Last major update issued on April 16, 2005 at 03:30 UTC.
[Solar and
geomagnetic data - last month (updated daily)]
[Solar wind and
electron fluence charts (updated daily)]
[Solar cycles 21-23
(last update April 4, 2005)]
[Solar cycles 1-20]
[Graphical comparison
of cycles 21, 22 and 23 (last update April 4, 2005)]
[Graphical
comparison of cycles 2, 10, 13, 17, 20 and 23 (last update April 4, 2005)]
[Historical solar and
geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports
(last update April 15, 2005)]
The geomagnetic field was quiet to active on April 15. Solar wind speed ranged between 439 and 537 km/sec under the slowly decreasing influence of a high speed stream from CH157.
Solar flux measured at 20h UTC on 2.8 GHz was 84.9. The planetary
A
index was 13 (STAR Ap - based on the mean of three hour interval ap
indices: 13.1).
Three hour interval K indices: 34223323 (planetary), 34222323 (Boulder).
The background x-ray flux is at the class A5 level.
At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.
Region 10750 decayed slowly and quietly.
Region 10752 decayed slowly with the easternmost spots disappearing.
Region 10754 decayed slightly and lost penumbra on the trailing spots.
April 13-15: No obvious fully or partly Earth directed CMEs were observed.
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 coronal hole (CH158) in the southern hemisphere will be in an Earth facing position on April 15-16.
Processed SOHO/EIT 284 image at 01:06 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 16-17. Effects from CH158 could reach Earth on April 18 and cause unsettled to active conditions that day and on April 19.
| 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) Material from a CME is likely to impact 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 to very poor. Propagation along long distance north-south paths is poor to fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay. The best frequency was 930 kHz which had a mix of CJYQ, 2 stations from Brazil and 1 from Uruguay. The only other North American station noted during the night was WWZN on 1510 kHz.
Local sunrise propagation on April 15 were fairly good with a number of stations from Perú, Colombia and Ecuador audible.
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 |
|---|---|---|---|---|---|---|---|
| 10750 | 2005.04.05 | 1 | 1 | S07W54 | 0030 | HSX | area was 0020 at midnight |
| 10752 | 2005.04.12 | 8 | 5 | N01E30 | 0140 | ESO | classification was DSO at midnight, area 0090 |
| 10753 | 2005.04.13 | 5 | N12W32 | 0010 | BXO | spotless | |
| 10754 | 2005.04.14 | 7 | 5 | S08E38 | 0050 | CSO | classification was CAO at midnight, area 0030 |
| S533 | emerged on 2005.04.09 |
N19W80 | plage | ||||
| Total spot count: | 21 | 11 | |||||
| SSN: | 61 | 41 | |||||
| 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) |
| 2004.02 | 107.0 | 45.8 | 49.3 (-2.7) |
| 2004.03 | 112.0 | 49.1 | 47.1 (-2.2) |
| 2004.04 | 101.2 | 39.3 | 45.5 (-1.6) |
| 2004.05 | 99.8 | 41.5 | 43.8 (-1.7) |
| 2004.06 | 97.4 | 43.2 | 41.6 (-2.2) |
| 2004.07 | 119.1 | 51.1 | 40.2 (-1.4) |
| 2004.08 | 109.6 | 40.9 | 39.2 (-1.0) |
| 2004.09 | 103.1 | 27.7 | 37.5 (-1.7) |
| 2004.10 | 105.9 | 48.0 | (35.6 predicted, -1.9) |
| 2004.11 | 113.2 | 43.5 | (33.9 predicted, -1.7) |
| 2004.12 | 94.5 | 17.9 | (31.6 predicted, -2.3) |
| 2005.01 | 102.2 | 31.3 | (28.9 predicted, -2.7) |
| 2005.02 | 97.2 | 29.1 | (26.5 predicted, -2.4) |
| 2005.03 | 89.9 | 24.8 | (24.7 predicted, -1.8) |
| 2005.04 | 85.3 (1) | 22.1 (2) | (22.9 predicted, -1.8) |
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% less.
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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