Microwave depolarization above sunspots

Document Type

Conference Proceeding

Publication Date

8-1-2010

Abstract

Microwave emissions from sunspots are circularly polarized in the sense of rotation (right or left) determined by the polarity (north or south) of coronal magnetic fields. However, they may convert into unpolarized emissions under certain conditions of magnetic field and electron density in the corona, and this phenomenon of depolarization could be used to derive those parameters. We propose another diagnostic use of microwave depolarization based on the fact that an observed depolarization strip actually represents the coronal magnetic polarity inversion line (PIL) at the heights of effective mode coupling, and its location itself carries information on the distribution of magnetic polarity in the corona. To demonstrate this diagnostic utility we generate a set of magnetic field models for a complex active region with the observed line-of-sight magnetic fields but varying current density distribution and compare them with the 4.9 GHz polarization map obtained with the Very Large Array (VLA). The field extrapolation predicts very different locations of the depolarization strip in the corona depending on the amount of electric currents assumed to exist in the photosphere. Such high sensitivity of microwave depolarization to the coronal magnetic field can therefore be useful for validating electric current density maps inferred from vector magnetic fields observed in the photosphere. © International Astronomical Union 2011.

Identifier

84883024988 (Scopus)

ISBN

[9780521760621]

Publication Title

Proceedings of the International Astronomical Union

External Full Text Location

https://doi.org/10.1017/S1743921311015857

e-ISSN

17439221

ISSN

17439213

First Page

487

Last Page

490

Issue

S273

Volume

6

Grant

AST 0968672

Fund Ref

National Science Foundation

This document is currently not available here.

Share

COinS