Solar Terrestrial Activity Report

Last major update issued on January 1, 2004 at 05:10 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update December 2, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update December 2, 2003)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update December 2, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update October 15, 2003)]
[Archived reports (last update December 30, 2003)]

Recent activity

The geomagnetic field was quiet to minor storm on December 31. Solar wind speed ranged between 410 and 565 km/sec under the influence of a high speed stream from coronal hole CH73.

Solar flux measured at 20h UTC on 2.8 GHz was 105.6. The planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 17.3).
Three hour interval K indices: 32234543 (planetary), 32233533 (Boulder).

The background x-ray flux is at the class C1 level.

At midnight there was 1 spotted region on the visible disk. Solar flare activity was moderate. A total of 4 C and 1 M class events were recorded during the day. A very active region is about to rotate into view at the southeast limb. This region is likely to be complex and could produce multiple M class events. The following events were recorded on December 31: C2.3 at 17:33, C2.2 at 18:08, C1.0 at 20:19 and a long duration C8.3 event peaking at 22:17 UTC. The LDE was associated with a CME off of the central east limb. Region 10528 behind the west limb produced a very impulsive M1.0 flare at 18:24 UTC - the total duration of the flare was only 5 minutes.

New region 10534 emerged in the southeast quadrant. C class flares are possible.

Coronal mass ejections (CMEs)

December 29-31: No partly or fully earth directed CMEs observed. Only a few new LASCO images were published on December 29 and 31, with no new images on December 30.

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 (CH73) was in a geoeffective position on December 28-29. A large, recurrent trans equatorial coronal hole (CH74) will probably be in a geoeffective position January 1-7.

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


The geomagnetic field is expected to be unsettled to minor storm on January 1 under the influence of a high speed stream from coronal hole CH73. Quiet to unsettled is likely on January 2-3 with unsettled to minor storm expected from January 4 as a high speed stream from coronal hole CH74 dominates the solar wind.

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 good. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: None, a large number of stations from Brazil was noted on this and other frequencies, many with good signals. Rádio Nacional in Brasilia on 980 kHz had an S90+20dB signal].

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)
Coronal hole indicator CME indicator M and X class flare indicator

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.

Active region Date numbered SEC
Location at midnight Area Classification Comment
10528 2003.12.18 3   N09W93 0120 CAO rotated out of view
10530 2003.12.21     S22W67     plage
10532 2003.12.25     S12W77     plage
10533 2003.12.28     N16E12     plage
10534 2003.12.31 2 11 S05E40 0010 BXO classification was DSO
at midnight, area 0050
Total spot count: 5 11
SSN: 25 21

Monthly solar cycle data

Month Average solar
flux at Earth
International sunspot number Smoothed sunspot number
2000.04 184.2 125.5 120.8
cycle 23 sunspot max.
2000.07 202.3 170.1 119.8
2001.12 235.1 132.2 114.6 (-0.9)
2002.11 168.7 95.5 85.2 (-5.3)
2002.12 157.2 80.8 82.0 (-3.2)
2003.01 144.0 79.7 80.8 (-1.2)
2003.02 124.5 46.0 78.3 (-2.5)
2003.03 131.4 61.1 74.0 (-4.3)
2003.04 126.4 60.0 70.1 (-3.9)
2003.05 115.7 55.2 67.6 (-2.5)
2003.06 129.3 77.4 (65.1 predicted, -2.5)
2003.07 127.7 83.3 (61.8 predicted, -3.3)
2003.08 122.1 72.7 (58.8 predicted, -3.0)
2003.09 112.2 48.7 (56.9 predicted, -1.9)
2003.10 151.7 65.6 (54.1 predicted, -2.8)
2003.11 140.8 67.2 (51.4 predicted, -2.7)
2003.12 114.9 (1) 76.1 (2) (48.9 predicted, -2.5)

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.

[DX-Listeners' Club]