The solar wind is a thin, hot gas given off by the sun. Charged particles in this gas enter the magnetic field of the earth and can experience a magnetic force. Suppose a charged particle traveling with a speed of 9.0 X 10 6 m/s encounters the eath's magnetic field at an altitude where the field has a magnitude of 1.2 X 10-7T. Assuming that the particle's velocity is perpendicular to the magnetic field, find the radius of the circular path on which the particle would flow if it were a proton.