We address the sequence of Sun-to-Earth phenomena, that enables to study the mechanism for geoefficiency of eruptive prominences propagating from the Sun inside coronal mass ejections (CMEs). An eruptive prominence ejected in the solar wind (SW) moves at the SW velocity Earthward like adiamagnetic structure of eruptive prominence (DSEP).The key feature of the latter is a largesharp plasma concentration jump N inside the DSEP at a simultaneous sharp drop in the interplanetary magnetic field (IMF) modulus B. It is the anti-correlation between the N and B profiles in DSEP, due to which its contact with the magnetosphere may lead not only to magnetosphere compression, but also to penetration of DSEP substance into the magnetosphere. The duration of the magnetospheric disturbance (in the form of dayside auroras), global increase in the current systems, charged particle flux enhancement in the radiation belts, and generation of the irregular Pi2-3 oscillations aredetermined by the DSEP size. We present statistical investigations into DSEPs observed in different years of solar activity and builta qualitative modelfor DSEP geoefficiency.

В статье рассматриваются особенности магнитосферного отклика на воздействие диамагнитной структуры солнечного ветра, вызвавшего генерацию геомагнитных пульсаций Рс1 типа шеврон, зарегистрированных на сети магнитометров CARISMA и спутниках THEMIS 07.09.2023. Исследованы их связь с суббурей, широтно-долготные и частотные характеристики. На основе пространственно-временных закономерностей в распространении пульсаций и особенностей связи с суббурей, предложена гипотеза их происхождения в результате выброса суббуревого плазмоида из хвоста магнитосферы и его движения в системе конвекции магнитосферы западном направлении.

Utilizing 1-minute resolution data on the geomagnetic indices SYM-H, AE, solar wind parameters (velocity Vsw and density Np), and z-component Bz of the interplanetary magnetic field (IMF) during solar cycles 23 and 24, we have statistically analyzed the correlations between geomagnetic activity (storms and substorms), Vsw, Np, Bz, and energy coupling functions of solar wind and Earth’s magnetosphere. For the selected 131 CME-driven storms, SYM-H stronger depends on Vsw and B than other parameters, whereas the selected 161 CIR-driven storms have nearly the same dependence on the solar wind electric field, the rate of open magnetic flux dφ/dt, and the reconnection electric field Ekl. Thus, the solar wind electric field and the dayside magnetic reconnection are likely to have different contributions for storms of the two types. During storms of different types, the substorm intensity AE relies mainly on the IMF Bz, rate of open magnetic flux and reconnection electric field.

It is shown that a diamagnetic structure (DS) of the slow solar wind (SW), the source of which on the Sun was a chain of streamers, arrived at Earth’s orbit on December 22, 2015. It interacted with Earth’s magnetosphere under conditions when the northward Bz component of the interplanetary magnetic field (IMF) remained for a long time in preceding undisturbed SW. The interaction and a sharp change in the direction of Bz to the south generated an isolated substorm whose duration depends on the duration of interaction with the DS. The substorm began at midday with the passage of the DS into the magnetosphere and spread to the east. All phases of the substorm — growth, expansion, and recovery — were observed for two hours. Variations in the SW and IMF parameters are shown to coincide for the isolated substorm whose energy source was the slow solar wind DS, and a trigger was the abrupt change in the direction of the vertical IMF component from north to south. The coincidence is justified by statistical generalizations of the same parameters in 40 % of cases of long-term observations of individual substorms whose trigger was a change in Bz direction.

This article describes in detail ultra-low frequency (ULF) burst of oscillations, which was observed on April 23, 2002 immediately after a sudden geomagnetic pulse. The source of the pulse was a sharp inhomogeneity of the solar wind, which was acting on the magnetosphere, accompanied by a jump in dynamic pressure. We used simultaneous measurements of the magnetic and electric fields, as well as plasma parameters from the Polar satellite and data from induction magnetometers at the Mondy and Borok observatories. Polar spacecraft and obs. Mondy were near the noon meridian at the time of the burst recording. Comparing the time regime of dynamic spectra of oscillations on Earth and in space with on-board records of variations in the intensity and anisotropy of charged particles, we assumed that the burst of ion-cyclotron waves was excited as a result of the effect of a sudden impulse on the magnetosphere. The packet of these waves ran along the field line to the conjugate point in the ionosphere, and then propagated along the ionospheric waveguide. These conclusions are compared with another event on June 28, 1999, also associated with a sudden impulse. In this case, the form of the dynamic spectrum of the burst is characteristic not of ion-cyclotron, but of fast magnetosonic waves. Possible burst generation mechanisms of both types are discussed.

