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Rönnmark, Kjell
Publikationer (10 of 17) Visa alla publikationer
Markidis, S., Henri, P., Lapenta, G., Rönnmark, K., Hamrin, M., Meliani, Z. & Laure, E. (2014). The fluid-kinetic particle-in-cell method for plasma simulations. Journal of Computational Physics, 271, 415-429
Öppna denna publikation i ny flik eller fönster >>The fluid-kinetic particle-in-cell method for plasma simulations
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2014 (Engelska)Ingår i: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 271, s. 415-429Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

A method that solves concurrently the multi-fluid and Maxwell's equations has been developed for plasma simulations. By calculating the stress tensor in the multi-fluid momentum equation by means of computational particles moving in a self-consistent electromagnetic field, the kinetic effects are retained while solving the multi-fluid equations. The Maxwell's and multi-fluid equations are discretized implicitly in time enabling kinetic simulations over time scales typical of the fluid simulations. The Fluid-Kinetic Particle-in-Cell method has been implemented in a three-dimensional electromagnetic code, and tested against the two-stream instability, the Weibel instability, the ion cyclotron resonance and magnetic reconnection problems. The method is a promising approach for coupling fluid and kinetic methods in a unified framework.

Ort, förlag, år, upplaga, sidor
San Diego: Academic Press, 2014
Nyckelord
Computational plasma physics, Fluid-kinetic particle-in-cell method, Implicit particle-in-cell method
Nationell ämneskategori
Fusion, plasma och rymdfysik
Identifikatorer
urn:nbn:se:umu:diva-90831 (URN)10.1016/j.jcp.2014.02.002 (DOI)000336618800022 ()
Tillgänglig från: 2014-07-24 Skapad: 2014-07-01 Senast uppdaterad: 2018-10-03Bibliografiskt granskad
Marghitu, O., Hamrin, M., Klecker, B., Rönnmark, K., Buchert, S., Kistler, L. M., . . . Rème, H. (2010). Cluster observations of energy conversion regions in the plasma sheet. In: Harri Laakso, Matthew Taylor, C. Philippe Escoubet (Ed.), The Cluster Active Archive: Studying the Earth's Space Plasma Environment. Paper presented at 15th Cluster workshop held in March 2008 (pp. 453-459). Springer Netherlands
Öppna denna publikation i ny flik eller fönster >>Cluster observations of energy conversion regions in the plasma sheet
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2010 (Engelska)Ingår i: The Cluster Active Archive: Studying the Earth's Space Plasma Environment / [ed] Harri Laakso, Matthew Taylor, C. Philippe Escoubet, Springer Netherlands , 2010, s. 453-459Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

Cluster allows for the first time a systematic examination of energy conversion, by the evaluation of the power density, E · J, with E the electric field and J the current density. Following a careful inspection of the Cluster plasma sheet data from the summer and fall of 2001, we selected 43 energy conversion regions (ECRs), out of which 26 concentrated load regions (CLRs, E · J > 0) and 17 concentrated generator regions (CGRs, E · J < 0). As expected in the tail, at about 19 RE geocentric distance, the energy conversion is more intense for CLRs, on average some 25 pW∕m3, compared to some 5 pW∕m3 for CGRs. The CLRs are located closer to the neutral sheet and dominated by E and J in the GSE y direction, unlike the CGRs, that prefer locations towards the plasma sheet boundary layer, where the deviations of E and J from the GSE y direction can be significant. The ECRs are often associated with high speed bulk flows, on average faster and hotter for CLRs. The CLRs appear to be associated also with density drop and sometimes with temperature anisotropy, T > T, features which are observed less frequently for CGRs.

