Last major update issued on April 28, 2011 at 04:10 UTC.
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Annotated geomagnetic activity charts - Carrington rotation
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2011] NEW
The geomagnetic field was very quiet on April 27. Solar wind speed ranged between 352 and 429 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 107.9 (decreasing 5.4 over the last solar rotation). The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.8). Three hour interval K indices: 00001111 (planetary), 10011011 (Boulder).
The background x-ray flux is at the class B2 level.
At midnight UTC the visible solar disk had 9 spotted regions.
Region 11195 decayed slowly and quietly.
Region 11196 has many tiny spots with no significant
changes observed over the last days.
Region 11199 matured as the opposite polarity spots increased their
spatial separation.
Region 11200 decayed and was quiet.
New region 11201 rotated into view several days ago and was numbered ny
SWPC because of flare activity. Flare: C2.0
at 02:33 UTC (associated with a CME off the northeast limb).
Spotted regions not numbered by NOAA/SWPC:
[S967] has a couple of tiny spots and could soon become spotless.
Location at midnight: S15W10
[S969] emerged in the northeast quadrant on April 24. Location at
midnight: N15W24
[S974] emerged in the southeast quadrant on April 27. Location at midnight:
S37E53
[S975] emerged in the northeast quadrant on April 27. Location at
midnight: N17E14
April 25-27: 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 fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet on April 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 |
7 | 17 | S17W38 | 0230 | DHO | DHO |
 |
 |
area: 0300 |
| 11196 | 2011.04.19 2011.04.20 |
12 | S28W12 | 0000 | BXO |
 |
 |
location: S25W13 |
||
| 11197 | 2011.04.19 2011.04.21 |
S16W27 |
 |
plage location: S17W22 |
||||||
| S965 | 2011.04.20 | S17W57 | plage | |||||||
| S967 | 2011.04.22 | 1 | S15W10 | 0000 | AXX |
|
 |
|||
| 11201 | 2011.04.24 2011.04.27 |
2 | N16E40 | 0000 | AXX |
 |
 |
formerly region S968 | ||
| S969 | 2011.04.24 | 7 | N15W24 | 0010 | BXO |
 |
 |
|||
| 11199 | 2011.04.25 2011.04.26 |
12 | 17 | N21W34 | 0120 | DAI | DAO |
 |
 |
|
| 11200 | 2011.04.25 2011.04.26 |
2 | S17E28 | 0000 | AXX |
 |
 |
location: S18E31 | ||
| S973 | 2011.04.26 | N33W33 |
 |
plage | ||||||
| S974 | 2011.04.27 | 1 | S37E53 | 0000 | AXX |
 |
||||
| S975 | 2011.04.27 | 2 | N17E14 | 0000 | BXO |
 |
||||
| Total spot count: | 19 | 61 | ||||||||
| Sunspot number: | 39 | 151 | ||||||||
| 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 | 112.9 (1) | 74.3 (2A) / 82.6 (2B) | (39.6 predicted, +2.9) | (9.33) |
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.
