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| Titel |
Latitudinal distribution of the solar wind properties in the low- and high-pressure regimes: Wind observations |
| VerfasserIn |
C. Lacombe, C. Salem, A. Mangeney, J.-L. Steinberg, M. Maksimovic, J. M. Bosqued |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 18, no. 8 ; Nr. 18, no. 8, S.852-865 |
| Datensatznummer |
250014037
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| Publikation (Nr.) |
 copernicus.org/angeo-18-852-2000.pdf |
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| Zusammenfassung |
The solar wind properties depend on
λ, the heliomagnetic latitude with respect to the heliospheric
current sheet (HCS), more than on the heliographic latitude. We analyse the wind
properties observed by Wind at 1 AU during about 2.5 solar rotations in 1995, a
period close to the last minimum of solar activity. To determine λ,
we use a model of the HCS which we fit to the magnetic sector boundary crossings
observed by Wind. We find that the solar wind properties mainly depend on the
modulus |λ|. But they also depend on a local parameter, the total
pressure (magnetic pressure plus electron and proton thermal pressure).
Furthermore, whatever the total pressure, we observe that the plasma properties
also depend on the time: the latitudinal gradients of the wind speed and of the
proton temperature are not the same before and after the closest HCS crossing.
This is a consequence of the dynamical stream interactions. In the low pressure
wind, at low |λ|, we find a clear maximum of the density, a clear
minimum of the wind speed and of the proton temperature, a weak minimum of the
average magnetic field strength, a weak maximum of the average thermal pressure,
and a weak maximum of the average β factor. This overdense sheet is
embedded in a density halo. The latitudinal thickness is about 5°
for the overdense sheet, and 20° for the density halo. The HCS is
thus wrapped in an overdense sheet surrounded by a halo, even in the
non-compressed solar wind. In the high-pressure wind, the plasma properties are
less well ordered as functions of the latitude than in the low-pressure wind;
the minimum of the average speed is seen before the HCS crossing. The
latitudinal thickness of the high-pressure region is about 20°. Our
observations are qualitatively consistent with the numerical model of Pizzo for
the deformation of the heliospheric current sheet and plasma sheet.
Key words: Interplanetary physics (solar wind plasma) |
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