Injection of 40-kHz-modulated electron beam from the satellite: II. Excitation of electrostatic and whistler waves

Beam-plasma interaction effects are studied during the active space experiment with electron and Xe-ion beam injections in an ionospheric plasma. Permanent 40-kHz-modulated electron beam injection occurs simultaneously with a xenon-ion beam injected by the Hall-type plasma thruster operating in a square-pulse mode (100/50 s for a job/pause duration). The unusual behavior of the background charged particle fluxes and wave activity stimulated during the beam-plasma interaction have been registered by the scientific instruments onboard Intercosmos-25 station (IK-25) and Magion-3 subsatellite. The longitudinal and electromagnetic wave instabilities and their mutual relationship are considered in order to explain the observed effects. The excitation of electrostatic waves by the electron injection has been considered for different resonance conditions near the linear stability boundary. Beam-driven electromagnetic instability is responsible for the backward-propagating whistler waves excited via cyclotron resonance. Competition of these two beam instabilities is one of the subjects of the present study.     

Remote spacecraft observations of waves excited by the pulse electron beam injected into ionosphere

In the Apex project the modulated electron beam (pulses of 2 micro sec duration, E=8 keV, I=0.1 A and 25 micro sec repetition) was emitted from a main satellite. The RF emissions were observed in parallel on the mother satellite as well as on Magion-3 subsatellite. The paper discusses the case when the subsatellite was separated about 200 km from the main object and the electron gun was operated. Together with strong electrostatic emission at the upper hybrid plasma frequency on the main spacecraft, selected spikes in RF frequency range on Magion-3, were simultaneously detected, which can be related to pulse electron beam emission.     

New aspects of whistler waves driven by an electron beam studied by a 3-D electromagnetic code

We have restudied electron beam driven whistler waves with a 3-D electromagnetic particle code. In the initialisation of the beam-plasma system, “quiet start” conditions were approached by including the poloidal magnetic field due to the current carried by beam electrons streaming along a background magnetic field. The simulation results show electromagnetic whistler wave emissions and electrostatic beam modes like those observed in the Spacelab 2 electron beam experiment. It has been suggested in the past that the spatial bunching of beam electrons associated with the beam mode may directly generate whistler waves. However, the simulation results indicate several inconsistencies with this picture: (1) the parallel (to the background magnetic field) wavelength of the whistler wave is longer than that of the beam instability, (2) the parallel phase velocity of the whistler wave is smaller than that of the beam mode, and (3) whistler waves continue to be generated even after the beam mode space charge modulation looses its coherence. The complex structure of the whistler waves in the vicinity of the beam suggest that the transverse motion (gyration) of the beam and background electrons is involved in the generation of the whistler waves.     

HF wave activity in the low and middle-altitude polar cusp

We reported the results of our investigations of wave activity in high-frequency range performed on board CLUSTER spacecraft in the middle-altitude cusp region, around 5 R_E during August and September 2002. Our analysis was mainly based on the registration gathered by the WHISPER instrument (Waves of HIgh frequency and Sounder for Probing of Electron density by Relaxation). For a better understanding of the processes of wave-particle interaction and in order to understand the general plasma conditions in the cusp region, we also included in our analysis the data registered by the STAFF (Spatio-Temporal Analysis of Field Fluctuation experiment) instrument and the CIS (Ion Spectrometry experiment) instrument. These observations were carried out during different geomagnetic activity; under quiet conditions and during magnetic storm period. The space plasma is characterised by the ratio of plasma frequency to electron gyrofrequency, in this case, the local plasma frequency was, mainly, a little greater than the electron plasma, but it was also frequently observed that these two characteristic frequencies were not very different from one another. The whistler waves, electron-cyclotron waves, electron-acoustic waves and Langmuir waves have been detected when the spacecraft was crossing the middle-altitude cusp region. We suggested that the majority of those waves were generated by electron beams. For a better understanding the plasma conditions in the low and middle-altitude cusp region the past FREJA wave data results are used to describe typical wave activity detected in the low-altitude cusp region. The aim of this paper is to discuss, on the basis of a few chosen representative examples, the property of typical high wave activity detected in the lower part of cusp region.     

