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Temporal evolution of the electric field accelerating electrons away from the auroral ionosphere
KTH, Superseded Departments, Alfvén Laboratory.ORCID iD: 0000-0002-1594-1861
KTH, Superseded Departments, Alfvén Laboratory.ORCID iD: 0000-0003-2422-5426
KTH, Superseded Departments, Alfvén Laboratory.ORCID iD: 0000-0003-1270-1616
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2001 (English)In: Nature, ISSN 0028-0836, Vol. 414, no 6865, 724-727 p.Article in journal (Refereed) Published
Abstract [en]

The bright night-time aurorae that are visible to the unaided eye are caused by electrons accelerated towards Earth by an upward-pointing electric field(1-3). On adjacent geomagnetic field lines the reverse process occurs: a downward-pointing electric field accelerates electrons away from Earth(4-11). Such magnetic-field-aligned electric fields in the collisionless plasma above the auroral ionosphere have been predicted(12), but how they could be maintained is still a matter for debate(13). The spatial and temporal behaviour of the electric fields-a knowledge of which is crucial to an understanding of their nature-cannot be resolved uniquely by single satellite measurements. Here we report on the first observations by a formation of identically instrumented satellites crossing a beam of upward-accelerated electrons. The structure of the electric potential accelerating the beam grew in magnitude and width for about 200 s, accompanied by a widening of the downward-current sheet, with the total current remaining constant. The 200-s timescale suggests that the evacuation of the electrons from the ionosphere contributes to the formation of the downward-pointing magnetic-field-aligned electric fields. This evolution implies a growing load in the downward leg of the current circuit, which may affect the visible discrete aurorae.

Place, publisher, year, edition, pages
2001. Vol. 414, no 6865, 724-727 p.
Keyword [en]
electrostatic potentials, current region, black aurora, altitude
URN: urn:nbn:se:kth:diva-21169DOI: 10.1038/414724aISI: 000172676200040OAI: diva2:339866
QC 20100525Available from: 2010-08-10 Created: 2010-08-10Bibliographically approved

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Marklund, Göran T.Ivchenko, Nickolay V.Karlsson, TomasLindqvist, Per-Arne
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