Solar Terrestrial Activity Report

Last update issued on February 1, 2003 at 01:40 UTC. Minor update posted at 17:15 UTC.

[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update January 1, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update January 1, 2003)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update January 1, 2003)]
[Historical solar and geomagnetic data charts 1954-2002 (last update January 27, 2003)]
[Archived reports (last update January 27, 2003)]

Recent activity

The geomagnetic field was quiet to minor storm on January 31. Solar wind speed ranged between 399 and 620 km/sec, generally decreasing after 09h UTC as a coronal stream began to weaken.

Solar flux measured at 20h UTC on 2.8 GHz was 120.4. The planetary A index was 18 (STAR Ap - based on the mean of three hour interval ap indices: 17.0).
Three hour interval K indices: 32454321 (planetary), 32343321 (Boulder).

The background x-ray flux is at the class B5 level.

At midnight there were 5 spotted regions on the visible disk. Solar flare activity was low. A total of 3 C class flares were recorded during the day.

Region 10269 was quiet and stable.
Region 10272 decayed slowly and quietly.
Region 10273 decayed slowly and lost all remaining trailing spots.
Region 10274 was quiet and stable.

A new region should soon rotate into view at the southeast limb. This region in SOHO EIT images appears to be the source of all C flares noted during the day, a C2.2 long duration event peaking at 0606, a C1.5 flare at 07:20 and a C1.4 long duration event peaking at 13:21 UTC.

Comment added at 17:15 UTC on February 1: Solar activity has increased a lot today with several C flares and one minor M class flare (long duration M1.2 peaking at 09:05 UTC). Most of the events have occurred in a region rotating into view at the southeast limb.

An unusual solar storm arrived at SOHO near 13:10 UTC. This storm is unusual in that solar wind speed was very low at the time of its arrival, and, probably more significant, had some of the highest peak solar wind speeds recorded during this solar cycle. During the early solar wind shock the velocity jumped abruptly from 390 to 520 km/sec, then increased slowly to 600 km/sec. At 14:30 UTC at SOHO there was another shock, this time speed increased to above 800 km/sec. By 16h UTC solar wind speed had peaked just below 1000 km/sec. The interplanetary magnetic field has, with the exception of a short southward swing, been northwards since the first shock.

Coronal mass ejections (CMEs)

January 29 and 31: No obviously geoeffective CMEs observed.

January 30: A large filament eruption across the central meridian and stretching from the equator until almost halfway towards the north pole was observed beginning at about 06:30 UTC. An associated full halo CME was observed with the leading part seen above the northwest limb at 10:06 UTC in LASCO C2 images. The CME will likely impact Earth sometime between 15h UTC on February 1 and 09h UTC on February 2.

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

Two coronal holes in the northern hemisphere were geoeffective on January 29-30. A large and well defined trans equatorial extension of the northern polar coronal hole will rotate into a geoeffective position on February 1-3.

Processed SOHO EIT 284 image at 19:06 UTC on January 31. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on February 1. Late on February 1 or early on February 2 a CME is likely to reach Earth. Active to major storm conditions are possible for the first 24h afterwards. A possibly strong coronal stream will likely begin to influence the geomagnetic field on February 4 and could cause unsettled to minor storm conditions until February 6 or 7. 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 fair to good.

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)

Composite image based on a SOHO/MDI continuum image and overlaid by a coronal hole image. Region numbering has been included. 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 UT 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.