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1.
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.
A. Galli P. Wurz H. Lammer H. I. M. Lichtenegger R. Lundin S. Barabash A. Grigoriev M. Holmström H. Gunell 《Space Science Reviews》2006,126(1-4):447-467
We have evaluated the Lyman-α limb emission from the exospheric hydrogen of Mars measured by the neutral particle detector of the ASPERA-3 instrument on Mars Express in 2004 at low solar activity (solar activity index = 42, F10.7=100). We derive estimates for the hydrogen exobase density, n H = 1010 m?3, and for the apparent temperature, T > 600 K. We conclude that the limb emission measurement is dominated by a hydrogen component that is considerably hotter than the bulk temperature at the exobase. The derived values for the exosphere density and temperature are compared with similar measurements done by the Mariner space probes in the 1969. The values found with Mars Express and Mariner data are brought in a broader context of exosphere models including the possibility of having two hydrogen components in the Martian exosphere. The present observation of the Martian hydrogen exosphere is the first one at high altitudes during low solar activity, and shows that for low solar activity exospheric densities are not higher than for high solar activity. 相似文献
3.
D. Abplanalp P. Wurz L. Huber I. Leya E. Kopp U. Rohner M. Wieser L. Kalla S. Barabash 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009,44(7):870-878
The Polar Balloon Atmospheric Composition Experiment (P-BACE) is a new generation of neutral gas mass spectrometer based on the time-of-flight principle. P-BACE is the scientific experiment on the Mars Environment Analog Platform (MEAP) flown successfully on a balloon mission in summer 2008. The MEAP mission was flown with a 334,000 m3 helium balloon in the stratosphere on a semicircular trajectory from northern Sweden around the North Pole to Canada using the summer northern hemispheric wind current. The atmospheric conditions at an atmospheric altitude of 35–40 km are remarkably similar to those on the surface of Mars and thus the balloon mission was an ideal testbed for our mass spectrometer P-BACE. Originally this instrument was designed for in situ measurements of the chemical composition of the Martian atmosphere.P-BACE has a unique mass range from 0 to 1000 amu/q with a mass resolution m/Δm (FWHM) > 1000, and the dynamic range is at least six orders of magnitude. During this experiment, the acquisition of one mass spectrum is a sum of 65,535 single spectra, recorded in a time frame of 66 s.The balloon mission lasted 5 days and had successfully demonstrated the functionality of the P-BACE instrument during flight conditions. We had recorded more than 4500 mass spectra. With little modifications, P-BACE can be used on a planetary mission for Mars, but for example also for Venus or Mercury, if placed on a satellite. 相似文献
4.
A. Galli P. Wurz S. Barabash A. Grigoriev H. Gunell R. Lundin M. Holmström A. Fedorov 《Space Science Reviews》2006,126(1-4):267-297
We present measurements of energetic hydrogen and oxygen atoms (ENAs) on the nightside of Mars detected by the neutral particle
detector (NPD) of ASPERA-3 on Mars Express. We focus on the observations for which the field-of-view of NPD was directed at
the nightside of Mars or at the region around the limb, thus monitoring the flow of ENAs towards the nightside of the planet.
We derive energy spectra and total fluxes, and have compiled maps of hydrogen ENA outflow. The hydrogen ENA intensities reach
105 cm−2 sr−1 s−1, but no oxygen ENA signals above the detection threshold of 104 cm−2 sr−1 s−1 are observed. These intensities are considerably lower than most theoretical predictions. We explain the discrepancy as due
to an overestimation of the charge-exchange processes in the models for which too high an exospheric density was assumed.
Recent UV limb emission measurements (Galli et al., this issue) point to a hydrogen exobase density of 1010 m−3 and a very hot hydrogen component, whereas the models were based on a hydrogen exobase density of 1012 m−3 and a temperature of 200 K predicted by Krasnopolsky and Gladstone (1996). Finally, we estimate the global atmospheric loss
rate of hydrogen and oxygen due to the production of ENAs. 相似文献
5.
D. V. Titov H. Svedhem D. McCoy J. -P. Lebreton S. Barabash J. -L. Bertaux P. Drossart V. Formisano B. Haeusler O. I. Korablev W. Markiewicz D. Neveance M. Petzold G. Piccioni T. L. Zhang F. W. Taylor E. Lellouch D. Koschny O. Witasse M. Warhaut A. Acomazzo J. Rodrigues-Cannabal J. Fabrega T. Schirmann A. Clochet M. Coradini 《Cosmic Research》2006,44(4):334-348
The first European mission to Venus (Venus Express) is described. It is based on a repeated use of the Mars Express design with minor modifications dictated in the main by more severe thermal environment at Venus. The main scientific task of the mission is global exploration of the Venusian atmosphere, circumplanetary plasma, and the planet surface from an orbiting spacecraft. The Venus Express payload includes seven instruments, five of which are inherited from the missions Mars Express and Rosetta. Two instruments were specially designed for Venus Express. The advantages of Venus Express in comparison with previous missions are in using advanced instrumentation and methods of remote sounding, as well as a spacecraft with a broad spectrum of capabilities of orbital observations. 相似文献
6.
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
7.
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
8.
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
9.
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
10.
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