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501.
The Energetic Particle and Plasma Spectrometer Instrument on the MESSENGER Spacecraft 总被引:1,自引:0,他引:1
G. Bruce Andrews Thomas H. Zurbuchen Barry H. Mauk Horace Malcom Lennard A. Fisk George Gloeckler George C. Ho Jeffrey S. Kelley Patrick L. Koehn Thomas W. LeFevere Stefano S. Livi Robert A. Lundgren Jim M. Raines 《Space Science Reviews》2007,131(1-4):523-556
The Energetic Particle and Plasma Spectrometer (EPPS) package on the MErcury Surface, Space ENvironment, GEochemistry, and
Ranging (MESSENGER) mission to Mercury is composed of two sensors, the Energetic Particle Spectrometer (EPS) and the Fast
Imaging Plasma Spectrometer (FIPS). EPS measures the energy, angular, and compositional distributions of the high-energy components
of the in situ electrons (>20 keV) and ions (>5 keV/nucleon), while FIPS measures the energy, angular, and compositional distributions
of the low-energy components of the ion distributions (<50 eV/charge to 20 keV/charge). Both EPS and FIPS have very small
footprints, and their combined mass (∼3 kg) is significantly lower than that of comparable instruments. 相似文献
502.
T. Tanaka 《Space Science Reviews》2007,133(1-4):1-72
Convection is the most fundamental process in understanding the structure of geospace and disturbances observed in the magnetosphere–ionosphere
(M–I) system. In this paper, a self-consistent configuration of the global convection system is considered under the real
topology as a compound system. Investigations are made based on the M–I coupling scheme by analyzing numerical results obtained
from magnetohydrodynamic (MHD) simulations which guarantee the self-consistency in the whole system under the Bv (magnetic field and velocity) paradigm. It is emphasized in the M–I coupling scheme that convection and field-aligned current
(FAC) are different aspects of same physical process characterizing the open magnetosphere. Special attention is given in
this paper to the energy supplying (dynamo) process that drives the FAC system. In the convection system, the dynamo must
be constructed from shear motion together with plasma population regimes to steadily drive the convection. Convection patterns
observed in the ionosphere are also the manifestation of achievement in global self-consistency. A primary approach to apply
these concepts to the study of geospace is to consider how the M–I system adjusts the relative motion between the compressible
magnetosphere and the incompressible ionosphere when responding to given solar-wind conditions. The above principle is also
applicable for the study of disturbance phenomena such as the substorm as well as for the study of apparently unique processes
such as the flux transfer event (FTE), the sudden commencement (SC), and the theta aurora. Finally, an attempt is made to
understand the substorm as the extension of enhanced convection under the southward interplanetary magnetic field (IMF) condition. 相似文献
503.
为解决微波等离子推力器全系统在真空中进行实验,减少不必要的能量损失,利用开关电源、衰减器和检波器一体化设计技术和液体冷却技术,通过解决微波电子器件在真空中的放电问题,研制出可在大气与真空环境中工作的体积小和质量轻的微波等离子推力器微波源,其输出和反射微波功率可根据磁控管的阳极电流和检波器的输出电压进行测量。对微波源进行调试的结果说明:微波输出功率稳定,和现有同类设备相比,性能得到大幅度提高。配合推力器腔体,在地面和真空下对微波源进行的实验说明,微波源能可靠地工作在地面和真空环境中。 相似文献
504.
505.
为了研究同轴谐振腔内导体的头部形状、位置对腔内电磁场分布的影响规律,用时域有限差分法(FDID)对微波等离子推力器(MPT)TEM谐振模式的同轴谐振腔中的电磁场进行了数值模拟,并结合实验现象对数值模拟的结果进行了分析讨论。结果表明,内导体头部形状的改变,改变了同轴腔内电磁场的分布规律和电场强度最大集中区域的位置。内导体位置的改变,只改变电磁场强度的大小,且内导体愈接近同轴腔的底面(即:放电间隙δ愈小),腔内电场强度愈强。同时,锥形头部的内导体,更有利于MPT的启动和稳定工作,为采用同轴谐振腔的MPT工程样机的研制提供了依据。 相似文献
506.
Two central issues in magnetospheric research are understanding the mapping of the low-altitude ionosphere to the distant regions of the magnetsphere, and understanding the relationship between the small-scale features detected in the various regions of the ionosphere and the global properties of the magnetosphere. The high-latitude ionosphere, through its magnetic connection to the outer magnetosphere, provides an important view of magnetospheric boundaries and the physical processes occurring there. All physical manifestations of this magnetic connectivity (waves, particle precipitation, etc.), however, have non-zero propagation times during which they are convected by the large-scale magnetospheric electric field, with phenomena undergoing different convection distances depending on their propagation times. Identification of the ionospheric signatures of magnetospheric regions and phenomena, therefore, can be difficult. Considerable progress has recently been made in identifying these convection signatures in data from low- and high-altitude satellites. This work has allowed us to learn much about issues such as: the rates of magnetic reconnection, both at the dayside magnetopause and in the magnetotail; particle transport across the open magnetopause; and particle acceleration at the magnetopause and the magnetotail current sheets. 相似文献
507.
Energetic (0.1-16 keV/e) ion data from a plasma composition experiment on the ISEE-1 spacecraft show that Earth's plasma sheet (inside of 23 RE) always has a large population of H+ and He++ ions, the two principal ionic components of the solar wind. This population is the largest, in terms of both number density and spatial thickness, during extended periods of northward interplanetary magnetic field (IMF) and is then also the most "solar wind-like" in the sense that the He++/H+ density ratio is at its peak (about 3% on average in 1978 and 79) and the H+ and He++ have mean (thermal) energies that are in the ratio of about 1:4 and barely exceed the typical bulk flow energy in the solar wind. During geomagnetically active times, associated with southward turnings of the IMF, the H+ and He++ are heated in the central plasma sheet, and reduced in density. Even when the IMF is southward, these ions can be found with lower solar wind-like energies closer to the tail lobes, at least during plasma sheet thinning in the early phase of substorms, when they are often seen to flow tailward, approximately along the magnetic field, at a slow to moderate speed (of order 100 km s-1 or less). These tailward flows, combined with the large density and generally solar wind-like energies of plasma sheet H+ and He++ ions during times of northward IMF, are interpreted to mean that the solar wind enters along the tail flanks, in a region between the lobes and the central plasma sheet, propelled inward by ExB drift associated with the electric fringe field of the low latitude magnetopause boundary layer (LLBL). In order to complete this scenario, it is argued that the rapid (of order 1000 km s-1) earthward ion flows (mostly H+ ions), also along the magnetic field, that are more typically the precursors of plasma sheet "recovery" during substorm expansion, are not proof of solar wind entry in the distant tail, but may instead be a time-of-flight effect associated with plasma sheet redistribution in a dipolarizing magnetic field. 相似文献
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