Solar Terrestrial Activity Report

Last update issued on March 17, 2003 at 04:10 UTC. Minor update posted at 20:42 UTC.

[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update March 3, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update March 3, 2003)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update March 3, 2003)]
[Historical solar and geomagnetic data charts 1954-2002 (last update January 27, 2003)]
[Archived reports (last update March 17, 2003)]

Recent activity

The geomagnetic field was quiet to minor storm on March 16. Solar wind speed ranged between 583 and 747 km/sec under the influence of a high speed coronal hole stream.

Solar flux measured at 20h UTC on 2.8 GHz was 128.6. The planetary A index was 23 (STAR Ap - based on the mean of three hour interval ap indices: 23.9).
Three hour interval K indices: 33254454 (planetary), 22244343 (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 low. A total of 6 C class events were recorded during the day.

Region 10306 decayed slightly in the central penumbra. An interesting development was the emergence of a negative polarity field ahead of the positive polarity spots which had split off from the main penumbra. This development occurred to the north of the huge penumbra and at one point created a magnetic delta configuration. At midnight the delta was not there anymore but there is still a possibility that it could redevelop. Flare: C1.3 at 00:03 UTC.
Region 10311 decayed further. At the current rate of decay this region will soon become spotless.
Region 10313 decayed and could become spotless today.
Region 10314 developed quickly in the trailing spot section with a substantial increase in penumbral area. There is still a strong magnetic delta structure in this part of the region and a major flare is becoming a possibility. Flares: C3.0 at 04:15, C1.0 at 11:29, C1.2 at 13:12, C2.6 at 14:31 and a C1.2 long duration event peaking at 21:30 UTC.

Comment added at 20:42 UTC on March 17: Region 10314 was the source of a major X1.5/1B flare at 19:05 UTC (see this SXI image). Prior to the flare the magnetic delta in the large trailing penumbra had strengthened even more with opposite polarity umbrae located very close to each other. Further major flares are possible as long as the current spot layout exists. The X1.5 event may have been associated with a possibly geoeffective CME. Otherwise region 10306 has developed a magnetic delta structure in a northern penumbra and could produce M class flares. No other spotted regions are currently visible.

The coronal hole stream from the eastern part of CH25 appears to have arrived at ACE just after 19h UTC and the solar wind speed has since then ranged between 750 and 800 km/sec.

Coronal mass ejections (CMEs)

March 14-16: No obviously geoeffective 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, huge, recurrent coronal hole (CH25) mainly in the southern hemisphere will be in a geoeffective position on March 11-19. This coronal hole has developed in the northwestern and northeastern trans equatorial parts. After the emergence of region 10314 the central part of CH25 has weakened considerably, further development of region 10314 could completely close off the western part of CH25.

Processed SOHO EIT 284 image at 01:06 UTC on March 17. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly unsettled to active until March 22 due to a high speed coronal hole stream, occasional quiet or minor storm intervals are likely. The strongest part of the disturbance will probably occur on March 18-21. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor, propagation along north-south paths is good. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay]

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.
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 SEC/NOAA. 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.

Monthly solar cycle data

1) Running average based on the daily 20:00 UT observed solar flux value at 2800 MHz.
2) Unofficial, accumulated value based on the Boulder (SEC/NOAA) sunspot number. The official international sunspot number is typically 25-45% less.

This report has been prepared by Jan Alvestad. It is based partly on my own observations and interpretations, and partly on data from sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.