Self-consistent model of magnetospheric electric field, ring current, plasmasphere, and electromagnetic ion cyclotron waves: Initial results (original) (raw)
Related papers
Journal of Geophysical Research, 2007
1] The further development of a self-consistent theoretical model of interacting ring current ions and electromagnetic ion cyclotron waves is presented. In order to adequately take into account wave propagation and refraction in a multi-ion magnetosphere, we explicitly include the ray tracing equations in our previous self-consistent model and use the general form of the wave kinetic equation. This is a major new feature of the present model and, to the best of our knowledge, the ray tracing equations for the first time are explicitly employed on a global magnetospheric scale in order to self-consistently simulate the spatial, temporal, and spectral evolution of the ring current and of electromagnetic ion cyclotron waves. To demonstrate the effects of EMIC wave propagation and refraction on the wave energy distribution and evolution, we simulate the May 1998 storm. The main findings of our simulation can be summarized as follows. First, owing to the density gradient at the plasmapause, the net wave refraction is suppressed, and He + -mode grows preferably at the plasmapause. This result is in total agreement with previous ray tracing studies and is very clearly found in presented B field spectrograms. Second, comparison of global wave distributions with the results from another ring current model reveals that this new model provides more intense and more highly plasmapause-organized wave distributions during the May 1998 storm period. Finally, it is found that He + -mode energy distributions are not Gaussian distributions and most important that wave energy can occupy not only the region of generation, i.e., the region of small wave normal angles, but all wave normal angles, including those to near 90°. The latter is extremely crucial for energy transfer to thermal plasmaspheric electrons by resonant Landau damping and subsequent downward heat transport and excitation of stable auroral red arcs.
Quasi-Static Modelling of the Ionosphere-Magnetosphere Coupling: Ionospheric Localized Effects
The physical processes that take place in the auroral ionosphere (activation of auroral arcs at various spatial scales, plasma irregularities, non-homogeneities of the electric conductivity) are linked with the dynamics of the distant magnetosphere; the same geomagnetic field lines connect the polar ionosphere and the distant magnetosphere. Inside the magnetosphere the plasma parameters (temperature, density, bulk velocity) are non-uniform. We develop a stationary model that predicts the amplitude of the ionospheric perturbations corresponding to magnetospheric sheared flows. In this study we investigate the sheared plasma flows encountered close to the outer magnetospheric boundary layers. The main components of the model are:(i) a kinetic tangential discontinuity that plays the role of a magnetospheric generator; (ii) a current-voltage relationship describing the flux of generator particles precipitating into the ionosphere as well as the flux o the ionospheric outflow and (iii) a simple model of the topside ionosphere. The solution of the current continuity equation at topside ionosphere gives the latitudinal variation of the ionospheric electrostatic potential and of the field aligned potential drop. Our model provides a tool for evaluating the ionospheric effects of a distant dynamic magnetosphere. Ionospheric perturbations (especially conductivity irregularities) constitute a threat for satellite communications (including GPS) as well as for radio-wave navigation systems. UNCLASSIFIED/UNLIMITED Echim, M.; Roth, M.; De Keyser, J. (2006) Quasi-Static Modelling of the Ionosphere-Magnetosphere Coupling: Ionospheric Localized Effects. In Emerging and Future Technologies for Space Based Operations Support to NATO Military Operations (pp. P4-1 -P4-8). Meeting Proceedings RTO-MP-RTB-SPSM-001, Poster 4. Neuilly-sur-Seine, France: RTO. Available from: http://www.rto.nato.int/abstracts.asp.
