Solar storm intensity correlated with suns polarity?

[jnb]

Watching a few documentaries recently on solar storms made me wonder the following ...

The intensity of a solar storm at the earth depends on two factors, how strong the solar storm is and whether the storm's magnetic polarity aligns with or opposes the Earth's magnetic polarity. In which case does the general severity of storms at a solar maximum vary over a 22 year cycle rather than an 11 year cycle. i.e. although the sun is as active in this maximum as it was in 2003 the impact on the Earth is only as severe as it was in 1992.

and a second question is what sort of potential does a big CME generate in a cable. If I have a kilometer long power cable running from a wind turbine to some houses as part of a microgeneration scheme disconnected from the frid what sort of load could that cable pick up in a CME / solar storm?

[rfdesigner]

On the pickup issue, I wouldn't worry TOO much about CMEs,  a 1 km cable is 2~3 orders of magnitude shorter than primary high voltage mains systems.  I'm sure you have high voltage tranzorbs and the like on your link, which are going to be pretty effective.   You have to remember that CMEs are pretty low frequency affairs..  and your "antenna" is going to act like a high pass filter making is insensitive to much of the energy in a CME.

Now If you had no lightening protection, then I'd be worried.. but so long as you have relatively fast acting circuit breakers and devices to discharge current to ground (not just break the circuit.. inducing huge voltages) then I'm sure you'd be OK.

some antenna maths,

Antenna gain equation:     G = 4PI Ae / L^2

Where G is gain (over an isotropic antenna) Ae is the effective aperture of the antenna (on high frequency antennas this equals the dish area), and L is Lamda (or wavelength).  

A "small" antenna will be very insensitive to ultra low frequencies, and the "effective aperture" will be limited to the length of the cable x roughly half the length..  so a 1km cable is ~0.5km2 aperture compared to a 100km mains cable having a 5000km2 aperture.

Where things have gone bang!:   So far as I'm aware only major, national grids have seen transformers etc damaged..  this indicates that the events concerned did not impact smaller systems.

Don't worry unduly, but I might ask my local energy supplier for some numbers, especially if you're doing something involving commerce or safety.

Derek