Solar Terrestrial Activity Report

Last major update issued on February 13, 2004 at 04:35 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 unsettled to minor storm on February 12. Solar wind speed ranged between 430 and 880 km/sec, increasing quickly early in the day under the influence of a high speed stream from coronal hole CH80.

Solar flux measured at 20h UTC on 2.8 GHz was 112.2. The planetary A index was 28 (STAR Ap - based on the mean of three hour interval ap indices: 29.5).
Three hour interval K indices: 34554443 (planetary), 34433443 (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 very low. No C class events was recorded during the day.

Region 10551 decayed quickly and lost all spots outside of the main penumbra.
Region 10554 decayed slowly and quietly.
Region 10555 decayed and could soon become spotless.
Region 10556 developed slowly. The region currently has a simple layout with the opposite polarity areas well separated.

Spotted regions not numbered by NOAA/SEC:
[S351] This region emerged on February 11 in the central western part of coronal hole CH80 near the center of the visible disk. Currently located on a coronal island drifting slowly southwards (compare the coronal hole and active region maps for February 12 and 11 below to observe this) towards the southern border of CH80, the region developed penumbra in both polarities on February 12. Location at midnight: S10W20.
[S352] A new region emerged very quickly late on February 12 in the southeast quadrant. The region is complex with positive polarity emerging inside a negative polarity area. Early on February 13 a magnetic delta structure has formed. Should the current rate of development continue this region will soon begin producing C flares and possibly even minor M class flares. Location at midnight: S16E46.

Coronal mass ejections (CMEs)

February 10-12: 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) was in a geoeffective position on February 9-13.

Processed SOHO/EIT 284 image at 01:06 UTC on February 13. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to minor storm on February 13-16 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 very poor. Propagation along long distance north-south paths is fair to good. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay. Propagation was best in the 700-1200 kHz range with unusually many stations from Argentina, Uruguay, Paraguay and Brazil noted. Before 04 UTC several stations from Venezuela became audible as well].

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.