Routine Space Environment Product Issued Weekly
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:Product: 7-day Space Weather Highlights
:Issued: 2017 Sep 18 0327 UTC
# Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center
# Product description and SWPC contact on the Web
# http://www.swpc.noaa.gov/wwire.html
#
#                7-day Space Weather Highlights
#
Highlights of Solar and Geomagnetic Activity
11 - 17 September 2017

Solar activity was at predominately very low levels through the
summary period, interupted by a brief period of low activity on 12
Sep as Region 2680 (N09, L=317, class/area Hsx/140 on 12 Sep)
produced a pair of impulsive C-class flares. 11 Sep saw the X-ray
background elevated at the C-level due to slow decay from the X8
flare (R3-Strong) observed at 10/1606 UTC. No Earth-directed CMEs
were detected during the period.

Of note, two halo CMEs were observed on 17 Sep. The first one, a
full-halo CME, was first observed in LASCO C2 imagery at 17/1224
UTC, while the second one was a partial-halo CME, first observed in
LASCO C2 imagery at 17/1424 UTC. The source region of both CMEs was
determined to be from old active Region 2673 (S09, L=119) which is
presently on the back side of the solar disk. Old Region 2673 is due
to return on 23 Sep.

10 MeV and 100 MeV protons at geosynchronous orbit exceeded their
respective event thresholds during the period, both in response to
the X8 flare observed on 10 Sep. At 10/1645 UTC, 10 MeV protons
exceeded 10 pfu (S1-Minor), reached a maximum of 1,490 pfu
(S3-Strong) and decayed below the S1 level at 14/1725 UTC. The 100
MeV proton flux exceeded the 1 pfu level at 10/1625 UTC, reached a
maximum of 68 pfu at 10/2215 UTC and ended at 13/0335 UTC.

The greater than 2 MeV electron flux at geosynchronous orbit was at
moderate levels on 13-14 Sep and high levels on 11-12 and 15-17 Sep.
A maximum of 46,263 pfu was observed at 17/1610 UTC.

Geomagnetic field activity was a quiet to minor storm levels
(G1-Minor) and major storm levels (G2-Moderate) during the summary
period. Quiet to unsettled levels were observed on 11 Sep through
late on 12 Sep due to waning effects from a negative polarity CH
HSS. Late on 12 Sep through midday on 13 Sep, field activity
increased to active to minor storm levels (G1-Minor) in response to
CME effects from the 10 Sep X8 flare. During this timeframe, total
field peaked at 16 nT, the Bz component reached a maximum southward
extent of -12 nT and solar wind speed peaked at about 650 km/s.
Quiet levels were observed for the remainder of 13 Sep through
midday on 14 Sep.

From midday on 14 Sep through 17 Sep, field activity was dominated
by effects from a recurrent, positive polarity CH HSS. Unsettled to
G1-Minor and G2-Moderate levels were observed through 16 Sep with
quiet to active levels present on 17 Sep. During this timeframe,
total field peaked at near 22 nT, the Bz component reached a maximum
southward extent of -18 nT and solar wind speed peaked at about 775
km/s.



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