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Solar wind — a plasma stream flowing out of the solar corona — is interesting both as a carrier of solar activity and as an example of a collisionless plasma. We present the main results of Russian studies in recent years. The original MHD model allows interpreting the bifurcation of the heliospheric current sheet during maximum activity years as occurring due to the quadrupole component of the heliomagnetic field. On a scale of the order of millions of kilometers, the solar wind consists of transient solar formations. On these scales, one of the basic geomagnetic forecast problems has been solved: it was shown that the interplanetary magnetic field can be assumed stable at times of about three hours. At small scales (hundreds to thousands of kilometers), local structures are formed that can be regarded, both individually and statistically, as turbulent cascades.

Observations of Earth's bow shock during high-β (ratio of thermal to magnetic pressure) solar wind streams are rare. However, such shocks are ubiquitous in astrophysical plasmas. Typical solar wind parameters related to high β (here β>10) are as follows: low speed, high density, and a very low interplanetary magnetic field of 1–2 nT. These conditions are usually quite transient and need to be verified immediately upstream of the observed shock crossings. In this report, three characteristic crossings by the Cluster project (from the 22 found) are studied using multipoint analysis, allowing us to determine spatial scales. The main magnetic field and density spatial scale of about a couple of hundred of kilometers generally corresponds to the increased proton convective gyroradius. Observed magnetic variations are different from those for supercritical shocks, with β∼1. Dominant magnetic variations in the shock transition have amplitudes much larger than the background field and have a frequency of ∼ 0.3–0.5 Hz (in some events – 1–2 Hz). The wave polarization has no stable phase and is closer to linear, which complicates the determination of the wave propagation direction. Spatial scales (wavelengths) of variations are within several tens to a couple of hundred of kilometers.

We review current status of Russian space research in the fields of planetary and Earth science. In the recent years planetary experiments of Space Research Institute are flown onboard six European and US missions at Mars, Venus, Moon and Mercury. In addition, two instruments are onboard Exomars-2016, a joint project with ESA. The second Exomars launch is expected in 2020. Extensive Russian lunar program includes launches of two landers and one orbiter in 2021,2024,2025, also with ESA cooperation. In more distant future the new Venus program is shaping up. Besides that Space Research Institute conducts extensive Earth observation research, mostly targeted at natural systems monitoring.

Electron dynamics and acceleration in an electromagnetic field configuration modeling the current sheet configuration of the Earth’s magnetotail region is investigated. A focus is made on the role of the dawn−dusk magnetic field component By in the convection electron heating by an electric field Ey. For numerical integration of a large number of test particle trajectories over long time intervals, the equations of motion written in the guiding center approximation are used. It is shown that the presence of a By ≠ 0 magnetic field significantly changes the electron heating and allows electrons with small pitch angles to gain energy much more efficiently than the equatorial electrons. As a result, the convection heating in the current sheet with By ≠ 0 leads to the formation of an accelerated anisotropic population of particles with energies higher than a few hundred electronvolts. The obtained results and spacecraft observations in the Earth’s magnetotail are compared, and possible limitations in the proposed model approaches are discussed.

This work is devoted to studying the processes of the acceleration of plasma particles in thin current sheets that appear during magnetospheric substorms in the Earth’s magnetosphere tail. A numerical model of magnetic dipolarization accompanied by plasma turbulence has been constructed and studied. The model allows one to investigate the particle acceleration due to the action of three principal mechanisms: (1) plasma turbulence; (2) magnetic dipolarization; (3) their simultaneous action. For the given velocity kappa-distributions, we obtained energy spectra of three types of accelerated particles, i.e., protons p+, ions of oxygen O+, and electrons e–. It has been shown that the combined mechanism of dipolarization with turbulence (3) makes the largest contribution to the increase in the energy of protons and heavy ions as compared with a separate action of each of mechanisms (1) and (2); in this case, electrons accelerate less. The consideration of the joint action of acceleration mechanisms (1) and (2) can explain the apparition of particles with energies on the order of magnitude equal to hundreds keV in the Earth’s magnetosphere tail.

