共查询到20条相似文献，搜索用时 15 毫秒
1.
D. L. Pasmanik V. Y. Trakhtengerts A. G. Demekhov A. A. Lyubchich E. E. Titova T. Yahnina M. J. Rycroft J. Manninen T. Turunen 《Annales Geophysicae》1998,16(3):322-330
The formation of a zone of energetic electron precipitation by the plasmapause, a region of enhanced plasma density, following energetic particle injection during a magnetic storm, is analyzed. Such a region can also be formed by detached cold plasma clouds appearing in the outer magnetosphere by restructuring of the plasmasphere during a magnetic storm. As a mechanism of precipitation, wave-particle interactions by the cyclotron instability between whistler-mode waves and electrons are considered. In the framework of the self-consistent equations of quasi-linear plasma theory, the distribution function of trapped electrons and the electron precipitation pattern are found. The theoretical results are compared with experimental data obtained from NOAA satellites. 相似文献
2.
Situations when localized precipitation of energetic (E > 30 keV) protons and electrons, associated with the development of cyclotron instability in the magnetosphere, is recorded during one satellite pass are identified in the data of particle flux observations on the NOAA-12 low-orbiting satellite. Such events were observed only in the evening sector of the magnetosphere. This precipitation is compared with the data on the cold (E < 10 eV) plasma density obtained on the LANL geostationary satellites. The comparison showed that the precipitation of energetic particles is related to the presence of cold plasma with a density of 20–100 cm?3 in geostationary orbit in the evening sector of the magnetosphere. The conclusion has been made that the localized precipitation of energetic particles is generated at the edges of small-scale structures of cold plasma, forming the so-called “plasmaspheric tail,” i.e., the cold plasma region extending from the evening plasmapause toward the Sun. 相似文献
3.
《Journal of Atmospheric and Solar》2000,62(10):889-900
The polar ionospheric X-ray imaging experiment (PIXIE) and the UV imager (UVI) onboard the Polar satellite have provided the first simultaneous global scale views of the patterns of electron precipitation through imaging of the atmospheric X-ray bremsstrahlung and the auroral UV emissions. While the UV images in the Lyman–Birge–Hopfield-long band used in this study respond to the total electron energy flux which is usually dominated by low-energy electrons (<10 keV), the PIXIE images of X-ray bremsstrahlung above ∼2.7 keV respond to electrons of energy above ∼3 keV. Comparison of precipitation features seen by UVI and PIXIE provides information on essentially complementary energy ranges of the precipitating electrons. In this study an isolated substorm is examined using data from PIXIE, UVI, ground-based measurements, and in situ measurements from high- and low-altitude satellites to obtain information about the global characteristics during the event. Results from a statistical study of isolated substorms, which has reported a significant difference in the patterns of energetic electron precipitation compared to the less energetic precipitation are confirmed. A localized maximum of electron precipitation in the morning sector delayed with respect to substorm onset is clearly seen in the X-ray aurora, and the time delay of this morning precipitation relative to substorm onset strongly indicates that this intensification is caused by electrons injected in the midnight sector drifting into a region in the dawnside magnetosphere where some mechanism effectively scatter the electrons into the loss cone. In this study, we also present the results from two low-altitude satellite passes through the region of the localized maximum of X-ray emission in the morning sector. Measured X rays are compared with X-ray fluxes calculated from the electron spectral measurements. By fitting the electron spectra by a sum of two exponentials we obtain fairly good agreement between calculated and directly measured X-ray flux profiles. 相似文献
4.
