Magnetospheric structures under four conditions: sub-Alfvénic (a), transition (b), super-Alfvénic (c), and CME conditions (d). The colour scale represents the density distribution of the solar wind. In the sub-Alfvénic regime (M_A < 1), the stellar wind does not form a bow shock and the radio emission originates solely from magnetospheric reconnection. In the transition case, a weak and asymmetric shock begins to form. In the super-Alfvénic case (M_A > 1), a clear bow shock develops, and the radio emission is strengthened by the shock and the reconnection region, the CME-like event, and a highly compressed and asymmetric magnetosphere.