The arcs are from a single 'ping' from a single satellite. The satellite knows where it is, and with the 'ping' it was able to determine the distance from the satellite to the aircraft. The satellite is the distance of this arc, the radius is the known distance between the satellite and aircraft. By having the last known radar location near Malaysia, approximate flight speed, and time between radar contact and satellite contact, an approximate distance is predicted along the circle defined by the centre (satellite) and radius/arc.