Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 31, 2013 at 06:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update March 1, 2013)] [Cycle 24 progress (last update March 2, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update March 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update March 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update March 1, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated March 24, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet to minor storm on March 30. Solar wind speed at SOHO ranged between 476 and 568 km/s under the influence of a high speed stream from CH562.

Solar flux measured at 20h UTC on 2.8 GHz was 108.4 (decreasing 3.6 over the last solar rotation). The Potsdam WDC planetary A index was 16 (STAR Ap - based on the mean of three hour interval ap indices: 16.5). Three hour interval K indices: 55212132 (planetary), 54222231 (Boulder).

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

At midnight UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).

Region 11704 [N15W20] was quiet and stable.
Region 11705 [S11W47] reemerged with a few spots.
Region 11706 [S06W36] was quiet and stable.
Region 11707 [S10E02] decayed slowly and quietly.
Region 11708 [N11E45] was quiet and stable.
Region 11710 [S21E32] was quiet and stable.
New region 11711 [S18E76] rotated fully into view. While the region was quiet, C and M class flares are possible.

Spotted regions not numbered by SWPC:
New region S2326 [N02E52] emerged with penumbra spots.

Coronal mass ejections (CMEs)

March 28-30: 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 (CH562) was in an Earth facing position on March 25-27. A recurrent northern hemisphere coronal hole (CH563) was in an Earth facing position on March 28.

Coronal hole map

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.

Forecast

The geomagnetic field is expected to be quiet to unsettled on March 31 - April 1 due to effects from CH562/563 and quiet on April 2.

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 2K resolution) Compare to the previous day's image. 0.5k image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue 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
11704 2013.03.23 3 12 2 N15W21 0070 HAX CSO area: 0120
11705 2013.03.24
2013.03.25
  3   S12W52 0007   AXX   location: S11W47
S2314 2013.03.25       S18E12           plage
11706 2013.03.26
2013.03.27
  2   S06W39 0004   BXO location: S06W36
11709 2013.03.26
2013.03.29
      S33W35         plage
11708 2013.03.27
2013.03.28
4 12 5 N11E45 0090 CSO DSO  
S2318 2013.03.27       N16W50           plage
11707 2013.03.28 2 5 3 S11E04 0040 HAX CAO  
11710 2013.03.28
2013.03.29
7 14 6 S21W34 0070 CAO DAO

location: S21E32

S2321 2013.03.28       S15E39           plage
S2322 2013.03.28       S14W10           plage
S2323 2013.03.28       S12W38           plage
11711 2013.03.29
2013.03.30
4 8 3 S17E77 0210 CAI CKO location: S18E76

area: 0450

S2326 2013.03.30   3 1 N02E52 0009   BXO    
Total spot count: 20 59 20  
Sunspot number: 70 139 80  (total spot count + 10 * number of spotted regions)
Weighted SN: 45 89 50  (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): 42 49 44 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 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)
2011.11 153.5 (cycle max) 96.7 (cycle max) 61.1 (+1.2) 5.55
2011.12 141.3 73.0 63.4 (+2.3) 3.78
2012.01 132.5 58.3 65.5 (+2.1) 7.15
2012.02 106.5 32.9 66.9 (+1.4)
possible cycle 24 max
8.81
2012.03 114.7 64.3 66.8 (-0.1) 16.08
2012.04 113.0 55.2 64.6 (-2.2) 10.10
2012.05 121.5 69.0 61.7 (-2.9) 7.06
2012.06 119.6 64.5 58.9 (-2.8) 10.08
2012.07 133.9 66.5 57.7 (-1.2) 13.90
2012.08 115.4 63.0 58.1 (+0.4) 7.96
2012.09 122.9 61.4 (57.9 projected, -0.2) 8.07
2012.10 123.3 53.3 (57.0 projected, -0.9) 9.97
2012.11 121.3 61.8 (56.1 projected, -0.9) 7.08
2012.12 108.6 40.8 (54.9 projected, -1.2) 3.44
2013.01 127.1 62.9 (53.6 projected, -1.3) 4.69
2013.02 104.3 38.0 (52.5 projected, -1.1) 6.11
2013.03 111.2 (1) 78.4 (2A) / 81.0 (2B) / 50.9 (2C) (51.5 projected, -1.0) (10.07)

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) Boulder SN current month average to date. 2C) STAR SDO 1K Wolf number 30 day average.
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.