Last major update issued on April 11, 2013 at 04:30 UTC. Minor update added at 15:05 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 on April 10. Solar wind speed at SOHO ranged between 303 and 417 km/s. A low speed stream associated with CH564 was observed beginning at SOHO near 02:30 UTC. As the interplanetary magnetic field was mostly northwards, there was only a minor increase in geomagnetic activity.
Solar flux measured at 20h UTC on 2.8 GHz was 148.0 (increasing 25.2 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: 3.9). Three hour interval K indices: 01111012 (planetary), 11222322 (Boulder).
The background x-ray flux was at the class B7 level.
At midnight UTC the visible solar disk had 11 spotted active regions (in 2K resolution SDO images).
Region 11711 [S17W68] was quiet and stable.
Region 11714 [N12W38] decayed slowly and quietly.
Region 11716 [S19W28] was quiet and stable.
Region 11717 [S11W00] was quiet and stable.
Region 11718 [N21W18] has many spots and a large penumbral coverage, however, umbral area is umpressive. M class flares are possible.
Region 11719 [N09E16] developed slowly and was mostly quiet.
Region 11720 [N10W46] reemerged with penumbra spots.
New region 11721 [S18E33] emerged on April 9 and developed on April 10. There's polarity intermixing and opposite polarity spots are very close in the central parts. At least C flares are possible.
New region 11722 [S20E44] emerged on April 9 and developed slowly on April 10 when it was numbered by SWPC.
Spotted regions not numbered by SWPC:
New region S2348 [N07W04] emerged with penumbra spots in an old plage area.
New region S2349 [S11W00] emerged with penumbra spots.
Minor updated posted at 15:05 UTC: AR 11719 produced a long duration M6.5/3B event peaking at 07:16 UTC. This event was associated with a significant increase in proton levels at Earth and a very large, wide and fast full halo CME. The CME could reach Earth early on April 13 and cause major to severe geomagnetic storm conditions.
A tiny spot was observed at S70W06 at 23:45 UTC on April 10, see image below. The spot is too small to be visible in 1 or 2K images.
April 8-10: 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 small coronal hole (CH564) in the northern hemisphere was in an Earth facing position on April 6.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet on April 11-13.
|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
|7||N08W88||0180||DAI||rotated out of view|
|Total spot count:||73||133||61|
|Sunspot number:||163||243||141||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||113||168||96||(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):||98||85||78||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||134.0 (1)||42.1 (2A) / 126.3 (2B) / 59.3 (2C)||(51.0 projected, -1.2)||(3.34)|
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.