Coronal loop widths and pressure scale heights

Abstract

The scale heights of stratification and the widths of steady solar coronal loops exhibit properties unexplained by standard theory: observed scale heights are often much greater than static theory predicts, while the nearly-constant widths of loop emission signatures defy theoretical expectations for large flux tubes in stratified media. In this work we relate the cross-sectional profile of a coronal flux tube to its density scale height in steady-state plasma flow regimes. Steady flows may shorten or lengthen the scale height according to how the tube cross-sectional area varies with arclength. In a near-potential corona the flux tubes are expected to be sufficiently expansive in many active regions for scale heights to be increased by steady flows. On the other hand, cases where scale lengths are actually increased to observed sizes form a small part of the solution space, close to regimes where density profiles reverse. Therefore, although steady flows are the only steady process known to be capable of extending scale heights significantly, they are not expected to be not responsible for the majority of extended active region scale heights.

References in corpus (9)

• Temperature and Emission-Measure Profiles Along Long-Lived Solar Coronal Loops Observed with TRACE
• An Ab Initio approach to Solar Coronal Loops
• Systematic construction of exact MHD models for astrophysical winds and jets
• TRACE-derived temperature and emission measure profiles along long-lived coronal loops: the role of filamentation
• The Magnetic Structure of Coronal Loops Observed by TRACE
• The Effect of Hydrostatic Weighting on the Vertical Temperature Structure of the Solar Corona
• Systematic Construction of Exact 2-D MHD Equilibria with Steady, Compressible Flow in Cartesian Geometry and Uniform Gravity
• 2D MHD modelling of compressible and heated coronal loops obtained via nonlinear separation of variables and compared to TRACE and SoHO observations
• A solar active region loop compared with a 2D MHD model

Cited by in corpus (4)

• The Width Distribution of Loops and Strands in the Solar Corona -- Are we Hitting Rock Bottom ?
• An ultra-long and quite thin coronal loop without significant expansion
• On the Area Expansion of Magnetic Flux-Tubes in Solar Active Regions
• Solving the Coronal Heating Problem using X-ray Microcalorimeters