Solar Terrestrial Activity Report

Last major update issued on August 10, 2006 at 04:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update August 6, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update August 6, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update August 6, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update August 6, 2006)]

Recent activity

The geomagnetic field was quiet to unsettled on August 9. Solar wind speed ranged between 457 and 561 km/s (all day average 517 km/s - decreasing 61 km/s from the previous day) under the decreasing influence of a high speed stream from CH235.

Solar flux measured at 20h UTC on 2.8 GHz was 74.1. The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.1).
Three hour interval K indices: 23132113 (planetary), 23242113 (Boulder).

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

At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

New region 10904 rotated into view at the southeast limb. Polarities are poorly separated and C flares are possible.

Coronal mass ejections (CMEs)

August 7-9: No partly or fully Earth directed CMEs were detected in LASCO imagery.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

No obvious coronal holes are currently in or approaching Earth facing positions.

Processed SOHO/EIT 284 image at 01:06 UTC on August 10. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on August 10 and quiet on August 11-13.

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. Both 590 VOCM and 930 CJYQ had decent signals at 02h UTC, other than that only a few stations from the easternmost parts of North America were heard with weak audio. Propagation on long distance northeast-southwest paths is very good, especially to Uruguay. 850 Carve, 930 Montecarlo, 1090 Imparcial, 1130 Nacional, 1410 AM Libre and 1470 Cristal were all heard with excellent signals. 1510 San Carlos was strong as well. A few stations from Brazil had amazing signals, one example being 760 Uirapurú (although with occasional strong interference from Emisora Atlántica).

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.