Solar Terrestrial Activity Report

Last major update issued on May 22, 2004 at 03:20 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 21. Solar wind speed ranged between 426 and 557 km/sec, slowly decreasing as the high speed stream from coronal hole CH96 weakened.

Solar flux measured at 20h UTC on 2.8 GHz was 106.9. The planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.9).
Three hour interval K indices: 33323322 (planetary), 33323323 (Boulder).

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

At midnight there were 4 spotted regions on the visible disk. The solar flare activity level was moderate. A total of 3 C and 1 M class events was recorded during the day.

Region 10613 was quiet. A small positive polarity spot emerged at the northwestern edge of the single penumbra.
Region 10615 was mostly quiet and stable. Flare: C1.2 at 22:20 UTC.
Region 10617 decayed slowly and was mostly quiet. Flare: C1.2 at 22:20 UTC.
Region 10618 developed quickly, particularly in the central part, and added many new spots. A magnetic delta structure in the central part of the region has become stronger and further minor M class flares are possible, even a major flare is becoming a possibility. Flares: C2.0 at 05:51 and M2.6 at 23:52 UTC.

Coronal mass ejections (CMEs)

May 19-21: 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, poorly defined coronal hole (CH97) in the northern hemisphere was in a geoeffective position on May 19-20.

Processed SOHO/EIT 284 image at 19:05 UTC on May 21. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on May 22-23 due to effects from a coronal hole flow. Quiet to unsettled is likely on May 24.

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 fair to poor. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela) with a weak signal most of the time, Radio Cristal del Uruguay was noted occasionally. Rádio Metropolitana (Brazil) had a good signal before 01h UTC. Propagation swung northwards after 01h UTC and most of the usual (540, 560, 590, 620, 640, 650, 710, 740, 750, 800 and 930 kHz) stations from Newfoundland became audible, as did a few Nova Scotia stations. From the USA WWZN on 1510 and WTOP on 1500 kHz had the best signals. Bahamas on 1540 kHz was unusually strong.

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
10609 2004.05.10 3   S02W88 0090 CAO rotated out of view
10613 2004.05.13 3 3 S09W28 0100 CSO beta-delta
classification was CAO
at midnight
10615 2004.05.16 1 5 N17W01 0100 HSX classification was CAO
at midnight
10616 2004.05.16     N07E04     plage
10617 2004.05.17 6 8 S11W46 0030 CRO classification was DRO
at midnight
10618 2004.05.20 19 44 S11E55 0150 CAI beta-gamma-delta
classification was EAC
at midnight, area 0260
Total spot count: 32 60
SSN: 82 100

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 98.9 (1) 51.4 (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.


[DX-Listeners' Club]