顶部电离层是低轨道卫星的运行空间,是能量粒子沉降的重要区域,认识这个空间的能量粒子分布特征对研究各种空间天气事件、地震、火山以及其他人类活动引起的扰动具有重要的现实意义.本文利用位于顶部电离层的5颗NOAA系列卫星数据,统计研究了100~300keV的电子和80~2500keV的质子的全球分布特征.研究发现:高能电子和质子主要分布在两极辐射带和南大西洋异常区,两极辐射带观测到的高能电子通量比南大西洋异常区高几倍到一个数量级,而质子则相反;高能电子在两极辐射带地区通量分布具有不对称性,主要表现为在北辐射带西经75°到东经90°存在低值区,相对应的是粒子主要聚集在其磁共轭区,且其边界和南大西洋异常区相交;高能质子两极辐射带对称分布,在南半球东经0°至东经50°存在高值区.利用概率密度统计分析发现,各颗卫星在南大西洋异常区和两极辐射带的高能电子和高能质子通量总体上均呈正态分布.在南大西洋异常区,NOAA-15观测到的高能电子通量比其他卫星的低,NOAA-16观测的高能电子通量比其他卫星的高,各卫星的高能质子观测结果基本相同.在两极辐射带,各卫星观测的高能电子通量结果基本相同,NOAA-18和NOAA-19观测的质子通量最高,NOAA-16和NOAA-17次之,NOAA-15最低,其中NOAA-19比NOAA-15观测到的质子通量要高一个数量级左右.在磁暴期间顶部电离层高能电子的变化表明地磁指数Dst和空间粒子通量变化具有时间同步性.本文的研究成果将为我国下一代电磁卫星设计提供基础依据. 相似文献
5.
Further analysis of energetic electron precipitation at the evening sector of magnetosphere is performed. In the framework of the quantitative model of cyclotron wave-particle interactions developed in the previous Pasmanik et al. paper, the case of finite spread over energies of initial energetic electron distribution is studied. The solution for distribution function of energetic electron is found. The energetic spectrum of trapped and precipitating electrons and whistler wave spectrum are analysed. 相似文献
6.
风云二号系列卫星是我国开展动态空间天气事件和空间环境监测及预警业务的重要观测平台,各系列星上均安装有高能带电粒子探测仪器开展卫星轨道空间带电粒子辐射环境连续实时的动态监测.FY2G卫星于2015年1月发射,星上采用了全新的高能粒子探测器,包括:一台高能电子探测器可监测200keV-4 MeV的高能电子,一台高能质子重离子探测器可监测4~300 MeV的高能质子,从而实现对带电粒子更宽、更精细能谱的监测.本文给出了FY2G高能带电粒子探测器在2015年1月至2015年10月期间几起典型的带电粒子动态观测结果,结合太阳和地磁活动相关参数,对高能带电粒子通量在亚暴、磁暴和太阳爆发等扰动影响下细节变化过程和特征作出了较为详细的分析描述,展现了FY2G卫星高能带电粒子探测器对轨道空间粒子环境动态变化的准确响应能力,表明观测数据可开展更加精细的轨道粒子环境评估.针对FY2G高能带电粒子探测结果进一步开展了与GOES系列卫星同期观测的比对分析,结果反映出在较小的扰动条件下多星观测到的带电粒子响应和通量变化可基本趋于一致或保持相对稳定的偏差,而扰动条件的显著变化会加大多星观测带电粒子响应和通量变化的差异,这些结果可为今后开展多星数据同化应用提供参考,也为发展磁层对扰动响应的更加复杂的图像提供了新的可能. 相似文献
7.
Regions of the detection of electromagnetic ion-cyclotron (EMIC) waves on the THEMIS satellites near the equatorial plane and the precipitation of energetic protons on POES low Earth orbiting satellites are compared with the magnetospheric magnetic field model. It is confirmed that low Earth orbiting satellites detect the precipitation of energetic protons in the regon associated with observations of EMIC waves in the magnetosphere. This is consistent with the idea that protons are scattered in the loss cone as a result of ioncyclotron interaction. Thus, observations of fluxes of energetic protons in low Earth orbits can be used to monitor ion-cyclotron instability regions in the magnetosphere. Simultaneous observations at high and low Earth orbits contribute to the construction of a spatiotemporal pattern of the interaction region of EMIC waves and energetic protons. In addition, it is shown that proton precipitation associated with EMIC waves can cause errors in determining the latitude of the isotropic boundary (the equatorial boundary of isotropic fluxes of energetic protons), which is an indicator of the configuration of the magnetic field in the magnetosphere. 相似文献
8.
