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Cluster observes formation of high-beta plasma blobs

Haerendel, G; Georgescu, E; Glassmeier, KH; Klecker, B; Bogdanova, YV; Reme, H; Frey, H; (2004) Cluster observes formation of high-beta plasma blobs. In: Spatio-temporal analysis and multipoint measurements in space (STAMMS). (pp. 2391 - 2401). European Geosciences Union Green open access

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Abstract

Late in a sequence of four moderate substorms on 26 July 2001,Cluster observed periods of a few minutes durations of high-beta plasma events (B < 10 nT, beta=2-30), connected with dipolarizations of the magnetic field. Cluster was located near 02:45 MLT, at R=19 R-E and at about 5 N GSM. These events began late in the recovery phase of the second and about 5 min before onset of the third substorm and lasted for three hours, way beyond the recovery phase of the fourth substorm. The most remarkable observation is that the onset coincided with the arrival of energetic (E similar to 7 keV) O+ ions and energetic electrons obviously from the ionosphere, which tended to dominate the plasma composition throughout the remaining time. The magnetic flux and plasma transport is continuously directed equator-ward and earthward, with oscillatory east-west movements superposed. Periods of the order of 5-10 min and strong correlations between the magnetic elevation angle and log P (correlation coefficient 0.78) are highly reminiscent of the high-beta plasma blobs discovered with Equator-S and Geotail between 9 and 11 R-E in the late night/early morning sector (Haerendel et al., 1999).We conclude that Cluster observed the plasma blob formation in the tail plasma sheet, which seems to occur predominantly in the recovery and post-recovery phases of substorms. This is consistent with the finding of Equator-S and Geotail. The origin is a pulsed earthward plasma transport with velocity amplitudes of only several tens of km/s.

Type: Proceedings paper
Title: Cluster observes formation of high-beta plasma blobs
Event: STAMMS (Spatio-Temporal Analy- sis and Multipoint Measurements in Space: Orleans, France, 12–16 May 2003)
Location: Orleans, FRANCE
Open access status: An open access version is available from UCL Discovery
DOI: 10.5194/angeo-22-2391-2004
Publisher version: http://dx.doi.org/10.5194/angeo-22-2391-2004
Language: English
Additional information: This special issue includes a large fraction of the papers that were presented at the STAMMS (Spatio-Temporal Analy- sis and Multipoint Measurements in Space) meeting held in Orleans (France, 12–16 May 2003). This work is distributed under the Creative Commons Attribution 3.0 License. Anyone (the author, his/her institution/company, the publisher, as well as the public) is free to copy, distribute, transmit, and adapt the work as long as the original author is given credit.
Keywords: Magnetospheric physics, plasma convection, plasma sheet, storms and substorms, collisionless magnetic reconnection, pulsation event, omega-bands, magnetosphere, sheet, instabilities, model, ps6
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/138754
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