Last major update issued on May 26, 2012 at 05:55 UTC.
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The geomagnetic field was quiet to unsettled on May 25. Solar wind speed at SOHO ranged between 434 and 540 km/s, weakly under the influence of a high speed stream from CH518.
Solar flux measured at 20h UTC on 2.8 GHz was 117.2 (decreasing 3.9 over the last solar rotation). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.3). Three hour interval K indices: 22132221 (planetary), 22122321 (Boulder).
The background x-ray flux is at the class B4 level.
At midnight UTC the visible solar disk had 13 spotted active regions (in 2K resolution SDO images).
Region 11484 [N12W81] rotated quietly to the northwest limb.
Region 11486 [N17W25] was quiet and stable.
Region 11488 [N11E15] was quiet and stable.
Region 11489 [S27E22] was quiet and stable.
Region 11490 [S12E46] developed slowly and quietly.
New region 11491 [N23W28] emerged on May 23 and was noticed 2 days later
by SWPC.
New region 11492 [S13E71] rotated partly into view at the southeast limb
on May 24 and was numbered the next day by SWPC. There's some polarity
intermixing and a possible magnetic delta structure in one of the leading
peumbrae. The region could produce a minor M class flare.
Spotted active regions not numbered by NOAA/SWPC:
S1671 [S21E03] was quiet and stable.
S1673 [N26W70] was quiet and stable.
New region S1682 [S22E72] rotated into view at the southeast limb.
New region S1683 [N01E30] emerged with one spot on each side of the
equator.
New region S1684 [N17E19] emerged with a few tiny spots.
New region S1685 [S12W17] emerged on the east side of CH519.
May 23-25: No obviously Earth directed CMEs were observed in LASCO or STEREO imagery.
Coronal hole history (since October
2002)
Compare today's report to the situation one solar rotation ago:
28 days ago
27 days ago
26 days ago
A poorly defined southern hemisphere coronal hole (CH519) was Earth facing on May 23-24.
The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using this method, the extent and intensity of both CHs are consistent with other data sources.
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 poor.
The geomagnetic field is expected to be quiet to unsettled on May 26-28 due to weak effects from CH519, occasional active intervals are possible.
| Coronal holes (1) | Coronal mass ejection (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 magnetic polarity overlay |
Comment | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| SWPC | STAR SDO | SWPC | STAR | Current | Previous | ||||||
| 2K | 1K | ||||||||||
| 11484 | 2012.05.13 | 6 | 15 | 7 | N10W80 | 0190 | DSO | DAI |
 |
 |
location: N12W81 |
| S1659 | 2012.05.15 | N14W36 |
 |
plage | |||||||
| 11485 | 2012.05.15 | S20W71 |
plage location: S18W67 |
||||||||
| 11486 | 2012.05.17 2012.05.18 |
3 | 10 | 4 | N17W26 | 0110 | CSO | CSO |
 |
 |
area: 0230 |
| S1663 | 2012.05.17 | N12W58 | plage | ||||||||
| 11487 | 2012.05.18 2012.05.20 |
N18W75 |
plage location: N20W69 |
||||||||
| S1666 | 2012.05.18 | S19W56 | plage | ||||||||
| S1667 | 2012.05.19 | N04W23 | plage | ||||||||
| 11489 | 2012.05.21 2012.05.22 |
5 | 2 | S30E12 | 0000 | BXO |
 |
 |
location: S27E22 | ||
| S1671 | 2012.05.21 | 4 | 3 | S21E03 | 0000 | BXO |
 |
 |
|||
| 11488 | 2012.05.21 2012.05.22 |
5 | 18 | 11 | N12E13 | 0050 | DSO | CRI |
 |
 |
location: N11E15 |
| S1673 | 2012.05.21 | 1 | 1 | N26W70 | 0000 | AXX |
 |
 |
|||
| S1674 | 2012.05.22 | S21E15 | plage | ||||||||
| 11490 | 2012.05.23 2012.05.24 |
3 | 17 | 9 | S12E45 | 0040 | DSO | DRI |
 |
 |
|
| S1676 | 2012.05.23 | S10E08 | plage | ||||||||
| S1677 | 2012.05.23 | N06W16 | plage | ||||||||
| 11491 | 2012.05.23 2012.05.25 |
6 | 17 | 6 | N23W29 | 0050 | DSO | DAI |
 |
 |
|
| S1679 | 2012.05.23 | N12W31 | plage | ||||||||
| S1680 | 2012.05.24 | N12W16 |
 |
plage | |||||||
| 11492 | 2012.05.24 2012.05.25 |
3 | 16 | 7 | S13E65 | 0090 | CSO | EAI |
 |
 |
beta-gamma area: 0350 location: S13E71 |
| S1682 | 2012.05.25 | 1 | 1 | S22E72 | 0000 | AXX |
 |
||||
| S1683 | 2012.05.25 | 2 | 1 | N01E30 | 0000 | BXO |
 |
||||
| S1684 | 2012.05.25 | 3 | 2 | N17E19 | 0000 | AXX |
 |
||||
| S1685 | 2012.05.25 | 1 | 1 | S12W17 | 0000 | AXX |
 |
||||
| Total spot count: | 26 | 110 | 53 | ||||||||
| Sunspot number: | 86 | 240 | 183 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted penumbral SN: | 56 | 139 | 82 | (Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10) | |||||||
| Relative sunspot number (Wolf number): | 52 | 84 | 101 | k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) for STAR SDO 2K, k = 0.55 for STAR SDO 1K | |||||||
| 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 |
|
| 2011.02 | 94.6 | 29.4 | 33.4 (+2.4) | 6.44 |
| 2011.03 | 115.0 | 56.2 | 36.9 (+3.5) | 8.18 |
| 2011.04 | 112.6 | 54.4 | 41.8 (+4.9) | 8.83 |
| 2011.05 | 95.8 | 41.6 | 47.6 (+5.8) | 8.94 |
| 2011.06 | 95.8 | 37.0 | 53.2 (+5.6) | 8.06 |
| 2011.07 | 94.2 | 43.9 | 57.2 (+4.0) | 8.16 |
| 2011.08 | 101.7 | 50.6 | 59.0 (+1.8) | 7.26 |
| 2011.09 | 133.8 | 78.0 | 59.5 (+0.5) | 12.27 |
| 2011.10 | 137.3 | 88.0 | 59.9 (+0.4) | 8.28 |
| 2011.11 | 153.5 | 96.7 | (61.2 projected, +1.3) | 5.55 |
| 2011.12 | 141.3 | 73.0 | (63.9 projected, +2.7) | 3.78 |
| 2012.01 | 132.5 | 58.3 | (67.4 projected, +3.5) | 7.15 |
| 2012.02 | 106.5 | 33.1 | (71.4 projected, +4.0) | 8.81 |
| 2012.03 | 114.7 | 64.2 | (73.5 projected, +2.1) | 16.08 |
| 2012.04 | 113.0 | 55.2 | (74.5 projected, +1.0) | 10.10 |
| 2012.05 | 124.1 (1) | 84.1 (2A) / 104.3 (2B) | (75.8 projected, +1.3) | (9.02) |
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 quicklook and definitive Potsdam WDC ap indices.
Values in red are based on the definitive
international Potsdam
WDC
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.
