OXFORD PLASMA THEORY GROUP

PLASMA SEMINARS AND GROUP MEETINGS

The style of the seminars will be informal/chaotic/interactive, following the established tradition. The format of the presentations can be a tutorial on a topic of interest, a report on just completed/ongoing/just starting/potentially interesting research projects, a literature review, a lecture by a passing visitor or anything else worthwhile that anyone cares to suggest. The speakers will be interrupted freely and asked to defend themselves. For background reading, only the most relevant or the most recent references are posted; please follow the paper trail from there. The schedule is subject to change on short notice, but what you see posted here is always up to date; the seminars are also announced via the department's seminar server (group meetings are not). Please email Alex Schekochihin if you would like to receive email updates on these seminars. "Group meetings to discuss current affairs" will discuss current affairs (ongoing projects, new litearture etc.) as well as feature some presentations that are even more informal than seminars. They are open to all members of the Oxford Plasma Theory Group. While some expected contributions are pre-announced, everything is TBC and people wishing their work to be discussed can volunteer contributions without prior notice. Unlike for the seminars, there will not be full-spam-list email reminders of the group meetings. The seminars and group meeting are organised by Michael Barnes, Felix Parra and Alex Schekochihin, please contact them with any queries or if you wish to present something.

Past seminar database:
Autumn 2007; Winter-Spring 2008; Summer 2008; Autumn 2008; HT 2009; TT 2009; Summer 2009; MT 2009; HT 2009; TT 2010; Summer 2010; MT 2010; HT 2011; TT 2011; Summer 2011; MT 2011; HT 2012; TT 2012; Summer 2012; MT 2012; HT 2013; TT & Summer 2013; MT 2013; HT 2014; TT & Summer 2014; MT 2014; HT 2015; TT & Summer 2015; MT 2015; HT 2016; TT & Summer 2016; Autumn/MT 2016; HT 2017


 
Trinity Term and Summer of 2017

The seminars/group meetings will be on Thursday at 11:30 in 501 DWB, except where indicated otherwise below.
Note also the ALP Seminars (here is a list of all Physics seminars)

If you know exactly what you are going to do, what is the point of doing it? Pablo Picasso

Every line in your calculations ends with "=0". You are not making much progress!
Kate Hammett
We don't do the calculation because we don't know the answer, we do it because we have a conscience. Bryan Taylor
Let's change the resolution on the Unknown. Gabe Plunk
Let me put it differently: suppose we had a reactor... Per Helander
Working together takes more than one person. Bill Dorland
We can't do ultraviolence to that square bracket. Ian Abel
Field lines are forever. Bryan Taylor
This is not really an ill-posed problem, this is not a problem at all. Paul Dellar
I am just doing mathematics at the moment, but it is mathematics that has some point. Bryan Taylor
The equivalent of God in MAST is MHD, which is global and all powerful. Anthony Field
I've got a fishbone coming up. Tim Horbury
We have crossed all the i's and dotted all the t's. Job's a good'un. Ian Abel
Let us not jump in front of the bandwagon! Anonymous
It's not the triviality, it's the emptiness of it that bothers me. Bryan Taylor
This is a very inefficient way of achieving nothing. François Rincon
It is better to be roughly right than precisely wrong. Maynard Keynes
 

We Hankel all the way in and then Hankel all the way out. Joseph Parker
For the sake of fairness, let me mention that some people have objections to this, none of which are particularly valid. Chris Chen
Yes, Steve, you have always known what we have only just figured out. Alfred Mallet
This is more or less right. Perhaps less. Alfred Mallet
You go ahead with your argument. I'll think. Steve Cowley
Too simple? At the end of my talk, you will beg for simplicity! Andrey Beresnyak
The point is not the point! Anonymous
This is why I am presenting this here and nowhere else: nothing is solved! Ian Abel
This calculation is not intellectual masturbation: there's no orgasm. Anonymous
There are many big Buts here... I like big Buts. Anonymous
Previous studies of this problem have been either unsatisfactory or limited in scope.---What  is the difference between these?---This means either wrong or irrelevant.
Anatoly Spitkovsky, Michael Medvedev and Steve Cowley (in conversation)
I don't give a damn about astrophysics, explain to me what is going on. Anatoly Spitkovsky
Have you subtracted the baby with the bathwater? Steve Balbus
EDQNM is not rigour, unless you mean rigor mortis. Ian Abel
[these quotes are from Oxford plasma seminars and Vienna meetings]

Wk Date
Time
& place
Speaker & Topic
Background reading
Comings and goings
(incl. visitors in town)
0
Thu
Apr 20
11:30
501
DWB
Plasma Group Meeting (organised by ALEX)
Spring resolutions
Everything is out now:
Ball: arXiv:1703.03375
PPCF 59, 024007 (2017)
Bott: arXiv:1702.03016
Colyer: PPCF 59, 055002 (2017)
Geraldini: PPCF 59, 025015 (2017)
Fox: PPCF 59, 034002 (2017)
PPCF 59, 044008 (2017)
Mallet: arXiv:1612.07604
MNRAS 466, 3918 (2017)
van Wyk: arXiv:1704.02830
JPP 82, 905820609 (2016)
...

