Solar Terrestrial Activity Report

Last major update issued on July 4, 2006 at 04:20 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 inactive to quiet on July 3. Solar wind speed ranged between 275 and 348 km/s (all day average 300 km/s - decreasing 61 km/s from the previous day).

Solar flux measured at 20h UTC on 2.8 GHz was 85.9. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.8).
Three hour interval K indices: 10110212 (planetary), 00121002 (Boulder).

The background x-ray flux is at the class B1 level.

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

Region 10897 decayed slowly and could become spotless today.
Region 10898 has patches of positive polarity surrounding the large negative polarity spot. C flares are possible. Flare: C1.2 long duration event peaking at 23:04 UTC.

Coronal mass ejections (CMEs)

July 1-3: No partly or fully Earth directed CMEs were detected in incomplete 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 recurrent trans equatorial coronal hole (CH230) was in an Earth facing position on July 1-3.

Processed SOHO/EIT 284 image at 01:06 UTC on July 4. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be to range from quiet to minor storm July 4-6 due to a high speed stream from CH230. Mostly quiet is likely on July 7-8

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 poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Radio Cristal del Uruguay had a weak to occasionally fair signal. While propagation was generally poor, the best reception was noted from stations along the east coast of the Buenos Aires province. Both 1030 Radio del Plata and 1270 Radio Provincia had strong signals while a more interesting unidentified station from Argentina was noted on 1400 kHz.

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.