Solar Terrestrial Activity Report

Last major update issued on September 13, 2005 at 03:25 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update September 3, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update September 3, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update September 3, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update September 2 , 2005)]

Recent activity

The geomagnetic field was active to major storm on September 12. Solar wind speed ranged between 593 and 1004 (all day average 843) km/sec. Another solar wind shock was observed at ACE near 06h UTC when the CME associated with the X2 flare late on September 10 arrived. Solar wind speed jumped to above 1000 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 118.0. The planetary A index was 66 (STAR Ap - based on the mean of three hour interval ap indices: 66.1).
Three hour interval K indices: 64665656 (planetary), 54654545 (Boulder).

The background x-ray flux is at the class C1 level.

At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was moderate. A total of 10 C and 4 M class events was recorded during the day.

Region 10808 lost some spots and penumbral area in the southeastern section. More significantly the negative polarity umbra embedded within the largest penumbra elongated. The magnetic delta structure in this penumbra is extremely strong and X class proton flares are possible as the flare potential has increased over the last day. Flares: C3.3 at 00:49, C2.0 at 02:48, M1.5 at 05:05, M1.3 at 07:01, M6.1/2F at 09:03, C1.1 at 15:37, C1.1 at 16:33, C1.2 at 16:38, C3.2 at 19:40, M1.5 at 20:09, C7.2 at 22:25, C4.7 at 23:00, C4.6 at 23:16 and C4.5 at 23:31 UTC.

Coronal mass ejections (CMEs)

September 10: A large, fast full halo CME was associated with the X2 long duration event in region 10808 late in the day.
September 11: At least a partial halo CME was associated with an M3 LDE in region 10808 just after noon.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report with the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent trans equatorial coronal hole (CH187) was in an Earth facing position on September 9-11.

Processed TRACE mosaic image on September 6, 2005. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to major storm on September 13 and unsettled to minor storm on September 14-15

Coronal holes (1)	Coronal mass ejections (2)	M and X class flares (3)

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) Material from a CME is likely to impact 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 useless. Propagation on long distance northeast-southwest paths is poor to very poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay with a very weak signal. Only a few other signals were audible, most of them from the São Paulo and Rio de Janeiro area in Brazil. Local sunrise propagation on September 12 was excellent towards Argentina with several stations on many frequencies below 1250 kHz. On 1170 kHz there were no European signals (very unusual) allowing two Argentine stations and one from Brazil to be heard.

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.