Initial results from a dynamic coupled magnetosphere-ionosphere-ring current model
Journal of Geophysical Research, 2012
In this paper we describe a coupled model of Earth's magnetosphere that consists of the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamics (MHD) simulation, the MIX ionosphere solver and the Rice Convection Model (RCM) and report some results using idealized inputs and model parameters. The algorithmic and physical components of the model are described, including the transfer of magnetic field information and plasma boundary conditions to the RCM and the return of ring current plasma properties to the LFM. Crucial aspects of the coupling include the restriction of RCM to regions where field-line averaged plasma-b ≤ 1, the use of a plasmasphere model, and the MIX ionosphere model. Compared to stand-alone MHD, the coupled model produces a substantial increase in ring current pressure and reduction of the magnetic field near the Earth. In the ionosphere, stronger region-1 and region-2 Birkeland currents are seen in the coupled model but with no significant change in the cross polar cap potential drop, while the region-2 currents shielded the low-latitude convection potential. In addition, oscillations in the magnetic field are produced at geosynchronous orbit with the coupled code. The diagnostics of entropy and mass content indicate that these oscillations are associated with low-entropy flow channels moving in from the tail and may be related to bursty bulk flows and bubbles seen in observations. As with most complex numerical models, there is the ongoing challenge of untangling numerical artifacts and physics, and we find that while there is still much room for improvement, the results presented here are encouraging.
Non-potential electric field model of magnetosphere-ionosphere coupling
2005
A new model is proposed to describe the electrodynamic coupling between the magnetosphere and ionosphere. In contrast with existing models, the ionospheric electric field is not assumed to be a potential field. The equation coupling the electric currents flowing into the ionosphere to the ionospheric electric fields is integrated analytically. This approach results in a simple, local and physically reasonable boundary condition, coupling the local tangential plasma velocity values in the mag netosphere to the tangential magnetic field through a properly integrated ionospheric conductivity. For simplified test cases the simulation results are in good agreement with those obtained with a traditional ionospheric electric potential model. The proposed approach improves computational efficiency and also allows prediction of the electromotive forces acting on closed electric current loops at the surface of the Earth. Such electric current loops can be induced by non-potential electric fields, generated by rapid changes in the ionosphere and magnetosphere.
Journal of Geophysical Research, 2002
Initial results from a newly developed model of the interacting ring current ions and ion cyclotron waves are presented. The model is based on the system of two kinetic equations: one equation describes the ring current ion dynamics, and another equation describes wave evolution. The system gives a self-consistent description of the ring current ions and ion cyclotron waves in a quasilinear approach. These equations for the ion phase space distribution function and for the wave power spectral density were solved on aglobal magnetospheric scale undernonsteady state conditions during the 2-5 May 1998 storm. The structure and dynamics of the ring current proton precipitating flux regions and the ion cyclotron wave-active zones during extreme geomagnetic disturbances on 4 May 1998 are presented and discussed in detail.
Simulation of electromagnetic ion cyclotron triggered emissions in the Earth's inner magnetosphere
Journal of Geophysical Research, 2011
1] In a recent observation by the Cluster spacecraft, emissions triggered by electromagnetic ion cyclotron (EMIC) waves were discovered in the inner magnetosphere. We perform hybrid simulations to reproduce the EMIC triggered emissions. We develop a self-consistent one-dimensional hybrid code with a cylindrical geometry of the background magnetic field. We assume a parabolic magnetic field to model the dipole magnetic field in the equatorial region of the inner magnetosphere. Triggering EMIC waves are driven by a left-handed polarized external current assumed at the magnetic equator in the simulation model. Cold proton, helium, and oxygen ions, which form branches of the dispersion relation of the EMIC waves, are uniformly distributed in the simulation space. Energetic protons with a loss cone distribution function are also assumed as resonant particles. We reproduce rising tone emissions in the simulation space, finding a good agreement with the nonlinear wave growth theory. In the energetic proton velocity distribution we find formation of a proton hole, which is assumed in the nonlinear wave growth theory. A substantial amount of the energetic protons are scattered into the loss cone, while some of the resonant protons are accelerated to higher pitch angles, forming a pancake velocity distribution.
