[Scan-DC] Propagation Update-Resend

[Rapbep@aol.com]

All,

Got this from another list.  Sorry the first one didn't work.



RON
ANNE ARUNDEL COUNTY, MD (NEAR BWI)
Pro-2045/BC-895XLT w/Discone

Folks:

What an exciting time for radio enthusiasts!=A0 This past weekend's media hy=
pe=20
about a major geomagnetic and solar storm was unfortunate and unwarranted.=
=A0=20
But,=20
today, solar events have occurred that has the whole propagation science=20
community buzzing.

I just finished talking with Mike Weaver from the National Ocean and=20
Atmospheric=20
Administration Space and Environment Center (NOAA SEC).=A0 He is the Solar=20
Forecaster that has been on duty for the last four days.=A0 Last week, I als=
o=20
spoke with Bill Murtagh, who is beginning a shift to cover the next few=20
days.=A0=20
Our discussion focused on today's events, and what will transpire over the=20
next=20
few days.=A0 The following is my perspective of current solar and geophysica=
l=20
conditions and the forecast for the next 48 hours or so.

On 28 October 2003 UTC, an X17.2-class flare from NOAA Region 486 occurred a=
t=20

0951Z, peaking at 1110Z.=A0 This caused severe radio blackouts (R4 is the=20
reported=20
level, see http://www.sec.noaa.gov/NOAAscales/ for details on the scales=20
used)=20
on the sunlit side of the Earth (which would have been morning, on the=20
eastern=20
coast of North America).=A0 It also created an S3 (strong) solar radiation=20
storm.=A0=20
Associated with this flare are a proton event and a full-halo coronal mass=20
ejection (CME).=A0 This flare is the second most intense of the current sola=
r=20
cycle.=A0 It is not historical.=A0 We expect several of these large flares d=
uring=20

any given solar cycle.

The proton event started at about 1330Z, and has exceeded all threshold=20
levels,=20
causing a Polar Cap Absorption event (PCA).=A0 It is expected that this prot=
on=20
event will be prolonged and last for the next 36 hours, to some degree.=A0 T=
his=20

will cause transpolar path degradation (don't expect any DX over the poles=20
nor=20
over any high-latitude paths) for the next few days.

The CME was a full-halo, and is directed squarely at the Earth.=A0 Based on=20=
the=20

speed and recordings, so far, Mike expects it to impact the Magnetosphere at=
=20
about 1500Z 29 October 2003.=A0 When it hits, the shock alone will produce a=
t=20
least G3-level geomagnetic activity.=A0 This would translate to a Kp index o=
f=20
about 8, even if the IMF (Interplanetary Magnetic Field) is not pointed sout=
h=20

when the CME arrives.=A0 After the initial shock wave, if the Bz is negative=
,=20

indicating that the IMF has turned south, the Kp index will remain high, wit=
h=20
a=20
possible Kp of 9 during the passage of the CME.=A0 This will cause between a=
=20
level=20
G4 and a G5 (severe to extreme) geomagnetic storm.=A0 This will severely=20
degrade=20
HF and MW radio communications (while possibly enhancing VHF/UHF=20
propagation).

The timing of the arrival of the CME shock will occur after sunrise for thos=
e=20
in=20
North America.=A0 Therefore, I do not expect to see any Aurora tonight, loca=
l=20
time=20
on 28 October 2003.=A0 However, I do expect radio auroral mode propagation=20
during=20
the day of 29 October 2003, and continuing into the night of the same day.=
=A0=20
If=20
the IMF remains negative, there is a strong chance of a prolonged severe=20
geomagnetic storm, with associated Aurora viewable as far south as southern=20
California and Florida.

Continued radio blackouts are likely from new flare activity.=A0 As I write=20
this,=20
we are in the decline of a new M-class flare.=A0 There are eight main region=
s=20
on=20
the visible solar disk, three of which are actively producing flares.=A0 One=
 of=20

these is about to rotate out of view.=A0 One of the new regions just rotatin=
g=20
into=20
view is active, and has already produced some M-class flares.

Overall conditions:

In the next 12 to 20 hours, expect great conditions on frequencies above 15=20
MHz,=20
while in general, all HF will have periods of radio blackouts during the=20
flare=20
events, if they occur.=A0 (And, they will occur).=A0 Sometime around 1500Z,=20
tomorrow=20
(29 Oct 2003), expect all HF communications to become severely degraded with=
=20
the=20
arrival of the CME shock, and for a severe to extreme geomagnetic storm to=20
commence and last for a prolonged period.=A0 S3-level (severe) solar radiati=
on=20
storm conditions will last for the next 24 to 48 hours.

I expect a lot more activity during this week, but I don't view this as a=20
"third" peak in this current solar cycle, number 23.=A0 Several past cycles=20
have=20
had such bursts during the decline of those cycles.

I'll post more about this soon.

73 de Tomas, NW7US (AAR0JA/AAM0EWA)
--
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