Solar Terrestrial Activity Report

Last major update issued on February 20, 2004 at 03:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update February 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update February 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update February 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2003 (last update January 16, 2004)]
[Archived reports (last update February 18, 2004)]

Recent activity

The geomagnetic field was quiet to slightly unsettled on February 19. Solar wind speed ranged between 382 and 539 km/sec, slowly decreasing all day.

Solar flux measured at 20h UTC on 2.8 GHz was 96.4. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 6.6).
Three hour interval K indices: 21112321 (planetary), 32112222 (Boulder).

The background x-ray flux is at the class B1 level.

At midnight there were 4 spotted regions on the visible disk. Solar flare activity was very low. No C class events was recorded during the day. 

Region 10554 decayed slowly and rotated to the southwest limb. quietly.
Region 10561 was quiet and stable.
New region 10562 rotated into view at the southeast limb.

Spotted regions not numbered by NOAA/SEC:
[S360] This region rotated into view at the southeast limb south of region 10562 on February 19. Location at midnight: S24E75.

Coronal mass ejections (CMEs)

February 17-19: No partly or fully earth directed CMEs observed.

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 small coronal hole (CH81) in the southern hemisphere was in a geoeffective position on February 17.

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

Forecast

The geomagnetic field is expected to be mostly quiet to unsettled until February 24. On February 20 there is a possibility of a weak high speed stream arriving from coronal hole CH81, this could cause unsettled to active conditions during parts of that day.

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor and slowly improving. Propagation along long distance north-south paths is poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay with a weak to fair signal on the southwesterly longwire. On the northwesterly EWE Radio Vibración (Venezuela was noted with a weak signal. Using that antenna several stations from Newfoundland, Nova Scotia and New Brunswick were audible, as were a few of the most common east coast US stations].

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
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
10554 2004.02.07 1 1 S08W83 0060 HSX  
10555 2004.02.09     S16W61     plage
10556 2004.02.11     N17W84
(SEC:
N15W93)
    plage
SEC has moved region
10556 to the position
of region S354
10558 2004.02.13     S16W45     plage
10560 2004.02.15     S17W22     plage
10561 2004.02.15 1 2 N02E12 0030 HSX  
10562 2004.02.19 1 2 S11E73 0010 AXX classification was CSO
at midnight
S357 emerged on
2004.02.17
    N10W51     plage
S358 emerged on
2004.02.18
    S06E12     plage
S359 emerged on
2004.02.18
    S14E14     plage
S360 visible on
2004.02.19
  1 S24E75 0020 HRX  
Total spot count: 3 6
SSN: 33 46

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)
2003.01 144.0 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 65.0 (-2.6)
2003.07 127.7 83.3 61.8 (-3.2)
2003.08 122.1 72.7 (59.4 predicted, -2.4)
2003.09 112.2 48.7 (57.6 predicted, -1.8)
2003.10 151.7 65.5 (54.9 predicted, -2.7)
2003.11 140.8 67.3 (52.2 predicted, -2.7)
2003.12 114.9 46.5 (49.6 predicted, -2.6)
2004.01 114.1 37.2 (45.4 predicted, -4.2)
2004.02 105.7 (1) 48.5 (2) (40.8 predicted, -4.6)

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]