Solar Terrestrial Activity Report

Last major update issued on August 31, 2004 at 04:20 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 quiet to minor storm on August 30. Solar wind speed ranged between 345 and 439 km/sec. A moderately strong disturbance began after 05h UTC when the interplanetary magnetic field swung strongly southwards and remained strongly southwards until the evening. The CME front passage observed at 09:20 UTC on August 29 was initially associated with a northwards IMF and did not cause any significant disturbance that day. The source of the CME is uncertain, however, based on the low solar wind speed, the most likely day of origin at the sun was on August 25. Another disturbance arrived at about 21h UTC and solar wind speeds increased again from a low near 350 km/sec at 16h UTC to near 450 km/sec early on August 31. It is not yet certain if this second disturbance is the arrival of a coronal hole flow.

Solar flux measured at 20h UTC on 2.8 GHz was 89.9. The planetary A index was 34 (STAR Ap - based on the mean of three hour interval ap indices: 35.0).
Three hour interval K indices: 32555445 (planetary), 32444435 (Boulder).

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

At midnight there were 2 spotted regions on the visible disk. The solar flare activity level was low. A total of 3 C class events was recorded during the day.

Region 10663 developed quickly early in the day with negative polarity spots emerging inside the leading positive polarity area. There is quite a bit of hot plage in and near this region. Flares: C2.4 at 03:11, C1.0 at 18:18 and a long duration C1.4 event peaking at 21:25 UTC.

Spotted regions not numbered by NOAA/SEC:
[S449] This region emerged early on August 30 in the southeast quadrant, then began to decay and had only a couple of tiny spots left by midnight.

Coronal mass ejections (CMEs)

August 28-30: 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 August 31. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to major storm on August 31 and quiet to active on September 1 due to a coronal hole flow. Quiet to unsettled is likely on September 2-3.

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. 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.

Propagation

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. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay with a very weak signal. On other frequencies a few of the most usual stations from Brazil could be heard, 740 and 980 kHz had the best signals. From North America WWZN on 1510 had a very poor signal as the only observed station.

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.

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 some of these solar data sources. All time references are to the UTC day. Comments and suggestions are always welcome.