Development Of Magnetic Storm Research Articles

Studying auroral activity using the SME index at the magnetic storm main phase during CIR and ICME events

In this paper, we examine the relationship of the SME index with magnetic storm characteristics and interplanetary medium parameters during the main phase of magnetic storms caused by CIR and ICME events. Over the period 1990–2017, 107 magnetic storms driven by (64) CIR and (43) ICME events have been selected. In contrast to AE and Kp, a stronger correlation is shown to exist between the average SME index (SMEaver) and interplanetary medium parameters during the magnetic storm main phase. Close correlation coefficients between SMEaver and the SW electric field (southward IMF Bz) have been obtained for CIR and ICME events. SMEaver has been found to increase with the rate of magnetic storm development and |Dstmin|. For CIR and ICME events, no difference has been revealed between SMEaver and |Dstmin| in linear regression equations.

Исследование авроральной активности по данным SME-индекса на главных фазах магнитных бурь во время CIR- и ICME-событий

. In this paper, we examine the relationship of the SME index with magnetic storm characteristics and interplanetary medium parameters during the main phase of magnetic storms caused by CIR and ICME events. Over the period 1990–2017, 107 magnetic storms driven by (64) CIR and (43) ICME events have been selected. In contrast to AE and Kp, a stronger correlation is shown to exist between the average SME index (SMEaver) and interplanetary medium parameters during the magnetic storm main phase. Close correlation coefficients between SMEaver and the SW electric field (southward IMF Bz) have been obtained for CIR and ICME events. SMEaver has been found to increase with the rate of magnetic storm development and |Dstmin|. For CIR and ICME events, no difference has been revealed between SMEaver and |Dstmin| in linear regression equations.

Temporal evolution analysis of storm-enhanced density during an intense magnetic storm on March 2015

An intense Storm Enhancement Density (SED) event with the magnetic storm occurred on 17–24 March 2015 has been investigated. The morphological character of the SED during different phase of the magnetic storm is examined and compared with the non-storm time. Three intensity indexes, i.e., “general” SED index, “heavy” SED index and “severe” SED index, are defined to represent the intensity of SED respectively represented by the numbers of the ionospheric total electron content (TEC) grids with TEC > 60 TECu, TEC > 80 TECu and TEC > 100 TECu. The temporal evolution of the SED intensity indexes during a time span covering the non-storm time and the magnetic storm time have also been investigated. The SED exhibits a shape with two parallel slender troughs in the middle and low latitudes during the non-storm time and then gradually develops into an ellipse structure as the development of magnetic storm. The intensity of SED and the fluctuation of the TEC evolution are generally corresponding to the fluctuation of Dst index. The analyzing results enrich our understanding of the temporal and spatial evolution of the ionospheric SED.

Dynamics and spatio-temporal distribution of geomagnetic disturbances during periods of increased solar activity and magnetic storms

A detailed spatio-temporal analysis of magnetic data was performed during the periods of magnetic storms on October 02, 2013 and September 27, 2019 based on measurements of the station network. In this work, we used a method developed by us for the analysis of magnetic data, based on the use of wavelet transform and adaptive thresholds. The method allows us to identify short-period field disturbances and estimate their intensity from the data of the H-component of the geomagnetic field. The features of the occurrence and propagation of geomagnetic disturbances in the auroral zone and at meridionally located stations have been studied. Dynamic spectra of disturbances of different intensity and duration are obtained. The paper confirms the possibility of occurrence of short-period weak geomagnetic disturbances at stations from high latitudes to the equator, preceding magnetic storms and correlating with fluctuations of the southern Bz-component of the interplanetary magnetic field and increases in the auroral indices of geomagnetic activity. Cross-correlation dependences of the intensity of geomagnetic disturbances on the parameters of the interplanetary medium during magnetic storms were obtained from the data of the network of magnetic stations. A statistically significant influence of the magnitude of the scope of the Bz-component of the IMF and the speed of the solar wind on the development of magnetic storms during the initial and main phases of magnetic storms was revealed.

