Today's Maneuvers

Today, 23-Apr-2014, SDO will perform two maneuvers. First up is the EVE Field of View, starting at 1315 UTC (9:15 am ET). Second is the HMI/AIA Flatfield, starting at 1630 UTC (12:30 pm ET). During these maneuvers the Sun will dance about in the SDO images. These maneuvers are used to keep the instruments well calibrated.

An Astronomical Picture of SDO

One of the cool things about knowing astronomers is the clever things they do with cameras. Here is one example. William Livingston, a solar astronomer living in Tucson, AZ, has taken pictures of the geostationary satellite ring since about 2001. These satellites tend to be big, and stay in one place over the Earth. By taking a long exposure (here about 9 hours), the satellites are almost points of light while the stars are long trails. (A nine hour star trail would cover 135 degrees of the sky.) Here is an example from March 2014. You can see 40 satellites in the center of the picture, all but one labeled with their name. SDO orbits the Sun every 24 hours, but at an angle to where these satellites orbit. Because it does not hover over the same place on Earth, SDO moves up and down through the geostationary satellites every day. So SDO isn't a point of light, it is another trail moving across the star trails. To help you find it, SDO is labeled on the plot. It is the very faint trail moving downward from between DirecTV 11 and DirecTV 8 to the l in Solar.

Dr. Livingston has been taking these pictures since 2001. I found a link about some of his first pictures. Another link describes the settings for digital cameras if you want to try to take pictures yourself. You'll need a dark sky and a steady mount!

Thanks to Bill for sending me these pictures.

HMI Roll Tonight

Tonight, April 9, 2014, from 0519-1200 UTC (1:19 am - 8:00 am ET). SDO will execute the HMI Roll maneuver. The spacecraft will spin 360 degrees about the line to the Sun center. It stops along the way to collect a few images at each of the points. Usually the near-realtime images that are served from the SDO website are "de-rotated", but sometimes we get the watch the Sun spin around.

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.

EVE Cruciform on April 2, 2014

Yesterday, between 1730 and 2230 UTC (1:30 pm to 6:30 pm ET) SDO did the EVE cruciform maneuver. SDO nods back and forth and up and down. Here is an example of an AIA image taken while SDO was moving, blurred by that motion. These maneuvers allow the EVE science team to maintain the accuracy of their measurements. Accurate measurements allow them to study how much energy is released in late-phase flares and other solar events.

X-1 Flare Yesterday with a Nice Coronal Dimming

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.

Momentum Management Maneuver Today

Today at 1840 UTC (2:40 pm ET) SDO will execute a momentum management maneuver. For about 45 minutes from 1815 to 1900 UTC SDO data may be unavailable.

SDO on the Astronomy Picture of the Day

An very nice animation of SDO images for the month of January 2014 is featured on the Astronomy Picture of the Day for March 12, 2014. The images show the brighter active latitudes on either side of the equator, a coronal hole in the northern hemisphere, and filaments covering the disk of the Sun. In the HMI visible light image in the six-image montage you can see the sunspots that make up the active regions. The image is too small to see the faculae that go along with sunspots, but the latest HMI flattened image shows them quite well.

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!