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- Barabash, S., et al.
(författare)
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Observations of Sounder Accelerated Electrons by Mars Express
- 2020
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Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 125:1
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Tidskriftsartikel (refereegranskat)abstract
- The electron sensor of the Analyzer of Space Plasmas and Energetic Atoms experiment detects accelerated electrons during pulses of radio emissions from the powerful topside sounder: the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board the Mars Express spacecraft. Accelerated electrons are observed at energies up to 400 eV at the times when MARSIS transmits at a frequency between the local plasma frequency and its harmonics (up to 4 times the plasma frequency). When the electron density and magnetic field strength are low (similar to 10(3) cm(-3), similar to 10 nT), the accelerated electrons are almost monoenergetic electron beams. An increase in density and magnetic field (similar to 3 . 10(3) cm(-3), similar to 50 nT) leads to substantial broadening of the energy spectrum of the accelerated electrons. It is concluded that in the latter case, electrons are accelerated by the variable spacecraft potential resulting from the imbalance of the electron and ion currents to the MARSIS antenna during transmission.
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| 2. |
- Carlsson, Ella, et al.
(författare)
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Mass composition of the escaping plasma at Mars
- 2006
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Ingår i: Icarus. - : Elsevier BV. - 0019-1035 .- 1090-2643. ; 182:2, s. 320-328
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Tidskriftsartikel (refereegranskat)abstract
- Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analyzed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: CO2+/O+ and O-2(+)/O+. The following ratios averaged over all events and energies were identified: CO2+/O+ = 0.2 and O-2(+)/O+ = 0.9. The values measured are significantly higher, by a factor of 10 for O-2(+)/O+, than a contemporary modeled ratio for the maximum fluxes which the martian ionosphere can supply. The most abundant ion species was found to be O+, followed by O-2(+) and CO2+. We estimate the loss of CO2+ to be 4.0 x 10(24) s(-1) (0.29 kg s(-1)) by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found.
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| 6. |
- Ungstrup, E., et al.
(författare)
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Rocket-borne particle, field, and plasma observations in the cleft region
- 1975
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 2:7, s. 345-348
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Tidskriftsartikel (refereegranskat)abstract
- First results of comprehensive observations of magnetic and electric fields, and ambient and suprathermal plasmas above the dayside auroral oval with rocket-borne instrumentation which penetrated the cleft region are reported. Measurements were also obtained equatorward and poleward of the cleft. Convection velocities as inferred from electric field measurements were generally toward noon equatorward of the cleft and were antisunward over the polar cap. Our observations of electron temperatures, electric fields and low-frequency electrostatic noise provide strong evidence of a plasma instability (Farley-Buneman) in the E-layer, which is associated with the appearance of the ‘slant E condition’ identified in ground-acquired ionograms. The positions of these measurements relative to that of the cleft were firmly established via the determination of the plasma environment with an electrostatic analyzer.
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