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Y. Futaana S. Barabash A. Grigoriev D. Winningham R. Frahm M. Yamauchi R. Lundin 《Space Science Reviews》2006,126(1-4):315-332
As a part of the global plasma environment study of Mars and its response to the solar wind, we have analyzed a peculiar case
of the subsolar energetic neutral atom (ENA) jet observed on June 7, 2004 by the Neutral Particle Detector (NPD) on board
the Mars Express satellite. The “subsolar ENA jet” is generated by the interaction between the solar wind and the Martian
exosphere, and is one of the most intense sources of ENA flux observed in the vicinity of Mars. On June 7, 2004 (orbit 485
of Mars Express), the NPD observed a very intense subsolar ENA jet, which then abruptly decreased within ∼10 sec followed
by quasi-periodic (∼1 min) flux variations. Simultaneously, the plasma sensors detected a solar wind structure, which was
most likely an interplanetary shock surface. The abrupt decrease of the ENA flux and the quasi-periodic flux variations can
be understood in the framework of the global response of the Martian plasma obstacle to the interplanetary shock. The generation
region of the subsolar ENA jet was pushed towards the planet by the interplanetary shock; and therefore, Mars Express went
out of the ENA jet region. Associated global vibrations of the Martian plasma obstacle may have been the cause of the quasi-periodic
flux variations of the ENA flux at the spacecraft location. 相似文献
2.
Yoshifumi Futaana Jean-Yves Chaufray H. Todd Smith Philippe Garnier Herbert Lichtenegger Magda Delva Hannes Gr?ller Alessandro Mura 《Space Science Reviews》2011,162(1-4):213-266
Our understanding of the upper atmosphere of unmagnetized bodies such as Mars, Venus and Titan has improved significantly in this decade. Recent observations by in situ and remote sensing instruments on board Mars Express, Venus Express and Cassini have revealed characteristics of the neutral upper atmospheres (exospheres) and of energetic neutral atoms (ENAs). The ENA environment in the vicinity of the bodies is by itself a significant study field, but ENAs are also used as a diagnostic tool for the exosphere and the interaction with the upstream plasmas. Synergy between theoretical and modeling work has also improved considerably. In this review, we summarize the recent progress of our understanding of the neutral environment in the vicinity of unmagnetized planets. 相似文献
3.
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
4.
M. Yamauchi Y. Futaana A. Fedorov E. Dubinin R. Lundin J.-A. Sauvaud D. Winningham R. Frahm S. Barabash M. Holmstrom J. Woch M. Fraenz E. Budnik H. Borg J. R. Sharber A. J. Coates Y. Soobiah H. Koskinen E. Kallio K. Asamura H. Hayakawa C. Curtis K. C. Hsieh B. R. Sandel M. Grande A. Grigoriev P. Wurz S. Orsini P. Brandt S. Mckenna-Lawler J. Kozyra J. Luhmann 《Space Science Reviews》2006,126(1-4):239-266
Although the Mars Express (MEX) does not carry a magnetometer, it is in principle possible to derive the interplanetary magnetic
field (IMF) orientation from the three dimensional velocity distribution of pick-up ions measured by the Ion Mass Analyser
(IMA) on board MEX because pick-up ions' orbits, in velocity phase space, are expected to gyrate around the IMF when the IMF
is relatively uniform on a scale larger than the proton gyroradius. During bow shock outbound crossings, MEX often observed
cycloid distributions (two dimensional partial ring distributions in velocity phase space) of protons in a narrow channel
of the IMA detector (only one azimuth for many polar angles). We show two such examples. Three different methods are used
to derive the IMF orientation from the observed cycloid distributions. One method is intuitive (intuitive method), while the
others derive the minimum variance direction of the velocity vectors for the observed ring ions. These velocity vectors are
selected either manually (manual method) or automatically using simple filters (automatic method). While the intuitive method
and the manual method provide similar IMF orientations by which the observed cycloid distribution is well arranged into a
partial circle (representing gyration) and constant parallel velocity, the automatic method failed to arrange the data to
the degree of the manual method, yielding about a 30° offset in the estimated IMF direction. The uncertainty of the derived
IMF orientation is strongly affected by the instrument resolution. The source population for these ring distributions is most
likely newly ionized hydrogen atoms, which are picked up by the solar wind. 相似文献
5.
