Originally, in superconducting transmission lines, the Swihart velocity is the propagation velocity of electromagnetic waves along transmission line.

Swihart velocity plays an important role in the physics of long Josephson junction

Long Josephson junction

In superconductivity, a long Josephson junction is a Josephson junction which has one or more dimensions longer than the Josephson penetration depth \lambda_J. This definition is not strict....

s (LJJ) that, in essence, are superconducting transmission lines with dispersion and nonlinearity due to Josephson effect

Josephson effect

The Josephson effect is the phenomenon of supercurrent across two superconductors coupled by a weak link...

. In LJJ

LJJ

LJJ might be an acronym or abbreviation for:*Long Josephson junction*Lords Justice of Appeal...

, Swihart velocity is a characteristic velocity of propagation of electromagnetic waves (aka Josephson plasma waves), see long Josephson junction

Long Josephson junction

In superconductivity, a long Josephson junction is a Josephson junction which has one or more dimensions longer than the Josephson penetration depth \lambda_J. This definition is not strict....

for details. For example, the group velocity may have any value from zero up to Swihart velocity.