Solar Terrestrial Activity Report

Last major update issued on August 26, 2005 at 04:25 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, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update August 2, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update August 2, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update August 13, 2005)]

Recent activity

The geomagnetic field was quiet to minor storm on August 25. Solar wind speed ranged between 573 and 777 (all day average 667) km/sec, at first due to CME effects, then a high speed stream from CH183.

Solar flux measured at 20h UTC on 2.8 GHz was 92.4. The planetary A index was 24 (STAR Ap - based on the mean of three hour interval ap indices: 24.4).
Three hour interval K indices: 54334532 (planetary), 54334422 (Boulder).

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

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was high. A total of 1 M class events was recorded during the day.

Region 10800 decayed slowly and quietly.
Region  10803 has a magnetic delta structure in the largest penumbra in the southeastern section. Polarity intermixing is evident in other parts of the region as well. Flare: impulsive major M6.4/1N at 04:40 UTC. This event was associated with a fast full halo CME.
New region 10804 emerged in the northeast quadrant on August 24 and was numbered the next day by NOAA/SEC.

Coronal mass ejections (CMEs)

August 23: At least a partial halo CME was observed after the M2 LDE in region S583 during the afternoon.
August 24: No obvious partly or fully Earth directed CMEs were observed.
August 25: A very fast and wide full halo CME was observed after the major M6 event in region 10803. This CME was not as dense as we often observe and it was difficult to track the expansion front over the western limbs.

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 coronal hole (CH184) in the southern hemisphere will likely rotate to an Earth facing position on August 28-29.

Processed SOHO/EIT 284 image at 01:06 UTC on August 26. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on August 26. The CME observed early on August 25 could reach Earth on August 27 and cause fairly brief unsettled to minor storm conditions. Quiet to unsettled is likely on August 28-29.

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 on long distance northeast-southwest paths is fair to poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay. On other frequencies mostly stations from Argentina (710, 870, 850, 1030, 1070, 1190 kHz), Uruguay (930, 970, 1010, 1050 kHz) and Brazil were audible. From North America only WWZN on 1510 and CJYQ on 930 kHz could be heard with weak 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.

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% 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.