Generalised Model for Earths Foreshock Radiation: First Source Images and Inclusion of Linear Mode Conversion

It is well understood that Earth's foreshock radiation is due to the bow shock deflecting the solar wind and accelerating electrons upstream into the foreshock where they produce Langmuir waves and radio emissions. Here we make new predictions about the radio emissions produced in Earths foreshock, with associated implications for other sources of radio emissions at multiples of the plasma frequency. Specifically based on an existing theory for Type II solar radio bursts and Earths foreshock radiation, we calculate the electron distributions, the Langmuir waves they drive, and the radio emissions produced by specific nonlinear wave-wave processes. We generalise the theory for the 3D case and to include linear mode conversion of Langmuir waves into fundamental radio emission at density gradients. This process is found to produce 10 30% of the total flux near the plasma frequency. We also produce the first 2D source pictures of Earths foreshock radiation, confirming the prediction from Gurnett et al. (1993) that the radio source should be elongated perpendicular to the plane containing the upstream magnetic field and solar wind velocity vectors.