Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 8, 2012 at 06:15 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 to unsettled on September 7. Solar wind speed at SOHO ranged between 345 and 396 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 133.4 (increasing 13.7 over the last solar rotation). The Potsdam WDC planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 11.6). Three hour interval K indices: 23322233 (planetary), 13322223 (Boulder).

The background x-ray flux is at the class B7 level.

At midnight UTC the visible solar disk had 7 spotted active regions (in 2K resolution SDO images).

Region 11563 [S27W35] was quiet and stable.
Region 11564 [S13W26] decayed slowly and was mostly quiet.
Region 11565 [N10W30] was quiet and stable.
Region 11566 [N22E27] was quiet and stable.
New region 11567 [N16E55] emerged with several spots.

Spotted regions not numbered by NOAA/SWPC:
S1897 [S21W63] developed further and could produce a minor M class flare.
New region S1903 [N05E06] emerged with tiny spots.

Coronal mass ejections (CMEs)

September 5-7: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

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

A northern hemisphere coronal hole (CH533) could rotate into an Earth facing position on September 8-9 while a small coronal hole (CH534) in the southern hemisphere will be Earth facing on September 9. CH533 may be too far to the north to become geoeffective.

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

Forecast

The geomagnetic field is expected to be quiet to unsettled on September 8. Quiet conditions are likely on September 9-11. Weak coronal hole effects could cause some unsettled intervals on September 12-13.

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
11558 2012.08.27       N13W79          
11559 2012.08.27
2012.08.28
      N13W69           originally AR 11558
11560 2012.08.29 2     N05W89 0010 BXO     rotated out of view
11562 2012.08.29
2012.08.30
6     S20W63 0340 DHO     location: S19W51

SWPC thinks S1897 is part of this region

11563 2012.08.30   2   S24W37       location: S27W35
11564 2012.08.30
2012.08.31
35 63 24 S13W28 0200 ESI ESI  
S1895 2012.09.02       S08W37           plage
11565 2012.09.02
2012.09.03
3 6 2 N11W32 0010 AXX BXO  
S1897 2012.09.02   14 9 S21W63 0500   DKI  
11566 2012.09.03 2 7 3 N23E26 0070 CAO CSO

area: 0130

S1898 2012.09.03       N09W26           plage
S1900 2012.09.05       N37E09         plage
S1901 2012.09.06       N28W27         plage
S1902 2012.09.06       N14W65         plage
11567 2012.09.07 2 9 3 N17E56 0010 BXO DRO    
S1903 2012.09.07   2   N05E06 0000   BXO    
Total spot count: 50 103 41  
Sunspot number: 110 173 91  (total spot count + 10 * number of spotted regions)
Weighted SN: 70 126 64  (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): 66 61 50 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) 7.53
2012.09 137.3 (1)  28.7 (2A)/ 123.0 (2B) (70.0 projected, +2.8) (19.18)

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 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.