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1.
A guided propagation of magnetoacoustic wave in the plasma sheet located between two lobes of the magnetotail is investigated. The dispersion equation for the wave and equation connecting a disturbance of plasma pressure inside the plasma sheet and amplitude of the plasma sheet boundary oscillations are obtained. For some value of plasma pressure disturbance, the displacement of the plasma sheet boundaries becomes of order of the half-thickness of the plasma sheet. In the case of symmetrical oscillations of the boundaries (“sausage-like” mode), it creates the favorable conditions for reconnection of the magnetic field lines in the magnetotail and may lead to triggering of a substorm. The magnetoacoustic wave may be generated by sudden impulse of the solar wind plasma pressure. 相似文献
2.
N. I. Izhovkina 《Geomagnetism and Aeronomy》2010,50(3):362-368
Electric fields in the near-Earth space was studied in the experiments with artificial plasma clouds and jets in the ionosphere
and magnetosphere. The development of a nonmonotonous plasma density stratification of an artificial plasma formation, with
the scale of strata across the geomagnetic field reaching several meters and tens of meters, was observed. It has been indicated
that the electrodynamics of plasma clouds and jets, decomposing into strata, depends on the excitation and decay of fast oscillations
of the electronic plasma component against a background of slow oscillations of the ionic component at frequencies of magnetized
plasma electrostatic oscillations (electrostatic Bernstein modes of the plasma electronic and ionic components and ion acoustic
oscillations). 相似文献
3.
Geomagnetism and Aeronomy - The directivity of transverse electromagnetic waves generated in a plasma at a double plasma frequency during the coalescence of plasma waves is calculated for various... 相似文献
4.
N. I. Izhovkina A. T. Karpachev I. S. Prutensky S. A. Pulinets Z. Klos H. Rotkel 《Geomagnetism and Aeronomy》2009,49(8):1254-1256
It has been indicated that the spectrum of electrostatic waves in the ionospheric plasma depends on the geophysical conditions
and solar wind parameters. The wave field measurements in the frequency band 0.1–10 MHz in the topside ionosphere were used
to analyze the electrostatic instabilities of the plasma electron content (the APEX satellite experiment). A change of the
sign of one magnetic field component at the geomagnetic equator can result in the formation of the large-scale irregular plasma
structure with a decay of the natural electrostatic oscillations and vortices in unstable plasma. The plasma particle polarization
drift from the region of decay of electrostatic oscillations and vortices can cause large plasma density and temperature gradients
across the geomagnetic field. New vortices can originate at these gradients. This mechanism of plasma vortex formation and
decay can be important for mass and energy convection in the topside ionosphere. 相似文献
5.
The profiles of the plasma density in the topside ionosphere, according to the data of sounding on board the Intercosmos-19 satellite, are presented. It is shown that the large-scale fluctuations of the plasma density can be related to the propagation and attenuation of the atmospheric waves (e.g., acoustic gravity waves) in the dynamo region of the ionosphere. In the topside ionosphere, suprathermal particle fluxes can be formed and the plasma density can be modulated at an attenuation of small-scale electrostatic fluctuations of the plasma electron component in plasma pits. Plasma vortices can be formed when polarization fluxes of charged particles escape from regions of heating. The vortex field imparts stability to the inhomogeneous plasma structure, necessary for experimental detection of this structure. 相似文献
6.
本文使用Cluster-C1卫星的CIS仪器和FGM仪器测量得到的质子通量数据和计算的β数据,判断Cluster卫星在地球磁尾不同位置位于等离子体片内的概率.使用2001—2004年7—11月的Cluster-C1数据,分别在行星际磁场南向和北向时,得出X-10RE区域内卫星位于等离子体片的概率在Y-Dz平面的分布图(Dz是卫星到中性片的距离).通过对比行星际磁场南向和北向时的卫星位于等离子体片的概率的分布图,我们发现等离子体片在行星际磁场南向时比在行星际磁场北向时要薄,并且这个效应在磁尾晨昏两侧比在午夜附近明显,同时我们还发现等离子体片在晨侧比在昏侧厚. 相似文献
7.
