Solar Terrestrial Activity Report

Last major update issued on October 31, 2004 at 04:40 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update October 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update August 28, 2004)]
[Archived reports (last update October 30, 2004)]

Recent activity

The geomagnetic field was quiet to active on October 30. Solar wind speed ranged between 361 and 458 km/sec under the influence of a fairly low speed stream from coronal hole CH121.

Solar flux measured at 17h UTC on 2.8 GHz was 136.4. The planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 16.9).
Three hour interval K indices: 44343323 (planetary), 44342323 (Boulder).

The background x-ray flux is at the class B6 level.

At midnight there were 8 spotted regions on the visible solar disk. The solar flare activity level was high. A total of 16 C, 4 M and 1 X class events was recorded during the day.

Region 10687 decayed further and was mostly quiet. Flare: C1.8 at 18:20 UTC.
Region 10689 decayed slowly and quietly.
Region 10690 decayed slowly and quietly.
Region 10691 developed new trailing spots. The negative polarity area inside the predominantly positive polarity leading penumbra decreased in area. While there is still a magnetic delta structure, that structure is not nearly as strong as it was just one day ago. Occasional minor M class flares are possible. Flares: C9.7 at 00:49 (with a weak associated type II radio sweep), C1.6 at 02:16, M3.3 at 03:33 (associated with a moderate type II radio sweep), C1.2 at 04:16, C1.1 at 05:55, M4.2 at 06:18 (associated with a moderate type II radio sweep), C5.5 at 07:01, C1.6 at 08:58, M3.7/1N (associated with a weak type II radio sweep) at 09:28, C7.2 at 10:35, C1.0 at 11:22, X1.2 (associated with a moderate type II and a weak type IV radio sweep) at 11:46, C3.7 at 12:51, C1.5 at 13:50, C2.6 at 14:06, C2.6 at 14:48, C1.4 at 15:54, M5.9 (associated with a weak type II radio sweep) at 16:33, C1.1 at 21:35 and C2.4 at 21:59 UTC.
Region 10692 decayed further and could become spotless today.
Region 10693 developed many new intermediate spots and is capable of producing a major flare.
Region 10694 decayed and could become spotless today.
New region 10695 rotated into view at the southeast limb on October 29 and was numbered by SEC one day later.

Coronal mass ejections (CMEs)

October 30: Several CMEs are likely to reach Earth. Unfortunately LASCO images were not available for the parts of the day when flaring in region 10691 was most intense. With images back in the afternoon only a single full halo CME was observed, this was after the major M5.9 event. Several of the other significant events are likely to have been associated with CMEs that will reach Earth on November 1 and 2.
October 28-29
: No obviously Earth directed CMEs observed.
October 27: A faint, slow, full halo CME was observed in LASCO C3 images beginning at 13:42 UTC. The origin of this CME may have been in region 10691 around 09h UTC. This was the only significant frontside activity that can be related to the CME. If the CME was frontsided it could reach Earth on October 31.

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 coronal hole (CH121) in the southern hemisphere was in a geoeffective position on October 25-26. A trans equatorial coronal hole (CH122) will rotate into a geoeffective position on October 30-31.

Processed SOHO/EIT 284 image at 01:06 UTC on October 31. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on October 31 and unsettled to severe storm on November 1 and 2 due to effects from CMEs reaching Earth.

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.


Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) and Radio Cristal del Uruguay. At 23h UTC only a single station could be heard with a very weak signal, CJYQ on 930 kHz. Four hours later that station had a strong S9 signal and several other stations from North America were audible as well, mainly form Newfoundland, Boston and New York.

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
10687 2004.10.19 4 5 N12W66 0090 HAX classification was CAO
at midnight, area 0060
10689 2004.10.21 1 1 N12W43 0020 HSX area was 0030
at midnight
10690 2004.10.22 6 5 N01W27 0040 CSO classification was CAO
at midnight, area 0050
10691 2004.10.23 24 21 N14W25 0200 FAO beta-gamma-delta
area was 0330
at midnight
10692 2004.10.24 2 1 S19W54 0000 AXX  
10693 2004.10.27 29 37 S16E34 0530 EHI beta-gamma
classification was EKI
at midnight, area 0740
10694 2004.10.28 5 4 N15W06 0020 CSO classification was AXX
at midnight, area 0010
10695 2004.10.30 2 6 S15E68 0100 DAO formerly region S468
area was 0070
at midnight
S467 emerged on
    S08W65     plage
Total spot count: 73 80
SSN: 153 160

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)
2003.08 122.1 72.7 60.0 (-1.7)
2003.09 112.2 48.7 59.5 (-0.5)
2003.10 151.7 65.5 58.2 (-1.3)
2003.11 140.8 67.3 56.7 (-1.5)
2003.12 114.9 46.5 54.8 (-1.9)
2004.01 114.1 37.3 52.0 (-2.8)
2004.02 107.0 45.8 49.3 (-2.7)
2004.03 112.0 49.1 47.1 (-2.2)
2004.04 101.2 39.3 (44.6 predicted, -2.5)
2004.05 99.8 41.5 (40.9 predicted, -3.7)
2004.06 97.4 43.2 (38.0 predicted, -2.9)
2004.07 119.1 51.0 (36.2 predicted, -1.8)
2004.08 109.6 40.9 (34.6 predicted, -1.6)
2004.09 103.1 27.7 (32.8 predicted, -1.6)
2004.10 104.8 (1) 72.7 (2) (30.5 predicted, -2.3)

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 some of these solar data sources. All time references are to the UTC day. Comments and suggestions are always welcome.

[DX-Listeners' Club]