Pi2 Pulsations Observed by Van Allen Probes: A Case Study

Tuesday, 16 December 2014
Essam Ghamry1,2, Khan-Hyuk Kim1, H.-J Kwon3, Dong-Hun Lee1, Craig Kletzing4 and William S Kurth4, (1)School of Space Research, Kyung Hee University, Yongin, Gyeonggi-Do,446-701, Korea., Yongin, South Korea, (2)National Research Institute of Astronomy and Geophysics, Helwan, Egypt, (3)Division of Polar Climate Change Research, Korea Polar Research Institute, Incheon, South Korea, (4)Univ. of Iowa, Iowa City, IA, United States
The plasmaspheric virtual resonance model has been proposed as one of the source mechanisms for low-latitude Pi2 pulsations. Few studies have used simultaneous multipoint observations in space to examine the spatial structure of Pi2 pulsations both inside and outside the plasmasphere. In this study we show multipoint observations for Pi2 pulsations using the Van Allen Probes (RBSP-A and RBSP-B). We focus on the two events that occurred between 1700 and 2000 UT on March 12, 2013, which were simultaneously observed by Van Allen Probes and Bohyun (BOH, L = 1.35) station in South Korea. By using plasma density measurements, we determined that during this time RBSP-A was located outside the plasmasphere and RBSP-B was located inside it. We found that the poloidal, radial (δBx) and compressional (δBz), magnetic field components, and the azimuthal (Ey) electric field component observed by both RBSP-A and RBSP-B have a high correlation with the H component at BOH for both events. The δBx and δBz oscillations at both RBSP-A and RBSP-B are nearly out of phase with ground Pi2. The Ey -H cross phases at RBSP-A outside the plasmapause and RBSP-B inside the plasmapause are nearly in quadrature for the first Pi2 event. These observations indicate that the Pi2 pulsations exist outside the plasmasphere with a radially standing signature which supports the plasmaspheric virtual resonance model.