Last major update issued on April 15, 2004 at 03:30 UTC.
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[Solar cycles 21-23 (last update April 2, 2004)]
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[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 14. Solar wind speed ranged between 350 and 437 km/sec.
Solar flux measured at 20h UTC on 2.8 GHz was 95.2. The planetary A
index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 6.4).
Three hour interval K indices: 21103221 (planetary), 22201212 (Boulder).
The background x-ray flux is at the class B1 level.
At midnight there were 4 spotted regions on the visible disk. The solar flare activity level was very low. No C class events were recorded during the day.
Region 10591 merged with region S387 and a small magnetic delta structure formed in the main penumbra. The trailing spot
Region 10592 developed slowly and quietly.
New region 10593 emerged in the southeast quadrant to the south southwest of region 10592.
New region 10594 rotated further into view at the northeast limb.
April 12-14: 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
A very small coronal hole (CH89) in the southern hemisphere was in a possibly geoeffective position on April 12 and could cause a weak geomagnetic disturbance on April 15. A poorly defined coronal hole (CH90) in the northern hemisphere may have been in a geoeffective position on April 13-14.
Processed SOHO/EIT 284 image at 19:06 UTC on April 14. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to unsettled on April 15-17 with a chance of a few active intervals on April 16 and 17 due to a weak high speed stream from coronal hole CH90.
Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is fair to good. Propagation along long distance north-south paths is fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela) with a strong signal. Numerous North American (mostly east coast) stations are audible. During the sunrise opening on April 13 Jamaica was heard with a nice signal on 700 kHz.].
|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|
|10588||2004.04.01||1||S13W92||0040||HRX||rotated out of view|
area was 0100
classification was HSX
classification was HRX
at midnight, area 0010
|10594||2004.04.14||1||1||N15E69||0060||HSX||formerly region S390|
merged with region
10591 on April 14
|Total spot count:||19||21|
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||99.0 (1)||25.9 (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.