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Implementing a particle-fluid model of auroral electrons
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
2007 (Engelska)Ingår i: Applied Parallel Computing. State of the Art in Scientific Computing: 8th International Workshop, PARA 2006, Umeå, Sweden, June 18-21, 2006, Revised Selected Papers / [ed] Bo Kågström, Erik Elmroth, Jack Dongarra, Jerzy Wasniewski, Heidelberg: Springer Berlin/Heidelberg, 2007, s. 371-379Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

The particle-fluid model of auroral electrons that is presented in [1] is a major step forward within the field of dynamic models of the auroral generation mechanisms. The model is, however, also an example where the implementation of a physical model requires a lot of knowledge from the field of computer science. Therefore, this paper contains a detailed description of the implementation behind the particle-fluid model. We present how the particles are implemented in doubly linked lists, how the fluid equations are solved in a time-efficient algorithm, and how these two parts are coupled into a single framework. We also describe how the code is parallelized with an efficiency of nearly 100%.

Ort, förlag, år, upplaga, sidor
Heidelberg: Springer Berlin/Heidelberg, 2007. s. 371-379
Serie
Lecture notes in computer science, ISSN 0302-9743 ; 4699
Nationell ämneskategori
Fysik
Identifikatorer
URN: urn:nbn:se:umu:diva-2308DOI: 10.1007/978-3-540-75755-9_45ISBN: 978-3-540-75754-2 (tryckt)OAI: oai:DiVA.org:umu-2308DiVA, id: diva2:140250
Konferens
8th International Workshop, PARA 2006, Umeå, Sweden, June 18-21, 2006
Tillgänglig från: 2007-05-08 Skapad: 2007-05-08 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
Ingår i avhandling
1. Numerical modeling of auroral processes
Öppna denna publikation i ny flik eller fönster >>Numerical modeling of auroral processes
2007 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

One of the most conspicuous problems in space physics for the last decades has been to theoretically describe how the large parallel electric fields on auroral field lines can be generated. There is strong observational evidence of such electric fields, and stationary theory supports the need for electric fields accelerating electrons to the ionosphere where they generate auroras. However, dynamic models have not been able to reproduce these electric fields. This thesis sheds some light on this incompatibility and shows that the missing ingredient in previous dynamic models is a correct description of the electron temperature. As the electrons accelerate towards the ionosphere, their velocity along the magnetic field line will increase. In the converging magnetic field lines, the mirror force will convert much of the parallel velocity into perpendicular velocity. The result of the acceleration and mirroring will be a velocity distribution with a significantly higher temperature in the auroral acceleration region than above. The enhanced temperature corresponds to strong electron pressure gradients that balance the parallel electric fields. Thus, in regions with electron acceleration along converging magnetic field lines, the electron temperature increase is a fundamental process and must be included in any model that aims to describe the build up of parallel electric fields. The development of such a model has been hampered by the difficulty to describe the temperature variation. This thesis shows that a local equation of state cannot be used, but the electron temperature variations must be descibed as a nonlocal response to the state of the auroral flux tube. The nonlocal response can be accomplished by the particle-fluid model presented in this thesis. This new dynamic model is a combination of a fluid model and a Particle-In-Cell (PIC) model and results in large parallel electric fields consistent with in-situ observations.

Ort, förlag, år, upplaga, sidor
Umeå: Fysik, 2007. s. 65
Nyckelord
space plasma physics, auroral acceleration region, auroral current circuit, Alfvén waves, parallel electric fields, equation of state, fluid simulation, PIC simulation
Nationell ämneskategori
Fusion, plasma och rymdfysik
Identifikatorer
urn:nbn:se:umu:diva-1117 (URN)978-91-7264-294-2 (ISBN)
Disputation
2007-06-05, MA121, MIT-huset, Umeå University, 13:00
Opponent
Handledare
Tillgänglig från: 2007-05-08 Skapad: 2007-05-08 Senast uppdaterad: 2018-06-09Bibliografiskt granskad

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