Magnetospheric Storms Research Articles

Contribution of global Pc5 oscillations to magnetic disturbance during geomagnetic storms

The contribution of global magnetospheric oscillations to magnetic disturbance during magnetospheric storms is studied. The bases of magnetic data from the INTERMAGNET global network in combination with the interplanetary and intramagnetospheric measurements of the magnetic field and plasma and the sets of the Kp, Dst, and AE indices are used for this purpose. The most favorable conditions in the solar wind and magnetosphere for generation of global Pc5 have been revealed. The contribution of these oscillations to the variations in the magnetic disturbance level, characterized by the AE index, has been estimated. The findings confirm that magnetospheric MHD oscillations participate in the processes of energy income from the solar wind and energy dissipation in the magnetosphere.

Observations on the variability and screening effect of Sporadic-E

Sporadic-E is a problem in high latitude HF communications because of its irregular and as yet unpredictable behaviour. This paper characterises the change in E-layer critical frequency ( f o E) that occurs in the four hours following a storm sudden commencement (SSC) event which is a precursor to magnetospheric storms which adversely affect ionospheric communications. Following checks for any seasonal or solar activity dependency in the data, further analysis determines the occurrence of full blanketing (screening) Sporadic-E layer formation at high latitudes as seen on vertical ionosondes in Northern Finland (67° Latitude). An appropriate threshold value of f o E is proposed that could be used following the commencement of ionospheric storms, indicating that there is a high probability that F-layer screening will occur. As far as the authors are aware this is the first statistical analysis of the onset of Sporadic-E following SSC.

Intermittency of storms and substorms: is it related to the critical behaviour?

Abstract. Intermittency is one of the possible means of quantifying dynamics of fractal processes. In this paper, the analysis of the intermittency of magnetospheric storms and substorms is presented. The analysis allows for a classification of the processes in terms of the power-law scaling of the magnitude of deviations of the index values from the values at quiet times (normal state), and the relative timings of occurrences of such deviations. These are expressed in terms of the co-dimension and the Fano factor. The relationship between the two is related to the nature of the processes behind the observed storm and substorm dynamics. The results suggest that there is a similarity between the two, and therefore it is possible that there are common dynamical processes behind the storms and substorms. In particular, it appears that both of them behave consistently with what would be expected for critical systems, which is consistent with the conclusions of several previous works.

Comment on the paper “CAWSES November 7–8, 2004, Superstorm: Complex Solar and Interplanetary Features in the Post-Solar Maximum Phase,” B. T. Tsurutani, E. Echer, F. L. Guarnieri, and J. U. Kozyra, Geophys. Res. Lett. 35 (2008)

The solar sources of the magnetic storms of November 8 and 10, 2004, are analyzed. The preliminary results of such an analysis [Yermolaev et al., 2005] are critically compared with the results of the paper [Tsurutani et al., 2008], where solar flares were put in correspondence with these magnetic storms. The method for determining solar sources that cause powerful magnetospheric storms is analyzed. It has been indicated that an optimal approach consists in considering coronal mass ejections (CMEs) as storm sources and accompanying flares as additional information about the location of CME origination.

On the loss of relativistic electrons at geosynchronous altitude: Its dependence on magnetic configurations and external conditions

The present study statistically examines geosynchronous magnetic configurations and external conditions that characterize the loss of geosynchronous MeV electrons. The loss of MeV electrons often takes place during magnetospheric storms, but it also takes place without any clear storm activity. It is found that irrespective of storm activity, the day‐night asymmetry of the geosynchronous H (north‐south) magnetic component is pronounced during electron loss events. For the loss process, the magnitude, rather than the duration, of the magnetic distortion appears to be important, and its effective duration can be as short as ∼30 min. The solar wind dynamic pressure tends to be high and interplanetary magnetic field BZ tends to be southward during electron loss events. Under such external conditions the dayside magnetopause moves closer to Earth, and the day‐night magnetic asymmetry is enhanced. As a consequence the area of closed drift orbits shrinks. The magnetic field at the subsolar magnetopause, which is estimated from force balance with the solar wind dynamic pressure, is usually stronger than the nightside geosynchronous magnetic field during electron loss events. It is therefore suggested that geosynchronous MeV electrons on the night side are very often on open drift paths when geosynchronous MeV electrons are lost. Whereas the present result does not preclude the widely accepted idea that MeV electrons are lost to the atmosphere by wave‐particle interaction, it suggests that magnetopause shadowing is another plausible loss process of geosynchronous MeV electrons.

