Solar Terrestrial Activity Report

Last major update issued on October 15, 2004 at 03:10 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, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update August 28, 2004)]
[Archived reports (last update October 10, 2004)]

Recent activity

The geomagnetic field was quiet to minor storm on October 14. Solar wind speed ranged between 463 and 545 km/sec under the influence of a high speed stream from coronal hole CH118. The coronal hole flow appeared to be coming to an end late in the day.

Solar flux measured at 20h UTC on 2.8 GHz was 90.7. The planetary A index was 27 (STAR Ap - based on the mean of three hour interval ap indices: 26.9). [Since October 13 USAF has delivered magnetometer data for sliding 3-hour intervals instead of the normal 1-hour data. One consequence of this, compared to previous data, is an apparent increase in 3-hour Ap indices. We will have to wait for more data to determine if data using the new methods diverge too much from previous data. For October 14 the data is somewhat curious as the same Ap value was reported for pairs of 3-hour data. For the 03-06 and 06-09 UTC intervals the Ap was 32, then 48 and 15 for the pairs of 09-12/12-15 h UTC and 15-18/18-21 h UTC. Additionally the Boulder and planetary K indices were equal.]
Three hour interval K indices: 34455332 (planetary), 34455332 (Boulder).

The background x-ray flux is at the class B1 level.

At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was low. A single C class event was recorded during the day.

Region 10682 developed slowly adding several new spots to the south and west of the main penumbra. The region is fairly complex with polarity intermixing observed in the areas where the new spots emerged. C flares are likely and there is a small chance of a minor M class flare. Flare: C1.7 at 03:49 UTC.

Coronal mass ejections (CMEs)

October 12-14: No obviously Earth directed CMEs 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 poorly defined coronal hole (CH119) in the southern hemisphere could rotate into a geoeffective position on October 14-15.

Processed SOHO/EIT 284 image at 19:06 UTC on October 14. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on October 15 and mostly quiet on October 16-17. On October 18 a weak recurrent coronal hole flow could cause occasional unsettled intervals. 

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 poor. Propagation along long distance north-south paths is fair. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela). On other frequencies propagation was best towards Newfoundland (560, 590, 620, 640, 750 and 930 kHz), Puerto Rico (580, 1430, 1480, 1600 and 1660 kHz), Venezuela (many stations, best was 660 Radio Anaco and 780 Radio Coro) and Colombia (760, 770 and 980 kHz). The only US station noted was on 1390, probably Heaven 13-90, WXTC Charleston SC.

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
10681 2004.10.12 4   N10W36 0020 AXX spotless
10682 2004.10.13 14 18 S13E50 0240 DSI beta-gamma
classification was DAI
at midnight, area 0200
Total spot count: 18 18
SSN: 38 28

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)
2003.08 122.1 72.7 60.0 (-1.7)
2003.09 112.2 48.7 59.5 (-0.5)
2003.10 151.7 65.5 58.2 (-1.3)
2003.11 140.8 67.3 56.7 (-1.5)
2003.12 114.9 46.5 54.8 (-1.9)
2004.01 114.1 37.3 52.0 (-2.8)
2004.02 107.0 45.8 49.3 (-2.7)
2004.03 112.0 49.1 47.1 (-2.2)
2004.04 101.2 39.3 (44.6 predicted, -2.5)
2004.05 99.8 41.5 (40.9 predicted, -3.7)
2004.06 97.4 43.2 (38.0 predicted, -2.9)
2004.07 119.1 51.0 (36.2 predicted, -1.8)
2004.08 109.6 40.9 (34.6 predicted, -1.6)
2004.09 103.1 27.7 (32.8 predicted, -1.6)
2004.10 89.4 (1) 12.1 (2) (30.5 predicted, -2.3)

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.

[DX-Listeners' Club]