N. I. Izhovkina 《Geomagnetism and Aeronomy》2011,51(3):342-347
The density and temperature of the plasma electron component and wave emission intensity in the topside ionosphere were measured
by the INTERCOSMOS-19 satellite. In the subauroral ionosphere, a decrease in the plasma density correlates with an increase
in the plasma electron component temperature. In this case, the additional increase in the electron component temperature
was measured in regions with increased plasma density gradients during the substorm recovery phase. In a linear approximation,
the electromagnetic wave growth increments are small on electron fluxes precipitating in the auroral zone. It has been indicated
that Bernstein electromagnetic waves propagating in the subauroral topside ionosphere can intensify in regions with increased
plasma density gradients on electron fluxes orthogonal to the geomagnetic field, which are formed when plasma is heated by
decaying electrostatic oscillations of the plasma electron component. This can be one of the most important factors responsible
for the intensification of auroral kilometric radiation. 相似文献
8.
Simulation of Physical Phenomena in the Ionosphere and Magnetosphere of the Earth on Krot Plasma Device. Some Results and Prospects 总被引：1，自引：0，他引：1
Krot device is a unique installation of the scientific infrastructure of the Russian Federation. It is a source of highly uniform low-temperature plasma that takes up to several tens of cubic meters. The setup makes it possible to perform both scaling laboratory simulations of ionospheric and magnetospheric phenomena in the approximation of unbound plasma, as well as plasma tests of full-size samples of the onboard equipment of spacecraft (SC). The simulation results of the dynamics and interaction of small-scale thermal plasma irregularities occurring during ionospheric heating experiments are presented. The impedance of the small-size models of RESONANCE and STRANNIK SC electric antennas in plasma is measured. The possible use of free-space calibration of antennas in the magnetospheric portions of the orbit in the ELF and VLF ranges is confirmed. The efficiency of a new plasma parameters resonance sensor for the TRABANT SC in the ionospheric range of electron densities is shown. 相似文献
9.
The electron component of intensive electric currents flowing along the geomagnetic field lines excites turbulence in the thermal magnetospheric plasma. The protons are then scattered by the excited electromagnetic waves, and as a result the plasma is stable. As the electron and ion temperatures of the background plasma are approximately equal each other, here electrostatic ion-cyclotron (EIC) turbulence is considered. In the nonisothermal plasma the ion-acoustic turbulence may occur additionally. The anomalous resistivity of the plasma causes large-scale differences of the electrostatic potential along the magnetic field lines. The presence of these differences provides heating and acceleration of the thermal and energetic auroral plasma. The investigation of the energy and momentum balance of the plasma and waves in the turbulent region is performed numerically, taking the magnetospheric convection and thermal conductivity of the plasma into account. As shown for the quasi-steady state, EIC turbulence may provide differences of the electric potential of δ V ≈ 1–10 kV at altitudes of 500 < h < 10 000 km above the Earth’s surface. In the turbulent region, the temperatures of the electrons and protons increase only a few times in comparison with the background values. 相似文献
10.
《Journal of Atmospheric and Solar》2002,64(2):115-124
Auroras have been extensively studied using images obtained by space-borne experiments. We use global UVI images obtained from Polar and simultaneous plasma data obtained by the 3D instrument on Wind from the near-earth plasma sheet to study the dynamics of auroras with different size and intensity. Unstable phase space ion distributions are detected in the plasma sheet under diverse geomagnetic and solar wind IMF conditions (positive and negative Bz) and at all phases of a substorm. These results indicate that plasma instability processes with different disturbance levels operate in the plasma sheet and produce a continuum of auroral size and intensity. The criteria for triggering an instability are dependent on the local properties of the plasma distributions. These observations suggest a new framework to integrate previous and current results and a new way to examine the causal relationships of auroral and plasma sheet dynamics. 相似文献
11.