哨声模合声波与地球同步轨道高能电子通量增强事件事例研究

局部加速机制是磁暴期间地球外辐射带高能电子通量增强事件发生的重要原 因. 此加速机制需要两个基本条件, 一是存在种子电子, 二是存在能与种子 电子产生共振的加速波动, 包括哨声模合声波. 通过对2004-2006年 Pi1地磁脉动持续时间与种子电子通量的相关性分析, 更明确提出Pi1地磁脉 动的持续时间可以作为种子电子通量的指示剂. 通过对三个磁暴事例地球同 步轨道的种子电子通量、高能电子通量及哨声模合声波变化情况的分析, 发 现在高能电子通量较强的事例中, 均观测到较高的种子电子通量和较强的 哨声模合声波, 这在一定程度上验证了哨声模合声波对种子电子的回旋加速 机制, 且合声波强度与高能电子通量有正的相关性.      

The glow of the night ionosphere due to energetic ion beams

This paper discusses photometric measurements made of the ionospheric excitation of the line $\text{λ = 5577}\text{A}\text{?}$ at the time of electron beam injection from a rocket into the Earth's ionosphere. The gradual increase of the glow intensity per impulse occurs due to accumulation of the energy of excited states of N₂(A³Σ⁺_u) and O(′S) during their lifetimes. The large disturbed zone in the near-rocket environment (size >500 m) is connected via the interaction of ions accelerated in the rocket potential field with ionospheric components. The glow intensity modulation is observed at a height of ～98 km during the electron beam injection simultaneously with the ignition of the beam-plasma discharge (BPD). The intensity minima are explained by a decrease of the energy of accelerated ions due to effective neutralization of the rocket body by the BPD plasma. The height profile of the glow intensity revealed two maxima at heights of ～103 km and ～115 km. The second maximum (at ～115 km) indicates that, at these heights, both collision and collision-free mechanisms of accelerated ion energy transport to ionospheric components exist.     

捕获加速新生离子对Alfvén波的激发

根据准线性方程,求出了在离子持续产生并被太阳风捕获加速的情况下离子的渐近态分布函数.采用此分布函数分析了斜向传播的Alfven波的稳定性.     

Stimulation of plasma waves in the magnetosphere using satellite JIKIKEN (EXOS-B)

The stimulated plasma wave experiment (SPW) has been successfully carried out in the plasmasphere and the magnetosphere along the JIKIKEN (EXOS-B) satellite orbit where the plasma parameters indicate wide variety of the combination of the electron number density, ranging from 1/cc to 10⁴/cc, and the electron cyclotron frequency, ranging from 6 kHz to 200 kHz.The upper hybrid resonances F_UHR usually persists for long periods up to 125 msec and the electron cyclotron resonances nF_H are stimulated at frequencies with the very high harmonic number n; sometimes, the nF_H resonance takes place for n=47.All the features of the resonances including F_On reflect the characteristics of the magnetospheric plasma that contains the energetic and non-Maxwellian components of the particles. The measurement of the plasma resonance contributes to the detection of the local electron density and the magnetic field intensity. The mode of the propagating radio waves is also determined being compared with the observed local plasma resonance frequency F_p.     

2010年4月地球同步轨道相对论电子增强事件分析

为研究2010年4月地球同步轨道相对论电子通量异常增强事件的原因, 选取了2004-2010年之间高速太阳风下7个类似事件进行对比分析. 探讨了多种可能导致此次异常事件的太阳风和地磁条件. 结果表明, 较弱的磁暴使得相对论电子高通量区域更接近同步轨道, 此外, 哨声波加速很可能在2010年4月地球同步轨道相对论电子通量异常增强事件中起到重要作用. 磁暴强度与种子电子的注入深度密切相关, 表现为Dst指数曲线的形态与能量为30～100keV的电子高通量区域的下边缘高度吻合. 能量为30～100keV电子的注入深度影响了能量大于300keV的电子出现的磁层区域. 此事件中, 由于磁暴相对较弱, 种子电子向内磁层注入的深度较浅, 更靠近同步轨道区域, 这使得相对论电子大量出现的区域也靠近同步轨道, 最终导致同步轨道相对论电子通量异常增强. 另外, 2010年4月地球同步轨道相对论电子通量异常增强事件中, 高强度的亚暴提供了充足的种子电子并加强了波粒相互作用, 这也是相对论电子增强的必要条件.      

