Monday, October 27, 2014
I downloaded the active region dataset produced by David Hathaway at Marshall SFC and looked at the largest active regions since 1874. This area data comes from the photographs taken at the Royal Greenwich Observatory until 1976 and various sources after that. I checked the list against the tables in Sunspot and Geomagnetic-Storm Data by Sir H. Spencer Jones just to make sure. I also added two regions from 2014 (AR 12192, of course, and AR 11967). Areas of active regions are measured in micro-hems (millionths of a solar hemisphere, where 1 micro-hem is about 1.54 million sq km.)
The yearly Sunspot Number is drawn as a red line. This allows you compare how the maximum area of active regions changes with the number of active regions. It was surprising that the largest active regions are not in Solar Cycle 19, which has the largest amplitude in Sunspot Number, but in Solar Cycle 18. The top 5 active regions appeared between 1946 and 1951. Solar Cycle 19 started in 1954. The next set of large active regions have areas of 3000-4000 micro-hems and are spread across many sunspot cycles.
How big was the active region that was the site of the Carrington Flare? It was 2300 micro-hems, not even in the top 50! You can look it up on p. 102 of the table by Jones. The flare on 1-Sep-1859 has been estimated at X35, showing that large flares can come from medium-sized active regions.
So long for now to AR 12192 but perhaps we will see you next rotation!
Wednesday, October 22, 2014
This active region has caused a "Major Flare Watch" to be declared, so the two calibration maneuvers SDO had scheduled for today will be done in two weeks. Here is a summary of our projected activities for the rest of 2014.
- 10/20/2014: Null Bias Application
- 10/29/2014: EVE Cruciform (@1800ut)
- 10/30/2014: Null Bias Removal
- 11/05/2014: EVE FOV (1315-1537 UTC) and HMI/AIA Flatfield (1630-1907 UTC) Calibration Maneuvers
- 11/12/2014: Null Bias Application
- 11/22/2014: Lunar Transit (2229-2304 UTC)
- 12/01/2014: Null Bias Removal