Magnetic Reconnection: A Kinetic Treatment

Adaptive Multi-Physics Simulations of Collisionless Plasmas

10.5194/egusphere-egu21-6242 ◽

2021 ◽

Author(s):

Simon Lautenbach ◽

Rainer Grauer

Keyword(s):

Magnetic Reconnection ◽

Vlasov Equation ◽

Fluid Model ◽

Environmental Modeling ◽

Landau Damping ◽

Proof Of Concept ◽

Collisionless Plasmas ◽

Space Environments ◽

Small Parts ◽

Kinetic Treatment

<p>Collisionless plasmas, mostly present in astrophysical and space environments, often require a kinetic treatment given by the Vlasov equation. Unfortunately, the six-dimensional Vlasov equation is inherently expensive to compute and usually can only be solved on very small parts of the considered spatial domain. However, in some cases, e.g. magnetic reconnection, it is sufficient to solve the Vlasov equation in a localized domain and solve the remaining domain with appropriate fluid models. We present an adaptive hierarchical treatment of collisionless plasmas ranging from fully kinetic, to a 10-moment fluid model incorporating a simplified treatment of Landau damping, to a 5-moment fluid description. To account for separation of electron and ion physics, hybrid stages of mixed electron and ion models are also allowed. As a proof of concept, the full physics-adaptive hierarchy is applied to the Geospace Environmental Modeling (GEM) challenge of magnetic reconnection.</p>

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A large rotating structure around AB Doradus A at VLBI scale

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319009785 ◽

2019 ◽

Vol 15 (S354) ◽

pp. 189-194

Author(s):

J. B. Climent ◽

J. C. Guirado ◽

R. Azulay ◽

J. M. Marcaide

Keyword(s):

Magnetic Reconnection ◽

Main Sequence ◽

Complex Structure ◽

Main Sequence Star ◽

Polar Cap ◽

Vlbi Observations ◽

Rotating Structure ◽

Source Structure ◽

Expected Position

AbstractWe report the results of three VLBI observations of the pre-main-sequence star AB Doradus A at 8.4 GHz. With almost three years between consecutive observations, we found a complex structure at the expected position of this star for all epochs. Maps at epochs 2007 and 2010 show a double core-halo morphology while the 2013 map reveals three emission peaks with separations between 5 and 18 stellar radii. Furthermore, all maps show a clear variation of the source structure within the observing time. We consider a number of hypothesis in order to explain such observations, mainly: magnetic reconnection in loops on the polar cap, a more general loop scenario and a close companion to AB Dor A.

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