Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 28, 2012 at 05:05 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-24 (last update September 8, 2012)] [Cycle 24 progress (last update September 2, 2012) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update September 8, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update September 8, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update September 3, 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 on September 27. Solar wind speed at SOHO ranged between 360 and 441 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 133.2 (increasing 2.7 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: 3.5). Three hour interval K indices: 22110011 (planetary), 22112211 (Boulder).

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

At midnight UTC the visible solar disk had 15 spotted active regions (in 2K resolution SDO images).

Region 11575 [N07W45] decayed slowly and quietly.
Region 11576 [S21W32] decayed slowly and quietly.
Region 11577 [N08W27] was quiet and stable.
Region 11579 [S10E33] was quiet and stable.
Region 11580 [N16E43] decayed slowly and quietly.
Region 11581 [N21W22] decayed slowly and quietly.
Region 11582 [S12E57] was quiet and stable.

Spotted regions not numbered by NOAA/SWPC:
S1929 [N08W11] was quiet and stable.
S1936 [N07W02] was quiet and stable.
S1943 [N16E24] lost the spot from the previous day and gained smaller spots further south and east.
S1944 [N17W38] decayed slowly and quietly.
New region S1946 [S12W02] emerged with a tiny spot.
New region S1947 [N12W47] emerged with several spots.
New region S1948 [N25W53] emerged with a few spots.
New region S1949 [S35W07] emerged with a tiny spot.

Two C class events were recorded during the day. A C4.4 flare peaked at 17:20 UTC from a location just south of AR 11579. A long duration C3.7 event peaked at 23:57 UTC and had its origin between ARs 11577, 11575 and 11581. This event was associated with a type II radio sweep, a CME and was the likely source of a small proton event.

Coronal mass ejections (CMEs)

September 25-27: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
September 28: A CME was observed in STEREO imagery early in the day following the long duration C3.7 event late on Sept.27. This CME could reach Earth on September 30.

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

No obvious coronal holes are currently in or near Earth facing positions.

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.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on September 28-29. The CME observed early on Sept.28 could reach Earth on Sept.30 and cause active to minor storm conditions with a chance of major storming.

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
detected
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
2K 1K
11573 2012.09.15
2012.09.16
      N16W83        

spotless

11575 2012.09.17
2012.09.18
4 12 4 N09W46 0130 HAX CAO

area: 0180

location: N07W45

11576 2012.09.18
2012.09.19
1 6 1 S20W35 0005 AXX HRX  
11581 2012.09.19
2012.09.25
2 3   N22W24 0005 AXX AXX

location: N21W22

S1929 2012.09.21   6 1 N08W11 0000   BXO  
11577 2012.09.22 3 11 3 N09W26 0015 CSO CRO  
S1933 2012.09.22       N18W41           plage
S1934 2012.09.22       S17W55           plage
11579 2012.09.23
2012.09.24
2 6 3 S10E33 0160 HSX CHO area: 0300
S1936 2012.09.23   3   N07W02 0000   AXX  
11578 2012.09.24 1     N21W31 0005 AXX     spotless
S1937 2012.09.24       S22E29         plage
11580 2012.09.24
2012.09.25
3 6 4 N17E40 0020 CSO  BXO location: N16E43
S1939 2012.09.24       N09W74         plage
S1940 2012.09.24       N28W18           plage
11582 2012.09.25
2012.09.26
1 1 1 S13E55 0260 HHX HHX area: 0440
S1943 2012.09.26   3 1 N16E24 0000   BXO  
S1944 2012.09.26   1 1 N17W38 0000   AXX  
S1946 2012.09.27   1 1 S12W02 0000   AXX    
S1947 2012.09.27   5 2 N12W47 0010   CRO    
S1948 2012.09.27   3 2 N25W53 0000   BXO    
S1949 2012.09.27   1   S35W07 0000   AXX    
Total spot count: 17 68 24  
Sunspot number: 97 218 144  (total spot count + 10 * number of spotted regions)
Weighted SN: 47 102 58  (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): 58 76 79 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
(3)
2011.05 95.8 41.5 47.6 (+5.8) 8.94
2011.06 95.8 37.0 53.2 (+5.6) 8.06
2011.07 94.2 43.8 57.2 (+4.0) 8.16
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) 8.81
2012.03 114.7 64.3 (67.3 projected, +0.4) 16.08
2012.04 113.0 55.2 (66.5 projected, -0.8) 10.10
2012.05 121.5 69.0 (64.4 projected, -2.1) 7.06
2012.06 119.6 64.5 (63.6 projected, -0.8) 10.08
2012.07 133.9 66.5 (64.6 projected, +1.0) 13.90
2012.08 115.4 63.1 (67.2 projected, +2.6) 7.96
2012.09 121.4 (1)  75.6 (2A) / 84.0 (2B) / 62.3 (2C) (70.0 projected, +2.8) (8.88)

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 month to date.
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.