Incoherent radar spectra in the auroral ionosphere in the presence of a large electric field: The effect of O+-O+ Coulomb collisions
نویسنده
چکیده
We have used Monte Carlo simulations of O+ velocity distributions in the high latitude Fregion to improve the calculation of incoherent radar spectra in auroral ionosphere. The Monte Carlo simulation includes ionneutral, O+-O collisions (resonant charge exchange and polarization interaction) as well as O+-O+ Coulomb self-collisions. At high altitudes, atomic oxygen O and atomic oxygen ion O+ dominate the composition of the auroral ionosphere and consequently, the influence of O+-O+ Coulomb collisions becomes significant. In this study we consider the effect of O+-O+ Coulomb collisions on the incoherent radar spectra in the presence of large electric field (100 mVm−1). As altitude increases (i.e. the ion-to-neutral density ratio increases) the role of O+-O+ Coulomb self-collisions becomes significant, therefore, the one-dimensional, 1-D, O+ ion velocity distribution function becomes more Maxwellian and the features of the radar spectrum corresponding to nonMaxwellian ion velocity distribution (e.g. baby bottle and triple hump shapes) evolve to Maxwellian ion velocity distribution (single and double hump shapes). Therefore, O+-O+ Coulomb self-collisions act to isotropize the 1-D O+ velocity distribution by transferring thermal energy from the perpendicular direction to the parallel direction, however the convection electric field acts to drive the O+ ions away from equilibrium and consequently, non-Maxwellian O+ ion velocity distributions appeared. Therefore, neglecting O+-O+ Coulomb self-collisions overestimates the effect of convection electric field.
منابع مشابه
Incoherent Scatter Radar Observations of Westward Electric Fields and Plasma Densities in the Auroral Ionosphere, 1
متن کامل
A kinetic model for runaway electrons in the ionosphere
Electrodynamic models and measurements with satellites and incoherent scatter radars predict large field aligned current densities on one side of the auroral arcs. Different authors and different kinds of studies (experimental or modeling) agree that the current density can reach up to hundreds of μA/m2. This large current density could be the cause of many phenomena such as tall red rays or tr...
متن کاملPonderomotive Acceleration in the Auroral Region A Kinetic Simulation
Alfvtn waves with frequencies of the order of several Hertz have been observed in the auroral region. These waves are thought to be responsible for the acceleration f !0nosphen'c particles out of the ionosphere and into the magnetosphere. As an Alfvtn wave propagates into an inhomogeneous ionosphere, the amplitude of the wave decreases resulting in a gradient in the electric field and a pondero...
متن کاملDetecting Narrow, Field-aligned Spatial Structures in the Auroral Ionosphere Using the Eiscat Svalbard Radar Dual Antennas as an Interferometer
In order to provide observations to help decide between competing theories of Anomalous Ion Spectra (AIS) observed at several Incoherent Scattering Radar (ISR) observatories, to explore the possibility of any connection between this phenomenon and visible auroral forms, and to see if enhanced scattering is due to localised scattering structures, we have used the two antennas of the EISCAT Svalb...
متن کاملAddition To Ph . D . Thesis Proposal
This document discusses the background and previous literature regarding radar and optical observations of the aurora. The first section covers coherent and incoherent scatter radars and open science questions involving the use of radars. The next section covers optical auroral imaging of both luminous and black auroral features, and the open science questions related to auroral imaging. The th...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2005