Abstract
We suggest that pairing of bouncing medium-energy electrons in the auroral upward current region close to the mirror points may play a role in driving the electron cyclotron maser instability to generate an escaping narrow band fine structure in the auroral kilometric radiation. We treat this mechanism in the gyrotron approximation, for simplicity using the extreme case of a weakly relativistic Dirac distribution instead the more realistic anisotropic Juettner distribution. Promising estimates of bandwidth, frequency drift and spatial location are given.
Highlights
The plasma dynamics in the near-Earth high-altitude auroral magnetosphere is comparably easy to monitor, either from ground or space (e.g., [1])
These estimates apply to emission at the fundamental |n| = 1. When this is suppressed say either by the escape condition with frequency mismatch < 0 or by absorption in the background electron population, emission of Auroral Kilometric Radiation (AKR) will occur at the second harmonic |n| = 2 or higher. In this case the location of the AKR source has to be replaced to a magnetic field of the order of B ≈ 8, 000 nT which is at an altitude hn=2 ≈ 2, 540 km above Earth, slightly larger than for emission at the fundamental
Emissions are sought for which are capable of causing intense fast sporadic radiation in the radio regime different from synchrotron emission, the favored mechanism in astrophysics since it is so simple
Summary
The plasma dynamics in the near-Earth high-altitude auroral magnetosphere is comparably easy to monitor, either from ground or space (e.g., [1]). Attempts of the plasma to refill the loss-cone by low frequency resonant wave-particle interaction with VLF [22] are slow quasilinear processes under the dilute topside conditions They effectively limit the high-energy radiation belt fluxes [23] but cannot come up for either depleting the lower energy auroral field-aligned electron loss cone or explaining the variability and fine structure of AKR, though models have been put forward [24] to overcome this deficiency. In the following we propose, at least qualitatively, another promising mechanism possibly capable of causing the spatial and temporal fine structure observed in AKR This mechanism can be based on the resonant interaction of quasi-trapped electrons with propagating plasma waves generating an attraction between electrons spaced by a Debye length along the field
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