A long‐duration narrowband Pc5 pulsation

We report on a rare event of a narrowband ULF magnetospheric pulsation that is observed at geosynchronous orbit over five consecutive days in the recovery period of a magnetospheric storm, with frequencies ranging from 5 to 9 mHz. The pulsation displays distinctive localization, being observed over several hours of local time in the noon and postnoon sectors during successive passes of GOES‐8 and GOES‐9. Geotail, which is traversing the outer magnetosphere a couple of RE farther out from geosynchronous orbit at the time the pulsations are observed, shows no distinct narrowband fluctuation in the magnetic field, excluding oscillations in the solar wind as a possible source of the pulsations. On the ground, several of the IMAGE magnetometers observe pulsations with similar spectral characteristics. By performing a phase cross‐spectrogram analysis on measurements from adjacent and latitudinally aligned ground stations we estimate the azimuthal mode number m of the pulsation, which we find to range between 20 and 55. Phase difference calculations indicate an eastward phase propagation of these pulsations. Density measurements from LANL spacecraft at geosynchronous orbit show evidence of a plasmasphere refilling process that is slower than usual, possibly associated with the observed slow frequency decrease and the unusually long lasting of the pulsations.

Solar wind drivers of large geomagnetically induced currents during the solar cycle 23

In this paper we investigate the interplanetary drivers of the largest geomagnetically induced currents (GIC) during the solar cycle 23. Interplanetary coronal mass ejections (ICMEs) are the major causes of intense geomagnetic storms and large GIC. In particular, in this work we examine the effectiveness of different structures embedded in an ICME (namely sheath regions, ejecta, and boundary layers) in causing large GIC. It was found that when an ICME interacts with the Earth's magnetosphere the most intense GIC activity is likely to take place during the passage of the turbulent sheath region. The effectiveness of sheath regions in driving large GIC is possibly due to their capability to trigger substorms and to drive intense directly driven ionospheric activity. We also investigated the relationships between different solar wind parameters and the GIC amplitudes. The best correlation with the GIC amplitudes was found with the solar wind electric field and the epsilon parameter. Ejecta‐associated GIC seem to require an on‐going magnetospheric Dst storm while sheath regions and boundary layers can cause large GIC even when no activity is taking place in terms of Dst. Interestingly, four of the nine ejecta‐associated GIC took place during the recovery phases of a intense magnetic storm (but when Dst still was having storm time values below −50 nT).

New progress of Double Star-Cluster joint exploration and study

The magnetic reconnection of magnetosphere and the magnetospheric space storms (including magnetospheric substorm, magnetic storm, magnetospheric particle storm) has long been one of the most challenging subjects in the solar-terrestrial physics. The reconnection mechanism and global triggering process of the magnetospheric space storms are still unclear up to now. Based on the Double Star Program (DSP) and Cluster joint measurements, we have observed the solar wind density hole, the component magnetic field reconnection in the magnetopause, the structures of magnetic storm ring current, global and multi-scale driven and triggering processes of magnetospheric substorm. In this paper we will briefly introduce these results.

Derivation of a planetary ionospheric storm index

Abstract. The planetary ionospheric storm index, Wp, is deduced from the numerical global ionospheric GPS-IONEX maps of the vertical total electron content, TEC, for more than half a solar cycle, 1999–2008. The TEC values are extracted from the 600 grid points of the map at latitudes 60° N to 60° S with a step of 5° and longitudes 0° to 345° E with a step of 15° providing the data for 00:00 to 23:00 h of local time. The local effects of the solar radiant energy are filtered out by normalizing of the TEC in terms of the solar zenith angle χ at a particular time and the local noon value χ0. The degree of perturbation, DTEC, is computed as log of TEC relative to quiet reference median for 27 days prior to the day of observation. The W-index map is generated by segmentation of DTEC with the relevant thresholds specified earlier for foF2 so that 1 or −1 stands for the quiet state, 2 or −2 for the moderate disturbance, 3 or −3 for the moderate ionospheric storm, and 4 or −4 for intense ionospheric storm at each grid point of the map. The planetary ionospheric storm Wp index is obtained from the W-index map as a latitudinal average of the distance between maximum positive and minimum negative W-index weighted by the latitude/longitude extent of the extreme values on the map. The threshold Wp exceeding 4.0 index units and the peak value Wpmax≥6.0 specify the duration and the power of the planetary ionosphere-plasmasphere storm. It is shown that the occurrence of the Wp storms is growing with the phase of the solar cycle being twice as much as the number of the magnetospheric storms with Dst≤−100 nT and Ap≥100 nT.

