Last major update issued on May 1, 2011 at 05:25 UTC.
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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 2107 [Feb.-March 2011] - 2108 [March-April 2011] NEW
The geomagnetic field was unsettled to minor storm on April 30. Solar wind speed ranged between 477 and 770 km/s under the influence of a high speed stream from CH446.
Solar flux measured at 20h UTC on 2.8 GHz was 109.5 (decreasing 4.5 over the last solar rotation). The planetary A index was 24 (STAR Ap - based on the mean of three hour interval ap indices: 24.1). Three hour interval K indices: 43354344 (planetary), 43444333 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight UTC the visible solar disk had 11 spotted regions.
Region 11195 decayed slowly and will be rotating over the southwest
limb today. Flares: C3.2 at 11:51, C1.0 at
12:28, long duration C3.2 peaking at 13:26 UTC.
Region 11196 decayed further and has only a tiny spot left.
Region 11199 developed further in the trailing spot section. Magnetic complexity increased as a magnetic delta structure formed in the largest trailing penumbra. Flares: C1.5 at 08:19 and C1.7 at 09:04 UTC.
Region 11200 displayed no significant changes and was quiet.
Region 11201 decayed slowly and was quiet. The northernmost spot observed the previous day was split off into S985.
Region 11202 was quiet and stable.
Region 11203 added a few spots and was quiet.
Spotted regions not numbered by NOAA/SWPC:
[S982] emerged near the northeast limb on April 30. Location at midnight: N17E70
[S983] rotated into view at the northeast limb on April 30. Location at midnight: N13E79
[S984] emerged in the southwest quadrant on April 30. Location at midnight: S35W15
[S985] was split off from 11201 with both polarity spots emerging. Location at nidnight: N20E03
April 28-30: 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 1 and quiet to unsettled on May 2 due to effects from CH446. Quiet conditions are likely on May 3-4.
|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
|Total spot count:||26||54|
|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 / 5.51|
|2011.02||94.6||29.4||(34.4 predicted, +2.5)||5.41 / 6.44|
|2011.03||115.0||56.2||(36.7 predicted, +2.3)||7.79|
|2011.04||112.6 (1)||81.6 (2A/2B)||(39.6 predicted, +2.9)||(9.71)|
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.