Last major update issued on August 18, 2013 at 06:40 UTC.
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[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]
The geomagnetic field was quiet on August 17. Solar wind speed at SOHO ranged between 558 and 734 km/s under the influence of a high speed stream from CH579, slowly decreasing all day.
Solar flux measured at 17h UTC on 2.8 GHz was 123.2 (increasing 13.8 over the last solar rotation, the measurements at 20 and 23h UTC were both influenced by the LDE in AR 11818). The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.1). Three hour interval K indices: 22212112 (planetary), 22322222 (Boulder).
The background x-ray flux was at the class B5 level.
At midnight UTC the visible solar disk had 13 spotted active regions (in 2K resolution SDO images).
Region 11817 [S21W60] decayed slowly and quietly. The region has a magnetically simple
Region 11818 [S06W33] has all umbrae within a single penumbral structure. Further M class flares are possible as long as the magnetic delta structure in the northern part remains. C5+ events: M3.3/2B at 18:24 and a long duration M1.4 event peaking at 19:33 UTC. An asymmetric full halo CME was observed in LASCO imagery after these events.
Region 11820 [S14E08] decayed slowly and quietly.
Region 11822 [S07E31] decayed slowly and quietly.
Region 11823 [S07E45] was quiet and stable.
New region 11824 [S15W12] emerged quickly and could produce C flares.
Spotted regions not numbered by SWPC:
S2601 [S19E19] was quiet and stable.
New region S2610 [S19E83] rotated into view.
New region S2611 [S10E78] rotated into view with a penumbra spot.
New region S2612 [N07E36] emerged with umbra forming in one spot.
New region S2613 [N25E18] emerged with a penumbra spot.
New region S2614 [S16W23] emerged with penumbra spots.
New region S2615 [N15E03] emerged with several penumbra spots.
August 15-16: No obviously Earth directed CMEs were observed in LASCO and
August 17: An asymmtric full halo CME was observed after the M class events in AR 11818. The CME could reach Earth on August 19 or 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 coronal hole (CH579) in the northern hemisphere rotated across the central meridian on August 11-15. A recurrent trans equatorial coronal hole (CH580) will rotate into an Earth facing position on August 18-19.
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 to fair.
The geomagnetic field is expected to be quiet with a chance of unsettled intervals on August 18-19 due to effects from CH579. The halo CME observed on August 17 could reach Earth either late on August 19 or on August 20 and cause unsettled to minor storm conditions. 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
|Total spot count:||36||96||34|
|Sunspot number:||96||226||144||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||61||129||67||(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):||62||60||56||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||111.7 (1)||49.1 (2A) / 89.5 (2B) / 53.8 (2C)||(57.6 projected, -0.1)||(7.71)|
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.