Last major update issued on April 26, 2006 at 02:45 UTC.
geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update April 1, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update April 1, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update April 1, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update April 3, 2006)]
The geomagnetic field was inactive to unsettled on April 25. Solar wind speed ranged between 344 and 384 (all day average 359) km/sec.
Solar flux measured at 20h UTC on 2.8 GHz was 95.1. The planetary A index
was 5 (STAR Ap - based on the mean of three hour interval ap
Three hour interval K indices: 30002221 (planetary), 21112111 (Boulder).
The background x-ray flux is at the class B1 level.
At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was low. A single C class event was recorded during the day.
Region 10875 developed slowly and remains capable
of producing M class flares. There is a magnetic delta structure in the northeastern part of the main penumbra. Flare:
long duration C1.3 peaking at 07:26 UTC. This was associated with a CME over the
Region 10876 was quiet. Magnetically the region has negative polarity areas in the east and west with a weaker positive polarity area in between.
Spotted regions not numbered by NOAA/SEC:
[S646] This region emerged near the southeast limb on April 25. Location at midnight: S05E65.
April 23-25: 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
No obvious coronal holes are currently in or approaching Earth facing locations.
Processed SOHO/EIT 284 image at 19:06 UTC on April 25. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be mostly quiet on April 26-28.
|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. Dominant stations tonight: Radio Vibración (Venezuela) and Radio Cristal del Uruguay. Propagation favored Argentina (good signals on 1030 and 1190 kHz) and Uruguay. A few stations from North America were audible after 02:30 UTC and, as usual, 1510 WWZN had the best signal.
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 DKC at midnight
|Total spot count:||13||31|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|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||86.7 (1)||44.6 (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.