0000000000056577

AUTHOR

Johannes Markkanen

showing 2 related works from this author

Controlled time integration for the numerical simulation of meteor radar reflections

2016

We model meteoroids entering the Earth[U+05F3]s atmosphere as objects surrounded by non-magnetized plasma, and consider efficient numerical simulation of radar reflections from meteors in the time domain. Instead of the widely used finite difference time domain method (FDTD), we use more generalized finite differences by applying the discrete exterior calculus (DEC) and non-uniform leapfrog-style time discretization. The computational domain is presented by convex polyhedral elements. The convergence of the time integration is accelerated by the exact controllability method. The numerical experiments show that our code is efficiently parallelized. The DEC approach is compared to the volume …

010504 meteorology & atmospheric sciencesComputer scienceMETEORPLASMATIC OBJECTSRADAR REFLECTIONS01 natural sciencesplasmatic objectslaw.inventionINTEGRAL EQUATIONSlawRadar010303 astronomy & astrophysicsSpectroscopyEARTH ATMOSPHEREvolume integral equationRadiationPLASMANUMERICAL MODELSMathematical analysisFinite differenceNUMERICAL METHODMETEORSAtomic and Molecular Physics and OpticsCALCULATIONSControllabilityDISCRETE EXTERIOR CALCULUSAstrophysics::Earth and Planetary AstrophysicsMAGNETOPLASMADiscretizationRADAR REFLECTIONTIME DOMAIN ANALYSISVOLUME INTEGRAL EQUATIONdiscrete exterior calculusELECTROMAGNETIC SCATTERINGOpticsFINITE DIFFERENCE TIME DOMAIN METHOD0103 physical sciencesSCATTERINGTime domainmeteorsNUMERICAL METHODS0105 earth and related environmental sciencesta113ta114Computer simulationbusiness.industryta111Finite-difference time-domain methodRADARDiscrete exterior calculuselectromagnetic scatteringradar reflectionsELECTROMAGNETIC METHODmeteoritbusinessJournal of Quantitative Spectroscopy and Radiative Transfer
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How much is enough? : The convergence of finite sample scattering properties to those of infinite media

2021

We study the scattering properties of a cloud of particles. The particles are spherical, close to the incident wavelength in size, have a high albedo, and are randomly packed to 20% volume density. We show, using both numerically exact methods for solving the Maxwell equations and radiative-transfer-approximation methods, that the scattering properties of the cloud converge after about ten million particles in the system. After that, the backward-scattered properties of the system should estimate the properties of a macroscopic, practically infinite system. (C) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.o…

010504 meteorology & atmospheric scienceseducationparticulate random mediapienhiukkasetoptiset ominaisuudet01 natural sciences114 Physical sciencesVolume densityScatteringsymbols.namesakelaskennallinen tiedeConvergence (routing)Radiative transferRadiative transferMaxwellin yhtälötsirontaSpectroscopy0105 earth and related environmental sciencesPhysicsRadiationScatteringscatteringAlbedoSample (graphics)Atomic and Molecular Physics and OpticsComputational physicsWavelengthMaxwell's equationsMaxwell equationsradiative transferParticulate random mediasymbolsapproksimointi
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