PC index as a proxy of the solar wind energy that entered into the magnetosphere: 3. Development of magnetic storms

Relationships between the 30-min smoothed PC and SymH indices in course of 430 magnetic storms observed in period of 1998–2015 have been examined. The storms were classified, by features of the PC evolution, as classic, pulsed and composite magnetic storms. It is shown these storm types are related, correspondingly, to such solar drivers as Interplanetary Coronal Mass Ejections (ICME), Stream Interaction Regions (SIR), and their joint action. Results of the statistical analysis demonstrate that depression of geomagnetic field (“Dst variation”) starts to develop as soon as PC index steadily excess the threshold level ∼1.5 mV/m, like to case of magnetic substorms. SymH index in course of magnetic storms (during 48 h preceding and succeeding the maximal depression of geomagnetic field) generally follows the time evolution of the PC index with typical delay time of ΔT ∼ 1 ± 0.5 h. The storm intensity (SymHMIN) is linearly related to maximal value of the foregoing PC index (PCMAX) observed ∼0.5÷2 h before the moment of maximal depression. The conclusion is made that the PC index can be successfully used for nowcasting the magnetic storm development.

Methods of analysis of geomagnetic field variations and cosmic ray data

In the present paper, we propose a wavelet-based method of describing variations in the Earth’s magnetic field, such as the horizontal component of the geomagnetic field, in addition to methods for evaluating changes in the energy characteristics of the field and for isolating the periods of increased geomagnetic activity. Based on a combination of multiresolution wavelet decompositions with neural networks, we propose a method of approximation of the cosmic ray time course and the allocation of anomalous variations (Forbush effects) that occur during periods of high solar activity. During the realization of the method, an algorithm was created for selecting the level of the wavelet decomposition and adaptive construction of the neural network. By using the proposed methods, we performed a joint analysis of the geomagnetic field and cosmic rays during periods of strong magnetic storms. The strongest geomagnetic field perturbations were observed in periods of abnormal changes in cosmic ray level. Assessment of the intensity of geomagnetic disturbances on the eve of and during magnetic storm development allowed us to highlight local increases in intensity of the geomagnetic field occurring at different frequency ranges prior to the development of the storm’s main phase. Implementation of the proposed method with theoretical tools in combination with other methods will improve the estimation accuracy of the geomagnetic field state during space weather forecasting.

Variations in the critical frequency of the ionospheric F-region during magnetic storms in 2008–2012 at auroral latitudes

Fifty-one magnetic storms occurred during the last solar half-cycle of transition from the epoch minimum to the epoch maximum are considered. Ionospheric (foF2) and magnetic (X component) data from Sodankyla observatory, Finland, were used for the analysis, as well as values of the ΣKp indices of magnetic activity. The dependence of variations in the critical frequency foF2 was studied before, during, and after each storm. It has been revealed that a major effect (ME) takes place for all of the storms analyzed. It consists in the following: the first maximum in foF2 values occurs several days before the onset of the active phase of a storm, then foF2 attains its minimum during the active phase, and the second maximum occurred after the active phase. Five principals, the most frequent types of variation in foF2 during a storm, have been revealed. However, special cases (30%) in which an ME exists but shifts rightward several days along the time axis are observable. Ionospheric “memory” (inertia) from 8–9 h to 2 days has been revealed. It has been ascertained that the occurrence of the first ME maximum can be considered a magnetic storm precursor. Such a precursor potentially can be used for forecasting the beginning of magnetic storm development, which is important for space weather problems.

