The radio frequency of bremsstrahlung emission is related to a plasma's electron density through the electron plasma frequency ( f p ) from Equation 1. A plasma with a density n e can produce emission only at or below the corresponding f p . Density in the corona generally decreases with height above the visible "surface", or photosphere, meaning that lower-frequency emission is produced higher in the atmosphere, and the Sun appears larger at lower frequencies. This type of emission is most prominent below 300 MHz due to typical coronal densities, but particularly dense structures in the corona and chromosphere can generate bremsstrahlung emission with frequencies into the GHz range.