Solar Terrestrial Activity Report

Last major update issued on July 29, 2006 at 05:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update July 19, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update July 19, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 19, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update July 9, 2006)]

Recent activity

The geomagnetic field was quiet to major storm on July 28. Solar wind speed ranged between 550 and 750 km/s (all day average 613 km/s - increasing 232 km/s over the previous day) under the influence of a high speed stream from CH233.

Solar flux measured at 20h UTC on 2.8 GHz was 72.6. The planetary A index was 29 (STAR Ap - based on the mean of three hour interval ap indices: 29.1).
Three hour interval K indices: 66432212 (planetary), 65433312 (Boulder).

The background x-ray flux is at the class A2 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.

Region 10901 was quiet and stable.

Coronal mass ejections (CMEs)

July 26-28: 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

A well defined recurrent trans equatorial coronal hole (CH234) will reach an Earth facing location on July 28-30.

Processed SOHO/EIT 284 image at 01:06 UTC on July 29. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on July 29 due to weakening coronal hole effects. Mostly quiet conditions are expected for July 30. On July 31 a strong high speed stream from CH234 can cause unsettled to major storm conditions lasting until August 1.

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. Stations from Brazil began fading in as early as 21:30 UTC and 1470 Radio Cristal del Uruguay was noted one hour later. Propagation was basically uninteresting until near dawn when the most common Newfoundland stations were heard. Unidentified US stations were audible on 1680 and 1700 kHz at LSR and the Venezuela was strong on 1290, 1390 and 1470 kHz. After LSR most of the stations heard were from Brazil (for instance two stations on 920 kHz) and Argentina. The post-dawn long distance propagation lasted only 30 minutes.

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.