The Effects of Localized Thermal Pressure on Equilibrium Magnetic Fields and Particle Drifts in The Inner Magnetosphere

Abstract

AbstractLocalized injections of hot anisotropic plasma sheet particles into the inner magnetosphere can significantly deform the quiet time dipole‐like magnetic field and thus disturb electron and ion's drift paths and scattering rates. Although many details of magnetic field deformation can be inferred from empirical models, roles of different characteristics of injected plasma on the structure of such deformation require further investigation. In this study, we use the 2‐D axisymmetric equilibrium model to calculate self‐consistent magnetic field in force balance with a Gaussian thermal pressure distribution characterized by four input parameters: the ratio between plasma pressure and magnetic pressure (β) at the pressure peak β0, the radial location of the pressure peak L0, the width of the half peak pressure σ0, and the equatorial pressure anisotropy Ae. Using the modeled magnetic field, we find that the magnetic field perturbation increases with increasing β0 and decreasing σ0 while the magnetic curvature perturbation increases with increasing Ae, β0, and σ0 and decreasing L0. For energetic particles the change of magnetic gradient drift motion is much greater than that of curvature drift motion. The magnetic dip structure formation requires a critical β value that increases with increasing σ0 and decreasing L0. Despite the unavailability of observations in the existing literatures to check the condition of magnetic dip formation, such condition will be checked against observations as a future study. Finally, we also use 3‐D ring current‐atmosphere interactions model with self‐consistent magnetic field model to illustrate the effect of azimuthal pressure distribution, which is relevant to asymmetric ring current.