Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 25, 2012 at 03:45 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update May 3, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 3, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 3, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 3, 2012)]

[POES auroral activity level since October 2009 - updated May 19, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on May 24. Solar wind speed at SOHO ranged between 475 and 568 km/s, at first under the influence of a high speed stream from CH517. ACE data indicates a change in the main solar wind source to CH518 after 17h UTC.

Solar flux measured at 20h UTC on 2.8 GHz was 115.5 (decreasing 2.6 over the last solar rotation). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 7.6). Three hour interval K indices: 22322221 (planetary), 23322322 (Boulder).

The background x-ray flux is at the class B5 level.

At midnight UTC the visible solar disk had 11 spotted active regions (in 2K resolution SDO images).

Region 11484 [N11W68] developed again and became a compact region capable of producing minor M class flares.
Region 11486 [N17W12] was quiet and stable.
Region 11488 [N11E28] has many small spots and produced the only flare of interest during the day, a C3.9 event at 20:09 UTC.
Region 11489 [S28E33] reemerged with a few small spots.
New region 11490 [S13E58] emerged near the east limb n May 23 and was numbered the next day by SWPC.

Spotted active regions not numbered by NOAA/SWPC:
S1659
[N14W24] was quiet and stable.
S1671 [S18E25] was quiet and stable.
S1673 [N24W60] reemerged with small spots.
S1678 [N22W17] developed slowly and quietly. A C1.1 flare was observed early on May 25.
New region S1680 [N12W03] emerged with a tiny spot.
New region S1681 [S13E83] rotated into view at the southeast limb.

Coronal mass ejections (CMEs)

May 22-24: No obviously Earth directed CMEs were observed in LASCO or STEREO imagery.

Coronal holes

Coronal hole history (since October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A coronal hole (CH518) in the northern hemisphere was in an Earth facing position on May 21. A poorly defined southern hemisphere coronal hole (CH519) was Earth facing on May 23-24.

Coronal hole map

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using this method, the extent and intensity of both CHs are consistent with other data sources.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on May 25 due to effects from CH518 and quiet to unsettled on May 26-28 due to weak effects from CH519, occasional active intervals are possible.

Coronal holes (1) Coronal mass ejection (2) M and X class flares (3)
     

1) Effects from a coronal hole could reach Earth within the next 5 days. When the high speed stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.

Green: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.

Active solar regions

Click on image for higher resolution image) Compare to the previous day's image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) is positive.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.

Active region Date numbered
detected
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
2K 1K
11483 2012.05.12
2012.05.13
5     S25W93 0010 BXO     rotated out of view
11484 2012.05.13 8 14 9 N09W68 0150 DSO DAC

location: N11W68

area: 0270

S1659 2012.05.15   2   N14W23 0000   BXO  
11485 2012.05.15       S20W57           plage

location: S18W54

11486 2012.05.17
2012.05.18
2 8 6 N18W14 0110 CSO CSO area: 0240

location: N17W12

S1663 2012.05.17       N12W45           plage
11487 2012.05.18
2012.05.20
      N18W61           plage

location: N20W56

S1666 2012.05.18       S19W43           plage
S1667 2012.05.19       N04W10           plage
S1668 2012.05.20       N13W58           plage
11489 2012.05.21
2012.05.22
1 4 3 S30E26 0000 AXX BXO   location: S28E33
S1671 2012.05.21   1 1 S18E11 0000   AXX  
11488 2012.05.21
2012.05.22
4 19 9 N11E27 0010 BXO BXI  
S1673 2012.05.21   2 1 N24W60          
S1674 2012.05.22       S21E28           plage
11490 2012.05.23
2012.05.24
3 9 3 S12E58 0030 CRO DRO  
S1676 2012.05.23       S10E21         plage
S1677 2012.05.23       N06W03         plage
S1678 2012.05.23   10 5 N22W17 0030   DRI  
S1679 2012.05.23       N12W18         plage
S1680 2012.05.24   1 1 N12W03 0000   AXX    
S1681 2012.05.24   2 1 S13E83 0010   BXO    
Total spot count: 23 72 39  
Sunspot number: 83 182 139  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 36 88 55  (Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 50 64 76 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) for STAR SDO 2K, k = 0.55 for STAR SDO 1K

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
(3)
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
 
2011.02 94.6 29.4 33.4 (+2.4)  6.44
2011.03 115.0 56.2 36.9 (+3.5) 8.18
2011.04 112.6 54.4 41.8 (+4.9) 8.83
2011.05 95.8 41.6 47.6 (+5.8) 8.94
2011.06 95.8 37.0 53.2 (+5.6) 8.06
2011.07 94.2 43.9 57.2 (+4.0) 8.16
2011.08 101.7 50.6 59.0 (+1.8) 7.26
2011.09 133.8 78.0 59.5 (+0.5) 12.27
2011.10 137.3 88.0 59.9 (+0.4) 8.28
2011.11 153.5 96.7 (61.2 projected, +1.3) 5.55
2011.12 141.3 73.0 (63.9 projected, +2.7) 3.78
2012.01 132.5 58.3 (67.4 projected, +3.5) 7.15
2012.02 106.5 33.1 (71.4 projected, +4.0) 8.81
2012.03 114.7 64.2 (73.5 projected, +2.1) 16.08
2012.04 113.0 55.2 (74.5 projected, +1.0) 10.10
2012.05 124.4 (1) 81.3 (2A) / 105.4 (2B) (75.8 projected, +1.3) (9.01)

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official SIDC international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international Potsdam WDC ap indices.

This report has been prepared by Jan Alvestad. It is based on analysis of data from whatever sources are available at the time the report is prepared. All time references are to the UTC day. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.