Earth's bow shock in high β (ratio of thermal to magnetic pressure) solar wind environment is relatively rare phenomenon. However such a plasma object may be of interest for astrophysics. We survey statistics of high-β (β > 10) shock observations by near-Earth spacecraft since 1995. Typical solar wind parameters related with high β are: low speed, high density and very low IMF 1–2 nT. These conditions are usually quite transient and need to be verified immediately upstream of the observed shock crossings. About a hundred crossings were initially identified mostly with quazi-perpendicular geometry and high Mach number. In this report 22 Cluster project crossings are studied with spacecraft separation within 30–200 km. Observed shock front structure is different from that for quaziperpendicular supercritical shocks with β = 1. There is no well defined ramp. Dominating magnetic waves have frequency 0.1–0.5 Hz (in some events 1–2 Hz). Polarization has no stable phase and is closer to linear. In some cases it is possible to determine wavelength at 0.1–0.5 Hz of the order of 200–900 km.

Thin current sheets having kinetic scales are an important plasma structure, where the magnetic energy dissipation and charged particle acceleration are the most effective. It is believed that such current sheets are self-consistently formed by the specific nonadiabatic dynamics of charged particles and play a critical role in many space plasma and astrophysical objects. Current sheets in the near-Earth plasma environment, e.g., the magnetotail current sheet, are readily available for in-situ investigations. The dedicated multi-spacecraft Cluster mission have revealed basic properties of this current sheet, which are presented in this review: typical spatial profiles of magnetic field and current density, distributions of plasma temperature and density, role of heavy ions and electron currents, etc. Being important for the Earth magnetosphere physics, the new knowledge also could provide the basis for advancement in general plasma physics as well as in plasma astrophysics.

In this review we discuss the formation of plasma structures in hot plasmas with large β. We use spacecraft observations of magnetic field fluctuations in the Earth magnetotail to reveal the main multiscale plasma properties. Fourier spectra of magnetic field fluctuations observed by various spacecraft in the different domains of the magnetotail at quiet or moderately disturbed times demonstrated a number of practically universal features: (1) the presence of two kinks at low (∼5×10−2 Hz) and high (∼5×10−1 Hz) frequencies, (2) in the frequency interval between the kinks the power law shape with an index ∼2.5, and (3) the significant intensification of fluctuations with the increase of plasma flow velocities. To describe these spectra we consider properties of a principal structure supporting the equilibrium of a hot plasma configuration—the magnetotail current sheet. The observed spatial scales of current sheets are often very small and almost reach the ion Larmor radius. Convection of such mesoscale plasma structures by plasma flows can be responsible for the formation of a certain part of the spectrum of magnetic field fluctuations. Lower- and higher- frequency domains in Fourier spectra can be generated respectively by large-scale MHD oscillations of current sheets and by kinetic small-scale instabilities excited by strong local magnetic field gradients existing in active current sheets.

[1] We developed a self-consistent kinetic model of thin current sheets (TCS), taking into account the inhomogeneity of TCS parameters in the antisunward direction. We show that the charged particle dynamics depending on the magnetic field distribution in the downtail direction completely determines the magnetotail equilibrium structure. We demonstrate that transient ions as well as electrons are the main current carriers in this system, but the first ones support mostly the background (1-D) structure of the current sheet. The influence of electrons and quasi-trapped ions is found to vary depending upon downtail distance along the sheet. Assuming the conservation of the so-called quasi-adiabatic invariant, we show that quasi-trapped particles are distributed along the current sheet in such a way that they concentrate in the region with large values of normal magnetic field component. As a result quasi-trapped ions can dominate near the earthward edge of TCS. In contrast, the electron current becomes stronger in the TCS tailward region where the normal magnetic field component becomes weaker, and field line curvature drifts are enhanced. Our quasi-adiabatic model predicts that thin current sheets in the Earth's magnetotail should have weakly 2-D configuration which, similar to its 1-D analog considered earlier, conserves the multiscale “matreshka” structure with multiple embedded layers.

[1] Using 25 observations of damped oscillatory flow behavior in the near-Earth plasma sheet by the five THEMIS probes during the 2008–2009 magnetotail seasons, we derive the parameters of an oscillating thin filament, such as its oscillation period, damping factor, and entropy. To facilitate comparison with theory, we use measured pressures and magnetic fields with an empirical model to achieve a quantitative representation of the overall structure of the plasma sheet during each event. Because the observed oscillation period of the filament agrees with the oscillation period predicted by Wolf et al. (2012), the observed damped oscillatory flow behavior in the near-Earth plasma sheet is most likely caused by oscillatory braking of the filament.

