Solar Terrestrial Activity Report

Last major update issued on October 5, 2005 at 03:25 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 inactive to very quiet on October 4. Solar wind speed ranged between 289 and 370 (all day average 334) km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 82.7. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.6).
Three hour interval K indices: 11001111 (planetary), 12102210 (Boulder).

The background x-ray flux is at the class B3 level.

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

New region 10813 emerged on October 3 and was numbered by NOAA/SEC the next day. This region has developed quickly and is currently compact with mixed polarities. There is very little separation between the opposite polarities in the northern part of the region and a magnetic delta structure could be forming. M class flares are possible.

Coronal mass ejections (CMEs)

October 2-4: No obvious fully or partly Earth directed CMEs were observed.

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 trans equatorial coronal hole (CH191) will rotate to an Earth facing position on October 5-7.

Processed SOHO/EIT 284 image at 01:06 UTC on October 5. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be mostly quiet October 5-7, some unsettled intervals are possible on October 5 due to effects from CH190. A high speed stream from CH191 will likely arrive on October 8 and cause quiet to active conditions until October 10.

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 good to very good. Propagation on long distance northeast-southwest paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: WLAM Lewiston ME. The best signals were from the usual Newfoundland stations, most of the 50 kW New York stations, and Cuba on several frequencies. WIOD Miami on 610 was good. Some stations from the Great Lakes and further south were audible as well.

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
10812 2005.09.23     S03W72     plage
10813 2005.10.04 5 26 S06E30 0060 DSO beta-gamma
formerly region S597
classification was DAC at midnight, area 0170
location: S08E30
S595 2005.09.30     N12W67     plage
S596 2005.10.02     S10W68     plage
Total spot count: 5 26  
SSN: 15 36  

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 76.0 (1) 0.5 (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]