Phase Space Distributions Of Ions Research Articles

Phase-space Analysis of Ordered and Disordered Nonthermal Ion Energization during Magnetic Reconnection

Anomalous ion heating is frequently observed to accompany magnetic reconnection, yet there is little consensus on its origin. Instead of the usual velocity-space analysis, we use phase-space analysis to exhaustively explain how ions are nonthermally energized during collisionless, antiparallel magnetic reconnection. There are both ordered and disordered aspects in the process; the former is explained in terms of conservative quantities, and the latter is explained by demonstrating chaos through a direct calculation of Lyapunov exponents. The former induces “multibeam-like heating” in all three directions, whereas the latter induces stochastic bulk heating. Profiles of the ion temperature tensor components during reconnection can be easily understood by the phase-space distributions of ions in different motional stages.

Magnetotail‐Inner Magnetosphere Transport Associated With Fast Flows Based on Combined Global‐Hybrid and CIMI Simulation

AbstractUsing the combined Auburn global hybrid simulation code in 3‐D (ANGIE3D) and the Comprehensive Inner Magnetosphere‐Ionosphere (CIMI) model, we investigate the self‐consistent connection of fast flow injections from the tail plasma sheet and the inner magnetosphere under a southward IMF. In the dynamic run, the hybrid results provide the CIMI model with 3‐D magnetic field and the electric potential at the high latitude ionosphere boundary as well as the full ion phase space distribution function at the CIMI outer boundary at the equator. The simulation shows that magnetotail reconnection, which has a dawn‐dusk size of ∼1–5 RE, recurs with a period of several minutes, resulting in recurring localized fast flow injections. Strong ion temperature anisotropy and non‐Maxwellian distributions are present in the fast flows, and the braking of fast flows due to the dipole‐like field results in further perpendicular heating in the injection sources. Multiple fast flow injections lead to multiple peaks in the particle fluxes in the inner magnetosphere as well as layers of upward and downward field‐aligned currents at the ionosphere, and low energy particles penetrate deeper radially than the high energy particles. The combined ANGIE3D‐CIMI model can be used to calculate the global kinetic physics that contains both Region‐1 and Region‐2 field‐aligned currents.

Structure of a strong supernova shock wave and rapid electron acceleration confined in its transition region

A new rapid energization process within a supernova shock transition region (STR) is reported by utilizing numerical simulation. Although the scale of a STR as a main dissipation region is only several hundreds of thousands km, several interesting structures are found relating to generation of a root of the energetic particles. The nonlinear evolution of plasma instabilities lead to a dynamical change in the ion phase space distribution which associates with change of the field properties. As a result, different types of large-amplitude field structures appear. One is the leading wave packet and another is a series of magnetic solitary humps. Each field structure has a microscopic scale (~ the ion inertia length). Through the multiple nonlinear scattering between these large-amplitude field structures, electrons are accelerated directly. Within a STR, quick thermalization realizes energy equipartition between the ion and electron, hot electrons play an important role in keeping these large-amplitude field structures on the ion-acoustic mode. The hot electron shows non-Maxwellian distribution and could be the seed of further non-thermal population. The "shock system", where fresh incoming and reflected ions are supplied constantly, play an essential role in our result. With a perpendicular shock geometry, the maximum energy of the electron is estimated by equating a width of the STR to a length of the Larmor radius of the energetic electron. Under some realistic condition of M_A = 170 and \omega_{pe}/\Omega_{ce} = 120, maximum energy is estimated to ~ 10 MeV at an instant only within the STR.

Correlated phase space distributions of ions in an orthogonal time-of-flight mass spectrometer

A prototype orthogonal time-of-flight (oTOF) mass spectrometer equipped with a thermal ionization (TI) source and an electron impact (EI) source was designed and constructed. Low energy ion beams (∼10 eV) were generated and ejected by a two-stage acceleration configuration into the TOF mass analyzer operating in the linear mode. Interfaces between the sources and the analyzer were optimized so as to reduce the contribution of the turn-around time on the final resolving power of the instrument. The concept of space-velocity correlated ion beams is described in this context. Experiments with variable detector positions were performed and spectral line widths of ∼2 ns were achieved at the end of a 45 cm long linear oTOF MS with ∼3.7 keV energy ions. A new theoretical approach is developed for linear phase space distributions of ions at the start of the TOF experiment. Analytical solutions for first and second-order focusing instruments are presented.

Feasibility study of fast ion diagnosis in ITER by collective Thomson scattering, millimeter waves to CO2 laser

Here we report on a study of the feasibility of measuring the fast ion phase space distribution in the International Thermonuclear Experimental Reactor (ITER) by collective Thomson scattering (CTS). The study covers the full range of potential probe frequencies from gyrotron based millimeter waves to the infrared of the CO2 laser. It is assessed whether the systems can meet the ITER measurement requirements and which technological developments may be required. The relative merits of the systems are compared. The study reveals that a CTS system based on a 60 GHz probe has the highest diagnostic potential, and is the only system expected to be able to meet all the ITER fast ion measurement requirements with existing or near term technology. With modest additions this system may also provide measurements of the fuel ion ratio.

Recent results from the Oxford EBIT

Here we summarise the present status of the experimental programme of the Oxfordelectron beam ion trap. Most notably this research has recently culminated in the successful measurementof the 2s1/2–2p3/2 transition in hydrogenlike nitrogen by a laser resonance method. We also introduce preliminary results from some computational investigations of both electron beam transport and the trapped ion ensemble. In particular, we show that the contribution of the magneticfield to ion confinement has a potentially measurable effect on the ion phase space distribution.

A self‐consistent model of the interacting ring current ions and electromagnetic ion cyclotron waves, initial results: Waves and precipitating fluxes

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 a global magnetospheric scale under nonsteady 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.

Design study of the fragment recoil separator ETNA

The secondary beam line ETNA (Exotics Transport to Nuclear Area) has been designed at LNS to separate unstable nuclei produced in high-energy heavy-ion reactions. The separation is performed according to the magnetic rigidity and energy loss in matter. Being a section of the extraction line of the Superconducting Cyclotron ( K = 800), ETNA is supposed to work both as a beam transport line and as a fragment recoil separator. Ion optical properties of ETNA have been optimized up to the second order. To have phase space distributions of ions in two focal planes of the separator Monte Carlo tests have been performed with the code RAYTRACE. Angular and momentum stragglings in the degrader have been taken into account in the tests to obtain the expected beam profiles.