Spatial structures in ionospheric electron density revealed in a tomographic image have been identified with auroral forms and related to their sources in precipitating particles observed by DMSP satellites. The observations of plasma enhancements relate to discrete auroral arcs seen in the post-noon sector, identified by both red- and green-line emissions measured by a meridional scanning photometer. The features lie within a very narrow latitudinal band on L-shells where the satellite detectors observed electron precipitation classified as from the boundary plasma sheet (BPS). The harder particles are identified with an E-region structure, while further north the precipitation is softer, resulting in a localised F-layer blob and 630.0 nm emissions. A steep gradient in plasma density represent a signature in the ionosphere of the central plasma sheet (CPS)/BPS boundary. A transition to a less-structured F-layer is found on crossing the convection reversal boundary.On leave from Artic Geophysics, University Course on Svalbard (UNIS), N-9170 Longyearbyen, Norway 相似文献
9.
A. G. Demekhov A. A. Lyubchich V. Y. Trakhtengerts E. E. Titova J. Manninen T. Turunen 《Annales Geophysicae》1998,16(11):1455-1460
We study a simple self-consistent model of a whistler cyclotron maser derived from the full set of quasi-linear equations. We employ numerical calculations to demonstrate dependencies of pulsation regimes of whistler-mode wave interactions with energetic electrons on plasma parameters. Possible temporal evolution of those regimes in real conditions is discussed; calculations are compared with case-study experimental data on energetic electron precipitation pulsations. A reasonable agreement of the model results and the observations has been found. 相似文献
10.
In this paper, we consider variations in energetic electron fluxes at a geostationary orbit, which are related to the Sun’s
rotation period, during two solar cycles. We use data on energetic electron fluxes obtained from the GOES (1986–2007) (>2
MeV) and LANL (1996–2007) (50–225 and 315–1500 keV) satellites. Within the solar cycle, we observed both periods of high flux
peak recurrence during several rotations and periods when there was no (or a low) 27-day recurrence. We show the similarity
and difference between manifestations of flux recurrences from cycle to cycle. Insignificant manifestation of recurrence and
its absence were observed mainly during the solar maximum. High electron flux recurrence was observed mainly at the phase
of decline in solar activity (near the solar minimum). We show that for both solar cycles, there were several days (within
the Bartels rotation) during which increased energetic electron fluxes would be most likely observed. 相似文献
11.
Thirteen events of high-latitude ionospheric travelling convection vortices during very quiet conditions were identified in the Greenland magnetometer data during 1990 and 1991. The latitudes of the vortex centres for these events are compared to the energetic electron trapping boundaries as identified by the particle measurements of the NOAA 10 satellite. In addition, for all events at least one close DMSP overpass was available. All but one of the 13 cases agree to an exceptional degree that: the TCV centres are located within the region of trapped, high energy electrons close to the trapping boundary for the population of electrons with energy greater than > 100 keV. Correspondingly, from the DMSP data they are located within the region of plasmasheet-type precipitation close to the CPS/BPS precipitation boundary. That is, the TCV centres map to deep inside the magnetosphere and not to the magnetopause. 相似文献
12.
L. L. Lazutin Yu. V. Gotselyuk E. A. Murav’eva I. N. Myagkova M. I. Panasyuk L. I. Starostin B. Yu. Yushkov K. Kudela N. Hasebe K. Sukurai M. Hareyama 《Geomagnetism and Aeronomy》2010,50(2):168-180
The processes of penetration, trapping, and acceleration of solar protons in the Earth’s magneto-sphere during magnetic storms in November 2004 and January 2005 are studied based on the energetic particle measurements on the CORONAS-F and SERVIS-1 satellites. Acceleration of protons by 1–2 orders of magnitude was observed after trapping of solar protons with an energy of 1–15 MeV during the recovery phase of the magnetic storm of November 7–8, 2004. This acceleration was accompanied by an earthward shift of the particle flux maximum for several days, during which the series of magnetic storms continued. The process of relativistic electron acceleration proceeded simultaneously and according to a similar scenario including acceleration of protons. At the end of this period, the intensification was terminated by the process of precipitation, and a new proton belt split with the formation of two maximums at L ～ 2 and 3. In the January 2005 series of moderate storms, solar protons were trapped at L = 3.7 during the storm of January 17–18. However, during the magnetic storm of January 21, these particles fell in the zone of quasi-trapping, or precipitated into the atmosphere, or died in the magnetosheath. At the same time, the belts that were formed in November at L ～ 2 and 3 remained unchanged. Transformations of the proton (and electron) belts during strong magnetic storms change the intensity and structure of belts for a long time. Thus, the consequences of changes during the July 2004 storm did not disappear until November disturbances. 相似文献
13.
