Solar Terrestrial Activity Report

Last update issued on April 8, 2003 at 01:50 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 1954-2002 (last update January 27, 2003)]
[Archived reports (last update April 7, 2003)]

Recent activity

The geomagnetic field was quiet to unsettled on April 7. Solar wind speed ranged between 349 and 378 km/sec. A weak solar wind shock was observed at SOHO at 00:07 UTC on April 8. Solar wind speed jumped from 350 to 400 km/sec. The source of this shock is likely a CME observed after an M2 event in region S129 on April 4.

Solar flux measured at 20h UTC on 2.8 GHz was 115.6. The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 7.1).
Three hour interval K indices: 21123311 (planetary), 22222212 (Boulder).

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

At midnight there were 5 spotted regions on the visible disk. Solar flare activity was low. A total of 2 C class events was recorded during the day. More interesting was perhaps a long duration B7.3 event peaking at 10:30 UTC from a source behind the southwest limb. A proton flux enhancement has been in progress since that event began. 

Region 10325 decayed slowly and quietly.
Region 10330 added a few small spots while the large penumbra took on a more ragged appearance.
Region 10331 was quiet and stable.
New region 10332 rotated into view at the northeast limb on April 6 and was numbered by SEC/NOAA the next day.

Spotted regions not yet numbered by SEC/NOAA:
[S129] A new region emerged northwest of region 10324 in the southeast quadrant on March 30. This region developed until April 4 and decayed quickly on April 5 and 6. Location at midnight: S13W88. Please note that SEC/NOAA has this as region 10324! Flares: C2.6 flare at 03:04 and C1.2 at 18:49 UTC.

Coronal mass ejections (CMEs)

April 5-7: 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 small coronal hole (CH30) in the southern hemisphere was in a geoeffective position on April 5. Another and large coronal hole (CH31) in the southern hemisphere will be in a geoeffective position on April 6-9. CH31 is the western part of a huge recurrent coronal hole, the eastern part is rotating into view. The northeastern part of CH31 is trans equatorial.

Processed SOHO EIT 284 image at 19:06 UTC on April 7. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active, possibly with minor storm intervals, on April 8 due to effects from the CME impact observed early in the day and a high speed stream from CH30. Unsettled to major storm conditions are possible on April 9-13 when the high speed stream from CH31 dominates the solar wind. 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 poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay.]

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.