Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 10, 2013 at 04:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update April 1, 2013)] [Cycle 24 progress (last update April 7, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update April 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update April 4, 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 very quiet on April 9. Solar wind speed at SOHO ranged between 339 and 373 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 146.5 (increasing 23.6 over the last solar rotation). The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.0). Three hour interval K indices: 11010011 (planetary), 11122211 (Boulder).

The background x-ray flux was at the class B7 level.

At midnight UTC the visible solar disk had 12 spotted active regions (in 2K resolution SDO images).

Region 11711 [S17W54] decayed slowly and quietly.
Region 11713 [N08W76] was mostly quiet. C and minor M class flares are possible.
Region 11714 [N12W24] decayed slowly and quietly.
Region 11716 [S22W15] was quiet and stable.
Region 11717 [S11E13] decayed slowly and quietly.
Region 11718 [N20W06] developed significantly with a nearly continuous logitudinal penumbral coverage. While the region only produced small C flares, M class flares are possible.
Region 11719 [N09E27] was quiet and stable.

Spotted regions not numbered by SWPC:
S2330 [N21W32] was quiet and stable.
S2343
[N11W03] was quiet and stable.
New region S2345 [S19E48] emerged with several spots.
New region S2346 [S21E58] emerged with several spots.
New region S2347 [S19W35] emerged with penumbra spots.

Coronal mass ejections (CMEs)

April 7-9: 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 small coronal hole (CH564) in the northern hemisphere was in an Earth facing position on April 6.

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

Forecast

The geomagnetic field is expected to be quiet on April 10 with a chance of unsettled intervals if a stream from CH564 arrives. Quiet conditions are likely on April 11-12.

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
11711 2013.03.29
2013.03.30
2 3 2 S17W55 0350 HHX HHX

area: 0500

11716 2013.04.01
2013.04.05
  3 1 S20W23 0010   BXO location: S22W15
11714 2013.04.01
2013.04.02
3 2 2 N12W26 0060 CSO HSX  
S2330 2013.04.01   1 1 N21W32 0004   AXX  
11713 2013.04.01
2013.04.02
16 14 9 N09W74 0180 DAO DAC beta-gamma
11715 2013.04.02
2013.04.04
      N18W81           plage
S2336 2013.04.03       S10W40           plage
S2337 2013.04.04       S08E03           plage
11720 2013.04.04
2013.04.07
      N10W35         plage
S2339 2013.04.04       N10W70           plage
11717 2013.04.05 3 5 1 S11E11 0020 CSO BXO

area: 0012

location: S11E13

11718 2013.04.05 21 31 21 N21W06 0190 DAC DAC

area: 0600

11719 2013.04.05 11 26 20 N10E26 0160 DAI DSI beta-gamma

location: N09E27

 

S2341 2013.04.06       N03W01           plage
S2342 2013.04.06       N10W56           plage
S2343 2013.04.07   4 2 N11W03 0012   BXO  
S2344 2013.04.08       S05W33         plage
S2345 2013.04.09   8 4 S19E48 0033   CRO    
S2346 2013.04.09   6 2 S21E58 0045   DSO    
S2347 2013.04.09   6 2 S19W35 0014   BXO    
Total spot count: 56 109 67  
Sunspot number: 116 229 187  (total spot count + 10 * number of spotted regions)
Weighted SN: 91 147 105  (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): 70 80 103 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
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 58.1 (-0.0) 8.07
2012.10 123.3 53.3 (57.6 projected, -0.5) 9.97
2012.11 121.3 61.8 (56.9 projected, -0.7) 7.08
2012.12 108.6 40.8 (55.7 projected, -1.2) 3.44
2013.01 127.1 62.9 (54.3 projected, -1.4) 4.69
2013.02 104.3 38.0 (53.3 projected, -1.0) 6.11
2013.03 111.3 57.9 (52.2 projected, -1.1) 10.56
2013.04 132.4 (1) 36.7 (2A) / 122.2 (2B) / 58.6 (2C) (51.0 projected, -1.2) (3.28)

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.