Solar Terrestrial Activity Report

Last major update issued on January 7, 2004 at 03:10 UTC. Minor update posted at 10:44 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update January 4, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update January 4, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update January 4, 2004)]
[Historical solar and geomagnetic data charts 1954-2003 (last update October 15, 2003)]
[Archived reports (last update January 1, 2004)]

Recent activity

The geomagnetic field was unsettled to minor storm on January 6. Solar wind speed ranged between 553 and 807 km/sec. Until 19:27 UTC at ACE the main solar wind source was a slowly weakening high speed stream from coronal hole CH74. At that time a moderate solar wind shock was observed, its source being the CME observed after the long duration M6.9 event in region 10536 early on January 5 - CME transit time was 39-40 hours. Solar wind speed later on increased to above 800 km/sec. The interplanetary field was initially moderately to strongly southwards but has been only weakly southwards early on January 7.

Solar flux measured at 20h UTC on 2.8 GHz was 117.3. The planetary A index was 20 (STAR Ap - based on the mean of three hour interval ap indices: 21.3).
Three hour interval K indices: 33433335 (planetary), 34422235 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight there were 3 spotted regions on the visible disk. Solar flare activity was high. A total of 4 C and 1 M class events was recorded during the day.

Region 10534 decayed and had only a single small spot left late in the day.
Region 10536 developed slowly and has a significant magnetic delta structure in the southeastern part of the huge main penumbra. A small delta is located further north. Another major flare remains a possibility. Flares: C2.5 at 07:18, C1.0 at 21:55 and C1.1 at 22:41 UTC.
New region 10537 rotated into view at the northeast limb. This is a complex region with a positive polarity field in the south and southeast extending to the center of the region, the negative polarity field is in the central western part and in the north. There is at least one magnetic delta structure and another major flare is possible. Flares: C1.0 at 02:28 and a major impulsive M5.8 at 06:29 UTC.

Comment added at 04:13 UTC on January 7: Region 10537 was the origin of an M4.5 flare at 04:04 UTC. The interplanetary magnetic field has become increasingly southwards since 03h UTC. If this development continues, major storm intervals will become possible.

Comment added at 10:44 UTC: Region 10537 continues to be very active and produced a major M8.3 flare at 10:27 UTC. An X flare could be possible. The geomagnetic field is currently at minor storm levels.

Coronal mass ejections (CMEs)

January 6: No partly or fully earth directed CMEs observed.

January 5: A fairly large partial halo CME was associated with the major M6.9 long duration event in region 10536 early in the day. Material outflow was observed over the east limbs and the southwest limb in LASCO images several hours after the event.

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 recurrent trans equatorial coronal hole (CH74) was in a geoeffective position on January 1-5.

Processed SOHO/EIT 284 image at 19:06 UTC on December 26. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to minor storm on January 7 due to effects from a CME. Quiet to active is expected for January 8-9.

Long distance low frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor to very poor. Propagation along long distance north-south paths is fair to good. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Early on many stations from Brazil could be heard, including Rádio Papacaça, then slowly Radio Cristal del Uruguay and Radio Rafaela (Argentina) took command. A few east coast US stations were heard for a short time, WWZN Boston on 1510 kHz had a good signal then].

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. When the high speed stream has arrived the color changes to green.
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 NOAA/SEC. 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. SEC active region numbers in the table below and in the active region map above are the historic SEC/USAF numbers.

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 (NOAA/SEC) sunspot number. The official international sunspot number is typically 30-50% less.

This report has been prepared by Jan Alvestad. It is based partly on my own observations and analysis, and partly on data from sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.