Solar Terrestrial Activity Report

Activity chart

Last major update issued on October 11, 2012 at 03:45 UTC.

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

[POES auroral activity level since October 2009 - updated October 7, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on October 10. Solar wind speed at SOHO ranged between 454 and 610 km/s under the influence of a high speed stream from CH538.

Solar flux measured at 20h UTC on 2.8 GHz was 112.0 (increasing 12.9 over the last solar rotation). The Potsdam WDC planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.3). Three hour interval K indices: 33332332 (planetary), 32323332 (Boulder).

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

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

Region 11585 [S18W41] decayed losing penumbral area.
Region 11586 [S12E26] decayed slightly and was quiet.
Region 11588 [N08W74] decayed slowly and quietly.
Region 11589 [N13E63] contributed to the M1.0 event peaking at 05:04 UTC and was otherwise mostly quiet.

Spotted regions not numbered by NOAA/SWPC:
S1971 [N13W70] decayed slowly and quietly.
New region S1973 [S30E73] rotated into view with small spots. It is uncertain if this is the region that has been quite active over the last days or if there is another trailing spot group. The largest event of the day was recorded as an M1.0 flare peaking at 05:04 UTC. This event was caused by near simultaneous flares in this region and AR 11589.
New region S1974 [S09W04] emerged near CH539 with a single tiny spot.
New region S1975 [N32W60] emerged with reversed polarities.

Coronal mass ejections (CMEs)

October 8-10: 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 southern hemisphere coronal hole (CH539) will rotate into an Earth facing position on October 9-11. A coronal hole (CH540) in the northern hemisphere will likely rotate into an Earth facing position on October 11. Another northern hemisphere coronal hole (CH541) could become Earth facing on October 13.

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.


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.


The geomagnetic field is expected to be mostly quiet on October 11. A high speed stream from CH539 could cause some unsettled and active intervals on October 12-15 with contribution from CH540 on October 14-15. A high speed stream from CH541 could produce a few unsettled and active intervals on October 16-17.

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
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlay
2K 1K
11585 2012.10.01
4 15 9 S19W41 0120 DAO DAO  
S1961 2012.10.04       N22W41           plage
11588 2012.10.04
3 4 1 N08W73 0010 BXO BXO  
S1963 2012.10.05       S08W50           plage
11586 2012.10.06
1 3 2 S12E24 0060 HSX HSX area: 0100
S1965 2012.10.06       S23W18           plage
S1967 2012.10.08       N14E12           plage
S1968 2012.10.08       N51W22           plage
S1969 2012.10.08       N12W75          
11587 2012.10.08
1     S09W92 0010 AXX     rotated out of view
11589 2012.10.09 12 19 14 N13E61 0200 DAI DAC beta-gamma

area: 0350

S1971 2012.10.09   2   N13W70 0000   AXX  
S1972 2012.10.09       N27W41         plage
S1973 2012.10.10   3 1 S30E73 0020   CRO    
S1974 2012.10.10   1 1 S09W04 0000   AXX    
S1975 2012.10.10   1   N32W60 0000   AXX   reversed polarities
Total spot count: 21 48 28  
Sunspot number: 71 128 88  (total spot count + 10 * number of spotted regions)
Weighted SN: 36 66 46  (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): 43 45 48 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
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)
possible cycle 24 max
2012.03 114.7 64.3 66.8 (-0.1) 16.08
2012.04 113.0 55.2 (64.7 projected, -2.1) 10.10
2012.05 121.5 69.0 (61.8 projected, -2.9) 7.06
2012.06 119.6 64.5 (59.9 projected, -1.9) 10.08
2012.07 133.9 66.5 (60.0 projected, +0.1) 13.90
2012.08 115.4 63.1 (62.0 projected, +2.0) 7.96
2012.09 122.9 61.5 (63.6 projected, +1.6) 8.07
2012.10 109.2 (1) 17.6 (2A) / 54.7 (2B) / 52.4 (2C) (63.5 projected, -0.1) (17.18)

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.