Implications of mass and energy loss due to coronal mass ejections on magnetically-active stars

TL;DR

This paper investigates how coronal mass ejections (CMEs) contribute to mass and energy loss in magnetically-active stars by analyzing solar CME data and extrapolating to stellar conditions, revealing potentially large stellar wind losses.

Contribution

It provides a novel extrapolation of solar CME-flare relationships to stellar environments, estimating stellar mass and energy loss rates and discussing their implications.

Findings

CME-related mass loss rates can reach ~5x10^-10 M_sun/yr for active stars.

Energy losses due to CMEs could be as high as 0.1 L_sun in highly active stars.

Relationships between CME properties and flare energies may flatten at high energies.

Abstract

Analysis of a database of solar coronal mass ejections (CMEs) and associated flares over the period 1996-2007 finds well-behaved power law relationships between the 1-8 AA flare X-ray fluence and CME mass and kinetic energy. We extrapolate these relationships to lower and higher flare energies to estimate the mass and energy loss due to CMEs from stellar coronae, assuming that the observed X-ray emission of the latter is dominated by flares with a frequency as a function of energy dn/dE=kE^-alpha. For solar-like stars at saturated levels of X-ray activity, the implied losses depend fairly weakly on the assumed value of alpha and are very large: M_dot ~ 5x10^-10 M_sun/yr and E_dot ~ 0.1L_sun. In order to avoid such large energy requirements, either the relationships between CME mass and speed and flare energy must flatten for X-ray fluence >~ 10^31 erg, or the flare-CME association must drop significantly below 1 for more energetic events. If active coronae are dominated by flares, then the total coronal energy budget is likely to be up to an order of magnitude larger than the canonical 10^-3 L_bol X-ray saturation threshold. This raises the question of what is the maximum energy a magnetic dynamo can extract from a star? For an energy budget of 1% of L_bol, the CME mass loss rate is about 5x10^-11 M_sun/yr.