Observations of Low-Latitude Coronal Plumes |
| |
Authors: | Y-M Wang K Muglach |
| |
Institution: | (1) Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352, USA;(2) ARTEP, Inc., Ellicott City, MD 21042, USA |
| |
Abstract: | Using Fe ix/x 17.1 nm observations from the Extreme-Ultraviolet Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO), we have identified many coronal plumes inside low-latitude coronal holes as they transited the solar limb during the late
declining phase of cycle 23. These diffuse, linear features appear to be completely analogous to the familiar polar plumes.
By tracking them as they rotate from the limb onto the disk (or vice versa), we confirm that EUV plumes seen against the disk appear as faint, diffuse blobs of emission surrounding a brighter core.
When the EIT images are compared with near-simultaneous magnetograms from the SOHO Michelson Doppler Imager (MDI), the low-latitude, on-disk plumes are found to overlie regions of mixed polarity, where small
bipoles are in contact with unipolar flux concentrations inside the coronal hole. The birth and decay of the plumes are shown
to be closely related to the emergence of ephemeral regions, their dispersal in the supergranular flow field, and the cancellation
of the minority-polarity flux against the dominant-polarity network elements. In addition to the faint polar and nonpolar
plumes associated with ephemeral regions, we note the existence of two topologically similar coronal structures: the giant
plume-like features that occur above active regions inside coronal holes, and the even larger scale “pseudostreamers” that
separate coronal holes of the same polarity. In all three cases, the basic structure consists of open field lines of a given
polarity overlying a photospheric region of the opposite polarity; ongoing interchange reconnection at the X-point separating
the open field domains from the underlying double-arcade system appears to result in the steady evaporation of material from
the closed into the open region. |
| |
Keywords: | Corona structures Coronal holes Magnetic fields corona Magnetic fields photosphere Magnetic reconnection observational signatures |
本文献已被 SpringerLink 等数据库收录! |
|