Solar Terrestrial Activity Report

Last major update issued on June 8, 2006 at 03:50 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update June 7, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update June 7, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update June 7, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update June 5, 2006)]

Recent activity

The geomagnetic field was unsettled to active on June 7. Solar wind speed ranged between 548 and 719 km/s (all day average 607 km/s - increasing 184 km/s over the previous day) under the influence of a high speed stream from CH227.

Solar flux measured at 20h UTC on 2.8 GHz was 82.7. The planetary A index was 24 (STAR Ap - based on the mean of three hour interval ap indices: 24.1).
Three hour interval K indices: 44433344 (planetary), 44443334 (Boulder).

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

At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10892 developed significantly as new positive polarity flux emerged east of the leading penumbra. A weak magnetic delta structure has formed in this developing area. C flares are possible and there is a minor chance of a small M class flare.
Region 10893 matured with the leading penumbra gaining area.

Coronal mass ejections (CMEs)

June 5-7: No partly or fully Earth directed CMEs were observed in incomplete LASCO imagery.

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 (CH227) in the northern hemisphere was in an Earth facing position on June 4-6.

Processed SOHO/EIT 284 image at 19:06 UTC on May 26. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on June 8-9 and mostly quiet on June 10-11.

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) Effects from a CME are likely to be observed at 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 poor. Propagation on long distance northeast-southwest paths is fair to good. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Radio Cristal del Uruguay was again the best signal this night. On other frequencies propagation was best towards Brazil (1350 kHz was a good frequency with no less than 3 stations competing for dominance) and Uruguay until 30 minutes after LSR when stations from Argentina (950 "La 950 AM", Buenos Aires and 1350 RBA had the best signals then) became stronger and the others weakened.

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.