Talk:Alfvén wave

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Can someone confirm whether μ₀ is supposed to be the permeability (as opposed to permeativity) of free space? Or can someone provide a definition for permeability of a plasma? That is correct.

Answer: There's no such thing as "permeativity". There is permittivity, usually given the symbol ε₀. Permeability is correct in this context. 11/12/2007 —Preceding unsigned comment added by 81.108.237.248 (talk) 17:15, 11 December 2007 (UTC)

Since the constant coefficient in the second expression is approximately seven times the speed of light, many readers will surely wonder how this propagation speed avoids violating Einstein's speed limit. Would someone who knows this field be so kind as to insert a brief mention? Peter (talk) 16:11, 23 January 2008 (UTC)