The review is devoted to plasma structures with an extremely small transverse size, namely, thin current sheets that have been discovered and investigated by spacecraft observations in the Earth’s magnetotail in the last few decades. The formation of current sheets is attributed to complicated dynamic processes occurring in a collisionless space plasma during geomagnetic perturbations and near the magnetic reconnection regions. The models that describe thin current structures in the Earth’s magnetotail are reviewed. They are based on the assumption of the quasi-adiabatic ion dynamics in a relatively weak magnetic field of the magnetotail neutral sheet, where the ions can become unmagnetized. It is shown that the ion distribution can be represented as a function of the integrals of particle motion—the total energy and quasi-adiabatic invariant. Various modifications of the initial equilibrium are considered that are obtained with allowance for the currents of magnetized electrons, the contribution of oxygen ions, the asymmetry of plasma sources, and the effects related to the non-Maxwellian particle distributions. The theoretical results are compared with the observational data from the Cluster spacecraft mission. Various plasma instabilities developing in thin current sheets are investigated. The evolution of the tearing mode is analyzed, and the parameter range in which the mode can grow are determined. The paradox of complete stabilization of the tearing mode in current sheets with a nonzero normal magnetic field component is thereby resolved based on the quasi-adiabatic model. It is shown that, over a wide range of current sheet parameters and the propagation directions of large-scale unstable waves, various modified drift instabilities—kink and sausage modes—can develop in the system. Based on the concept of a turbulent electromagnetic field excited as a result of the development and saturation of unstable waves, a mechanism for charged particle acceleration in turbulent current sheets is proposed and the energy spectra of the accelerated particles are obtained.

Kinetic structure of embedded thin horizontal current sheets is investigated. Current density estimated by curlometer technique is in general agreement with a sum of electron and proton currents. Embedding of observed thin current sheets in the much wider plasma sheet is apparent in the current density profiles. Ion velocity distributions consist of two parts: the cold non-drifting core likely belongs to the plasma sheet background, while the hotter asymmetric "wings" carry the main portion of the current. Oxygen ions (if present) and higher-energy tails of distribution function can contribute up to 30% of the total current. We compared current density profiles across sheets with three typical current sheet models. Models which allow embedding, describe observed structures equally well at the level of experimental accuracy.

The eigenmodes of low frequency perturbations of thin anisotropic current sheets with a finite value of the normal magnetic field, are investigated in this paper. It is shown that two possible polarizations of symmetric and asymmetric modes (sausage and kink) exist where the growth rate of instabilities is positive. In addition, we demonstrate that a tearing instability might have a positive growth rate in thin anisotropic current sheets. The class of relatively fast wavy flapping oscillations observed by Cluster is described. The main direction of wave motion coincides with the direction of the current and the typical velocity of this motion is comparable with the plasma drift velocity in the current sheet. The comparison of these characteristics with theoretical predictions of the model of anisotropic thin current sheets, demonstrates that, in principle, the theory adequately describes the observations.

Recent development of popular substorm onset models was driven by the apparent controversy between ground onset mapping in the near-Earth tail and statistics of tailward flow observations (reconnection signatures), pointing to ∼ -25 R E downtail. However, several comprehensive multi-point event studies, taking into account backward tracing of flows, place plasmoid origin closer to the near-Earth location, in better consistency with auroral onset observations. Accuracy of such remote onset positioning is about a couple of Earth radii. We further discuss possibilities of reconciliation of different onset scenarios and future critical experiments.

Fast magnetic field polarity changes detected in the quiet magnetotail by a spacecraft are usually attributed to thin cross-tail cur-rent sheet crossings. On September 14, 2001, Cluster registered several such events. However the IMF was northward for the pre-vious 24 h and the formation of a thin current sheet was very unlikely. The multi-point analysis revealed that these sheets werealmost vertically oriented, had strong shear and vanishing normal magnetic components and therefore should be interpreted asboundaries between two independent magnetic field domains (flux tubes), rather than crossings of the main cross-tail current sheet.We suggest that such anomalous configuration might form in the course of high-latitude reconnection of geomagnetic lobe andinterplanetary field lines when IMF is northward. 2005 Published by Elsevier Ltd on behalf of COSPAR. Keywords: Magnetotail; Vertical current sheets; Northward IMF 1. IntroductionSince the first Dungey model (Dungey, 1961)itiswidely accepted that the dynamics of the Earths magne-tosphere is primarily determined by IMF reconnectionwith antiparallel geomagnetic field. When the IMF issouthward, it merges with geomagnetic field lines onthe day-side and new open field lines are added to thetail lobes, shaping the thin cross-tail current sheet withsmall normal component B

