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Reconstructing ICMEs with the toroidal Grad-Shafranov method
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
2019 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The main objective of this thesis is to model the magneticstructure of interplanetary coronal mass ejections (ICME) measuredin-situ from the WIND spacecraft positioned at L1. The modeling isdone by a magnetohydrodynamic reconstruction technique based onthe GS equation with a toroidal geometry. The purpose has been toextend the application of the reconstruction program to real dataand to test its performance when different input parameters arechanged. Two events are presented; 16-17 May 2012 and 15-16 May2005 ICMEs have been successfully reconstructed with this model.

The main achievements of the study are that a) the code now worksfor real data b) the important parameters that can be changed fordifferent reconstructions in the code are the number of iterationsused to find the optimal Z-axis, the plasma pressure and the orderof the polynomial fitting of the flux functional, c) if all crosssection reconstructions for different variations of theseparameters strongly resembles each other then this is anindication that the model approximation is good and that the fluxrope exists. The results have been compared and verified withpreviously published studies of these events.

Using a toroidal geometry for the GS reconstruction method weobtain very similar results to the one obtained with differentreconstruction techniques.This implies that at L1, the ICMEs haveexpanded so much that a cylindrical geometry is sufficient todescribe the flux rope geometry. The toroidal Grad-Shafranovreconstruction technique is best suited for circular, or slightlyelongated, flux rope cross section profiles but have been provento work for one complex ejecta consisting of two merged fluxropes. The toroidal model might become an important asset in thefuture when data from spacecraft closer to the Sun, such as ParkerSolar Probe and Solar Orbiter, is public. When the major radius ofthe flux rope is smaller the choice of geometry will most likelyhave a larger role than for measurements at L1 and so, thetoroidal Grad-Shafranov reconstruction technique will probably bethe better alternative of the models that exists today.

Place, publisher, year, edition, pages
2019. , p. 48
Series
UPTEC F, ISSN 1401-5757 ; 19009
Keywords [en]
space physics, plasma, coronal mass ejections, interplanetary coronal mass ejections
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:uu:diva-382398OAI: oai:DiVA.org:uu-382398DiVA, id: diva2:1306748
Educational program
Master Programme in Engineering Physics
Supervisors
Examiners
Available from: 2019-04-26 Created: 2019-04-24 Last updated: 2019-04-26Bibliographically approved

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Swedish Institute of Space Physics, Uppsala Division
Fusion, Plasma and Space Physics

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