Weekly Highlights of Solar and Geomagnetic Activity, 25 February - 03 March 2013

Weekly Highlights of Solar and Geomagnetic Activity, 25 February - 03 March 2013

Post by SWPC.Webmas.. » Tue, 05 Mar 2013 20:34:54

:Product: Weekly Highlights and Forecasts
:Issued: 2013 Mar 04 0205 UTC
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Highlights of Solar and Geomagnetic Activity
25 February - 03 March 2013

Solar activity was very low for most of the week, with only B-class
flares observed. The majority of the B-class activity was split
between Regions 1682 (S18, L=299, class/area=Dai/240 on 01 Mar) and
1683 (S16, L=202, class/area=Eai/210 on 02 Mar) both of which
developed beta-gamma magnetic characteristics during the week.
Activity increased to low levels on 02 Mar, when Region 1687 (N06,
L=166, class/area=Cro/30 on 03 Mar) produced a C1 flare at 1511 UTC
and again at 1847 UTC. All three of the regions mentioned remain on
the visible disk at the time of this report.

A greater than 10 MeV proton enhancement was observed from a long
duration B9 flare which occurred on 25 Feb at 1151 UTC and was
attributed to old Region 1678 (N11, L=069) which had rotated around
the West Limb two days earlier. The proton flux enhancement began on
27 Feb, reached a peak of 0.995 pfu at 28/0440 UTC, and returned to
background levels early on 01 Mar.

The greater than 2 MeV electron flux at geosynchronous orbit was at
low to moderate levels until 02 Mar when it rose to 3800 pfu in
response to the arrival of a significant coronal hole high speed
stream. Flux remained at high levels through the end of the period.

Geomagnetic field activity was quiet for most of the week. However,
on 28 Feb around 15-17 UTC, a corotating interaction region (CIR)
and subsequent high speed solar wind stream (HSS) became
geoeffective. Solar wind speed which had been in the mid 300 km/s
range began rising and eventually peaked at 675 km/s early on 02
Mar. Bt rose to 18 nT by 01/0817 UTC while Bz ranged from +14 to -16
nT. The Phi angle shifted from a positive (away) orientation to a
negative (towards) orientation. The magnetosphere responded with
unsettled levels late on 28 Feb. Geomagnetic activity quickly
climbed to active levels for most of 01 Mar, punctuated by one
period of minor storm levels during the 09-12 UTC synoptic period.
This response was no doubt exacerbated by the favorable orientation
described by the Russel-McPherron effect. Solar wind speed declined
abruptly between 02/11-15 UTC, dropping from about 590 to around 480
km/s, then began a slow decline back to around 400 km/s by the end
of the week. After an active first period on 02 Mar, the remainder
of the week saw quiet to unsettled activity levels.

Forecast of Solar and Geomagnetic Activity
04 March - 30 March 2013

Solar activity is expected to be very low to low with a slight
chance for an isolated M-class event. The threat of an M-class flare
is most probable between 11 and 23 Mar with the return of old Region
1675.

No proton events are expected at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to begin the period at high levels in response to the
continued presence of a recurrent coronal hole high speed stream but
decline to normal to moderate levels after 06 Mar. High levels are
possible again in the last day of the forecast period with the
return of a recurrent coronal hole high speed stream.

Geomagnetic field activity is expected to be pre***ly quiet to
unsettled. Active periods are possible on 28 March with the return
of a recurrent coronal hole high speed stream.