Monitoring Magnetosheath-magnetosphere Interconnection Topology from the Aurora : Volume 20, Issue 5 (30/11/-0001)

By Sandholt, P. E.

Book Id: WPLBN0004001079
Format Type: PDF Article :
File Size: Pages 9
Reproduction Date: 2015

Title:	Monitoring Magnetosheath-magnetosphere Interconnection Topology from the Aurora : Volume 20, Issue 5 (30/11/-0001)
Author:	Sandholt, P. E.
Volume:	Vol. 20, Issue 5
Language:	English
Subject:	Science, Annales, Geophysicae
Collections:	Periodicals: Journal and Magazine Collection, Copernicus GmbH
Historic Publication Date:	-0001
Publisher:	Copernicus Gmbh, Göttingen, Germany

Member Page:	Copernicus Publications
Citation APA MLA Chicago Farrugia, C. J., & Sandholt, P. E. (-0001). Monitoring Magnetosheath-magnetosphere Interconnection Topology from the Aurora : Volume 20, Issue 5 (30/11/-0001). Retrieved from http://self.gutenberg.org/

Description
Description: Department of Physics, University of Oslo, Oslo, Norway. A strong southward rotation of the IMF (B_Z from 5 to -6 nT in ~ 20 s) on 4 January 1995 caused an abrupt reconfiguration of midday aurorae and plasma convection consisting of the following: (1) the red-line aurora associated with magnetosheath plasma transfer at the low-latitude magnetopause appeared at the same time that (2) the green-line aurora from precipitating energetic plasma sheet particles equatorward of the cusp (near the open-closed field line boundary) weakened visibly and shifted equatorward, (3) the high-latitude aurora during the previous northward IMF, which is associated with lobe reconnection, persisted briefly (3 min) and brightened, before it disappeared from the field-of-view, (4) the activation of a strong convection bay (DPY current) at cusp and sub-cusp latitudes when the field turned strongly south, (5) a distinct wave motion of the plasma sheet outer boundary, as inferred from the aurora, which correlates closely with Pc 5 magnetic pulsations. Our interpretation of the dramatic reconfiguration is that reconnection poleward of the cusp coexisted briefly with reconnection at sub-cusp latitudes. The latter provided a magnetic field connection which enabled, on the one hand, magnetosheath particles to enter and cause the red-line cusp aurora, and on the other hand, allowed for magnetospheric energetic particles to escape and weaken the outer plasma sheet source of the green-line emission. The coexistence of the two cusp auroras reflects the time required for one field line topology to replace another, which, under the prevailing high speed wind ( ~ 650 km/s), lasts ~ 3–4 min. The motion of open flux tubes propagating from equator to pole during this transition is traced in the aurora by a poleward moving form. The waves on the outer boundary of the plasma sheet are most likely due to the Kelvin-Helmholtz instability. The study illustrates the ability of local auroral observations to monitor even a global change in magnetospheric magnetic topology.

Key words. Magnetospheric Physics (auroral phenomena; magnetopause, cusp, and boundary layers; solar wind-magnethoshere interactions)

Summary
Monitoring magnetosheath-magnetosphere interconnection topology from the aurora