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  Weekly Space Weather Highlights
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Highlights of Solar and Geomagnetic Activity
10 - 16 July 2017

Solar activity was at very low levels on 12 Jul, low levels on 10,
11, 13, 15 and 16 Jul and moderate (R1-Minor) levels on 14 Jul.
Region 2665 (S06, L=111, class/area Ekc/710 on 09 Jul) produced a
majority of the flare activity. However, new Region 2667 (N12,
L=155, class/area Axx/010 on 14 Jul) produced all of the C-class
activity on 13 Jul including a C8 x-ray event with a Type II radio
emission (770 km/s). The largest event of the summary period was a
long-duration M2/1n flare from Region 2665 observed at 14/0209 UTC.
Associated with this event was a Tenflare (130 sfu) and Type IV
radio emission. At 14/0125 UTC, LASCO C2 imagery detected an
asymmetric halo CME that was analyzed and modelled to reveal an
Earth-directed component with a likely arrival at Earth on 16 Jul. 

A greater than 10 MeV at greater than or equal to 10 pfu proton
event (S1-Minor) began at 14/0900 UTC, reached a maximum flux of 22
pfu at 14/2320 UTC and ended at 15/1115 UTC. 

The greater than 2 MeV electron flux at geosynchronous orbit was at
moderate flux levels then entire summary period. A maximum flux of
942 pfu was observed at 14/1750 UTC. 

Geomagnetic field activity was at quiet to unsettled levels, with
isolated active intervals, on 10-11 Jul due to waning effects from a
positive polarity CH HSS. Solar wind speeds reached a peak of about
650 km/s early on 11 Jul and steadily decreased through the summary
period to reach a low speed of 287 km/s at 16/0446 UTC. Quiet levels
were recorded from mid-day 11 Jul through early on 16 Jul. 

At 16/0515 UTC, an interplanetary shock associated with the arrival
of the 14 Jul CME, was observed in DSCOVR solar wind data. Solar
wind speeds sharply increased from around 320 km/s to 502 km/s.
Solar wind speeds then slowly increased to a peak value of 643 km/s
observed at 16/2037 UTC. Total field strength values reached 28 nT
at 16/0836 UTC while the Bz component was sustained at around -23 nT
for a prolonged period following the shock arrival. Solar wind
density reached a peak of around 56 particles/cubic cm following the
shock and the phi angle became highly variable after 16/0515 UTC.
Phi angle settled into a mostly positive (away) solar sector after
16/1100 UTC. The geomagnetic field was quiet until 16/0601 UTC when
a geomagnetic sudden impulse was observed (40 nT at Hartland
magnetometer) indicating the arrival of the 14 Jul CME. The
geomagnetic field responded with active to G1 and G2 (Minor to
Moderate) geomagnetic storm levels through the remainder of 16 Jul. 

Forecast of Solar and Geomagnetic Activity
17 July - 12 August 2017

Solar activity is expected to be low with a chance for M-class flare
activity (R1-R2 / Minor-Moderate) through 19 Jul when Region 2665
exits the visible disk. Very low to low levels are expected from
20-28 Jul. A chance for R1-R2 activity is possible with the return
of old Region 2665 from 29 Jul - 12 Aug. 

There is a chance for an S1 (Minor) solar radiation storm through 19
Jul due to potential significant flare activity from Region 2665. No
proton events are expected from 20-28 Jul. A chance for S1 (Minor)
solar radiation storms is possible with the return of old Region
2665 from 29 Jul - 12 Aug. 

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to be reach high levels on 19-20 Jul due to influence from
the 14 Jul CME. Normal to moderate levels are expected for the
remainder of the outlook period. 

Geomagnetic field activity is expected to be at G1-G2
(Minor-Moderate) geomagnetic storm levels on 17 Jul due to continued
CME effects. Unsettled to active levels are expected on 21-22 Jul
and again on 05-06 Aug, with G1 (Minor) geomagnetic storm levels
likely on 05 Aug, due to positive polarity CH HSS influence. Quiet
to unsettled levels are expected for the remainder of the outlook
period.