Solar Terrestrial Activity Report

Last update issued on March 27, 2003 at 04:40 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 24, 2003)]

Recent activity

The geomagnetic field was quiet to unsettled on March 26. Solar wind speed ranged between 349 and 430 km/sec. A fairly weak coronal hole stream began to influence the geomagnetic field early in the day. While solar wind parameters were not fully consistent with a coronal hole stream early in the day, the disturbance had a more obvious coronal hole origin later on.

Solar flux measured at 20h UTC on 2.8 GHz was 127.2. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 9.9).
Three hour interval K indices: 13232223 (planetary), 14222213 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight there were 6 spotted regions on the visible disk, 1 of the regions has not yet been numbered by SEC/NOAA. Solar flare activity was low. Only 1 C class event was recorded during the day.

Region 10318 decayed further in the trailing spots while penumbra formed on one of the leader spots.
Region 10319 developed very quickly and was near the size of region 10321 at the end of the day. Some polarity intermixing is obvious and the region has become capable of producing minor M class flares.
Region 10320 was mostly unchanged and quiet.
Region 10321 developed further and now has 2 magnetic delta structures, one in a penumbra in the southwestern section and another in the northern part of a trailing penumbra. The chance of an M class flare is obviously increasing. Flare: C2.2 at 17:10 UTC.
Region 10323 developed slowly and quietly.

Spotted regions not yet numbered by SEC/NOAA:
[S128] A new region rotated into view at the southeast limb late on March 26. Location at midnight: S18E79.

Coronal mass ejections (CMEs)

March 24-26: 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 coronal hole (CH27) in the southern hemisphere will rotate into a geoeffective position on March 24-27, this coronal hole is best defined in the section due west of region 10318. A coronal hole (CH28) in the northern hemisphere will rotate into a geoeffective position on March 28. A coronal hole (CH29) in the southern hemisphere will be in a possibly geoeffective position on March 29-31.

Processed SOHO EIT 284 image at 01:06 UTC on March 27. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to minor storm on March 27 due to a high speed stream from coronal hole CH26. Quiet to active is likely on March 28-31 due to other high speed streams, this time from CH27 and then CH28. 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. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: none, several stations noted including Radio Cristal del Uruguay, Radio Vibración (Venezuela) and unidentified stations from Brazil.]

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 UTC 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.