Last major update issued on April 25, 2013 at 04:10 UTC.
[Solar and geomagnetic data - last month (updated
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update April 1, 2013)] [Cycle 24 progress (last update April 7, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update April 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update April 4, 2013)]
[POES auroral activity level since October
2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated March 24, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]
The geomagnetic field was quiet to minor storm on April 24. Solar wind speed at SOHO ranged between 313 and 515 km/s, most of the day under the influence of a high speed stream from CH566.
Solar flux measured at 20h UTC on 2.8 GHz was 114.7 (increasing 16.0 over the last solar rotation). The Potsdam WDC planetary A index was 20 (STAR Ap - based on the mean of three hour interval ap indices: 20.5). Three hour interval K indices: 33244353 (planetary), 33344333 (Boulder).
The background x-ray flux was at the class B8 level.
At midnight UTC the visible solar disk had 10 spotted active regions (in 2K resolution SDO images).
Region 11726 [N12W62] lost some spots and had no obvious magnetic
delta structures by the end of the day. A major flare is possible during the
next 2-3 days.
Region 11727 [N24W12] was quiet and stable.
Region 11728 [N20E51] added a few penumbra spots and was quiet.
Region 11729 [S15W22] developed slowly and quietly.
New region 11730 [S19E47] emerged with several spots and has polarity intermixing. C flares are possible.
Spotted regions not numbered by SWPC:
S2368 [S16E20] was quiet and stable.
S2369 [N17E05] was quiet and stable.
S2374 [N16E36] decayed slowly and quietly.
New region S2375 [N08E78] rotated into view with several spots. C and minor M class flares are possible.
New region S2376 [N13W29] emerged with several spots.
April 22-24: 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 trans equatorial coronal hole (CH566) was Earth facing position on April 22-24. CH566 has decayed significantly during its transition of the visible disk.
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 unsettled on April 25-27 due to effects from CH566.
|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:||42||100||41|
|Sunspot number:||92||200||131||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||62||141||82||(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):||55||70||72||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 max)||96.7 (cycle max)||61.1 (+1.2)||5.55|
possible cycle 24 max
|2012.10||123.3||53.3||(57.6 projected, -0.5)||9.97|
|2012.11||121.3||61.8||(56.9 projected, -0.7)||7.08|
|2012.12||108.6||40.8||(55.7 projected, -1.2)||3.44|
|2013.01||127.1||62.9||(54.3 projected, -1.4)||4.69|
|2013.02||104.3||38.0||(53.3 projected, -1.0)||6.11|
|2013.03||111.3||57.9||(52.2 projected, -1.1)||10.56|
|2013.04||122.8 (1)||89.7 (2A) / 112.1 (2B) / 63.9 (2C)||(51.0 projected, -1.2)||(4.85)|
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 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.