Solar Terrestrial Activity Report

Last update issued on May 22, 2003 at 02:40 UTC.

[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update 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 minor storm on May 21. Solar wind speed ranged between 353 and 563 km/sec. A high speed stream from coronal hole CH40 arrived at approximately 11h UTC at ACE and dominated the solar wind for the remainder of the day.

Solar flux measured at 20h UTC on 2.8 GHz was 119.3. The planetary A index was 20 (STAR Ap - based on the mean of three hour interval ap indices: 21.0).
Three hour interval K indices: 34223445 (planetary), 34223444 (Boulder).

The background x-ray flux is at the class B3 level.

At midnight there were 6 spotted regions on the visible disk. Solar flare activity was low. A single C class event was recorded during the day.

Region 10357 decayed further and was quiet.
Region 10362 decayed somewhat in the trailing spot section. Polarities are still intermixed and C class flares are possible. Flare: C1.2 at 06:04 UTC.
Region 10364 decayed and lost spots and penumbral area.
Region 10365 was quiet and stable.

Spotted regions not numbered by SEC/NOAA:
[S165] A new region emerged south of region 10365 on May 21. The region appears to be decaying and could soon become spotless again. Location at midnight: S13E54.
[S166] A new region rotated partially into view at the southeast limb on May 21. Location at midnight: S14E82.

Early on May 22 a fairly large penumbra is rotating into view at the southeast limb, location at 02h UTC: S35E87.

Coronal mass ejections (CMEs)

May 20-21: No obviously geoeffective CMEs observed.

May 19: A filament eruption in the northeast quadrant north of coronal hole CH40 began at approximately 08:20 UTC 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 (CH40) was in a geoeffective position on May 18-21. A recurrent coronal hole (CH41) in the southern hemisphere will rotate into a geoeffective position on May 24.

Processed SOHO EIT 284 image at 19:06 UTC on May 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 May 22-24 due to a high speed stream from coronal hole CH40 and quiet to active on May 25.

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 to fair and 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, weak signals noted from Radio Cristal del Uruguay and at least one station 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 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.