Solar Terrestrial Activity Report

Last major update issued on July 9, 2007 at 04:15 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 on July 8. Solar wind speed ranged between 346 and 446 km/s (average speed was 381 km/s, decreasing 67 km/s from the previous day).

Solar flux measured at 20h UTC on 2.8 GHz was 75.1. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.4). Three hour interval K indices: 12111111 (planetary), 11201112 (Boulder).

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

At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was low. A total of 3 C class events was recorded during the day.

Region 10963 developed slowly. The region has some magnetic complexity with a central positive polarity area and bordering negative polarity areas to the east and west. Further C class flare activity is likely and there is a minor chance of a small M class event. Flares: C1.1 at 13:27, C1.0 at 15:52 and C1.8 at 16:48 UTC.

Coronal mass ejections (CMEs)

July 6-8: No obvious fully or partially Earth directed CMEs were observed 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

The nortwesternmost 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 could rotate into an Earth facing position on July 9-10.

.

Processed STEREO 195 image at 23:35 UTC on July 8. 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 poor. Propagation on long distance northeast-southwest paths is poor.

Monitoring remarks from a location near N58E06: July 9: Perú was noted on 1470 and 1499.92 kHz at LSR, otherwise only a few stations from South America were audible.

Forecast

The geomagnetic field is expected to be quiet on July 9. CH277 could cause some unsettled and active intervals late on July 9 and on July 10 and perhaps again on July 13.

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.