Journal of Atmospheric and Solar-Terrestrial Physics, 2015
Behaviors of the integrated wave gain of electromagnetic ion cyclotron (EMIC) waves in the H + -He + plasma of the inner magnetosphere is investigated. The integrated wave gain is obtained by integration of a temporal local growth rate along a geomagnetic field line. The local growth rate is determined by the method of generalized on the case of a bi-ion plasma. The concentration of the cold plasma is obtained on a basis of an empirical model of the plasmasphere and trough by . The energetic proton flux in the equatorial inner magnetosphere is set by the empirical model of , which refers to the conditions of low geomagnetic activity. The coefficients of EMIC wave reflection from the conjugated ionosphere are calculated using the International Reference Ionosphere (IRI) model. It is shown that the integrated wave gain of the EMIC waves increases with L -shell increasing and peaks around 14-20 MLT. In the afternoon sector the integrated wave gain reaches maximum in the cold plasma of higher density. Here the EMIC waves with the frequency below the equatorial He + gyrofrequency will be generated. The main findings of our study are in agreement with the basic experimental results on the EMIC wave occurrence in the equatorial middle magnetosphere known from satellite observations.
Journal of Geophysical Research, 1992
The dynamic processes in the plasma along high-latitude field lines plays an important role in ionosphere-magnetosphere coupling process. We have created a time-dependent, large-scale simulation of these dynamics parallel to the geomagnetic field lines from the ionosphere well into the magnetosphere. The plasma consists of hot e-and H-I-of magnetospheric origin and low-energy e-, H-I-, and O-[-of ionospheric origin. Including multiple electron species, a major improvement to the model, has allowed us for the first time to simulate the upward current region properly and to dynamically simulate the diodelike response of the field-line plasma to the parallel currents coupling the ionosphere and magnetosphere. It is shown that return currents flow with small resistance, while upward currents produce kilovolt-sized potential drops along the field, as concluded from satellite observations. The kilovolt potential drops are due to the effect of the converging magnetic field on the high-energy magnetospherlc electrons. a natural result of forcing high-energy electrons from the magnetosphere to maintain the upward current by flowing down the converging magnetic field against the resistance of the magnetic mirror, a resistive effect which does not occur for the upward-flowing low-energy electrons from the ionosphere. It has also been shown [Chiu and Schulz, 1978; Chiu and Cornwall, 1980] that a charged particle population consisting of hot anisotropic magnetospheric plasma, ionospheric plasma evaporated and extracted upward by the parallel electrostatic field, and backscattered electrons can support a potential difference of up to several kilovolts between the equator and the ionosphere along an aurorkl field line. This is not to say that the other theories do not play a role in the maintenance of these potentials. There are still open questions concerning the distribution of potential along the magnetic field line, the dynamic stability of the potential, and the energetic signature of the particle species interacting with the potential.
A family of ionospheric models for different uses
Physics and Chemistry of The Earth Part C-solar-terrestial and Planetary Science, 2000
Empirical models of three dimensional electron density distributions in the ionosphere have been constructed for global as wel1 as regional use. The models differ by their degree of complexity and calculation time and therefore have different uses. Al1 are based on "ionogram parameter" (critical frequenties foE, foF1, foF2 and the F2 region transfer parameter M(3000)F2). The models allow the use of global or regional maps for foF2 and M(3000)F2 and use built-in formulations for foE and foF1. Update (instantaneous mapping / nowcasting) versions exist which take foF2 and M(3000)F2 or F2 region peak height and electron density as input. The ground to F2 layer peak part of the profile is identical for al1 three models and is based on an Epstein formulation. The "quick calculation" model NeQuick uses a simple formulation for the topside F layer, which is essentially a semi-Epstein layer with a thickness parameter which increases linearly with height. The "ionospheric model" COSTprof is the model which was adopted by COST 251 in its regional "monthly median" form. Its topside F layer is based on O+-H+ diffusive equilibrium with built-in maps for three parameters, namely the oxygen scale height at the F2 peak, its height gradient and the O+-H+ transition height. The "ionosphereplasmasphere" model NeUoG-plas uses a magnetic field aligned "plaSmasphere" above COSTprof.