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
6.
Yuichiro Ezoe Kumi Ishikawa Takaya Ohashi Noriko Y. Yamasaki Kazuhisa Mitsuda Ryuichi Fujimoto Yoshizumi Miyoshi Naoki Terada Yasunobu Uchiyama Yoshifumi Futaana 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Recent results of solar system planets observed with the Japanese X-ray astronomy satellite Suzaku are reviewed. Thanks to the low instrumental background and good energy resolution, X-ray CCDs onboard Suzaku are one of the best probes to study diffuse X-ray emission. An overview of the Suzaku data of Jupiter and Earth is presented, along with preliminary results of Mars. Firstly, diffuse hard X-ray emission is discovered in 1–5 keV at Jovian radiation belts. Its spectrum is represented by a power-law continuum with a photon index of ∼1.4. This emission could originate from inverse-Compton scattering of solar photons by tens MeV electrons. Secondly, variable diffuse soft X-rays are serendipitously found during observations in the directions of the north ecliptic pole and galactic ridge. Good time correlations with the solar wind and emission lines found in the X-ray spectra are firm evidences of a solar wind charge exchange emission with Earth’s exosphere. Thirdly, diffuse X-ray emission from Martian exosphere via the solar wind charge exchange is investigated for the first time at solar minimum. A stringent upper limit on the density of the Martian exosphere is placed from the Suzaku data. 相似文献
7.
Takeshi Imamura Takahiro Iwata Zen-ichi Yamamoto Nanako Mochizuki Yusuke Kono Koji Matsumoto Qinghui Liu Hirotomo Noda Hideo Hanada Koh-ichiro Oyama Alexander Nabatov Yoshifumi Futaana Akinori Saito Hiroki Ando 《Space Science Reviews》2010,154(1-4):305-316
Radio occultation observations of the electron density near the lunar surface were conducted during the SELENE (Kaguya) mission using the Vstar and Rstar sub-satellites. Previous radio occultation measurements conducted in the Soviet lunar missions have indicated the existence of an ionosphere with peak densities of several hundreds of electrons per cubic centimeters above the dayside lunar surface. These densities are difficult to explain theoretically when the removal of plasma by the solar wind is considered, and thus the generation mechanism of the lunar ionosphere is a major issue, with even the validity of previous observations still under debate. The most serious error source in the measurement is the fluctuation of the terrestrial ionosphere which also exists along the ray path. To cope with this difficulty, about 400 observations were conducted using Vstar to enable statistical analysis of the weak signal of the lunar ionosphere. Another method is to utilize Vstar and Rstar with the second one being used to measure the terrestrial ionosphere contribution. The observations will establish the morphology of the lunar ionosphere and will reveal its relationship with various conditions to provide possible clues to the mechanism. 相似文献
8.
Yasuhiro Morita Junichiro Kawaguchi Yoshifumi Inatani Takashi Abe Hirokazu Nagai 《Acta Astronautica》2003,53(12):282-981
Despite huge amount of data collected by the previous interplanetary spacecraft and probes, the origin and evolution of the solar system still remains unveiled due to limited information they brought back. Thus, the Institute of Space and Astronautical Science (ISAS) of Japan has been given a commitment to pave the way to an asteroid sample return mission: the MUSES-C project. A key to success is considered the reentry with hyperbolic velocity, which has not ever been demonstrated as yet. With this as background, a demonstrator of atmospheric reentry system, DASH, has been designed to demonstrate the high-speed reentry technology as a GTO piggyback mission. The capsule, identical to that of the sample return mission, can experience the targeted level of thermal environment even from the GTO by tracing a specially designed reentry trajectory. After the purpose of the mission was outlined at the last IAF symposium, the final fitting tests have been conducted in the ISAS Sagamihara Campus involving the flight model hardware. Furthermore, a series of rehearsals for recovery have been already executed. The paper describes the current mission status of the project. 相似文献
9.
