Last major update issued on April 14, 2013 at 06:35 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 unsettled on April 13. Solar wind speed at SOHO ranged between 349 and 519 km/s. A solar wind shock was observed at SOHO at 22:24 UTC, the arrival of the CME observed on April 11. The CME arrived later than expected. The interplanetary magnetic field was predominantly northwards after the arrival of the CME and subsequently only a minor increase in geomagnetic activity was observed. IMF swung southwards after 05 UT on April 14 which will likely increase geomagnetic disturbance levels.
Solar flux measured at 20h UTC on 2.8 GHz was 125.1 (decreasing 0.6 over the last solar rotation). The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.6). Three hour interval K indices: 22110103 (planetary), 22122203 (Boulder).
The background x-ray flux was at the class B3 level.
At midnight UTC the visible solar disk had 9 spotted active regions (in 2K resolution SDO images).
Region 11714 [N12W80] was quiet and stable.
Region 11718 [N20W57] has polarity intermixing and could produce C flares and maybe a minor M class event. The region decayed further and the umbral area is unimpressive.
Region 11719 [N09W23] decayed further and was quiet. There were just traces of umbral area remaining in a few positive polarity spots.
Region 11721 [S19W08] was quiet and stable. C flares are possible.
Region 11722 [S22E03] was quiet and stable.
New region 11723 [S18E49] emerged on April 12 and was numbered by SWPC the next day.
New region 11724 [S27E72] rotated partly into view on April 12 and got its NOAA number the next day.
Spotted regions not numbered by SWPC:
S2353 [N13W02] was quiet and stable.
New region S2354 [N11E23] emerged with a penumbra spot in an old plage area.
April 12-13: 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 small trans equatorial coronal hole (CH565) could rotate into an Earth facing position on April 14. CH565 decreased in size on April 13.
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 April 14 due to CME effects with a chance of minor storm intervals. Quiet conditions are likely on April 15-17 becoming quiet to unsettled on April 18 due to weak effects from CH565.
|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
approaching CSI classification
|Total spot count:||78||134||55|
|Sunspot number:||148||224||125||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||111||162||83||(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):||89||78||69||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||133.8 (1)||55.3 (2A) / 127.7 (2B) / 59.7 (2C)||(51.0 projected, -1.2)||(3.59)|
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.