The principle investigator (Dr. James C. LoPresto) began monitoring K-line and Ha plage (white patchy regions), sunspots, total solar magnetic flux, and Calcium K-line K2 variations in November of 1992. These measurements are still in progress and it is our intent and hope to continue them through the solar cycle 23 (to about the year 2005).
The data consists of binary images obtained via FTP Internet. K-line, Ha, and white light images are obtained from Big Bear Solar Observatory in Big Bear, California. Binary magnetograms are received from the Vacuum Telescope at National Solar Observatory on Kitt Peak in Tucson, Arizona. K-line Spectral data comes by direct observations made at the McMath-Pierce Telescope on Kitt Peak and the 10-inch Celeostat at Sacremento Peak Observatory in Sunspot, New Mexico. These later data are made available through the courtesy of Dr. William Livingston at Kitt Peak and Dr. Steven Keil at Scremento Peak.
If funding continues, we will continue to attempt to correlate the surface area (measured number of pixels) covered by plage on K-line and Ha images with total magnetic flux (sum of North and South magnetic poles) from Kitt Peak Vacuum Telescope magnetograms. In addition, correlations between changing plage area, total magnetic flux area, and changes in K-line K2 equivalent width will be sought.
Such correlations have already been made and the preliminary results are encouraging.
The plage pixel count is measured with image processing software on both PC and Macintosh computers. The K-line spectral data (K2 index) is measured with a spectral analyzing program called DECOMP and one-dimentional data routines on MIRA with the PC clone . These plage and magnetic flux pixel counts are correlated with one-another and the k-line spectral changes.
If the plage variation correlates well with the K-line K2 changes (which is has so far), and in turn changes in concert with the solar cycle, then a case can be made for the plage variations as a proxy for small amplitude solar irradiance changes. Do the plage counts also change with large amplitude irradiance changes? If so, a simple way to measure solar irradiance variations will exist and its applications to environmental dynamics such as global warming and ozone depletion goes without saying.
We are well on our way to obtaining our initial goals.
We have begun work on coronal brightpoint images. Susan Sheldon has conducted an INDEPENDENT STUDY on the ROTATION OF THE CORONA with the use of bright points on SOHO Fe XII 195 Angstrom UV images. The purpose of the study is to test the hypothesis that:
THE SOLAR CORONA ROTATES LIKE A RIGID BODY?
The rotation of the solar photosphere has been studied extensively by many workers since the time of Galileo in the early 17th Century. Over the years astronomers have gradually discovered the Sun's photospheric differential rotation. The equator rotates about once in 26 days, whereas the period of rotation decreases gradually to a period in excess of 30 days at latitudes higher than 80 degrees.
The SKYLAB mission provided some of the first striking images of the Sun's corona in X-RAY wavelengths. Among many features in such images are CORONAL HOLES and CORONAL BRIGHT POINTS. Coronal holes are regions in the corona wherein the magnetic lines of force are oriented straight outward away from the Sun. These regions with open magnetic fields are the source of outward moving charged particles known as the SOLAR WIND. These coronal holes have been used to measure the rotation of the corona. Results of such measurements imply the corona rotates like a rigid body. Since coronal holes tend to by very extensive in area, astronomers worry about the accuracy of the rotation rate they predict.
Coronal bright points are bright intense X-RAY and UV emitters. They appear to be locations of very small and intense bi-polar magnetic regions. Since they are small in extent, they might be useful in measuring the rotation of the corona? This is the subject of Susan Sheldon's independent study.
One disadvantage is that coronal bright points appear to have short lifetimes. Most are visible in SOHO UV images for about 1 day or less. Only a small fraction remain intact for two or more days. Nevertheless, they have been used to measure the rotation rate as a function of heliographic latitude. The method used is very simple. The program NIH IMAGE was used to measure the distance (radius vector) of the bright points from the solar disc center and the angle of the radius vector with respect to the solar rotation axis. These two quantities in turn were used to calculate the heleiographic latitude and longitude of the coronal bright points using well known transformation equations. The drift in longitude over successive images taken approximately one day apart where then used to calculate the number of degress of rotation per day. This in turn was converted into days of rotation at the bright point latitude.
Using two months of images (approximately 60 days) and about 200 coronal bright points, Susan Sheldon has come to the conclusion that the rotation rate of coronal bright points seems to be randomly correlated with heliographic latitude. This preliminary result tends to favor the hypothesis that THE CORONA ROTATES LIKE A RIGID BODY?
The image below shows a raw SOHO 195 Angstrom Image. The coronal bright points are the intense looking bright points.
The image below shows a SOHO working image, which shows an example bright point. The radius vector and the angle between Solar Heliographic North are indicated.
A graph of the coronal bright point rotation rate in days as a function of solar heliographic latitude is shown below.
LACK OF SUNSPOTS? Several people have noticed that no sunspots have appeared on the disc for more than 50 days. (55 days as of 10/26/96). The graph below shows that other indices of solar activity do not conform with this lack of sunspots. The plage from Halpha and Kline images from Big Bear Observatory and the plage from He II 304 SOHO images show quite a different picture of activity over the same time period.
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