Solar Terrestrial Activity Report

Last update issued on June 1, 2003 at 02:30 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 26, 2003)]

Recent activity

The geomagnetic field was quiet to minor storm on May 31. Solar wind speed ranged between 555 and 775 km/sec. 

Solar flux measured at 20h UTC on 2.8 GHz was 113.1. The planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 19.8).
Three hour interval K indices: 55313322 (planetary), 46322322 (Boulder).

The background x-ray flux is at the class B5 level.

An above 10 MeV proton event peaked at 27 pfu at 06:45 UTC. The source of this event was the M9 flare in region S169 earlier in the day.

At midnight there were 4 spotted regions on the visible disk. Solar flare activity was high. A total of 6 C and 1 M class events was recorded during the day. A C1.0 flare at 20:34 UTC had its origin in a region just behind the northeast limb. This region produced a C3.8 flare at 00:51 UTC on June 1 as well and may be capable of minor M class flaring.

Region 10368 decayed quickly and could become spotless today or tomorrow.
Region 10373 developed slightly as new small spots emerged. Flare: C3.5 at 00:29 UTC.

Spotted regions not numbered or misnumbered by NOAA/SEC:
[S169] This region emerged very quickly after noon on May 24 in the southeast quadrant about 11 degrees longitude east of spotless region 10365. The region continued to develop quickly as a compact region on May 25-28. On May 29-31 the region decayed slowly losing penumbral area and spots. Major flares are still possible as there is a magnetic delta structure in the trailing part of the region. Location at midnight: S07W72. Flares: M9.3/2B (associated with a strong type II radio sweep) at 02:24, C1.3 at 14:16, C3.5 at 15:33 and C1.3 at 23:11 UTC.
[S175] A new region emerged in the northeast quadrant on May 31. The region was decaying late in the day and could soon become spotless. Location at midnight: N14E15.

Coronal mass ejections (CMEs)

May 30: No obviously geoeffective CMEs observed.

May 31: A halo CME was observed in LASCO C2 images after the M9 flare in region S169 early in the day. This CME could reach Earth late on June 1 or early on June 2. As a high speed stream is likely to be dominating the solar wind at that time, it is uncertain how much, if anything, the CME will add to the geomagnetic disturbance.

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 huge recurrent coronal hole (CH42) in the southern hemisphere will rotate into a geoeffective position on May 29-June 6. This coronal hole has a narrow leading extension into the northern hemisphere.

Processed SOHO EIT 284 image at 19:06 UTC on May 31. Any black areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be unsettled to minor storm until June 9 due to a high speed stream from coronal hole CH42 arriving on June 1.

Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is useless and will likely be very poor to useless until at least June 10. Propagation along north-south paths is poor to very poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: none, Radio Cristal del Uruguay was heard at times, as was an unidentified station from Brasil.]

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 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.

Solar region Date numbered SEC
Location at midnight Area Classification Comment
10365 2003.05.20 22   S08W80
0540 DKC location corrected
the region is spotless,
SECs spots belong to
region S169.
10366 2003.05.22     N11W55     plage
10367 2003.05.22     S14W48     plage
10368 2003.05.22 4 2 S33W38 0020 CRO classification was HSX
at midnight
10370 2003.05.23     N16W52     plage
10371 2003.05.27     S13W62     plage
10372 2003.05.27     S14W55     plage
10373 2003.05.27 1 6 N08E28 0110 CSO  
S169 emerged on
  31 S07W72 0400 DKC beta-gamma-delta
(see region 10365)
S171 emerged on
    S23W37     plage
S172 emerged on
    S17W18     plage
S173 emerged on
    N05E05     plage
S174 emerged on
    N18W14     plage
S175 emerged on
  2 N14E15 0000 AXX  
Total spot count: 27 41
SSN: 57 81

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)
2003.05 115.7 (1) 89.9 (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 (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 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]