Observations of Whistler-mode Waves and Large-amplitude Electrostatic Waves Associated with a Dipolarization Front in the Bursty Bulk Flow

Abstract

Plasma jets and jet fronts are common phenomena in planetary magnetospheres. They are usually associated with many plasma waves and can play a key role in the energy conversion, the excitation of wave emissions, particle acceleration, and the evolution of many astrophysical phenomena, which are major issues in the study of helio-terrestrial space physics. In this paper, we carefully investigated the properties of the whistler-mode wave and large-amplitude electrostatic wave in a plasma jet (bursty bulk flow (BBF)) using the Magnetospheric Multiscale mission data on the Earth's magnetosphere. At the leading part of the BBF, intense whistler-mode waves were observed inside the ion mirror-mode structures, which should be excited by the perpendicular temperature anisotropy of trapping electrons. A small-scale dipolarization front (DF) was then observed at the center of this BBF as a boundary between the leading and trailing parts of the BBF. Behind the DF, both an ion mirror-mode structure and whistler-mode waves disappear, while a large-amplitude electrostatic wave was detected and was associated with the cold ions at the trailing part of the BBF. The electrostatic wave is supposed to be generated by ion beam instability. These results will significantly improve the understanding of the kinetic process associated with the important boundary layer DF within plasma jets. The corresponding wave–particle interaction in space and the plasma environment can be further understood.

MESSENGER Observations of Multiple Magnetic Energy Releases during Mercury’s Substorm

“…During substorms, the magnetic energy and flux are first loading in the lobe region and then unloading in the magnetotail (Sun et al 2015a;Imber & Slavin 2017;Sun et al 2020a). Dipolarization front, which is a product of nightside magnetotail reconnection, is characterized by a sudden enhancement of the northward component of the magnetic field (B z ; Runov et al 2011;Fu et al 2013;Dewey et al 2020) and is usually associated with a planetward bursty bulk flow (BBF) in the plasma sheet (Runov et al 2015;Zhang et al 2022). On Mercury, dipolarizations are common, with characteristics of a rapid increase (∼1 s) in the B z component and gradual return (∼10 s) to preonset values (Sundberg et al 2012).…”