Estimates of the geomagnetic indices made with real-time solar wind measurements form the basis of many space weather forecast techniques. We analyze 20 years of hourly AL and OMNI solar wind data to determine geomagnetic importance of various solar wind and IMF parameters. Besides the solar wind driver of primary importance ( VB s ), the first-order contributions, significantly increasing the quality of the model are: solar wind velocity, 2 h of solar wind prehistory and 1 h of AL history. The factors of secondary importance, marginally contributing to overall statistical quality, are IMF B y , solar wind density, and IMF fluctuations. The dynamic pressure is geomagnetically effective only if the pressure is lower than the average. Modelling of the same data set with an artificial neural network (ANN) confirmed our selection of important factors. Statistically the ANN model was just marginally better than our analytic expression E = V B y 2 / 2 + B z 2 sin 4 ( θ / 2 ) + α V 2 sin 0.5 ( θ / 2 ) . The AU index dependence is principally different from AL in several respects; therefore modelling of the AE composite index is physically misleading.

We present a brief review of published results on the geomagnetic storm effectiveness of CMEs and solar flares as well as of interplanetary events. Attention is drawn to the fact that the published values of storm effectiveness are in conflict with one another. Possible reasons of their differences are discussed. The presented comparison of methods and results of the analysis of the phenomena on the Sun, in the interplanetary space and in the Earth's magnetosphere shows that in addition to different methods used in each of areas, a way of comparison of the phenomena in various space areas or for different direction of data tracing is of great importance for research of the entire chain of solar-terrestrial physics.

This report describes current and future solar-terrestrial space missions of the Russian Federal Space Agency. They are discussed in the context of the International Living With a Star activity aimed at consolidation of efforts in developing a balanced cooperative program of solar-terrestrial and space weather oriented research. We provide information on several missions that are at different stages of realization: solar observing – CORONAS-F, CORONAS-PHOTON, and INTERHELIOPROBE; and magnetospheric – RESONANCE, ROY, and INTERBALL-PROGNOZ.

Preliminary results of an analysis of satellite and ground-based measurements during extremely strong magnetic storms at the end of October 2003 are presented, including some numerical modeling. The geosynchronous satellites Ekspress-A2and Ekspress-A3, and the low-altitude polar satellites Coronas-F and Meteor-3M carried out measurements of charged particles (electrons, protons, and ions) of solar and magnetospheric origin in a wide energy range. Disturbances of the geomagnetic field caused by extremely high activity on the Sun were studied at more than twenty magnetic stations from Lovozero (Murmansk region) to Tixie (Sakha-Yakutia). Unique data on the dynamics of the ionosphere, riometric absorption, geomagnetic pulsations, and aurora observations at mid-latitudes are obtained.

We present new observational data on the phenomena of extremely high activity on the Sun and in the heliosphere that took place in October-November 2003. A large variety of solar and heliospheric parameters give evidence that the interval under consideration is unique over the entire observation time. Based on these data, comparing them with similar situations in the past and using available theoretical concepts, we discuss possible cause-and-effect connections between the processes observed. The paper includes the first results and conclusions derived by the collaboration "Solar Extreme Events-2003" organized in Russia for detailed inves- tigations of these events. As a result of our consideration, it is beyond question that the physical causes of solar and heliospheric phenomena in October-November 2003 are not exclusively local and do not belong only to the active regions and solar atmosphere above them. The energy reservoirs and driving forces of these processes have a more global nature. In general, they are hidden from an observer, since ultimately their sources lie in the subphotospheric layers of the Sun, where changes that are fast and difficult to predict can sometimes take place (and indeed they do). Solar flares can serve as sufficiently good tracers of these sudden changes and reconstruc- tions on the Sun, although one can still find other diagnostic indicators among the parameters of magnetic fields, motions of matter, and emission characteristics.

Russian Space Weather Initiatives (RSWI) support different models for space weather forecastin (http://alpha.npi.msu.su/RSWI/rswi.html). The models give the long-time (months-years) and short-time (days) predictions of the solar activity, heliospheric conditions, and dynamics of the Earth's magnetic field and radiation. Many different parameters measured from the Sun to the Earth's magnetosphere are used as inputs to the space weather models. The paper is devoted to a short overview of these models.

