Plasmoid formation for multiple onset substorms: observations of the Japanese Lunar Mission &amp;quot;Kaguya&amp;quot;

T Nagai,K Asamura,H Shibuya,T Tanaka,H Tsunakawa,M N Nishino,Y Saito,O Amm,H Shimizu,Y Yokota,F Takahashi,M Matsushima

doi:10.5194/angeo-27-59-2009

Abstract

Abstract. The Japanese Lunar Mission "Kaguya" carried out its first magnetic field and plasma measurements in the Earth's magnetotail on 22 December 2007. Fortuitously, three well-defined multiple onset substoms took place. Kaguya was located in the premidnight magnetotail at radial distances of 56 RE and observed plasmoids and/or traveling compression regions (TCRs). Although the present study is based on limited data sets, important issues on multiple onset substorms can be examined. Each onset in a series of onsets releases a plasmoid, and magnetic reconnection likely proceeds to tail lobe field lines for each onset. Since the duration of each plasmoid is less than 5 min, these observations imply that magnetic reconnection for each onset can develop fully to the tail lobe field lines and be quenched within this timescale.

Highlights

The Japanese Lunar Mission “Kaguya” was launched on 14 September 2007
Since the duration of each plasmoid is less than 5 min, these observations imply that magnetic reconnection for each onset can develop fully to the tail lobe field lines and be quenched within this timescale
The results from the Geotail observations show that magnetic reconnection in association with a substorm onset usually takes place in the premidnight plasma sheet at X=−20 to −30 RE (e.g. Nagai et al, 1998a, 2005)

Summary

Introduction

Three multiple onset substorms took place and Kaguya observed plasmoids and traveling compression regions (TCRs) during these substorms. Plasmoids and TCRs are often observed successively during substorm activity. Slavin et al (1992) examined ISEE 3 observations at radial distances of 76–80 RE during an extended interval of substorm activity and found that all of the substorms produced one or more plasmoids and/or TCRs. one-to-one correspondence between each onset and a plasmoid is not fully examined. The other is whether or not tail lobe open field lines are reconnected in the magnetic reconnection process for each onset. This question does not seem to be explored properly

Observations

Discussion and conclusions