Multiple magnetic topologies in flux transfer events at the magnetopause: In situ measurements and formation mechanisms

Pu, Zuyin

Multiple magnetic topologies in flux transfer events at the magnetopause: In situ measurements and formation mechanisms

Thursday, 13 July 2017: 11:40

Furong Room (Cynn Hotel)

Zuyin Pu¹, Leiqi Lv¹, Jun Zhong², Lun Xie¹, Suiyan Fu¹, Qiugang Zong¹, Malcolm Dunlop³, Yulia Bogdanova⁴, Chijie Xiao⁵ and Xiaogang Wang⁶, (1)Peking University, School of Earth and Space Sciences, Beijing, China, (2)Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China, (3)Rutherford Appleton Laboratory, Didcot, United Kingdom, (4)Rutherford Appleton Laboratory, Harwell Oxford Didcot, United Kingdom, (5)Peking University, School of Physics, Beijing, China, (6)HIT Harbin Institute of Technology, Harbin, China

Abstract:

Flux transfer events (FTEs) are local transient magnetic reconnections at the magnetopause (MP) that provide channels for transport of solar wind energy and plasma into the magnetosphere (MSP). All current theoretical models suggest that FTEs are open-flux ropes; however, 3D and global simulations show that they contain both open and closed magnetic fields. To clarify this topology, we have analyzed 441 FTEs measured by THEMIS from 2009 to 2011 for which the electron energy-pitch angle distribution was successfully detected. Only open field lines were detected in most magnetosheath (MSH) FTEs, either MSH→N MSP or S MSP→MSH, independent of the polarity of Bn signatures. Newly formed MSH field lines were possibly also measured. In most MP current layers FTEs and most MSP FTEs, multiple types of topologies were observed, irrelevant to the B_n bipolar polarity. Closed field lines were found in all MP current layer and MSP FTEs. In some situations, only closed field lines were seen in MSP FTEs, which are referred to as the fossil FTEs.

These results largely differ from the traditional views, demonstrating the existence of multiple magnetic topologies in FTEs. Based on these results, we propose a new 3D FTE picture to modify the current FTE models by considering the complex field line topology in different branches of the FTE flux rope. Continuous multiple reconnection processes at the dayside MP are studied and suggested to be responsible for the formation of FTE multiple magnetic topologies.