Last major update issued on April 18, 2004 at 03:45 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 5, 2004)]
The geomagnetic field was quiet to unsettled on April 17. Solar wind speed ranged between 377 and 459 km/sec.
Solar flux measured at 20h UTC on 2.8 GHz was 98.2. The planetary A
index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.4).
Three hour interval K indices: 23212332 (planetary), 24212222 (Boulder).
The background x-ray flux is at the class B1 level.
At midnight there were 7 spotted regions on the visible disk. The solar flare activity level was low. A single C class event was recorded during the day.
Region 10591 decayed quickly and will soon rotate to the southwest limb.
Region 10592 was quiet and stable.
Region 10593 reemerged with several small spots.
Region 10594 decayed losing some of its penumbral area.
Region 10595 decayed and could soon become spotless.
Spotted regions not numbered by NOAA/SEC:
[S391] This region emerged to the north of region 10595 late on April 16 and developed moderately quickly on April 17.
[S392] This region was barely visible at the southeast limb near midnight on April 16 and rotated fully into view on April 17. The region has a leading negative polarity area, then a wider positive polarity area and then a negative polarity at the southeastern corner. Further C class flares are possible. Flare: C1.8 at 11:42 UTC.
April 15-17: No fully or partly Earth directed CME 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
No obvious coronal holes are currently approaching geoeffective positions.
Processed SOHO/EIT 284 image at 19:05 UTC on April 17. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to unsettled on April 18-22.
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 station tonight: Radio Vibración (Venezuela). Several of the usual Newfoundland stations were noted, as was WWZN Boston on 1510 kHz with a fair signal].
|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 CSO
at midnight, area 0030
classification was HRX
|Total spot count:||15||35|
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||98.7 (1)||31.5 (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.