Ballooning Instability in the Magnetospheric Plasma: Two‐Dimensional Eigenmode Analysis

Abstract

This paper is concerned with the transverse structure of the ballooning instability in a two-dimensionally inhomogeneous model of the magnetosphere, which takes into account inhomogeneity both across the magnetic shells and along the field lines. According to the previous studies, the ballooning instability can develop at steep fall of the plasma pressure from the Earth. In this paper, the region of negative plasma pressure gradient is assumed to be sharply localized across the magnetic shells. It causes the localization of the unstable perturbation in the same direction. In this region, the perturbation has a resonator-like structure, where only modes with discrete set of the growth rate values can exist. The azimuthal wave number of the unstable mode must exceed some critical value, which is determined by the width of the localization region.

Plasmasphere Control of ULF Wave Distribution at Different Geomagnetic Conditions

“…Large plasma β and steep plasma pressure gradient may satisfy a ballooning instability condition. Ballooning modes are result of coupling of Alfvén and slow waves in MHD (Rubtsov et al., 2020; Vetoulis & Chen, 1994) and Alfvén and drift‐compressional waves in kinetics (Klimushkin et al., 2012). The excited waves can be either poloidal or compressional in Pc4 and Pc5 bands.…”

Alfvén Waves Generated Through the Drift‐Bounce Resonant Instability in the Ring Current: A THEMIS Multi‐Spacecraft Case Study

“…It is believed that these waves are generated by internal sources, such as nonstationary currents caused by the magnetic drift of energetic particles injected in the magnetosphere during substorms (James et al., 2013; Mager & Klimushkin, 2008; Zolotukhina et al., 2008), and plasma instabilities associated with non‐equilibrium distributions of ring current particles. The possible instabilities are the ballooning instability arising from earthward pressure gradient (Keiling, 2012; Leonovich & Kozlov, 2014; Roux et al., 1991; Rubtsov et al., 2020); the drift resonant instability (Claudepierre et al., 2013; Dai et al., 2013) and the bounce‐drift resonant instability (Chen & Hasegawa, 1994; Korotova et al., 2016; Min et al., 2017; Southwood et al., 1969; Yamamoto et al., 2019) caused by radial gradients of phase space density of the energetic particles being in the corresponding resonance with the waves; or the same resonant instabilities but caused by non‐equilibrium inverted distribution of the resonant particles (bump‐on‐tail instability; Baddeley et al., 2005; Liu et al., 2013; Mager et al., 2018; Yeoman et al., 2000); the drift‐mirror instability due to plasma temperature anisotropy (Constantinescu et al., 2009; Hasegawa & Chen, 1989; Klimushkin & Mager, 2012; Rae et al., 2007). However, sometimes the poloidal ULF waves observed seeming, generated by the solar wind ram pressure impulses (A. Leonovich et al., 2019; Zong et al., 2017) and moving pressure pulses on the magnetopause (Klimushkin et al., 2019).…”