The layering of the ionosphere leads to the formation of resonators and waveguides of various kinds. One of the most well-known is the ionospheric Alfvén resonator (IAR) whose radiation can be observed both on Earth’s surface and in space in the form of a fan-shaped set of discrete spectral bands (DSB), the frequency of which changes smoothly during the day. The bands are formed by Alfvén waves trapped between the lower part of the ionosphere and the altitude profile bending of Alfvén velocity in the transition region between the ionosphere and the magnetosphere. Thus, IAR is one of the important mechanisms of the ionosphere-magnetosphere interaction. The emission frequency lies in the range from tenths of hertz to about 8 Hz — the frequency of the first harmonic of the Schumann resonance. The review describes in detail the morphology of the phenomenon. It is emphasized that the IAR emission is a permanent phenomenon; the probability of observing it is primarily determined by the sensitivity of the equipment and the absence of interference of natural and artificial origin. The daily duration of the DSB observation almost completely depends on the illumination conditions of the lower ionosphere: the bands are clearly visible only when the D layer is shaded. Numerous theoretical IAR models have been systematized. All of them are based on the analysis of the excitation and propagation of Alfvén waves in inhomogeneous ionospheric plasma and differ mainly in sources of oscillation generation and methods of accounting for various factors such as interaction of wave modes, dipole geometry of the magnetic field, frequency dispersion of waves. Predicted by all models of the cavity and repeatedly confirmed experimentally, the close relationship between DSB frequency variations and critical frequency foF2 variations serves as the basis for searching ways of determining in real time the electron density of the ionosphere from IAR emission frequency measurements. It is also possible to estimate the profile of the ion composition over the ionosphere from the data on the IAR emission frequency structure. The review also focuses on other results from a wide range of IAR studies, specifically on the results that revealed the influence of the interplanetary magnetic field orien tation on oscillations of the resonator, and on the facts of the influence of seismic disturbances on IAR.

Показано, что на орбите Земли 22.12.2015 г. взаимодействие диамагнитной структуры (ДС) медленного солнечного ветра с магнитосферой после продолжительной северной ориентации Bz генерирует изолированную суббурю, длительность которой определяется длительностью ДС. Суббуря начинается в околополуденные часы прохождением ДС в магнитосферу и распространяется к востоку. В течение двух часов наблюдаются все фазы суббури – подготовительная, взрывная и восстановительная. Протоны ДС, генерируясь в области источника, достигают орбиты Земли и, взаимодействуя с частицами радиационных поясов, вызывают генерацию колебаний IPDP в околополуденные часы в большом широтном диапазоне.

We report on the dynamics of field-aligned currents (FACs), broadband geomagnetic pulsations, and airglow obtained from the Irkutsk (IRK), Mondy (MND), and Borok (BOX) midlatitude geomagnetic observatories and the Tory (TOR) optical observatory during storm substorms. For the first time, using the short duration, Delta t < 0.5 min, high-frequency component of the burst pulsations (Pi1B), we determined the substorm double expansion phase (EP) onsets <5 min apart, which is hardly possible by means of the low-frequency (periods of 2-5 min) Psc/PiB pulsations. We argue that the observed burst pulsations are the result of prompt changes in the solar wind dynamic pressure and/or the current circuit related to the westward electrojet. Each pulsed source can excite short bursts of broadband electromagnetic modes of the ionospheric Alfven resonator in the range of short-period pulsations with a periodic resonance structure of the spectrum characteristic of the observed Pi1B/Psc pulsations. Plain Language Summary We explored geomagnetic and optical midlatitude observations during storms. In addition to the common low-frequency (periods of 2-5 min) Psc/PiB pulsations, we used the short-period part (Pi1B) of burst pulsations with T < 10 s that allowed us to determine not only isolated substorm expansion onsets but also double substorm onsets and series of onsets of short substorm activations or pseudobreakups during storms. This is hardly possible with the commonly used long-period pulsations (Pi2, Pi3) that are problematic due to their long duration.

Within substorm activations during two superstorms (2000 and 2003) from the observations at mid-latitude geomagnetic observatories, we study short-period irregular geomagnetic pulsations and airglow in the 557.7 nm and 630.0 nm atomic oxygen emission lines, and in the 391.4 nm ionized nitrogen molecular band. Through the genuine magnetogram inversion technique, from the 1-minute data of the ground-based magnetometer global network, we investigate the distribution dynamics for field-aligned currents (FACs) in the ionosphere. The relation is shown between pulsation bursts and airglow disturbances in the post-midnight sector to precipitations of energetic electrons (~keV) and increase in the R2 upward FACs.

