Solar Terrestrial Activity Report

Last major update issued on February 10, 2004 at 04:15 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 9, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on February 9. Solar wind speed ranged between 365 and 449 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 117.8. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 9.3).
Three hour interval K indices: 21123332 (planetary), 10113232 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight there were 6 spotted regions on the visible disk. Solar flare activity was low. A total of 9 C class events was recorded during the day.

Region 10549 decayed and had only a few small spots left by midnight, the region could become spotless today.
Region 10551 decayed slowly and lost about a quarter of the penumbral area. There is still a weak magnetic delta structure in the eastern part of the largest trailing penumbra. A minor M class flare is possible.
Region 10554 developed quickly early in the day, produced many flares, then began to decay. The current magnetic field layout is much simpler than just one day ago. The magnetic delta structure in the leading penumbra has disappeared. A minor M class flare is possible. Flares: C1.6 at 01:01, C1.7 at 01:50, C1.7 at 03:07, C5.5 at 05:50, C4.3 at 09:46, C9.6 at 11:02, C2.7 at 13:00, C5.6 at 14:03, C1.9 at 15:11 UTC.
New region 10555 rotated into view at the southeast limb on February 8 and was numbered by SEC the next day. The region developed slowly on February 9.

Spotted regions not numbered by NOAA/SEC:
[S349] This region emerged in the northwest quadrant on February 9. Location at midnight: N07W20.
[S350] A new region emerged in the northeast quadrant on February 9. Location at midnight: N16E46.

Coronal mass ejections (CMEs)

February 7-9: 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 recurrent trans equatorial coronal hole (CH80) will rotate into a geoeffective position on February 9-12, the easternmost half is poorly defined.

Processed SOHO/EIT 284 image at 01:06 UTC on February 10. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled February 10-11 and unsettled to active on February 12-15 due to a high speed stream from coronal hole CH80.

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 currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay on the longwire aimed southwest, Radio Vibración (Venezuela) on the northwesterly EWE. Otherwise quite a few stations from the northeastern USA and Canada could be heard throughout the mediumwave band with reception improving slowly during the monitoring period. Propagation in the lower part of the band was not nearly as good as yesterday].

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.