The Earth’s magnetosphere response to interplanetary medium conditions on January 21–22, 2005 and on December 14–15, 2006

The Earth’s magnetosphere response to interplanetary medium conditions on January 21–22, 2005 and on December 14–15, 2006 has been studied. The analysis of solar wind parameters measured by ACE spacecraft, of geomagnetic indices variations, of geomagnetic field measured by GOES 11, 12 satellites, and of energetic particle fluxes measured by POES 15, 16, 17 satellites was performed together with magnetospheric modeling based in terms of A2000 paraboloid model. We found the similar dynamics of three particle populations (trapped, quasi-trapped, and precipitating) during storms of different intensities developed under different external conditions: the maximal values of particle fluxes and the latitudinal positions of the isotropic boundaries were approximately the same. The main sources caused RC build-up have been determined for both magnetic storms. Global magnetospheric convection controlled by IMF and substorm activity driven magnetic storm on December 14–15, 2006. Extreme solar wind pressure pulse was mainly responsible for RC particle injection and unusual January 21, 2005 magnetic storm development under northward IMF during the main phase.

New aspects in plasmaspheric ion temperature variations from INTERBALL 2 and MAGION 5 measurements

INTERBALL 2 (1996) and MAGION 5 (1999–2001) cold plasma measurements provided the possibility to deduce new aspects of ion temperature distributions in the Earth's plasmasphere during magnetically quiet and moderately disturbed times. Proton temperatures in the plasmasphere were compared along the magnetic field lines to electron and ion temperatures measured by DMSP satellites in the upper (∼840 km) ionosphere. On the nightside for 1.4< L<2.8, plasmaspheric temperatures were found to be quite close to ionospheric electron temperatures. At L=2.5–2.8, ion temperatures in the plasmasphere were close to electron temperatures in the upper ionosphere everywhere except for the noon-to-dusk MLT sector. At higher L ( L>3), the plasmasphere-to-ionosphere temperature ratio was greater than 1, and there was also an increase in the 12–20 MLT sector. Apparently there is a heating source at high L that is strongest in the noon-to-dusk MLT sector. It was revealed that during moderate magnetic storm development, nighttime ion temperature was depressed in the storm main phase, but exceeded quiet time values in the storm recovery phase. Possible reasons of such temperature behavior are briefly discussed.

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.

Magnetic storm cessation during sustained northward IMF

Times of sustained strong northward IMF can interrupt the magnetic storm development and lead to lower levels of geomagnetic activity for many hours. During 1997–2000 we have found two events of this kind observed on November 8, 1998 and October 13, 2000. In both cases, the storms started as usual after arrival of ejecta with a southward IMF component from the Sun to the Earth, but ceased after several hours due to the onset of sustained northward IMF leading to the faster recovery process. After the passage of this so-called positive domain, the storm development started again. The heliospheric magnetic field intensity remained enhanced and nearly constant. The solar origins of the geomagnetic storm interruptions have been investigated. Tentatively they may be related to strong nonlinear Alfvйn type solitary waves excited by non-stationary coronal current variations with a characteristic time-scale of about a day.

Correlation between particle injections observed at geosynchronous orbit and the Dst index during geomagnetic storms

To understand the relationship between geomagnetic storms and substorms, we examine the correlation between dispersionless proton injections observed by geosynchronous satellites and the Dst index during geomagnetic storms. It is not possible to deduce the amount of the total energy injection into the inner magnetosphere from measurements only by one or two satellites. Nonetheless, we may obtain a quantity that is proportional to the true injection rate during magnetic storms by estimating the flux increase expressed in terms of the flux ratio (fmax/fpre_ave) and the number of injections, where fpre_ave and fmax represent the average flux of prestorm level and onset level, respectively. Thus we propose to introduce a parameter, “total energy injection parameter” (TEIP), defined by the product of the flux ratio and the number of injections, as an indicator of the energy injected into the inner magnetosphere. Several interesting points are noted, particularly for the main phase of storms. First, the number of particle injections tends to increase with the storm size. Second, the flux ratio (fmax/fpre_ave) also tends to increase with the storm size. Third, there is also a significantly high correlation between TEIP and Dstmin. In particular, the correlation coefficients are very high, above 0.85, for those channels of energy, 50–400 keV, which represent the typical energy range of ring current particles. These results indicate that the substorm expansion activity is higher during the main phase than the recovery phase, suggesting that the substorm expansion activity seems to be closely associated with the development of magnetic storms.

