Do magnetospheric shear Alfvén waves generate sufficient electron energy flux to power the aurora?
نویسندگان
چکیده
[1] Using a self‐consistent drift‐kinetic simulation code, we investigate whether electron acceleration owing to shear Alfvén waves in the plasma sheet boundary layer is sufficient to cause auroral brightening in the ionosphere. The free parameters used in the simulation code are guided by in situ observations of wave and plasma parameters in the magnetosphere at distances >4 RE from the Earth. For the perpendicular wavelength used in the study, which maps to ∼4 km at 110 km altitude, there is a clear amplitude threshold which determines whether magnetospheric shear Alfvén waves above the classical auroral acceleration region can excite sufficient electrons to create the aurora. Previous studies reported wave amplitudes that easily exceed this threshold; hence, the results reported in this paper demonstrate that auroral acceleration owing to shear Alfvén waves can occur in the magnetosphere at distances >4 RE from the Earth.
منابع مشابه
Reply to comment by F. Mottez on “Do magnetospheric shear Alfvén waves generate sufficient electron energy flux to power the aurora?”
[1] The gauge condition relating the electromagnetic potentials of shear Alfvén waves is one of the key governing equations in simulations of low-frequency waves in the Earth’s magnetosphere. Mottez [2013] suggests that the gauge condition used in Watt and Rankin [2010] is inappropriate for the case where the perpendicular wave number of the shear Alfvén wave varies as a function of distance al...
متن کاملPropagation of kinetic Alfvén waves in the ionospheric Alfvén resonator in the presence of density cavities
[1] Recent observations of particle distributions that are narrow in pitch angle and broad in energy have suggested that kinetic Alfvén waves are a significant contributor to auroral particle acceleration. Oscillations at frequencies near 1 Hz are a natural consequence of the propagation of Alfvén waves in the strongly varying Alfvén speed profile above the auroral ionosphere, the so-called ion...
متن کاملKinetic Theory of the Alfvén Wave Acceleration of Auroral Electrons
Recent observations have indicated that in addition to the classical “inverted-V” type electron acceleration, auroral electrons often have a field-aligned distribution that is broad in energy and sometimes shows time dispersion indicating acceleration at various altitudes up the field line. Such acceleration is not consistent with a purely electrostatic potential drop, and suggests a wave heati...
متن کاملLocalized parallel electric fields associated with inertial Alfvén waves
Measurements of intense, localized parallel electric fields are reported in association with inertial Alfvén waves and accelerated electron fluxes in a space plasma. The parallel electric fields are localized to several hundreds of Debye lengths and carry potentials on the order of the energy of the accelerated electron fluxes. The structures are observed at sharp maxima or minima of the pertur...
متن کاملNon-local interactions between electrons and Alfvén waves on auroral field lines
The interaction of auroral electrons with kinetic Alfvén waves is complicated by the fact that the Alfvén speed above the ionosphere is strongly inhomogeneous, leading to a region often referred to as the ionospheric Alfvén resonator (IAR). For these waves, the wave-particle interaction must be treated with a non-local kinetic approach. Linear damping of these waves due to the wave-particle int...
متن کامل