Solar Terrestrial Activity Report

Last update issued on April 10, 2003 at 03:15 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 minor storm on April 9. Solar wind speed ranged between 393 and 510 km/sec. A high speed stream from coronal hole CH31 began to dominate the solar wind after 17h UTC, prior to that the disturbance which began on April 8 appears to have mixed with a high speed stream from coronal hole CH30.

Solar flux measured at 20h UTC on 2.8 GHz was 109.4. The planetary A index was 25 (STAR Ap - based on the mean of three hour interval ap indices: 26.0).
Three hour interval K indices: 43545332 (planetary), 53544333 (Boulder).

The background x-ray flux is at the class B1-B2 level.

At midnight there were 6 spotted regions on the visible disk. Solar flare activity was moderate. A total of 5 C and 1 M class events was recorded during the day.

Region 10330 lost the trailing spots which had developed rudimentary penumbra. A few new small spots emerged while the main penumbra was basically unchanged.
Region 10331 was quiet and stable.
Region 10332 developed slowly and was quiet.

Spotted regions not yet numbered by SEC/NOAA:
[S133] A new region emerged in the southwest quadrant on April 8. The region developed quickly early on April 9 and may be capable of further minor M class flaring. Location at midnight: S13W76. SEC has this as region 10326, even though the new region emerged 6 degrees further east and 3 degrees further south than the expected position of region 10326.
[S134] A new region emerged in the southeast quadrant on April 8 and decayed slightly on April 9 with the leading spot disappearing while a new trailing spot emerged. Location at midnight: S15E14. Flares: C1.1 at 02:54, C3.8 at 03:49, C1.1 at 05:37, C4.7 at 06:13, C6.4 at 09:33 and M2.5/1F at 23:29 UTC.
[S135] A new region rotated into view at the southeast limb late on April 9. Location at midnight: S10E81.

Coronal mass ejections (CMEs)

April 7-9: 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

The western part of a huge coronal hole (CH31), mainly in the southern hemisphere, was in a geoeffective position on April 6-9. The eastern part of CH31 will rotate to a geoeffective position on April 11-12.

Processed SOHO EIT 284 image at 19:06 UTC on April 9. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to minor storm on April 10-13 when the high speed stream from CH31 dominates the solar wind, isolated major storm intervals are possible on April 11 and 12. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor and will likely remain so at least until April 17, propagation along north-south paths is poor to fair but should become fair to good over the next few days and remain fairly good until at least April 16. [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.