本文建立了一个包含离心力效应的自洽稳态土星磁层模型,并且用等离子体细丝模型对土星磁层等离子体径向输运进行了数值模拟.模拟结果表明,Dione（土卫四）附近的等离子体可能因为发生离心交换不稳定性（Centrifugal Interchange Instability）而被输运到离土星更远的地方.这种输运现象的发生是由离心力主导的,等离子体的黏滞效应和能量转移对输运过程的影响非常小（几乎可以忽略不计）,但土星电离层电导率对输运过程有重要影响,电导率越低,径向输运过程越快,反之,高电导率在一定程度上会阻碍输运的进行.在土星电离层电导率σ=2 S时,Dione（距离土星6.3RS, RS为土星半径）附近的等离子体在5.52个小时中被输运到距离土星10RS的地方.本文的模拟结果还表明,密度受到扰动的等离子体是不稳定的,如果洛仑兹力和等离子体热压强梯度不能与离心力平衡,径向输运就会发生.密度大的等离子体在向外输运过程中会绝热膨胀而温度降低,密度小的等离子体则在注入磁层过程中因为绝热压缩而温度升高. 相似文献
12.
《Journal of Atmospheric and Solar》2002,64(5-6):567-572
The possibility to estimate plasma sheet parameters from low-altitude measurements looks quite attractive, but it critically depends on how isotropic the plasma pressure is in the flux tube. To evaluate the ion pressure anisotropy we compare the values of pressure in the ionospheric and equatorial parts of the field line. Ionospheric values were computed from proton measurements at NOAA low-altitude satellites, they were compared with pressure estimates computed from empirical magnetic field models as well as with average values known from direct plasma sheet measurements. Three different methods of mapping the plasma pressure from plasma sheet to low altitude have been tried; each uses the particle isotropic boundaries observed at low altitudes and/or computed from magnetospheric models. Excluding observations obtained during substorm expansion, from these comparisons we conclude that in the plasma sheet, at geocentric distances 9–20RE, the pressure estimates in the ionospheric and equatorial parts of the plasma sheet flux tube agree very well, suggesting a good pressure isotropy and thus justifying a possibility to monitor the plasma sheet parameters based on low-altitude measurements. The results also illustrate the usefulness of isotropic boundaries as a label of tail current intensity and as reliable tool for establishing mapping between magnetosphere and ionosphere. 相似文献
13.
《Journal of Atmospheric and Solar》2000,62(16):1509-1514
We examined 126 limb flares formed between October 1991 and August 1998. X-ray plasma ejections were found in 54 flares. All the X-ray plasmoids were detected in images taken before the maximum peak of hard X-ray (HXR) emission or in each of the first image after the HXR peak. In our choice of 57 flares which Yohkoh started to observe before the HXR peak, with the soft X-ray telescope aboard, X-ray plasma ejections were found in ∼63–70% of these flares. We found X-ray plasma ejections in 100% of X-class flares and 74–82% of M-class flares, whereas only 31–38% of C-class flares have X-ray plasma ejections. It is difficult to detect X-ray plasma ejections in C-class flares, because the scale size and lifetime of ejections are short. We propose that solar flares including microflares occur through magnetic reconnection and that X-ray plasma ejections are general phenomena associated with solar flares. 相似文献
14.
15.
Based on observations of electromagnetic radiation, a concept of thermal solar flares has been proposed. The absence of hard X-ray emission implies no accelerated electrons. This fact is the basis of the proposed concept of thermal flares. Since the acceleration rate should not exceed the electron energy loss rate, plasma density in the acceleration range must be at least 1011 cm?3. The temperature of plasma emitting in the soft X-ray range is of the order of 107 K. In the simplified problem of heated plasma hydrodynamics, we calculated the temperature profiles and their changes over time and by coordinate. The emission measure values determined from observations of the soft X-ray emission of flares is of the order of 1045 cm?3. The geometry of the source is an axial symmetric straight cylinder with a section of 1016 cm2 and an axial coordinate determined by the depth of plasma heating. Time profiles of soft X-ray emission were calculated for different sources of plasma heating, which were simulated using the Gaussian distribution law with respect to the coordinate and time. We have considered two modes of plasma heating: single (in time) and multipulse modes with different pulse intervals. The dynamics of plasma heating and cooling was shown to control the experimentally observed time profiles of soft X-ray emission. A comparison of numerical results with observational data allows us to confirm the implications of the proposed concept of thermal flares and, in addition, to perform diagnostics of plasma parameters in the emission source. 相似文献
16.
