Solar Terrestrial Activity Report

Last major update issued on May 24, 2006 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 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 May 3, 2006)]

Recent activity

The geomagnetic field was quiet to unsettled on May 23. Solar wind speed ranged between 370 and 477 (all day average 431) km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 84.2. The planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.0).
Three hour interval K indices: 33211121 (planetary), 33211101 (Boulder).

The background x-ray flux is at the class A4 level.

At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10885 developed further and may be capable of C class flaring.
New region 10886 emerged in the northeast quadrant on May 22 and was numbered the next day by SEC. The region developed on May 23.

Coronal mass ejections (CMEs)

May 21-23: No partly or fully Earth directed CMEs were observed in LASCO imagery.

Coronal holes

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 positions.

Processed SOHO/EIT 284 image at 13:06 UTC on May 23. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet on May 24-27.

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.

Propagation

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. Radio Vibración (Venezuela) and Radio Cristal del Uruguay had occasionally good signals. Most of the other stations audible were from Argentina (the Buenos Aires stations on 950 and 1190 were fairly strong) and Uruguay (930 and 1410 kHz to mention the best signals).

Active solar regions (Recent map)

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
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
10884 2006.05.19 4   S13W05 0020 DSO spotless
10885 2006.05.20 11 14 S12E03 0060 DSI classification was DAI at midnight, area 0090
10886 2006.05.23 3 5 N08E46 0030 CRO formerly region S655
classification was DAO at midnight, area 0060
Total spot count: 18 19  
SSN: 48 39  

Monthly solar cycle data

Month Average solar
flux at Earth
International sunspot number Smoothed sunspot number
2000.04 184.2 125.5 120.8
cycle 23 sunspot max.
2000.07 202.3 170.1 119.8
2001.12 235.1 132.2 114.6 (-0.9)
2005.02 97.2 29.2 33.9 (-0.7)
2005.03 89.9 24.5 33.5 (-0.4)
2005.04 86.0 24.2 31.6 (-1.9)
2005.05 99.3 42.7 28.9 (-2.7)
2005.06 93.7 39.3 28.8 (-0.1)
2005.07 96.4 40.1 29.1 (+0.3)
2005.08 90.5 36.4 27.4 (-1.7)
2005.09 91.1 21.9 25.8 (-1.6)
2005.10 77.0 8.5 25.5 (-0.3)
2005.11 86.3 18.0 (24.5 predicted, -1.0)
2005.12 90.7 41.2 (21.8 predicted, -2.7)
2006.01 83.4 15.4 (18.7 predicted, -3.1)
2006.02 76.5 4.7 (15.6 predicted, -3.1)
2006.03 75.4 10.8 (13.4 predicted, -2.2)
2006.04 89.0 30.2 (12.7 predicted, -0.7)
2006.05 80.5 (1) 25.9 (2) (12.2 predicted, -0.5)

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.


[DX-Listeners' Club]