Last major update issued on April 14, 2011 at 04:20 UTC. Minor update posted at 19:30 UTC
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The geomagnetic field was quiet to active on April 13. Solar wind speed ranged between 470 and 611 km/s under the influence of a high speed stream originating from an extension of the southern polar coronal hole.
Solar flux estimated at 20h UTC on 2.8 GHz was 117.8 (increasing 27.7 over the last solar rotation). The planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.0). Three hour interval K indices: 43432321 (planetary), 43433211 (Boulder).
The background x-ray flux is at the class B5 level.
At midnight UTC the visible solar disk had 10 spotted regions.
Region 11186 didn't change significantly and was quiet.
Region 11187 was quiet and still has a few tiny spots.
Region 11189 was mostly quiet and stable.
Flare: C1.4 at 10:41 UTC. [Note that SWPC currently has this region as 11185 with
the real region 11185 having been renumbered 11189]
Region 11190 developed moderately quickly and has become a fairly compact
region with polarity intermixing. C flares are likely and there's an increasing
chance of an M class flare.
Flare: C1.1 at 16:07 UTC.
Region 11191 added a few trailing spots.
Flares: C1.9 at 03:30, C1.2 at 07:59 UTC.
Region 11192 was mostly unchanged and quiet.
New region 11193 began to rotate into view at the northeast limb late on
April 12 and was numbered the next day by NOAA/SWPC. This is a complex and
compact region capable of producing M flares.
Flares: C2.2/1F at 06:28 and C2.5 at 13:43 UTC.
Spotted regions not numbered by NOAA/SWPC:
[S944] reemerged with several spots on April 13. Location at midnight:
S32W30
[S950] emerged in the southeast quadrant on April 13. Location at
midnight: S28E56
[S951] emerged in the northeast quadrant on April 13. Location at
midnight: N32E41
Comment added at 19:30 UTC on April 14: Region 11190 has developed quickly today and now has an EKC classification. A magnetic delta structure has formed in a central penumbra and M flares are becoming likely. Region 11193 has large spots as well and an EKC classification. The latest STAR CHARMAP (without polarities).
April 11-13: 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
No obvious coronal holes are currently in or near Earth facing positions.
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 poor to fair.
The geomagnetic field is expected to be mostly quiet on April 14-16.
| 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 | |||||
| 11185 | 2011.04.03 2011.04.04 |
10 | 0030 | CAO |
 |
SWPC data is for region 11189 spotless location: N22W59 |
||||
| S932 | 2011.04.04 | N13W55 | plage | |||||||
| 11186 | 2011.04.05 2011.04.06 |
15 | 21 | N22W33 | 0070 | CSI | CSI |
 |
 |
|
| 11189 | 2011.04.06 2011.04.08 |
2 | 16 | 0010 | AXX | CAO |
 |
 |
location: N16W48 |
|
| 11187 | 2011.04.06 2011.04.07 |
2 | 5 | S22W15 | 0010 | BXO | BXO |
 |
area: 0000 location: S22W13 |
|
| S940 | 2011.04.06 | S22W62 | plage | |||||||
| 11190 | 2011.04.08 2011.04.11 |
34 | 64 | N12W00 | 0150 | EAC | EAC |
 |
 |
beta-gamma |
| S944 | 2011.04.09 | 3 | S32W30 | 0010 | BXO |
 |
||||
| S945 | 2011.04.09 | N08W46 | plage | |||||||
| 11191 | 2011.04.11 2011.04.12 |
1 | 7 | N08E56 | 0140 | HSX | CSO |
 |
 |
location: N08E60 |
| 11192 | 2011.04.12 | 3 | 5 | N10W15 | 0020 | BXO | CRO |
 |
 |
|
| 11193 | 2011.04.12 2011.04.13 |
6 | 18 | N17E71 | 0220 | DAO | DAC |
 |
 |
formerly region S949 location: N15E71 area: 0350 |
| S950 | 2011.04.13 | 1 | S28E56 | 0000 | AXX |
 |
||||
| S951 | 2011.04.13 | 1 | N32E41 | 0000 | AXX |
 |
||||
| Total spot count: | 73 | 141 | ||||||||
| Sunspot number: | 153 | 241 | ||||||||
| 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 | (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 | 110.3 (1) | 35.1 (2A) / 81.1 (2B) | (39.6 predicted, +2.9) | (12.68) |
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.
