Click to enlarge
Solar magnetogram from http://www.solen.info for the same day (http://www.solen.info/solar/images/AR_CH_20140913.jpg). Sunspots are labelled as 5 digits
blue = N magnetic pole and pink = S magnetic pole.
I was looking through some old images and thought there were some bright points lurking around a sunspot (AR 2158) in one of my Calcium K images. So I decided to reprocess the image and enhance lighter grey shades to try and bring out these features. There’s not a lot out there about processing Calcium K images, so I include a screenshot of how I enhanced the image in Registax 6.
When this was completed, I could see a lot of small, intense white spots around the sunspot. I wasn’t sure what these were so I asked on the Imaging Solar section of “Stargazers Lounge” (http://stargazerslounge.com/forum/92-imaging-solar/), an online forum for astronomers.
A very expert solar astronomer and winner of Astronomy Photographer of the Year for her solar photographs, Alexandra Hart (flickr feed here: https://www.flickr.com/photos/alexandra4), kindly told me that these are areas of intense magnetic fields where arch filaments rise up from the surface of the sun – these are known as arch filament foot points and correspond to the ends of long filaments seen on hydrogen alpha images.
Occasionally, there can be magnetic reconnection of field lines that cause micro-flares – these also show up as bright white points but are transient over the course of 10 – 20 minutes. These were first spotted by an astronomer called Ellerman and he thought they resembled the atomic bombs that were being tested at that time. The only way to confirm if one of these bright spots is an Ellerman bomb is to do 2 runs about 20 minutes apart and see if any of the bright spots disappear or new spots appear for the 1st time. Those that remain unchanged are arch filament foot points and any transient spots are Ellerman bombs.
I’m very pleased that I can I get to this level of detail in my Calcium K imaging and it is certainly very encouraging for me. At some stage, I want to start hydrogen alpha imaging but for now, I’m happy to improve the quality of my white light and calcium K images.
1000/102mm refractor, Lunt B1200 CaK module, Baader K line filter, Skyris 274m CCD camera, Astro Hutech solar guider, Ioptron ZEQ25GT mount.