Last major update issued on May 28, 2011 at 05:30 UTC.
[Solar and geomagnetic data - last month (updated
daily)]
[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 27, 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 to unsettled on May 27. Solar wind speed ranged between 382 and 537 km/s. A high speed stream from CH450 became the dominant solar wind source early in the day. Early on May 28 active to minor storm conditions have been recorded.
Solar flux measured at 20h UTC on 2.8 GHz was 89.9 (decreasing 19.6 over the last solar rotation). The planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 11.3). Three hour interval K indices: 12223333 (planetary), 12222333 (Boulder).
The background x-ray flux is at the class B4 level.
At midnight UTC the visible solar disk had 6 spotted regions.
Region 11216 was quiet and stable and will rotate to the southwest
limb today.
Region 11223 decayed slowly and quietly.
New region 11224 emerged quickly in the northern hemisphere near the central
meridian on May 26 and was numbered by SWPC the next day. Slow development was
observed on May 27 and the region could produce C flares. A filament in this
region erupted between 03 and 07 UTC. Material was ejected mostly in a
southwesterly direction.
New region 11225 rotated into view at the northeast limb on May 25 and
was noticed by NOAA/SWPC 2 days later.
New region 11226 rotated into view at the southeast limb on May 27. The
region is complex and has a magnetic delta configuration in the trailing
penumbra. Further C class flaring is likely and there's a fair chance of an M
class flare. Flares: C2.1 at 14:53, C5.6 at
16:43, C1.1 at 18:04, C1.4 at 19:43 and C1.2 at 22:46 UTC. A long duration C8.3
event was observed peaking at 03:31 UTC on May 28.
Spotted regions not numbered by NOAA/SWPC:
[S1026] emerged in the northeast quadrant on May 25, was spotless on
May 26 and reemerged on May 27. Location at midnight: N10E18
May 25-27: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
Coronal hole history (since late October
2002)
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 coronal hole (CH451) in the northern hemisphere was Earth facing position on May 27-28.
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 good.
The geomagnetic field is expected to be quiet to minor storm on May 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
green.
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 detected |
Spot count | Location at midnight | Area | Classification | SDO / HMI 4K continuum image with polarity overlay |
Comment | |||
|---|---|---|---|---|---|---|---|---|---|---|
| SWPC | STAR SDO | SWPC | STAR | Current | Previous | |||||
| 11216 | 2011.05.15 2011.05.16 |
1 | 1 | S15W78 | 0070 | HSX | HSX |
 |
 |
|
| 11218 | 2011.05.17 2011.05.18 |
S16W56 |
 |
location: S15W45 plage |
||||||
| 11222 | 2011.05.20 2011.05.25 |
N16W51 |
 |
|||||||
| 11219 | 2011.05.21 | N15W12 |
 |
location: N15W07 | ||||||
| 11223 | 2011.05.21 2011.05.26 |
6 | 10 | S16W00 | 0050 | DSO | CRO |
 |
 |
location: S17E02 area: 0020 |
| S1024 | 2011.05.24 | N29W11 | plage | |||||||
| S1025 | 2011.05.24 | N25W57 | plage | |||||||
| S1026 | 2011.05.25 | 2 | N10E18 | 0000 | AXX |
 |
||||
| 11225 | 2011.05.25 2011.05.27 |
1 | 1 | N18E55 | 0020 | HSX | HSX |
 |
 |
formerly region S1027 location: N16E57 |
| S1028 | 2011.05.25 | S22W06 |
 |
plage | ||||||
| 11224 | 2011.05.26 2011.05.27 |
6 | 17 | N21W15 | 0030 | DSO | DAI |
 |
 |
formerly region S1029 location: N20W13 area: 0080 |
| S1030 | 2011.05.26 | N27W37 |
 |
plage | ||||||
| 11226 | 2011.05.27 | 1 | 7 | S18E74 | 0020 | HSX | DAC |
 |
beta-delta location: S21E79 area: 0200 |
|
| Total spot count: | 15 | 38 | ||||||||
| Sunspot number: | 65 | 98 | ||||||||
| Month | Average measured solar flux | International sunspot number (SIDC) | Smoothed sunspot number | Average ap (3) |
|---|---|---|---|---|
| 2008.07 | 65.7 (SF minimum) | 0.5 | 2.8 (-0.4) | |
| 2008.12 | 69.2 | 0.8 | 1.7 (-) sunspot minimum |
3.25 |
| 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 | 93.9 (1) | 48.0 (2A) / 55.1 (2B) | (44.1 predicted, +3.3) | (7.04) |
1) Running average based on the daily 20:00 UTC observed solar flux value at
2800 MHz.
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.