Study of the&amp;lt;tex&amp;gt;$rm Dst-AL$&amp;lt;/tex&amp;gt;Correlation During Geospace Magnetic Storms

A dispute on the role of substorms in geospace magnetic storm development has emerged during the last decade; the scientific community has not yet reached a definite conclusion. This paper attempts to clarify, to the extent possible with statistical methods, if there is any causal relationship between the energy dissipation during storms and during substorms. To assess this aspect of the storm-substorm relationship, we performed an investigation using the geomagnetic indexes SYM-H and AL for a large number of magnetic storms. We selected a group of 53 magnetic storms with SYM-H peak values in the range between -50 nT and -350 nT. We then calculated the integrals of the SYM-H and AL squares, to represent magnetic energy dissipation for storms and substorms respectively. These integrals exhibit a strong linear correlation, with a correlation index of r=0.928. The result implies a strong coupling between storm and substorm energy dissipation.

자기폭풍 기간 중 정지궤도 공간에서의 입자 유입률과 Dst 지수 사이의 상관관계

자기폭풍(magnetic storm)과 서브스톰(substorm)의 인과관계를 규명하기 위하여 서브스톰 확장기 활동(substorm expansive activity)의 전형적인 지시자로 알려진 정지궤도 위성에서 관측된 양성자 플럭스(proton flux)의 무분산 입자유입률(dispersionless particle injection rate)과 Dst 지수와의 상관관계를 조사하였다. 본 연구에 이용된 자기폭풍은 1996년에서 2000년까지 5년 동안에 일어난 것으로 자기폭풍 기간 중 Dst의 최소값인 <TEX>$Dst_{min}$</TEX>의 크기에 따라 대규모(<TEX>$-200nT{$\leq$}Dst_{min}{$\leq$}-100nT$</TEX>), 중규모(<TEX>$-100nT{\leq}Dst_{min}{\leq}-50nT$</TEX>), 소규모 자기폭풍(<TEX>$-50nT{\leq}Dst_{min}{\leq}-30nT$</TEX>)의 3단계로 구분하였다. 양성자 플럭스는 LANL의 정지궤도 위성에서 관측된 자료 중에서 주로 환전류(ring current)를 구성하는 입자의 에너지에 해당하는 50keV에서 670keV 범위의 6개 에너지 채널의 자료를 이용하였다. 그리고 입자유입은 자정 부근에서 주로 일어나므로 18:00~04:00MLT구간에서 관측된 자료만을 이용하였다. 한편 내부 자기권으로 유입되는 입자에너지를 추정하기 위하여 양성자 플럭스 비(<TEX>$f_{max}/f_{ave}$</TEX>)를 조사하였다. 여기서, <TEX>$f_{ave}$</TEX> 및 <TEX>$f_{max}$</TEX>는 각각 입자유입이 일어나기 전 후의 양성자 플럭스의 양을 나타낸다. 한편 자기폭풍 기간 동안에 1 ~ 2개의 인공위성 관측으로부터 내부 자기권으로 유입되는 총 에너지량을 추정하는 것이 불가능하다는 것이 알려졌다. 그러나 총 에너지 유입량은 적어도 플럭스 비와 유입횟수에 비례할 것이다. 따라서 내부 자기권으로 유입되는 에너지의 양을 간접적으로 추정하기 위해서 이들의 곱으로 정의되는 총 에너지 유입률 지수(total energy injection parameter, TEIP)를 제안하였다. 특히 서브스톰이 자기폭풍의 발달에 기여하는 정도를 알기 위하여 자기폭풍을 두 구간, 즉 주상(main phase)과 회복기(recovery phase)로 나누어 조사하였다. 양성자의 무분산 유입자료와 자기폭풍 기간 중 Dst<TEX>$_{min}$</TEX> 값을 비교해 본 결과 다음과 같은 특성이 확인되었다. 첫째, 주상기간 중 입자들의 평균 유입횟수는 자기폭풍의 크기에 비례하여 증가하는 경향을 나타내며 유입휫수와 <TEX>$Dst_{min}$</TEX> 사이에는 높은 상관관계(0.83)가 있었다. 둘째, 주상기간 중 자기폭풍의 크기가 클수록 플럭스 비 (<TEX>$f_{max}/f_{ave}$</TEX>는 대체로 증가하는 경향을 나타냈다. 그리고 75~113keV 에너지 채널에서의 <TEX>$Dst_{min}$</TEX> 값과 플럭스 비의 상관계수는 0.74로서 가장 높았으며 나머지 에너지 채널 역시 비교적 높은 상관관계를 나타냈다. 셋째, 주상기간 중 총 에너지 유입률 지수와 <TEX>$Dst_{min}$</TEX> 사이에 높은 상관관계가 확인되었다. 특히 환전류를 구성하는 주요 입자의 에너지 영역(75~l13keV)에서 가장 높은(0.80) 상관계수를 기록했다. 넷째, 회복기 중에 일어나는 입자들의 유입은 자기폭풍의 지속시간을 연장시키는 경향을 보이며 큰 자기폭풍일수록 현저했다. 