Speaker
Description
Pulsars are neutron stars that emit coherent radio beams out of their magnetic poles. However, the origin and exact mechanism of their coherent radio emission are still under investigation. We exploited plasma bunches, clouds of electron-positron pairs, created during spark events in gap regions by utilizing particle-in-cell simulations streaming instabilities and hot bunches to study the emissions. We found that the main parameter influencing the bunch evolution is the initial drift velocity between electrons and positrons. For zero drift, the bunches can freely expand, and adjacent bunches may overlap in the phase space, forming relativistic streaming instability that produces soliton-like waves. Otherwise, the bunches are constrained from expansion and form strong oscillating local electrostatic fields where plasma particles can oscillate and emit coherent radio waves. We also developed a new post-processing technique for calculation of the emitted radio power and found that the bunches constrained from expansion have similar observational characteristics as those observed for pulsars. The estimated radio spectrum contains a flat part for low frequencies and power-law profiles for higher frequencies. Also, the emitted radiation is relativistically beamed along the pulsar dipole axis and oscillates at microsecond scales.
