AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 78. TRACE and Coronal Heating
Solar, Display, Wednesday, June 2, 1999, 10:00am-6:30pm, Southeast Exhibit Hall

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[78.04] Dynamics and Plasma Diagnostics of Transition Region ``Moss'' using SOHO/CDS, TRACE and SVST (La Palma)

B. De Pontieu (Stanford-Lockheed Institute for Space Research), T.E. Berger, L. Fletcher, C.J. Schrijver, A.M. Title (Lockheed-Martin Solar and Astrophysics Lab)

Recent observations of solar active regions with the Transition Region And Coronal Explorer (TRACE) have revealed finely textured, low-lying extreme ultraviolet (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 et al., (1999). In this poster we study the physical conditions in the moss plasma, as well as its dynamics and connections to photosphere and chromosphere. Using simultaneous SOHO Coronal Diagnostic Spectrometer (CDS) and TRACE observations of Active Region (AR) 8227 on 30-May-1998 we determine the physical parameters of the moss material. We find Te = 0.6-1.5~106~K and ne = 2-5~109 cm-3 at a temperature of 1.3~106~K. The pressure in the moss plasma is higher than that in coronal loops observed in the TRACE Fe IX/X 171~Å~passband, and moss emission is associated with high temperature loops, observed by SXT and by CDS in lines of T\rm max > 2.5~106~K. The volume filling factor of the moss plasma is of the order 0.1 and the path along which the emission originates is of the order 1,000 km long. We examine the dynamics of the moss plasma, by making comparisons of TRACE 171~Å~movies with SVST (La Palma) Ca II K-line, H\alpha, and G-band movies. Local Correlation Tracking (LCT) flowmapping techniques are used to establish the photospheric flowfield in plage regions with and without associated moss. The relation of moss emission to chromospheric spicules or fibrils is examined in detail using H\alpha movies and dopplergrams. In addition, several miniflare events occuring in plage regions are analyzed using TRACE and SVST movies. This research was supported by NASA contract NAS5-38099 (TRACE) and NASA SR&T grant NASW-98008.

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