Last major update issued on April 17, 2005 at 05:40 UTC.
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 unsettled on April 16. Solar wind speed ranged between 401 and 484 km/sec.
Solar flux measured at 20h UTC on 2.8 GHz was 82.9. The planetary
index was 7 (STAR Ap - based on the mean of three hour interval ap
Three hour interval K indices: 32112222 (planetary), 32112322 (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. Sub flare activity increased as a fairly active region is approaching the southeastern limb. This region produced a C flare early on April 17.
Region 10750 decayed slowly and quietly, the region could become spotless today.
Region 10752 decayed further and lost all negative polarity spots.
Region 10754 decayed further and could become spotless today if the current rate of decay is sustained.
April 14-16: No obvious fully or partly Earth directed CMEs were observed.
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 was in an Earth facing position on April 15-17. A coronal hole (CH159) in the northern hemisphere will likely be in an Earth facing position on April 19.
Processed SOHO/EIT 284 image at 01:06 UTC on April 17. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be mostly quiet on April 17 and the first half of April 18. Effects from CH158 could reach Earth on April 18 and cause unsettled to active conditions until April 20.
|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. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela). Some stations from Venezuela and Puerto Rico were audible at local sunrise, however, most of the stations noted then were from North America. WBZ on 1030 and WWZN on 1510 kHz had the best signals.
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|
|10750||2005.04.05||1||1||S08W66||0020||HSX||classification was AXX at midnight, area 0010|
|10752||2005.04.12||5||4||N02E14||0090||DSO||classification was HAX at midnight|
|10753||2005.04.13||1||N12W45||0010||AXX||spotless for the second consecutive day|
|10754||2005.04.14||5||4||S08E23||0040||DSO||classification was CSO at midnight, area 0020|
|Total spot count:||12||9|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|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||85.2 (1)||23.8 (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.