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Here is this week's space weather and geophysical report, issued 2015 Sep 21 0538 UTC.
Highlights of Solar and Geomagnetic Activity
14 - 20 September 2015
Solar activity was low from 14-16 Sep. Activity increased to
moderate levels on 17 Sep when Region 2415 (S19, L=233, class/area
Eac/240 on 19 Sep) produced an M1/Sf flare at 17/0940 UTC. A long
duration C2/Sf flare observed at 18/0631 UTC was accompanied by Type
II (850 km/s) and Type IV radio sweeps along with a coronal mass
ejection (CME). Low levels were observed on 18-19 Sep but returned
to moderate levels on 20 Sep. Region 2420 (N09, L=108, class/area
Ekc/270 on 20 Sep) produced an M1 at 20/0503 UTC as it rotated onto
the east limb. Region 2415 produced an M2/2n flare at 20/1803 UTC
accompanied by a Type II (1358 km/s) radio sweep as well as a 320
sfu Tenflare. An associated CME was observed in SOHO LASCO C2
imagery beginning at 20/1812 UTC and a WSA-Enlil model run is in
progress to determine geoeffectiveness.
No proton events were observed at geosynchronous orbit, however, an
enhancement was observed in conjunction with the M2 flare from 20
Sep with a peak flux of 3 pfu at 20/2045 UTC.
The greater than 2 MeV electron flux at geosynchronous orbit was at
moderate to high levels from 14-18 Sep due to a combination of
effects from a CME and coronal hole high speed stream (CH HSS)
influence. Normal to moderate levels were observed on 19-20 Sep.
Geomagnetic field activity was at quiet to minor storm levels on 14
Sep due to the onset of a recurrent, positive polarity CH HSS late
in the day. Quiet to active levels persisted from 15-17 Sep as HSS
influence continued. Quiet to unsettled conditions were observed on
18 Sep as CH HSS effects subsided. Predominately quiet to unsettled
levels were observed on 19 Sep with the exception of isolated active
and minor storm periods from 19/0300-0600 UTC and 19/0600-0900 UTC,
respectively, in response to a solar sector boundary change and a
prolonged period of negative Bz. A geomagnetic Sudden Impulse of 27
nT was observed at the Boulder magnetometer on 20 Sep at 0605 UTC
indicating the arrival of the 18 Sep CME. Unsettled to severe storm
conditions were subsequently observed and then were followed by the
onset of a recurrent, positive polarity CH HSS.
Forecast of Solar and Geomagnetic Activity
21 September - 17 October 2015
Solar activity is expected to be at low to moderate levels from 21
Sep - 02 Oct as Region 2420 makes its way across the visible disk.
Low levels are anticipated from 03-05 Oct. Low to moderate levels
are likely to return on 06 Oct when Region 2415 is expected to
rotate back into view and remain elevated through the end of the
forecast period (17 Oct).
No proton events are expected at geosynchronous orbit although a
slight chance exists from 21-22 Sep when Region 2415 rotates off of
the west limb and 06-17 Oct when it returns as it now has a history
of producing protons.
The greater than 2 MeV electron flux at geosynchronous orbit is
expected to be at moderate to high levels from 21-27 Sep due to
influence from various CME and CH HSS activity. Normal to moderate
levels are expected from 28 Sep to 01 Oct. Chances for high levels
return from 02-11 Oct due to effects from a series of recurrent,
positive polarity high speed streams. Predominately normal to
moderate levels are expected for the remainder of the period.
Geomagnetic field activity is expected to reach minor storm levels
early on 21 Sep due to waning effects of the 18 Sep CME and CH HSS
influence. Quiet to unsettled conditions are expected from 22-24 Sep
although analysis is ongoing to determine if and when the 20 Sep CME
will affect field activity. Unsettled to active levels are expected
from 25-26 Sep due to influence from a negative polarity CH HSS.
Quiet to unsettled conditions are expected from 27-30 Sep. A series
of recurrent positive polarity high speed streams are expected to
increase field activity to a baseline of unsettled to active
conditions from 01-09 Oct with minor storm levels likely on 01 Oct
and 05-06 Oct and major storm levels likely on 04 and 08 Oct during
peak influence as well as co-rotating interaction regions (CIRs)
preceding the onset of the individual streams. Quiet to unsettled
conditions are expected from 10-16 Oct with isolated active periods
possible during periods of sustained negative Bz as HSS influence
subsides. Unsettled to active levels are expected with a chance for
minor storm periods on 17 Oct due to positive polarity CH HSS
influence.
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![Weekly Propagation Summary - 2015 Sep 21 16:10 UTC]()
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