Solar Terrestrial Activity Report

Last major update issued on September 6, 2011 at 04:10 UTC. Minor update posted at 18:40 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update September 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update September 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update September 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update September 1, 2011)]

[POES auroral activity level since October 2009 - updated September 5, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2112 [July 2011] -  2113 [July-August 2011] NEW
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on September 5. Solar wind speed ranged between 299 and 403 km/s under the influence of a low speed stream from CH474.

Solar flux measured at 20h UTC on 2.8 GHz was 118.7 (increasing 21.2 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.5). Three hour interval K indices: 20102222 (planetary), 10112322 (Boulder).

The background x-ray flux is at the class C1 level.

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

Region 11277 was quiet and stable and will rotate over the northwest limb today.
[Region 11280 produced several C flares and 2 M flares (M1.6 at 04:08, M1.2 at 07:52 UTC) from behind the northwest limb.
Region 11281 decayed further and was quiet.
Region 11282 was quiet and stable. The region will rotate out of view today.
Region 11283 developed slowly and was mostly quiet. There's a magnetic delta structure in a penumbra to the north of the largest penumbra. M flares are possible. The region produced a major M5.3/1B flare at 01:50 UTC on September 6. A moderate type II radio sweep was recorded. A CME was observed in STEREO images soon after the flare. The CME appears to be fast and could impact Earth late on September 7 or early on September 8. Proton fluxes are increasing.
Region 11287 was quiet and stable.
New region 11288 emerged in the northeast quadrant on September 3 and was numbered 2 days later by SWPC. The region decayed slowly on September 5.

Spotted regions not numbered by NOAA/SWPC:
[S1196] emerged in the southeast quadrant on September 4. Location at midnight: S19E19
[S1198] began to rotate into view at the northeast limb late on September 5. Location at midnight: N25E87

Minor update added at 18:40 UTC on September 6: The CME observed earlier today was a halo CME, however, most of the ejected material was observed over the northern limbs. The CME was slower than first estimated and could reach Earth late on September 8 causing unsettled to active conditions with a chance of minor storming. A larger CME was observed later in the morning from a source behind the northwest limb.

Coronal mass ejections (CMEs)

September 3-5: No obviously Earth directed CMEs were observed in LASCO or STEREO imagery.
September 6: The CME associated with the major M5 flare in region 11283 appears to be fast in initial images and could impact Earth late on September 7 or early on September 8.

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 recurrent trans equatorial coronal hole (CH475) will likely rotate into an Earth facing position on September 8.

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 on September 6 and most of September 7. Late on September 7 or early on September 8 the CME from the major flare early on September could reach Earth and cause active to major storm conditions.

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
11277 2011.08.24
2011.08.25
1 1 N18W80 0010 AXX AXX location: N18W78
11279 2011.08.25     N13W73          
11281 2011.08.27
2011.08.28
3 6 S18W39 0050 CSO CRO

location: S19W37

11283 2011.08.29
2011.08.30
29 49 N14W04 0220 EAI DAC

beta-gamma-delta

area: 0450

11282 2011.08.29
2011.08.30
1 2 N22W86 0070 HSX CSO location: N23W83
S1190 2011.08.30     S13W17           plage
11287 2011.09.02
2011.09.03
5 8 S31E38 0080 CSO CSO

location: S30E38

S1193 2011.09.02     N19W29           plage
S1194 2011.09.02     N22W36           plage
11288 2011.09.03 3 2 N18E34 0010 BXO AXX formerly region S1195
S1196 2011.09.04   2 S19E19 0000   AXX  
S1197 2011.09.04     N35W68         plage
S1198 2011.09.05   1 N25E87 0150   HSX    
Total spot count: 42 71  
Sunspot number: 102 151  (total spot count + 10 * number of spotted regions)
Classification adjusted SN: 62 94  (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 68  k * (sunspot number). k = 0.6 for SWPC. k = 0.45 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
2010.06 72.5 13.6 16.4 (+0.9) 8.17 / 6.85
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 (36.2 predicted, +2.8) 7.79 / 8.18
2011.04 112.6 54.4 (39.1 predicted, +2.9) 9.71 / 8.83
2011.05 95.8 41.6 (42.4 predicted, +3.3) 9.18 / 8.94
2011.06 95.8 37.0 (46.1 predicted, +3.7) 8.96
2011.07 94.2 43.9 (50.3 predicted, +4.2) 9.14
2011.08 101.7 50.6 (54.4 predicted, +4.1) 8.16
2011.09 116.6 (1) 19.2 (2A) /  115.4 (2B) (56.7 predicted, +2.3) (6.43)

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.