What speed would a proton need to achieve in order to circle Earth 1000.0 km above the magnetic equator? Assume that Earth’s magnetic field is everywhere perpendicular to the path of the proton and that Earth’s magnetic field has an intensity of 4.00 × 10-8 T. (Hint: The magnetic force exerted on the proton is equal to the centripetal force, and the speed needed by the proton is its tangential speed. Remember that the radius of the circular orbit should also include the radius of Earth. Ignore relativistic effects.)