Last major update issued on April 6, 2011 at 04:10 UTC. Minor update posted at 18:10 UTC.
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[Solar cycles 21-24 (last update April 1, 2011)]
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[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
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[POES auroral activity level charts since October
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Annotated geomagnetic activity charts - Carrington rotation 2106 [Jan.-Feb.2011] - 2107 [Feb.-March 2011]
The geomagnetic field was quiet to unsettled on April 5. Solar wind speed ranged between 434 and 592 km/s. A weak solar wind shock was observed at SOHO near 18:10 UTC.
Solar flux estimated at 20h UTC on 2.8 GHz was 109.2 (decreasing 33.9 over the last solar rotation). The planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 6.6). Three hour interval K indices: 21121223 (planetary), 22220012 (Boulder).
The background x-ray flux is at the class B2 level.
At midnight UTC the visible solar disk had 11 spotted regions.
Region 11180 was quiet and will rotate over the northwest limb today.
Region 11183 was quiet and stable.
Region 11184 did not change significantly and was quiet.
Region 11185 developed slowly and quietly.
Spotted regions not numbered by NOAA/SWPC:
[S928] emerged with spots in an old plage field in the northeast quadrant on April 1. Location at midnight: N12W12
[S929] emerged in the southern hemisphere near the central meridian on April 1. Location at midnight: S26W53
[S933] emerged with a few tiny spots in an old plage area in the northeast quadrant on April 4. Location at midnight: N20E18
[S934] emerged in the southwest quadrant on April 4. Location at midnight: S24W63. Note that SWPC has recycled region number 11181 for this region, 11181 is spotless and 13 degrees further west.
[S935] rotated into view at the northeast limb on April 5. Location at midnight: N22E70
[S936] emerged in the southeast quadrant on April 5. Location at midnight: S25E34
[S937] emerged in the southeast quadrant near region S936 on April 5. Location at midnight: S19E32. A minor filament eruption near regions S936/937 was observed starting at 08:59 UTC.
Minor update added at 17:40 UTC on April 6: What was likely another solar wind shock was observed at SOHO near 08:55 UTC. Since then the interplanetary magnetic field has been predominantly southwards. This has caused active to major storm conditions, peaking at a 3-hour planetary A index of 111 (severe storm) from 13 to 16h UTC. The source of the disturbance may have been a large CME which was observed early on April 3 from region 11176 near the southwest limb.
Minor update added at 18:10 UTC: New regions today: Region S938 is emerging quickly to the southeast of region 11185. Region S939 has rotated partly into view at the southeast limb, while region S940 has emerged with spots in an old plage area in the southeast quadrant. The latest high resolution STAR CHARMAP.
April 3-5: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
Coronal hole history (since late October
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
No obvious coronal holes are currently in or near Earth facing positions.
The darkest areas on the solar disk are likely coronal holes.
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 to good.
The geomagnetic field is expected to be quiet to active on April 6 and mostly quiet on April 7-8.
|Coronal holes (1)||Coronal mass ejections (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 polarity overlay
See region S934
|S934||2011.04.04||2||S24W63||0000||BXO||SWPC has recycled region number 11181 for these spots|
|Total spot count:||20||60|
|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)|
|2010.02||84.7||18.8||10.6 (+1.3)||4.15 / 4.61|
|2010.03||83.4||15.4||12.3 (+1.7)||4.58 / 4.65|
|2010.04||75.9||8.0||14.0 (+1.7)||10.22 / 10.24|
|2010.05||73.8||8.7||15.5 (+1.5)||9.18 / 8.15|
|2010.06||72.5||13.6||16.4 (+0.9)||8.17 / 6.85|
|2010.07||79.8||16.1||16.7 (+0.3)||6.31 / 5.15|
|2010.08||79.2||19.6||17.4 (+0.7)||8.49 / 7.77|
|2010.09||81.1||25.2||19.6 (+2.2)||5.33 / 5.45|
|2010.10||81.6||23.5||(22.6 predicted, +3.0)||6.07 / 6.27|
|2010.11||82.5||21.5||(25.7 predicted, +3.1)||4.80 / 5.50|
|2010.12||84.2||14.4||(28.9 predicted, +3.2)||3.41 / 4.35|
|2011.01||83.6||19.1||(31.9 predicted, +3.0)||4.32|
|2011.02||94.6||29.4||(34.4 predicted, +2.5)||5.41|
|2011.03||115.0||56.2||(36.7 predicted, +2.3)||7.79|
|2011.04||110.5 (1)||11.4 (2A) / 68.2 (2B)||(39.6 predicted, +2.9)||(12.9)|
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 preliminary daily SWPC ap indices. Values in red are based on the official NGDC 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.