Solar Terrestrial Activity Report

Last major update issued on August 27, 2005 at 03:45 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 active on August 26. Solar wind speed ranged between 463 and 587 (all day average 520) km/sec slowly decreasing all day.

Solar flux measured at 20h UTC on 2.8 GHz was 93.2. The planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 11.4).
Three hour interval K indices: 34422222 (planetary), 34421221 (Boulder).

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

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 3 C 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. Flares: C1.3 at 03:12, C2.1 at 11:55 and C2.3 at 22:02 UTC
Region 10804 decayed and could soon become spotless.

Coronal mass ejections (CMEs)

August 24 and 26: No obvious partly or fully Earth directed CMEs were observed.
August 25: A 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 27-29.

Processed SOHO/EIT 284 image at 01:06 UTC on August 27. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on August 27-29. If the CME observed on August 25 reaches Earth, brief unsettled to minor storm conditions are possible on August 27. A high speed stream from CH184 could reach Earth during the latter half of August 30 and cause unsettled to minor storm conditions that day and on August 31.

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 poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay. Rádio Rural AM de Parelhas was heard again at 23h UTC. There were less stations during the night compared to the previous night.

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.