[IGPP Everyone] Plasma Seminar Thursday 12/3, 2pm: The Multi Domain PIC method (M.E. Innocenti, U. Leuven)

[Emmanuel V. Masongsong]

FYI...

----- Forwarded Message -----
From: "Seth E Dorfman" <sethd at physics.ucla.edu>
To: "cmpd seminar" <cmpd_seminar at lists.ucla.edu>, bapsf at lists.ucla.edu

Dear all,

We have a plasma seminar this Thursday, December 3rd at 2PM in Room 
4-330 of the Physics & Astronomy Building (PAB).  Coffee and cookies 
will be available in the room at 1:45.  Our speaker is Dr. Maria Elena 
Innocenti of the University of Leuven, and her title and abstract are as 
follows:

"The Multi Domain method, a semi-implicit adaptive method for fully 
kinetic Particle In Cell simulations"

Fully kinetic Particle In Cell (PIC) simulations with the ambition of 
realistically representing both ion and electron dynamics have to be 
able to cope with the huge scale separation between electron and 
parameters while respecting strict stability constraints. This often 
results in computational costs so high to seriously limit the extension 
and duration of the simulations. Many alternatives are available to 
reduce the computational costs of PIC simulations. Semi implicit methods 
(Vu and Brackbill, 1992; Lapenta et al., 2006; Cohen et al., 1989) can 
bypass the strict stability constraints of explicit PIC codes. Adaptive 
Mesh Refinement (AMR) techniques (Vay et al., 2004; Fujimoto and Sydora, 
2008) can be employed to change locally the resolution of the simulation.

We focus here on the Multi Level Multi Domain (MLMD) method introduced 
in Innocenti et al. (2013), Beck et al. (2014), Innocenti et al (2015). 
The method combines the advantages of semi-implicit algorithms and 
adaptivity. Two grid levels are fully simulated with fields and 
particles. Different spatial and temporal resolutions are used at the 
different levels, with jumps in spatial and temporal resolution reaching 
up to 14 and 10 respectively. These large resolution jumps are allowed 
by the Implicit Moment Method used. The aim is to resolve ion scale 
processes in the less resolved grid, electron scale processes in the 
higher resolution areas.

MLMD simulations with standard parameters have been measured to be 70 
times cheaper than their single grid, semi-implicit counterparts.

The MLMD method is demonstrated with simulations of collisionless 
magnetic reconnection and turbulence generated by the Lower Hybrid Drift 
Instability. In magnetic reconnection, the characteristic Ion and 
Electron Diffusion Regions (IDR and EDR) develop at the ion and electron 
scales respectively (Daughton et al., 2006): electron scale resolution 
can be used in the EDR only. In turbulence simulations, a mixed grid 
spectrum is obtained by joining the solutions calculated on the grids 
evolved with the different resolutions. This extends the simulated 
wavenumber range of a factor proportional to the resolution jump at a 
cost only roughly double with respect to simulating the low resolution 
grid alone.

All the simulations shown have realistic mass ratio, domains of the 
order of tens of ion skin depths and higher resolution of the order of 
fractions of the electron skin depth.

Co-authors:
Stefano Markidis (KTH Royal Institute of Technology, Stockholm, Sweden)
Giovanni Lapenta (University of Leuven, Leuven, Belgium)

http://www.pa.ucla.edu/sites/default/files/plasma_Innocenti120315.pdf