Solar Terrestrial Activity Report

Last major update issued on May 28, 2004 at 04:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update May 3, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update May 3, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update May 3, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update April 28, 2004)]
[Archived reports (last update May 18, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on May 27. Solar wind speed ranged between 330 and 423 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 101.8. The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 7.4).
Three hour interval K indices: 11322221 (planetary), 22221011 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight there were 2 spotted regions on the visible disk. The solar flare activity level was low. A total of 2 C class events was recorded during the day. Region 10619 at the southwest limb was the source of a C1.0 flare at 09:13 UTC.

Region 10615 was quiet and stable and is rotating over the northwest limb.
Region 10618 decayed in central spot section while slow development was observed in the leading spot section. Flare: C1.1 at 00:27 UTC.

Coronal mass ejections (CMEs)

May 25-27: No fully or partly Earth directed CME 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 recurrent elongated coronal hole (CH98) in the northern hemisphere will likely be in a geoeffective position on May 25-29. A recurrent trans equatorial coronal hole (CH99) will probably rotate to a geoeffective position on May 31.

Processed SOHO/EIT 284 image at 01:05 UTC on May 28. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on May 28-June 1 due to effects from coronal hole CH98.

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.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor to fair. Propagation along long distance north-south paths is fair. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay early in the night, Radio Vibración (Venezuela) after 02h UTC. At and just after local sunrise (02:45 UTC) several stations from Brazil were noted on 1570 (Rádio Asa Branca), 1580 and 1590 kHz. Before local sunrise several stations from the easternmost parts of North America were audible. In addition to the usual Newfoundland stations I logged WBBR 1130, WJAE 1440, WTOP 1500 and WWZN 1510 kHz.

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
10615 2004.05.16 2 1 N17W80 0070 HAX  
10616 2004.05.16     N07W74     plage
10618 2004.05.20 40 33 S10W27 0330 FAC beta-gamma
classification was FSI
at midnight, area 0230
location: S09W30
10619 2004.05.23   S09W89 plage
10620 2004.05.23   S15W16     plage
S406 emerged on
2004.05.24
    S14W30     plage
Total spot count: 42 34
SSN: 62 54

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)
2003.04 126.4 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 60.0 (-1.8)
2003.09 112.2 48.7 59.5 (-0.5)
2003.10 151.7 65.5 58.1 (-1.4)
2003.11 140.8 67.3 (56.5 predicted, -1.6)
2003.12 114.9 46.5 (53.5 predicted, -3.0)
2004.01 114.1 37.2 (49.1 predicted, -4.4)
2004.02 107.0 46.0 (44.8 predicted, -4.3)
2004.03 112.0 48.9 (42.1 predicted, -2.7)
2004.04 101.2 39.3 (40.0 predicted, -2.1)
2004.05 99.8 (1) 70.0 (2) (36.8 predicted, -3.2)

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.


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