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FXXX12 KWNP 270032

:Product: Forecast Discussion
:Issued: 2017 Jul 27 0030 UTC
# Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center
# Product description and SWPC contact on the Web
#             Forecast Discussion
Solar Activity

.24 hr Summary...
Solar activity was very low and the disk became void of spot groups as
Region 2668 (N03W41) decayed to plage. No Earth-directed CMEs were
observed in available coronagraph imagery.

Solar activity is expected to remain very low all three days (27-29
July) due to a spotless Sun, no anticipated returning regions, nor any
noteworthy approaching active region signatures in STEREO-A EUV

Energetic Particle

.24 hr Summary...
The greater than 2 MeV electron flux was predominantly at high levels,
with a short-duration redistribution to normal to moderate levels early
in the period. The greater than 2 MeV electrons reached a maximum flux
of 13,961 pfu at 26/1545 UTC. The greater than 10 MeV proton flux was at
background values.

The greater than 2 MeV electron flux is expected to continue at
primarily high levels all three days (27-29 July) due to continuing
particle influx from CH HSS influences. The greater than 10 MeV proton
flux is expected to remain at background levels all three days.

Solar Wind

.24 hr Summary...
Solar wind parameters remained indicative of a continued CH HSS regime.
Total IMF strength was variable and ranged primarily from 4 to 7 nT. The
Bz component underwent a short period of sustained southward direction
during the 26/0600-0900 UTC synoptic period. Solar wind speed unsteadily
decreased from around 650 km/s early in the period to end-of-period
speeds near 525 km/s. The phi angle was predominantly in a positive
sector, but did undergo some early period sector shifts.

Solar wind is anticipated to continue at elevated, but unsteadily
weakening speeds on day one (27 Jul) as positive polarity CH HSS
influences are likely to continue. WSA-Enlil ambient runs suggest Earth
will remain effected by the southern flank of the north polar CH HSS
through day one before beginning to rotate away from a geoeffective
position on day two (28 Jul). This seems a reasonable solution,
therefore solar wind speed is likely to continue decreasing on day two
and approach approach background-ambient like speeds by day three (29


.24 hr Summary...
The geomagnetic field was quiet to unsettled, with an active period
during the 26/0600-0900 UTC synoptic period; likely due to the higher
solar wind speeds and period of favorable IMF orientation.

The geomagnetic field is expected to be mostly quiet with isolated
unsettled periods on days one and two (27-28 Jul) due to continuing, but
weakening CH HSS influences. Day three (29 Jul) is expected to be quiet
as the CH HSS rotates away from a geoeffective position. is the U.S. government's official web portal to all federal, state and local government web resources and services.