Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 25, 2013 at 03:55 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 on March 24. Solar wind speed at SOHO ranged between 346 and 430 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 96.0 (decreasing 2.7 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: 4.5). Three hour interval K indices: 21111110 (planetary), 21322221 (Boulder).

The background x-ray flux was at the class B1 level.

At midnight UTC the visible solar disk had 5 spotted active regions (in 2K resolution SDO images).

Region 11702 [N08W67] decayed slowly and quietly.
Region 11703 [S27W82] decayed slowly and quietly.
Region 11704 [N15E59] was quiet and stable.

Spotted regions not numbered by SWPC:
S2310 [S22E13] was quiet and stable.
New region S2313 [S12E33] emerged with several spots.

Coronal mass ejections (CMEs)

March 22-24: 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) will likely rotate into an Earth facing position on March 25-26. A recurrent northern hemisphere coronal hole (CH563) could rotate into 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 poor.

Forecast

The geomagnetic field is expected to be quiet on March 25-27. A high speed stream from CH562 could cause quiet to active conditions on March 28-29.

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
11700 2013.03.15
2013.03.17
      S13W43        

plage

S2299 2013.03.15       N18W37           plage
S2301 2013.03.17       S13W53           plage
11703 2013.03.19
2013.03.22
5 1 1 S26W84 0040 CAO HRX area: 0015
11702 2013.03.20
2013.03.21
9 8 4 N07W64 0060 CAO DAO area: 0050

location: N08W67

S2309 2013.03.21       N00W36           plage
S2310 2013.03.22   2   S22E13 0003   AXX  
S2311 2013.03.22       S10W21         plage
11704 2013.03.23 1 3 1 N16E60 0080 HAX HSX  
S2312 2013.03.23       N30W25         plage
S2313 2013.03.24   6 2 S12E33 0025   CRO    
Total spot count: 15 20 8  
Sunspot number: 45 70 48  (total spot count + 10 * number of spotted regions)
Weighted SN: 30 36 24  (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): 27 25 26 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 61.4 (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
2013.03 114.5 (1) 68.0 (2A) / 87.8 (2B) / 50.6 (2C) (51.5 projected, -1.0) (9.54)

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.