Last major update issued on August 20, 2013 at 02:45 UTC.
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[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)]
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[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]
The geomagnetic field was quiet on August 19. Solar wind speed at SOHO ranged between 392 and 472 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 128.3 (increasing 21.6 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 21111111 (planetary), 22112211 (Boulder).
The background x-ray flux was at the class B5 level.
At midnight UTC the visible solar disk had 14 spotted active regions (in 2K resolution SDO images).
Region 11818 [S06W62] was mostly quiet. An M class flare is still
possible due to the magnetic delta structure in the northern part of the large
Region 11820 [S13W20] developed quickly as new flux emerged. The region has polarity intermixing.
Region 11822 [S09E04] was quiet and stable.
Region 11823 [S07E18] gained a few spots and has weak polarity intermixing.
Region 11824 [S13W40] decayed slowly and quietly.
Region 11825 [N15W27] matured with minor polarity intermixing still observed. C flares are possible.
Region 11827 [S19E59] was quiet and stable.
New region 11828 [N14E68] rotated into view on August 18 and was numbered by SWPC the next day.
Spotted regions not numbered by SWPC:
S2601 [S08W07] was quiet and stable.
S2611 [S11E52] reemerged with a pneumbra spot.
S2617 [N14E03] decayed slowly and quietly.
S2620 [S12E17] developed slowly and quietly.
New region S2621 [N20E62] emerged with a penumbra spot.
New region S2622 [S28W20] emerged with a penumbra spot.
August 18-19: No obviously Earth directed CMEs were observed in LASCO and
August 17: An asymmetric full halo CME was observed after the M class events in AR 11818. The core of the CME was likely not Earth directed, however, a glancing blow is possible on August 20.
Coronal hole history (since October
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.
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 poor.
The geomagnetic field is expected to be quiet to active on August 20 due to weak CME effects. Quiet to active conditions are likely on August 21-22 as a high speed stream from CH580 becomes geoeffective.
|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
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.
(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
|Spot count||Location at midnight||Area||Classification||SDO / HMI 4K continuum
image with magnetic polarity overlay
|3||S19W88||0060||CSO||rotated out of view|
spotless, however, SWPC/USAF moved this region to the location of AR
real location: N08E07
|S2620||2013.08.18||7||3||S12E17||0023||DRO||split off from AR 11823|
|Total spot count:||61||119||49|
|Sunspot number:||161||259||149||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||101||160||90||(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):||97||91||82||k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for STAR SDO 2K, k = 0.55 for STAR SDO 1K|
|Month||Average measured solar flux||International sunspot number (SIDC)||Smoothed sunspot number||Average ap
|2011.11||153.5 (cycle peak)||96.7 (cycle peak)||61.1 (+1.2)||5.55|
likely cycle 24 max
|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||113.3 (1)||58.6 (2A) / 95.6 (2B) / 57.0 (2C)||(57.6 projected, -0.1)||(7.41)|
1) Running average based on the daily 20:00 UTC observed solar flux value at
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.