Solar Terrestrial Activity Report

Last major update issued on October 23, 2005 at 02:50 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update October 2, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 2, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 2, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update October 2, 2005)]

Recent activity

The geomagnetic field was quiet to active on October 22. Solar wind speed ranged between 337 and 390 (all day average 362) km/sec under the influence of a weak, low speed coronal hole stream.

Solar flux measured at 20h UTC on 2.8 GHz was 74.7. The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.1).
Three hour interval K indices: 42101011 (planetary), 43201221 (Boulder).

The background x-ray flux is below the class A1 level.

At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Spotted regions not numbered by NOAA/SEC:
[S599] This region emerged in the northeast quadrant on October 22. Location at midnight: N05E36

Coronal mass ejections (CMEs)

October 20-22: No obvious fully or partly Earth directed CMEs were observed. A full halo CME with an origin on the back side of the sun was observed beginning at 10:24 UTC.

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

A recurrent coronal hole (CH193) in the southern hemisphere was in an Earth facing position on October 20-21. CH193 did not cause any disturbance during the previous rotation. Recurrent trans equatorial coronal hole CH194 will rotate to an Earth facing position on October 22-23.

Processed SOHO/EIT 284 image at 19:06 UTC on October 23. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to active on October 23-26 due to coronal hole effects (multiple coronal holes).

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)
Coronal hole indicator CME indicator M and X class flare indicator

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 excellent. Propagation on long distance northeast-southwest paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: WWNN Boca Raton FL and WLAM Lewiston ME. A large number of US and Canadian stations were heard on other frequencies, from locations at the Atlantic coast to near the Pacific coastline. 1510 kHz had WWZN Boston, WLAC Nashville and KCUV with mostly strong signals. Several daytimers were noted during the evening with WIZZ 1520 and WFIF 1500 both heard with weak to fair 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
Location at midnight Area Classification Comment
10815 2005.10.14 3   N07W32 0020 CAO spotless
10816 2005.10.19     S14W68     plage
S599 2005.10.22   1 S08E36 0010 AXX  
Total spot count: 3 1  
SSN: 13 11  

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)
2004.08 109.6 40.9 39.2 (-1.0)
2004.09 103.1 27.7 37.5 (-1.7)
2004.10 105.9 48.0 35.9 (-1.6)
2004.11 113.2 43.5 35.3 (-0.6)
2004.12 94.5 17.9 35.2 (-0.1)
2005.01 102.2 31.3 34.6 (-0.6)
2005.02 97.2 29.2 33.9 (-0.7)
2005.03 89.9 24.5 33.5 (-0.4)
2005.04 86.0 24.4 (31.9 predicted, -1.6)
2005.05 99.3 42.6 (29.4 predicted, -2.5)
2005.06 93.7 39.6 (28.1 predicted, -1.3)
2005.07 96.4 39.9 (26.9 predicted, -1.2)
2005.08 90.5 36.4 (25.0 predicted, -1.9)
2005.09 91.1 22.1 (23.0 predicted, -2.0)
2005.10 78.3 (1) 10.9 (2) (21.0 predicted, -2.0)

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]