Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 23, 2012 at 05:10 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]
Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was unsettled to minor storm on May 22. Solar wind speed at SOHO ranged between 355 and 478 km/s under the influence of a high speed stream from CH517.

Solar flux measured at 20h UTC on 2.8 GHz was 121.3 (decreasing 5.9 over the last solar rotation). The Potsdam WDC planetary A index was 25 (STAR Ap - based on the mean of three hour interval ap indices: 24.6). Three hour interval K indices: 34334454 (planetary), 24233433 (Boulder).

The background x-ray flux is at the class B3 level.

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

Region 11479 [N14W81] decayed slowly and quietly.
Region 11482 [N15W74] decayed further losing all trailing spots.
Region 11483 [S23W67] was quiet. New small spots emerged and disappeared during the day, there's some potential for development in this region.
Region 11484 [N12W40] was quiet and decayed slowly.
Region 11485 [S18W28] was quiet and stable.
Region 11486 [N16E14] was quiet and stable.
New region 11488 [N11E55] rotated into view on May 21 and was numbered the next day by SWPC.

Spotted active regions not numbered by NOAA/SWPC:
S1659
[N13W11] was quiet and stable.
S1670 [S30E54] was quiet and stable.
S1671 [S21E39] was quiet and stable.
New region S1674 [S21E54] emerged with a tiny spot.

Coronal mass ejections (CMEs)

May 20-22: 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 recurrent trans equatorial coronal hole (CH517) was in an Earth facing position on May 19-20. A coronal hole (CH518) in the northern hemisphere was in an Earth facing position on May 21 but may have been too far to the north to become geoeffective. A poorly defined trans equatorial coronal hole (CH519) will be 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 fair to good.

Forecast

The geomagnetic field is expected to be quiet to minor storm on May 23 and quiet to unsettled on May 24 due to effects from CH517. Effects from CH518 could cause some unsettled intervals on May 24-25 while CH519 could cause quiet to active conditions on May 26-28.

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
11479 2012.05.10
2012.05.11
1 1 1 N13W80 0030 HSX AXX

area: 0000

11482 2012.05.11
2012.05.13
4 9 4 N14W71 0240 DSO HHX

area: 0300

11483 2012.05.12
2012.05.13
4 12 3 S25W67 0010 BXO CRO location: S23W67
11481 2012.05.12
2012.05.13
      S10W64          

plage

location: S10W55

11484 2012.05.13 19 33 14 N10W43 0290 EAI DAI

location: N12W40

S1654 2012.05.14       S25W37           plage
S1659 2012.05.15   4   N13W11 0000   AXX  
S1661 2012.05.15       N33W49           plage
11485 2012.05.15   3   S20W29 0000   BXO location: S18W28
11486 2012.05.17
2012.05.18
2 10 5 N17E13 0200 HSX CSO  
S1663 2012.05.17       N12W19           plage
11487 2012.05.18
2012.05.20
      N18W33           plage

location: N20W30

S1666 2012.05.18       S19W17           plage
S1667 2012.05.19       N04E16           plage
S1668 2012.05.20       N13W32           plage
S1670 2012.05.21   3 1 S30E54 0010   BXO  
S1671 2012.05.21   2   S21E39 0000   AXX  
11488 2012.05.21
2012.05.22
5 6 3 N12E55 0010 BXO DRO  
S1673 2012.05.21       N27W29         plage
S1674 2012.05.22   1 1 S21E54 0000   AXX    
Total spot count: 35 84 32  
Sunspot number: 95 194 112  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 55 110 58  (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): 57 68 62 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
2012.05 125.1 (1) 75.7 (2A) / 106.7 (2B) (75.8 projected, +1.3) (10.26)

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.