Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 28, 2012 at 05:15 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 26, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on May 27. Solar wind speed at SOHO ranged between 339 and 379 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 110.7 (decreasing 3.4 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.6). Three hour interval K indices: 12211100 (planetary), 11011221 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight UTC the visible solar disk had 7 spotted active regions (in 2K resolution SDO images).

Region 11486 [N17W52] decayed slowly and quietly.
Region 11488 [N10W14] developed as spots became more organized both in the leading and trailing polarity area.
Region 11490 [S13E18] developed with more spots appearing and a significant increase in penumbral area.
Region 11491 [N23W56] decayed slowly and quietly.
Region 11492 [S13E47] extended longitudinally and added several spots. The region produced the only C flare of the day, a long duration C3.1 event peaking at 05:52 UTC. This event was associated with a CME off the east limb.

Spotted active regions not numbered by NOAA/SWPC:
S1686
[S19W00] developed slowly and quietly.
New region S1692 [S12E72] rotated into view with a small spot.

Coronal mass ejections (CMEs)

May 25-27: 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

No obvious coronal holes are currently in potentially geoeffective positions.

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 fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on May 28-31.

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
11486 2012.05.17
2012.05.18
1 1 1 N16W53 0080 HSX HSX area: 0200
S1667 2012.05.19       N04W49           plage
11489 2012.05.21
2012.05.22
3     S30E15 0010 BXO     plage

location: S23W10

Don't know what SWPC observed. No spots are visible at the reported location and there are no spots in the original location of AR 11489

S1671 2012.05.21       S19W24         plage
11488 2012.05.21
2012.05.22
3 25 16 N11W13 0010 BXO DRI location: N11E02

area: 0050

S1674 2012.05.22       S21W11           plage
11490 2012.05.23
2012.05.24
6 25 15 S12E17 0070 DSO DSI beta-gamma

area: 0110

S1676 2012.05.23       S10W18           plage
S1677 2012.05.23       N06W42           plage
11491 2012.05.23
2012.05.25
3 10 5 N22W56 0040 DSO CRO  
S1679 2012.05.23       N12W57           plage
S1680 2012.05.24       N12W42           plage
11492 2012.05.24
2012.05.25
7 26 10 S14E43 0190 EAO EKO

area: 0340

location: S13E47

S1682 2012.05.25       S22E49         plage
S1683 2012.05.25       N01E04           plage
S1684 2012.05.25       N21W07         plage
S1685 2012.05.25       S12W43           plage
S1686 2012.05.26   8 6 S19W00 0030   DRO  
S1687 2012.05.26       S28E05         plage
S1688 2012.05.26       N31W21         plage
S1689 2012.05.26       N17W78         plage
S1690 2012.05.26       S07E34         plage

reversed polarities

S1691 2012.05.26       S26E27         plage
S1692 2012.05.27   1 1 S12E72 0010   HRX    
Total spot count: 23 96 54  
Sunspot number: 83 166 124  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 43 128 86  (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 58 68 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
2012.05 123.1 (1) 89.0 (2A) / 102.2 (2B) (75.8 projected, +1.3) (8.74)

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.