《Journal of Atmospheric and Solar》2007,69(3):387-402
Jupiter is a planet of superlatives: the most massive planet in the solar system, rotates the fastest, has the strongest magnetic field, and has the most massive satellite system of any planet. These unique properties lead to volcanoes on Io and a population of energetic plasma trapped in the magnetic field that provides a physical link between the satellites, particularly Io, and the planet Jupiter. There are strong differences between the magnetospheres of Earth and Jupiter but there are also underlying basic physical principles that all magnetospheres share in common. This paper provides a rough sketch of the magnetosphere of Jupiter, briefly describes the current understanding and lists outstanding issues. As at Earth, a major issue of the jovian system is how the magnetospheric plasma is coupled to the planet's ionosphere. 相似文献
14.
V. V. Khegay K. W. Min H. J. Kim J. Park J. J. Lee V. P. Kim 《Geomagnetism and Aeronomy》2008,48(5):615-621
The structure of the electron density horizontal distribution at heights of the topside ionosphere in the Northern Hemisphere under quiet magnetic conditions in the polar peak region has been analyzed based on the measurements conducted on board the STSAT-1, DMSP F13, and DMSP F15 satellites during the period of moderate solar activity. The sector near 1000 MLT (magnetic local time) for the spring equinox season has been studied most thoroughly. It has been obtained that the polar peak consists of localized irregularities in the electron density of a specific form, inside which the electron density exceeds its background values by several tens of percent. The characteristic dimensions of the irregularities vary from a few degrees to several tens of degrees in the meridional and zonal directions, respectively. The irregularities are centered along the dayside boundary of the polar cap and coincide with the region of “soft” electron precipitation (with the average energy lower than 500 eV and with the flux density above 107 electrons cm?2 s?1 sr?1). 相似文献
15.
We follow the electron precipitation characteristics on and nearby a preonset arc using the high resolution Freja TESP instrument. Our data coverage extends from about 10 min before onset up to 1 min before onset. The arc is the most equatorward one (around MLAT 62°) of a system of growth phase arcs, and it was close to the radiation belt precipitation. Within the preonset arc, inverted-V type precipitation dominates. Poleward of the arc we also find some precipitation regions, and here there is systematically a cold electron population superposed with a warm population. Using single and double Maxwellian fits to the measured electron spectra we find the ionosphere-magnetosphere coupling parameters (field-aligned conductance K and the parallel potential drop V) as well as the effective source plasma properties (density and temperature) during the event. Compared to typical expansion phase features, the preonset parallel potential drop is smaller by a factor of ten, the electron temperature is smaller by a factor of at least five, and the field-aligned conductance is about the same or larger. The fact that there are two isotropic superposed electron populations on the poleward side of the preonset arc suggests that the distance between warm trapped electrons on dipolar field lines and colder electrons on open field lines has become so small near the onset that mixing e.g. due to finite electron Larmor radius effects can take place. 相似文献
16.
