Solar Terrestrial Activity Report

Last update issued on September 29, 2003 at 03:40 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update September 1, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update September 1, 2003)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update September 1, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update July 23, 2003)]
[Archived reports (last update September 16, 2003)]

Recent activity

The geomagnetic field was very quiet to slightly unsettled on September 28. Solar wind speed ranged between 346 and 441 km/sec. 

Solar flux measured at 20h UTC on 2.8 GHz was 137.0 (slightly enhanced by a long duration event). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 7.6).
Three hour interval K indices: 21232221 (planetary), 01122111 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight there were 7 spotted regions on the visible disk. Solar flare activity was low. A total of 4 C class events was recorded during the day. A C1.3 long duration event peaking at 07:50 UTC was optically uncorrelated.

Region 10464 decayed further in the intermediate spot section. Slow decay was observed in the leading spot section as well, while slow development occurred in the trailing spots. There is still a magnetic delta structure in a penumbra just southwest of the largest trailing penumbra. An M class flare remains a possibility. Flares: C2.3 at 14:28, C6.8 long duration event peaking at 15:58 and C1.6 at 20:37 UTC.
Region 10465 decayed and had a couple of tiny spots left at midnight..
Region 10466 decayed slowly and quietly.
Region 10467 decayed and could become spotless today or tomorrow.
Region 10469 decayed quickly and could become spotless tomorrow if the current rate of decay persists.

Spotted regions not numbered by NOAA/SEC:
[S263] A new region emerged in the southeast quadrant on September 28. Location at midnight: S14E44.
[S264] A new region is rotating into view at the southeast limb: Location at midnight: S07E84.

Coronal mass ejections (CMEs)

September 26-27: No potentially geoeffective CMEs observed.

September 28: CMEs were observed mainly off the north and south poles. A fainter extension over the east limb indicates that one of the CMEs may have been a partial halo CME. With no EIT images available it is difficult to determine if the CMEs had frontside or backside sources.

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 coronal hole (CH60) in the northern hemisphere was in a geoeffective position on September 26-28.

Processed SOHO/EIT 284 image at 19:06 UTC on September 25. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet until the latter half of September 29 when a high speed stream from coronal hole CH60 is likely to cause unsettled to active conditions until October 1.

Long distance low frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor. Propagation along north-south paths is poor to fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) and Radio Cristal del Uruguay].

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.
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.

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.

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% less.

This report has been prepared by Jan Alvestad. It is based partly on my own observations and analysis, and partly on data from sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.