Last major update issued on May 27, 2011 at 04:00 UTC. Minor update posted at 18:10 UTC.
[Solar and geomagnetic data - last month (updated
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update May 1, 2011)]
[Solar cycles 1-20]
[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
2009 - updated May 25, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2108 [March-April 2011] - 2109 [April-May 2011]
[Solar polar fields - updated May 26, 2011] NEW
The geomagnetic field was quiet on May 26. Solar wind speed ranged between 348 and 457 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 82.7 (decreasing 26.9 over the last solar rotation). The planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 6.8). Three hour interval K indices: 22102222 (planetary), 22212422 (Boulder).
The background x-ray flux is at the class B1 level.
At midnight UTC the visible solar disk had 9 spotted regions.
Region 11216 was quiet and stable.
Region 11218 was quiet and stable.
Region 11219 was quiet and stable.
Region 11222 decayed and could soon become spotless.
New region 11223 rotated into view at the southeast limb on May 21, became spotless on May 22, reemerged quickly on May 25 and was numbered the next day by NOAA/SWPC. Slow development was observed on May 26.
Spotted regions not numbered by NOAA/SWPC:
[S1027] rotated into view at the northeast limb on May 25. Location at midnight: N16E70
[S1028] emerged in the southeast quadrant on May 25. Location at midnight: S22E07
[S1029] emerged quickly in the northern hemisphere near the central meridian on May 26. C flares are possible. Location at midnight: N20E00
[S1030] emerged at the western edge of the northern part of CH450 in the northwest quadrant on May 26. Location at midnight: N27W24
Minor update posted at 18:10 UTC on May 27: New region S1031 is rotating into view at the southeast limb. The region could be complex and has produced several C flares. A minor M class flare is possible. The region can easily be seen in this high resolution CHARMAP image. The disturbance associated with CH450 has been in progress most of the day and is currently intensifying.
May 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 recurrent trans equatorial coronal hole (CH450) was in an Earth facing position on May 24-25. A small trans equatorial coronal hole (CH451) will likely rotate into an Earth facing position on May 27. CH451 lost a significant part of its area on May 26 and could be closing.
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 minor storm on May 27-28 due to effects from CH450. Quiet to unsettled is likely on May 29-31 due to coronal hole streams.
|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
|6||16||S15E14||0050||CSO||CAI||formerly region S1021|
|Total spot count:||10||36|
|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||94.1 (1)||45.9 (2A) / 54.7 (2B)||(44.1 predicted, +3.3)||(6.88)|
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.