Analyses of solar coronal prominence cavities

Tuesday, October 16, 2012

Analyses of solar coronal prominence cavities by an international group of scientists including HAO's Sarah Gibson, Christian Bethge, Giuliana de Toma, Yuhong Fan, HAO visitor Urszula Bak Steslicka and University of Colorado graduate student Don Schmit, has been profiled in a NASA news release and UCAR AtmosNews research briefs.

Cavities ultimately may erupt as coronal mass ejections (CMEs), but only after days or weeks of existence as a strikingly organized, elliptical coronal structure. Probing the physical properties of prominence cavities provides clues to the magnetohydrodynamic equilibrium states that precede a CME. The NASA news release described a three-paper series by an international team of researchers that quantifies the morphological, density, and temperature structure within a coronal prominence cavity (Gibson et al., 2010, Schmit and Gibson, 2011, Kucera et al., 2012). UCAR AtmosNews highlighted new cavity observations from HAO's CoMP telescope which are providing evidence for the presence of twisted magnetic fields in the corona. See story in UCAR's AtmosNews. Also see NASA story.

Coronal Cavity image

Figure caption:

Top left: Modeled flux-rope field lines on the solar surface that provide an indication of how cavities within the corona may be aligned. The cartoon "eye" shows the line of sight from Earth (courtesy Yuhong Fan, NCAR).
Top right: The NCAR team's "forward model," predicting where a cavity will appear, matches well with the observation made by the CoMP instrument (courtesy Sarah Gibson, NCAR)
Bottom left: An observation in the extreme ultraviolet portion of the light spectrum by NASA's Solar Dynamic Observatory on May 25, 2011. The approximate center of a low-density coronal cavity (white diamond) and its approximate radius (turquoise line) are indicated (courtesy NASA).
Bottom right: An observation on the same date by NCAR's CoMP instrument shows the Sun's magnetic signature. Researchers are studying the relationship between this magnetic behavior, the presence of low-density coronal cavities, and the likelihood of a coronal mass ejection. The team has dubbed the observed pattern the "bunny head," with the head indicating the suspected location of the cavity and the ears being an artifact of the way we view these polarized signals from Earth (courtesy NCAR High Altitude Observatory).