Solar Physics Seminar: Thomas Berger (Lockheed Martin Solar and Astrophysics Laboratory)

What	seminar
When	16 April 08 from 04:00 pm to 05:00 pm
Where	Physics & Astrophysics Conf. Room 232
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Buoyant plumes in solar prominences: Hinode/SOT observations of a new phenomenon on the Sun

We report new findings from multi-hour movies of solar quiescent

prominences (QPs) observed with the recently launched Solar Optical

Telescope (SOT) on the Hinode satellite. SOT is capable of observing

prominences for up to 6 hours with a spatial resolution of 0.22

arcseconds (160 km) and a temporal resolution of 15 seconds. The

image quality is uniform throughout all time series. SOT observations

verify previous ground-based observations of filamentary downflows as

well as large-scale vortex flows in QP sheets. SOT observations also

verify the existence of large-scale transverse ``body oscillations''

in QPs, with periods of 20--40 minutes and amplitudes of 5--10 Mm. We

measure the upward propagation speed of several waves to be ~10 km/

sec, consistent with the sound speed of a 10,000 K plasma. Most

surprisingly, SOT movies show that buoyant starting plumes occur

episodically in most QPs observed to date. The plumes are visible as

dark turbulent upflows plowing through the prominence plasma with

relatively constant ascent velocities of ~20 km/sec. The plumes are

200--700 km in width and sometimes exhibit "mushroom head" vortex

formation at the leading edge. The plumes rise to heights of ~10--20

Mm above the prominence base and are clearly visible in both Ca II

396.8 nm and H-alpha 656.3 nm images. The plumes are never seen in

active region prominences or in QPs with horizontal thread

structuring. We discuss possible mechanisms for the plume formation

as well as the structural and dynamic differences between active

region and quiescent prominences in the SOT database.

July 2008

KIPAC