Gravitational Steady States of Coronal Loops as Magnetic Flux Ropes
Abstract
Many coronal loops observed on the surface of the sun appear to bemagnetic flux ropes containing plasma, with ends tied in the photosphere. Different types of loops contribute to important solar processes, but relatively little is known about their configuration.Like all toroidal confined, curved plasmas carrying current,they are intrinsically unstable to expansion in major radius.Consistent 3D MHD steady states are derived for the coronal partof the loop, including non-negligible effects due to the plasma pressure and solar gravity. Most loops have relativelyslender inverse aspect ratios ɛ =a/R≤ 1.For predominantly simple, non-helical loops, three gravitationally stabilized asymptotic solutions can be foundthat can be related to toroidal magnetically confined plasams.Comparison to observations shows thattwo solutions bracket the observed heights R<108m of the common thin coronal loops (ɛ ∼ 0.02) in solar active regions.The third solution better describes the fatter loops (ɛ ∼ 0.1)that sometimes appear along the magnetic neutral line in an active regionand grow to produce solar flares or coronal mass ejections.Since radial expansion is higher order than the basic flux ropeconfinement, the states also approximately describe radially unstable loops over similar heights.The solutions can also be generalized to other stabilizing mechanismsand may provide a useful basis for studies of loop dynamics.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMSH51F2649S
- Keywords:
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- 2109 Discontinuities;
- INTERPLANETARY PHYSICSDE: 2114 Energetic particles;
- INTERPLANETARY PHYSICSDE: 2149 MHD waves and turbulence;
- INTERPLANETARY PHYSICSDE: 7835 Magnetic reconnection;
- SPACE PLASMA PHYSICS