This data is used to study how the instruments change while they are on orbit. The most important science that comes out is whether the Sun is round or bulges a little bit at the waist. So far, it appears that the Sun bulges less than we expect and that bulge does not change very much as sunspots come and go. The only way to check is to redo the measurements at different times in the solar cycle. This set of points will be made at the maximum of Solar Cycle 24.
Tuesday, April 8, 2014
Thursday, April 3, 2014
Monday, March 31, 2014
The X-1 flare on Saturday produced a very nice example of coronal dimming. Here is a short movie showing five hours of the Sun in the AIA 193 passband. After the flare happens in the upper right quadrant at 1755 UTC on March 29, 2014, a dark region spreads over the north pole. This is a coronal dimming event. There are many ways to interpret these dimming events. Are they the edges of the coronal mass ejection that left the Sun at the time of the flare? Are they waves moving past magnetic field lines and making them sway? Whatever it is, it moves fast. Active Region 12017 is at 10°N 48°W. If something moves from there to the north pole of the Sun (90°N) in 45 minutes it had to move at about 360 km/s (800,000 mph). I only see the dimming moving north.
Wherever coronal dimmings come from, they look pretty cool.
Wednesday, March 26, 2014
Wednesday, March 12, 2014
January's 31 days are a little longer than one solar rotation of 27.27 days. That means you see a part of the Sun that is just off limb at the beginning of the month a second time as that part of the Sun rotates back into view. Active region 11944 is present throughout the month in the southern hemisphere and reappears as AR 11967 at the end of the movie. AR 11946 grows in the northern hemisphere and will reappear as AR 11968. AR 11944 will also return as AR 11990 in late February. On February 25 it will be the location of an X-4.9 flare as it rotates back into view.
Long-lived active regions are a sign that solar maximum is here and starting to fade.
Check it out!
Wednesday, March 5, 2014
Thursday, February 27, 2014
Here is an image from our first eclipse. It is always nice to see the ragged edge of the Earth's atmosphere as the bright spots on the Sun shine through while the dimmer regions disappear. Here we can see AR 11988 near the edge of the Earth, with a coronal hole just to the right. Active regions 11981-11984 are further to the right and are hardly affected by the Earth, although they soon disappear behind the Earth.
When SDO can't see the Sun we don't get data. Eclipses are one of our largest data holes. But the orbit gives us 24/7 access to the data flow. So far we have received 98% of the data, so the eclipses aren't a problem but they are pretty!