Effect of auroral electrojets and solar wind parameters on variations in the intensity of low-latitude geomagnetic disturbances and Dst during the extremely large magnetic storm of November 20–21, 2003

The effect of auroral electrojets on the variations in the low-latitude geomagnetic disturbances and Dst during a strong magnetic storm of November 20–21, 2003, with Dst ≈ −472 nT has been studied based on the global magnetic observations. It has been indicated that the magnetospheric storm expansive phase with Δt ≈ 1–2 h results in positive low-latitude disturbances (ΔH) of the same duration and with an amplitude of ∼ 1–2 h results in positive low-latitude disturbances (ΔH) of the same duration and with an amplitude of ∼ 30–100 nT in the premidnight-dawn sector. A growth of negative low-latitude ΔH values and Dst is mainly caused by regular convection electrojets with Δt ≥ 10 h, the centers of which shift to latitudes of ∼ 50°–55° during the storm development. It has been established that the maximal low-latitude values of the field ΔH component at 1800–2400 MLT are observed when the auroral luminosity equatorward boundary shifts maximally southward during an increase in the negative values of the IMF B z component. It has been assumed that, during this storm, a magnetic field depression at low latitudes was mainly caused by an enhancement of the partially-ring current which closes through field-aligned currents into the ionosphere at the equatorward boundary of the auroral luminosity zone.

Cluster observations in the inner magnetosphere during the 18 April 2002 sawtooth event: Dipolarization and injection at r = 4.6 RE

The present study examines a sawtooth injection event that took place around 0800 UT on 18 April 2002 when the Cluster spacecraft were located in the inner magnetosphere in the premidnight sector. In association with this injection, Cluster, at a radial distance of 4.6 RE, observed that the local magnetic field became more dipolar and that both ion and electron fluxes increased without notable energy dispersion. These features were accompanied by intensifications of the equatorward component of a double‐oval structure and also by an enhancement of the ring‐current oxygen ENA flux. The event was also accompanied by large magnetic field (a few tens of nT) and electric field (a few tens of mV/m) fluctuations with characteristic timescales of a few tens of seconds. These observations strongly suggest that this sawtooth injection extended not only widely in local time but also deeply into the inner magnetosphere. Interestingly, Cluster repeatedly observed dipolarization‐like signatures afterward, which, however, were not associated with enhancements of local energetic ion flux or with geosynchronous dipolarization or injection signatures. Instead, these magnetic signatures were accompanied by oscillatory plasma motion in the radial direction with a characteristic timescale of about 10 min, which appears to be related to the westward propagation of a spatially periodic auroral structure. The associated azimuthal electric field component was well correlated with the time derivative of the north‐south magnetic field component, suggesting that the observed electric field is inductive. These findings suggest that electromagnetic processes far inside geosynchronous orbit play an important role in energization of energetic ions and auroral dynamics during magnetospheric storms.

Space weather explorer – The KuaFu mission

The KuaFu mission is designed to explore the physical processes that are responsible for space weather, complementing planned in situ and ground-based programs, and also to make an essential contribution to the space weather application. KuaFu encompasses three spacecraft. KuaFu-A will be located at the L1 libration point and have instruments to observe solar extreme ultraviolet (EUV) and far ultraviolet (FUV) emissions and white-light coronal mass ejections (CMEs), and to measure radio waves, the local plasma and magnetic field, and high-energy particles. KuaFu-B1 and KuaFu-B2 will be in elliptical polar orbits chosen to facilitate continuous (24 h per day 7 days per week) observation of the northern polar aurora oval and the inner magnetosphere. The KuaFu mission is designed to observe globally the complete chain of disturbances from the solar atmosphere to geospace, including solar flares, CMEs, interplanetary clouds, shock waves, and their geo-effects, with a particular focus on dramatic space weather events such as magnetospheric substorms and magnetic storms. The mission start is targeted for the next solar maximum with launch hoped for in 2012. The initial mission lifetime will be 3 years. The overall mission design, instrument complement, and incorporation of recent technologies will advance our understanding of the physical processes underlying space weather, solve several key outstanding questions including solar CME initiation, Earth magnetic storm and substorm mechanisms, and advance our understanding of multi-scale interactions in and system-level behavior of our Sun–Earth space plasma system.