주상에서 관측된 이러한 특성은 서브스톰 확장기 활동이 자기폭풍의 발달과 밀접한 관계가 있음을 시사한다. To examine the causal relationship between geomagnetic storm and substorm, we investigate the correlation between dispersionless particle injection rate of proton flux observed from geosynchronous satellites, which is known to be a typical indicator of the substorm expansion activity, and Dst index during magnetic storms. We utilize geomagnetic storms occurred during the period of 1996 ~ 2000 and categorize them into three classes in terms of the minimum value of the Dst index (<TEX>$Dst_{min}$</TEX>); intense (<TEX>$-200nT{$\leq$}Dst_{min}{$\leq$}-100nT$</TEX>), moderate(<TEX>$-100nT{\leq}Dst_{min}{\leq}-50nT$</TEX>), and small (<TEX>$-50nT{\leq}Dst_{min}{\leq}-30nT$</TEX>) -30nT)storms. We use the proton flux of the energy range from 50 keV to 670 keV, the major constituents of the ring current particles, observed from the LANL geosynchronous satellites located within the local time sector from 18:00 MLT to 04:00 MLT. We also examine the flux ratio (<TEX>$f_{max}/f_{ave}$</TEX>) to estimate particle energy injection rate into the inner magnetosphere, with <TEX>$f_{ave}$</TEX> and <TEX>$f_{max}$</TEX> being the flux levels during quiet and onset levels, respectively. The total energy injection rate into the inner magnetosphere can not be estimated from particle measurements by one or two satellites. However, the total energy injection rate should be at least proportional to the flux ratio and the injection frequency. Thus we propose a quantity, “total energy injection parameter (TEIP)”, defined by the product of the flux ratio and the injection frequency as an indicator of the injected energy into the inner magnetosphere. To investigate the phase dependence of the substorm contribution to the development of magnetic storm, we examine the correlations during the two intervals, main and recovery phase of storm separately. Several interesting tendencies are noted particularly during the main phase of storm. First, the average particle injection frequency tends to increase with the storm size with the correlation coefficient being 0.83. Second, the flux ratio (<TEX>$f_{max}/f_{ave}$</TEX>) tends to be higher during large storms. The correlation coefficient between <TEX>$Dst_{min}$</TEX> and the flux ratio is generally high, for example, 0.74 for the 75~113 keV energy channel. Third, it is also worth mentioning that there is a high correlation between the TEIP and <TEX>$Dst_{min}$</TEX> with the highest coefficient (0.80) being recorded for the energy channel of 75~113 keV, the typical particle energies of the ring current belt. Fourth, the particle injection during the recovery phase tends to make the storms longer. It is particularly the case for intense storms. These characteristics observed during the main phase of the magnetic storm indicate that substorm expansion activity is closely associated with the development of mangetic storm.

