Modeling transverse heating and outflow of ionospheric ions from the dayside cusp/cleft. 1 A parametric study

Abstract

Abstract. The transport patterns of non-thermal H + and O + field-aligned flows from the dayside cusp/cleft, associated with transverse heating by means of wave-particle interactions and in combination with the poleward motion due to the magnetospheric convection are investigated. This has been accomplished by developing a steady-state, twodimensional, trajectory-based code. The ion heating is modelled by means of a Monte Carlo technique, via the process of ion cyclotron resonance (ICR), with the electromagnetic left-hand circular polarized component of a broad-band, extremely low-frequency (BBELF) turbulence. The altitude dependence of ICR heating from 1000 km to 3 Earth radii (R E ) is modelled by a power law spectrum, with an index α, and a parameter w 0 that is proportional to the spectral density at a referenced gyrofrequency. Because of the finite latitudinal extent of the cusp/cleft, the incorporation of the horizontal convection drift leads to a maximum residence time t D of the ions when being energized. A large set of simulations has been computed so as to study the transport patterns of the H + and O + bulk parameters as a function of t D , α, and w 0 . Residence time effects are significant in O + density patterns while negligible for H + . When comparing the results with analytical one-dimensional theories (Chang et al., 1986;Crew et al., 1990), we find that mean ion energies and pitch angles at the poleward edge of the heating region are slightly influenced by t D and may be used as a probe of ICR parameters (α, w 0 ). Conversely, poleward of the heating region, upward velocity and mean energy dispersive patterns depend mainly on t D (e.g. the magnitude of the convection drift) with latitudinal profiles varying versus t D . In short, the main conclusion of the paper is that any triplet (t D , α, w 0 ) leads to a unique transport-pattern feature of ion flows associated with a cusp/cleft ionospheric source. In a companion paper, by using high-altitude (1.5-3 R E ) ion observations as constraints, the results from the parametric study are used to determine the altitude dependence of transverse ion heatingCorrespondence to: M. Bouhram (bouhram@mpe.mpg.de) during a significant number of passes of the Interball-2 satellite.

The structure of high altitude O<sup>+</sup> energization and outflow: a case study

“…This allows for a change in the relation between parallel and perpendicular temperature, and one may possibly use this for a more advanced velocity dispersion analysis. However, such simulations should be performed with a proper model, such as that of Bouhram et al (2003a), allowing for a proper description of the heating. That model is currently limited to altitudes up to 3 R E , but for the case of 12 April 2001 that could explain much of the observations.…”

Modeling transverse heating and outflow of ionospheric ions from the dayside cusp/cleft. 2 Applications

“…Then, we develop a procedure for finding the altitude dependence of ICR heating for any data set in the high-altitude cusp/cleft under the absence of field-aligned potential drops. This has been accomplished using a large set of numerical simulations from a two-dimensional, steadystate, Monte Carlo, trajectory-based code, as discussed in detail in the first companion paper (Bouhram et al, 2003).The procedure is applied and tested successfully for the first two events, by using patterns of ion moments along the satellite track as constraints. Then, we present a statistical study that uses 25 cusp/cleft crossings associated with steady IMF conditions, where ICR heating is expected to occur alone.…”

High-altitude and high-latitude O<sup>+</sup> and H<sup>+</sup> outflows: the effect of finite electromagnetic turbulence wavelength

“…In another series of papers, Bouhram et al (2002Bouhram et al ( , 2003aBouhram et al ( , b, 2004) studied the transverse heating and outflow of ions in the cusp/cleft region. Bouhram et al (2002) studied the spatial properties of ionospheric ion outflows associated with perpendicular heating processes in the cusp using a conjunction study from two satellites and ground radar system.…”

“…They found that any triplet of (residence time of the ions when being energized, α, and ω 0 ) leads to a unique transport pattern feature of ion flows associated with a cusp/cleft ionospheric source. Bouhram et al (2003b) used high-altitude (1.5-3 R E ) ion observation as constraints and the results of Bouhram et al (2003a) are used to determine the altitude dependence of transverse ion heating during a significant number of the Interball-2 satellites. Bouhram et al (2004) focused on the altitude dependence of oxygen ion conics in the dayside cusp/cleft region.…”

“…They found that since broadband extremely lowfrequency turbulence is available to pre-heat the ions up to non-thermal energies, Lower Hybrid waves may provide additional energization up to keV energies for O + ions at high altitude. Bouhram et al (2003a), developed a two-dimensional, Monte Carlo, trajectory-based code for ion outflow from the dayside cusp/cleft, which is associated with transverse ion heating. They modeled the altitude dependence of ion cyclotron resonance heating from 1000 km to 3 R E by a power law spectrum with an index α, and a parameter ω 0 that is proportional to the spectral density at a referenced frequency.…”