Solar Terrestrial Activity Report

Last major update issued on October 28, 2004 at 03:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update October 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update August 28, 2004)]
[Archived reports (last update October 18, 2004)]

Recent activity

The geomagnetic field was inactive to quiet on October 27. Solar wind speed ranged between 354 and 424 km/sec. A weak disturbance, source unknown, began at noon.

Solar flux measured at 17h UTC on 2.8 GHz was 129.5. The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.3).
Three hour interval K indices: 00011212 (planetary), 00102212 (Boulder).

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

At midnight there were 8 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 3 C class events was recorded during the day.

Spotted regions not numbered by NOAA/SEC:
[S466] This region emerged on October 25 in the northeast quadrant. Decay was observed on October 26 while the region developed slowly on October 27. Location at midnight: N16E34.

Coronal mass ejections (CMEs)

October 25-26: No obviously Earth directed CMEs observed.
October 27: A faint, slow, full halo CME was observed in LASCO C3 images beginning at 13:42 UTC. The origin of this CME may have been in region 10691 around 09h UTC. This was the only significant frontside activity that can be related to the CME. If the CME was frontsided it could reach Earth on October 31.

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 (CH121) in the southern hemisphere was in a geoeffective position on October 25-26.

Processed SOHO/EIT 284 image at 01:06 UTC on October 28. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on October 28. Quiet to active is possible on October 29-30 due to effects from coronal hole CH121 and on October 31 due to a possible CME impact.

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 fair and slowly becoming worse (propagation was good until just after midnight). Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: WLAM Lewiston ME and WWNN Boca Raton FL. On other frequencies propagation was best towards the eastern part of North America. US stations were heard before 21h UTC with the daytime signals of WFIF Milford CT on 1500 kHz and WIZZ Greenfield MA on 1520 kHz the most interesting stations.

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% less.

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.