磁层中哨声波与电子的相互作用

哨声波与磁层中电子的非线性相互作用,导致电子投掷角降低,沉降到低电离层,引起局部电离增强,而诱发Trimpi效应。本文讨论波-粒子相互作用的过程,并利用超粒子法进行了计算机模拟。计算结果指出共振不仅与电子的速度有关,而且与电子初始拉莫尔相位角有关;计算得到了相互作用时共振电子相位聚焦效应、非共振电子相位聚束效应及电子速度-相位空间中的不均匀振荡等一些结果。同时,也给出了波-电子相互作用引起的沉降电子能量通量随时间的变化和沉降电子的能量分布。      

从空间飞行器入射进电离层的调制电子束产生的高频波辐射

在主动束-等离子体试验中,调制电子束从空间飞行器入射进电离层等离子体将会产生电磁波辐射,在不同试验条件下电磁波辐射机理也不一样,由电子束纵向约束性产生电磁波辐射是其中之一.对半无界稀薄调制电子束从空间飞行器入射进电离层等离子体时所产生的波现象进行了理论分析和数值计算.结果表明,当调制电子束沿磁力线入射时,会在电离层等离子体中产生高频电磁波辐射,该辐射主要集中在垂直于入射电子束运动方向的平面内.      

无碰撞电流片哨声波不稳定性

通过数值求解文献[4]中物理模型A得到的一般形式的色散关系,讨论了无碰撞电流片低频波不稳定性问题.结果表明,哨声波能被无碰撞电流片直接激发.在中性片上(z/di=0),在较宽的波数范围内,斜哨声波是可以传播的,但它基本上是稳定的.在离子惯性区内(z/di<1,电子惯性区外),斜传播的哨声波是不稳定的.在离子惯性区边缘(z/di=1),斜传播的哨声波仍然是不稳定的,增长率更大,不稳定的波频率范围更高.此外,朝向中性片方向传播(kzdi<0)的哨声波比离开中性片方向传播(kzdi>0)的哨声波有更大的增长率.     

Spatial coherence and electromagnetic wave generation during electron beam experiments in space

A two-dimensional electromagnetic simulation model is used to investigate the production of whistler waves in connection with electron beam experiments in space. The spectrum is observed to peak near 0.7 ω_e, and the conversion efficiency of beam energy to whistler waves is about 5 × 10⁻⁵. The whistlers can be trapped in a density trough extending out from the spacecraft and experience ducted propagation.     

Electron beams and their interactions with the ionosphere — A review of the E| |B series

A review is presented of results from a series of experiments which began with an attempt to reflect electrons from the potential change which is thought to generate the aurora. In order to understand the experiment, this series then expanded to study beam-plasma interactions in the laboratory as well as in the ionosphere. Results from the electron reflection experiment, as well as in situ and ground-based observations of the waves generated by beam-plasma interactions will be reviewed. Measurements bearing on modifications of the ambient plasma by the beam-emitting rocket will be presented.     

Identification of seismic activity sources on the subsatellite track by ionospheric plasma disturbances detected with the Sich-2 onboard probes

Using a cylindrical Langmuir probe and the authors’ proprietary two-channel pressure transducer, ionospheric plasma parameter distributions along the orbit of the Sich-2 satellite (Ukraine, 2011–2012) were measured. This paper is concerned with identifying the space–time location of ionospheric plasma disturbance sources, including the epicenters of actual earthquakes (before or during the satellite flyover) and incipient earthquakes on the subsatellite track, from the measured distributions of the electron density and temperature and the neutral particle temperature along the satellite orbit. To do this, the measured ionospheric plasma parameter distributions are connected to the coordinates on the subsatellite track.It is shown that local disturbances in the electron density and temperature and neutral particle temperature distributions in the satellite orbit in the ionosphere may serve as indicators of seismic activity on the subsatellite track. The epicenters of incipient earthquakes may be set off from other plasma parameter disturbance sources associated with seismic activity using information provided by special monitoring and survey centers that monitor the current seismic situation.     

