Last major update issued on August 14, 2013 at 04:30 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 to unsettled on August 13. Solar wind speed at SOHO ranged between 317 and 423 km/s. A disturbance after about 08h UTC was associated with a minor increase in solar wind speed and an increased total field of the interplanetary magnetic field as well as frequent southward excursions of the IMF. This may be associated with a corotating interaction region ahead of the stream from CH579.
Solar flux measured at 20h UTC on 2.8 GHz was 122.0 (increasing 10.7 over the last solar rotation). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.4). Three hour interval K indices: 20121322 (planetary), 20132522 (Boulder).
The background x-ray flux was at the class B6 level.
At midnight UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).
Region 11816 [S19W25] was quiet and stable.
Region 11817 [S21W04] decayed as the opposite polarity fields became better separated. The magnetic delta structure disappeared.
Region 11818 [S07E35] developed further and has acquired a weak magnetic delta structure at the northeast corner of the large penumbra. C and M class flares are possible.
Region 11819 [S18E08] developed slowly and quietly.
New region 11820 [S13E60] rotated into view on August 11 and was numbered by SWPC 2 days later. The region decayed slowly.
Region 11809, just behind the northwest limb, became quite active during the day and produced 5 C flares.
Spotted regions not numbered by SWPC:
S2600 [N03W20] decayed slowly and quietly.
New region S2601 [S08E78] rotated into view.
New region S2602 [N25E45] emerged with a few penumbra spots in an old plage area.
August 11-13: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
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 will be rotating across the central meridian on August 11-16.
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.
The geomagnetic field is expected to be quiet to active with a chance of minor storm intervals on August 14-19 due to effects from CH579.
|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:||48||105||51|
|Sunspot number:||98||185||111||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||74||126||77||(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):||59||65||61||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||108.3 (1)||35.1 (2A) / 83.7 (2B) / 52.7 (2C)||(57.6 projected, -0.1)||(6.06)|
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.