Solar Terrestrial Activity Report

Last update issued on March 21, 2003 at 04:30 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 20. Solar wind speed ranged between 578 and 813 km/sec. A solar wind shock was observed at ACE at 04:22 UTC. Solar wind speed increased abruptly to near 800 km/sec. The cause of the shock was likely a halo CME observed after the X1 flare in region 10314 near noon on March 18. The effects of the CME appeared to be ending before midnight and was replaced by a high speed coronal hole stream 

Solar flux measured at 20h UTC on 2.8 GHz was 97.4 (this is the lowest recorded solar flux value at 20h UTC since June 23, 1998). The planetary A index was 21 (STAR Ap - based on the mean of three hour interval ap indices: 22.6).
Three hour interval K indices: 13354444 (planetary), 23334433 (Boulder).

The background x-ray flux is at the class B1-B2 level.

At midnight there were 4 spotted regions on the visible disk, 1 of the regions has not yet been numbered by SEC/NOAA. Solar flare activity was moderate. A total of 1 C and 1 M  class events was recorded during the day.

Region 10314 decayed further as it began to rotate over the southwest limb.  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: C9.2 at 02:31 and M1.5/1F at 11:31 UTC.
Region 10316 was quiet and table.
New region 10317 emerged on March 19 and was numbered the next day. The region has decayed and could soon become spotless.

Spotted regions not yet numbered by SEC/NOAA:
[S125] A new region emerged in the northwest quadrant. Location at midnight: N12W53.

Coronal mass ejections (CMEs)

March 19-20: 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 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 01:06 UTC on March 21. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to minor storm on March 21 and quiet to active on March 22-24 due to a high speed stream, then unsettled to minor storm on March 25-26 due to a high speed stream from coronal hole CH26. 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 fair to 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.