Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 5, 2012 at 04:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-24 (last update August 6, 2012)] [Cycle 24 progress (last update September 2, 2012) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update August 6, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update August 6, 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 August 5, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to minor storm on September 4. Solar wind speed at SOHO ranged between 302 and 479 km/s (incomplete data). A sudden change in Bz (interplanetary magnetic field)and a minor increase in solar wind speed just after 22h UTC was likely the arrival of the CME observed early on September 2. There's a chance that the disturbance is partially caused by a high speed stream from CH532 as well. The geomagnetic field has been active to major storm since the arrival of this disturbance.

Solar flux measured at 20h UTC on 2.8 GHz was 137.6 (increasing 4.3 over the last solar rotation). The Potsdam WDC planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 17.1). Three hour interval K indices: 33532224 (planetary), 33522323 (Boulder).

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

At midnight UTC the visible solar disk had 9 spotted active regions (in 2K resolution SDO images).

Region 11558 [N15W31] decayed slowly and quietly.
Region 11560 [N03W45] decayed slowly with a reduction in penumbral area and a loss of spots. There's a weak magnetic delta structure in a central penumbra and a minor M class flare is possible.
Region 11561 [S11W53] decayed slowly and quietly.
Region 11563 [S27E02] decayed slowly and quietly.
Region 11564 [S13E15] decayed significantly losing penumbral area. There are many small spots and still some polarity intermixing.
Region 11565 [N11E09] decayed slowly and quietly.
Region 11566 [N22E66] was quiet and stable

Spotted regions not numbered by NOAA/SWPC:
S1895 [S08E01] reemerged with tiny spots.
S1897
[S22W21] developed slowly and quietly

Coronal mass ejections (CMEs)

September 3-4: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
September 2
: A full faint halo CME was observed early in the day and could reach Earth on September 5.

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 small northern hemisphere coronal hole (CH532) was in an Earth facing position on September 2-3, CH532 appears closed during the latter half of September 3.

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 very poor. Propagation on long distance northeast-southwest paths is good.

Forecast

The geomagnetic field is expected to be unsettled to major storm on September 5 due to CME and coronal hole effects. Quiet to unsettled is likely on September 6-7.

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
11555 2012.08.24
2012.08.25
      N08W68           plage
11557 2012.08.27       N17W74           plage
11558 2012.08.27   9 4 N13W37 0010   BXO location: N15W31
S1882 2012.08.27       N23W46           plage
11559 2012.08.27
2012.08.28
7     N15W30 0050 DSO       originally AR 11558
S1884 2012.08.27       N15W48           plage
11560 2012.08.29 15 34 14 N04W47 0170 EAI EAC beta-gamma-delta
11561 2012.08.29
2012.08.30
2 3 2 S10W54 0010 AXX BXO  
11562 2012.08.29
2012.08.30
6     S20W22 0050 DSO     location: S18W16

SWPC has added S1897 to this region

S1890 2012.08.29       S18W31           plage
11563 2012.08.30 5 8 3 S24E03 0010 BXO BXO location: S27E02
11564 2012.08.30
2012.08.31
29 63 28 S14E14 0160 ESI DAI  
S1894 2012.09.01       S02W23           plage
S1895 2012.09.02   2   S08E01           plage
11565 2012.09.02
2012.09.03
5 8 4 N10E07 0080 DSO CSO area: 0100
S1897 2012.09.02   11 6 S22W21 0050   DRO  
11566 2012.09.03 1 1 1 N22E64 0060 HAX HSX location: N22E79
S1898 2012.09.03       N09E13         plage
S1899 2012.09.03       N10W43         plage
Total spot count: 70 139 62  
Sunspot number: 150 229 142  (total spot count + 10 * number of spotted regions)
Weighted SN: 95 162 85  (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): 90 80 78 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
2012.09 141.8 (1)  17.8 (2A)/ 133.5 (2B) (70.0 projected, +2.8) (19.16)

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.