排序方式: 共有39条查询结果,搜索用时 281 毫秒
11.
H. Nilsson E. Carlsson H. Gunell Y. Futaana S. Barabash R. Lundin A. Fedorov Y. Soobiah A. Coates M. Fränz E. Roussos 《Space Science Reviews》2006,126(1-4):355-372
Using data from the Mars Express Ion Mass Analyzer (IMA) we investigate the distribution of ion beams of planetary origin
and search for an influence from Mars crustal magnetic anomalies. We have concentrated on ion beams observed inside the induced
magnetosphere boundary (magnetic pile-up boundary). Some north-south asymmetry is seen in the data, but no longitudinal structure
resembling that of the crustal anomalies. Comparing the occurrence rate of ion beams with magnetic field strength at 400 km
altitude below the spacecraft (using statistical Mars Global Surveyor results) shows a decrease of the occurrence rate for
modest (< 40 nT) magnetic fields. Higher magnetic field regions (above 40 nT at 400 km) are sampled so seldom that the statistics
are poor but the data is consistent with some ion outflow events being closely associated with the stronger anomalies. This
ion flow does not significantly affect the overall distribution of ion beams around Mars. 相似文献
12.
H. Nilsson R. Lundin K. Lundin S. Barabash H. Borg O. Norberg A. Fedorov J.-A Sauvaud H. Koskinen E. Kallio P. Riihelä J. L. Burch 《Space Science Reviews》2007,128(1-4):671-695
The Ion Composition Analyzer (ICA) is part of the Rosetta Plasma Consortium (RPC). ICA is designed to measure the three-dimensional
distribution function of positive ions in order to study the interaction between the solar wind and cometary particles. The
instrument has a mass resolution high enough to resolve the major species such as protons, helium, oxygen, molecular ions,
and heavy ions characteristic of dusty plasma regions. ICA consists of an electrostatic acceptance angle filter, an electrostatic
energy filter, and a magnetic momentum filter. Particles are detected using large diameter (100 mm) microchannel plates and
a two-dimensional anode system. ICA has its own processor for data reduction/compression and formatting. The energy range
of the instrument is from 25 eV to 40 keV and an angular field-of-view of 360° × 90° is achieved through electrostatic deflection
of incoming particles. 相似文献
13.
L. Eliasson O. Norberg R. Lundin K. Lundin S. Olsen H. Borg M. André H. Koskinen P. Riihelä M. Boehm B. Whalen 《Space Science Reviews》1994,70(3-4):563-576
The Hot Plasma Experiment, F3H, on boardFreja is designed to measure auroral particle distribution functions with very high temporal and spatial resolution. The experiment consists of three different units; an electron spectrometer that measures angular and energy distributions simultaneously, a positive ion spectrometer that is using the spacecraft spin for three-dimensional measurements, and a data processing unit. The main scientific objective is to study positive ion heating perpendicular to the magnetic field lines in the auroral region. The high resolution measurements of different positive ion species and electrons have already provided important information on this process as well as on other processes at high latitudes. This includes for example high resolution observations of auroral particle precipitation features and source regions of positive ions during magnetic disturbances. TheFreja orbit with an inclination of 63° allows us to make detailed measurements in the nightside auroral oval during all disturbance levels. In the dayside, the cusp region is covered during magnetic disturbances. We will here present the instrument in some detail and some outstanding features in the particle data obtained during the first months of operation at altitudes around 1700 km in the northern hemisphere auroral region. 相似文献
14.
Space Science Reviews - The magnetopause and its inner contact region with the magnetosphere, the magnetosphere boundary layer, constitute the interface between the shocked solar wind plasma and... 相似文献
15.
Rickard Lundin 《Space Science Reviews》2011,162(1-4):309-334
Solar wind forcing of Mars and Venus results in outflow and escape of ionospheric ions. Observations show that the replenishment of ionospheric ions starts in the dayside at low altitudes (??300?C800 km), ions moving at a low velocity (5?C10 km/s) in the direction of the external/ magnetosheath flow. At high altitudes, in the inner magnetosheath and in the central tail, ions may be accelerated up to keV energies. However, the dominating energization and outflow process, applicable for the inner magnetosphere of Mars and Venus, leads to outflow at energies ??5?C20 eV. The aim of this overview is to analyze ion acceleration processes associated with the outflow and escape of ionospheric ions from Mars and Venus. Qualitatively, ion acceleration may be divided in two categories:
- Modest ion acceleration, leading to bulk outflow and/or return flow (circulation).
- Acceleration to well over escape velocity, up into the keV range.
16.
