A diffusion model of radial distributions of plasma density from measurements on the Cassini spacecraft in the inner magnetosphere of Saturn

Equatorial radial distributions of plasma density in the 3 < L < 9 region of Saturn’s magnetosphere, obtained from measurements on the Cassini spacecraft, are considered on the basis of diffusion theory. The concentration of particles in the magnetic tubes is found to grow with L. The external source is located at L ? 9. The particles diffuse to Saturn. In the 5 < L < 9 interval the distribution is close to equilibrium. A relation between the diffusion coefficient and the densities of internal sources and losses is obtained in this interval. Prevalence of losses over sources is very probable. Estimates of the diffusion flux and its derivative are given. If the diffusion coefficient is expressed as D _LL = D _o L ³ and the contencentration of particles depends on L according to a power law, the diffusion rate is constant.     

Turbulent fluctuations of plasma and magnetic field parameters in the magnetosheath and the low-latitude boundary layer formation: Multisatellite observations on March 2, 1996

The results of simultaneous analysis of plasma and magnetic field characteristics measured on the INTERBALL/Tail Probe, WIND and Geotail satellites on March 2, 1996, are presented. During these observations the INTERBALL/Tail Probe crossed the low-latitude boundary layer, and the WIND and Geotail satellites measured the solar wind’s and magnetosheath’s parameters, respectively. The plasma and magnetic field characteristics in these regions have been compared. The data of the Corall, Electron, and MIF instruments on the INTERBALL/Tail Probe satellite are analyzed. Fluctuations of the magnetic field components and plasma velocity in the solar wind and magnetosheath, measured onboard the WIND and Geotail satellites, are compared. The causes resulting in appearance of plasma jet flows in the low-latitude boundary layer are analyzed. The amplitude of magnetic field fluctuations in the magnetosheath for a studied magnetosphere boundary crossing is shown to exceed the magnetic field value below the magnetopause near the cusp. The possibility of local violation of pressure balance on the magnetopause is discussed, as well as penetration of magnetosheath plasma into the magnetosphere, as a result of magnetic field and plasma flux fluctuations in the magnetosheath.     

First results of investigating the space environment onboard the Universitetskii-Tatyana satellite

The complex of scientific pay load installed onboard the research and educational Universitetskii-Tatyana microsatellite of Moscow State University is described. The complex is designed to study charged particles in the near-earth space and ultraviolet emissions of the atmosphere. Data of the measurements of charged particle fluxes in the microsatellite orbit are presented, spectra are calculated, and the dynamics of penetration boundaries for protons of solar cosmic rays (SCR) during geomagnetic disturbances in 2005 is investigated. Intensities of the ultraviolet emission are measured in the entire range of variation of the atmospheric irradiation, as well as intensities of auroras in the polar regions of the Northern and Southern hemispheres. The experimental data on flashes of ultraviolet radiation (transient light phenomena in the upper atmosphere) are considered, and some examples of oscillograms of their temporal development and their distribution over geographical coordinates are presented. Original Russian Text ? V.A. Sadovnichy, M.I. Panasyuk, S.Yu. Bobrovnikov, N.N. Vedenkin, N.A. Vlasova, G.K. Garipov, O.R. Grigorian, T.A. Ivanova, V.V. Kalegaev, P.A. Klimov, A.S. Kovtyukh, S.A. Krasotkin, N.V. Kuznetsov, S.N. Kuznetsov, E.A. Muravyeva, I.N. Myagkova, N.N. Pavlov, R.A. Nymmik, V.L. Petrov, M.V. Podzolko, V.V. Radchenko, S.Ya. Reisman, I.A. Rubinshtein, M.O. Riazantseva, E.A. Sigaeva, E.N. Sosnovets, L.I. Starostin, A.V. Sukhanov, V.I. Tulupov, B.A. Khrenov, V.M. Shakhparonov, V.N. Sheveleva, A.V. Shirokov, I.V. Yashin, V.V. Markelov, N.N. Ivanov, V.N. Blinov, O.Yu. Sedykh, V.P. Pinigin, A.P. Papkov, E.S. Levin, V.M. Samkov, N.N. Ignatiev, V.S. Yamnikol, 2007, published in Kosmicheskie Issledovaniya, 2007, vol. 45, No. 4, pp. 291–305.     

