Last major update issued on April 7, 2011 at 04:40 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 4, 2011]
Annotated geomagnetic activity charts - Carrington rotation
2106 [Jan.-Feb.2011]
- 2107 [Feb.-March
2011]
The geomagnetic field was quiet to major storm on April 6. Solar wind speed ranged between 473 and 578 km/s. A disturbance was observed starting at SOHO near 08:55 UTC (and peaked geomagnetically during the 13 to 16h UTC interval with an ap of 111). This was likely the arrival of a large CME observed in association with a long duration event involving region 11176 late on April 2 and early on April 3.
Solar flux estimated at 20h UTC on 2.8 GHz was 117.1 (decreasing 14.2 over the last solar rotation). The planetary A index was 26 (STAR Ap - based on the mean of three hour interval ap indices: 25.5). Three hour interval K indices: 33146533 (planetary), 23245433 (Boulder).
The background x-ray flux is at the class B3 level. A total of 3 C flares were observed during the latter half of the day, all from a source just behind the northeast limb.
At midnight UTC the visible solar disk had 12 spotted regions.
Region 11183 was quiet and stable.
Region 11184 developed slowly in the intermediate spot section.
Region 11185 decayed slowly and lost penumbra on the trailing spots.
New region 11186 rotated into view on April 5 and was numbered by NOAA/SWPC
the next day. The region developed slowly on April 6.
Spotted regions not numbered by NOAA/SWPC:
[S928] emerged with spots in an old plage field in the northeast quadrant on
April 1. Location at midnight: N13W25
[S933] emerged with a few tiny spots in an old plage area in the
northeast quadrant on April 4. Location at midnight: N21E09
[S936] emerged in the southeast quadrant on April 5. Location at midnight:
S26E20
[S937] emerged in the southeast quadrant near region S936 on April 5.
Location at midnight: S19E19.
[S938] emerged in the northeast quadrant on April 6. Location at midnight:
N18E45
[S939] rotated into view at the southeast limb on April 6. Location at
midnight: S20E78
[S940] emerged in the southeast quadrant on April 6 in an old plage area.
Location at midnight: S23E30
[S941] emerged in the southern hemisphere near the central meridian on
April 6. Location at midnight: S20W03
April 4-6: 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 very poor. Propagation on long distance northeast-southwest paths is fair to good.
The geomagnetic field is expected to be quiet to unsettled on April 7 and quiet on April 8-9.
| 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 | |||||
| 11183 | 2011.03.26 2011.03.27 |
1 | 2 | N15W71 | 0040 | HSX | HSX |
 |
 |
|
| S924 | 2011.03.29 | N36W56 | plage | |||||||
| 11184 | 2011.03.30 2011.04.01 |
9 | 14 | N16W41 | 0110 | DSO | CAI |
 |
 |
|
| S927 | 2011.03.31 | N25W13 | plage | |||||||
| S928 | 2011.04.01 | 7 | N13W25 | 0000 | BXO |
 |
 |
|||
| S929 | 2011.04.01 | S26W66 |
 |
plage | ||||||
| 11185 | 2011.04.03 2011.04.04 |
5 | 9 | N22E38 | 0070 | CSO | CAI |
 |
 |
|
| S932 | 2011.04.04 | N13E36 | plage | |||||||
| S933 | 2011.04.04 | 7 | N21E09 | 0000 | BXO |
 |
 |
|||
| S934 | 2011.04.04 | S24W76 |
 |
|||||||
| 11186 | 2011.04.05 2011.04.06 |
1 | 11 | N22E58 | 0010 | AXX | DRO |
 |
 |
formerly region S935 area: 0030 |
| S936 | 2011.04.05 | 4 | S26E20 | 0010 | BXO |
 |
 |
|||
| S937 | 2011.04.05 | 1 | S19E19 | 0000 | AXX |
 |
 |
|||
| S938 | 2011.04.06 | 3 | N18E45 | 0010 | BXO |
 |
||||
| S939 | 2011.04.06 | 4 | S20E78 | 0010 | BXO |
 |
||||
| S940 | 2011.04.06 | 1 | S23E30 | 0000 | AXX |
 |
||||
| S941 | 2011.04.06 | 1 | S20W03 | 0000 | AXX |
 |
||||
| Total spot count: | 16 | 64 | ||||||||
| Sunspot number: | 56 | 184 | ||||||||
| 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 |
| 2011.02 | 94.6 | 29.4 | (34.4 predicted, +2.5) | 5.41 |
| 2011.03 | 115.0 | 56.2 | (36.7 predicted, +2.3) | 7.79 |
| 2011.04 | 111.6 (1) | 13.2 (2A) / 66.2 (2B) | (39.6 predicted, +2.9) | (15.0) |
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.
