Observations of kinetic Alfvén waves by THEMIS near a substorm onset

• DOI: 10.1007/s11434-012-4973-x
• Publication Date: 2012-03-08T09:31:45Z
• Authors: SuPing Duan; ZhenXing Liu; Vassilis Angelopo...
• Keywords: Substorm; Plasma sheet; Wedge (geometry)

Low frequency electromagnetic fluctuations in the vicinity of a magnetospheric substorm onset were investigated using simultaneous observations by THEMIS multiple probes in the near-Earth plasma sheet in the magnetotail. The observations indicate that in the vicinity of a substorm onset, kinetic Alfven waves can be excited in the high-β plasma sheet (β=2µ0nT/B2, the ratio of plasma thermal pressure to magnetic pressure) within the near-Earth magnetotail. The kinetic Alfven wave has a small spatial scale in the high-β plasma. The parallel electric field accompanying kinetic Alfven waves accelerates the charged particles along the magnetic field. The kinetic Alfven waves play an important role in the substorm trigger process, and possibly in the formation of a substorm current wedge.