Solar Terrestrial Activity Report

Last major update issued on July 8, 2006 at 04:35 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 quiet to unsettled on July 7. Solar wind speed ranged between 461 and 561 km/s (all day average 518 km/s - decreasing 49 km/s from the previous day) under the declining influence of a high speed stream from CH230.

Solar flux measured at 20h UTC on 2.8 GHz was 79.9. The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.1).
Three hour interval K indices: 22112231 (planetary), 22221221 (Boulder).

The background x-ray flux is at the class A5 level.

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

Region 10898 has a weak magnetic delta structure in the western part of the main penumbra. C flares are possible and there is a small chance of another M class flare. Flares:C5.2 at 12:04 and C2.3 at 21:47 UTC.
Region 10899 was mostly unchanged and quiet.

Coronal mass ejections (CMEs)

July 5 and 7: No partly or fully Earth directed CMEs were detected in LASCO imagery.
July 6: A large full halo CME was observed after the M2 event in region 10898. While the core of this CME is not likely to reach Earth, some of the ejected material is heading our way and could reach Earth late on July 8 or sometine on July 9.

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 coronal hole (CH231) in the southern hemisphere will rotate into an Earth facing location on July 7-9.

Processed SOHO/EIT 284 image at 19:06 UTC on July 7. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet on July 8. CME effects are possible from late on July 8 until July 10 with unsettled to minor storm conditions likely. A high speed stream from CH231 will probable dominate the solar wind on July 10-12 and cause quiet to minor storm conditions.

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 very poor. Propagation on long distance northeast-southwest paths is poor to fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Radio Cristal del Uruguay and Radio Vibración had the best signals. On other frequencies mainly stations from Brazil and Argentina were audible, although most had weak signals.

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.