Solar Terrestrial Activity Report

Last update issued on May 17, 2003 at 03:30 UTC.

[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update May 1, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update May 1, 2003)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update May 1, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update April 13, 2003)]
[Archived reports (last update May 12, 2003)]

Recent activity

The geomagnetic field was quiet to unsettled on May 16. Solar wind speed ranged between 504 and 656 km/sec, the high speed stream from coronal hole CH38 ended early in the day.

Solar flux measured at 20h UTC on 2.8 GHz was 102.6. The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 10.5).
Three hour interval K indices: 32222233 (planetary), 32222322 (Boulder).

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

At midnight there were 5 spotted regions on the visible disk. Solar flare activity was very low.

Region 10356 decayed further. If the region continues to decay at the current rate, no spots will be visible by tomorrow.
Region 10357 developed slowly and quietly.
Region 10358 decayed and lost all spots outside of the main penumbra.
Region 10361 decayed and could soon become spotless.
Region 10362 was mostly unchanged and quiet.

Coronal mass ejections (CMEs)

May 14-16: No obviously geoeffective 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 recurrent trans equatorial coronal hole (CH39) was in a geoeffective position on May 15-16. A recurrent trans equatorial coronal hole (CH40) will rotate into a geoeffective position on May 18-20.

Processed SOHO EIT 284 image at 19:06 UTC on May 16. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on May 17. A high speed stream from coronal hole CH39 will likely reach Earth on May 18 and cause unsettled to active geomagnetic conditions that day and on May 19. A high speed stream from coronal hole CH40 is expected to influence the field May 21-24. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor and will likely be very poor until at least May 25. Propagation along north-south paths is fair to good and is likely to be at least fair until May 25. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay.]

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.
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 SEC/NOAA. 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.

Solar region Date numbered SEC
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
10356 2003.05.09 10 2 N18W29 0030 CSO  
10357 2003.05.11 4 6 S17E07 0050 DAO  
10358 2003.05.12 3 1 N08W30 0030 CSO classification was HSX
at midnight
10359 2003.05.12 2   S14W75 0020 AXX spotless
10360 2003.05.14     S05W47     plage
10361 2003.05.15 7 2 N08E25 0030 HSX classification was AXX
at midnight, area 0010
10362 2003.05.15 11 13 S11E64 0240 DAO area was 0130
at midnight
S158 emerged on
2003.05.14
    S10W72     now spotless
Total spot count: 37 24
SSN: 97 74

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)
2002.04 189.8 120.7 110.5 (-2.9)
2002.05 178.4 120.8 108.8 (-1.7)
2002.06 148.7 88.3 106.2 (-2.6)
2002.07 173.5 99.6 102.7 (-3.5)
2002.08 183.6 116.4 98.7 (-4.0)
2002.09 175.8 109.6 94.6 (-4.1)
2002.10 167.0 97.5 90.5 (-4.1)
2002.11 168.7 95.5 (84.9 predicted, -5.6)
2002.12 157.2 80.8 (80.5 predicted, -4.4)
2003.01 144.0 79.5 (77.5 predicted, -3.0)
2003.02 124.5 46.2 (72.4 predicted, -5.1)
2003.03 131.4 61.5 (66.8 predicted, -5.6)
2003.04 126.4 60.0 (61.9 predicted, -4.9)
2003.05 113.3 (1) 50.0 (2) (57.9 predicted, -4.0)

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 (SEC/NOAA) sunspot number. The official international sunspot number is typically 25-45% less.

This report has been prepared by Jan Alvestad. It is based partly on my own observations and interpretations, 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]