b'Mark Lackies best of Exploration GeophysicsFeatureMagnetic Exploration Models incorporating Remanence, Demagnetisation and Anisotropy: HP 41C Handheld Computer AlgorithmsD. W. Emerson1, D. A. Clark2 and S. J. Saul3 Resultant magnetisation calculation, program VECT, taking account of isotropic or anisotropic susceptibility, remanence 1Department of Geology & Geophysics, University of Sydney,anddemagnetization (approximate) for a 2D sheet .43NSW2006, Australia2CSIRO Division of Mineral Physics, Delhi Road, North Ryde,MAGMOD VIllA: Dipping 2D Tabular Body with susceptibility, NSW2113, Australia remanence and demagnetization (approximate) 443Austirex International Ltd, 586 Pacific Highway, Chatswood, NSW2067, Australia MAGMOD VIIIB: Dipping 2D Tabular Body with anisotropic susceptibility, remanence and demagnetizationThe program material contained herein is supplied without(approximate).44representation or warranty of any kind. Despite the extensive checking and editing that preceded publication, the authors,Notes on the ellipsoid of revolution incorporating susceptibility the ASEG, the publishers, or equipment manufacturers accept oranisotropy, remanence and demagnetizalion .47assume no responsibility whatsoever and shall have no liability,MAG MOD XI A: Prolate Ellipsoid of Revolution 53consequential or otherwise, for the use, performance and results of these programs or for any actions that may follow the usageMAG MOD XI B: Oblate Ellipsoid of Revolution .56of these programs. No claims whatsoever are made or implied regarding the elegance or accuracy of the programs. Errors may2D Elliptic Cylinder- notation and formulae58come to light as the programs are used; users should documentMAGMOD XII: 2D Elliptic Cylinder.62any such errors and notify the ASEG so that revisions can be made. The programs were designed as a learning aid for the teachingNotes on the vertical rectangular prism- formulae; remanence, and understanding of applied magnetics. They are not intended toinduction, demagnetization and anisotropy .64compete with sophisticated large computer packages. However,MAG MOD XIII: Vertical Rectangular Prism 67they may be useful to practising professional field geophysicists in preliminary analyses of magnetic data. Program listings and register contents.69Computation of B H 111Contents Addendum: Notes on the vertical circular cylinder (solid and Page annular cylinders)- formulae; remanence and induction; demagnetization and anisotropy.113Abstract.2MAG MOD XIV: Vertical circular cylinder116Preface 2 Coordinate system .5 AbstractMeasured and calculated magnetic anomalies.6 Handheld computer (HP 41C) algorithms are presented for basic Notation 8. and advanced magnetic exploration models along principal profiles. The thirteen models are: monopole, 2D line of poles, Magnetic Models I-IX, Key Figures .10 sheet of poles, dipole, 2D line of dipoles, 2D horizontal sheet of dipoles, 2D dipping thin sheet, 2D dipping thick sheet, 2D MAGMOD Formulae-Principal profiles .12 sloping step, 2D body with polygonal cross section, prolate Vector Addition, Program VALG, induced and remanentand oblate ellipsoids of revolution, 2D elliptic cylinder, vertical magnetisation . 16 rectangular prism. Key diagrams, program useage instructions, worked numerical example, program listing and register Basic Magnetic Models contents are given for each model. Induction, remanence, MAGMOD I: Monopole .18 demagnetisation and susceptibility anisotropy effects are MAGMOD II: Line of Poles .20 calculated. The vertical circular and annular cylinders are treated MAGMOD Ill: Sheet of Poles .22 for the cases of induction and remanence.MAGMOD IV: Point Dipole-Sphere 24MAG MOD V: Line of Dipoles .26 PrefaceDemagnetisation corrections for MAGMODS I-V .28MAG MOD VI: Horizontal Thin Sheet Of Dipoles .29 This is a presentation of magnetic computational techniques for MAGMOD VII: Dipping 2D Thin Sheet .29 modelling residual or regional anomalies (but not for separating MAGMOD VIII: Dipping 2D Thick Sheet 32 them). It does not include a detailed theoretical development. MAG MOD IX: Sloping Step 34 Its purpose is as a working compendium of techniques primarily MAGMOD X: 2D Body With Polygonal Cross Section.36 designed to teach and to impart some understanding of the magnetic response of basic modelsmostly simple but Advanced Magnetic Models geologically very important.Notes on incorporating anisotropy and demagnetisationMagnetics has a vital place in all exploration, but often data effectsinto modelling . 39 analysis comprises crude eyeballing or overinterpretation 59 PREVIEW DECEMBER 2020'