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| Titel |
Thermal ion measurements on board Interball Auroral Probe by the Hyperboloid experiment |
| VerfasserIn |
N. Dubouloz, J.-J. Berthelier, M. Malingre, L. Girard, Y. Galperin, J. Covinhes, D. Chugunin, M. Godefroy, G. Gogly, C. Guérin, J.-M. Illiano, P. Kossa, F. Leblanc, F. Legoff, T. Mularchik, J. Paris, W. Stzepourginski, F. Vivat, L. Zinin |
| 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 ; 16, no. 9 ; Nr. 16, no. 9, S.1070-1085 |
| Datensatznummer |
250013449
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| Publikation (Nr.) |
 copernicus.org/angeo-16-1070-1998.pdf |
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| Zusammenfassung |
Hyperboloid is a multi-directional mass
spectrometer measuring ion distribution functions in the auroral and polar
magnetosphere of the Earth in the thermal and suprathermal energy range. The
instrument encompasses two analyzers containing a total of 26 entrance windows,
and viewing in two almost mutually perpendicular half-planes. The nominal
angular resolution is defined by the field of view of individual windows
≈13° × 12.5°. Energy analysis is performed using spherical
electrostatic analyzers providing differential measurements between 1 and 80 eV.
An ion beam emitter (RON experiment) and/or a potential bias applied to
Hyperboloid entrance surface are used to counteract adverse effects of
spacecraft potential and thus enable ion measurements down to very low energies.
A magnetic analyzer focuses ions on one of four micro-channel plate (MCP)
detectors, depending on their mass/charge ratio. Normal modes of operation
enable to measure H+, He+, O++, and O+
simultaneously. An automatic MCP gain control software is used to adapt the
instrument to the great flux dynamics encountered between spacecraft perigee
(700 km) and apogee (20 000 km). Distribution functions in the main analyzer
half-plane are obtained after a complete scan of windows and energies with
temporal resolution between one and a few seconds. Three-dimensional (3D)
distributions are measured in one spacecraft spin period (120 s). The secondary
analyzer has a much smaller geometrical factor, but offers partial access to the
3D dependence of the distributions with a few seconds temporal resolution.
Preliminary results are presented. Simultaneous, local heating of both H+
and O+ ions resulting in conical distributions below 80 eV is
observed up to 3 Earth's radii altitudes. The thermal ion signatures associated
with large-scale nightside magnetospheric boundaries are investigated and a new
ion outflow feature is identified associated to the polar edge of the auroral
oval. Detailed distribution functions of injected magnetosheath ions and
ouflowing cleft fountain ions are measured down to a few eVs in the dayside.
Key words. Ionosphere (auroral ionosphere; particle
acceleration; ionosphere-magnetosphere interactions)
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