[PPRAANet] CME protection

[John Bloodgood]

The recent X9.3 solar flare and subsequent coronal mass ejection (CME) has resulted in some radio blackouts and G4  (G5 being the highest) geomagnetic storms.  It has also resulted in a flurry of conversations by folks about building Electro-Magnetic Pulse (EMP) protections against a Carrington Event level flare and CME.

 It appears that a lot of folks not understand the difference between a simple Faraday Cage and EMP hardening (I have worked in, designed, and built HEMP shelters – comparing HEMP hardening to a simple Faraday Cage is like comparing a battle tank and a VW van) , but more importantly many don’t understand the differences between an EMP and a CME.

The fact is that a Faraday Cage or EMP hardened container does very little to protect your electronics from a CME.  About the only good it does is that you have to unplug the device to put it in such a container.  Unplugging your equipment from commercial power, phone lines, and cable TV coax does far, far more to protect against CMEs than a magic metal container does.  In fact, unplugging is really the about only thing you need to do to protect against a CME.

CMEs and EMP act very differently.  A solar flare produces a rapid burst of X-Ray and light energy which hits the Earth in a matter of minutes, causing some immediate radio blackouts, but not really harming electronics.  The blackouts from this usually don’t last a real long time, but a subsequent CME may wreak more havoc.  If the flare is accompanied by a CME, the CME will take many hours to arrive – anywhere from about 17 to about 40 hours.  When the CME arrives it can result in geomagnetic storms which in turn induce currents in very long conductors (think on the order of kilometers – even a half wave 160 meter dipole wouldn’t really be long enough) such as the afore mentioned power lines, phone lines, and possibly cable TV coax.  These currents can be very high, even lethal.  However, the length of conductors in most electronic devices or even HF antennas are just way too short for these currents to be developed. Unlike a CME, an EMP is a very rapid and short lived event which can cause problems within electronic devices.

If there is solar flare with a dangerous CME, NOAA 's Space Weather Prediction Center will send out alerts.  At that time, simply unplug all your electronic devices from power lines, phone lines, and cable TV/internet coax.

So again, aside from the fact that you have to unplug your electronic devices to put them in a Faraday Cage or EMP hardened box, the cage or box is pretty useless for CME protection.





John Bloodgood, KD0SFY