Last major update issued on April 10, 2011 at 05:25 UTC.
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[Historical solar and geomagnetic data charts 1954-2006
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[POES auroral activity level charts since October
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Annotated geomagnetic activity charts - Carrington rotation
2106 [Jan.-Feb.2011]
- 2107 [Feb.-March
2011]
The geomagnetic field was quiet to unsettled on April 9. Solar wind speed ranged between 372 and 455 km/s.
Solar flux estimated at 20h UTC on 2.8 GHz was 105.0 (decreasing 7.9 over the last solar rotation). The planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 9.6). Three hour interval K indices: 33312311 (planetary), 33312211 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight UTC the visible solar disk had 11 spotted regions.
Region 11184 rotated partly out of view at the northwest limb.
Flare: C1.3 long duration event peaking at
14:48 UTC.
Region 11185 decayed slowly and was quiet.
Region 11186 was mostly unchanged and quiet.
Region 11187 was quiet and stable.
Region 11188 decayed and could soon become spotless.
Region 11189 has many small spots but has not displayed any significant
activity so far. [Note that SWPC currently has this region as 11185 while what
is actually region 11185 for incomprehensible reasons got the new number 11189]
Spotted regions not numbered by NOAA/SWPC:
[S933] emerged with a few tiny spots in an old plage area in the
northeast quadrant on April 4. Location at midnight: N19W29
[S940] emerged in the southeast quadrant on April 6 in an old plage area.
Location at midnight: S22W10
[S943] rotated into view at the northeast limb on April 8. Slow decay was
observed during the latter half of April 9 and the region could soon become
spotless. Location at midnight: N14W51
[S944] emerged in the southeast quadrant on April 9. Location at midnight:
S32E21
[S945] emerged just south of region 11189 on April 9. Location at
midnight: N08E06
April 7-9: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery. Significant backsided CMEs have been observed these days.
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. An extension of the southern polar coronal hole is likely too far to the south to cause any geomagnetic disturbance.
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 to good.
The geomagnetic field is expected to be mostly quiet on April 10-12.
| 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 | |||||
| 11184 | 2011.03.30 2011.04.01 |
1 | 1 | N14W85 | 0080 | HSX | HSX |
 |
 |
|
| S927 | 2011.03.31 | N25W52 | plage | |||||||
| S928 | 2011.04.01 | N16W53 |
 |
plage | ||||||
| 11185 | 2011.04.03 2011.04.04 |
9 | 7 | 0030 | CSO | BXO |
 |
 |
location: N22W02, SWPC location way off | |
| S932 | 2011.04.04 | N13W03 | plage | |||||||
| S933 | 2011.04.04 | 5 | N19W29 | 0000 | BXO |
 |
 |
|||
| 11186 | 2011.04.05 2011.04.06 |
5 | 15 | N23E18 | 0040 | CRO | CAO |
 |
 |
location: N22E20 |
| 11188 | 2011.04.05 2011.04.08 |
2 | 2 | S24W20 | 0010 | BXO | AXX |
 |
 |
|
| S937 | 2011.04.05 | S18W22 |
 |
plage | ||||||
| 11189 | 2011.04.06 2011.04.08 |
3 | 22 | 0030 | CSO | BXI |
 |
 |
location: N17E05 |
|
| 11187 | 2011.04.06 2011.04.07 |
4 | 6 | S18E38 | 0040 | CSO | BXO |
 |
 |
|
| S940 | 2011.04.06 | 2 | S22W10 | 0000 | AXX |
 |
 |
|||
| S941 | 2011.04.06 | S19W38 | plage | |||||||
| S942 | 2011.04.07 | N07W15 | plage | |||||||
| S943 | 2011.04.08 | 3 | N14E51 | 0000 | BXO |
 |
 |
|||
| S944 | 2011.04.09 | 1 | S32E21 | 0000 | AXX |
 |
||||
| S945 | 2011.04.09 | 1 | N08E06 | 0000 | AXX |
 |
||||
| Total spot count: | 24 | 65 | ||||||||
| Sunspot number: | 84 | 175 | ||||||||
| 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 | 110.6 (1) | 21.7 (2A) / 72.3 (2B) | (39.6 predicted, +2.9) | (12.57) |
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.
