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    Re: New inovation in astro navigation?
    From: George Huxtable
    Date: 2010 Aug 3, 21:40 +0100

    Lu Abel wrote, about effects of a serious solar flare on the early electic
    telegraph
    
    "The Northern Lights are caused by atmospheric ionization, and solar flares
    significantly increase it, so there are many examples of the Northern
    Lights being seen below their usual latitudes due to solar flares.
    
    But as a graduate electrical engineer, I have a hard time with "shorting
    out telegraph wires."
    
    "Shorting out" requires either wires to stretch enough that they touch, or
    that the air or insulation separating them suddenly becomes conductive.   I
    can not imagine how a solar flare could cause this to happen.
    
    Do you have any reference material on how this solar flare "shorted out
    telegraph wires?"
    
    ===================================
    
    I know little about early telegraphy, and have read no authoritative detail
    about what happened in 1859 or in 1989. But that won't deter me from
    speculating.
    
    I~n early telegraphy, repeaters were required at intervals, which were
    first human operators, later based on the use of electrical relays. The aim
    was to maximise the distance between repeating stations. This was done by
    keying signals using a large voltage at one end, taken from a big stack of
    batteries, which could amount to some kilovolts, and detecting the
    resulting current pulses at the other using a sensitive galvanometer. There
    would be spark gaps placed to protect the galvanometer in the event of a
    lighning strike. I can envisage a flare producing enhanced ionisation in
    the air, resulting in sparking at those spark gaps and perhaps elsewhere.
    
    I've considered the effect of voltages induced in the current loop created
    by the wire and its ground return, by changes in the magnetic field passing
    through that loop, but at first sight the order-of-magnitiude seems quite
    insufficient to give rise to sparking..
    
    As for the 1989 event that knocked out the Quebec electrical grid, I've
    seen it ascribed to a runaway event triggered by a burned-out power
    transformer. But what caused the transformer failure? Such systems are
    protected against lighning surges, which I would expect to be rather more
    testing.
    
    Or was it a failure of cotrol circuitry? It's possible to imagine sudden
    changes in Earth's magnetic field giving rise to unexpected current surges
    in ground-loop circuits, giving rise to a cumulative domino-effect in the
    protection system.
    
    But to be honest, I'm only guessing. Can anyone offer an authoritative
    study of either event?
    
    George.
    
    contact George Huxtable, at  george@hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
    
    
    

       
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