Solar Terrestrial Activity Report

Last major update issued on October 24, 2011 at 04:20 UTC. Minor update posted at 19:05 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 12, 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 on October 23. Solar wind speed ranged between 270 and 345 km/s. A low speed stream associated with CH480 became the dominant solar wind factor late in the day.

Solar flux measured at 20h UTC on 2.8 GHz was 155.5 (increasing 7.3 over the last solar rotation). The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.1). Three hour interval K indices: 00011121 (planetary), 01111211 (Boulder).

The background x-ray flux is at the class B6 level.

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

Region 11324 [N12E01] has many small spots and some polarity intermixing. C flares are likely with a chance of a minor M class flare. Flare: C2.5 at 11:47 UTC
Region 11325 [N15E28] was quiet and stable.
Region 11326 [N15W76] decayed slowly and quietly.
Region 11327 [S21W27] lost spots and regained penumbra on the leader spots.
Region 11328 [N15W16] was quiet and stable.
Region 11330 [N08E57] was quiet and has M class flaring potential.
New region 11331 [N09W60] emerged in the northwest quadrant on October 22 and got an SWPC number the next day.

Spotted regions not reported by NOAA/SWPC:
[S1292] emerged just north of region 11330 on October 23. Location at midnight: N15E65
[S1293] rotated partly into view at the northeast limb on October 23. Location at midnight: N31E87
[S1294] emerged in the northeast quadrant on October 23. Location at midnight: N27E23

Minor update added at 19:05 UTC on October 24: A strong solar wind shock was observed at ACE near 17:50 UTC, the arrival of the CME observed early on October 22. Minor to severe geomagnetic storming is possible for the end of today and the first half of October 25.

Coronal mass ejections (CMEs)

October 21 and 23: No obviously Earth directed CMEs observed.
October 22: A full halo CME was observed after a large filament eruption in the northwest quadrant early in the day.

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 small coronal hole (CH480)  in the northern hemisphere was in an Earth facing position on October 19-20.

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

Forecast

The geomagnetic field is expected to be quiet to unsettled on October 24 due to weak coronal hole effects. On October 25 the CME observed on October 22 could arrive and cause unsettled to active conditions with a chance of minor storm intervals until October 26.

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
    S16W62           plage
11323 2011.10.16
2011.10.17
    N25W25        

plage

11324 2011.10.17 26 61 N12W00 0150 EAI FSI beta-gamma
11327 2011.10.17
2011.10.20
11 13 S21W29 0130 DAO DAO area: 0200
S1280 2011.10.17     S15W38           plage
11325 2011.10.19 8 21 N15E29 0180 DAO CAO

 

11326 2011.10.20   3 N16W76 0010   BXO  
11328 2011.10.20   5 N17W20 0000   AXX location: N15W16
11329 2011.10.20
2011.10.21
    S29W69         plage
S1283 2011.10.20     S06W24           plage
11330 2011.10.21
2011.10.22
5 14 N08E60 0210 EAO EHO location: N08E57

area: 0750

S1287 2011.10.21     N02W34           plage
S1288 2011.10.22     S15W05         plage
S1289 2011.10.22     N20E04         plage
S1290 2011.10.22     N17W08         plage
11331 2011.10.22
2011.10.23
2 3 N11W60 0010 BXO CRO  
S1292 2011.10.23   1 N15E65 0000   AXX    
S1293 2011.10.23   1 N31E87 0080   HSX    
S1294 2011.10.23   1 N27E23 0000   AXX    
Total spot count: 52 123  
Sunspot number: 102 223  (total spot count + 10 * number of spotted regions)
Classification adjusted SN: 72 156  (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): 61 74  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
2011.10 138.5 (1) 92.2 (2A) / 124.2 (2B) (61.8 predicted, +1.5) (6.62)

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.