Ort, förlag, år, upplaga, sidor
Springer Netherlands, 2010
Serie
Astrophysics and Space Science Proceedings, ISSN 1570-6591 ; 7
Nationell ämneskategori
Fysik
Identifikatorer
urn:nbn:se:umu:diva-36514 (URN)10.1007/978-90-481-3499-1_32 (DOI)000288478600032 ()978-90-481-3498-4 (ISBN)978-90-481-3499-1 (ISBN)
Konferens
15th Cluster workshop held in March 2008
Tillgänglig från: 2010-10-01 Skapad: 2010-10-01 Senast uppdaterad: 2018-09-04Bibliografiskt granskad
Hamrin, M., Rönnmark, K., Börlin, N. & Vaivads, A. (2008). GALS: gradient analysis by least squares. Annales Geophysicae, 26(11), 3491-3499
Öppna denna publikation i ny flik eller fönster >>GALS: gradient analysis by least squares
2008 (Engelska)Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, nr 11, s. 3491-3499Artikel i tidskrift (Refereegranskat) Published
Nationell ämneskategori
Fusion, plasma och rymdfysik
Identifikatorer
urn:nbn:se:umu:diva-11041 (URN)10.5194/angeo-26-3491-2008 (DOI)
Tillgänglig från: 2008-11-14 Skapad: 2008-11-14 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
Vedin, J. & Rönnmark, K. (2008). Parallel electric fields: variations in space and time on auroral field lines. Journal of Plasma Physics, 74(1), 53-64
Öppna denna publikation i ny flik eller fönster >>Parallel electric fields: variations in space and time on auroral field lines
2008 (Engelska)Ingår i: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 74, nr 1, s. 53-64Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We present results from a particle–fluid simulation of auroral electrons and discuss the distribution of parallel electric fields along auroral field lines and the processes occurring during the build up of these electric fields. Neglecting field-aligned ion dynamics, the main potential drop has a width of about 5000, km and is centered at an altitude of roughly 5000, km. We find that the gradient in the potential becomes steeper and the build up of the potential drop becomes faster if the temperature of the magnetospheric electrons is lower.

Ort, förlag, år, upplaga, sidor
Cambridge University Press, 2008
Nationell ämneskategori
Fusion, plasma och rymdfysik
Identifikatorer
urn:nbn:se:umu:diva-2309 (URN)10.1017/S0022377807006538 (DOI)
Tillgänglig från: 2007-05-08 Skapad: 2007-05-08 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
Vedin, J., Rönnmark, K., Bunescu, C. & Marghitu, O. (2007). Estimating properties of concentrated parallel electric fields from electron velocity distributions. Geophysical Research Letters, 34(16), Article ID L16107.
Öppna denna publikation i ny flik eller fönster >>Estimating properties of concentrated parallel electric fields from electron velocity distributions
2007 (Engelska)Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 34, nr 16, artikel-id L16107Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Information about the magnitude of the field-aligned potential drop along auroral field lines is usually derived from the velocity distribution of the particles. When the electrons are accelerated by a strong double layer their velocity distribution will have features different from those produced by a weak, spread-out, electric field. Quantifying these features, we obtain information about the strength and thickness of the double layer.

