How to Observe the Sun Safely by Lee Macdonald

Author:Lee Macdonald
Language: eng
Format: epub
Publisher: Springer New York, New York, NY

If you observe the Sun with a suitable H-alpha instrument on almost any day you will probably notice at least one or two sinuous, dark lines on the disc that are not visible in white light (Fig. 6.3). These are called filaments and are simply prominences seen silhouetted against the disc. More strictly, we should say that they are seen in absorption, as they are cooler and less dense than the chromosphere beneath them and so absorb some of the light from the chromosphere. It is sometimes possible to see their true nature yourself when a filament close to the limb extends into the darkness above the limb, and part of it shows up as a prominence. Such a combined filament and prominence is sometimes known informally as a “filaprom” (Fig. 6.4). Like prominences, filaments are often associated with sunspots and sometimes appear to be entangled with sunspot groups, but on many occasions they occur well away from any spots and at high latitudes, where spots seldom or never form.

Fig. 6.3The Sun’s disc in hydrogen-alpha. The dark linear features are filaments (i.e., prominences seen in absorption against the disc), and the bright regions are plages. Whole-disc mosaic image by Dave Tyler

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.