Details

Autor(en) / Beteiligte

• Ohtani, Shinichi
• Gkioulidou, Matina
• Wang, Chih‐Ping
• Wolf, Richard A.

Titel

The Harang reversal and the interchange stability of the magnetotail

Ist Teil von

• Journal of geophysical research. Space physics, 2016-04, Vol.121 (4), p.3278-3292

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2016

Link zum Volltext

Quelle

Wiley Online Library

Beschreibungen/Notizen

• The present study addresses steady convection in the plasma sheet in terms of the interchange stability with special attention to the Harang reversal. The closure of the tail current with a field‐aligned current (FAC) results from the divergence/convergence of the pressure gradient current. If the magnetotail is in a steady state, the associated change of local plasma pressure p has to balance with its advective change. Accordingly, for adiabatic transport, the flux tube entropy parameter pVγ increases and decreases along the convection path in regions corresponding to downward and upward FACs, respectively. This requirement, along with the condition for the interchange stability imposes an important constraint on the direction of convection especially in the regions of downward FACs. It is deduced that for the dusk cell, the convection in the downward R2 current has to be directed azimuthally duskward, which follows the sunward, possibly dawnward deflected, convection in the region of the premidnight upward R1 current. This duskward turn of convection takes place in the vicinity of the R1‐R2 demarcation, and it presumably corresponds to the Harang reversal. For the dawn cell the convection in the postmidnight downward R1 current has to deflect dawnward, and then it proceeds sunward in the upward R2 current. The continuity of the associated ionospheric currents consistently reproduces the assumed FAC distribution. The proposed interrelationships between the convection and FACs are also verified with a quasi‐steady plasma sheet configuration and convection reproduced by a modified Rice Convection Model with force balance. Key Points The Harang reversal is the solution of the steady plasma sheet convection for the interchange stability PVg increases/decreases along the convection flow for downward/upward FACs in a steady plasma sheet Auroral arcs in the premidnight R1/R2 currents mapped to the equator likely extend in the Sun‐Earth/azimuthal direction