Solar Terrestrial Activity Report

Last major update issued on July 13, 2007 at 01:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-23 (last update June 3, 2007)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update June 3, 2007)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update June 3, 2007)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update July 1, 2007)]

Recent activity

The geomagnetic field was quiet to unsettled on July 12. Solar wind speed ranged between 448 and 568 km/s (average speed was 532 km/s, decreasing 12 km/s from the previous day) under the diminishing influence of a high speed stream from CH277.

Solar flux measured at 20h UTC on 2.8 GHz was 76.9. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 7.9). Three hour interval K indices: 23301222 (planetary), 23311112 (Boulder).

The background x-ray flux is at the class A1 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 10963 was mostly unchanged and could produce C flares.

Spotted regions not numbered by NOAA/SEC:
[S705] This region emerged in the northwest quadrant on July 12. Location at midnight: N04W13.

Coronal mass ejections (CMEs)

July 10-12: No obvious fully or partly Earth directed CMEs were observed.

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

The northwesternmost extension of a recurrent coronal hole (CH277) in the southern hemisphere was in an Earth facing position on July 6-7. The northeasternmost extension of the same coronal hole structure may have been in an Earth facing position on July 9-10.

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Processed SOHO/EIT 195 image at 14:36 UTC on July 12. The darkest areas on the solar disk are likely coronal holes.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is very poor. Propagation on long distance northeast-southwest paths is fair to good.

Monitoring remarks from a location near N58E06: July 13: At 01h UTC 1470 kHz had several stations with Radio Cristal del Uruguay on top, at times with a strong signal. A few other stations, like 950 Belgrano, were audible with fair signals. No signals from Brazil were noted at this time.

Forecast

The geomagnetic field is expected to be quiet to unsettled on July 13-14 and quiet on July 15-17.

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.

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.