the zebra pattern has been going on for more than 50 years. In many papers it is usually postulated that the double plasma resonance mechanism always works in the presence of fast particles in the magnetic trap. Due to a number of difficulties encountered by this mechanism, works on its improvement began to appear, mainly in a dozen papers by Karlický and Yasnov, where the whole discussion is based on variability of the ratio of the magnetic field and density height scales and the assumption of some plasma turbulence in the source. Here we show possibilities of an alternative model of the interaction between plasma waves and whistlers. Several phenomena were selected in which it is clear that the ratio of height scales does not change in the magnetic loop as the source of the zebra pattern. It is shown that all the main details of the sporadic zebra pattern in the phenomenon of August 1, 2010 (and in many other phenomena), can be explained within the framework of a unified model of zebra patterns and radio fibers (fiber bursts) in the interaction of plasma waves with whistlers. The main changes in the zebra pattern stripes are caused by scattering of fast particles by whistlers leading to switching of the whistler instability from the normal Doppler effect to the anomalous one. In the end, possibilities of laboratory experiments are considered and the solar zebra pattern is compared with similar stripes in the decameter radio emission of Jupiter.

Using the quartile-based statistical' as this approach is used in the present study approach G-PS-VTEC data of the Lhasa observing station (Geographical Lat. 29.66° N, Geographical Long. 91.10° E) are analysed for six months from July 1, 2019, to December 31, 2019, in the light of eleven major shallow earthquakes (M ≥ 5.0, depth < 30 km) occurred in India, Nepal, and China within a radius of 1500 km assuming it as a center. The results of the analysis show anomalous TEC enhancements of 0.08–15.26 TECU, 1–28 days before the occurrence of these earthquakes. The percentage of TEC enhancements seen before these earthquakes range from 0.74–113.20%. Co-seismic TEC enhancements are also noted for the earthquakes (M = 5, 5.4, 5, 5.3, 5) of August 11, 31, 2019, September 7, 2019, October 27, 2019, and December 9, 2019. The range of co-seismic TEC enhancements is 0.01–4.25 TECU and percentage range of these enhancements is 0.07–31.08%. The post TEC enhancements are observed for the seismic events. The range of post TEC enhancements and percentage enhancements in it are 0.12–6.54 TECU and 1.52–36.41% respectively and the duration of these enhancements is found to vary from 1–21 days. Further, these enhancements in TEC data are also examined in the light of magnetic storms and solar activity and it is found that none of these enhancements are associated with solar activity and magnetic storms. The anomalous days are also confirmed by one more statistical technique. Finally, the possible generation and propagation mechanisms for the observed anomalies are also discussed.

Attempts have been made repeatedly to investigate the effect of the geomagnetic activity on the equatorial plasma bubble (EPB) generation. At the moment, it is generally accepted that the geomagnetic activity tends to suppress the EPB generation and evolution in the pre-midnight sector. As for the post-midnight sector, it is believed that the EPB occurrence probability will increase after midnight as the geomagnetic activity increases. Moreover, the growth rates of the EPB occurrence probability will strongly depend on the solar activity: at the solar activity minimum, they will be the most significant. A sufficient amount of the observations is required to confirm these ideas. For this purpose, the EPB observations obtained on board the ISS-b satellite (~972–1220 km, 1978–1979) in the pre- and post-midnight sectors are best suited. The data were considered in two latitudinal regions: the equatorial/low-latitude (±20°) and mid-latitude ±(20°–52°) regions. The LT- and Kp-variations of the EPB occurrence probability were calculated for both groups. (1) It was revealed that the occurrence probability maximum of the EPBs recorded at the equator and low latitudes is observed in the premidnight sector. The EPB occurrence probability decreases with increasing the Kp-index with a delay of 3 and 9 h before the EPB detection. (2) However, the occurrence probability maximum of the EPBs recorded at the mid-latitudes occurs in the post-midnight sector. Their occurrence probability increases slightly with the increase of the Kp-index taken 9 h before the EPB detection. Thus, the idea of the ionospheric disturbance dynamo (IDD) influence on the post-midnight EPB generation has been confirmed. The IDD mechanism “switched on” after some hours of the enhanced geomagnetic activity and favors the generation. However, its influence is weakened during the years of increased solar activity.

Ionospheric disturbances that accompanied the moderate magnetic storm on January 14–20, 2022, are analyzed. The work is based on data obtained from vertical and oblique ionospheric sounding in the northeastern region of Russia and supplemented by observations at HF radars and magnetic observatories. It has been revealed that the amplitudes of positive and negative ionospheric disturbances accompanying this storm are comparable to those observed on other days of January during weak magnetic storms and disturbances. The specific features of the disturbances observed only during the storm in question are as follows: (1) a midnight–morning increase in the maximum observed frequency of one-hop mode of HF radio wave propagation on the paths Norilsk–Tory and Magadan–Tory on 14 January; (2) enhancement of nighttime fluctuations of the critical frequency in the F2 layer in Irkutsk and the maximum observed frequency of one-hop mode on the path Magadan–Tory on January 15; and (3) morning–midday Es layers with limiting frequencies reaching 7 MHz that were observed in mid-latitudes at the end of the first day and beginning of the second day of the storm recovery phase.

