Last major update issued on April 30, 2006 at 05:40 UTC.
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April 3, 2006)]
The geomagnetic field was inactive to quiet on April 29. Solar wind speed ranged between 296 and 424 (all day average 338) km/sec.
Solar flux measured at 20h UTC on 2.8 GHz was 101.2. The planetary A index
was 3 (STAR Ap - based on the mean of three hour interval ap
indices: 3.1).
Three hour interval K indices: 10001211 (planetary), 10001011 (Boulder).
The background x-ray flux is at the class B2 level.
At midnight there were 4 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 2 C class events was recorded during the day. A C2.3 flare at 23:36 UTC had its source in a region just behind the northeast limb.
Region 10875 developed slowly in the main penumbral area while spots
emerged and disappeared in the northern spot section. Flare:
C1.1 at 18:52 UTC.
Region 10876 decayed further and lost all penumbra on the leader spots.
Spotted regions not numbered by NOAA/SEC:
[S647] This region emerged on April 29 in the northeast quadrant.
Location at midnight: N08E28
[S648] A new region rotated into view at the northeast limb on
April 29. Further C class flaring is possible. Location at midnight: N15E75. Flare:
C2.3 at 16:31 UTC. This region was the source of a C5.4 event early on April 30.
This event was associated with a type II radio sweep.
April 27-29: No partly or fully Earth directed CMEs were observed in LASCO imagery.
Coronal hole history (since late October 2002)
Compare today's report with the situation one solar rotation ago:
28 days ago
27 days ago
26 days ago
A recurrent trans equatorial coronal hole (CH222) will likely rotate into an Earth facing position on May 3-4.
Processed SOHO/EIT 284 image at 01:06 UTC on April 30. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet on April 30 - May 2.
| 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.
Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. The dominant signal tonight was from Radio Vibración (Venezuela) while both CPN Radio (Perú) and Radio Cristal del Uruguay were audible at times. Propagation was best to Venezuela and Argentina near local sunrise, while stations from the southeastern part of Brazil dominated during the first hour after LSR (1130 Rádio Nacional had a good signal then).
Compare to the previous day's image.
Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SEC. 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 SEC or where SEC has observed no spots. SEC active region numbers in the table below and in the active region map above are the historic SEC/USAF numbers.
| Active region | Date numbered | SEC spot count |
STAR spot count |
Location at midnight | Area | Classification | Comment |
|---|---|---|---|---|---|---|---|
| 10875 | 2006.04.23 | 31 | 23 | S09W07 | 0280 | DKC | classification was CKI at midnight, area 0400 |
| 10876 | 2006.04.24 | 13 | 9 | S14E18 | 0110 | EAI | classification was CAO at midnight |
| 10877 | 2006.04.26 | S05E11 | plage | ||||
| S647 | 2006.04.29 | 2 | N08E28 | 0010 | BXO | ||
| S648 | 2006.04.29 | 4 | N15E75 | 0040 | DAO | ||
| Total spot count: | 44 | 38 | |||||
| SSN: | 64 | 78 | |||||
| Month | Average solar flux at Earth |
International sunspot number | Smoothed sunspot number |
|---|---|---|---|
| 2000.04 | 184.2 | 125.5 | 120.8 cycle 23 sunspot max. |
| 2000.07 | 202.3 | 170.1 | 119.8 |
| 2001.12 | 235.1 | 132.2 | 114.6 (-0.9) |
| 2005.01 | 102.2 | 31.3 | 34.6 (-0.6) |
| 2005.02 | 97.2 | 29.2 | 33.9 (-0.7) |
| 2005.03 | 89.9 | 24.5 | 33.5 (-0.4) |
| 2005.04 | 86.0 | 24.2 | 31.6 (-1.9) |
| 2005.05 | 99.3 | 42.7 | 28.9 (-2.7) |
| 2005.06 | 93.7 | 39.3 | 28.8 (-0.1) |
| 2005.07 | 96.4 | 40.1 | 29.1 (+0.3) |
| 2005.08 | 90.5 | 36.4 | 27.4 (-1.7) |
| 2005.09 | 91.1 | 21.9 | 25.8 (-1.6) |
| 2005.10 | 77.0 | 8.5 | (24.8 predicted, -1.0) |
| 2005.11 | 86.3 | 18.0 | (22.7 predicted, -2.1) |
| 2005.12 | 90.7 | 41.2 | (19.8 predicted, -2.9) |
| 2006.01 | 83.4 | 15.4 | (16.7 predicted, -3.1) |
| 2006.02 | 76.5 | 4.7 | (13.6 predicted, -3.1) |
| 2006.03 | 75.4 | 10.8 | (11.4 predicted, -2.2) |
| 2006.04 | 88.6 (1) | 53.1 (2) | (10.7 predicted, -0.7) |
1) Running average based on the
daily 20:00 UTC observed solar flux
value at 2800 MHz.
2) Unofficial, accumulated value based on the Boulder (NOAA/SEC)
sunspot number. The official international sunspot number is typically
30-50% lower.
This report has been prepared by Jan Alvestad. It is based partly on my own observations and analysis, and partly on data from some of these solar data sources. All time references are to the UTC day. Comments and suggestions are always welcome.
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