Solar Terrestrial Activity Report

Last update issued on May 11, 2003 at 01:55 UTC.

[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update May 1, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update May 1, 2003)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update May 1, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update April 13, 2003)]
[Archived reports (last update May 5, 2003)]

Recent activity

The geomagnetic field was quiet to major storm on May 10. Solar wind speed ranged between 505 and 769 km/sec. The disturbance which began on May 9 decreased in intensity after 11h UTC and was gradually replaced by a high speed stream from coronal hole CH38. While the source of the disturbance is not obvious, close examination of SXI images on May 7 revealed a filament eruption beginning at approximately 14h UTC. The location of this eruption was in the coronal "island" situated between the western and eastern parts of coronal hole CH38.

Solar flux measured at 20h UTC on 2.8 GHz was 92.7. The planetary A index was 43 (STAR Ap - based on the mean of three hour interval ap indices: 44.3).
Three hour interval K indices: 66652333 (planetary), 56444333 (Boulder).

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

At midnight there were 2 spotted regions on the visible disk. Solar flare activity was very low.

Region 10351 decayed slowly and quietly.
Region 10356 decayed slightly with the trailing fading slowly.

Coronal mass ejections (CMEs)

May 8-10: 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 huge recurrent coronal hole (CH38) in the southern hemisphere was in a geoeffective position on May 2-10.

Processed SOHO EIT 284 image at 19:06 UTC on May 10. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to minor storm until May 13. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor and will likely be very poor until at least May 14. Propagation along north-south paths is fair and is likely to at least fair until May 14. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay with a strong signal.]

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.