Solar Terrestrial Activity Report

Activity chart

Last major update issued on October 12, 2012 at 04:45 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 11. Solar wind speed at SOHO ranged between 442 and 552 km/s under the decreasing influence of a high speed stream from CH538. A high speed stream associated with CH539 became the dominant solar wind source near midnight and is currently causing unsettled to active conditions.

Solar flux measured at 20h UTC on 2.8 GHz was 116.6 (increasing 15.7 over the last solar rotation). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.3). Three hour interval K indices: 32122112 (planetary), 21113212 (Boulder).

The background x-ray flux is at the class B5 level.

At midnight UTC the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).

Region 11585 [S18W55] decayed slowly and was mostly quiet.
Region 11586 [S12E12] was quiet and stable.
Region 11589 [N13E50] has polarity intermixing and could produce minor M class events.
New region 11590 [S30E57] rotated into view on October 10 and was numbered by SWPC the next day. The region decayed on Oct.11 and was quiet.

Spotted regions not numbered by NOAA/SWPC:
New region S1976 [N07E85] rotated into view with a single spot.
New region S1977 [S15E34] emerged with a tiny spot.

Coronal mass ejections (CMEs)

October 9-11: 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) was in an Earth facing position on October 9-11. A coronal hole (CH540) in the northern hemisphere was Earth facing on October 11, however, CH540 nearly closed on Oct.11 due to emerging flux to the southwest of the coronal hole. 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 good.


The geomagnetic field is expected to be quiet to actice on October 12-15 due to a high speed stream from CH539. 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
8 7 5 S19W54 0100 CAO CAO area: 0060
S1961 2012.10.04       N22W54           plage
11588 2012.10.04
1     N09W87 0010 AXX     rotated out of view
11586 2012.10.06
1 4 2 S13E11 0080 HSX CSO  
S1965 2012.10.06       S23W31           plage
S1967 2012.10.08       N14W01           plage
S1968 2012.10.08       N51W35           plage
11589 2012.10.09 20 45 20 N12E49 0280 DAC DAC beta-gamma
S1972 2012.10.09       N27W54           plage
11590 2012.10.10
2 1 1 S29E59 0030 CSO HRX location: S30E57
S1974 2012.10.10       S09W17         plage
S1975 2012.10.10       N32W73         reversed polarities
S1976 2012.10.11   1 1 N07E85 0180   HSX    
S1977 2012.10.11   1   S15E34 0000   AXX    
Total spot count: 32 59 29  
Sunspot number: 82 119 79  (total spot count + 10 * number of spotted regions)
Weighted SN: 52 82 52  (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): 49 42 43 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
2012.10 109.9 (1) 20.3 (2A) / 57.2 (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.