Solar Terrestrial Activity Report

Last update issued on March 20, 2003 at 03:30 UTC. Minor update posted at 05:33 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 active on March 19. Solar wind speed ranged between 578 and 770 km/sec under the influence of a high speed coronal hole stream.

Solar flux measured at 20h UTC on 2.8 GHz was 108.2. The planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.8).
Three hour interval K indices: 44333332 (planetary), 34322322 (Boulder).

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

At midnight there were 3 spotted regions on the visible disk, 1 of the regions has not yet been numbered by SEC/NOAA. Solar flare activity was high. A total of 16 C and 5 M  class events were recorded during the day.

Region 10314 decayed significantly as the central penumbra split into several penumbrae. The magnetic delta structure disappeared during the day and the region is unlikely to produce further major flares. An isolated minor M class flare may still be possible. Flares: C6.2 at 00:18, C1.5 at 01:50, C1.7/1N at 02:15, C3.4 at 02:44, M1.5 at at 03:07, long duration M1.2 event peaking at 03:43, M1.6 at 06:46, M3.7/1N at 09:53, C5.8 at 11:25, C1.0 at 13:09, M1.4 at 13:32, C1.1 at 16:10, C3.2 at 16:48, C1.9 at 17:11, C1.3 at 18:21, C6.3 at 18:54, C1.3 at 20:51, C1.8 at 21:04, C2.2 at 21:28, C3.5 at 22:00 and C2.0 at 23:15 UTC.
Region 10316 was quiet and table.

Spotted regions not yet numbered by SEC/NOAA:
[S124] A new region emerged in the northeast quadrant. Location at midnight: N05E18.

Comment added at 05:33 UTC on March 20: A solar wind shock was observed at ACE at 04:22 UTC. Solar wind speed increased abruptly to 800 km/sec. The interplanetary magnetic field has swung moderately southwards and active to minor storm conditions are likely for the remainder of the day.

Coronal mass ejections (CMEs)

March 17: A possibly geoeffective CME may have been associated with an X class flare in region 10314.

March 18: A fast CME, probably with a geoeffective extension, was observed after the X1/1B flare in region 10314. This CME will likely reach Earth on March 20 and could cause unsettled to minor storm conditions.

March 19: A full halo CME was observed early in the day with the major part of the ejected material seen below the south pole. The source of this CME was likely backsided.

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 was 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 southeastern part of CH25 appears to have closed. A well placed, developing and recurrent coronal hole (CH26) in the northern hemisphere will rotate into a geoeffective position on March 22-23.

Processed SOHO EIT 284 image at 19:06 UTC on March 19. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active until March 23 due to a high speed stream. A CME associated with an X1 event in region 10314 near noon on March 18 is likely to arrive on March 20 and cause unsettled to minor storm conditions. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is poor, propagation along north-south paths is fair to good. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay before 02h UTC, then Abril 1470 AM (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.