Ion cyclotron instability due to the thermal anisotropy of drifting ion species

In a recent study of ion cyclotron waves generated by the thermal anisotropy of oxygen ions, it was shown that the heavy ion drift velocity and a large thermal anisotropy of the heavy ions can destabilize proton-cyclotron waves [Gomberoff and Valdivia, 2003]. Here this study is extended to alpha particles in order to show that a much smaller thermal anisotropy is required to trigger strong proton-cyclotron waves. It is also shown that under some conditions, the alpha particle branch of the dispersion relation becomes unstable for frequency values beyond the proton gyrofrequency. This instability occurs for very large alpha particle thermal anisotropy and very low beta||alpha = vth2/vA2, where vth and vA are the thermal and Alfvén velocity, respectively. The maximum growth rate of this branch of the dispersion relation occurs for drift velocities of the alpha particles larger than those that drive the maximum growth rate of the proton-cyclotron instability. Finally, it is demonstrated that the combined effect of oxygen ions and alpha particles lead to a complex unstable spectrum, and to an enhancement of the proton-cyclotron instability. This mechanism is like a cascade effect in which low-frequency ion cyclotron waves can drive unstable high-frequency ion cyclotron waves through anisotropic heating and acceleration of heavy ions. These results may be relevant to the understanding of the heating process of the fast solar wind in coronal holes

Contribution of Latin–American scientists to the study of the magnetosphere of the Earth. A review

Since the very beginning of the space era, Latin–American scientists have been contributing to the understanding of the magnetosphere of the Earth. This review summarizes some significant contributions in this field with emphasis on results obtained during the last decade. Special attention is paid to most important topics of the magnetosphere of the Earth such as geomagnetic storms and substorms and possible relations between them, interplanetary origin of storms, role of turbulent processes in the magnetosphere dynamics, and analysis of the dynamics of the magnetosphere as a complex self-organized non-linear system

Proton-cyclotron instability induced by the thermal anisotropy of minor ions

We study ion cyclotron instabilities due to the thermal anisotropy of minor heavy ions. Very large thermal anisotropics have been observed in O +5 ions in coronal holes [Cranmer, 2001], and as is well known, the thermal anisotropy of an ion species is the free-energy source of ion cyclotron waves of the corresponding species. Nevertheless, as the heavy ion thermal anisotropy in coronal holes develops, the ions are being heated and accelerated, and therefore they acquire a drift velocity relative to the protons. Owing to the drift velocity a new instability branch develops very close to the proton gyrofrequency. In other words, heavy ion cyclotron waves can also trigger proton-cyclotron waves as a result of the drift velocity of the minor heavy ions. We propose that the proton-cyclotron waves generated by this mechanism are absorbed by the protons, and therefore this process can contribute to fast proton heating in coronal holes

The earth's magnetosphere: a systems science overview and assessment

A systems science examination of the Earth's fully interconnected dynamic magnetosphere is presented. Here the magnetospheric system (a.k.a. the magnetosphere-ionosphere-thermosphere system) is considered to be comprised of 14 interconnected subsystems, where each subsystem is a characteristic particle population: 12 of those particle populations are plasmas and two (the atmosphere and the hydrogen geocorona) are neutrals. For the magnetospheric system, an assessment is made of the applicability of several system descriptors, such as adaptive, nonlinear, dissipative, interdependent, open, irreversible, and complex. The 14 subsystems of the magnetospheric system are cataloged and described, and the various types of magnetospheric waves that couple the behaviors of the subsystems to each other are explained. This yields a roadmap of the connectivity of the magnetospheric system. Various forms of magnetospheric activity beyond geomagnetic activity are reviewed, and four examples of emergent phenomena in the Earth's magnetosphere are presented. Prior systems science investigations of the solar-wind-driven magnetospheric system are discussed: up to the present these investigations have not accounted for the full interconnectedness of the system. This overview and assessment of the Earth's magnetosphere hopes to facilitate (1) future global systems science studies that involve the entire interconnected magnetospheric system with its diverse time and spatial scales and (2) connections of magnetospheric systems science with the broader Earth systems science.NSF Geospace Environment Modeling Program AGS1502947 NASA Heliophysics Living with a Star program NNX16AB75G NNX14AN90G NSF Solar-Terrestrial Program AGS-12GG13659 NSF Solar Heliospheric and Interplanetary Environment program AGS-1723416 NASA Heliophysics Guest Investigator Program NNX17AB71G NNX14AC15G Conicyt ACT1405 Fondecyt 115071

Thermal effects on the propagation of large-amplitude electromagnetic waves in magnetized relativistic electron-positron plasma

The propagation of circularly polarized electromagnetic waves along a constant background magnetic field in an electron-positron plasma is calculated by means of both a fluid and a kinetic theory treatment. In the fluid theory, relativistic effects are included in the particle motion, the wave field, and in the thermal motion by means of a function f, which depends only on the plasma temperature. In this work we analyze the consistency of the fluid results with those obtained from a kinetic treatment, based on the relativistic Vlasov equation. The corresponding kinetic dispersion relation is numerically studied for various temperatures, and results are compared with the fluid treatment. Analytic expressions for the Alfvén velocity are obtained for the fluid and kinetic models, and it is shown that, in the kinetic treatment, the Alfvén branch is suppressed for large temperatures. © 2012 American Physical Society

Temporal evolution of fractality in the Earth's magnetosphere and the solar photosphere

