Last major update issued on April 27, 2011 at 04:00 UTC.
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Annotated geomagnetic activity charts - Carrington rotation 2107 [Feb.-March 2011] - 2108 [March-April 2011] NEW
The geomagnetic field was very quiet on April 26. Solar wind speed ranged between 376 and 463 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 109.4 (decreasing 8.2 over the last solar rotation). The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.9). Three hour interval K indices: 00101111 (planetary), 10111211 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight UTC the visible solar disk had 9 spotted regions.
Region 11195 decayed further with the trailing penumbra splitting.
There is still a magnetic delta structure in the southernmost penumbra. Although
the region has been quiet the last days, there is a possibility of an M class
Region 11196 has many tiny spots with no significant changes observed over the last days.
Region 11197 was quiet and stable.
New region 11199 emerged in the northwest quadrant on April 25 and was numbered the next day by NOAA/SWPC. The region developed significantly on April 26 and could produce C flares.
New region 11200 emerged in the southeast quadrant on April 25 with SWPC numbering it the following day.
Spotted regions not numbered by NOAA/SWPC:
[S968] decayed slowly. Location at midnight: N15E49. The region produced a C2.0 flare at 02:33 UTC on April 27.
[S969] emerged in the northeast quadrant on April 24. Location at midnight: N15W12
[S973] emerged in the northwest quadrant on April 26. Location at midnight: N33W20
April 24-26: 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) will rotate into 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 fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet to unsettled on April 27-28. A high speed stream associated with CH446 could cause quiet to active conditions on April 29 - May 1.
|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
|8||18||N21W23||0020||CAI||DAI||formerly region S972
|4||4||S17E42||0010||BXO||BXO||formerly region S971|
|Total spot count:||17||80|
|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||113.1 (1)||73.0 (2A) / 84.3 (2B)||(39.6 predicted, +2.9)||(9.59)|
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) 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.