Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 21, 2013 at 04:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update August 1, 2013)] [Cycle 24 progress (last update August 1, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update August 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update August 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 August 20, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet on August 20. Solar wind speed at SOHO ranged between 349 and 444 km/s. A weak solar wind shock was observed at SOHO at 21:43 UTC, likely the arrival of the CME observed on August 17. Initially the interplanetary magnetic field was northwards, however, after 02h UTC on August 21 the IMF swung moderately southwards.

Solar flux measured at 20h UTC on 2.8 GHz was 131.5 (increasing 23.9 over the last solar rotation). The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.1). Three hour interval K indices: 10010012 (planetary), 10112213 (Boulder).

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

At midnight UTC the visible solar disk had 13 spotted active regions (in 2K resolution SDO images).

Region 11818 [S06W76] was quiet and decayed slowly.
Region 11820 [S13W32] developed further and has polarity intermixing. C and minor M class flares are possible.
Region 11823 [S07E05] gained a few spots and has weak polarity intermixing.
Region 11824 [S13W54] decayed slowly and quietly.
Region 11825 [N15W42] decayed slowly and quietly.
Region 11827 [S18E46] was quiet and stable.
Region 11828 [N14E55] decayed slowly and was mostly quiet.

Spotted regions not numbered by SWPC:
S2601 [S10W23] was quiet and stable.
S2602 [N21W43] reemerged with penumbra spots.
New region S2623 [S19E26] emerged with several penumbra spots in an old plage area.
New region S2624 [N13W21] emerged with a penumbra spot.
New region S2625 [N25W22] emerged with several spots.
New region S2626 [N05W46] emerged with several spots.

Coronal mass ejections (CMEs)

August 18-19: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
August 20: At least a partial halo CME was observed from 09:18 UTC in LASCO imagery following a large filament eruption in the southern hemisphere. A backsided full halo CME was observed early in the day.

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 trans equatorial coronal hole (CH580) was in an Earth facing position on August 18-19. A coronal hole (CH581) in the northern hemisphere will likely rotate into an Earth facing position on August 22.

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

Forecast

The geomagnetic field is expected to be unsettled to minor storm on August 21 due to CME effects. A high speed stream from CH580 could become geoeffective later in the day and extend the disturbance into August 22. On August 23 the CME observed on August 20 could arrive and cause unsettled to minor storm 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 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
11819 2013.08.09
2013.08.10
      S16W88           plage
11818 2013.08.09
2013.08.10
2 2 2 S05W76 0210 HAX CHO

area: 0300

11820 2013.08.11
2013.08.13
10 33 15 S12W34 0060 DAI DAI area: 0150
S2601 2013.08.13   5 2 S10W23 0010   AXX  
S2602 2013.08.13   3   N21W43 0004   AXX    
11823 2013.08.14
2013.08.15
5 13 5 S08E03 0120 CSO CSO beta-gamma

area: 0190

11822 2013.08.15       S11W14         plage

location: S09W09

S2608 2013.08.16       S21W20           plage
S2609 2013.08.16       S29W41           plage
11824 2013.08.17 3 5 3 S13E54 0050 DAO CRO area: 0030
11827 2013.08.17
2013.08.18
7 12 9 S18E44 0160 DAO DAC area: 0230
S2611 2013.08.17       S10E39         plage
11826 2013.08.17
2013.08.18
      N13W13           plage, SWPC/USAF moved this region to the location of AR S2617

real location: N08W06

S2613 2013.08.17       N22W29           plage
11825 2013.08.17
2013.08.18
12 14 7 N16W40 0080 DAO DAO beta-gamma

area: 0100

11828 2013.08.18
2013.08.19
6 15 2 N16E57 0060 CAO CAO  
S2617 2013.08.18       N14W10         plage
S2619 2013.08.18       N05W58           plage
S2620 2013.08.18       S12E04         merged with AR 11823
S2621 2013.08.19       N20E49         plage
S2622 2013.08.19       S28W15         plage
S2623 2013.08.20   7 2 S19E26 0011   BXO    
S2624 2013.08.20   1   N13W21 0003   AXX    
S2625 2013.08.20   6 2 N25W22 0015   CRO    
S2626 2013.08.20   8 5 N05W46 0040   CRO    
Total spot count: 45 124 54  
Sunspot number: 115 254 164  (total spot count + 10 * number of spotted regions)
Weighted SN: 80 168 98  (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): 69 89 90 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 (57.8 projected, -0.9) 6.11
2013.03 111.3 57.9 (57.3 projected, -0.5) 10.56
2013.04 124.8 72.4 (57.3 projected, 0.0) 5.40
2013.05 131.4 78.7 (57.3 projected, 0.0) 9.73
2013.06 110.1 52.5 (57.6 projected, +0.3) 12.60
2013.07 115.5 57.0 (57.7 projected, +0.1) 9.47
2013.08 114.2 (1) 62.3 (2A) / 96.6 (2B) / 58.5 (2C) (57.6 projected, -0.1) (7.19)

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.