Solar Terrestrial Activity Report

Last major update issued on September 14, 2011 at 05:10 UTC. Minor update added at 20:10 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 12, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2112 [July 2011] -  2113 [July-August 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on September 13. Solar wind speed ranged between 492 and 585 km/s under the decreasing influence of a high speed stream from CH475.

Solar flux measured at 20h UTC on 2.8 GHz was 129.4 (increasing 31.9 over the last solar rotation). The planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 16.8). Three hour interval K indices: 44432113 (planetary), 44432222 (Boulder).

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

At midnight UTC the visible solar disk had 14 spotted regions (in 2K resolution SDO images).

Region 11287 developed slowly and was quiet.
Region 11289 was mostly quiet and unchanged. The region was the source of the most significant event of the day, a C2.9 long duration event peaking at 23:36 UTC. This event was associated with a bright CME (in STEREO-B) which appears to be partly Earth directed.
Region 11290 decayed slowly and quietly.
Region 11292 decayed slolwy and was quiet.
Region 11293 decayed slowly and quietly.
Region 11294 developed slowly and was quiet.
Region 11295 was mostly quiet but could produce minor M class events.
New region 11296 rotated into view at the northeast limb on September 12 and was numbered the next day by SWPC.

Spotted regions not numbered by NOAA/SWPC:
[S1196] rotated partly out of view at the southwest limb. Location at midnight: S19W83
[S1203] emerged in the northeast quadrant on September 10, became spotless quickly, then reemerged with tiny spots on September 12. Location at midnight: N07E27
[S1213] emerged in the southern hemisphere near the central meridian on September 13. Location at midnight: S18W01
[S1214] emerged in the southeast quadrant on September 13. Location at midnight: S26E04
[S1215] emerged in the southwest quadrant on September 13. Location at midnight: S17W37
[S1216] emerged in the northwest quadrant on September 13. Location at midnight: N22W56

Minor update posted at 20:10 UTC: Region 11297 (formerly S1215) has developed very quickly today and could produce M class flares. Region 11295 has developed significantly as well and could produce an M class flare. Solar flux at 17h UTC was above 140. The latest high resolution CHARMAP.

The CME observed early today after an eruption late on September 13, was a full halo CME based on LASCO images.

Coronal mass ejections (CMEs)

September 11-12: No obviously Earth directed CMEs observed.
September 13: A bright CME was observed following an eruption in region 11289 late in the day. This CME could reach Earth on September 16.

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

No obvious coronal holes are currently in or near potentially geoeffective positions.

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

Forecast

The geomagnetic field is expected to be quiet to unsettled on September 14 and quiet on September 15 and most of September 16. During the latter half of September 16 there's a chance of a CME impact which could cause unsettled to active 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
11287 2011.09.02
2011.09.03
3 6 S27W68 0080 DSO DSO location: S28W65

area: 0110

11288 2011.09.03
2011.09.04
    N19W78           plage
S1196 2011.09.04   1 S19W83 0000   AXX  
11289 2011.09.05
2011.09.06
10 20 N23W08 0350 CKO CHO

location: N23W12

area: 0450

11290 2011.09.07
2011.09.09
8 11 S14W25 0070 DAO CRO

location: S13W24

11291 2011.09.09
2011.09.10
    N23W43         plage
11294 2011.09.10
2011.09.12
5 16 S18E13 0020 CSO CAO location: S17E13

area: 0040

S1202 2011.09.10     N11W42           plage
S1203 2011.09.10   3 N07E27 0000   BXO  
11292 2011.09.11 5 7 N09E38 0050 CAO CSO  
11295 2011.09.11
2011.09.12
2 22 N21E58 0030 CSO CAI location: N21E60

area: 0100

S1206 2011.09.11     N15W13           plage
11293 2011.09.11
2011.09.12
3 7 N17W25 0010 BXO BXO  
11296 2011.09.12
2011.09.13
2 9 N27E70 0050 DSO DSO formerly region S1210

area: 0080

S1211 2011.09.12     S33W25         plage
S1212 2011.09.12     N38E05         plage
S1213 2011.09.13   3 S18W01 0010   BXO    
S1214 2011.09.13   2 S26E04 0000   BXO    
S1215 2011.09.13   7 S17W37 0030   CRO    
S1216 2011.09.13   1 N22W56 0000   AXX    
Total spot count: 38 114  
Sunspot number: 118 254  (total spot count + 10 * number of spotted regions)
Classification adjusted SN: 78 160  (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): 71 84  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
2010.06 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
2011.09 116.9 (1) 40.9 (2A) /  94.5 (2B) (56.7 predicted, +2.3) (13.10)

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.