Before a substorm, the magnetotail is reconfigured to accommodate the enhanced solar wind energy input. Pressure build-up in the magnetotail and plasma sheet stretching are typical for substorms with the broad range of magnitudes. Before larger substorms, extra pressure increase can be compensated by plasma heating. Average growth phase duration for small and large isolated substorms differ by only the factor of two, while the solar wind input is different by the order of magnitude. These and other recent findings suggest there is no clear energy or magnetic flux threshold for the substorm initiation, and one rather should look for some time constant of the magnetotail system.

Based on about two years of Geotail data, we use a superposed epoch approach to study the average behavior of plasma and magnetic fields at different radial distances during 66 substorms in the premidnight sector. Magnetic field dipolarization is first seen inside of 16 R E around substorm onset and subsequently moves tailward at a rate of 0.4 R E /min. Fast earthward and tailward ion bulk flows in the central plasma sheet indicate that the near-Earth neutral line is first located around 21 R E , but later moves a bit tailward. About 30 min after onset, the tailward moving dipolarization front reaches the near-Earth neutral line at around 26 R E . Thereafter the near-Earth neutral line suddenly disappears beyond 31 R E . This may be the beginning of the recovery phase.

Multipoint observations on ground-based stations and a fleet of ISTP satellites allowed us to study the plasma processes in different regions of space for multiple (4) substorm event on December 22–23, 1996 which was characterized by almost constant solar wind pressure ∼ 1.2 nPa and southward IMF B z . Comparison of measurements in the plasma sheet at opposite flanks showed (1) the similar loading/unloading processes in the tail, correlated with substorm development, and (2) a strong bursty convection concentrated in the narrow ( ΔY ∼ 15 R E ) channel.

On the basis of ∼2 years of Geotail data, we use a superposed epoch approach to study the average behavior of plasma and magnetic fields at different radial distances, between 11 and 31 RE, during 66 substorms in the premidnight sector. Magnetic field dipolarization is first seen in the innermost region (11–16 RE) around substorm onset and subsequently moves tailward at a rate of 35 km/s. Fast earthward and tailward ion bulk flows in the central plasma sheet indicate that during substorm expansion the near-Earth neutral line is located between 21 and 26 RE, with a tendency to be closer to 21 RE near substorm onset. About 45 min after onset, the tailward moving dipolarization front reaches the distance range where the near-Earth neutral line is located. Thereafter the near-Earth neutral line disappears beyond 31 RE. This is the classical signature of the start of the recovery phase. We conclude that substorm recovery sets in when the tailward moving dipolarization front reaches the near-Earth neutral line, because the near-Earth neutral line cannot operate in a dipolar field geometry.

During ∼18 hours of continuous activity caused by long interval of southward IMF, the INTERBALL/Tail Probe and GEOTAIL spacecraft monitored the plasma sheet in dusk and dawn sectors of the midtail plasma sheet at 25–30 RE. While bursty bulk flows were persistently observed at both spacecraft, there was a systematic difference between the hourly averages of the Earthward flux transport. During a 3-hour interval the average flux transport rate (Ey) on GEOTAIL (dawn plasma sheet) was ∼3 times larger than both the average Ey on INTERBALL (dusk plasma sheet), and the cross-tail Ey0 expected for the existing IMF conditions. This implies that the most intense bursty bulk flows tend to be confined within a limited longitudinal sector of the magnetotail (X < −30 RE) forming the observed average convection jet feature.

Two typical bow shock crossings recorded by the Phobos-2 spacecraft in 1989 are considered in the present paper in order to demonstrate that the Martian bow shock is the shock of “common sense” in spite of peculiarities due to the pick-up ions of the Martian origin and their Larmour radius comparable to the scale size of the interaction region between the planet and solar wind. The incident plasma flow is decelerated and plasma species are heated within the relatively thin layer upstream the planet. The observed changes of plasma density, velocity and temperature are comparable with values expected for the MHD shock waves. Moreover, the dynamics of ion and electron energy distributions observed in the shock transition region indicates that mechanisms responsible for the energy dissipation seems to be similar to those operating at the Earth’s bow shock.