The Neutral Particle Detector (NPD) of the ASPERA-3 experiment (Analyser of Space Plasmas and Energetic Atoms) on board the
Mars Express (MEX) spacecraft observed an intense flux of H ENAs (energetic neutral atoms) with average energy of about 1.5
keV emitted anisotropically from the subsolar region of Mars. The NPD detected the ENA jet near the bow shock at radial distances
of about 1 R
M from the Martian surface as the spacecraft moved outbound, while the NPD continuously pointed towards the subsolar region.
The jet intensity shows oscillative behavior. These intensity variations occur on two clearly distinguishable time scales.
The majority of the identified events have an average oscillation period of about 50 sec. The second group consists of events
with long-scale variations with a time scale of approximately 300 sec. The fast oscillations of the first group exhibit a periodic structure and are detected in every orbit, while the slow variations of the second group are identified in ∼40% of orbits. The intensity of the fast oscillations have a peak-to-valley ratio about 20 to 30% of the peak intensity. One of the possible mechanisms to explain
fast oscillations is the formation of the low frequency ion waves at the subsolar region of Mars. Slow variations may be explained by either temporal variations in the ENA generation source or by a specific structure of the
ENA generation source, in which hair-like ENA subjets can be present. 相似文献
10.
In-flight Performance and Initial Results of Plasma Energy Angle and Composition Experiment (PACE) on SELENE (Kaguya) 总被引:1,自引:0,他引:1
Yoshifumi Saito Shoichiro Yokota Kazushi Asamura Takaaki Tanaka Masaki N. Nishino Tadateru Yamamoto Yuta Terakawa Masaki Fujimoto Hiroshi Hasegawa Hajime Hayakawa Masafumi Hirahara Masahiro Hoshino Shinobu Machida Toshifumi Mukai Tsugunobu Nagai Tsutomu Nagatsuma Tomoko Nakagawa Masato Nakamura Koh-ichiro Oyama Eiichi Sagawa Susumu Sasaki Kanako Seki Iku Shinohara Toshio Terasawa Hideo Tsunakawa Hidetoshi Shibuya Masaki Matsushima Hisayoshi Shimizu Futoshi Takahashi 《Space Science Reviews》2010,154(1-4):265-303
MAP-PACE (MAgnetic field and Plasma experiment—Plasma energy Angle and Composition Experiment) on SELENE (Kaguya) has completed its ~1.5-year observation of low-energy charged particles around the Moon. MAP-PACE consists of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). ESA-S1 and S2 measured the distribution function of low-energy electrons in the energy range 6 eV–9 keV and 9 eV–16 keV, respectively. IMA and IEA measured the distribution function of low-energy ions in the energy ranges 7 eV/q–28 keV/q and 7 eV/q–29 keV/q. All the sensors performed quite well as expected from the laboratory experiment carried out before launch. Since each sensor has a hemispherical field of view, two electron sensors and two ion sensors installed on the spacecraft panels opposite each other could cover the full 3-dimensional phase space of low-energy electrons and ions. One of the ion sensors IMA is an energy mass spectrometer. IMA measured mass-specific ion energy spectra that have never before been obtained at a 100 km altitude polar orbit around the Moon. The newly observed data show characteristic ion populations around the Moon. Besides the solar wind, MAP-PACE-IMA found four clearly distinguishable ion populations on the dayside of the Moon: (1) Solar wind protons backscattered at the lunar surface, (2) Solar wind protons reflected by magnetic anomalies on the lunar surface, (3) Reflected/backscattered protons picked-up by the solar wind, and (4) Ions originating from the lunar surface/lunar exosphere. 相似文献
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