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FXXX12 KWNP 030031

:Product: Forecast Discussion
:Issued: 2015 Sep 03 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 continued at very low levels with only an optical
subflare noted from slowly decaying Region 2407 (N17W87, Cso/beta) as it
neared the limb. Region 2409 (N04E39, Dro/beta) showed no additional
development and was stable and inactive. The regions magnetic field
structure remained in a simple bipolar configuration with no significant
shear or perceptible field line tension. The remaining regions underwent
further decay or were stable.

Analysis of STEREO-Ahead EUV imagery of the far-side of the Sun revealed
a small active region (AR) rotating towards the NE limb of the
Earth-facing side. This hints that the 10.7 cm flux may increase
slightly in a few days, while the overall flare potential is likely to
remain very low.

A coronal mass ejection (CME) from the NW limb was first noted in
available SOHO/LASCO-C2 imagery at 02/1325 UTC, however analysis of
available SDO/AIA and GONG/H-alpha imagery suggests this was on the
Suns far-side. No Earth-directed CMEs were observed in available
coronagraph imagery.

Solar activity is expected to remain very low with a slight chance for
C-class flares all three days (03-05 Sep) primarily due to the flare
probability from Region 2409.

Energetic Particle

.24 hr Summary...
The greater than 2 MeV electron flux was at normal to high levels with a
maximum flux of 2790 pfu at 02/1515 UTC. A decrease in electrons from
high levels to normal levels occurred between 02/0100-0300 UTC in
conjunction with a weak transient feature noted in ACE data. The greater
than 10 MeV proton flux was at background levels.

The greater than 2 MeV electron flux is expected to be at normal to
moderate levels on days one and two (03-04 Sep) as a coronal hole high
speed stream (CH HSS) has become geoeffective. The 2 MeV electron flux
may see increased levels of normal to high on day three (05 Sep) as the
CH HSS effects begin to wane. The greater than 10 MeV proton flux is
expected to continue at background levels.

Solar Wind

.24 hr Summary...
The solar wind and interplanetary magnetic field (IMF) parameters
reflected ambient conditions until about 02/0030 UTC when a weak
transient feature was evident at ACE, as the total field strength
increased from about 6 nT to 9 nT. Solar wind velocities also increased
in conjunction with the transient feature, from around 350 km/s to near
400 km/s by about 02/0700 UTC. Density also reflected an increase and
decrease with the transient passage. Total magnetic field strength
slowly decreased afterwards and solar wind speeds ranged between 375-400
km/s until the expected solar sector boundary crossing (SSBC),
co-rotating interaction region (CIR), and CH HSS were noted in the ACE
data beginning at about 02/1522 UTC when the phi angle changed from
negative (towards the Sun) to positive (away). This was followed by
reflection of a weak CIR and eventual connection with a positive
polarity CH HSS. Solar wind velocities increased to about 425 km/s
beginning at about 02/1650 UTC as Earth connected with the CH HSS, and
remained fairly steady afterwards. Total magnetic field strength
increased from 3-5 nT to about 8 nT and density increased as the CIR
passed ACE. The Bz component was variable, but primarily in a northward
orientation until the SSBC and CIR passage, when the Bz became primarily
negative from -1 to -5 nT. The phi angle remained positive after the

The positive polarity CH HSS solar wind velocities were lower than
expected this rotation, resulting in a weaker than expected CIR. Solar
wind speeds are expected to continue at higher than ambient levels for
the next two days (03-04 Sep) before beginning to wane as Earth begins
to exit the CH HSS on day three (05 Sep).


.24 hr Summary...
The geomagnetic field was quiet until the 02/1800-2100 UTC synoptic
period when the Earths magnetosphere reacted to unsettled levels due to
the disturbed and enhanced solar wind and IMF environment from the CIR
and CH HSS.

The geomagnetic field is expected to have periods of unsettled to active
conditions on day one (03 Sep) due to CH HSS influences. Day two (04
Sep) is expected to see quiet to unsettled conditions as the CH HSS
effects continue. Day three (05 Sep) is expected to be mostly quiet,
with a few unsettled periods as CH HSS effects begin to wane. is the U.S. government's official web portal to all federal, state and local government web resources and services.