The study of complexity in two aspects of the magnetic activity in the Sun-Earth system is presented. We compare the temporal evolution of the magnetic fluctuations in the Earth's magnetosphere and the spatial distribution of the magnetic field in the solar photosphere, by calculating fractal dimensions from the data. It is found that the fractal dimension of the Dst data decreases during magnetic storm states and is well correlated with other indexes of solar activity, such as the solar flare and coronal indexes. This correlation holds for individual storms, full-year data, and the complete 23rd solar cycle. The fractal dimension from solar magnetogram data also correlates well with both the Dst index and solar flare index, although the correlation is much more clear at the larger temporal scale of the 23rd solar cycle, showing a clear increase around solar maximum. Key Points Calculation of fractal dimension of Dst series and solar photosphere Evolution of fractal dimensions Correla

Controlling the quantum state with a time varying potential

The problem of controlling the quantum state of a system is investigated using a time varying potential. As a concrete example we study the problem of a particle in a box with a periodically oscillating infinite square-well potential, from which we obtain results that can be applied to systems with periodically oscillating boundary conditions. We derive an analytic expression for the frequencies of resonance between states, and against standard intuition, we show how to use this behavior to control the quantum state of the system at will. In particular, we offer as an example the transition from the ground state to the first excited state of the square well potential. At first sight, it may be counter intuitive that we can control the state of such a quantum Hamiltonian, as the Schrodinger equation conserves the norm of the wave function. In this manuscript, we show how that can be achieved.CONICYT-PCHA/Doctorado Nacional 2016-2116103 Fondo Nacional de Investigaciones Cientficas y Tecnologicas (FONDECYT, Chile) 1120399 1150718 CEDENNA through "Financiamiento Basal para Centros Cientficos y Tecnologicos de Excelencia FB080

Ion cyclotron instability triggered by drifting minor ion species: Cascade effect and exact results

On the basis of bi-Maxwellian velocity distribution functions it has been recently shown that the combined effect of heavy ion thermal anisotropy and drift velocity can trigger ion-cyclotron instabilities beyond the corresponding heavy ion-cyclotron frequency. (Proton-cyclotron instability induced by the thermal anisotrophy of minor ions. J. Geophys. Res. 107 (2002) 1494; Ion-cyclotron instability due to the thermal anisotrophy of drifting ion species. J. Geophys. Res. 108 (2003) 1050.) Here we show that the cascade-type mechanism proposed by Gomberoff and Valdivia (2002, 2003) can take place in the region where main heating of the fast solar wind seems to occur (i.e. within 10 solar radii). We also compare some of the results obtained by using the semi-cold approximation with the exact kinetic dispersion relation

Asymptotic, non-linear solutions for ambipolar diffusion in one dimension

Artículo de publicación ISIWe study the effect of the non-linear process of ambipolar diffusion (joint transport of magnetic flux and charged particles relative to neutral particles) on the long-term behaviour of a non-uniform magnetic field in a one-dimensional geometry. Our main focus is the dissipation of magnetic energy inside neutron stars (particularly magnetars), but our results have a wider application, particularly to the interstellar medium and the loss of magnetic flux from collapsing molecular cloud cores. Our system is a weakly ionized plasma in which neutral and charged particles can be converted into each other through nuclear beta decays (or ionizationrecombination processes). In the ‘weak-coupling’ limit of infrequent inter-particle interactions, the evolution of the magnetic field is controlled by the beta decay rate and can be described by a non-linear partial integro-differential equation. In the opposite, ‘strong-coupling’ regime, the evolution is controlled by the inter-particle collisions and can be modelled through a non-linear diffusion equation.We show numerically that, in both regimes, ambipolar diffusion tends to spread out the magnetic flux, but, contrary to the normal Ohmic diffusion, it produces sharp magnetic-field gradients with associated current sheets around those regions where the magnetic field is weak.This work was financed by the Gemini-CONICYT Fund, project no 32070014; FONDECYT regular projects 1060644 and 1070854; the FONDAP Center for Astrophysics (15010003); Proyecto Basal PFB-06/2007 and the joint project ‘Estudio Computacional del decaimiento de campos magn´eticos en estrellas de neutrones’ between Universidad de Medell´ın (Summa Group), Pontificia Universidad Cat´olica de Chile and Universidad de Chile. The post-doctoral stay of JHH at Astrophysikalisches Institut Potsdam was possible due to the financial support of Deutscher Akademischer Austauschdienst (DAAD), Germany, and Comisi´on Nacional de Investigaci´on Cientifica y Tecnol´ogica (CONICYT), Chile, through the postdoctoral fellowship no A0772255-2007-07-DOCDAAD-25. We also thank the FONDECYT International Cooperation Project 7090020

Spatial distribution of the eddy diffusion coefficients in the plasma sheet during quiet time and substorms from THEMIS satellite data

During the last decade, a number of studies have shown that turbulent processes in the plasma sheet are very important for the analysis of the formation of quasi-stable plasma sheet configurations. The existence of this turbulence provides a self-consistent approach to study the dynamics of the Earth's magnetosphere, including the plasma sheet stability. The turbulence can also be very important for an understanding of the location of an isolated substorm expansion phase onset. In this study the level of turbulence has been evaluated by calculating the eddy diffusion coefficients using the Time History of Events and Macroscale Interactions during Substorms satellite data. It was found that the value of the eddy diffusion coefficients may vary by at least 3 orders of magnitude, generally ranging from 103 to 106 km2/s, increasing with the distance from the Earth. The area of low eddy diffusion coefficients, less than 104 km2/s, is situated at distances below 12 RE in the tail where we f