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[88.07] Active Region Moss as a Diagnostic for the Thermal Evolution of Chromospheric Spicule-Like Jets, and for Coronal Heating.

B. De Pontieu, T. Tarbell (Lockheed Martin Solar & Astrophysics Lab)

The recent discovery of active region moss, i.e, dynamic and bright upper transition region emission at chromospheric heights above active region plage, provides a powerful diagnostic to probe the structure, dynamics, energetics and coupling of the magnetized solar chromosphere and transition region.

Here we present an observational study of the interaction of the chromosphere with the TR moss, using a 2 hour time sequence of high-cadence (30 s) TRACE C IV 1550 Å (0.1 MK), Fe IX/X 171 Å (1 MK) and Fe XII 195 Å (1.5 MK) images, as well as co-aligned, simultaneous SUMER spectra, and ground-based filtergrams from the Swedish Vacuum Solar Telescope (SVST, La Palma) in the wings of H-alpha. Detailed comparisons of the H-alpha filtergrams (at -700, -350, +350 and +700 mÅ) with the TRACE C IV images reveals that there is often a significant spatial correlation of the C IV emission with the highly redshifted fibril or spicule-like structures in H-alpha +700 mÅ. The discovery and detailed quantitative study of this correlation promises to shed light on the long outstanding issue of what role chromospheric spicule-like jets play in the heating and momentum balance of the outer atmosphere.

We have also quantitatively studied the auto-correlation and cross-correlation time-scales of moss using a time sequence of high cadence TRACE 171 Å and 195 Å images. In most of the active region moss patch we studied, we find that the emission of 1 and 1.5 MK plasma is highly correlated, but often with significant negative and positive time delays. Our results indicate that the footpoints of hot coronal loops seem to undergo frequent cooling and heating on time-scales of order fifteen minutes. By quantifying these variations we can shed light on the temporal variability and on the location of coronal heating in general.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.