Plasma diagnostics of transition region 'Moss' using SOHO/CDS and TRACE

Fletcher, L. and De Depontieu, B. (1999) Plasma diagnostics of transition region 'Moss' using SOHO/CDS and TRACE. Astrophysical Journal Letters, 520(2), L135-L138. (doi: 10.1086/312157)

Abstract

Recent observations of solar active regions with the Transition Region and Coronal Explorer (TRACE) have revealed finely textured, low-lying EUV emission, called the ``moss,'' appearing as a bright dynamic pattern with dark inclusions. The moss has been interpreted as the upper transition region by Berger and coworkers. In this study we use SOHO Coronal Diagnostic Spectrometer and TRACE observations of Active Region 8227 on 1998 May 30 to determine the physical parameters of the moss material. We establish that the plasma responsible for the moss emission has a temperature range of (0.6-1.5)x10^6 K and is associated with hot loops (T>2x10^6 K). Moss plasma has an electron density of (2-5)x10^9 cm^-3 at a temperature of 1.3x10^6 K, giving a pressure of 0.7-1.7 dynes cm^-2 (a few times higher than in coronal loops observed in the TRACE Fe IX/X lambda171 passband). The volume filling factor of the moss plasma is of order 0.1, and the path along which the emission originates is of order 1000 km long.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Fletcher, Professor Lyndsay
• Authors: Fletcher, L., and De Depontieu, B.
• Subjects: Q Science > QB Astronomy; Q Science > QC Physics
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Research Group: Astronomy and Astrophysics
• Journal Name: Astrophysical Journal Letters
• Journal Abbr.: Ap.J.Letts.
• Publisher: American Astronomical Society
• ISSN: 2041-8205
• ISSN (Online): 2041-8213
• Copyright Holders: Copyright © 1999 American Astronomical Society
• First Published: First published in Astronomy and Astrophysics 520(2):L135-L138
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher