A cosmic ray proton with mass \(m\) and charge \(e\) travels vertically downward toward Earth's surface along the equatorial plane at speed \(v\). Near the equator, Earth's magnetic field is horizontal, directed from South to North, with uniform magnitude \(B\). Which of the following correctly identifies the direction of the initial magnetic force acting on the proton and the radius of curvature \(R\) of its trajectory?