| 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. |
- Jones, G. H., et al.
(författare)
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The dust halo of Saturn's largest icy moon, Rhea
- 2008
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 319:5868, s. 1380-1384
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Tidskriftsartikel (refereegranskat)abstract
- Saturn's moon Rhea had been considered massive enough to retain a thin, externally generated atmosphere capable of locally affecting Saturn's magnetosphere. The Cassini spacecraft's in situ observations reveal that energetic electrons are depleted in the moon's vicinity. The absence of a substantial exosphere implies that Rhea's magnetospheric interaction region, rather than being exclusively induced by sputtered gas and its products, likely contains solid material that can absorb magnetospheric particles. Combined observations from several instruments suggest that this material is in the form of grains and boulders up to several decimetres in size and orbits Rhea as an equatorial debris disk. Within this disk may reside denser, discrete rings or arcs of material.
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| 3. |
- Telloni, Daniele, et al.
(författare)
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Linking Small-scale Solar Wind Properties with Large-scale Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar Orbiter Observations
- 2022
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Ingår i: Astrophysical Journal. - : IOP Publishing Ltd. - 0004-637X .- 1538-4357. ; 935:2
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Tidskriftsartikel (refereegranskat)abstract
- The solar wind measured in situ by Parker Solar Probe in the very inner heliosphere is studied in combination with the remote-sensing observation of the coronal source region provided by the METIS coronagraph aboard Solar Orbiter. The coronal outflows observed near the ecliptic by Metis on 2021 January 17 at 16:30 UT, between 3.5 and 6.3 R (circle dot) above the eastern solar limb, can be associated with the streams sampled by PSP at 0.11 and 0.26 au from the Sun, in two time intervals almost 5 days apart. The two plasma flows come from two distinct source regions, characterized by different magnetic field polarity and intensity at the coronal base. It follows that both the global and local properties of the two streams are different. Specifically, the solar wind emanating from the stronger magnetic field region has a lower bulk flux density, as expected, and is in a state of well-developed Alfvenic turbulence, with low intermittency. This is interpreted in terms of slab turbulence in the context of nearly incompressible magnetohydrodynamics. Conversely, the highly intermittent and poorly developed turbulent behavior of the solar wind from the weaker magnetic field region is presumably due to large magnetic deflections most likely attributed to the presence of switchbacks of interchange reconnection origin.
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| 4. |
- Feldstein, Y. I., et al.
(författare)
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Structure of the auroral precipitation region in the dawn sector : relationship to convection reversal boundaries and field-aligned currents
- 2001
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 19:5, s. 495-519
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Tidskriftsartikel (refereegranskat)abstract
- Simultaneous DMSP F7 and Viking satellite measurements of the dawnside high-latitude auroral energy electron and ion precipitation show that the region of the low and middle altitude auroral precipitation consists of three characteristic plasma regimes. The recommendation of the IAGA Working Group IIF/III4 at the IAGA Assembly in Boulder, July 1995 to decouple the nomenclature of ionospheric populations from magnetospheric population is used for their notation. The most equatorial regime is the Diffuse Auroral Zone (DAZ) of diffuse spatially unstructured precipitating electrons. It is generated by the plasma injection to the inner magnetosphere in the nightside and the subsequent drift plasma to the dawnside around the Earth. Precipitating par tides have a hard spectrum with typical energies of electrons and ions of more than 3 keV. In the DAZ, the ion pitch-angle distribution is anisotropic. with the peak near 90 degrees. The next part is the Auroral Oval (AO), a structured electron regime which closely resembles the poleward portion of the nightside auroral oval. The typical electron energy is several keV, and the ion energy is up to 10 keV. Ion distributions are predominantly isotropic. In some cases, this plasma regime may be absent in the prenoon sector. Poleward of the Auroral Oval, there is the Soft Small Scale Luminosity (SSSL) regime. It is caused by structured electron and ion precipitation with typical electron energy of about 0.3 keV and ion energy of about 1 keV. The connection of these low-altitude regimes with plasma domains of the distant magnetosphere is discussed. For mapping of the plasma regimes to the equatorial plane of the magnetosphere, the empirical model by Tsyganenko (1995) and the conceptual model by Alexeev et al. (1996) are used. The DAZ is mapped along the magnetic field lines to the Remnant Layer (RL), which is located in the outer radiation belt region: the zone