Last major update issued on May 2, 2011 at 05:10 UTC.
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[Solar cycles 21-24 (last update May 1, 2011)]
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[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 1, 2011)]
[POES auroral activity level charts since October
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Annotated geomagnetic activity charts - Carrington rotation 2107 [Feb.-March 2011] - 2108 [March-April 2011] NEW
The geomagnetic field was unsettled to active on May 1. Solar wind speed ranged between 566 and 686 km/s under the influence of a high speed stream from CH446.
Solar flux measured at 20h UTC on 2.8 GHz was 106.1 (decreasing 6.6 over the last solar rotation). The planetary A index was 19 (STAR Ap - based on the mean of three hour interval ap indices: 19.4). Three hour interval K indices: 33334433 (planetary), 34344422 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight UTC the visible solar disk had 12 spotted regions.
Region 11195 rotated out of view at the southwest
limb. Flare: long duration C1.6 event
peaking at 08:14 UTC.
Region 11199 rotated partly out of view at the northwest limb. Flare: C6.5 at 23:32 UTC.
Region 11200 was quiet and stable.
Region 11201 was quiet and stable.
Region 11202 rotated to the northwest limb.
Region 11203 decayed slowly and quietly.
Spotted regions not numbered by NOAA/SWPC:
[S975] reemerged with a single tiny spot on May 1. Location at midnight: N18W39
[S980] reemerged with a single spot on May 1. Location at midnight: N22E09
[S982] emerged near the northeast limb on April 30 and developed slowly on May 1. Location at midnight: N17E54
[S983] rotated into view at the northeast limb on April 30. Location at midnight: N13E66
[S985] decayed on May 1 and was quiet. Location at nidnight: N21W06
[S986] emerged in the southeast quadrant on May 1. Location at midnight: S20E36
[S987] emerged in the northwest quadrant in an old plage area on May 1. Location at midnight: N35W16
April 29 - May 1: 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
A trans equatorial coronal hole (CH446) was in an Earth facing position on April 26-28.
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 May 2 and quiet to unsettled on May 3 due to effects from CH446. Quiet conditions are likely on May 4.
|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
rotated out of view
|Total spot count:||17||37|
|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||23.2 (+3.6)||6.07 / 6.27|
|2010.11||82.5||21.5||(26.9 predicted, +3.7)||4.80 / 5.50|
|2010.12||84.2||14.4||(30.1 predicted, +3.2)||3.41 / 4.35|
|2011.01||83.6||19.1||(33.1 predicted, +3.0)||4.32 / 5.51|
|2011.02||94.6||29.4||(35.6 predicted, +2.5)||5.41 / 6.44|
|2011.03||115.0||56.2||(37.9 predicted, +2.3)||7.79|
|2011.04||112.6||54.4||(40.8 predicted, +2.9)||9.71|
|2011.05||106.1 (1)||1.8 (2A) / 57.0 (2B)||(44.1 predicted, +3.3)||(19.38)|
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.