http://elecraft.85.s1.nabble.com/OT-K-index-2-But-Bands-Deader-Than-Doornail-tp442135p442137.html
Always take a listen to the HF beacons. This is a great way to see if
the bands are "open". Right now from Colorado, I can hear W6 and KH6
Stephen W. Kercel wrote:
> Jeff:
>
> It is a perfectly reasonable topic, and one I've been wondering about
> myself.
>
> Since Thanksgiving, we've had astoundingly bad conditions with lots of
> flares and storms.
>
> There are three mechanisms of disruption indicated on the NOAA Web
> site, radio blackouts due to X-rays which are mostly felt on the
> sunlit side of the Earth and dissipate in a matter of hours, "solar
> storms" which are bursts of heavy particles (protons, as I recall),
> and the solar wind (a stream of electrons).
>
> As I understand the numbers, K is a "near real time" (reported every 3
> hours) indication of disruption of propagation due to the geomagnetic
> fluctuations caused by fluctuations in the solar wind. With each value
> of K there is an associated value of a, with a pseudo logarithmic
> relationship between K and a, such that k=1 => a=3, and k=9 => a=400.
> A is the average of the last 8 a values, and thus is an indication of
> the cumulative effect of the solar wind on the geomagnetic field over
> the past 24 hours.
>
> It is important to realize that A and K are statistical measures that
> correctly describe propagation most of the time, but not always.
>
> A=9 is not low. It is usually an indication of "marginal but somewhat
> useful" conditions.
>
> My guess is that when the atmosphere takes a series of severe hits, as
> has happened over the past week, it takes much more than 24 hours
> (suggested by formula for the A index) for the atmosphere to "heal"
> itself, irrespective of the low A and K values currently being reported.
>
> It is my observation over recent months that once we've had a
> geomagnetic storm it requires two continuous days of both K and A <= 2
> before one sees the return of good conditions.
>
> The problem is aggravated by the low sunspot numbers, and consequent
> low MUFs. I've noticed that most nights lately from New England, one
> hears practically nothing from Europe on 40 m (although one can hear
> Caribbean stations running European pileups). The reason is that the
> MUF between NE and EU most nights is about 6 MHz. 40 is dead but 80
> (in between storms) can be very lively.
>
> Anyway, given the low MUFs, most HF bands are dead much of the time,
> and 80 is only usable when the noise (partly induced by geomagnetic
> activity) dies down.
>
> I'd be curious what other list members know about this.
>
> 73,
>
> Steve Kercel
> AA4AK
>
>
>
> At 03:53 PM 12/19/2006, Jeff wrote:
>> My apologies for going off-topic, but I'm learning to interpret the
>> various
>> solar parameters, such as the A- and K-indexes, and I'm a bit
>> confused. The
>> K-index is only 2 at 2045 UTC on Dec. 19, but I can't hear ANY CW
>> signals on
>> any band, which, until recent weeks, was a very unusual state of
>> affairs.
>> The A-index is 9, which I believe is also relatively low. Shouldn't
>> I be
>> hearing at least a couple of signals, or is it just that everyone is
>> still
>> at work?
>>
>> Thanks & Happy Holidays,
>> Jeff
>> WB5GWB
>> Long Island, NY
>>
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