Solar Terrestrial Activity Report

Last update issued on April 15, 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 April 2, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update April 2, 2003)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update April 2, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update April 13, 2003)]
[Archived reports (last update April 14, 2003)]

Recent activity

The geomagnetic field was quiet to minor storm on April 14. Solar wind speed ranged between 458 and 623 km/sec under the influence of a high speed stream from coronal hole CH32.

Solar flux measured at 20h UTC on 2.8 GHz was 102.0. The planetary A index was 16 (STAR Ap - based on the mean of three hour interval ap indices: 16.8).
Three hour interval K indices: 23125433 (planetary), 24224333 (Boulder).

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

At midnight there were 4 spotted regions on the visible disk. Solar flare activity was low. Only 1 C class event was recorded during the day.

Region 10330 decayed slowly and quietly and will soon be rotating out of view at the northwest limb.
Region 10332 decayed and could become spotless within a couple of days.
Region 10334 did not change much and was quiet.
Region 10335 decayed slowly and could soon become spotless. Flare: C1.1 long duration event peaking at 09:30 UTC.

Coronal mass ejections (CMEs)

April 12-14: 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 large trans equatorial southern hemisphere coronal hole (CH32) was in a geoeffective position on April 11-13, CH32 has become smaller over the last rotation. A small coronal hole (CH33) in the southern hemisphere will likely rotate into a geoeffective position on April 18. A small coronal hole (CH34) in the northern hemisphere will rotate into a geoeffective position on April 19.

Processed SOHO EIT 284 image at 19:06 UTC on April 14. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to active on April 15-16 due to a high speed stream from coronal hole CH32. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is likely to remain very poor until at least April 19. Propagation along north-south paths is poor to fair becoming fair until April 18. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight:  Radio Vibración (Venezuela).]

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.