Studying the ionosphere with the incoherent scatter radar during the magnetic storm of January 10, 1997

Specific features of the variations and structure of the ionosphere above northern Europe during the known magnetospheric storm of January 10, 1997, have been analyzed using the oblique-incidence backscatter (OIB) methods. The OIB equipment installed near St. Petersburg, Gor’kovskaya (AANII), represent a BIZON small radar, the data of which were compared with the CUTLASS radar data, GPS observations of TEC, and geophysical data of the Sweden, Finnish, and Russian high-latitude observatories. A local substorm that occurred from 1451 to 1655 UT has been studied in detail, and 52 OIB ionograms have been obtained. The types of reflections from the MIT polar wall and the narrow ionization trough have been identified.

Space weather drivers in the ACE era

We examine ACE observations of interplanetary disturbances and energetic particle activity for the period of solar maximum during solar cycle 23 and compare these measurements to the historical record as represented by the National Space Science Data Center Omnitape of near‐Earth observations. Magnetospheric response parameters, Dst and Kp, are similarly compared for the two epochs. We find that ACE observed an unexpectedly large number of the strongest transient events with the strength of magnetospheric drivers exceeding the historical record for the space flight era. This is not entirely true of the magnetospheric response, which demonstrates that the magnetospheric response is an integrated effect that is more subtle than examination of single hourly averages would indicate. For these and other reasons, we argue that satellites at L1 orbit, such as ACE, provide an excellent database for the study of magnetospheric storm drivers and their associated energetic particle populations from which space weather models may be refined. We also compare and contrast energetic particle measurements. While protons are a large space weather concern, heavy ions are also a radiation hazard for hardware in particular. We argue that heavy ion radiation predictions based on the measurements of protons are not reliable and that only by measuring the actual composition of the solar energetic particle population can we hope to understand and address the threat posed by these particles to machines and to obtain a more complete view of the radiation environment.

The ionosphere of Europe and North America before the magnetic storm of October 28, 2003

The X17 solar flare occurred on October 28, 2003, and was followed by the X10 flare on October 29. These flares caused very strong geomagnetic storms (Halloween storms). The aim of the present study is to compare the variations in two main ionospheric parameters (foF2 and hmF2) at two chains of ionosondes located in Europe and North America for the period October 23–28, 2003. This interval began immediately before the storm of October 28 and includes its commencement. Another task of the work is to detect ionospheric precursors of the storm or substorm expansion phase. An analysis is based on SPIDR data. The main results are as follows. The positive peak of δfoF2 (where δ is the difference between disturbed and quiet values) is observed several hours before the magnetic storm or substorm commencement. This peak can serve as a disturbance precursor. The amplitude of δfoF2 values varies from 20 to 100% of the foF2 values. The elements of similarity in the variations in the δfoF2 values at two chains are as follows: (a) the above δfoF2 peak is as a rule observed simultaneously at two chains before the disturbance; (b) the δfoF2 variations are similar at all midlatitude (or, correspondingly, high-latitude) ionosondes of the chain. The differences in the δfoF2 values are as follows: (a) the effect of the main phase and the phase of strong storm recovery at one chain differs from such an effect at another chain; (b) the manifestation of disturbances at high-latitude stations of the chain differ from the manifestations at midlatitude stations. The δhmF2 variations are approximately opposite to the δfoF2 variations, and the δhmF2 values lie in the interval 15–25% of the hmF2 values. The performed study is useful and significant in studying the problems of the space weather, especially in a short-term prediction of ionospheric disturbances caused by magnetospheric storms or substorms.

Asymmetric development of magnetospheric storms during magnetic clouds and sheath regions

This study examines how the asymmetry in the low‐latitude geomagnetic field evolves during sheath and magnetic cloud domains of interplanetary coronal mass ejections using the Dst, SYMH and ASYH indices. For all investigated storms the station that contributed most to Dst was located in the dusk sector while the smallest disturbance field was concentrated around dawn. We found that sheath region storms are associated with larger morning/afternoon asymmetry than magnetic cloud storms. For sheath storms the station in the dusk sector contributed almost four times as much to Dst as the station in the dawn sector. Furthermore, the disturbance field is strongly variable during sheath storms. The results of this study suggest that for magnetic cloud storms the asymmetry arises mainly from ions drifting on open trajectories whereas in a case of a sheath driven storm the sudden intensifications of the substorm associated current systems add significantly to the asymmetry.

