Introduction to Geomagnetically Trapped Radiation

Walt, M.

doi:10.1017/cbo9780511524981

Cited by 266 publications

(239 citation statements)

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“…In contrast, during maximum solar activity Surv Geophys (2010) 31:581-638 593 an increased number of CMEs and solar flares produce high energy solar particles (O'Sullivan 2007). The Van Allen radiation belt contains electrons and protons with energies from several keV up to several hundreds of MeV (Walt 1994); their distribution in time and space depends on solar wind and other parameters. Thus, energetic charged particles (GCRs, SEPs and radiation belt) in the vicinity of the Earth vary with altitude, latitude and stage of solar cycle (Vainio et al 2009).…”

Section: Energetic Particlesmentioning

confidence: 99%

Space Weather: Physics, Effects and Predictability

2010

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The time varying conditions in the near-Earth space environment that may affect space-borne or ground-based technological systems and may endanger human health or life are referred to as space weather. Space weather effects arise from the dynamic and highly variable conditions in the geospace environment starting from explosive events on the Sun (solar flares), Coronal Mass Ejections near the Sun in the interplanetary medium, and various energetic effects in the magnetosphere-ionosphere-atmosphere system. As the utilization of space has become part of our everyday lives, and as our lives have become increasingly dependent on technological systems vulnerable to the space weather influences, the understanding and prediction of hazards posed by these active solar events have grown in importance. In this paper, we review the processes of the Sun-Earth interactions, the dynamic conditions within the magnetosphere, and the predictability of space weather effects on radio waves, satellites and ground-based technological systems today.

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Section: Energetic Particlesmentioning

confidence: 99%

Space Weather: Physics, Effects and Predictability

2010

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“…The McIlwain L-parameter [6] is a parameter describing a set of the Earth's magnetic field lines, in particular those which cross the Earth's magnetic equator at a number of Earth-radii equal to the L-value. Magnetically equivalent positions (from the standpoint of the incoming charged particle) around the world will by definition have the same McIlwain L values, therefore making this parameter particularly convenient for characterizing cutoff rigidities [7].…”

Section: Introductionmentioning

confidence: 99%

In-flight measurement of the absolute energy scale of the Fermi Large Area Telescope

Ackermann¹,

Ajello²,

Allafort³

et al. 2012

Astroparticle Physics

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The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to survey the gamma-ray sky from 20 MeV to several hundreds of GeV. In this energy band there are no astronomical sources with sufficiently well known and sharp spectral features to allow an absolute calibration of the LAT energy scale. However, the geomagnetic cutoff in the cosmic ray electronplus-positron (CRE) spectrum in low earth orbit does provide such a spectral feature. The energy and spectral shape of this cutoff can be calculated with the aid of a numerical code tracing charged particles in the Earth's magnetic field. By comparing the cutoff value with that measured by the LAT in different geomagnetic positions, we have obtained several calibration points between ∼6 and ∼13 GeV with an estimated uncertainty of ∼2%. An energy calibration with such high accuracy reduces the systematic uncertainty in LAT measurements of, for example, the spectral cutoff in the emission from gamma ray pulsars.

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“…20 and references therein). This theory was later developed into a unified model according to which the number of particles contained in each magnetic flux tube tends to be homogenized, with the result that a peaked density profile is formed inwardly where the flux tube volume diminishes 18 .…”

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Inward diffusion and acceleration of particles driven by turbulent fluctuations in magnetosphere

et al. 2016

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Charged particles in a magnetosphere are spontaneously attracted to a planet while increasing their kinetic energy via inward diffusion process. A constraint on particles' micro-scale adiabatic invariants restricts the class of motions available to the system, giving rise to a proper frame on which particle diffusion occurs. We investigate the inward diffusion process by numerical simulation of particles on constrained phase space. The results reveal the emergence of inhomogeneous density gradient and anisotropic heating, which is consistent with spacecraft observations, experimental observations, and the recently formulated diffusion model on the constrained phase space.Magnetospheres are the prototypical systems that demonstrate spontaneous confinement of plasmas by magnetic force. Since magnetic force is free of mechanical work, its effect does not appear as an energy term in the Boltzmann distribution (which is in marked contrast with the gravitational confinement created by a star). Instead, the magnetic field manifests itself as topological constraints in the dynamics and equilibrium structures; for example, see Ref. 1 for a recent formulation of magnetic confinement in the perspective of phasespace foliation.The self-organization of a magnetospheric plasma confinement, both in astronomical magnetic dipoles 2,3 and laboratory ones 4-6 , requires a spontaneous mechanism that 'creates' density gradients. As a concomitant effect, particles are accelerated (heated) as they climb up the density gradients 7 ; conservation of first and second adiabatic invariants along the inward displacement increases particle's kinetic energy. The Van Allen radiation belt is believed to be the product of such process [8][9][10] (electrons in an ultra-relativistic regime are created by non-local acceleration mechanisms, such as wave particle interaction [11][12][13] ). Recently, the inward diffusion heating was observed in laboratory magnetosphere experiments 14,15 . As mentioned above, magnetic field does not produce a potential energy (unlike gravity or electrostatic force); hence the concentration and acceleration are not due to centripetal force. The driving force for such 'up-hill diffusion' 16 and acceleration may come from some fluctuations. The key element of the mechanism is, then, the symmetry breaking that selects the preferential direction for particles to penetrate. The symmetry breaking appears in the metric of the phase space; the root cause of an inhomogeneous metric is the topological constraint imposed on magnetized particles by the adiabatic invariants such as magnetic moments 1,17,18 .The early theoretical studies developed an empirical Fokker-Planck type diffusion model on a phase space spanned by adiabatic invariants 19 and explained planetary radiation belt with inhomogeneous density gradients (see Ref. 20 and references therein). This theory was later developed into a unified model according to which the number of particles contained in each magnetic flux tube tends to be homogenized, with the result tha...

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Introduction to Geomagnetically Trapped Radiation

Cited by 266 publications

References 0 publications

Space Weather: Physics, Effects and Predictability

Space Weather: Physics, Effects and Predictability

In-flight measurement of the absolute energy scale of the Fermi Large Area Telescope

Inward diffusion and acceleration of particles driven by turbulent fluctuations in magnetosphere

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