Solar Terrestrial Activity Report

Last major update issued on January 20, 2004 at 05:20 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 January 16, 2004)]
[Archived reports (last update January 19, 2004)]

Recent activity

The geomagnetic field was quiet to active on January 19. Solar wind speed ranged between 552 and 720 km/sec under the influence of a high speed stream from coronal hole CH76.

Solar flux measured at 20h UTC on 2.8 GHz was 134.6 (slightly enhanced by a C8 flare). The planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 18.0).
Three hour interval K indices: 32344433 (planetary), 32234433 (Boulder).

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

At midnight there were 4 spotted regions on the visible disk. Solar flare activity was moderate. A total of 9 C and 2 M class events was recorded during the day. A C1.5 flare at 17:43 UTC had its origin in region 10537 behind the northwest limb.

Region 10540 developed early in the day, then began to decay and had lost a large amount of penumbral area in the trailing spot section by the end of the day. The magnetic delta structures disappeared as well. Further M class flares are possible. Flares: C1.1 at 02:13, C1.7 at 02:31, C1.2 at 02:55, impulsive M1.0 at 05:32, M1.0 at 12:40, C8.2 (with an associated moderate type II radio sweep) and a long duration C5.7 event which began at 23:08 UTC and peaked at 00:45 on January 20. The C5 LDE was associated with a CME.
Region 10542 developed quickly and a weak magnetic delta structure emerged at the eastern end of the elongated intermediate penumbra. Minor M class flares are possible.
New region 10543 emerged east of region 10540 and developed quickly. Flare: C3.4 at 14:39 UTC.

Spotted regions not numbered by NOAA/SEC:
[S333] This region emerged quickly east of region 10542 on January 18 and developed further on January 19. Strangely SEC has failed to separate this region from 10542. M class flares are possible. Location at midnight: N08E21.

Coronal mass ejections (CMEs)

January 19/20: The long duration C5.7 event in region 10540 late on January 19 and early on January 20 was associated with a CME. A filament eruption at the southeast limb at the same time has greatly complicated the analysis of this event. LASCO C2 observed this CME first at 00:30 UTC on January 20 below the south pole and high latitude parts of the southern limbs. By 00:54 the CME was visible over the east limbs while, surprisingly, no trace of a CME could be seen off of the central west limb. Some ejected material was observed off of the northwest limb. It is possible that the filament eruption at and near the southeast limb contributed a major part of the ejected material observed over the east and south limbs. Currently I would say there is a fairly good chance of a CME impact at Earth on January 22. Further analysis could lower or increase that possibility.

January 18: The M1 flare in region 10540 early in the day was associated with a partial halo CME observed mostly off of the southern limbs and the south pole. It is uncertain if there are any earth directed parts of this CME.

January 17: The major M5 flare in region 10540 was associated with a partial halo CME observed off of the southern limbs and the south pole. It is uncertain if there are any earth directed parts of this CME.

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 (CH76) was in a geoeffective position on January 13-17.

Processed SOHO/EIT 284 image at 01:06 UTC on January 20. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on January 20 due to a high speed stream from coronal hole CH76. Quiet to unsettled is likely on January 21 while there is a possibility of active to major storm conditions on January 22-23 if the CME observed early on January 20 impacts Earth.

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 poor to fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Rafaela (Argentina). On the northwesterly EWE a few east coast US and Canadian stations were noted with rather weak signals].

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.