Magnetic Reversals: a technology hazard?

Abstract

The record of magnetic reversals in geological history has fascinating implications and has led to some speculation with regard to life and technology. Although variations in palaeomagnetism are not correlated with mass extinctions, indicating that there is no impact on life from magnetic reversals, this phenomena has raised questions about possible technological impacts. Plimer (2001) suggested that a rapid magnetic reversal could cause the failure of all electronic equipment worldwide and suggested the possible collapse of Western Civilisation. However, comparing the intensity of magnetic flux during the shortest magnetic reversals with that of existing magnetic flux systems such as solar and magnetic storms, offers no evidence that a magnetic reversal will substantially impact electronic or electrical technology.

Introduction

Magnetic reversals are the reversal of the poles as indicated by magnetite orientations in sediments and lavas of the geological record. During a magnetic reversal, particles containing sufficient iron align themselves with the magnetic field as it occurs when they are deposited - at the point when they are immobilised by either the overburden of sedimentation or solidification of cooling lava. The magnetic orientation of these particles gives a strong indication of the location of the magnetic poles at the time of immobilisation and the strength of the magnetic field. Studies of palaeomagnetic reversals yields some striking results.

On the geological time scale, magnetic reversals are very frequent, occurring around seven times per million years. The potential for magnetic reversals to pose a hazard to life or technology is a fairly regular question. Given that mass extinctions do not occur at a frequency any where near that of magnetic reversals it is safe to rule them out as a potential biohazard. This is also confirmed by the physics of magnetic systems, requiring very intense changes in magnetic fields to affect the ionic mechanism of neural networks like the brain and the nervous system. The other consideration delivered by physics is the inverse square rule, which dictates that field strength and changes thereof necessarily become geometrically smaller with distance from the source. The Inverse Square Law speaks also to the weakness of the earth's magnetic field.

Magnetic Reversals and Potential Intensity

Prévôt et. al. (1985) show that geomagnetic field reversals are made up of transitional impulses as the poles do not reverse directly, but wander on a lengthy and convoluted path to eventually wind up in the fully reversed position. During a reversal, there are also variations in absolute magnetic field strength (Coe Et. Al. 1995), but no complete collapse of the earth's magnetic field.

This observation does speak to a number of induced surges of varying strength depending on the orientation of power lines to the direction of magnetic polar wander. Induction surges in electrical equipment depend on the relative change in magnetic field, as well as the length and orientation of conductor wherein the surge is induced within the magnetic field. Coe et. al. (1989) document polar wandering at rates of up to six degrees per day at Steens Mountain. This speaks to much more rapid magnetic reversals than previously expected. However, according to Coe et. al. (1995) a three degree per day rate of magnetic polar wander corresponds to a change in magnetic field strength of 300 nT/day. Thus the maximum intensity of magnetic flux due to a magnetic reversal is observed to be 600 nT/day.

Electrical Induction Surges

Electrical induction occurs when there is a sudden change in magnetic field. Lightning can induce current along a cable without having to strike anything attached to the cable - if it strikes closely enough. This is because a minor electro-magnetic pulse is generated by the discharge and explains how components of a computer can get fried by a very near lightning strike, even when it is switched off and disconnected from all incoming power, RJ45, RJ12, & RF lines. The longer the cable attached to the equipment, the higher the voltage induced in the cable by a given surge. This is why power surges are measured in volts per kilometre.

Magnetic flux can also lead to radio interference. The variation of 29 nT/min measured at the Hermanus Magnetic Observatory, ISO:2001-Nov-24 is certainly troublesome for radio communications, but is insufficient to harm properly isolated electronic equipment. The palaeomagnetic maximum measured at 600 nT/day corresponds to less than 1 nT/min. It took 400 times this flux to bring down the Hydro Quebec Electric System via voltage collapse during the magnetic storm of Mar-1989 and the maximum disturbance during the storm measured by a Danish magnetic observatory totalled 2000nT/min (Pirjola, 2000a, 2000b). The highest natural magnetic flux on record would seem to be from the magnetic storm of July-1982 that produced a flux of 2800 nT/min with induced voltage as high as 29.6 volts per kilometre of cable (Kappenman & Radasky, 1999).

Conclusion

The maximum intensity of magnetic flux measured in magnetic particulates of lavas is no-where near enough to cause problems with electrical and electronic technologies. While, the question of what causes a magnetic reversal remains unanswered, the lack of any correlative factor in terms of extinction rates and rates of geological activity speaks to an external magnetic force or flux. This raises the question of whether magnetic flux thousands of times higher than the maximum flux of the earth's magnetic field, may alter the orientation of the earth's "internal dynamo" if occurring over the correct vector for a sufficient period of time. I think it possible that magnetic or solar storms may occasionally play an active role destabilising the earth's "internal dynamo" with respect to mass rotation; thereby triggering magnetic reversals.

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