11th September


Solar activity reached high levels. Region 2158 (N16W06, Dkc/beta-gamma)
produced largest solar event of the period, an X1/2b flare (R3/Strong)
at 10/1745 UTC, along with associated Type II and Type IV radio sweeps,
a 10cm radio burst, and a full halo coronal mass ejection (CME).

While the 9 Sep CME, mentioned in previous discussions, is still
expected to arrive early in the day on 12 Sep, the latest analysis of
the WSA Enlil solar wind model indicated the CME associated with
yesterdayâ??s X1/2b flare is likely to have an Earthward component as
well. This second CME has an estimated speed near 1400 km/s and is
expected to pass the Earth’s magnetosphere mid to late day (universal
time) on 12 Sep.

Region 2158 exhibited a fairly pronounced ring of intermediate spots
surrounding the main leader spot, indicative of significant mixing and
instability, but has since shown signs of decay and reorganization of
these spots. Region 2157 (S14W18, Ekc/beta-gamma-delta) maintained its
delta magnetic configuration yet was fairly inactive during the period.
The remaining spot groups appeared to be stable and predominantly
inactive throughout the period.

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