Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 5, 2013 at 04:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update September 1, 2013)] [Cycle 24 progress (last update September 1, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update September 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update September 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update August 4, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated September 5, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet on September 4. Solar wind speed at SOHO ranged between 409 and 457 km/s under the influence of weak effects from CH583.

Solar flux measured at 20h UTC on 2.8 GHz was 109.2 (increasing 4.8 over the last solar rotation). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.6). Three hour interval K indices: 20121012 (planetary), 21222222 (Boulder).

The background x-ray flux was at the class B4 level.

At midnight UTC the visible solar disk had 5 spotted active regions (in 2K resolution SDO images).

Region 11834 [N12W78] decayed slowly and quietly.
Region 11835 [S10W66] decayed slowly and quietly.
Region 11836 [N12W37] became more unstable during the latter half of the day due to increasing polarity intermixing.
Region 11837 [S17W47] produced a number of low level C flares during the first half of the day, then became quiet again.

Spotted regions not numbered by SWPC:
New region S2657 [S04E84] rotated into view.

Coronal mass ejections (CMEs)

September 2-4: 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 small coronal hole currently in the northeast quadrant could be numbered today.

Coronal hole map

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 to fair.

Forecast

The geomagnetic field is expected to be quiet on September 5-7.

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 2K resolution) 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 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
11834 2013.08.23
2013.08.24
5 6 2 N12W79 0080 CSO BXO

area: 0025

11835 2013.08.24 4 6 4 S12W67 0060 CSO CAO

location: S10W66

11836 2013.08.26
2013.08.27
7 29 10 N12W39 0110 HSX DSI images/AR_11836_20130903_2345.png beta-gamma

location: N12W37

area: 0200

S2645 2013.08.29       N33W30           plage
S2646 2013.08.30       S13W01           plage
S2647 2013.08.30       S13W35           plage
S2648 2013.08.30       N42W05           plage
S2649 2013.08.31       S04W22           plage
11837 2013.08.31
2013.09.02
21 20 11 S15W47 0120 DSO DAC area: 0220

location: S17W47

S2651 2013.09.01       N20E03           plage
S2652 2013.09.01       S22W52           plage
S2653 2013.09.01       N10W46           plage
S2655 2013.09.03       N03E39         plage
S2656 2013.09.03       S07W03         plage
S2657 2013.09.04   1 1 S04E84 0080   HAX    
Total spot count: 37 62 28  
Sunspot number: 77 112 78  (total spot count + 10 * number of spotted regions)
Weighted SN: 57 82 48  (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): 46 39 43 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)
2011.11 153.5 (cycle peak) 96.7 (cycle peak) 61.1 (+1.2) 5.55
2012.02 106.5 32.9 66.9 (+1.4)
likely cycle 24 max
8.81
2012.05 121.5 69.0 61.7 (-2.9) 7.06
2012.06 119.6 64.5 58.9 (-2.8) 10.08
2012.07 133.9 66.5 57.8 (-1.1) 13.90
2012.08 115.4 63.0 58.2 (+0.4) 7.96
2012.09 122.9 61.4 58.1 (-0.1) 8.07
2012.10 123.3 53.3 58.6 (+0.5) 9.97
2012.11 121.3 61.8 59.7 (+1.1) 7.08
2012.12 108.6 40.8 59.6 (-0.1) 3.44
2013.01 127.1 62.9 58.7 (-0.9) 4.69
2013.02 104.3 38.0 58.4 (-0.3) 6.11
2013.03 111.3 57.9 (58.2 projected, -0.2) 10.56
2013.04 124.8 72.4 (57.9 projected, -0.3) 5.40
2013.05 131.4 78.7 (58.0 projected, +0.1) 9.73
2013.06 110.1 52.5 (58.3 projected, +0.3) 12.60
2013.07 115.5 57.0 (58.3 projected, 0.0) 9.47
2013.08 114.6 66.0 (58.2 projected, -0.1) 7.86
2013.09 106.2 (1) 10.2 (2A) / 76.5 (2B) / 55.8 (2C) (57.8 projected, -0.4) (6.97)

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) Boulder SN current 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 the 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.