Torus-Stable Zone Above Starspots
Xudong Sun, Tibor T\"or\"ok, Marc L. DeRosa

TL;DR
This paper investigates the magnetic conditions above starspots that can suppress stellar coronal mass ejections, explaining the low observed CME rates on cool stars through a model of the torus-stable zone.
Contribution
It introduces a potential field model to estimate the extent of the torus-stable zone above starspots, linking magnetic field configurations to CME suppression.
Findings
The upper bound of the TSZ increases with bipole size, dipole strength, and source surface radius.
A secondary TSZ can form at higher altitudes, possibly leading to failed eruptions.
Extended TSZs may explain the low CME detection rate on cool stars.
Abstract
Whilst intense solar flares are almost always accompanied by a coronal mass ejection (CME), reports on stellar CMEs are rare, despite the frequent detection of stellar 'super flares'. The torus instability of magnetic flux ropes is believed to be one of the main driving mechanisms of solar CMEs. Suppression of the torus instability, due to a confining background coronal magnetic field that decreases sufficiently slowly with height, may contribute to the lack of stellar CME detection. Here we use the solar magnetic field as a template to estimate the vertical extent of this 'torus-stable zone' (TSZ) above a stellar active region. For an idealised potential field model comprising the fields of a local bipole (mimicking a pair of starspots) and a global dipole, we show that the upper bound of the TSZ increases with the bipole size, the dipole strength, and the source surface radius where…
Peer Reviews
No public reviews on file for this paper yet. If you reviewed it on a platform where reviews are public (OpenReview, ICLR, NeurIPS, ICML), you can paste yours below so the community can read it here.
Videos
No videos yet. Explain this paper in a talk, walkthrough, or lecture? Add one.