I
Thu
Apr 27
11:30
501
DWB
Plasma Group Meeting (organised by FELIX)
Valerian Chen --- Beam tracing

Hye-Sook Park
(LLNL)
Fri
Apr 28
14:00
A. Wood
Room
ALP Seminar (organised by GIANLUCA)
Hye-Sook Park (LLNL) --- Frontiers in high-energy density physics at the National Ignition Facility and other high-power laser facilities
PRL 114, 065502 (2015)
Nature Phys 11, 173 (2015)
II
Thu
May 4.
11:30
501
DWB
Plasma Group Meeting (organised by MICHAEL)
Free discussion

Swadesh Mahajan
(UT Austin)
1-12 May
Les Houches-2017 School om Plasma Physics
III
Thu
May 11
11:30
501
DWB
Plasma Seminar (organised by MICHAEL)
Swadesh Mahajan (UT Austin) --- Relativistic-amplitude electromagnetic waves: beating the “magnetic” barrier
The "dispersion'' characteristics of an arbitrary-amplitude circularly polarized electromagnetic wave, propagating in a highly (thermally and kinematically) relativistic plasma, are shown to approach those of a linear wave in an unmagnetized, non-relativistic plasma. Further aided by high relativistic temperatures, the cut-off frequency tends to become anomalously small; waves with frequencies well below the nominal plasma and the cyclotron frequencies find the plasma to be essentially transparent. This spectacular relativistic phenomenon will greatly advance our ability to understand and model the dynamics of a large class of astrophysical and laser-produced high electromagnetic-energy density systems. It is speculated that the enormous reduction in the effective cyclotron  frequency may be a fundamental mechanism for facilitating waves - at the lower end of the electromagnetic spectrum - to escape from highly magnetized plasma like that of a pulsar magnetosphere.
JPP 83, 905830101 (2017)

Swadesh Mahajan
(UT Austin)
IV
Thu
May 18
11:30
501
DWB
Plasma Seminar (organised by ALEX)
Jono Squire (Caltech) --- Compressible turbulence: overview + recent ideas on density statistics
arXiv:1702.07731
Swadesh Mahajan
(UT Austin)
Jono Squire
(Caltech)
V
Thu
May 25
No seminar
Swadesh Mahajan
(UT Austin)
Jono Squire
(Caltech)
24-26 May
1st JPP Frontiers in Plasma Physics Conference in Spineto
VI
Thu
June 1
11:30
501
DWB
Plasma Seminar (organised by FELIX)
Jesus Ramos (MIT) --- Stability criteria for Kinetic MHD
JPP 82, 905820607 (2016)
JPP 81, 905810325 (2015)
JPP 81, 905810111 (2015)
Jesus Ramos
(MIT)

Adwiteey Mauriya
rejoins the group

VII
Thu
June 8
11:30
501
DWB
Plasma Group Meeting (organised by MICHAEL)
Filomena Nave --- JET intrinsic rotation update


VIII
Thu
June 15
11:30
501
DWB
Plasma Group Meeting (organised by ALEX)
Michael Hardman --- ETG turbulence update


9
Thu
June 22
11:30
501
DWB
Plasma Group Meeting (organised by FELIX)
Valerian Chen --- Modelling the effect of the misalignment of the probe beam and the magnetic field in Doppler backscattering measurements of fusion plasmas
Magnetic confinement fusion is a promising candidate for carbon-free energy. Unlike renewables, fusion energy will be able to provide the base load power. However, it is still a work in progress. I will give a brief overview of some of the current challenges, and introduce the research being done at the Oxford Plasma Theory Group and the Culham Centre for Fusion Energy, which is home to two of the world's leading fusion experiments (JET and MAST). I will then present the recent results of our research on improving the Doppler Backscattering (DBS) microwave diagnostic. DBS enables the non-perturbative characterisation of density fluctuations and flows, both at the edge and the core of the plasma. However, the use of DBS in spherical tokamaks (like MAST) is complicated since the magnetic pitch angle is large (up to 35◦, compared to 15◦ in standard tokamaks like JET). Moreover the pitch angle varies both spatially and temporally. Consequently, the DBS probe beam and the magnetic field may not be normal to each other. This misalignment, which affects the backscattered signal, can be empirically optimised with 2D beam steering. Unfortunately, this significantly increases the amount of experiment time required, which is already in short supply. To get around this problem, we used the beam tracing code Torbeam to determine the beam width, curvature, and location of scattering. Using this information, we have developed a model to determine the backscattered power and its dependence on the mismatch angle, thereby accounting for the misalignment of DBS measurements. The results are compared to scans of the toroidal launch angle from MAST data. With insight from our model, we also assessed the measurement capabilities for the planned MAST-U DBS system.