At 1130 UT on November 28, 1995, two spacecraft, Interball-Tail and Geotail, were in a favorable position to study the plasma sheet activity and an auroral breakup observed on the ground near the spacecraft ionospheric footpoints. Both spacecraft were near the neutral sheet, and they were nearly aligned along the magnetic meridian. During the auroral breakup observed at the equatorward half of the auroral oval (also registered as an AKR burst at Interball) both spacecraft simultaneously detected signatures of a reconnection pulse: The earthward plasma streaming and magnetic field dipolarization were observed at 12 R E at Interball, while the tailward energetic ion beam, then the tailward flow and the passage of a plasmoid were observed at 28 R E at Geotail. This pulse seem to proceed inside of the plasma sheet closed field lines, in the region of small (∼ 1nT) background magnetic field at the neutral sheet. At Interball position the onset of fast earthward ion flow, likely initiated by the reconnection pulse, was followed by other manifestations (dipolarization, enhancements of the magnetic turbulence and the energetic particle flux, the intensification of field-aligned currents). Auroral observations showed initial brightening delayed an approximately 1 min after the commencement of the reconnection pulse. The auroral intensification was not accompanied by a significant magnetic disturbance on the ground, and therefore the event can be classified as the pseudobreakup. We estimate magnetic flux transport characteristics and possible location of the onset region in the plasma sheet. We conclude that observations during this event are consistent with the initiation of an auroral breakup by some disturbance (e.g., Alfven wave) generated by the reconnection pulse that commenced in the neutral sheet at ∼15 R E distance.

The high-apogee Interball Tail Probe crosses the magnetopause in two latitude ranges: one is close to the equator, and the other is at middle and high latitudes. A brief description of dayside magnetopause observations from the fast plasma analyzer SCA-1 is given. We give examples of plasma regimes observed at low latitudes that show evidence for plasma cloud penetration into the magnetosphere. Nonstationary reconnection is suggested as a possible mechanism for the observed near-magnetopause structures.

The fast ion spectrometer SCA-1 on Interball Tail Probe measures 3-D ion distribution in the energy range 0.05–5.0 keV/Q in less than 10 sec. With new data we are testing the hypothesis, proposed on the basis of measurements on Prognoz-8 and Prognoz-10, that the thermalization of ion core on the strong Q-perpendicular shock front is provided by non-stationarity of the shock front. One supercritical Q-perpendicular bow shock crossing is analyzed. The downstream transmitted beam consists of multiple beams with thermal width of about upstream solar wind thermal width. This supports previous suggestion that the heated core of the downstream ion velocity distribution is formed of beamlets originating at patchy and oscillating structure of the shock front.

International audience; We present two examples of INTERBALL-1 data near both the high and low-latitude tail magnetopause (MP) under disturbed conditions. For the high-latitude case, MAGION-4 data determine the scales of the MP current sheets which are in the order of 100–500 km for the main ones, 50–200 km for Flux Transfer Events (FTEs) and a few km for the fine structures and ULF turbulence. The MP speed was 15–30 km/s. The energetic protons in the magnetosheath (MSH) provide evidence of reconnection upstream of the spacecraft (S/C). The tailward flows grow for the northward MSH magnetic field when the reconnection site is believed to be shifted tailward of the cusp. The inner boundary layer (BL) after the disturbance consists of tailward and earthward flowing plasma of MSH origin and cold mantle plasma flowing tailward The earthward flow is evidence of reconnection tailward of the S/C, which is regarded as a specific feature of the disturbed conditions. Local production of a plasma-sheet-like plasma at high latitudes is argued based on the inner BL plasma characteristics. The following features are observed in both cases: (a) FTEs for both northward and southward MSH fields; (b) waves in the current sheet vicinities over ten mV/m and 15 nT peak-to-peak; (c) electron fluxes with scales down to a few km with extra heating especially parallel to the magnetic field; (d) outer turbulent boundary layers with a deflected magnetic field; (e) ions with time-energy dispersion-like features and deflected ion fluxes. In the downstream dawn region at the transition between the low-latitude boundary layer and the plasma sheet (LLBL/PS), multiple MP encounters are observed. In the LLBL parallel electron intensifications correlate with ULF magnetic fluctuations.

INTERBALL-1 spacecraft with the subsatellite MAGION-4 was launched on August 3, 1995 to the highly elliptical orbit with the period of 92 hours and apogee 193000 km. Both spacecraft carry onboard the full spectrum of scientific instruments for the plasma investigation. The separation of two spacecraft varies from 100 to 10000 km. Such a distance permit to study spatial extents and velocities of the variety of large-scale and small-scale magnetospheric structures. INTERBALL-2 spacecraft, complementing the first pair on the auroral orbit with the period about 6 hours and apogee 19200 km, was launched at the 29th of August, 1996.

