TopBand: propagation versus sun

[Robert Brown]

Greg,

The A-index is a measure of magnetic activity at a particular magnetic 
bservatory.  There is a global A-index too, averaged over a dozen 
observatories around the world.  The K-index is given eight times a day 
and represents current conditions, not averaged over more than 3 hours.

In any event, magnetic activity starts to get interesting when the 
A-index gets above 25, with magnetic storming for A above 40-50.  Those 
conditions involve energy input to the atmosphere, from collision ionization 
by energetic auroral electrons and the ohmic-heating of ionospheric current 
systems.  That input has been observed to propagate to lower latitudes 
from the auroral zones and can perturb the lower atmosphere by generating 
travelling ionospheric disturbances (TID) and acoustic/gravity waves.

Those conditions can also affect propagation on Top Band but are not 
well-documented as observations by the scientific community have become 
sporadic now that the main features of the events have been established.  
But it is of interest to log Top Band conditions with various levels of 
magnetic activity, for your information as well as possible recurrences.

Have fun, another season is about to start with the equinox.

73,

Bob, NM7M

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