ULF Waves Associated with Solar Wind Deceleration in the Earth's Foreshock

Abstract

Characteristics of ULF waves associated with the solar wind deceleration in the Earth's foreshock on 6–7 April 2003 is studied using the wave telescope technique. In the satellite frame, the ULF waves are the left-handed polarized and quasi anti-parallel propagating mode, with a power peak at about 18.63 mHz. The wave vector in the GSE coordinates is estimated to be κ = (−4.29, 2.28, 1.21) × 10−4 km−1. In the solar wind frame, the frequency of waves becomes −9.39 mHz after the Doppler shift correction. The propagation direction of the waves is thus reversed and correspondingly the polarization of the waves becomes right-handed. The above-mentioned characteristics of the ULF waves in the solar wind frame indicate that the ULF waves associated with the solar wind deceleration are the Alfven-whistler waves, which have been frequently reported in both the observations and computer simulations.