Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 2, 2013 at 04:15 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 March 2, 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 Spril 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 April 1. Solar wind speed at SOHO ranged between 348 and 447 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 119.1 (increasing 0.7 over the last solar rotation). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.8). Three hour interval K indices: 12221102 (planetary), 12221212 (Boulder).

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

At midnight UTC the visible solar disk had 14 spotted active regions (in 2K resolution SDO images).

Region 11704 [N15W46] was quiet and stable.
Region 11705 [S12W75] reemerged with a penumbra spot.
Region 11707 [S11W28] decayed slowly and quietly.
Region 11708 [N11E17] was quiet and stable.
Region 11710 [S21E08] decayed slowly and quietly.
Region 11711 [S18E51] was quiet. C and M class flares are possible.
Region 11712 [N02E24] was quiet and stable.

Spotted regions not numbered by SWPC:
S2314 [S19W07] developed slowly and quietly.
New region S2328 [S19E81] rotated into view.
New region S2329 [N12E80] rotated into view.
New region S2330 [N24E60] emerged with a penumbra spot in an old plage area.
New region S2331 [N08E37] emerged quickly with many spots.
New region S2332 [S15E08] emerged with penumbra spots.
New region S2333 [S17W31] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

March 30 - April 1: 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

No obvious coronal holes are currently in or near potentially geoeffective positions.

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

Forecast

The geomagnetic field is expected to be quiet on April 2-4.

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 4 5 3 N14W47 0080 DAO CAO  
11705 2013.03.24
2013.03.25
  1   S12W80 0002   AXX    
S2314 2013.03.25   3 2 S19W07 0011   BXO  
11706 2013.03.26
2013.03.27
      S07W67           plage
11709 2013.03.26
2013.03.29
      S33W63           plage
11708 2013.03.27
2013.03.28
2 9 3 N11E17 0040 HAX CAO  
11707 2013.03.28 4 9 4 S10W28 0030 CRO CRO  
11710 2013.03.28
2013.03.29
7 9 2 S22E07 0010 BXO BXO  
S2321 2013.03.28       S15E13           plage
S2322 2013.03.28       S14W36           plage
11711 2013.03.29
2013.03.30
6 17 5 S20E52 0480 CKI CKO location: S18E51

area: 0600

11712 2013.03.30
2013.03.31
1 2 1 N02E23 0010 AXX BXO  
S2328 2013.04.01   1   S19E81 0003   AXX    
S2329 2013.04.01   1 1 N12E80 0050   HSX    
S2330 2013.04.01   1   N24E60 0002   AXX    
S2331 2013.04.01   15 8 N08E37 0040   DRI    
S2332 2013.04.01   2 1 S15E08 0005   BXO    
S2333 2013.04.01   1 1 S17W31 0004   AXX    
Total spot count: 24 76 31  
Sunspot number: 84 216 141  (total spot count + 10 * number of spotted regions)
Weighted SN: 47 107 62  (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 76 78 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) 9.86
2013.04 119.1 (1) 2.8 (2A) / 84.0 (2B) / 52.0 (2C) (51.0 projected, -1.2) (4.8)

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.