Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 26, 2012 at 04:10 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update March 2, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update March 2, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update March 2, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update March 1, 2012)]

[POES auroral activity level since October 2009 - updated March 25, 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 quiet to unsettled on March 25. Solar wind speed at SOHO ranged between 352 and 420 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 101.3 (decreasing 3.2 over the last solar rotation). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.0). Three hour interval K indices: 32322100 (planetary), 21312211 (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 11438 [S14E04] decayed slowly and was mostly quiet.
Region 11440 [S25W79] was quiet and stable.
Region 11442 [N12E08] reemerged with a single small spot.
Region 11443 [N16E28] added a small trailing spot and was quiet.
Region 11444 [N20E12] decayed slowly with no rudimentary penumbra visible.  Flare: C3.0/1N at 00:28 UTC
Region 11445 [S23E52] increased penumbral area on the leader spots. C and minor M class flares are possible. Flare: C2.5 at 01:57 UTC

Spotted regions not reported by NOAA/SWPC:
[S1548] emerged in the northeast quadrant on March 23. Location at midnight: N12E18

Coronal mass ejections (CMEs)

March 23-25: No obviously Earth directed CMEs were observed in LASCO and 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 (CH509) was in an Earth facing position on March 23-25.

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

Forecast

The geomagnetic field is expected to be quiet to active on March 26-28 due to a high speed stream from CH509.

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
11436 2012.03.15
2012.03.16
      S14W62           plage
S1533 2012.03.18       N23W42           plage
S1534 2012.03.18       N13W52           plage
11438 2012.03.19
2012.03.20
2 3 2 S17E02 0020 HSX HRX location: S14E04
11440 2012.03.19
2012.03.21
2 2 1 S25W79 0020 HRX BXO  
S1539 2012.03.20       N05W40           plage
11442 2012.03.21
2012.03.22
  1 1 N13E08 0000   AXX    
11443 2012.03.21
2012.03.22
1 3 2 N16E25 0000 AXX BXO location: N16E28
11444 2012.03.22
2012.03.23
7 14 7 N19E11 0060 CAO BXI reversed polarities

area: 0010

11446 2012.03.22
2012.03.25
4     N23W27 0010 BXO     spotless
11445 2012.03.23 8 15 5 S24E52 0280 FHO FHO

area: 0300

S1545 2012.03.23       S28W26           plage
S1547 2012.03.23       N29E16         plage
S1548 2012.03.23   3 3 N12E15 0010   BXO  
S1550 2012.03.24       S18E36         plage
Total spot count: 24 41 21  
Sunspot number: 84 111 91  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 47 54 34  (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 39 50 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
 
2010.12 84.2 14.4 28.8 (+2.3) 4.35
2011.01 83.6 19.1 31.0 (+2.2) 5.51
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 (59.2 projected, +0.2) 12.27
2011.10 137.3 88.0 (59.4 projected, +0.2) 8.28
2011.11 153.5 96.7 (60.8 projected, +1.4) 5.55
2011.12 141.3 73.0 (63.6 projected, +2.8) 3.78
2012.01 132.5 58.3 (67.1 projected, +3.5) 7.15
2012.02 106.5 33.1 (71.0 projected, +3.9) 8.81
2012.03 116.3 (1) 61.7 (2A) / 76.6 (2B) (73.2 projected, +2.2) (23.07)

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 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.