Perhaps there's a difference in intensity and duration.
Wikipedia indicates[0] that an EMP could generate 50kV/m electric fields lasting ~1μs, a second component similar to lightning lasting ~1s (electric field intensity not listed), and a third, long-term component that lasts hundreds of seconds.
CMEs, it appears, only generate the third, long-lasting type of electric disturbance. According to NASA[1], these have electric fields up to 26V/km, which is a much lower intensity, but for a significantly longer duration.
[someone please check my numbers; they seem wrong but I'm posting them anyway; my guess is misinterpreting electric field potential as actual induced voltage]
To estimate how much power would be dissipated in transmission lines, let's consider a disconnected 1km wire with a DC resistance of 30 milliohms per kilometer (based on [2]) and ignore all other losses. The so-called E1 pulse at 50kV/m would generate a voltage of 50MV across the wire. Let's assume that lasts 200ns. Power is V^2/R, or (50MV)^2/30mohms=83.33petawatts [3].
That sounds enormous, but it's for a short time. Energy is Pt, or 83.33PW200ns=16.7GJ. To find out how much the wire heats up, let's assume a perfectly straight copper conductor 2cm in diameter. That's a volume of 1kmpi(1cm)^2=1.257m^3 or a mass of 2815kg[4]. Taking energy/(specific heat * mass), we get a temperature rise of 15410K[5]. Copper melts at 1357K, so if the math is right that transmission line would be toast. These numbers seem way too large.
An E3-type pulse from a CME lasting 1000 seconds would generate up to 26kV across the length of wire. That's (26kV)^2/30mohms=22.5GW. Over 1000 seconds that generates 22.5terajoules[6]. I'm not even going to bother calculating a temperature rise for that (okay, it's 20.8 million K[7]). Again, this seems several orders of magnitude off.
I've ignored capacitance, inductance, increased resistance with temperature (up to 170milliohms if I used [8] correctly), and no doubt a lot of other things that would significantly affect the current flow, so keep in mind that these numbers are probably way off. I've also ignored heat dissipation to the air, which would mitigate the energy input a bit but also keep the resistance lower. I welcome any corrections.
Assuming these numbers are completely bogus, it seems to me that an EMP would be more damaging to small electronics, while the CME would be more dangerous for transmission infrastructure.
Claims a 1km copper wire with 10mm has a resistance of ~0.2Ohms. But I don't think it's ok to use normal resistance for pulses that last on the order of microseconds. I imagine capacitance and inductance play a very significant role.
> CMEs, it appears, only generate the third, long-lasting type of electric disturbance. According to NASA[1], these have electric fields up to 26V/km, which is a much lower intensity, but for a significantly longer duration.
And on a much bigger scale distance wise. An EMP would not engulf half the planet in one go.
Wikipedia indicates[0] that an EMP could generate 50kV/m electric fields lasting ~1μs, a second component similar to lightning lasting ~1s (electric field intensity not listed), and a third, long-term component that lasts hundreds of seconds.
CMEs, it appears, only generate the third, long-lasting type of electric disturbance. According to NASA[1], these have electric fields up to 26V/km, which is a much lower intensity, but for a significantly longer duration.
[someone please check my numbers; they seem wrong but I'm posting them anyway; my guess is misinterpreting electric field potential as actual induced voltage]
To estimate how much power would be dissipated in transmission lines, let's consider a disconnected 1km wire with a DC resistance of 30 milliohms per kilometer (based on [2]) and ignore all other losses. The so-called E1 pulse at 50kV/m would generate a voltage of 50MV across the wire. Let's assume that lasts 200ns. Power is V^2/R, or (50MV)^2/30mohms=83.33petawatts [3].
That sounds enormous, but it's for a short time. Energy is Pt, or 83.33PW200ns=16.7GJ. To find out how much the wire heats up, let's assume a perfectly straight copper conductor 2cm in diameter. That's a volume of 1kmpi(1cm)^2=1.257m^3 or a mass of 2815kg[4]. Taking energy/(specific heat * mass), we get a temperature rise of 15410K[5]. Copper melts at 1357K, so if the math is right that transmission line would be toast. These numbers seem way too large.
An E3-type pulse from a CME lasting 1000 seconds would generate up to 26kV across the length of wire. That's (26kV)^2/30mohms=22.5GW. Over 1000 seconds that generates 22.5terajoules[6]. I'm not even going to bother calculating a temperature rise for that (okay, it's 20.8 million K[7]). Again, this seems several orders of magnitude off.
I've ignored capacitance, inductance, increased resistance with temperature (up to 170milliohms if I used [8] correctly), and no doubt a lot of other things that would significantly affect the current flow, so keep in mind that these numbers are probably way off. I've also ignored heat dissipation to the air, which would mitigate the energy input a bit but also keep the resistance lower. I welcome any corrections.
Assuming these numbers are completely bogus, it seems to me that an EMP would be more damaging to small electronics, while the CME would be more dangerous for transmission infrastructure.
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[0] https://en.wikipedia.org/wiki/Nuclear_electromagnetic_pulse#...
[1] http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=4189
[2] http://large.stanford.edu/courses/2010/ph240/harting1/
[3] http://www.wolframalpha.com/input/?i=%2850MV%29^2%2F30mohms
[4] http://www.wolframalpha.com/input/?i=1km*pi*%281cm%29^2+*+de...
[5] http://www.wolframalpha.com/input/?i=16.67GJ+%2F+%28specific...
[6] http://www.wolframalpha.com/input/?i=%2826kV%29^2%2F30mohms
[7] http://www.wolframalpha.com/input/?i=%2826kV%29^2%2F30mohms+...
[8] http://hyperphysics.phy-astr.gsu.edu/hbase/electric/restmp.h...