자기폭풍 기간 동안의 월별 누적 오로라 제트전류 지수, Dst 지수 및 행성간 전기장 사이의 상관관계

자기폭풍 기간 중에는 서브스톰이 빈번히 발생한다. 그리고 서브스톰이 진행될 때 극지방에는 오로라 제트 전류가 발생하며, 이는 AU 및 AL 지수로 그 강도를 규정할 수 있다. 따라서 AU 및 AL 지수와 자기폭풍의 정도를 나타내는 Dst 지수와의 상관관계를 구해봄으로써 서브스톰이 자기폭풍의 형성에 어떻게 기여하는지 조사할 수 있다. 이를 위하여 월별 누적 AU 지수, 월별 누적 <TEX>$\mid{AL}\mid$</TEX> 지수 값을 구한 뒤, 월별 누적 <TEX>$\mid{Dst}\mid$</TEX> 지수와의 상관관계를 구하였다. 그 결과 월별 누적 <TEX>$\mid{AL}\mid$</TEX> 지수와 월별 누적 <TEX>$\mid{Dst}\mid$</TEX> 지수의 상관관계는 0.60으로 월별 누적 AU 지수와 월별 누적 <TEX>$\mid{Dst}\mid$</TEX> 지수의 상관관계 0.28보다 비교적 높게 나타났다. 이는 서브스톰이 자기폭풍의 발달에 기여하고 있음을 의미한다. 한편 IMF가 남쪽을 향할 때 자기권에는 강력한 대류가 형성되어 하전입자를 내부 자기권으로 가속시키므로 자기폭풍을 야기한다는 견해가 있다. 대류를 야기하는 행성간 전기장은 <TEX>$\bar{E}=-\var{V}$</TEX>(태양풍 속도) <TEX>$\times\bar{B}_Z$</TEX>(GSM에서 IMF의 Z축 성분)으로 주어지며, 이로부터 월별 누적 행성간 전기장과 월별 누적 Dst 지수 값을 비교해 봄으로써 행성간 전기장의 강화로 인한 자기권 대류가 자기폭풍 형성에 어느 정도 기여하는지를 조사할 수 있다. 여기서 Dst 지수는 태양풍에 의한 동압을 고려한 값이며, 월별 누적 행성간 전기장은 행성간 전기장이 양일 때와 음일때를 구분한 뒤 월별 누적 Dst 지수와의 상관관계를 알아보았다. 그 결과 행성간 전기장이 음의 값을 나타낼 때 구한 월별 누적 행성간 전기장과 월별 누적 Dst 지수와의 상관관계는 0.83이고, 양일 때 월별 누적 행성간 전기장과 월별 누적 Dst 지수와의 상관관계는 0.39로 나타났다. 이것은 IMF가 남쪽으로 향할 때 발생하는 자기권 대류의 강화 역시 자기폭풍의 발달에 중요한 역할을 하고 있음을 보여 준다. Magnetospheric substorms occur frequently during magnetic storms, suggesting that the two phenomena are closely associated. We can investigate the relation between magnetospheric substorms and magnetic storms by examining the correlation between AE and Dst indices. For this purpose, we calculated the monthly cumulative AU, <TEX>$\mid{AL}\mid$</TEX> and <TEX>$\mid{Dst}\mid$</TEX> indices. The correlation coefficient between the monthly cumulative <TEX>$\mid{AL}\mid$</TEX> and <TEX>$\mid{Dst}\mid$</TEX> index is found to be 0.60, while that between monthly cumulative AU and <TEX>$\mid{Dst}\mid$</TEX> index is 0.28. This result indicates that substorms seem to contribute to the development of magnetic storms. On the other hand, it has been reported that the interplanetary electric field associated with southward IMF intensifies the magnetospheric convection, which injects charged particles into the inner magnetosphere, thus developing the ring current. To evaluate the contribution of the interplanetary electric field to the development of the storm time ring current belt, we compared the monthly cumulative interplanetary electric field and the monthly cumulative Dst index. The correlation coefficient between the two cumulative indices is 0.83 for southward IMP and 0.39 for northward IMF. It indicates that magnetospheric convection induced by southward IMF is also important in developing magnetic storms. Therefore, both magnetospheric substorm and enhanced magnetospheric convection seem to contribute to the buildup of magnetic storm.

