Last major update issued on April 17, 2006 at 02:55 UTC.
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April 3, 2006)]
The geomagnetic field was quiet to active on April 16. Solar wind speed ranged between 533 and 643 (all day average 582) km/sec, decreasingly under the influence of a high speed stream from CH220.
Solar flux measured at 20h UTC on 2.8 GHz was 76.5. 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: 43222211 (planetary), 44322222 (Boulder).
The background x-ray flux is at the class A3 level.
At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.
Region 10871 decayed and could become spotless late today or tomorrow.
April 14-16: 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 coronal hole in the northern hemisphere (CH221) could rotate to a partly Earth facing position on April 17.
Processed SOHO/EIT 284 image at 19:06 UTC on April 16. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to unsettled on April 17 and quiet on April 18-19. A few unsettled intervals are possible on April 20 due to effects from CH221.
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 very poor. Propagation on long distance northeast-southwest paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela) and Radio Cristal del Uruguay. Most of the overseas stations audible during the night were from Venezuela with good signals noted from 1290 Puerto Cabello and 1390 Fé y Alegria.
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 |
---|---|---|---|---|---|---|---|
10870 | 2006.04.10 | S09W56 | plage | ||||
10871 | 2006.04.10 | 5 | 2 | S06W33 | 0060 | CSO | classification was HSX at midnight, area 0020. SEC data based on real observations or extrapolation from the previous day? |
10872 | 2006.04.11 | 6 | S06E08 | 0020 | BXO | spotless | |
10873 | 2006.04.11 | 4 | N01W17 | 0010 | BXO | spotless | |
Total spot count: | 15 | 2 | |||||
SSN: | 45 | 12 |
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 | 89.0 (1) | 35.1 (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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