Propagation and escape of astrophysical cyclotron-maser radiation

A multitude of astrophysical plasma environments exist where a combination of particle acceleration, convergent magnetic fields and a sufficiently large ratio of electron cyclotron frequency to plasma frequency are present to support electron cyclotron-maser emission [1-6]. The resultant radiation signatures typically comprise of well-defined spectral components (around the relativistic electron cyclotron frequency) with near 100% left or right handed circular polarization when viewed out-with the source region. Although the generation mechanism has been well documented [7-25], there are numerous potential hindrances to the propagation and escape of the radiation from the source region, including issues of geometry/mode conversion [26] and coupling onto the dispersion branch connecting with vacuum propagation [12]. In the current context we consider the results of numerical Particle-in-cell (PiC) simulations conducted at the University of Strathclyde to study the spatial growth rate and emission topology of the cyclotron-maser emission process. The results have significant bearing on the radiation propagation characteristics and highly debated question of propagation/escape, with particular relevance to the planetary/stellar auroral magnetospheric case.