We study two events of structured Pc1 waves (pearls) observed by CARISMA magnetometers during a period of quiet magnetic (Kp ~1) and solar wind conditions on 1 August 2008. Bursts of proton precipitations and electromagnetic ion‐cyclotron waves were simultaneously observed by NOAA/POES and GOES satellites at dayside. Apparent correspondence was found between ground pearl pulsations and magnetospheric compressions observed by GOES and THEMIS satellites. We have found the Pc1 wave splitting into very close subfrequencies (within 0.1 Hz) that can be explained by weak magnetospheric compressions. The compressions are caused by pressure pulses originated from transient foreshock and interplanetary magnetic field discontinuities observed upstream of the bow shock by the THEMIS‐C probe. Thus, the observed pearls are compression‐related Pc1 waves generated under transient foreshock conditions.

Using the June 22, 2015 event as an example, we present new data confirming the presence of a precursor of the sudden magnetic impulse caused by a powerful interplanetary shock wave (ISW). The precursor in the form of a train of oscillations (broadband pulse) with a falling frequency in the range 0.25÷11 Hz with a duration of ~20 s, which had a spectral resonance structure, was recorded globally by a network of induc-tion magnetometers at 18:33:27 UT. No significant phase delays of the signals were detected in four fre-quency bands at widely spaced observatories. It is sug-gested that the impulse can be excited in the Earth — ionosphere waveguide by a pulsed electric field which occurs in the ionosphere due to the short-term impact of ISW on the magnetosphere.

We study geomagnetic disturbances and aurora observed near Irkutsk (GEO: 52.2 degrees, 104.5 degrees) at mid-latitude observatories of the Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences (ISTP SB RAS) during the 2003 November 20 superstorm. Based on the data from the world network of magnetometers and on the magnetogram inversion technique, we found the auroral oval boundaries, the westward electrojet position, and calculated the parameters for the auroral electron energy distribution. We found a relationship of precipitations of energetic electrons (>= 1 keV) with the bursts of the Pi1B/Pi1c pulsations and intensity in the 557.7 nm emission and in the 360-410 nm spectral channel observed in the postmidnight sector within the period, when the auroral oval southern boundary lowered below the latitude of Irkutsk. The origin of the observed emissions at the middle latitude is related to electron precipitations in the main and equatorial parts of the westward electrojet. Modeling the ionosphere parameters showed that collision of oxygen atoms with thermal electrons and deactivation of excited nitrogen atom N(D-2) at collisions with oxygen molecules make the main contributions to the 630 nm total intensity. During the addressed superstorm, two types of mid latitude auroras were probably observed: diffuse aurora and/or type "d", as well as emission irregular variations typical of normal auroras related to the auroral energy particle precipitation.

The ionosphere monitoring is an important task because it allows us to adjust the forecasts of radio wave propagation, specify the environment models, and follow the changes of space weather. Currently sounding of the ionosphere is produced by the HF radio waves from the Earth's surface using ionosondes, as well as by raying signals from satellites. Our goal is to draw attention to the possibility of the diagnosis of the ionospheric parameters by detecting ultra-low frequency (ULF) electromagnetic emission generated in the so-called Ionospheric Alfvén Resonator (IAR). To do this, we offer the observations of the IAR emission made the first time simultaneously at three stations using identical induction magnetometers. The stations are located along the same meridian, two of them are mid-latitudinal; the third one is situated in the auroral zone. We compare the main features of the observed multi-band emission (frequency, amplitude, and frequency difference between adjacent harmonics) with ionospheric parameters measured at the stations using ionosondes and GPS-observations. Diurnal variations of the ionospheric and ULF emission characteristics are also compared. The results show that there is quite a reliable connection between the resonant frequencies of the resonator bands and the critical frequency of the F2 layer of the ionosphere, namely, the frequency of the IAR emission varies inversely as the critical frequency of the ionosphere. This is due to the fact that the frequency of oscillation captured in the resonator is primarily determined by the Alfvén velocity (which depends on the plasma density) in the ionospheric F2 layer. The correlation varies at different stations; at the high latitudes it is smaller, but is generally well observed along the whole meridian. This gives hope for the opportunity to develop a method for evaluating the critical frequency of the F2 layer of the ionosphere according to ULF observations in the 0.5-10 Hz frequency range. This method is particularly in demand for the high latitudes, as there is often not possible to measure the critical frequency by conventional methods due to significant disturbances.