South Atlantic magnetic anomaly ionization: A review and a new focus on electrodynamic effects in the equatorial ionosphere

Satellite observations of enhanced energetic particle fluxes in the South Atlantic Magnetic Anomaly (SAMA) region have been supported by ground-based observations of enhanced ionization induced by particle precipitation in the ionosphere over this region. Past observations using a variety of instruments such as vertical sounding ionosondes, riometers and VLF receivers have provided evidences of the enhanced ionization due to energetic particle precipitation in the ionosphere over Brazil. The extra ionization at E-layer heights could produce enhanced ionospheric conductivity within and around the SAMA region. The energetic particle ionization source that is operative even under “quiet” conditions can undergo significant enhancements during magnetospheric storm disturbances, when the geographic region of enhanced ionospheric conductivity can extend to magnetic latitudes closer to the equator where the magnetic field line coupling of the E and F regions plays a key role in the electrodynamics of the equatorial ionosphere. Of particular interest are the sunset electrodynamic processes responsible for equatorial spread F/plasma bubble irregularity generation and related dynamics (zonal and vertical drifts, etc.). The SAMA represents a source of significant longitudinal variability in the global description of the equatorial spread F irregularity phenomenon. Recent results from digital ionosondes operated at Fortaleza and Cachoeira Paulista have provided evidence that enhanced ionization due to particle precipitation associated with magnetic disturbances, in the SAMA region, can indeed significantly influence the equatorial electrodynamic processes leading to plasma irregularity generation and dynamics. Disturbance magnetospheric electric fields that penetrate the equatorial latitudes during storm events seem to be intensified in the SAMA region based on ground-based and satellite-borne measurements. This paper will review our current understanding of the influence of SAMA on the equatorial electrodynamic processes from the perspective outlined above.

Magnetic Pulsations: Their Sources and Relation to Solar Wind and Geomagnetic Activity

Ultra low frequency (ULF) waves incident on the Earth are produced by processes in the magnetosphere and solar wind. These processes produce a wide variety of ULF hydromagnetic wave types that are classified on the ground as either Pi or Pc pulsations (irregular or continuous). Waves of different frequencies and polarizations originate in different regions of the magnetosphere. The location of the projections of these regions onto the Earth depends on the solar wind dynamic pressure and magnetic field. The occurrence of various waves also depends on conditions in the solar wind and in the magnetosphere. Changes in orientation of the interplanetary magnetic field or an increase in solar wind velocity can have dramatic effects on the type of waves seen at a particular location on the Earth. Similarly, the occurrence of a magnetospheric substorm or magnetic storm will affect which waves are seen. The magnetosphere is a resonant cavity and waveguide for waves that either originate within or propagate through the system. These cavities respond to broadband sources by resonating at discrete frequencies. These cavity modes couple to field line resonances that drive currents in the ionosphere. These currents reradiate the energy as electromagnetic waves that propagate to the ground. Because these ionospheric currents are localized in latitude there are very rapid variations in wave phase at the Earth’s surface. Thus it is almost never correct to assume that plane ULF waves are incident on the Earth from outer space. The properties of ULF waves seen at the ground contain information about the processes that generate them and the regions through which they have propagated. The properties also depend on the conductivity of the Earth underneath the observer. Information about the state of the solar wind and the magnetosphere distributed by the NOAA Space Disturbance Forecast Center can be used to help predict when certain types and frequencies of waves will be observed. The study of ULF waves is a very active field of space research and much has yet to be learned about the processes that generate these waves.

Stability of the magnetospheric plasma pressure distribution and magnetospheric storms

One of the main features of magnetospheric storms is the increase of the inner magnetospheric plasma pressure. Models of this increase take into account the transport and acceleration of the plasma sheet particles by the large-scale dawn–dusk electric field and particle injections by the induction fields of magnetospheric substorms. Upper limit of the increase of the inner magnetospheric plasma pressure is determined by the condition of the stability of the plasma pressure profile. The most dangerous instability in the regions of low plasma parameter is the interchange instability. The development of such kind of instability leads to the loss of plasma up to form the quasi-stable profile of the plasma pressure. Developed theoretical approach gives the possibility to explain the radial dependence of the storm time plasma pressure profile and the dependence of D st-variation on the most equatorial position of storm time auroral electrojets.