Abstract
Abstract. We present Cluster and Double Star-1 (TC-1) observations from a close magnetic conjunction on 8 May 2004. The five spacecraft were on the dawnside flank of the magnetosphere, with TC-1 located near the equatorial plane and Cluster at higher geographic latitudes in the Southern Hemisphere. TC-1, at its apogee, skimmed the magnetopause for almost 8h (between 08:00-16:00 UT). Flux Transfer Events (FTEs), moving southward/tailward from the reconnection site, were observed by TC-1 throughout almost all of the period. Cluster, travelling on a mainly dawn-dusk trajectory, crossed the magnetopause at around 10:30 UT in the same Magnetic Local Time (MLT) sector as TC-1 and remained close to the magnetopause boundary layer in the Southern Hemisphere. The four Cluster spacecraft observed FTEs for a period of 6.5h between 07:30 and 14:00 UT. The very clear signatures and the finite transverse sizes of the FTEs observed by TC-1 and Cluster imply that, during this event, sporadic reconnection occurred. From the properties of these FTEs, the reconnection site was located northward of both TC-1 and Cluster on the dawn flank of the magnetosphere. Reconnection occurred between draped magnetosheath and closed magnetospheric field lines. Despite variable interplanetary magnetic field (IMF) conditions and IMF-Bz turnings, the IMF clock angle remained greater than 70° and the location site appeared to remain relatively stable in position during the whole period. This result is in agreement with previous studies which reported that the dayside reconnection remained active for an IMF clock angle greater than 70°. The simultaneous observation of FTEs at both Cluster and TC-1, separated by 2h in MLT, implies that the reconnection site on the magnetopause must have been extended over several hours in MLT.
Highlights
Magnetic reconnection between magnetospheric and interplanetary magnetic fields (IMF) is a commonly accepted process, allowing transfer of energy and momentum from the solar wind to the magnetosphere
On 8 May 2004, between 08:00 and 16:00 UT, the TC-1 and Cluster spacecraft were located at low- and high-latitudes, respectively, on the southern dawn flank of the magnetosphere
Both spacecraft observed clear and successive Flux Transfer Events (FTEs) signatures, with “reverse” bipolar signatures of the magnetic field normal component and with a repetition rate of 4 (TC-1) to 8 (Cluster) minutes. These conjugate observations suggest that reconnection was occurring at a reconnection site located northward of both TC-1 and Cluster
Summary
Magnetic reconnection between magnetospheric and interplanetary magnetic fields (IMF) is a commonly accepted process, allowing transfer of energy and momentum from the solar wind to the magnetosphere. Simulations by Berchem et al (1995) and recent observations by Vaisberg et al (2004) suggested the possible existence of multiple Xlines forming isolated magnetic flux ropes on the dayside, as well as on the flanks of the magnetopause, for various IMF conditions These results support the multiple reconnection lines model of Lee and Fu (1985). The different parts of the magnetopause probed by Cluster (high-latitude) and Double Star-1 (near-equatorial latitude) and the use of Cluster multi-spacecraft analysis allow us to develop an understanding of the reconnection geometry on the dawn flank magnetopause during this period and to document the effect of variable IMF conditions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