Eigen Ultra-Low-Frequency Magnetosonic Oscillations of the Near Plasma Sheet

A critical analysis of existing theories of the magnetospheric resonator for fast magnetosonic waves is performed. A new variant of the theory is suggested, according to which the near-Earth part of the plasma sheet plays the role of the resonator. It is shown that the magnetosonic wave is locked inside this region over its entire boundaries. The eigen frequencies of resonator modes are in a good agreement with observed values (0.8, 1.3, 1.9, 2.6, 3.4, ... MHz), both when estimated in the order of magnitude and when calculated exactly in the context of a simple model.     

Dynamics of debye-scale nonstationary plasma structures in the region of auroral field-aligned currents

We consider the formation of small-scale nonstationary plasma structures in the region of relatively strong field-aligned electric currents. The formation of these structures has been shown to be associated with the density instability developed when the current velocity exceeds a critical value. The conditions for the development of this instability can be most favorable in the region of low-density plasma. Numerical calculations have been performed for the initial nonlinear stage of the structure development. The main parameters of the structure, i.e., the times of its formation and destruction, spatial scales, and electric field, have been estimated. The features of the structures are consistent with the existing data from space experiments in the region of auroral field-aligned currents of the Earth.     

Statistical investigation of Heliospheric conditions resulting in magnetic storms: 2

This work is a continuation of investigation [1] of the behavior of the solar wind’s and interplanetary magnetic field’s parameters near the onset of geomagnetic storms for various types of solar wind streams. The data of the OMNI base for the 1976–2000 period are used in the analysis. The types of solar wind streams were determined, and the times of beginning (onsets) of magnetic storms were distributed in solar wind types as follows: CIR (121 storms), Sheath (22 storms), MC (113 storms), and “uncertain type” (367 storms). The growth of variations (hourly standard deviations) of the density and IMF magnitude was observed 5–10 hours before the onset only in the Sheath. For the CIR-, Sheath-and MC-induced storms the dependence between the minimum of the IMF B _z-component and the minimum of the D _st -index, as well as the dependence between the electric field E _y of solar wind and the minimum of the D _st -index are steeper than those for the “uncertain” solar wind type. The steepest D _st vs. B _z dependence is observed in the Sheath, and the steepest D _st vs. E _y dependence is observed in the MC.     

On correctness of canonical formulation of the problem of motion of submicron particles in the Earth’s plasmasphere

The general conditions of applicability are formulated for the canonical formulation of the problem of motion of micro-particles with variable electric charge in the near-Earth space. The validity of these conditions is demonstrated for particles of sub-micron dimension executing orbital motion in the Earth’s plasmasphere.     

Identification of sources of Pc1 geomagnetic pulsations on the basis of proton aurora observations

The relationship between proton aurora and geomagnetic pulsations Pc1, which are an indicator of development of ion-cyclotron instability in the equatorial magnetosphere, are studied on the basis of the observations of proton aurora from the IMAGE satellite, observations of particle fluxes onboard the low-orbiting NOAA satellites, and geomagnetic pulsation observations at the Lovozero observatory. A conclusion is drawn that the subauroral spots in the proton emission projected into the magnetosphere near the plasmapause are two-dimensional images at the ionospheric “screen” of the region of intense scattering of energetic protons into the loss cone at the development of an ion-cyclotron instability.     

Dynamics of polar boundary of the auroral oval derived from the IMAGE satellite data

Based on a new database on positions of the auroral oval boundaries including measurements made by the IMAGE satellite in 2000–2002 with correct determination of the glow boundaries, statistical estimations of the latitudinal position of the polar cap boundary (PCB) are obtained depending on the IMF B _y and B _z , and the PCB evolution during a magnetic storm is analyzed. At zero IMF in the noon (midnight) sector, PCB is located approximately at 80° (76°) CGMLat. The PCB displacement along the noon-midnight meridian is controlled by the IMF B _z , and in the noon (midnight) sector it is equal to 0.45° (0.15°) CGMLat when B _z changes by 1 nT. The PCB displacement along the dawn-dusk meridian depends on the IMF B _y , and it equals 0.1° CGMLat when B _y changes by 1 nT. Accordingly, the north polar cap as a whole is shifted to the dawn (dusk) side at B _y > 0 (B _y <0). After northward turn of the IMF during the storm’s recovery phase, the PCB on the dayside is shifted to the north practically without time delay. The night boundary requires 25 h or more in order to be shifted to the pole to a latitude corresponding to B _z > 0.     