of structured electrons and isotropic ion precipitation (AO) is mapped to the dawn periphery of the Central Plasma Sheet (CPS); the soft small scale structured precipitation (SSSL) is mapped to the outer magnetosphere close to the magnetopause, i.e. the Low Latitude Boundary Layer (LLBL). In the near-noon sector, earthward fluxes of soft electrons, which cause the Diffuse Red Aurora (DRA), are observed. The ion energies decrease with increasing latitude, The plasma spectra of the DRA regime are analogous to the spectra of the Plasma Mantle (PM). In the dawn sector, the large-scale field-aligned currents flow into the ionosphere at the SSSL latitudes (Region 1) and flow out at the AO or DAZ latitudes (Region 2). In the dawn and dusk sectors, the large-scale Region 1 and Region 2 FAC generation occurs in different plasma domains of the distant magnetosphere. The dawn and dusk FAC connection to the traditional Region 1 and Region 2 has only formal character, as FAC generating in various magnetospheric plasma domains integrate in the same region (Region 1 or Region 2). In the SSSL, there is anti-sunward convection in the DAZ and the AO, there is the sunward convection. At PM latitudes, the convection is controlled by the azimuthal IMF component (By) It is suggested to extend the notation of the plasma pattern boundaries, as proposed by Newell et al. (1996), for the nightside sector of the auroral oval to the dawn sector.
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| 5. |
- Mishin, V M, et al.
(författare)
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A study of the CDAW 9C substorm of May 3, 1986, using magnetogram inversion technique 2, and a substorm scenario with two active phases
- 1997
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Ingår i: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS. - 0148-0227. ; 102:A9, s. 19845-19859
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Tidskriftsartikel (refereegranskat)abstract
- One of the CDAW 9C substorms is investigated in this paper using the database reported by Hones et al. and supplemented with magnetogram inversion technique (MIT) 2 data. These latter have provided information about the dynamics of the open tail magnetic Aux, current systems in the ionosphere, and the size and dynamics of the current wedge. We have identified the growth: expansion, and recovery phases of this substorm, with characteristics expected from a generally accepted scenario. However, specific signatures were observed in the interval (0919-0935) UTI i.e., between the growth and expansion phases, indicating the concurrent development of the substorm onset and corresponding instabilities in the innermost current sheet, and small-scale cross-tail current disruptions without the open tail reconnection. In addition to signatures of small-scale dipolarization, an increase of the open tail magnetic flux, and a current system of the type close to DP 2 were observed at (0919-0935) UT, which is more likely to suggest predominance of the tail-stretching process than magnetic collapse, This fact was interpreted in tel ms of a relevant simple model as a signature of the growth of the energy input from the solar wind which ensures the observable disturbance power. Hence the disturbance st (0919-0935) UT was more likely a driven one than an unloading one. The aforementioned signatures make it possible to identify the interval (0919-0935) UT as the ''phase of multiple onsets'' or: (equivalently) the ''first active phase,'' which was previously defined by Mishin [1991., and references therein] as one of the four standard phases of a typical substorm (in addition to the expansion phase). Thus the case study supports the substorm scenario with two active phases and, accordingly, with two different kinds of physics, This case study illustrates also the informativity of MIT 2 data and their ability to effectively complement the database traditionally used in substorm studies.
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| 6. |
- VOGELSANG, H, et al.
(författare)
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An ionospheric travelling convection vortex event observed by ground‐based magnetometers and by Viking
- 1993
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 20:21, s. 2343-2346
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Tidskriftsartikel (refereegranskat)abstract
- A transient ionospheric travelling convection vortex (ITCV) event was recorded by the EISCAT magnetometer cross in northern Scandinavia on April 21, 1986 around 8:40 MLT. Simultaneously, the near-conjugate satellite VIKING observed strong magnetic and electric field variations on closed magnetic field lines. The signatures seen by the spacecraft are consistent with a passage through two oppositely directed field-aligned current tubes. The total upward and downward currents turned out to be matched within a region of approximately 1000 km in the ionosphere. Because of the close spatial and temporal proximity of both observations we interpret the field-aligned currents as being associated with the ITCV. This is the first time that in-situ measurements of the currents connecting the ITCV to the source region close to the magnetopause have been published. Both the current density and the dimensions of the current tubes could be estimated here.
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