Last major update issued on April 5, 2012 at 05:40 UTC.
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[Solar wind and electron fluence charts (updated daily)
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[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2012)]
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[POES auroral activity level since October
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Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]
The geomagnetic field was quiet to unsettled on April 4. Solar wind speed at SOHO ranged between 275 and 341 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 102.1 (decreasing 37.4 over the last solar rotation). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.5). Three hour interval K indices: 33112223 (planetary), 22011223 (Boulder).
The background x-ray flux is at the class B2 level.
At midnight UTC the visible solar disk had 7 spotted active regions (in 2K resolution SDO images).
Region 11445 [S22W86] was quiet and stable.
Region 11448 [S18W34] was quiet and stable.
Region 11450 [N14W19] decayed in the leading spot section and redeveloped polarity intermixing in the central spot section.
Region 11451 [N17E03] was quiet and stable.
Region 11452 [N17E19] decayed slowly and was quiet.
Spotted regions not numbered by SWPC:
[S1565] rotated into view at the northeast limb on April 4. Location at midnight: N23E80
[S1566] emerged in the southwest quadrant on April 4. Location at midnight: S27W24
April 2-4: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery. A filament eruption in the northern hemisphere early on April 2 caused a CME and was observed in both LASCO (northern hemisphere limb only) and STEREO images. There's a slight chance of a flank impact from this CME on April 5.
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
An extension of the southern polar coronal hole was probably too far to the south on April 3 to become geoeffective. A recurrent trans equatorial coronal hole (CH512) will likely rotate into an Earth facing position on April 9.
The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using this method, the extent and intensity of both CHs are consistent with other data sources.
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 5 with a chance of active intervals and quiet to unsettled on April 6-7.
|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 higher resolution image) Compare to the previous day's image
When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) 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:||20||47||19|
|Sunspot number:||60||117||79||(total spot count + 10 * number of spotted regions)|
|Weighted penumbral SN:||35||60||32||(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):||36||41||43||k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) 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
|2008.07||65.7 (SF minimum)||0.5||2.8 (-0.4)|
|2011.10||137.3||88.0||(60.1 projected, +0.6)||8.28|
|2011.11||153.5||96.7||(61.6 projected, +1.5)||5.55|
|2011.12||141.3||73.0||(64.3 projected, +2.7)||3.78|
|2012.01||132.5||58.3||(67.8 projected, +3.5)||7.15|
|2012.02||106.5||33.1||(71.8 projected, +4.0)||8.81|
|2012.03||114.7||64.2||(73.9 projected, +2.1)||16.08|
|2012.04||104.7 (1)||8.0 (2A) / 59.8 (2B)||(74.9 projected, +1.0)||(10.09)|
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) Month average to date.
3) Running average based on the quicklook 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.