Last major update issued on April 9, 2011 at 05:45 UTC.
[Solar and geomagnetic data - last month (updated
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update April 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update April 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update April 1, 2011)]
[POES auroral activity level charts since October
2009 - updated April 7, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2106 [Jan.-Feb.2011] - 2107 [Feb.-March 2011]
The geomagnetic field was quiet to unsettled on April 8. Solar wind speed ranged between 384 and 453 km/s. A weak solar wind shock was detected by SOHO/MTOF at 18:21 UTC. Since then the interplanetary magnetic field has been southwards resulting in a relatively weak geomagnetic disturbance.
Solar flux estimated at 20h UTC on 2.8 GHz was 108.7 (decreasing 12.0 over the last solar rotation). The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 7.6). Three hour interval K indices: 20113233 (planetary), 21112333 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight UTC the visible solar disk had 11 spotted regions.
Region 11184 lost the trailing spots and will rotate to the northwest
Region 11185 decayed slowly and was quiet.
Region 11186 decayed and was quiet.
Region 11187 was quiet and stable.
New region 11188 emerged in the southeast quadrant on April 5 and was noticed by NOAA/SWPC 3 days later. The region developed slowly on April 8.
New region 11189 emerged in the northeast quadrant on April 6 and was detected by NOAA/SWPC 2 days later. Slow development was observed on April 8.
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: N16W40
[S933] emerged with a few tiny spots in an old plage area in the northeast quadrant on April 4. Location at midnight: N22W12
[S937] emerged in the southeast quadrant near region S936 on April 5. Location at midnight: S18W09.
[S940] emerged in the southeast quadrant on April 6 in an old plage area. Location at midnight: S24E08
[S943] rotated into view at the northeast limb on April 8. Location at midnight: N13E68
April 6-8: 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. An extension of the southern coronal hole is likely too far to the south to cause any geomagnetic disturbance.
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 unsettled with a chance of active intervals on April 9 and mostly quiet on April 10-11.
|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
|3||6||S25W06||0020||CRO||BXO||formerly region S936|
|6||15||0020||DSO||BXI||formerly region S938
|Total spot count:||37||76|
|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||111.3 (1)||18.9 (2A) / 70.9 (2B)||(39.6 predicted, +2.9)||(12.94)|
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.