Change of the plasma sheet ion composition during magnetic storm development observed by the Geotail spacecraft

The present study aims to investigate how and where ions of ionospheric origin are accelerated to the ring current energy (a few tens to a few hundreds of keV) and how they are supplied to the ring current. We examined the plasma sheet ion composition during magnetic storm development, using energetic (9–210 keV) ion flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on board the Geotail spacecraft. We selected two magnetic storms, that is, the 16–17 May 2000 storm and the 25 December 1998 storm, for which the energy density ratios of O+/H+ and He+/H+ in the plasma sheet were calculated from the EPIC/STICS data. These magnetic storms had a minimum of the SYM‐H index (the 1‐min Dst index) less than −50 nT and a duration of the main phase shorter than 6 hours. We obtained the following results: (1) Both the O+/H+ and He+/H+ energy density ratios were anticorrelated with the SYM‐H index (∣r∣ = 0.73–0.88); (2) The O+/H+ energy density ratio was rather constant at ∼0.1 before storms, but reached 0.3–1.0 at the storm maximum; and (3) The He+/H+ energy density ratio increased from 0.01–0.02 before storms to 0.04–0.1 at the storm maximum. These ion composition changes are comparable to those in the ring current, which have been reported by previous studies, indicating that ions of ionospheric origin are possibly convected to the ring current via the plasma sheet. A close inspection of ion energy spectra revealed that the observed ion composition changes can be attributed to the mass‐dependent acceleration of ions by the dawn‐to‐dusk electric field in the current sheet and the additional transport of ionospheric ions into the plasma sheet.

Magnetic Storm Development and Its Quantification for Aims of Modeling.

Using a large sample of storms of different intensity the ring current magnetic field development is followed in terms of varying interplanetary conditions. It is shown that although the storm depression field is associated with energy input into the magnetosphere, the sustained IEF intensity <-5 mV/m as a condition for the occurrence of intense storms appears not to be of general validity. Quantification of the magnetic storm development indicates the role of the actual state of the magnetosphere in the development of its response on interplanetary medium forcing. Ring current energization is considered for some storm models represented by pairs of energy injection rate and time decay parameter. A number of models are juxtaposed quantitatively. The adequacy of modeling of storm profiles and the significance of decay parameter in the magnetic storm development is discussed from the viewpoint of consistency of energy injection rate and energy decay rate and also with regard to an adequate distribution of dissipated energy within the ring current region and auroral ionosphere.

What does the magnetic storm development depend on?

Adiabatic drift model applied to the magnetic storm development simulation reveals the significance of initial energy, initial pitch angle and the site of ions injection for the intensity, growth time and growth rate of a storm produced by two ion species—H + and O +. The most severe storms are caused by the ring current intensified by low initial pitch angle ions injected at low radial distance in the postmidnight local time region.

Low‐energy plasma in the Earth's magnetosphere

The low‐energy plasma fluxes in the earth's magnetosphere, with energies from thermal up to ∼50 kev, are an important factor in determining many of the essential properties of the magnetosphere. Currents produced by the motion of these charged particles play a key role in the development of magnetic storms and in the production of auroras and the geomagnetic tail. This paper will review the experimental observations of this plasma obtained over the last decade in different regions of the magnetosphere, considered in order of increasing distance from the earth. The similarity of results from measurements of the ion and electron components of the earth's thermal plasma envelope and the dependence of the altitude of the boundary of this envelope (the ‘plasmapause’) on geomagnetic activity are described. Within the radiation belts there exists a low‐energy plasma component that is much more variable than the energetic component; the variation of low‐energy plasma fluxes in the outer belt seems to be the main cause of geomagnetic storms. The radiation belts are always surrounded by low‐energy plasma fluxes; on the night side these fluxes become a part of the thick plasma layer within which is imbedded the neutral sheet of the geomagnetic tail. Experimental data on low‐energy plasma at geocentric distances &gt;2 RE and geomagnetic latitudes &gt;45° are very scarce; this region needs intensive investigation.