Solar Terrestrial Activity Report

Last update issued on August 24, 2003 at 04:15 UTC. 

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update August 18, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update August 18, 2003)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update August 18, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update July 23, 2003)]
[Archived reports (last update August 1, 2003)]

Recent activity

The geomagnetic field was unsettled to severe storm on August 23. Solar wind speed ranged between 673 and 887 km/sec under the influence of a high speed stream from coronal hole CH52.

Solar flux measured at 23h UTC on 2.8 GHz was 123.2. The planetary A index was 44 (STAR Ap - based on the mean of three hour interval ap indices: 44.9).
Three hour interval K indices: 45755344 (planetary), 56555434 (Boulder).

The background x-ray flux is at the class B2-B3 level.

At midnight there were 6 spotted regions on the visible disk. Solar flare activity was very low.

Region 10436 developed slowly in the intermediate spot section and may be capable of producing an isolated minor M class flare.
Region 10439 decayed and could become spotless today.
Region 10440 decayed slowly and quietly.
Region 10441 developed slowly and was quiet.
Region 10442 was quiet and stable.
New region 10444 emerged in the northeast quadrant.

Coronal mass ejections (CMEs)

August 21-23: No potentially geoeffective 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 large coronal hole (CH52) in the northern hemisphere was in a geoeffective position on August 17-21. A coronal hole (CH53) in the southern hemisphere does not currently appear likely to reach geoeffective positions.

Processed GOES SXI coronal structure image at 00:00 UTC on August 23. Base SXI image courtesy of NOAA/SEC. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to minor storm on August 24, unsettled to active on August 25 and quiet to unsettled on August 26-28.

Long distance low frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is very poor to useless. Propagation along north-south paths is fair to poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay]

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.
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.

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.

Monthly solar cycle data

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 sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.