Ort, förlag, år, upplaga, sidor
Washington: American Geophysical Union (AGU), 2007
Nyckelord
auroral acceleration region, particle
Nationell ämneskategori
Multidisciplinär geovetenskap
Identifikatorer
urn:nbn:se:umu:diva-16550 (URN)10.1029/2007GL030162 (DOI)000249334400002 ()
Tillgänglig från: 2007-10-05 Skapad: 2007-10-05 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
Vedin, J. & Rönnmark, K. (2007). Implementing a particle-fluid model of auroral electrons. In: Bo Kågström, Erik Elmroth, Jack Dongarra, Jerzy Wasniewski (Ed.), Applied Parallel Computing. State of the Art in Scientific Computing: 8th International Workshop, PARA 2006, Umeå, Sweden, June 18-21, 2006, Revised Selected Papers. Paper presented at 8th International Workshop, PARA 2006, Umeå, Sweden, June 18-21, 2006 (pp. 371-379). Heidelberg: Springer Berlin/Heidelberg
Öppna denna publikation i ny flik eller fönster >>Implementing a particle-fluid model of auroral electrons
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
Serie
Lecture notes in computer science, ISSN 0302-9743 ; 4699
Nationell ämneskategori
Fysik
Identifikatorer
urn:nbn:se:umu:diva-2308 (URN)10.1007/978-3-540-75755-9_45 (DOI)978-3-540-75754-2 (ISBN)
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
Reiniusson, A., Stenberg, G., Norqvist, P., Eriksson, A. & Rönnmark, K. (2006). Enhancement of electric and magnetic wave fields at density gradients. Annales Geophysicae, 24, 367-79
Öppna denna publikation i ny flik eller fönster >>Enhancement of electric and magnetic wave fields at density gradients
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2006 (Engelska)Ingår i: Annales Geophysicae, Vol. 24, s. 367-79Artikel i tidskrift (Refereegranskat) Published
Identifikatorer
urn:nbn:se:umu:diva-11974 (URN)
Tillgänglig från: 2007-03-17 Skapad: 2007-03-17 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
Hamrin, M., Vedin, J., Rönnmark, K., Börlin, N. & Stenberg, G. (2006). GALS: gradient analysis by least squares. In: Proceedings of the 2006 AGU Fall Meeting: . Paper presented at AGU Fall Meeting, San Francisco, USA (pp. SM53A-1442-SM53A-1442). American Geophysical Union
Öppna denna publikation i ny flik eller fönster >>GALS: gradient analysis by least squares
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2006 (Engelska)Ingår i: Proceedings of the 2006 AGU Fall Meeting, American Geophysical Union , 2006, s. SM53A-1442-SM53A-1442Konferensbidrag, Publicerat paper (Övrigt vetenskapligt)
Ort, förlag, år, upplaga, sidor
American Geophysical Union, 2006
Nationell ämneskategori
Fusion, plasma och rymdfysik
Forskningsämne
rymd- och plasmafysik
Identifikatorer
urn:nbn:se:umu:diva-40109 (URN)
Konferens
AGU Fall Meeting, San Francisco, USA
Tillgänglig från: 2011-02-16 Skapad: 2011-02-16 Senast uppdaterad: 2018-06-08Bibliografiskt granskad
Hamrin, M., Marghitu, O., Rönnmark, K., Klecker, B., André, M., Buchert, S., . . . Vaivads, A. (2006). Observations of concentrated generator regions in the nightside magnetosphere by Cluster/FAST conjunctions. Annales Geophysicae, 24, 637-49
Öppna denna publikation i ny flik eller fönster >>Observations of concentrated generator regions in the nightside magnetosphere by Cluster/FAST conjunctions
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2006 (Engelska)Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 24, s. 637-49Artikel i tidskrift (Refereegranskat) Published
Nationell ämneskategori
Fusion, plasma och rymdfysik
Identifikatorer
urn:nbn:se:umu:diva-12250 (URN)10.5194/angeo-24-637-2006 (DOI)
Tillgänglig från: 2007-03-27 Skapad: 2007-03-27 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
Vedin, J. & Rönnmark, K. (2006). Particle-fluid simulation of the auroral current circuit. Journal of Geophysical Research, 111(A12201), 12
Öppna denna publikation i ny flik eller fönster >>Particle-fluid simulation of the auroral current circuit
2006 (Engelska)Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 111, nr A12201, s. 12-Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The incompatibility between stationary kinetic and dynamic fluid descriptions of auroral electron acceleration has been an outstanding problem in space physics for decades. In this study we introduce a new numerical simulation model that provides a unified picture by including electron temperature variations consistent with collisionless kinetic theory in the fluid description. We demonstrate that this new particle-fluid model can describe the partial reflection of Alfvén waves from the acceleration region, as well as the formation of a field-aligned potential drop proportional to the upward current. This study also suggests that for example ion dynamics and high-frequency waves must be added to the model before it properly can describe the return current region. Simulations based on the particle-fluid concept can be applied to various processes in space physics and astrophysics where strong currents flowing along an inhomogeneous magnetic field will cause temperature increases and field-aligned electric fields.

Ort, förlag, år, upplaga, sidor
Washington: American Geophysical Union., 2006
Nyckelord
Alfvén waves, auroral electron acceleration, electron heating
Identifikatorer
urn:nbn:se:umu:diva-12004 (URN)doi:10.1029/2006JA011826 (DOI)
Tillgänglig från: 2007-03-18 Skapad: 2007-03-18 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
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