Solar Terrestrial Activity Report

Last major update issued on February 27, 2004 at 03:05 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update February 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update February 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update February 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2003 (last update January 16, 2004)]
[Archived reports (last update February 26, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on February 26. Solar wind speed ranged between 289 and 350 km/sec. A fairly weak disturbance began early on February 27 with the interplanetary magnetic field swinging weakly to moderately southwards.

Solar flux measured at 20h UTC on 2.8 GHz was 120.8. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 6.8).
Three hour interval K indices: 11122321 (planetary), 11112211 (Boulder).

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

At midnight there were 4 spotted regions on the visible disk. Solar flare activity was high. A total of 5 C, 1 M and 1 X class events was recorded during the day. 

Region 10563 was quiet and stable.
Region 10564 developed further and has a huge penumbra (measuring 8 degrees longitudinal extent and 5 degrees latitudinal extent in an irregular shape) containing many positive and negative polarity spots. A strong and large magnetic delta is near the center of this penumbra. Further M and X class flares are likely. Flares: C1.8 at 01:07, major X1.1/2N at 02:03 (no CME observed), C1.6 at 04:49, C2.4 at 05:39, C6.5 at 14:20, C7.5 at 20:18 and a major M5.7 event at 22:30 UTC.
Region 10565 added penumbral area in the leading spot section while some penumbra disappeared from the trailing spots.

Spotted regions not numbered by NOAA/SEC:
[S364] A new region emerged near the southeast limb on February 26. Location at midnight: S14E65.

Coronal mass ejections (CMEs)

February 24-26: No partly or fully 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 well defined  recurrent trans equatorial coronal hole (CH83) will rotate into a geoeffective position on February 26-28.

Processed SOHO/EIT 284 image at 19:06 UTC on February 26. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on February 27-28. On February 29 - March 2 a high speed stream from coronal hole CH83 will likely cause unsettled to minor storm conditions.

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 fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela) and WLAM Lewiston ME from midnight to 02 UTC, then WLAM disappeared and Radio Cristal del Uruguay became stronger. At that time the station in Cordoba (Argentina) on 700 kHz appeared with an unusually strong signal. Several of the usual east coast North American stations were noted with occasionally strong signals].

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.

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 sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.