Winds and magnetospheres of stars and planets: similarities and differences

TL;DR

This paper reviews the physics of stellar and planetary winds and magnetospheres, highlighting their similarities and differences in origin, structure, and observable phenomena like flares and radio emissions.

Contribution

It provides a comparative overview of how winds and magnetospheres operate in stars and planets, emphasizing their physical mechanisms and observational signatures.

Findings

Mass loss driven by radiative line-scattering in massive stars

Thermal corona-driven winds in low-mass stars and planets

Magnetic reconnection causes observable flares and radio outbursts

Abstract

Both stars and planets can lose mass through an expansive wind outflow, often constrained or channeled by magnetic fields that form a surrounding magnetosphere. The very strong winds of massive stars are understood to be driven by line-scattering of the star's radiative momentum, while in the Sun and even lower-mass stars a much weaker mass loss arises from the thermal expansion of a mechanically heated corona. In exoplanets around such low-mass stars, the radiative heating and wind interaction can lead to thermal expansion or mechanical ablation of their atmospheres. Stellar magnetospheres result from the internal trapping of the wind outflow, while planetary magnetospheres are typically shaped by the external impact from the star's wind. But in both cases the stressing can drive magnetic reconnection that results in observable signatures such as X-ray flares and radio outbursts. This review will aim to give an overview of the underlying physics of these processes with emphasis on their similarities and distinctions for stars vs. planets.