Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 24, 2012 at 05:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-24 (last update September 8, 2012)] [Cycle 24 progress (last update September 2, 2012) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update September 8, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update September 8, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update September 3, 2012)]

[POES auroral activity level since October 2009 - updated September 8, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was inactive on September 23. Solar wind speed at SOHO ranged between 332 and 371 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 133.6 (increasing 22.1 over the last solar rotation). The Potsdam WDC planetary A index was 0 (STAR Ap - based on the mean of three hour interval ap indices: 0.3). Three hour interval K indices: 00000000 (planetary), 10001210 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight UTC the visible solar disk had 10 spotted active regions (in 2K resolution SDO images).

Region 11573 [N15W28] developed slowly and quietly.
Region 11575 [N08E09] was quiet. The region is being considered for a split into two groups.
Region 11576 [S21E15] added a spot with rudimentary penumbra in the far western part of the leading polarity area. The region could be split into two tomorrow.
Region 11577 [N09E31] developed further and could produce C and minor M class flares.

Spotted regions not numbered by NOAA/SWPC:
S1924 [S25W15] developed with a new leader spot forming.
S1927 [N21E27] was quiet and stable.
S1928 [N02W27] reemerged with a tiny spot.
S1934 [S17W03] was quiet and stable.
New region S1935 [S10E84] rotated partly into view with a large spot.
New region S1936 [N08E53] emerged with a tiny spot.

Bipolar flux emerged at N78W26, however, no spots were observed.

The single C class event of the day was a long duration C1.7 event peaking at 15:56 UTC and was associated with a large filament eruption (and CME) behind the east limb.

Coronal mass ejections (CMEs)

September 20-22: 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 Earth facing positions.

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

Forecast

The geomagnetic field is expected to be quiet on September 24-26.

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. 0.5k 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
11571 2012.09.10
2012.09.12
      S13W86           plage
11573 2012.09.15
2012.09.16
  8 4 N18W31 0010   CRO location: N15W28
11575 2012.09.17
2012.09.18
13 32 14 N08E11 260 EHO EHO

area: 0380

S1924 2012.09.17   7 1 S25W15 0010   BXO  
S1925 2012.09.17       S12W38           plage
11576 2012.09.18
2012.09.19
2 16 4 S22E17 0050 DSO FSO  
S1927 2012.09.19   3   N21E27 0000   BXO  
S1928 2012.09.20   1   N02W27 0000   AXX    
S1929 2012.09.21       N06E39         plage
S1930 2012.09.21       S16W31         plage
S1931 2012.09.21       N22W48           plage
11577 2012.09.22 12 27 14 N08E30 0100 DAI DAI  
S1932 2012.09.22       N02W37         plage
S1933 2012.09.22       N18E11         plage
S1934 2012.09.22   2 1 S17W03 0000   BXO  
S1935 2012.09.23   1 1 S10E84 0320   HHX    
S1936 2012.09.23   1   N08E53 0000   AXX    
Total spot count: 27 98 39  
Sunspot number: 57 198 109  (total spot count + 10 * number of spotted regions)
Weighted SN: 47 131 72  (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): 34 69 60 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)
2011.05 95.8 41.5 47.6 (+5.8) 8.94
2011.06 95.8 37.0 53.2 (+5.6) 8.06
2011.07 94.2 43.8 57.2 (+4.0) 8.16
2011.08 101.7 50.6 59.0 (+1.8) 7.26
2011.09 133.8 78.0 59.5 (+0.5) 12.27
2011.10 137.3 88.0 59.9 (+0.4) 8.28
2011.11 153.5 96.7 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) 8.81
2012.03 114.7 64.3 (67.3 projected, +0.4) 16.08
2012.04 113.0 55.2 (66.5 projected, -0.8) 10.10
2012.05 121.5 69.0 (64.4 projected, -2.1) 7.06
2012.06 119.6 64.5 (63.6 projected, -0.8) 10.08
2012.07 133.9 66.5 (64.6 projected, +1.0) 13.90
2012.08 115.4 63.1 (67.2 projected, +2.6) 7.96
2012.09 118.6 (1)  61.9 (2A) / 80.8 (2B) / 58.0 (2C) (70.0 projected, +2.8) (9.80)

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. 2C) STAR SDO 1K Wolf number month to date.
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.