The work describes the design of a measurement module (fluxgate compass) and the creation of various magnetometer devices on its basis. These devices are intended for geomagnetic and special works in various conditions and environments both for stationary observation points and for expeditions.

The ionosphere is an inhomogeneous and anisotropic medium in nature. It causes degradation in the performance of positioning through Global Navigation Satellite Systems (GNSS). Generally, the vertical total electron content (VTEC) is used to characterize the ionosphere. The present study can further be used to enhance positional accuracy with a Navigation with Indian Constellation (NavIC) dual-frequency receiver, especially in the Northern region of India where the elevation angle is consistently very low. At such low elevation angles, converting Slant Total Electron Content (STEC) to VTEC and vice versa introduces errors. Therefore, in this study, STEC is used directly instead of VTEC. STEC can be used to analyze dynamic variations in the ionosphere and investigate local and regional ionospheric disturbances. The STEC is dependent on various factors such as solar activity, elevation and azimuth angle of the satellite, seasonal variation etc. Therefore, it is necessary to evaluate the dynamic attributes and variability of STEC to maintain high accuracy in any ionospheric conditions. This research paper focuses on the evaluation of dynamic attributes and variability of Ionospheric Slant Total Electron Content using Navigation with Indian Constellation (NavIC) satellite system. This study utilizes 19 months (from June 2017 to December 2018) dual frequency NavIC data to compute and analyze STEC. The results show a significant effect of satellite elevation angle, azimuth angle, and seasonal STEC variability. The discussion highlights the suitability of NavIC geostationary satellites (PRN3, PRN6, and PRN7) of NavIC for ionospheric studies, space weather applications, and identification of local ionospheric irregularities. The research findings demonstrate the importance of considering dynamic attributes and variability of STEC to model applications for maintaining high accuracy in case of any ionospheric irregularity. Additionally, this research could serve as a reference for future studies in the field of ionospheric-plasmapheric studies and space weather applications using NavIC system.

Autocorrelations of fragments of the Wolf number series (V2) are considered for 6-year forecasting (solar half-cycle). For physical and optimal reasons, fragments similar to one and half cycles are used. Testing is successfully performed on sufficiently reliable pairs of fragments of the series consisting of a fixed and a time-shifted fragment. A pair is selected for testing if the correlation coefficient is 0.91 or more when its components are combined. The original modification of the fixed fragment and the parts of the series following it are used. Similarly, 6-year forecasts after 2023 are produced from the fragment (2008.5–2023.5), which has correlation coefficients from 0.81 to 0.96 with fragments (1978.5–1993.5), (1901.5–1916.5), (1922.5–1937.5), (1964.5–1979.5), and (1985.5–2000.5). The maximum Wolf number (161 ± 30) is expected in mid-2024.

Estimates of the long-term changes in the ionospheric F2 layer parameters (slab thickness, total electron content, height, and maximal electron concentration) are presented and mutually compared. It is shown that these estimates mutually agree and show that both foF2 and hmF2 have been decreasing in recent decades.

The article presents the first results of identifying trends in annual average ionospheric indices ΔIG₁₂ and ΔT₁₂, which are obtained after excluding from IG₁₂ and T₁₂ the dependence of these indices on solar activity indices. In this case, solar activity indices are F10 and F30—solar radio emission fluxes at 10.7 and 30 cm. It was found that for the interval of 1957–2023, all analyzed linear trends are negative, i.e., quantities ΔIG₁₂ and ΔT₁₂ decrease over time, and these trends are significant. In absolute value, they are maximum for ΔIG₁₂, taking into account the IG₁₂ dependence on F10₁₂, and minimum for ΔT₁₂, taking into account the T₁₂ dependence on F30₁₂. Account for the nonlinearity of trends shows that, e.g., after 2010, they intensified. Relations are presented that make it possible, based on data from trends of the ionospheric indices (ΔIG₁₂ or ΔT₁₂), to judge the nature of the Δ foF2 trend over a specific point. For this, using the IRI model for foF2, a coefficient was obtained that gives the relationship between the trends of the ionospheric index and Δ foF2 over this point. Comparison with experimental data at mid-latitudes revealed that trends of the ionospheric indices make it possible to correctly determine the sign of the Δ foF2 trend and the general tendency for this trend change, but the calculated value of the trend over a specific point may differ markedly from the experimental data.