Last major update issued on April 24, 2011 at 06:40 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 quiet to unsettled on April 23. Solar wind speed ranged between 346 and 450 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 119.1 (increasing 3.5 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.6). Three hour interval K indices: 21031211 (planetary), 21141211 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight UTC the visible solar disk had 5 spotted regions.
Region 11193 was quiet and stable. The main penumbra became
asymmetrical.
Region 11195 decayed in the leading spot section as the main penumbra
became symmetrical. The trailing spot section is still complex with poor
separation of opposite polarity fields, particularly in the southwestern part.
While an M class flare is still possible, the region has become mostly quiet
since noon on April 23. Flares: C1.3 at
02:00, C1.9 at 03:53, C1.1 at 04:19, C1.2 at 04:59, C2.4 at 07:34, C1.0 at 14:22 UTC.
Region 11196 has many tiny spots but hadn't displayed any significant
changes over the last day.
Spotted regions not numbered by NOAA/SWPC:
[S965] emerged in the southeast quadrant on April 20. Location at midnight:
S18W04
[S967] emerged in the southeast quadrant on April 22. Location at
midnight: S15E47
April 21-23: 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 to fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be mostly quiet on April 24-26.
| 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 | |||||
| 11191 | 2011.04.11 2011.04.12 |
N08W80 |
 |
location: N08W76
|
||||||
| 11193 | 2011.04.12 2011.04.13 |
18 | 21 | N17W57 | 0270 | EKI | DKI |
 |
 |
beta-gamma |
| 11195 | 2011.04.18 2011.04.19 |
22 | 37 | S16E14 | 0310 | EKC | EHC |
 |
 |
beta-gamma
|
| S960 | 2011.04.18 | N10W34 | plage | |||||||
| 11196 | 2011.04.19 2011.04.20 |
10 | 25 | S26E40 | 0010 | BXO | BXI |
 |
 |
|
| 11197 | 2011.04.19 2011.04.21 |
S16E30 | plage | |||||||
| S963 | 2011.04.19 | S18W25 | plage | |||||||
| 11198 | 2011.04.19 2011.04.21 |
S25W66 |
 |
plage | ||||||
| S965 | 2011.04.20 | 10 | S18W04 | 0000 | AXX |
 |
 |
|||
| S967 | 2011.04.22 | 1 | S15E47 | 0010 | AXX |
 |
 |
|||
| Total spot count: | 50 | 94 | ||||||||
| Sunspot number: | 80 | 144 | ||||||||
| 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) | 66.3 (2A) / 86.5 (2B) | (39.6 predicted, +2.9) | (10.22) |
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.
