Prominences consist of partially ionized gas at chromospheric temperatures of ~10,000 K at heights of 10--30 Mm above the photosphere - heights normally associated with fully-ionized 1,000,000 K coronal plasma. Quiescent prominences (QPs) occur primarily at high latitudes over the polarity inversion line (PIL) between network patches of opposite polarity. Hinode/SOT observations to date show that QPs are highly dynamic with vertical downflows confined in narrow "streams", intermittent turbulent upflows seen in the form of dark plumes rising through the bright prominence emission (Berger et al., 2008), vortex flows that can span several Mm in diameter, and occasional large "bubble" instabilities that can temporarily disrupt the large-scale structure of the prominence (deToma et al. 2008). Understanding prominence dynamics, and in particular instability modes, is crucial to further study of Coronal Mass Ejections, the cores of which often contain prominence mass launched within the CME.
This HOP seeks to understand further the structure and dynamics of QPs, and in particular the origin of the dark turbulent upflows and large bubble instabilities. Berger et al. (2009) have established that a magnetic Rayleigh-Taylor instability is the mechanism responsible for plume formation. In this finding, the plumes are generated from cavities that emerge from below the prominence and then undergo RT instability on the cavity/prominence interface. The larger bubbles are cavities that do not undergo RT instability for some as-yet-unknown reason. The cavities/bubbles are currently thought to be emerging twisted flux ropes but this remains to be observationally verified. We also speculate that the cavities/bubbles are thermally enhanced regions such that the buoyancy driving the RT instability is both magnetic and thermal in origin.
Due to the limited wavelength choices in the Hinode/SOT instrument, we seek coordinated observations with the TRACE, SOHO/SUMER and STEREO/SECCHI instruments in order to achieve an expanded spectral range and thus measure the temperature and density in the cavities/bubbles. TRACE will provide 171A and/or 195A absorption images, SUMER will provide high spectral resolution scans in transition region lines such as C III 1175A, and SECCHI will provide high cadence He II 304A movies.The use of ground-based telescopes such as the Swedish Solar Telescope (SST) and Dutch Open Telescope (DOT) on La Palma allow the possibility of higher spatial resolution (SST) and cadence observations than can be achieved with SOT.
This HOP should be used for prominences on the limb. It should be coordinated with HOP 139 which observes filaments on the disk. The ideal sequence would thus be to track a filament from disk center using HOP 139 and then switch to HOP 73 when the filament becomes a prominence above the limb.
Note that as of December 2009 we have removed the on-disk component of this HOP in favor of HOP 139.
Berger, T. E. et al., ApJ, 676, L89, 2008.
Berger, T. E. et al., ApJ, submitted 2009.
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De Toma, G. et al., ApJ Letters, submitted, 2008.
Merenda, L. et al., ApJ, 642, 554, 2006. |
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