Conductor in a plasma sheath The model presented is a synthesis of the theory put forth by previous authors. An RF pulse is applied across either the X or Y 500 m sounding antenna on IMAGE, disturbing the ambient plasma. During the positive half cycle of the pulse, a group of electrons are attracted to the antenna. During the negative half cycle, though, the group of protons that migrate to the antenna cannot be as large as the preceding group of electrons because protons have much lower mobility. This asymmetrical movement of charge enables the antenna to attain a negative potential. By equilibrium, the antenna has potential (given by Oya) where is the amplitude of the RF signal, me and mp are the electron and proton masses, Tp is the proton temperature, k is Boltzmann’s constant, and e is the electric charge. The negative potential causes a proton concentration to develop around the antenna, forming a plasma sheath with a tapered profile. Subsequent RF pulses traverse the sheath and energize the protons, sending them into cyclotron motion. A sufficient number of protons have to be excited for echoes to be observed later. Remarkably, the protons exhibit a plasma memory phenomenon, in which they can replicate the original wave at nTp . If the resultant electron Bernstein waves travel in a direction that is conducive to signal reception on the antennae, then the proton cyclotron echoes are detected by IMAGE. For higher n (longer time delays), the effect may be less noticeable due to time-dependent loss of energy.