Communication Systems

Ground Based | Mobile Phone | Space Based

The telegraph was the first man-made system to involve the use of long electrical conductors. By using an electrical current to move magnetic needles, the operator was able to send messages in code along long stretches of cable. As a result, this was the first such system to be affected by geomagnetically induced currents. The first recorded incident of space weather effecting a telegraph system took place as far back as 1847 when engineer W. H. Barlow published his paper "on the spontaneous electrical currents observed in wires of the electric telegraph", Phil. Trans. Roy. Soc., London, 139, 61-72, 1849:

"When the telegraph instruments are not working, the batteries are put out of circuit, and the wires remain with a simple earth connection at both extremities.
It was in this condition of the wires that spontaneous currents were observed to arise in them, producing occasionally large deflections in the needles. These deflections were sometimes to the right and sometimes to the left; at times they changed rapidly from right to left, at others they continued in one direction from periods varying from a few minutes to one or more hours.
My attention was strongly drawn to the subject by the constancy of these effects, when a circumstance occurred which imparted a new interest to the inquiry. On the evening of the 19th of March, 1847, a brilliant aurora was seen, and during the whole time of its remaining visible, strong alternating deflections occurred on all the instruments. Similar effects were observed also on the telegraphs on several other lines of railway."

Following this observation, numerous incidents of spontaneous currents seen in telegraphs were recorded and the presence of aurora noted. Unusually large magnetic storms took place on February 4, 1872, and August 5, 1972. These were accompanied by exceptional auroral displays at middle and low latitudes. During the 1872 storm it was possible to send telegraph communications using the induced currents in the system alone, without additional power sources. At other times however, the signal was totally disrupted preventing any communication.

More recent communication methods are also subject to space weather influences. These however, are mainly caused by space weather induced changes to the composition and structure of the ionosphere.

Ground Based 

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