Energisation of O+ and O+
2 Ions at Mars: An Analysis of a 3-D Quasi-Neutral Hybrid Model Simulation
E. Kallio A. Fedorov S. Barabash P. Janhunen H. Koskinen W. Schmidt R. Lundin H. Gunell M. Holmström Y. Futaana M. Yamauchi A. Grigoriev J. D. Winningham R. Frahm J. R. Sharber 《Space Science Reviews》2006,126(1-4):39-62
We have studied the loss of O+ and O+
2 ions at Mars with a numerical model. In our quasi-neutral hybrid model ions (H+, He++, O+, O+
2) are treated as particles while electrons form a massless charge-neutralising fluid. The employed model version does not
include the Martian magnetic field resulting from the crustal magnetic anomalies. In this study we focus the Martian nightside
where the ASPERA instrument on the Phobos-2 spacecraft and recently the ASPERA-3 instruments on the Mars Express spacecraft
have measured the proprieties of escaping atomic and molecular ions, in particular O+ and O+
2 ions. We study the ion velocity distribution and how the escaping planetary ions are distributed in the tail. We also create
similar types of energy-spectrograms from the simulation as were obtained from ASPERA-3 ion measurements. We found that the
properties of the simulated escaping planetary ions have many qualitative and quantitative similarities with the observations
made by ASPERA instruments. The general agreement with the observations suggest that acceleration of the planetary ions by
the convective electric field associated with the flowing plasma is the key acceleration mechanism for the escaping ions observed
at Mars. 相似文献
17.
Michael W. Liemohn Yingjuan Ma Rudy A. Frahm Xiaohua Fang Janet U. Kozyra Andrew F. Nagy J. David Winningham James R. Sharber Stas Barabash Rickard Lundin 《Space Science Reviews》2006,126(1-4):63-76
Atmospheric photoelectrons have been observed well above the ionosphere of Mars by the ASPERA-3 ELS instrument on Mars Express.
To systematically interpret these observations, field lines from two global MHD simulations were analyzed for connectivity
to the dayside ionosphere (allowing photoelectron escape). It is found that there is a hollow cylinder behind the planet from
1–2 R
M away from the Mars-Sun line that has a high probability of containing magnetic field lines with connectivity to the dayside
ionosphere. These results are in complete agreement with the ELS statistics. It is concluded that the high-altitude photoelectrons
are the result of direct magnetic connectivity to the dayside at the moment of the measurement, and no extra trapping or bouncing
mechanisms are needed to explain the data. 相似文献
18.
19.
J. L. Burch R. Goldstein T. E. Cravens W. C. Gibson R. N. Lundin C. J. Pollock J. D. Winningham D. T. Young 《Space Science Reviews》2007,128(1-4):697-712
The ion and electron sensor (IES) is part of the Rosetta Plasma Consortium (RPC). The IES consists of two electrostatic plasma
analyzers, one each for ions and electrons, which share a common entrance aperture. Each analyzer covers an energy/charge
range from 1 eV/e to 22 keV/e with a resolution of 4%. Electrostatic deflection is used at the entrance aperture to achieve
a field of view of 90°× 360° (2.8π sr). Angular resolution is 5°× 22.5° for electrons and 5°× 45° for ions with the sector
containing the solar wind being further segmented to 5°× 5°. The three-dimensional plasma distributions obtained by IES will
be used to investigate the interaction of the solar wind with asteroids Steins and Lutetia and the coma and nucleus of comet
67P/Churyumov–Gerasimenko (CG). In addition, photoelectron spectra obtained at these bodies will help determine their composition. 相似文献
20.
The Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) for the Mars Express Mission 总被引:1,自引:0,他引:1
S. Barabash R. Lundin H. Andersson K. Brinkfeldt A. Grigoriev H. Gunell M. Holmström M. Yamauchi K. Asamura P. Bochsler P. Wurz R. Cerulli-Irelli A. Mura A. Milillo M. Maggi S. Orsini A. J. Coates D. R. Linder D. O. Kataria C. C. Curtis K. C. Hsieh B. R. Sandel R. A. Frahm J. R. Sharber J. D. Winningham M. Grande E. Kallio H. Koskinen P. Riihelä W. Schmidt T. Säles J. U. Kozyra N. Krupp J. Woch S. Livi J. G. Luhmann S. McKenna-Lawlor E. C. Roelof D. J. Williams J.-A. Sauvaud A. Fedorov J.-J. Thocaven 《Space Science Reviews》2006,126(1-4):113-164
The general scientific objective of the ASPERA-3 experiment is to study the solar wind – atmosphere interaction and to characterize
the plasma and neutral gas environment with within the space near Mars through the use of energetic neutral atom (ENA) imaging
and measuring local ion and electron plasma. The ASPERA-3 instrument comprises four sensors: two ENA sensors, one electron
spectrometer, and one ion spectrometer. The Neutral Particle Imager (NPI) provides measurements of the integral ENA flux (0.1–60
keV) with no mass and energy resolution, but high angular resolution. The measurement principle is based on registering products
(secondary ions, sputtered neutrals, reflected neutrals) of the ENA interaction with a graphite-coated surface. The Neutral
Particle Detector (NPD) provides measurements of the ENA flux, resolving velocity (the hydrogen energy range is 0.1–10 keV)
and mass (H and O) with a coarse angular resolution. The measurement principle is based on the surface reflection technique.
The Electron Spectrometer (ELS) is a standard top-hat electrostatic analyzer in a very compact design which covers the energy
range 0.01–20 keV. These three sensors are located on a scanning platform which provides scanning through 180∘ of rotation. The instrument also contains an ion mass analyzer (IMA). Mechanically IMA is a separate unit connected by a
cable to the ASPERA-3 main unit. IMA provides ion measurements in the energy range 0.01–36 keV/charge for the main ion components
H+, He++, He+, O+, and the group of molecular ions 20–80 amu/q. ASPERA-3 also includes its own DC/DC converters and digital processing unit
(DPU). 相似文献