Solar Terrestrial Activity Report

Last major update issued on July 15, 2006 at 03:10 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 July 9, 2006)]

Recent activity

The geomagnetic field was quiet to active on July 14. Solar wind speed ranged between 380 and 540 km/s (all day average 442 km/s - decreasing 34 km/s from the previous day). A moderately high speed stream from an unidentified coronal hole caused a disturbance from 09h UTC and for the remainder of the day.

Solar flux measured at 20h UTC on 2.8 GHz was 70.9. The planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 13.8).
Three hour interval K indices: 11023443 (planetary), 01023431 (Boulder).

The background x-ray flux is below the class A1 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 10900 emerged quickly early in the day. Slow decay was noted during the evening.

Coronal mass ejections (CMEs)

July 12-14: 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 locations.

Processed SOHO/EIT 284 image at 01:06 UTC on July 15. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on July 15 and quiet on July 16-20.

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 very poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Radio Cristal del Uruguay had a weak signal and was only occasionally audible tonight. Only a few other stations from South America had useable signals. From North America I noted weak Newfoundland stations on 560, 590, 640, 710, 750, 800 and 930 kHz, while NB/NS stations were weakly audible on 780, 920 and 950 kHz. 1130 WBBR and 1510 WWZN were the only US stations.

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.