Asymmetric multiple auroral arcs and inertial Alfvén waves
نویسندگان
چکیده
High-resolution optical observations by the University of Calgary Portable Auroral Imager show a frequent occurrence of asymmetric multiple small-scale auroral arc structures during auroral substorms. Whereas the classical multiple arc array tends to exhibit a fairly symmetrical configuration, with parallel motions within individual discrete arcs being opposite in direction across the center of the arc array, the multiple arcs to be discussed herein are distinguished by the presence of discrete arcs strictly equatorward of the two bright counter-streaming arcs that would ordinarily define the center of the arc array. The intensity of these parallel equatorward-lying arcs were in most cases found to decrease rapidly in the equatorward direction. By considering the topology of the structures and the spacing between arcs, observations are found to be consistent with recent theories suggesting inertial Alfvén waves as a possible cause of fine-scale auroral arcs.
منابع مشابه
Fine-Scale Cavitation of Ionospheric Plasma Caused by Inertial Alfvén Wave Ponderomotive Force
Deep, very narrow magnetic-field-aligned density depletions were observed by the Freja spacecraft during auroral oval crossings. These cavities have perpendicular width of the order of the electron skin depth cyvpe and are associated with low-frequency electromagnetic perturbations and with discrete auroral structures. We demonstrate here that these cavities are likely produced by the ponderomo...
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 کاملReduced magnetohydrodynamic equations with coupled Alfvén and sound wave dynamics
A set of reduced magnetohydrodynamic equations is described that is appropriate for the simulation of auroral Alfvén waves using curvilinear coordinates. These equations include the parallel electric field, ponderomotive force, diamagnetic drift effects, and gravity and rotation, but do not include the fast mode dynamics. The equations are formulated for multiple species, but quasineutrality is...
متن کاملGeneration of short-burst radiation through Alfvénic acceleration of auroral electrons
[1] A comparison of modeled simulation results with in situ observations is presented in an effort to better understand the generation mechanism of short-burst radiation (AKR) observed in the Alfvénic acceleration region. The simulation is performed using a linear gyrofluid Alfvén model to generate propagating inertial Alfvén waves with a test particle scheme to study the behavior of electrons ...
متن کامل