Solar Terrestrial Activity Report

Activity chart

Last major update issued on October 4, 2012 at 03:35 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-24 (last update October 3, 2012)] [Cycle 24 progress (last update October 1, 2012) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update October 3, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update October 3, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update October 1, 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 October 3. Solar wind speed at SOHO ranged between 276 and 352 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 111.7 (decreasing 16.3 over the last solar rotation). The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.5). Three hour interval K indices: 32211011 (planetary), 32211310 (Boulder).

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

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

Region 11579 [S10W46] developed slowly and quietly.
Region 11580 [N17W40] decayed slowly and quietly.
Region 11582 [S12W24] was quiet and stable.
Region 11584 [S23W11] decayed slowly and quietly.
Region 11585 [S18E54] developed significantly and could produce C and minor M class flares.

Spotted regions not numbered by NOAA/SWPC:
S1936 [N06W83] reemerged with a single spot.
S1956
[S20E03] reemerged with tiny spots.

Coronal mass ejections (CMEs)

October 1-3: 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 recurrent coronal hole (CH538) in the southern hemisphere will rotate into an Earth facing position on October 5-6.

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

Forecast

The geomagnetic field is expected to be mostly quiet on October 4-7. On October 8-9 a high speed stream from CH538 could cause quiet to active conditions.

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
11579 2012.09.23
2012.09.24
4 15 7 S10W47 0180 CSO DHO area: 0280
S1936 2012.09.23   1 1 N06W83 0010   AXX    
S1937 2012.09.24       S22W49           plage
11580 2012.09.24
2012.09.25
  1   N19W42 0000   AXX  
11582 2012.09.25
2012.09.26
5 9 5 S08W25 0270 CHO CHO area: 0420

location: S12W24

S1943 2012.09.26       N14W58           plage
S1951 2012.09.29       S19W55           plage
11584 2012.09.30 2 6 3 S23W12 0020 HAX CRO  
S1953 2012.09.30       N12W53           plage
11585 2012.10.01
2012.10.02
7 14 6 S17E52 0240 DSO DKI location: S18E54
S1955 2012.10.01       S08W13         plage
S1956 2012.10.01   3   S10E03 0000   BXO    
S1957 2012.10.01       N04W55         plage
S1958 2012.10.01       N05W11         plage
S1959 2012.10.02       N09E06         plage
S1960 2012.10.02       N37W16         plage
Total spot count: 18 49 22  
Sunspot number: 58 119 72  (total spot count + 10 * number of spotted regions)
Weighted SN: 43 82 55  (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): 35 42 40 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)
2011.08 101.7 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)
possible solar max
8.81
2012.03 114.7 64.3 66.8 (-0.1) 16.08
2012.04 113.0 55.2 (64.7 projected, -2.1) 10.10
2012.05 121.5 69.0 (61.8 projected, -2.9) 7.06
2012.06 119.6 64.5 (59.9 projected, -1.9) 10.08
2012.07 133.9 66.5 (60.0 projected, +0.1) 13.90
2012.08 115.4 63.1 (62.0 projected, +2.0) 7.96
2012.09 122.9 61.5 (63.6 projected, +1.6) 8.64
2012.10 119.3 (1)  6.0 (2A) / 61.7 (2B) / 57.1 (2C) (63.5 projected, -0.1) (15.54)

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 30 day average.
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.