Ponderomotive forces in magnetized nonthermal space plasmas due to cyclotron waves

¹ Departmento de Física, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
e-mail: joaquin.espinoza.t@ug.uchile.cl; pablo.moya@uchile.cl
² Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Santiago, Chile
e-mail: felipe.asenjo@uai.cl

Received: 1 December 2023
Accepted: 4 March 2024

Abstract

Context. The ponderomotive force is involved in a variety of space plasma phenomena characterized by the family of Kappa distributions. Therefore, evaluating these nonthermal effects in the ponderomotive force is required.

Aims. The Karpman–Washimi ponderomotive interaction due to cyclotron waves is evaluated for different space conditions considering low-temperature magnetized plasmas described by an isotropic Kappa distribution and with a wave propagation parallel to the background magnetic field.

Methods. We performed a brief analysis of the influence of the Kappa distribution in the dispersion relation for a low-temperature plasma expansion at the lowest order in which the thermal effects can be appreciated without considering the damping characteristics of the wave. The different factors of the ponderomotive force were obtained and analyzed separately as a function of the wavenumber, the spectral index κ, and the plasma beta.

Results. We found a relevant influence of the nonthermal effects in all factors of the ponderomotive force for magnetized plasmas. The effect of the Kappa distribution has been evaluated for a wide variety of space environments, such as the solar wind and the different regions of our magnetosphere, where it has been found that these results can be relevant for the solar wind, the magnetosheath, the plasma sheet, and the polar cusps. We also analyzed the role of the nonthermal effect in the induced Karpman–Washimi ponderomotive magnetization in the context of spatial plasmas and the total radiated power associated with it.

Conclusions. We find that even for nearly cold magnetized plasmas and waves far from the resonances, the effect of the kappa parameter in the ponderomotive force cannot be neglected. This suggests a significant role of the Kappa distribution in ponderomotive phenomena of space physics.