Evaluating the diffusive equilibrium models: Comparison with the IMAGE RPI field‐aligned electron density measurements

Abstract

The diffusive equilibrium models that are widely used by the space physics community to describe the plasma densities in the plasmasphere are evaluated with field-aligned electron density measurements from the radio plasma imager (RPI) instrument onboard the IMAGE satellite. The original mathematical form of the diffusive equilibrium model was based on the hydrostatic equilibrium along the magnetic field line with the centrifugal force and the field-aligned electrostatic force as well as a large number of simplifying approximations. Six free parameters in the mathematical form have been conventionally determined from observations. We evaluate four sets of the parameters that have been reported in the literature. The evaluation is made according to the equatorial radial distance dependence, latitudinal dependence at a given radial distance, and the combined radial and latitudinal dependences. We find that the mathematical form given in the diffusive equilibrium model is intrinsically incompatible with the measurements unless another large number of free parameters are artificially introduced, which essentially changes the nature of a theoretical model to an empirical model.

A new dynamic fluid‐kinetic model for plasma transport within the plasmasphere

“…The fluctuations of the O + , H + , and He + equatorial densities are due to the day‐night variations of the upward ionospheric fluxes. The time variations of the field‐aligned density distributions of O + , H + , and He + (data not shown) indicate that for each ion species, no shock is produced at any time of refilling and refilling is from the base ionospheres to the equator, consistent with the conclusions of Wilson et al [] and observations of Reinisch et al [, ], Huang et al [], Song et al [], and Ozhogin et al [, ].…”

Modeling the plasmasphere to topside ionosphere scale height ratio

“…The TaD model belongs to this group of models. Its core component, the Topside Sounder Model (TSM) originally proposed by Marinov et al (2004) and Kutiev et al (2006), reproduced the topside electron density scale height (H T ) and the O + -H + (upper) transition height (h T ), based on 172,622 measured N e profiles by topside sounders onboard Alouette-1a, -1b, -1c, and -2 and ISIS-1 and -2 satellites (Bilitza et al 2003). The H T and h T models were represented by five-dimensional polynomials expressing both quantities as functions of month of the year, geomagnetic latitude, local time, solar flux (F10.7), and geomagnetic index (K p ).…”

“…The method of extracting the topside parameters H T , h T , and R T was described by Marinov et al (2004), Kutiev et al (2006), and Kutiev & Marinov (2007). The topside (O + density) scale height H T was defined at the minimum gradient dh/d(ln O + ) of the topside part of the profile plotted in height/lnNe scale.…”

“…A new empirical model of plasmasphere density distribution has been developed recently, based on the Radio Plasma Instrument (RPI) onboard the Imager for Magnetopauseto-Aurora Global Exploration (IMAGE) satellite (Reinisch et al 2001;Huang et al 2004) which provides N e profiles along magnetic field lines (Ozhogin et al 2014). To connect the plasmasphere model to the topside ionosphere, Reinisch et al (2007) introduced a modified Chapman function, named Vary-Chap, with a continuously varying scale height H(h).…”

Propagation of EMIC Waves Inside the Plasmasphere: A Two‐Event Study

“…Second, when the guided waves approached the local f biHe+ at higher |MLAT|, some of the waves may pass through f biHe+ without reflection. Then, the waves will find their way inward and equatorward, depending on the plasmaspheric density distribution (Angerami & Thomas, ; Ozhogin et al, ). Any of these two ways can explain why the inward waves are observed at higher |MLAT| and are more intense than the outward waves.…”