Global Observations of High-m Poloidal Waves in the Magnetosphere during the Recovery Phase of the June 2015 Magnetic Storm

Le, Guan

Global Observations of High-m Poloidal Waves in the Magnetosphere during the Recovery Phase of the June 2015 Magnetic Storm

Tuesday, 11 July 2017: 16:10

Furong Room (Cynn Hotel)

Guan Le, NASA Goddard Space Flight Center, Greenbelt, MD, United States, Peter J Chi, University of California Los Angeles, Los Angeles, CA, United States, Robert J Strangeway, University of California Los Angeles, IGPP/EPSS, Los Angeles, CA, United States, Christopher Russell, Russian Academy of Sciences, Moscow, Russia, James A Slavin, University of Michigan Ann Arbor, Ann Arbor, MI, United States, Kazue Takahashi, Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States, Howard J Singer, NOAA Boulder, Boulder, CO, United States and MMS Magnetometer Team

Abstract:

In this paper, we report global observations of high-m poloidal waves occurred during the recovery phase of the magnetic storm starting on 22 June 2015. The long lasting waves are observed by a constellation of widely spaced satellites from 5 missions including MMS, Van Allen Probes, THEMIS, Cluster, and GOES, covering L-values between 4 and 12 in a large range of local times. These observations have demonstrated that storm-time high-m poloidal waves can occur globally. High-resolution data from four MMS satellites enable us to detect the azimuthal phase shifts and determine the m number to be ~ 100. The mode identification suggests that the observed poloidal waves are associated with the second harmonic of the field line resonance. The wave frequencies range from 8 to 22 mHz and decrease as the radial distance increases. Detailed examinations of instantaneous wave frequency show discrete spatial structures with step-like changes along the radial direction. In each discrete structure the wave has a steady frequency and spans about 1 Re in the radial direction. Our observations suggest that storm-time high-m poloidal waves are different from the single-frequency global poloidal mode waves that are common during periods of low-level of geomagnetic activities.