Solar Terrestrial Activity Report

Last update issued on March 18, 2003 at 01:50 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 unsettled to major storm on March 17. Solar wind speed ranged between 602 and 831 km/sec under the influence of a high speed coronal hole stream.

Solar flux measured at 17 and 23h UTC on 2.8 GHz was 124.4 (the measurement at 20h UTC was highly influenced by the X class flare). The planetary A index was 39 (STAR Ap - based on the mean of three hour interval ap indices: 40.8).
Three hour interval K indices: 34646445 (planetary), 34545435 (Boulder).

The background x-ray flux is at the class B5 level.

At midnight there were 3 spotted regions on the visible disk. Solar flare activity was high. A total of 7 C and 1 X class events were recorded during the day. A C1.8 flare at 01:55 UTC had its source at the southeast limb.

Region 10306 developed a magnetic delta structure in the northernmost penumbra. An M class flare is possible.
Region 10311 decayed and will probably become spotless early today.
Region 10314 developed in the central large penumbra with narrowly separated opposite polarity umbrae within this penumbra. As long as this delta configuration persists there further major flares are likely. Flares: C3.1 at 01:03, C2.1 long duration event peaking at 15:51, C7.7 at 16:50, a major X1.5/1B event (and associated with a minor proton flux increase) at 19:05 (see this SXI image), C6.9 at 20:21, C2.8 at 21:20 and C1.7 at 23:57 UTC.

Coronal mass ejections (CMEs)

March 15-16: No obviously geoeffective CMEs observed.

March 17: A possibly geoeffective CME may have been associated with the X class flare in region 10314. A more definitive analysis is awaiting the availability of images covering the hours after the eruption.

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. A coronal hole (CH26) in the northern hemisphere will rotate into a geoeffective position on March 23.

Processed SOHO EIT 284 image at 19:06 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 23 due to a high speed coronal hole stream, occasional 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 useless, propagation along north-south paths is poor to fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Rádio Guanancés de Itapajé (Brasil)]

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.