In an incoherent scattering radar experiment, the spectral measurement of the so-called up- and downshifted electron plasma lines provides information about their intensity and their Doppler frequency. These two spectral lines correspond, in the backscatter geometry, to two Langmuir waves travelling towards and away from the radar. In the daytime ionosphere, the presence of a small percentage of photoelectrons produced by the solar EUV of the total electron population can excite or damp these Langmuir waves above the thermal equilibrium, resulting in an enhancement of the intensity of the lines above the thermal level. The presence of photo-electrons also modifies the dielectric response function of the plasma from the Maxwellian and thus influences the Doppler frequency of the plasma lines. In this paper, we present a high time-resolution plasma-line data set collected on the EISCAT VHF radar. The analysed data are compared with a model that includes the effect of a suprathermal electron population calculated by a transport code. By comparing the intensity of the analysed plasma lines data to our model, we show that two sharp peaks in the electron suprathermal distribution in the energy range 20–30 eV causes an increased Landau damping around 24.25 eV and 26.25 eV. We have identified these two sharp peaks as the effect of the photoionisation of N2 and O by the intense flux of monochromatic HeII radiation of wavelength 30.378 nm (40.812 eV) created in the chromospheric network and coronal holes. Furthermore, we see that what would have been interpreted as a mean Doppler drift veloCity for a Maxwellian plasma is actually a shift of the Doppler frequency of the plasma lines due to suprathermal electrons. 相似文献
17.
《Journal of Atmospheric and Solar》2007,69(14):1690-1706
This brief review summarizes recent findings related to particle precipitation associated with electromagnetic ion–cyclotron (EMIC) waves seen on the ground as geomagnetic Pc1 and IPDP pulsations.Particle precipitation signatures of ion–cyclotron interaction are described as revealed from low-altitude satellite measurements of the energetic proton fluxes as well as from observations of the proton aurora. As a result, localized proton precipitation patterns situated equatorward of the isotropy boundary are disclosed. One of the patterns is a proton precipitation spot in the morning sector, presumably mapped onto plasmapause; another one is an elongated region of the precipitation, presumably mapped onto the plasmaspheric plume.Clear evidence of the pitch-angle scattering associated with the ion–cyclotron wave activity is found near the equatorial plane in the region conjugated with the localized proton precipitation at low altitude.Thus, the revealed precipitation patterns determine the location of the region of intense pitch-angle scattering of energetic protons, and, therefore, their observations can be used to monitor the region of the ion–cyclotron interaction and to study its origin and properties. Some examples of such application of the low-altitude observations of energetic particles are described. 相似文献
18.
M. Cyamukungu C. Lippens L. Adams R. Nickson C. Boeder V. Pierrard E. Daly Gh. Grégoire J. Lemaire 《Annales Geophysicae》1999,17(12):1622-1625
On the basis of the currents induced by electron fluxes in the Scintillating Fibre Detector (SFD) onboard the EQUATOR-S satellite launched on 2 December 1997, an in-situ acceleration of radiation belt electrons is found to possibly contribute to the increase of the flux of electrons with energies greater than 400 keV. The data acquired between 16 December 1997 and 30 April 1998 on the 500–67300 km, 4° inclination EQUATOR-S orbit show that the increase of the energetic electron flux corresponds to the enhanced geomagnetic activity measured through the Dst index. 相似文献
19.
A. Belehaki E. T. Sarris G. Tsiropoula R. W. McEntire S. Kokubun T. Yamamoto 《Annales Geophysicae》1997,15(12):1515-1531
Geotail energetic particle, magnetic field data and plasma observations (EPIC, MGF and CPI experiments) have been examined for a number of energetic particle bursts in the distant tail (120Re < |XGSM| < 130 Re), associated with moving magnetic field structures, following substorm onsets. The features obtained from this data analysis are consistent with the distant magnetotail dynamics determined first by ISEE3 observations and explained in terms of the neutral line model. At the onset of the bursts, before plasma sheet entrance, energetic electrons appear as a field-aligned beam flowing in the tailward direction, followed by anisotro-pic ions. Within the flux rope region, suprathermal ions exhibit a convective anisotropy, which allows determination of the plasma flow velocity, assuming that the anisotropy arises from the Compton-Getting effect. The velocities thus determined in the plasma sheet are estimated to be 200–650 km/s, and compare favourably with the velocities derived from the CPI electron and proton experiment. The estimated length of magnetic field structures varies between 28 and 56 Re and depends on the strength of the westward electrojet intensification. Finally, the three structures reported here show clear magnetic field signatures of flux rope topology. The existence of a strong magnetic field aligned approximately along the Y-axis and centred on the north-to-south excursion of the field, and the bipolar signature in both By and/or Bz components, is consistent with the existence of closed field lines extending from Earth and wrapping around the core of the flux rope structure. 相似文献