[HCRA] Fw: [YCCC] A-Index

Thu, 5 Dec 2002 09:37:19 -0500

This is an interesting thread on the Yankee Clipper Contest Club reflector.
I think a good many of us on this list could learn from this.

Dan S.
----- Original Message -----
Wrom: NNYCGPKYLEJGDGVCJVTLBXFGGMEPYOQK
To: "Ted Edwards W3TB" <[email protected]>; "YCCC Reflector" <[email protected]>
Sent: Thursday, December 05, 2002 7:19 AM
Subject: RE: [YCCC] A-Index

> Hi Ted - good question.
>
> Mike, K1MK gave a very good answer, but I thought I would try to add to
it.  I will give this a shot.
>
> The A index is an average of geo-magnetic activity over the previous 24
hours.
> (The K or Kp index is a shorter time measurement, recorded every 3 hours.)
>
> I think it correlates in some way with the K index, which is recorded
every 3 hours.
> Note: A mid latitude K index will be lower than a northern latitude K
index, like from Scandinavia or Alaska or Zone 2.
>
> What makes them high?  Because of solar events that eject "mass"
> (coronal mass ejections, CMEs) (as opposed to energy, i.e.; x-rays and
light).
> The 'mass" is charged particles (ions).
>
> If a stream of particles form the Sun hits the earth's magnetosphere, it
causes "magnetic disturbance" or
> geomagnetic disturbance, which causes higher levels of absorption in the D
(and E and F)
> layers of the Ionosphere.  When a very intense disturbance occurs, the HF
bands may go
> completely dead, and Aurora Borealis occurs.  Aurora starts at a K or
about 4 but becomes
> significant for upper HF and VHF propagation at 5 and really good at K=6.
>
> It is important to note that the A and K and their propagation effects
vary with where you are in the world and where you want your
> radio signals to go to.  We here in the Northeast are more vulnerable that
most as the magnetic North pole is at a true bearing of
> about 16 degrees from us and well S of the true N pole, so
> we can get hit with absorbtion on the path to Europe, while folks in
Florida and South see enhanced propagation to Europe,
> particularly on 10 and 6 meters.
>
> My cable modem  internet access is down right now, so I can not validate
the links below as still valid.
> There are many more which I can post if anyone is interested.
>
> http://dx.qsl.net/propagation/propagation.html
>
> http://www.spacew.com/main.html
>
> www.dxatlas.com/ionoprobe
>
> Studying HF/VHF propagation for 35 years,
>
> John Allen K1AE
> [email protected]
> 978 779-6189
>
>
> > -----Original Message-----
> > Wrom: EDOTWFAOBUZXUWLSZLKBRNVWWCUFPEGAUTFJMVRESKPNKMBIPBARHDMNNSKVFVWR
> > Edwards W3TB
> > Sent: Wednesday, December 04, 2002 6:57 PM
> > To: YCCC Reflector
> > Subject: [YCCC] A-Index
> >
> >
> > I have noticed that the WWV "A" Index rose to 30 at the start of CQWW CW
> > and then settled at about 15 ever since --- although it often sits below
5.
> > Can anybody tell me the significance of the steadier-but-higher level?
> >
> > KB!         73 de Ted W3TB
> >
> > _______________________________________________
> > YCCC Reflector
> > [email protected]
> > http://lists.contesting.com/mailman/listinfo/yccc
> >
>
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>