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  Weekly Space Weather Highlights
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Highlights of Solar and Geomagnetic Activity
17 - 23 April 2017

Solar activity reached low levels on 17-18 Apr due to isolated
C-class flare activity from Region 2651 (N12, L=070,
class/area=Cso/150 on 23 Apr), but solar activity was at very low
levels through the remainder of the period (19-23 Apr). The largest
event of the period, a long-duration C5/Sf flare at 18/2010 UTC with
both Type-II and IV radio emissions, had an associated CME that was
observed in C2 coronagraph imagery beginning at 18/1948 UTC. CME
analysis and WSA-Enlil modelling suggested that this event did not
have an Earth-directed component, however, it is likely that this
event reached Earth late on 21 Apr. No other Earth-directed CMEs
were observed. 

No proton events were observed at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit reached
high levels on 17-18, 21-23 Apr, moderate levels on 20 Apr, and
normal levels on 19 Apr. 

Geomagnetic field activity was quiet on 17 Apr and quiet to
unsettled on 18 Apr under a nominal solar wind regime. The influence
of a recurrent, positive polarity CH HSS caused periods of G1
(Minor) geomagnetic storm conditions on 19 Apr and G1-G2
(Minor-Moderate) storm conditions on 20 Apr. The likely arrival of a
CME (from 18 Apr) combined with the onset of a CIR caused G1 (Minor)
geomagnetic storm levels late on 21 Apr. The influence of a
recurrent, negative polarity CH HSS began early on 22 Apr and caused
G1-G2 (Minor-Moderate) geomagnetic storms on 22-23 Apr. 

Forecast of Solar and Geomagnetic Activity
24 April - 20 May 2017

Solar activity is expected to be very low with a chance for C-class
flare activity throughout the outlook period (24 Apr-20 May). 

No proton events are expected at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit is
likely to reach very high levels on 29-30 Apr with high levels
likely on 24-28 Apr and 06-12, 17-20 May. Normal to moderate flux
levels are expected for the remainder of the period. 

Geomagnetic field activity is likely to reach G2 (Moderate)
geomagnetic storm levels on 19-20 May with G1 (Minor) geomagnetic
storms likely on 24-27 Apr and 01, 17-18 May due to the influence of
multiple, recurrent CH HSSs. Active conditions are likely on 28 Apr
and 05-06, 16 May with quiet or quiet to unsettled field activity
expected for the remainder of the period.