Solar Terrestrial Activity Report

Last major update issued on September 1, 2005 at 05:10 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 major storm on August 31. Solar wind speed ranged between 332 and 550 (all day average 402) km/sec under the increasing influence of a high speed stream from CH184.

Solar flux measured at 20h UTC on 2.8 GHz was 84.0. The planetary A index was 36 (STAR Ap - based on the mean of three hour interval ap indices: 36.0).
Three hour interval K indices: 22235665 (planetary), 23334554 (Boulder).

The background x-ray flux is at the class A6 level.

At midnight there were 4 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 2 C class event was recorded during the day.

Region 10803 decayed and became spotless. Flare: C2.0 long duration event peaking at 11:51 UTC. This event was associated with a full halo CME.
Region 10805 decayed slowly and was quiet.
Region 10806 decayed quickly and quietly.

Spotted regions not numbered by NOAA/SEC:
[S588] This region emerged in the northeast quadrant on August 31 and had a single small spot at midnight. Location: N12E29.
[S589] A new region emerged in the southwest quadrant on August 31. A tiny spot was visible at midnight. The inversion line runs east-west instead of the usual north-south. Location: S23W46.

Coronal mass ejections (CMEs)

August 29-30: No obvious partly or fully Earth directed CMEs were observed. A large full halo CME was observed from a source behind the southwest limb on August 29. A minor increase in the above 10 MeV proton flux was probably caused by this event as well.
August 31: A full halo CME was observed in LASCO images following the long duration C2 event in region 10803 at noon. An extremely bright "mother-of-all-CMEs" full halo CME was observed in LASCO C3 images beginning at 23:18 UTC. Its source was backsided, about 6 days behind the southwest limb.

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 recurrent coronal hole (CH184) in the southern hemisphere was in an Earth facing position on August 27-28. A small recurrent coronal hole (CH185) in the northern hemisphere will likely rotate to an Earth facing position on September 1-2. CH185 did not cause any obvious disturbance during the previous rotation.

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

Forecast

The geomagnetic field is expected to be quiet to minor storm on September 1 due to a high speed stream from CH184. Quiet to unsettled is likely on September 2. The halo CME observed at noon on August 31 could reach Earth early on September 3 and cause unsettled to major storm conditions.

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. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and LT28 Rafaela Argentina. Stations from Argentina and southern Brazil were heard on a number of frequencies.

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.