10
Thu
June 29
11:30
501
DWB
Plasma Group Meeting (organised by MICHAEL)
Nicolas Christen --- Momentum transport and rotation for JET/ITER plasmas



3-5 July
D. Sciama
LT
DWB
Workshop on Plasma Astrophysics: From the Laboratory to the Non-Thermal Universe (in homour of Tony Bell and John Kirk)
(organised by Katherine Blundell)
Right here in Oxford: an opportunity to learn everything you ever wanted to know about plasma astrophysics but were afraid to ask Tony!
Roger Blandford
(Stanford)
Lorenzo Sironi
(Columbia)
Anatoly Spitkovsky
(Princeton)
Alessandro Zocco
(IPP Greifswald)

Joe Abbate (Princeton),
Ching Chong (Oxford) &
David Hosking (Oxford)
join as summer interns
with F. Parra and
A. Schekochihin, resp.
Thu
July 6
11:30
501
DWB
Plasma Group Meeting (organised by ALEX)
1) Valerian Chen and Adwiteey Mauriya to report on the EPS Plasma Meeting in Belfast
2) Alessandro Zocco (IPP Greifswald) --- Update on resonant destabilisation of ITGs in stellarators and tokamaks
2) preprint
on request

Thu
July 13
11:30
501
DWB
Plasma Seminar (organised by ALEX)
David Hatch (UT Austin) --- Flow shear suppression of pedestal turbulence
A combined analytic and computational gyrokinetic approach is developed to address the question of the scaling of pedestal turbulent transport with arbitrary levels of ExB shear. Due to strong gradients and shaping in the pedestal, the instabilities of interest are not curvature-driven like the core instabilities. By extensive numerical (gyrokinetic) simulations, it is demonstrated that pedestal modes respond to shear suppression very much like the predictions of a basic analytic decorrelation theory. The quantitative agreement between the two provides us with a new dependable, first principles (physics based) theoretical framework to predict the efficacy of shear suppression in burning plasmas that lie in a low-shear regime not accessed by present experiments.
Phys. Fluids B 4, 1385 (1992)
arXiv:1706.08406
Roger Blandford
(Stanford)
Daniel Dunai
(Wigner, Budapest)
David Hatch
(UT Austin)
Alessandro Zocco
(IPP Greifswald)
Fri
July 14
16:00
New
 Seminar
Rm, StJ
Workshop on hot QFT (organised by Andrei Starinets)
(16:00) Pavel Kovtun (Victoria) --- Relativistic magneto-hydrodynamics
I will discuss relativistic magneto-hydrodynamics, which is hydrodynamics coupled to dynamical electromagnetic fields. Until recently, there seemed to be no consensus in the literature on a) what does the relevant thermodynamics look like, and b) what is the number of transport coefficients. I will describe my take on the subject, through Maxwell's equations in matter in a covariant form. Simple examples include Alfven, magnetosonic, and other waves. For a parity-preserving fluid in 3+1 dimensions, there are seven dissipative and four non-dissipative transport coefficients at first order in derivatives.
(17:30) Saso Grozdanov (Leiden) --- Generalised global symmetries and dissipative magnetohydrodynamics: field theory and holography
I will discuss a new symmetry-based approach to dissipative relativistic magnetohydrodynamics (MHD), which allows for a formulation of MHD in plasmas with any equation of state and transport coefficients, in weakly- and strongly-interacting theories. After constructing MHD at ideal and dissipative levels, I will present new predictions for the behaviour of MHD waves (Alfven and magnetosonic waves) in dense plasmas with strong magnetic fields. Furthermore, I will claim that MHD may persist to be a good low-energy effective theory in the limit of zero temperature where it becomes non-dissipative with corrections controlled by second-order hydrodynamics. Finally, I will discuss a new construction of a holographic dual to MHD, from which relevant microscopic details (equations of state and seven transport coefficients) can be extracted to study MHD waves in a model of a strongly interacting plasma.
JHEP05(2017)001
PRD 95, 096003
(2017)


Thu
July 20
No seminar
Daniel Dunai
(Wigner, Budapest)

17-28 July
10th Plasma Kinetics Working Meeting in Vienna
Daniel Dunai
(Wigner, Budapest)

Thu
July 27.
11:30
501
DWB
Plasma Group Meeting (organised by FELIX)
Free discussion



Thu
Aug 3
11:30
501
DWB
Plasma Seminar (organised by MICHAEL)
Chris Bambic (Maryland) --- Observational and theoretical insights on AGN feedback: constraints on turbulent heating
ApJ 815, 41 (2015)
Bill Dorland,
Chris Bambic
(Maryland)

Thu
Aug 10
11:30
501
DWB
Plasma Group Meeting (organised by ALEX)
Discussion of summer interns' projects (Ching Chong and David Hosking)



Thu
Aug 17
11:30
501
DWB
Plasma Group Meeting (organised by FELIX)
Free discussion
Hermite
spectrum paper:
arXiv:1707.08180


Thu
Aug 24
11:30
501
DWB
Plasma Group Meeting (organised by MICHAEL)
TBA



Thu
Aug 31
11:30
501
DWB
Plasma Seminar (organised by ALEX)
Thomas Antonsen (Maryland) --- Reciprocity and adjoint methods applied to charged particle dynamics

Thomas Antonsen
(Maryland)

Adwiteey Mauriya
leaves the group


Autumn and Michaelmas Term of 2017