Solar Terrestrial Activity Report

Last update issued on May 20, 2003 at 02:30 UTC.

[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update 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 19, 2003)]

Recent activity

The geomagnetic field was quiet to active on May 19. Solar wind speed ranged between 382 and 448 km/sec under the influence of a fairly weak high speed stream from coronal hole CH39.

Solar flux measured at 20h UTC on 2.8 GHz was 114.7. The planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.6).
Three hour interval K indices: 33232334 (planetary), 32233333 (Boulder).

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

At midnight there were 6 spotted regions on the visible disk. Solar flare activity was very low.

Region 10357 decayed losing penumbral area both in the leading and trailing spot sections.
Region 10362 did not change much. The only change of significance was the increased separation between the negative and positive polarity areas in the trailing spot section.
New region 10364 emerged on May 18 in the southwest quadrant and was numbered by SEC the next day. The region developed quickly on May 19 and is capable of producing C flares. Minor M class flaring is becoming a possibility as a magnetic delta structure is forming in the central part of the region.

Spotted regions not numbered by SEC/NOAA:
[S162] A new region emerged in the southwest quadrant on May 19, south of region 10357 and to the west of region 10364. Location at midnight: S24W40.
[S163] A new region emerged in the northwest quadrant late on May 19. Location at midnight: N20W14.
[S164] A new region rotated into view at the southeast limb on May 19. Location at midnight: S07E79.

Coronal mass ejections (CMEs)

May 17-18: No obviously geoeffective CMEs observed.

May 19: A filament eruption in the northeast quadrant north of coronal hole CH40 began at approximately 08:20 and peaked two hours later. A partial halo CME was observed later on in LASCO C3 images with most of the ejected material visible above the northeast limb and the north pole. This CME will probably not reach Earth.

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 recurrent trans equatorial coronal hole (CH39) was in a geoeffective position on May 15-16. A recurrent trans equatorial coronal hole (CH40) will rotate into a geoeffective position on May 18-20.

Processed SOHO EIT 284 image at 01:06 UTC on May 20. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on May 20 and quiet to unsettled on May 21. A high speed stream from coronal hole CH40 is expected to influence the field from late on May 21 until May 24 and cause unsettled to active conditions with a possibility of occasional minor storm intervals. 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 25. Propagation along north-south paths is poor but should improve to fair over the next few days. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: none, rather weak signals from Radio Cristal del Uruguay and a couple of stations from Brazil were noted]

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 30-50% 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.