This study examines the mode conversion from electrostatic to electromagnetic waves near the plasma frequency in the Earth's electron foreshock. The conversion and reflection coefficients are obtained by solving coupled differential equations in a weakly magnetized warm plasma with a longitudinal linear density gradient. Results indicate that the foreshock first harmonic electromagnetic emissions and the backward-propagating Langmuir waves required for the generation of the second harmonic electromagnetic waves may be efficiently produced by the linear conversion process in an inhomogeneous plasma. ¿ 1998 American Geophysical Union