Structure of current and plasma in current sheets depending on the conditions of sheet formation

The structure of current sheets created under laboratory conditions is characterized by a large variety, which depends substantially on the conditions under which the sheet if formed. In this work, we present the results of an experimental study of the structure and evolution of current sheets that were formed in magnetic configurations with a singular line of the X type. It has been shown that the change in the transverse magnetic field gradient, the strength of the longitudinal magnetic field, and the mass of the ions in plasma makes it possible to significantly vary the main parameters of the current sheets. This offers the challenges of using laboratory experimental results for analyzing and simulating the cosmophysical processes.     

Numerical simulation of effects of the August 11, 1999 solar eclipse in the outer ionosphere

The results of a numerical simulation of such parameters of the topside ionosphere as concentration N _e and temperature T _e of electrons, and concentration n(H⁺) and fluxes along the magnetic field lines Φ(H⁺) of H⁺ ions at an altitude of ～2000 km for the conditions of the August 11, 1999 solar eclipse are presented. The calculations were performed using the Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere of the Earth (GSM TIP). It is shown that during the eclipse, in addition to a region of decreased values of T _e in the Northern Hemisphere and in the magnetically conjugate region in the Southern Hemisphere, regions of electron heating emerge in both hemispheres. Simultaneously, an extended region of decreased values of N _e comes into existence and moves behind the Moon’s shadow. Regions with decreased (down to ～30%) and enhanced (up to ～50%) concentrations of H⁺ ions are detected in the global distribution of these ions.     

二次电子发射对稳态等离子体推进器加速通道鞘层的影响

稳态等离子体推进器( Stationary Plasma Thruster,SPT)工作时产生的高密度等离子体遇到其加速通道陶瓷器壁时,在陶瓷器壁与等离子体之间形成鞘层.离子会在鞘层电场作用下到达SPT加速通道器壁表面进而复合,而等离子体中的电子由于具有高能可跃过鞘层电场轰击器壁表面,从而产生二次电子发射效应.从器壁表面发射出的二次电子由于受到鞘层电场的排斥,导致其向等离子体源区移动,进而影响等离子体鞘层的特性.建立了考虑二次电子发射效应的无碰撞等离子体鞘层的一维流体模型,研究了二次电子发射对SPT加速通道鞘层特性的影响.计算结果显示,随二次电子发射系数增加,鞘层电势、离子密度、电子密度和二次电子密度增加,而离子速度降低,鞘层中离子密度始终大于电子密度.鞘层中二次电子绝大多数集中在器壁附近,随二次电子穿越鞘层厚度的增加,二次电子密度快速下降.     

On the stress-strain state of film structures in space at electrodynamic deployment

We discuss a possibility of using the Ampere force for deployment and stabilization of film structures in space. It is supposed that a conductor connected with a power supply is deposited on the surface of a thin film, or solar batteries are used as conductors with current. The stress and strain of the thin film, caused by the electric current flow over a circular conductor confining this film, are found. The method of calculating the radial component of the stress tensor in a film, connected with concentric circular conductors with current, is obtained. The distribution of stresses for a film with three conductors is calculated. A possibility of minimizing the magnetic moment of a system of currents is discussed.     

霍尔推力器羽流离子能量实验研究

霍尔推力器羽流中的离子能量分布情况对于评估推力器羽流影响,优化推力器在航天器上的布局具有重要意义。本文使用阻滞势分析器对霍尔推力器羽流的离子能量分布进行了实验研究,获得了推力器在不同工况下羽流场中关注位置的离子能量分布状况。实验结果表明:霍尔推力器羽流离子主要由电荷交换碰撞产生的低能量离子和高能量源离子组成;高能量源离子的分布在推力器轴线达到最大值,低能量离子的分布随着与推力器轴线夹角的减小呈先增后减态势;随着霍尔推力器放电电压的提高,羽流源离子能量分布会相应向高能量方向偏移。     

Finding the dispersion of low-frequency waves in cosmic plasma from the results of multi-satellite measurements

An improved method of analysis of low-frequency wave processes in the interplanetary plasma using the results of multi-satellite measurements is presented. The new method develops the phase difference method and is distinguished by the fact that it allows one to analyze wavelengths several times shorter than the mean separation between spacecraft that perform the measurements. Its capabilities and the feasibility of analyzing events in different regions where spacecraft plasma measurements are undertaken are demonstrated using several examples of dispersion functions obtained by this method from the results of processing the magnetic field measurements on four spacecraft of the Cluster mission. The remarkable role played by ion-cyclotron oscillations in the outer magnetosphere cusp region is demonstrated, which manifests itself in wave generation and nonlinear structure formation.