本文同时利用DMSP、ROCSAT-1卫星数据和地基的GPS观测数据,研究一种与低纬等离子体泡相伴随的局部等离子体浓度增强现象.地基GPS的观测表明电离层总电子含量(TEC)也能反映这种等离子体浓度增强.通过4个观测事例的详细分析表明:这种等离子体浓度增强主要出现在磁纬±10°～±20°的局部区域,有时在近磁赤道区和中纬地区的电离层顶部也能观测到;与等离子体泡的出现规律相似,这种等离子体浓度增强主要出现在地方时21∶00以后,并在午夜后也能观测到.当等离子体浓度增强和等离子体泡发生时,在午夜前一般对应着背景垂直速度明显向上的扰动,在午夜后一般处于等离子体垂直速度下降至反向前的时间段,表明东向电场对于低纬不规则体的产生有非常重要的作用. 相似文献
17.
本文讨论了等离子体湍流对电子加速的两种模型:（1）假定在空间中存在一个空间均匀的等离子体湍流区,当具有一定初始分布的电子束通过此湍流区时,研究湍流场对电子束的加速过程;（2）在某一封闭的区域中,存在着具有一定初始分布和空间均匀的等离子体,当某种类型的等离子体波突然传入此等离子体区,然后考察此区中电子的加速过程。在这两种模型中,可能存在着某种电子消失机制。假定湍谱是幂指数形式,我们给出了不同类型湍流扩散系数的普遍形式。利用较简单的数学方法,求解了包括消失过程的一维准线性动力学方程,对于给定的初始分布,得出了分布函数的解析解,并给出了平均能量时间关系的表达式。另外,对于特定的湍谱指数,解出了当平行电场和湍流同时存在时的分布函数。最后,对所得结果进行了数值分析和讨论。 相似文献
18.
The structure and dynamics of ion-acoustic waves in an unmagnetized plasma, including the case of weakly relativistic collisional plasma (when it is necessary to take into account the high energy particle flows which are observed in the magnetospheric plasma), are studied analytically and numerically on the basis of a model of the Kadomtsev-Petviashvili (KP) equation. It is shown that, if the velocity of plasma particles approaches the speed of light, the relativistic effects start to strongly influence on the wave characteristics, such as its phase velocity, amplitude, and characteristic wavelength, with the propagation of the twodimensional solitary ion-acoustic wave. The results can be used in the study of nonlinear wave processes in the magnetosphere and in laser and astrophysical plasma. 相似文献
19.
V. Pinto M. Stepanova E.E. Antonova J.A. Valdivia 《Journal of Atmospheric and Solar》2011,73(11-12):1472-1477
We have studied the turbulent processes in the central plasma sheet using the tailward alignments of THEMIS satellites. Fluctuations of the plasma bulk velocity and corresponding eddy-diffusion coefficients were calculated using the simultaneous data obtained by THEMIS satellites situated inside the central plasma sheet between approximately 5 and 30 Earth's radii. The instantaneous profiles of eddy-diffusion coefficients show an increase with distance from the Earth in the tailward direction. This result agrees with previous statistical studies, and it is relevant for the understanding of the dynamics of the turbulent plasma sheet. 相似文献
20.
Geomagnetism and Aeronomy - The transfer of accelerated electrons in the plasma of flaring loops is accompanied by a hydrodynamic response of the heated plasma. The dynamics of the accelerated... 相似文献