An empirical model of electron density in low latitude at 600 km obtained by Hinotori satellite

An empirical model of electron density (Ne) was constructed by using the data obtained with an impedance probe on board Japanese Hinotori satellite. The satellite was in circular orbit of the height of 600 km with the inclination of 31 degrees from February 1981 to June 1982. The constructed model gives Ne at any local time with the time resolution of 90 min and between −25 and 25 degrees in magnetic latitude with its resolution of 5 degrees in the range of F_10.7 from 150 to 250 under the condition of K_p < 4. Spline interpolations are applied to the functions of day of year, geomagnetic latitude and solar local time, and linear interpolation is applied to the function of F_10.7. Longitude dependence of Ne is not taken into account. Our density model can reproduce solar local time variation of electron density at 600 km altitude better than current International Reference Ionosphere (IRI2001) model which overestimates Ne in night time and underestimates Ne in day time. Our density model together with electron temperature model which has been constructed before will enable more understanding of upper ionospheric phenomenon in the equatorial region.     

Electron beam experiments in Japanese satellites and rockets

Electron beam experiments in space that have been done and planned in Japan are reviewed. 200eV, 1mA electron beam is emitted from a satellite and several types of wave excitation such as UHF and ω_ce have been observed. The satellite potential and the energy spectrum of returning electrons are measured by Langmuir probes and electrostatic energy analyser. In rocket experiments of K-10-11, K-10-12, K-9M-57, K-9M-58, K-9M-61 and K-9M-66, several types of electron guns were used whose power ranges from 1mW to 1KW. The rocket potential was measured by Langmuir probes and floating probes and optical line emission measurement and wave measurements were also done. The rocket potential was not so high as expected from the balance with ionospheric plasma but strongly affected by the plasma production by the emitted electron beam and return electrons.     

哨声模波通过低纬电离层传播的某些特征

本文采用IGRF(1980)模型进行了哨声模三维射线跟踪计算, 研究了夜间哨声通过低纬电离层传播的射线与波法的特征.着重讨论了形成非导管哨声可透射路径的条件、射线的聚焦效应及射线的低纬截止.数值计算得到路径终纬度截止约在倾角纬度10.7°N.      

调制电子束弛豫长度对哨声波辐射的影响

在发射调制电子束的主动空间试验中,电子束与背景等离子体的线性和非线性相互作用将产生哨声波辐射.影响辐射特性的因素很多,调制电子束的弛豫长度是其中一个重要因素.本文研究了呈指数衰减的调制电子束弛豫长度对电子束产生的哨声波辐射特性的影响.结果表明,当电子束弛豫长度与背景等离子体非均匀特征尺度相当时,有利于提高调制电子束产生的波辐射强度.      

Study of VLF wave with relativistic effect in Saturn magnetosphere in the presence of parallel A.C. electric field

Cassini radio and plasma wave surveys aim to study radio emissions, plasma waves, thermal plasma and dust near Saturn. Using the characteristic solution and dynamics method, the influence of electron beam on the loss cone and bi-Maxwellian distribution of whistler mode waves in the parallel alternating electric field and magnetic field is studied. The dispersion relation and the growth rate of Saturn's magnetic layer were deduced and calculated in detail. Parameter analysis is performed by changing the parameters of the plasma like number density, AC frequency, temperature anisotropy, etc. The influence of AC frequency on Doppler shift and the comparative study of growth rate of oblique and parallel propagating waves are analyzed using generalized distribution function. We found temperature anisotropy ${\text{A}}_{\text{T}}=1.25$ can explain the linear spatiotemporal growth rate of whistler mode waves. It provides the majority of the observed frequency integral power. It can be seen that the effective parameters for the generation of Whistler mode waves are not only temperature anisotropy, but also the relativistic factors discussed in the results and discussion section, and the AC field frequency and width of the loss cone distribution function.