spaceweb@oulu.fi - last update: 1 July 1998, 1200 UT (RR) . ... Relates the wave number k to the wave frequency. ... From the equation of motion , m d v /dt = q( v x B ) one can calculate that, in a presence of magnetic field B , a charged particle is accelerated in direction perpendicular to both v (perp) and B . ... The angle a between magnetic field B and velocity vector of a charged particle, v ., i.e., sin a = v(perp) / v(total), where v(perp) refers to the velocity component perpendicular to B . ...