Solar Terrestrial Activity Report

Last major update issued on September 1, 2004 at 02:40 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update August 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update August 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update August 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update August 28, 2004)]
[Archived reports (last update August 25, 2004)]

Recent activity

The geomagnetic field was unsettled to major storm on August 31. Solar wind speed ranged between 363 and 548 km/sec under the influence of a high speed stream from coronal hole CH111.

Solar flux measured at 20h UTC on 2.8 GHz was 88.1. The planetary A index was 28 (STAR Ap - based on the mean of three hour interval ap indices: 28.5).
Three hour interval K indices: 64543343 (planetary), 64443433 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight the visible disk was spotless. The solar flare activity level was moderate. A total of 1 M class event was recorded during the day.

Region 10663 rotated out of view at the northwest limb. Flares: M1.4 at 05:38 UTC. A weak type II radio sweep was associated with this event, as was a small CME off the central west limb.

Coronal mass ejections (CMEs)

August 29-31: No obviously 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 poorly defined coronal hole (CH111) in the northern hemisphere was in a geoeffective position on August 27-29.

Processed SOHO/EIT 284 image at 01:06 UTC on September 1. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to active on September 1 due to a coronal hole flow. Quiet to unsettled is likely on September 2-4.

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 very poor. Propagation along long distance north-south paths is poor to occasionally fair. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay with a very weak signal. Radio Vibración (Venezuela) and an unidentified station from Brazil were noted at times. On other frequencies some Brazilian stations were heard with Rádio Marajoara on 1130, Rádio Cristal on 1350 and Rádio Metropolitana on 930 kHz having the best signals. From the Caribbean both WDHP on 1620 and Harbour Light on 1400 kHz had weak signals. At local sunrise on August 31 several stations from Argentina and Paraguay had 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
10663 2004.08.19 1   N03W88 0050 HAX rotated out of view
10666 2004.08.29     N17E04     plage
S449 emerged on
    S14E24     plage
Total spot count: 1 0
SSN: 11 0

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)
2003.06 129.3 77.4 65.0 (-2.6)
2003.07 127.7 83.3 61.8 (-3.2)
2003.08 122.1 72.7 60.1 (-1.7)
2003.09 112.2 48.7 59.6 (-0.5)
2003.10 151.7 65.5 58.2 (-1.4)
2003.11 140.8 67.3 56.8 (-1.4)
2003.12 114.9 46.5 54.8 (-2.0)
2004.01 114.1 37.7 52.0 (-2.8)
2004.02 107.0 45.8 (49.1 predicted, -2.9)
2004.03 112.0 49.1 (46.5 predicted, -2.6)
2004.04 101.2 39.3 (44.3 predicted, -2.2)
2004.05 99.8 41.5 (41.0 predicted, -3.3)
2004.06 97.4 43.2 (38.2 predicted, -2.8)
2004.07 119.1 51.0 (36.3 predicted, -1.9)
2004.08 109.6 (1) 69.5 (2) (34.9 predicted, -1.4)

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]