Knowledge of the ionospheric state allows us to adjust the forecasts of radio wave propagation, specify the environment models, and follow the changes of space weather. At present, probing of the ionosphere is produced by radio sounding with ground ionosondes, as well as by raying signals from satellites. We want to draw attention to the possibility of the diagnosis of the ionospheric parameters by detecting ultra-low frequency (ULF) electromagnetic emission generated in the so-called ionospheric Alfvén resonator (IAR). To do this, we present observations of the IAR emission made simultaneously for the first time at three stations using identical induction magnetometers. The stations are within one-hour difference of local time, two of them are mid-latitudinal; the third one is situated in the auroral zone. We compare frequency and frequency difference between adjacent harmonics of the observed multi-band emission with ionospheric parameters measured at the stations using ionosondes and GPS-observations. Diurnal variations of the ionospheric and ULF emission characteristics are also compared. The results show that there is quite a stable correlation between the resonant frequencies of the resonator bands and the critical frequency of the F2 layer of the ionosphere, namely, the frequency of the IAR emission varies inversely as the critical frequency of the ionosphere. This is due to the fact that the frequency of oscillation captured in the resonator is primarily determined by the Alfvén velocity (which depends on the plasma density) in the ionospheric F2 layer. The correlation is high; it varies at different stations, but is observed distinctly along the whole meridian. However, coefficients of a regression equation that connects the ionosphere critical frequency with DSB frequency vary significantly from day to day at all stations. The reason for such a big spread of the regression parameters is not clear and needs further investigation before we are able to develop a method for evaluating the ionosphere critical frequency using the IAR emission observations. Such a method may prove to be useful as an additional alternative to the basic method for probing the ionosphere using digisondes. This is especially important for auroral regions, where the presence of strong absorption, shielding by a lower layer, stratification, the presence of echoes, etc. make the sounding difficult.

So-called “killer” electrons are electrons of relativistic energies (more than 1–2MeV) forming the outer radiation belt. Their fluxes present a serious threat for on-board electronics of spacecraft orbiting in geosynchronous orbit. This provides actuality of the problem of electron flux forecast. The population of energetic electrons grows after immersion of the Earth's magnetosphere into a high-speed stream of the solar wind. One of the main mechanisms of acceleration of magnetospheric electrons to relativistic energies assumed to be their wave-particle interaction with the ultra-low-frequency or very-low-frequency waves. Accordingly, the previously proposed prognostic methods were based on the connection of the outer radiation belt population with the speed of the solar wind and the activity of the low-frequency waves in the magnetosphere. In this paper, we propose to build a forecast based on a new kind of the multiple regressions model with sliding window of predictors. A set of predictors used in the successful multiple regressions model include parameters that reflect processes of replenishment of the outer radiation belt due to the acceleration of seed electrons as well as processes of the devastation of the electron flux in the geosynchronous region due to outward adiabatic transport and outward radial diffusion. To characterize these processes, we use the following set of parameters measured on the ground and in situ: the solar wind speed, density and dynamic pressure of the interplanetary plasma, the intensity of ultra-low-frequency oscillations in front of the magnetosphere and on the ground, the flux of seed electrons (of hundreds eV energy) at geosynchronous orbit, the actual values of the magnetic field at L=6.6, and interplanetary electric field. Coefficients in the model equation are derived from experimental data using the least-squares method. Test calculations using the proposed model have shown promising results.

Long-period geomagnetic pulsations during the SSC of July 14, 2012, are studied. The prenoon longitudinal sector (09:20–11:30) MLT, from the boundaries of which pulsations propagate azimuthally onto the dawn and dusk sides with an opposite polarization direction and increased amplitude, has been distinguished. The position of this sector relative to noon (a shift to the dawn side) depends on the front azimuthal inclination. It has been found that the polarization direction reverses in going from low (<30°) to middle/subauroral (≥50°) latitudes on the entire dayside. The geomagnetic pulsations mainly fluctuate near the f 1 = 2.9 and f 2 = 4.4 mHz frequencies. Fluctuations with frequency f 1, which coincide with the fluctuation frequency of the IMF х component, predominate at the polar cap latitudes (the open field line region) in the form of rapidly attenuating impulses and at low latitudes with a much smaller amplitude. Fluctuations with frequency f 2 are globally registered at all latitudes in the dayside sector below the magnetopause projection as a train of several fluctuations. It is assumed that fluctuations with frequency f 1 penetrate from the solar wind, and fluctuations with frequency f 2 are radial magnetopause oscillations.