| 1. |
- 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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| 2. |
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| 3. |
- Feldstein, Y. I., et al.
(författare)
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Auroral electrojets and 3D currents in the ionosphere-magnetosphere system
- 2006
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Ingår i: “Physics of Auroral Phenomena”, Proc. XXIX Annual Seminar, Apatity. - : Kola Science Centre, Russian Academy of Science. ; , s. 25-30
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There are shortly described results of the analysis of variations in the location and intensity of the auroral electrojets during magnetic storms and substorms using a numerical method for estimating the equivalent ionospheric currents based on data from meridian chains of magnetic observatories. It is shown that the westward electrojet adjoins to the polar electrojet located at cusp latitudes in the dayside sector. The association of electrojets with the field-aligned currents (FACs), namely Region 1 FAC and Region 2 FAC is considered. During intense disturbances a Region 3 FAC (accompanied with diffuse electron precipitation from the plasma sheet boundary layer) with the downward current was identified. The analysis of observational data is summarized in terms of 2D time-latitude distribution of electrojets at ionospheric altitudes. The magnetic field sawtooth variations generated during the storm main and early recovery phases are also discussed. To follow 3D currents in the magnetosphereionosphere system a clarified view of interrelated 3D currents and magnetospheric plasma domains is presented.
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| 4. |
- Feldstein, Y. I., et al.
(författare)
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Auroral electrojets and boundaries of plasma domains in the magnetosphere during magnetically disturbed intervals
- 2006
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 24:8, s. 2243-2276
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Tidskriftsartikel (refereegranskat)abstract
- We investigate variations in the location and intensity of the auroral electrojets during magnetic storms and substorms using a numerical method for estimating the equivalent ionospheric currents based on data from meridian chains of magnetic observatories. Special attention was paid to the complex structure of the electrojets and their interrelationship with diffuse and discrete particle precipitation and field-aligned currents in the dusk sector. During magnetospheric substorms the eastward electrojet (EE) location in the evening sector changes with local time from cusp latitudes (Phi similar to 77 degrees) during early afternoon to latitudes of diffuse auroral precipitation (Phi similar to 65 degrees) equatorward of the auroral oval before midnight. During the main phase of an intense magnetic storm the eastward currents in the noon-early evening sector adjoin to the cusp at Phi similar to 65 degrees and in the pre-midnight sector are located at subauroral latitude Phi similar to 57 degrees. The westward electrojet (WE) is located along the auroral oval from evening through night to the morning sector and adjoins to the polar electrojet (PE) located at cusp latitudes in the day-side sector. The integrated values of the eastward (westward) equivalent ionospheric current during the intense substorm are similar to 0.5 MA (similar to 1.5 MA), whereas they are 0.7 MA (3.0 MA) during the storm main phase maximum. The latitudes of auroral particle precipitation in the dusk sector are identical with those of both electrojets. The EE in the evening sector is accompanied by particle precipitation mainly from the Alfven layer but also from the near-Earth part of the central plasma sheet. In the lower-latitude part of the EE the field-aligned currents (FACs) flow into the ionosphere (Region 2 FAC), and at its higher-latitude part the FACs flow out of the ionosphere (Region 1 FAC). During intense disturbances, in addition to the Region 2 FAC and the Region 1 FAC, a Region 3 FAC with the downward current was identified. This FAC is accompanied by diffuse electron precipitation from the plasma sheet boundary layer. Actually, the triple system of FAC is observed in the evening sector and, as a consequence, the WE and the EE overlap. The WE in the evening sector comprises only the high-latitude periphery of the plasma precipitation region and corresponds to the Hall current between the Region 1 FAC and Region 3 FAC. During the September 1998 magnetic storm, two velocity bursts (similar to 2-4 km/s) in the magnetospheric convection were observed at the latitudes of particle precipitation from the central plasma sheet and at subauroral latitudes near the ionospheric trough. These kind of bursts are known as subauroral polarization streams (SAPS). In the evening sector the Alfven layer equatorial boundary for precipitating ions is located more equatorward than that for electrons. This may favour northward electric field generation between these boundaries and may cause high speed westward ions drift visualized as SAPS. Meanwhile, high speed ion drifts cover a wider range of latitudes than the distance between the equatorward boundaries of ions and electrons precipitation. To summarize the results obtained a new scheme of 3-D currents in the magnetosphere-ionosphere system and a clarified view of interrelated 3-D currents and magnetospheric plasma domains are proposed.
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| 5. |
- Mlynczak, Martin G., et al.
(författare)
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Solar-terrestrial coupling evidenced by periodic behavior in geomagnetic indexes and the infrared energy budget of the thermosphere
- 2008
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 35:5
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Tidskriftsartikel (refereegranskat)abstract
- We examine time series of the daily global power (W) radiated by carbon dioxide (at 15 μm) and by nitric oxide (at 5.3 μm) from the Earth's thermosphere between 100 km and 200 km altitude. Also examined is a time series of the daily absorbed solar ultraviolet power in the same altitude region in the wavelength span 0 to 175 run. The infrared data are derived from the SABER instrument and the solar data are derived from the SEE instrument, both on the NASA TIMED satellite. The time series cover nearly 5 years from 2002 through 2006. The infrared and solar time series exhibit a decrease in radiated and absorbed power consistent with the declining phase of the current 11-year solar cycle. The infrared time series also exhibits high frequency variations that are not evident in the solar power time series. Spectral analysis shows a statistically significant 9-day periodicity in the infrared data but not in the solar data. A very strong 9-day periodicity is also found to exist in the time series of daily Ap and Kp geomagnetic indexes. These 9-day periodicities are linked to the recurrence of coronal holes on the Sun. These results demonstrate a direct coupling between the upper atmosphere of the Sun and the infrared energy budget of the thermosphere. Copyright 2008 by the American Geophysical Union.
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