Solar Terrestrial Activity Report

Last major update issued on October 21, 2004 at 02:40 UTC. The next major update will be on October 25 as I will be attending a DXLC board meeting.

[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 quiet to active on October 20. Solar wind speed ranged between 348 and 449 km/sec under the influence of a coronal hole flow.

Solar flux measured at 20h UTC on 2.8 GHz was 111.3. The planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 11.5).
Three hour interval K indices: 13314412 (planetary), 23313322 (Boulder).

The background x-ray flux is at the class B3 level.

At midnight there were 7 spotted regions on the visible solar disk. The solar flare activity level was moderate. A total of 1 C and 1 M class events was recorded during the day.

Region 10682 decayed slowly with the single penumbra losing area.
Region 10683 developed new spots and has minor polarity intermixing.
Region 10684 decayed slowly and quietly.
Region 10685 developed slowly and was quiet.
Region 10687 is a fairly complex and compact region with most spots inside a single penumbra. Further M class flaring is possible. Flare: M2.6 at 10:51 UTC.
New region 10688 emerged in the southwest quadrant on October 19 and was numbered by SEC the following day. The region developed slowly on October 20.

Spotted regions not numbered by NOAA/SEC:
[S464] A new bipolar region emerged immediately to the west of region 10682 on October 18. Quick development was observed late on October 19 and early on October 20. A minor M class flare is possible. Location at midnight: S12W36. Flare: C4.5 at 02:13 UTC.

Coronal mass ejections (CMEs)

October 19-21: No obviously Earth directed CMEs observed.

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 coronal hole (CH120) - an extension of the northern polar coronal hole -  will be in a geoeffective position on October 19-22.

Processed SOHO/EIT 284 image at 19:06 UTC on October 20. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on October 21 and quiet on October 22. A recurrent high speed coronal hole stream (from coronal hole CH120) will likely reach Earth on October 23 and cause unsettled to active conditions during the latter half of that day and on October 24-25.

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. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: none, only a few weak signals observed. On other frequencies propagation was best towards the Canadian Atlantic provinces and the northeastern and southeastern part of the USA. I observed 3 stations on 610 kHz: the frequency dominant WIOD, CHNC and an unidentified station. 850 kHz had WEEI Boston at times with an excellent signal, occasionally with WFTL a strong second signal. Most of the New York 50 kW stations had strong 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% 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.