Last major update issued on April 26, 2004 at 03:50 UTC.
[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update April 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update April 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update April 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2003 (last update January 16, 2004)]
[Archived reports (last update April 18, 2004)]
The geomagnetic field was quiet to active on April 25. Solar wind speed ranged between 463 and 582 km/sec.
Solar flux measured at 20h UTC on 2.8 GHz was 107.1. The planetary A
index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.6).
Three hour interval K indices: 13433322 (planetary), 13333332 (Boulder).
The background x-ray flux is at the class B1-B2 level.
At midnight there were 2 spotted regions on the visible disk. The solar flare activity level was moderate. A total of 5 C and 1 M class events was recorded during the day.
Region 10596 was quiet and stable.
Region 10599 developed further. The magnetic delta structure in a penumbra just east of the leading penumbra disappeared, however, the opposite polarities in this area are still quite close and further minor M class flares are possible. Flares: C9.0 at 01:44, M2.2/1N at 05:37, C1.2 at 09:09, C5.0 at 10:15, C1.4 at 14:40 and C2.6 at 16:06 UTC.
April 23-25: No fully or partly Earth directed CME observed due to no new LASCO images (SOHO is currently recovering from a failure).
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 (CH92) in the northern hemisphere was in a geoeffective position on April 23-25.
Processed SOHO/EIT 284 image at 01:05 UTC on April 22. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to active on April 26-28 with occasional minor storm intervals possible due to a high speed stream from coronal hole CH92.
Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor. Propagation along long distance north-south paths is poor to fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) and CPN Radio (Perú). Several stations from Newfoundland and the northeastern part of the USA were noted on other frequencies].
|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.
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
|Location at midnight||Area||Classification||Comment|
classification was CAO
at midnight, area 0180
|Total spot count:||25||28|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|2003.10||151.7||65.5||(58.0 predicted, -1.5)|
|2003.11||140.8||67.3||(55.9 predicted, -2.1)|
|2003.12||114.9||46.5||(53.3 predicted, -2.6)|
|2004.01||114.1||37.2||(49.1 predicted, -4.2)|
|2004.02||107.0||46.0||(44.5 predicted, -4.6)|
|2004.03||112.0||48.9||(41.7 predicted, -2.8)|
|2004.04||103.2 (1)||53.3 (2)||(39.6 predicted, -2.1)|
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.