Last major update issued on April 30, 2011 at 06:55 UTC.
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Annotated geomagnetic activity charts - Carrington rotation
2107 [Feb.-March
2011] - 2108 [March-April
2011] NEW
The geomagnetic field was quiet to active on April 29. Solar wind speed ranged between 334 and 505 km/s. A high speed stream associated with CH446 dominated the solar wind after 17h UTC.
Solar flux measured at 20h UTC on 2.8 GHz was 109.6 (increasing 2.1 over the last solar rotation). The planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.1). Three hour interval K indices: 13112344 (planetary), 13111235 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight UTC the visible solar disk had 11 spotted regions.
Region 11195 decayed slowly. Flares:
C1.8 at 20:48, C1.5 at 22:55 UTC.
Region 11196 decayed slowly and was quiet.
Region 11197 reemerged with a tiny spot on April 29.
Region 11199 decayed in the leading and intermediate spot section while
more penumbra formed on the trailing spots.
Region 11200 developed slowly and was mostly quiet.
Region 11201 added a few tiny spots.
Region 11202 developed slowly and was quiet.
Region 11203 rotated fully into view. Occasional C class flaring is
likely. Flare: C3.8 at 00:26 UTC.
Spotted regions not numbered by NOAA/SWPC:
[S975] reemerged with a single tiny spot on April 29. Location at
midnight: N22W19
[S980] emerged with a tiny spot on April 29. Location at midnight: N22E37
[S981] emerged with a tiny spot at a high latitude in the southeast
quadrant on April 29. Location at midnight: S46E09
April 27-29: 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 trans equatorial coronal hole (CH446) was in an Earth facing position on April 26-28.
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 fair.
The geomagnetic field is expected to be quiet to active on April 30 - May 1 and quiet to unsettled on May 2 due to effects from CH446, minor storm intervals are possible on April 30.
| 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 | |||||
| 11195 | 2011.04.18 2011.04.19 |
4 | 5 | S15W65 | 0170 | DHO | CSO |
 |
 |
|
| 11196 | 2011.04.19 2011.04.20 |
2 | 7 | S30W45 | 0010 | BXO | BXO |
 |
 |
location: S28W39 area: 0000 |
| 11197 | 2011.04.19 2011.04.21 |
1 | S16W55 | 0000 | AXX |
 |
location: S19W42 |
|||
| S967 | 2011.04.22 | S15W36 | plage | |||||||
| 11201 | 2011.04.24 2011.04.27 |
7 | N16E12 | 0010 | BXO |
 |
 |
location: N15E17 | ||
| 11202 | 2011.04.24 2011.04.28 |
6 | N15W51 | 0030 | CRO |
 |
 |
|||
| 11199 | 2011.04.25 2011.04.26 |
8 | 14 | N18W62 | 0180 | ESI | DSI |
 |
 |
location: N20W61 |
| 11200 | 2011.04.25 2011.04.26 |
4 | 16 | S17E05 | 0030 | BXO | CRI |
 |
 |
|
| S973 | 2011.04.26 | N32W60 |
 |
plage | ||||||
| S974 | 2011.04.27 | S37E27 | plage | |||||||
| S975 | 2011.04.27 | 1 | N22W19 | 0000 | AXX |
 |
||||
| 11203 | 2011.04.28 | 2 | 2 | N18E64 | 0050 | CSO | ESO |
 |
 |
location: N18E66 area: 0090 |
| S976 | 2011.04.28 | N07E32 |
 |
plage | ||||||
| S977 | 2011.04.28 | N05E16 |
 |
plage | ||||||
| S979 | 2011.04.28 | N28W06 |
 |
plage | ||||||
| S980 | 2011.04.29 | 1 | N22E37 | 0000 | AXX |
 |
||||
| S981 | 2011.04.29 | 1 | S46E09 | 0000 | AXX |
 |
||||
| Total spot count: | 20 | 61 | ||||||||
| Sunspot number: | 70 | 171 | ||||||||
| 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 | 112.7 (1) | 79.0 (2A) / 81.8 (2B) | (39.6 predicted, +2.9) | (9.22) |
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.
