An extended TRANSCAR model including ionospheric convection: simulation of EISCAT observations using inputs from AMIE

Abstract

Abstract. The TRANSCAR ionospheric model was extended to account for the convection of the magnetic field lines in the auroral and polar ionosphere. A mixed EulerianLagrangian 13-moment approach was used to describe the dynamics of an ionospheric plasma tube. In the present study, one focuses on large scale transports in the polar ionosphere. The model was used to simulate a 35-h period of EISCAT-UHF observations on 16-17 February 1993. The first day was magnetically quiet, and characterized by elevated electron concentrations: the diurnal F 2 layer reached as much as 10 12 m −3 , which is unusual for a winter and moderate solar activity (F 10.7 =130) period. An intense geomagnetic event occurred on the second day, seen in the data as a strong intensification of the ionosphere convection velocities in the early afternoon (with the northward electric field reaching 150 mV m −1 ) and corresponding frictional heating of the ions up to 2500 K. The simulation used time-dependent AMIE outputs to infer flux-tube transports in the polar region, and to provide magnetospheric particle and energy inputs to the ionosphere. The overall very good agreement, obtained between the model and the observations, demonstrates the high ability of the extended TRANSCAR model for quantitative modelling of the high-latitude ionosphere; however, some differences are found which are attributed to the precipitation of electrons with very low energy. All these results are finally discussed in the frame of modelling the auroral ionosphere with space weather applications in mind.

Observing the north polar ionosphere on 30 October 2003 by GPS imaging and IS radars

“…The Svalbard radar monitors increased electron density between 20:50 UT and 21:30 UT, with an electron temperature of ∼2000 K after 21:10 UT. The Tromsø radar measured increased electron density several minutes later from 21:35-22:00 UT accompanied by an electron temperature decrease to 2000 K from ambient values above 3000 K. The Sondrestrom radar shows an enhancement of the electron density after 21:00 UT, also coinciding with electron temperature values of 2000 K. The coincidence of high electron density and low temperature indicate that the plasma was transported rather than created locally, for example, by soft particle precipitation (Blelly et al, 2005). In particular, an F region electron temperature of ∼2000 K is typical for transported dayside mid-latitude plasma .…”

Model‐Based Inversion of Auroral Processes

“…We address this using the TRANSCAR model [Blelly et al, 2005;Lilensten and Blelly, 2002]. TRANSCAR is a 1-D time-dependent flux tube model that solves for the density, drift velocity, temperature, and heat flux for seven different ion species (O + , H + , N + , N 2 + , NO + , O 2 + , and e À ).…”

Auroral ion outflow: low altitude energization

“…The computer model that we use for this case study is TRANSCAR and has been described most recently in (Lilensten et al, 2002;Blelly et al, 2005). TRANSCAR is a one-dimensional time-dependent model of the ionosphere that solves for the density n s , drift velocity u s , temperature T s , and heat flow q s for seven different ion species (s=O + , H + , N + , N + 2 , NO + , O + 2 , and e − ).…”