Solar Terrestrial Activity Report

Activity chart

Last major update issued on October 6, 2012 at 05:45 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 September 8, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on October 5. Solar wind speed at SOHO ranged between 284 and 331 km/s. After 14h UTC a weak low speed stream, probably from CH537, was the dominant solar wind source.

Solar flux measured at 20h UTC on 2.8 GHz was 106.2 (decreasing 22.4 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.5). Three hour interval K indices: 00111213 (planetary), 00012312 (Boulder).

The background x-ray flux is at the class B2 level.

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

Region 11579 [S11W74] decayed slowly and quietly.
Region 11582 [S12W50] was quiet and stable.
Region 11584 [S23W39] decayed slowly and quietly.
Region 11585 [S18E25] decayed slowly and quietly.

Spotted regions not numbered by NOAA/SWPC:
S1962 [N09W03] was quiet and stable.
New region S1963 [S08E16] emerged with a tiny spot.

Coronal mass ejections (CMEs)

October 3-4: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
October 5: A very long duration B7.8 event peaked at 07:30 UTC and was associated with a filament eruption near AR 11584. A partial halo CME was observed in LASCO images and STEREO imagery indicate that parts of the CME are Earth directed.

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 coronal hole (CH538) in the southern hemisphere was in an Earth facing position on October 5. Another recurrent southern hemisphere coronal hole (CH539) will likely rotate into an Earth facing position on October 9-10.

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 poor to fair.


The geomagnetic field is expected to be quiet to unsettled on October 6 due to weak effects from CH537 and quiet on October 7. On October 8-9 a high speed stream from CH538 could cause quiet to active conditions. The CME observed on October 5 could reach Earth on October 8 and contribute to the disturbance from CH538.

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
11579 2012.09.23
2 3 2 S10W73 0150 CSO HHX area: 0300
11580 2012.09.24
      N19W69           plage
11582 2012.09.25
1 1 1 S12W51 0230 HSX HHX area: 0420
11584 2012.09.30 2 2 1 S22W40 0000 AXX AXX  
11585 2012.10.01
10 14 7 S19E26 0180 DAO DSO area: 0250
S1955 2012.10.01       S08W39           plage
S1956 2012.10.01       S10W23           plage
S1958 2012.10.01       N05W37           plage
S1959 2012.10.02       N09W20           plage
S1960 2012.10.02       N37W42           plage
S1961 2012.10.04       N22E24         plage
S1962 2012.10.04   3   N09W03 0000   BXO  
S1963 2012.10.05   1   S08E16 0000   AXX    
Total spot count: 15 24 11  
Sunspot number: 55 84 51  (total spot count + 10 * number of spotted regions)
Weighted SN: 30 49 36  (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): 33 29 28 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 sunspot 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) 8.64
2012.10 114.7 (1) 9.5 (2A) / 59.2 (2B) / 54.0 (2C) (63.5 projected, -0.1) (10.58)

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 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.