skip to main content

SciTech ConnectSciTech Connect

Title: The solar chromosphere observed at 1 Hz and 0.''2 resolution

We recently reported extremely rapid changes in chromospheric fine structure observed using the IBIS instrument in the red wing of Hα. Here, we examine data obtained during the same observing run (2010 August 7), of a mature active region NOAA 11094. We analyze more IBIS data including wavelength scans and data from the Solar Dynamics Observatory, all from within a 30 minute interval. Using a slab radiative transfer model, we investigate the physical nature of fibrils in terms of tube-like versus sheet-like structures. Principal Component Analysis shows that the very rapid Hα variations in the line wings depend mostly on changes of line width and line shift, but for Ca II 854.2 the variations are dominated by changes in column densities. The tube model must be rejected for a small but significant class of fibrils undergoing very rapid changes. If our wing data arise from the same structures leading to 'type II spicules', our analysis calls into question much recent work. Instead, the data do not reject the hypothesis that some fibrils are optical superpositions of plasma collected into sheets. We review how Parker's theory of tangential discontinuities naturally leads to plasma collecting into sheets, and show that the sheetmore » picture is falsifiable. Chromospheric fine structures seem to be populated by both tubes and sheets. We assess the merits of spectral imaging versus slit spectroscopy for future studies.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. Smith College, 99 Paradise Road, Northampton, MA 01063 (United States)
  2. High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States)
  3. National Solar Observatory/Sacramento Peak, P.O. Box 62, Sunspot, NM 88349 (United States)
  4. INAF-Ossevatorio Astrofisico di Arcetri, I-50125 Firenze (Italy)
Publication Date:
OSTI Identifier:
22357096
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 785; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHROMOSPHERE; COHERENT TUBE MODEL; DENSITY; FINE STRUCTURE; HYPOTHESIS; LINE WIDTHS; MAGNETIC FIELDS; PLASMA; RADIANT HEAT TRANSFER; RESOLUTION; SOLAR PROMINENCES; SPECTROSCOPY; SUN; WAVELENGTHS