Increasing Flow Oscillation Period at a Tailward Retreating Flux Pileup Region during Dipolarization

Tuesday, 16 December 2014
Evgeny V Panov1, Wolfgang Baumjohann1, Marina Kubyshkina2, Rumi Nakamura1, Victor A Sergeev2, Vassilis Angelopoulos3, Karl-Heinz Glassmeier4 and Anatoli A Petrukovich5, (1)Space Research Institute, Austrian Academy of Sciences, Graz, Austria, (2)St. Petersburg State University, St. Petersburg, Russia, (3)University of California Los Angeles, Los Angeles, CA, United States, (4)Technical University of Braunschweig, Braunschweig, Germany, (5)Space Research Institute RAS, Moscow, Russia
On 23 March 2009 between 6:00 and 6:40 UT, three THEMIS probes (P3, P4, and P5) were at about -11.5 Earth radii (RE) and two (P1and P2) were at -14 RE downtail. The inner probes (P3-P5) started to observe oscillatory flow braking with plasma sheet dipolarization due to fluxpileup at about 6:04 UT. After 6:16 UT the flux pileup region (FPR) expanded tailward as the outer probes (P1 and P2) moved closer to the neutral sheet and began to observe oscillatory braking also. During the FPR tailward expansion, the flow oscillation period increased from about 3.5 minutes at P3-P5 to about 6.2 minutes at P1 and P2. Meanwhile, as observed by the all-sky camera at Rankin Inlet, auroral activity gradually moved northward indicating that the increasing oscillation period of flows at the tailward retreating FPR is crucial for understanding the magnetosphere-ionosphere coupling.