Solar Terrestrial Activity Report

Last update issued on April 5, 2003 at 02:50 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 1, 2003)]

Recent activity

The geomagnetic field was unsettled to minor storm on April 4. Solar wind speed ranged between 459 and 509 km/sec under the influence of a high speed stream from coronal hole CH29.

Solar flux measured at 20h UTC on 2.8 GHz was 152.5. The planetary A index was 26 (STAR Ap - based on the mean of three hour interval ap indices: 27.4).
Three hour interval K indices: 43555344 (planetary), 33554333 (Boulder).

The background x-ray flux is at the class B8 level.

At midnight there were 6 spotted regions on the visible disk. Solar flare activity was moderate. A total of 18 C and 1 M class events was recorded during the day. Region 10323 at the southwest limb produced a C1.2 flare at 02:39 and a C3.1 at 13:41 UTC while spotless region 10327 generated a C1.0 flare at 02:47 UTC.

Region 10321 developed slowly and will likely continue to produce C flares while rotating to the northwest limb. Flares: C1.2 at 01:51, C3.4 at 14:16, C2.7 at 15:55, C1.6 at 17:04, C2.2 at 17:12 and C9.7 at 20:50 UTC.
Region 10325 was quiet and stable.
Region 10326 decayed slowly and was quiet.
Region 10330 was quiet and stable.

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 has been developing and currently has two magnetic delta structures. Further minor M class flares are possible. Location at midnight: S14W48. Please note that SEC/NOAA has this as region 10324! Flares: C1.9 at 04:34, C2.4 at 06:55, C2.8 at 08:40, C2.0 at 10:01, C3.9 at 12:17, C2.0 at 17:36, a long duration M2.1 event peaking at 20:19 and a C2.8 event at 22:18 UTC.
[S130] A new region emerged on April 2 south southeast of region 10325 with quite a few spots. Slow decay was observed on April 3 and the region became spotless before noon on April 4. The region then reemerged and currently has penumbra on both a leading and a trailing spot. Location at midnight: N07W19.

Coronal mass ejections (CMEs)

April 2-4: 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 will likely rotate into a geoeffective position on April 5. Another coronal hole (CH31) in the southern hemisphere will probably be in a geoeffective position on April 6-8.

Processed SOHO EIT 284 image at 19:06 UTC on April 4. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to minor storm on April 5 due to a high speed stream from coronal hole CH29 and quiet to unsettled on April 6-7. Quiet to active is likely on April 8 as a high speed stream from CH30 reaches Earth, with unsettled to minor storm conditions possible on April 9-12 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 to fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: none, Radio Cristal del Uruguay noted at times as well as a few unidentified stations 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 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.