Geomagnetism and Aeronomy最新文献

Geomagnetic storms are disorders in Earth’s magnetic field triggered by solar activity. This research attempts to foretell the total electron content (TEC) using the Kriging and AI model in both low and mid-latitude stations during strong geomagnetic storms that happened on March 17, 2015 and February 3, 2022. This research paper focuses on predicting and analysing TEC anomalies in the ionosphere during the solar storm by using three models: ordinary kriging (OK), cokriging (CoK) and recurrent neural network (RNN). The predicted TEC values by the models are justified with the TIEGCM and KMPCA models. Parameters like RMSE, CC, MAE, and MAPE were applied to assess the execution of predictive models and to quantify the accuracy of predictions. The average RMSE for TEC predicted in the low-latitude region ranges from 4.90 to 5.41, 5.85 to 6.26 and 8.50 to 9.90 for the OK, CoK, and RNN models, respectively. Likewise, the average RMSE for TEC predicted in the mid-latitude region ranges from 1.81 to 4.04, 1.91 to 4.24 and 2.77 to 5.38 for the OK, CoK, and RNN models, respectively. The performance evaluation parameters show that the OK performs better than the CoK and RNN models.

The study estimates the contribution of middle-scale solar wind structures (variations recorded by a spacecraft during ~10 min intervals) in turbulence development in the transition region behind the bow shock. The analysis is based on simultaneous measurements of plasma and/or magnetic field parameters in the solar wind, in the dayside magnetosheath, and on the flanks. The study adopts measurements by Wind, THEMIS, and Spektr-R spacecraft. The properties of the magnetic field and ion flux fluctuation spectra are analyzed in the 0.01–4 Hz frequency range, which corresponds to the transition from MHD to kinetic scales. The dynamics of turbulence properties in the magnetosheath is governed by large-scale disturbances, while structures with smaller scales have an effect in the absence of large-scale structures.

The results of identifying trends in the annual average ionospheric indices ΔIG and ΔT are presented, obtained after excluding from IG and T the dependence of these indices on the annual average solar activity indices. The solar activity indices were F10, Ly-α, and MgII—solar radiation fluxes at 10.7 cm, in the Lyman-alpha line of hydrogen (121.567 nm), and the ratio of the central part to the flanks in the magnesium emission band 276–284 nm. Two time intervals (in years) are considered: 1980–2012 and 2013–2023. It was found that in 1980–2012, all analyzed linear trends were negative: the ΔIG and ΔT values decreased over time; they were very weak and insignificant. Fluctuations of ΔIG and ΔT with respect to trends for Ly-α were almost twice as large as for F10 and MgII. In the interval of 2013–2023, all analyzed linear trends intensified and became significant: the rate of decrease in ΔIG and ΔT over time increased. For MgII this rate was almost twice as high as for F10. For 2013–2023, the MgII index overestimated the contribution of solar radiation to ionospheric indices, especially during the growth phase of solar cycle 25, which began at the end of 2019. As a result, in the growth phase of solar cycle 25, the F10 index became a more adequate solar activity indicator for ionospheric indices than MgII. In the interval of 1980–2012, the F10 and MgII indices changed almost synchronously. The growth phase of solar cycle 25 was the first case this synchrony was disrupted for the entire period of MgII measurements.

The article presents the results of a comparative analysis of the solar proton event on March 30, 2022, which has an unusual time profile of solar proton fluxes, and the previous and subsequent solar proton events (March 28, 2022, and April 02, 2022). Increases in energetic proton fluxes in the interplanetary and near-Earth space are associated with successive solar X-ray flares M4.0, X1.3, and M3.9 and three halo-type coronal mass ejections. The study was based on experimental data obtained from spacecraft located in the interplanetary space (ACE, WIND, STEREO A, and DSCOVR), in a circular polar orbit at an altitude of 850 km (Meteor-M2) and in geostationary orbit (GOES-16, Electro-L2). An explanation has been proposed for the specific features of the energetic proton flux profile in the solar proton event on March 30, 2022: protons accelerated in the flare on March 30, 2022 were partially screened by an interplanetary coronal mass ejection, the source of which was the explosive processes on the Sun on March 28, 2022; late detection of maximum proton fluxes, simultaneous for particles of different energies, is due to the arrival of particle fluxes inside an interplanetary coronal mass ejection. The spatial distribution of solar protons in near-Earth orbit was similar to the distribution at the Lagrange point L1 but with a delay of ~50 min.

The induction and momentum equations are simplified to a dynamical system for the kinetic and magnetic energies in Earth’s core. Stable stationary points of this system give a geomagnetic field of ~10 mT and the cosecant of the angle between the magnetic field vector and fluid velocity vector is on average about 500 at a known speed of ~1 mm/s and a generally accepted dynamo power of ~1 TW. With a generally known typical geomagnetic time on the order of 1000 years, harmonic secular variations on the order of several decades and rapid exponential changes on the order of several months, possibly associated with jerks, were obtained. All this agrees well with dynamo theory, paleomagnetic reconstructions, numerical modeling, and observations. A geomagnetic energy of ~10 mJ/kg is four orders of magnitude greater than the kinetic energy. Under conditions of such dominant magnetic energy, an analytical solution was obtained, which over time converges to stable stationary points. Apparently unlikely catastrophes with virtually zero magnetic energy near partially stable stationary points are discussed.

Dayside high-latitude geophysical phenomena provide a ground-based observer with information about the processes at the dayside magnetopause and/or in the adjacent magnetospheric domains. It is assumed that these phenomena are initiated by changes in the parameters of the interplanetary medium and can therefore be used as a tool to investigate the ways in which solar wind energy penetrates through the magnetopause. Such phenomena include magnetic impulses, which are an isolated train of damped oscillations of two to three bursts with a repetition period of 8–12 min. Eight magnetic impulse events were investigated using data from the Scandinavian IMAGE magnetometer network, for which DMSP satellites flew over the observation area during, shortly before, and immediately after the impulse and crossed the boundaries of several domains. From ground-based and DMSP satellite data, it is shown that the downward field-aligned current associated with the impulses is located away from the magnetopause. This means that the impulse cannot be considered as an ionospheric trace of a reconnected flux tube (flux transfer event, FTE) and/or as a traveling convection vortex (TCV). It is found on a larger statistics that the impulse is preceded by marked changes in the By- and Bz-components of the IMF, while the contribution of rapid changes in solar wind pressure and velocity as well as in the Bx-component of the IMF to the generation of the magnetic impulse is not obvious. A possible scenario of the magnetic impulse initiation by IMF variations is discussed.

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.

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.

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.