Solar Terrestrial Activity Report

Last major update issued on October 25, 2011 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 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update October 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update October 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update October 1, 2011)]

[POES auroral activity level since October 2009 - updated October 24, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2113 [July-August 2011] - 2114 [August-September 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to severe storm on October 24. Solar wind speed ranged between 322 and 563 km/s. A strong solar wind shock was observed at SOHO at 17:50 UTC, the arrival of the CME observed after a filament eruption in the northwest quadrant on October 22.

Solar flux measured at 20h UTC on 2.8 GHz was 145.3 (increasing 6.3 over the last solar rotation). The planetary A index was 23 (STAR Ap - based on the mean of three hour interval ap indices: 23.3). Three hour interval K indices: 20200157 (planetary), 20211246 (Boulder).

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

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

Region 11324 [N12W11] decayed quickly losing all mature penumbra on both polarities.
Region 11325 [N15E15] was quiet and stable.
Region 11327 [S22W39] decayed slowly and quietly.
Region 11328 [N17W27] was quiet and stable.
Region 11330 [N07E45] was quiet and has M class flaring potential.
Region 11331 [N08W75] developed slowly and quietly.
New region 11332 [N31E75] rotated into view late on October 23 and was numbered by SWPC the next day.

Spotted regions not reported by NOAA/SWPC:
[S1292] emerged just north of region 11330 on October 23. Location at midnight: N15E54

Coronal mass ejections (CMEs)

October 23-24: No obviously Earth directed CMEs observed.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A coronal hole (CH481)  in the southern hemisphere could rotate into an Earth facing position on October 25-26.

The above coronal hole map is based on a new method where coronal holes are detected automatically. The method may need some fine tuning, however, 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 the new method, the extent and intensity of both holes 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 very poor. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be unsettled to severe storm on October 25 due to CME effects and quiet to unsettled on October 26-27. A high speed stream from CH481 could cause quiet to active conditions on October 28-29.

Coronal holes (1) Coronal mass ejections (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

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 polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
11321 2011.10.14
2011.10.15
    S16W76           plage
11323 2011.10.16
2011.10.17
    N25W39          

plage

11324 2011.10.17 31 34 N12W13 0140 EAI DRI area: 0040
11327 2011.10.17
2011.10.20
5 11 S20W41 0200 DSO CAO location: S22W39
S1280 2011.10.17     S15W51           plage
11325 2011.10.19 11 25 N16E16 0150 DSO CSO

 

11328 2011.10.20   2 N17W34 0000   AXX location: N17W27
11329 2011.10.20
2011.10.21
    S29W83         plage
S1283 2011.10.20     S06W37           plage
11330 2011.10.21
2011.10.22
13 24 N08E45 0560 EKO EHO

area: 0750

S1287 2011.10.21     N02W47           plage
S1288 2011.10.22     S15W18           plage
S1289 2011.10.22     N20W09           plage
S1290 2011.10.22     N17W21           plage
11331 2011.10.22
2011.10.23
4 7 N09W73 0030 CSO DRO location: N08W75
S1292 2011.10.23   1 N15E54 0000   AXX  
11332 2011.10.23
2011.10.24
1 1 N32E77 0030 HSX HSX area: 0060

location: N31E75

S1294 2011.10.23     N27E10         plage
Total spot count: 65 105  
Sunspot number: 125 185  (total spot count + 10 * number of spotted regions)
Classification adjusted SN: 100 136  (Sum of total spot count + classification adjustment for each AR. Classification adjustment: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 75 61  k * (sunspot number). k = 0.6 for SWPC. k = 0.33 for STAR SDO

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
(3)
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
3.25
2010.07 79.8 16.1 16.7 (+0.3) 6.31 / 5.15
2010.08 79.2 19.6 17.4 (+0.7) 8.49 / 7.77
2010.09 81.1 25.2 19.6 (+2.2) 5.33 / 5.45
2010.10 81.6 23.5 23.2 (+3.6) 6.07 / 6.27
2010.11 82.5 21.5 26.5 (+3.3) 4.80 / 5.50
2010.12 84.2 14.4 28.8 (+2.3) 3.41 / 4.35
2011.01 83.6 19.1 31.0 (+2.2) 4.32 / 5.51
2011.02 94.6 29.4 33.4 (+2.4) 5.41 / 6.44
2011.03 115.0 56.2 36.9 (+3.5) 7.79 / 8.18
2011.04 112.6 54.4 (41.1 predicted, +4.2) 9.71 / 8.83
2011.05 95.8 41.6 (45.2 predicted, +4.1) 9.18 / 8.94
2011.06 95.8 37.0 (49.2 predicted, +4.0) 8.96
2011.07 94.2 43.9 (53.1 predicted, +3.9) 9.14
2011.08 101.7 50.6 (57.2 predicted, +4.1) 8.16
2011.09 133.8 78.0 (60.3 predicted, +3.1) 12.80
2011.10 138.8 (1) 96.2 (2A) / 124.3 (2B) (61.8 predicted, +1.5) (7.31)

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.
3) Running average based on the preliminary daily SWPC ap indices. Values in red are based on the official NGDC 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.