A closer look at the temporal evolution of the wave activity in the lobes of the Earth's magnetotail seems to suggest a long periodic modulation of the wave intensity. In order to test this suggestion we analyzed time series of the ULF electric field fluctuations in the northern lobes of the Earth's magnetotail, measured on board Prognoz-8. As a result we find that the wave activity seems to be modulated with a basic period of about 68 minutes and harmonics near 34, 21 and 16.5 minutes. We speculate that this periodicity is due to a global effect of the three-dimensional Earth's magnetosphere.

[1] We consider the electron distribution in current sheets observed by Cluster mission in the Earth magnetotail. We use the statistics of 70 fast (less than 20 minutes) and 12 slow (more than one hour) crossings of horizontal current sheets. We demonstrate that for both types electron temperature decreases with increase of magnetic field ∣Bx∣ away from the current sheet center. We use the approximations Te⊥/Te⊥ max ≈ 1 − αT⊥(Bx/Bext)2 and Te∥/Te∥ max ≈ 1 − αT∥(Bx/Bext)2, where Bext is value of Bx in the lobes. For statistics of thin current sheets (fast crossings) we obtain mean values 〈αT⊥〉 ≈ 〈αT∥〉 ≈ 1. For thick current sheets (slow crossings) we also obtain 〈αT⊥〉 ≈ 〈αT∥〉, but 〈αT⊥〉, 〈αT∥〉 > 1. The electron temperature anisotropy is about Te∥/Te⊥ = 1.1 − 1.2 and vertical profiles Te∥/Te⊥ ≈ const. Observed vertical distributions of Te∥ and Te⊥ are described by the analytical model of electron heating in the course of the earthward convection in thin current sheets with (Bx(z), Bz(x)) and in thick current sheets with (Bx(x, z), Bz(x, z)). We also show that the observed electron temperature anisotropy is provided by the electron population in the energy range between 50 ev and 3 keV. The cold core of electron distribution ( 5 keV) has Te∥/Te⊥ ∼ 1 or even Te∥/Te⊥

The strong magnetic field B-y component (in GSM coordinates) has been increasingly noticed to play an important role in the dynamics of tail current sheet (CS). The distribution profile of strong B-y components in the tail CS (i.e., those with guide field), however, is not well known. In the present work, by using the simultaneous multipoint observations of Cluster satellites, the profile of a strong B-y component in tail current sheets is explored, through detailed case studies, as well as in a statistical study. It is discovered that around the midnight meridian, the strength of the strong B-y component, i.e., |B-y|, is basically enhanced at the center of the CS relative to that in the CS boundaries and lobes and forms a north-south symmetric distribution about the center of CS. Generally, however, for strong guide field cases in the non-midnight meridian, the profile of B-y strength basically becomes north-south asymmetric, the strength of the B-y component in the northern side of the CS is found to be either stronger or weaker than that in the counterpart southern side. By considering the modulation of the tail flaring magnetic field with magnetic local time, we propose an interpretation to account for the variation of the B-y-profile, which is supported by the statistical survey. These results offer an observation basis for further studies.

[1] In this paper we use the statistics of 70 crossings by the Cluster mission to study and compare properties of thin current sheets observed at the dawn and dusk flanks of the Earth magnetotail. Special attention is devoted to the current sheet embedding: we define the degree of the current sheet embedding as be = Bext/B0 (B0 and Bext are magnetic field magnitudes at the thin current sheet boundary and in the lobes). We determine the current density by curlometer technique and calculate the current sheet thickness. We demonstrate that the current sheets at the dawn flank have larger be, smaller magnitude of the current density and larger relative thicknesses in Larmor radii than the current sheets at the dusk flank. Protons in thin current sheets are divided into two populations (the current-carrying particles and the background) and the temperatures of these populations have been estimated. The distribution of the proton temperature p inside typical current sheet is approximated as p ≈ Tp(1 − αT(Bx/Bext)2), where Tp is the p value in the central region of the current sheet. The average value 〈αT〉 ≈ 0.8. The proton current density (flow velocity in Y) is positive at the dusk flank and negative at the dawn flank, while the electron current density is positive at both flanks. This difference of the proton current density at two flanks is explained by the E × B drift due to the presence of the earthward electrostatic field Ex. We develop a simple model of the earthward electrostatic field to incorporate the influence of the embedding and the dawn-dusk magnetic field component.