Last major update issued on April 27, 2011 at 04:00 UTC.
[Solar and geomagnetic data - last month (updated
daily)]
[Solar wind and electron fluence charts (updated
daily)
[Solar cycles 21-24 (last update April 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last
update April 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and
24 (last update April 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006
(last update April 5, 2007)]
[Archived reports since January 2003 (last update April
1, 2011)]
[POES auroral activity level charts since October
2009 - updated April 19, 2011]
Annotated geomagnetic activity charts - Carrington rotation
2107 [Feb.-March
2011] - 2108 [March-April
2011] NEW
The geomagnetic field was very quiet on April 26. Solar wind speed ranged between 376 and 463 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 109.4 (decreasing 8.2 over the last solar rotation). The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.9). Three hour interval K indices: 00101111 (planetary), 10111211 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight UTC the visible solar disk had 9 spotted regions.
Region 11195 decayed further with the trailing penumbra splitting.
There is still a magnetic delta structure in the southernmost penumbra. Although
the region has been quiet the last days, there is a possibility of an M class
flare.
Region 11196 has many tiny spots with no significant
changes observed over the last days.
Region 11197 was quiet and stable.
New region 11199 emerged in the northwest quadrant on April 25 and was
numbered the next day by NOAA/SWPC. The region developed significantly on April
26 and could produce C flares.
New region 11200 emerged in the southeast quadrant on April 25 with SWPC
numbering it the following day.
Spotted regions not numbered by NOAA/SWPC:
[S968] decayed slowly. Location at midnight: N15E49. The region
produced a C2.0 flare at 02:33 UTC on April 27.
[S969] emerged in the northeast quadrant on April 24. Location at
midnight: N15W12
[S973] emerged in the northwest quadrant on April 26. Location at midnight:
N33W20
April 24-26: 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) will rotate into 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 fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet to unsettled on April 27-28. A high speed stream associated with CH446 could cause quiet to active conditions on April 29 - May 1.
| 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 | 31 | S17W25 | 0210 | EHO | EHO |
 |
 |
beta-gamma-delta area: 0350 |
| 11196 | 2011.04.19 2011.04.20 |
1 | 16 | S28E02 | 0005 | AXX | BXO |
 |
 |
location: S27W00 |
| 11197 | 2011.04.19 2011.04.21 |
1 | S16W13 | 0000 | AXX |
 |
 |
location: S17W09 | ||
| S963 | 2011.04.19 | S18W64 | plage | |||||||
| S965 | 2011.04.20 | S17W44 |
 |
plage | ||||||
| S967 | 2011.04.22 | 1 | S15E04 | 0000 | AXX |
 |
 |
|||
| S968 | 2011.04.24 | 1 | N15E49 | 0000 | AXX |
 |
 |
|||
| S969 | 2011.04.24 | 5 | N15W12 | 0000 | BXO |
 |
 |
|||
| 11199 | 2011.04.25 2011.04.26 |
8 | 18 | N21W23 | 0020 | CAI | DAI |
 |
 |
formerly region S972 area: 0070 |
| 11200 | 2011.04.25 2011.04.26 |
4 | 4 | S17E42 | 0010 | BXO | BXO |
 |
 |
formerly region S971 |
| S973 | 2011.04.26 | 3 | N33W20 | 0000 | BXO |
 |
||||
| Total spot count: | 17 | 80 | ||||||||
| Sunspot number: | 57 | 170 | ||||||||
| 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 | 113.1 (1) | 73.0 (2A) / 84.3 (2B) | (39.6 predicted, +2.9) | (9.59) |
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.
