Solar Terrestrial Activity Report

Last major update issued on February 26, 2004 at 04:00 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 25. Solar wind speed ranged between 337 and 381 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 118.5. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 9.0).
Three hour interval K indices: 21233322 (planetary), 22222222 (Boulder).

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

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

Region 10563 was quiet and stable.
Region 10564 developed quickly with penumbra forming all the way between large spots in the northeastern and southwestern part of the region. A strong magnetic delta structure has developed in the central part of this large region. M and X class flares are likely. Flares: C2.4 at 02:08, C1.0 at 05:29, C1.3 at 06:52, C1.1 at 10:47, C1.3 at 11:26, C8.0 at 12:25, C2.6 at 16:27 and C2.6 at 23:15 UTC. This region was the source of an X1.1 flare at 02:03 UTC on February 26. It is not yet known if there was a geoeffective CME associated with this event.
Region 10565 developed moderately quickly with most of the development occurring in the intermediate and trailing spot sections. C flares are possible.

Coronal mass ejections (CMEs)

February 23-25: 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

The southernmost part of a coronal hole (CH82) in the northern hemisphere was likely in a geoeffective position on February 22-23. A recurrent trans equatorial coronal hole (CH83) will rotate into a geoeffective position on February 26-28.

Processed SOHO/EIT 284 image at 13:06 UTC on February 25. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on February 26-28. 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 poor to fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela) on the WSW antenna, Radio Cristal del Uruguay on the southwesterly longwire. On other frequencies strong signals were noted from a number of east coast North American stations with WINS 1010, WBBR 1130, WTOP 1500 and WWZN 1510 having the best 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.