Seminars Autumn/Michaelmas Term of 2024

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. "Plasma group meetings (or journal clubs)" 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 meetings are organised by Michael Barnes 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; TT & Summer 2017; Autumn/MT 2017; HT 2018; TT & Summer 2018; MT 2018; HT 2019; TT & Summer 2019; MT 2019; HT 2020; TT & Summer 2020; MT 2020; HT 2021; TT & Summer 2021; Autumn/MT 2021; HT 2021; TT & Summer 2022; Autumn/MT 2022; HT 2023; TT & Summer 2023; Autumn/MT 2023; HT 2024; TT & Summer 2024;

Autumn/Michaelmas Term of 2024

The seminars/group meetings will be on Tuesday at 14:00 in the Simpkins Lee Room, Beecroft Building, except where indicated otherwise below, in red.
It will be possible to join these meetings (when they are held in SL Room) on ZOOM --- details available from Alex on request.
Those who join these meetings on ZOOM are asked keep their video cameras on.
The ZOOM system in Simpkins Lee Room does not display a list of participants whose cameras are off. It is not germane to these informal meetings to have invisible listeners of whom those present in the room are unaware, so if you are unable or unwilling to turn on your camera, you cannot join the meeting.
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
He goeth furthest who knows not whither he is going. Oliver Cromwell

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
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
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! Alex Schekochihin
It's not the triviality, it's the emptiness of it that bothers me. Bryan Taylor
Never take 0 for an answer. Alex Schekochihin
This is a very inefficient way of achieving nothing. Francois Rincon
For the sake of fairness, let me mention that some people have objections to this, none of which are particularly valid. Chris Chen
This is more or less right. Perhaps less. Alfred Mallet
Too simple? At the end of my talk, you will beg for simplicity! Andrey Beresnyak
What is the point? The point is not the point! Anonymous
This is why I am presenting this here and nowhere else: nothing is solved! Ian Abel
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 & 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
This is not rigour, unless you mean rigor mortis. Ian Abel

I wouldn't say these are theoretical arguments... Let's just call them arguments. Francois Rincon

This qualitative explanation is not of sufficient quality. Eugene Churazov

If you mean it seriously, this is actually a very good question. Minhyong Kim

This paper is a tour de farce. Ian Abel

It is better to be vaguely right than exactly wrong. Carveth Read (usually attributed to Maynard Keynes)

What is modelling? You run a simulation, you compare. If it coincides, great! If it doesn't coincide, fuck! Felix Parra
I have seen papers where the student wasn't the problem. Michael Hardman
There has been a lot of fascinating work on this subject, most of it kind of boring. Philipp Kempski
So now you want us to drop everything we are doing and start worrying about what the big questions are?! Ian Abel
Oh dear, I thought I had some conclusions. Nuno Loureiro
I've got my little fingers inside this plasma. Steve Cowley
Words will play a big role in this talk. Dmitri Uzdensky
Everything that can be done should be done---and that's the astrophysical attitude. Michael Medvedev
What I will talk about is not low-hanging fruit. A lot of people have looked at this. There is no fruit here at all.---What about sour grapes? Michael Medvedev & Nuno Loureiro
In order to have a disappointment, you first have to have an appointment. Alex Schekochihin
In our experiment, we observed strong absence of magnetic energy. Archie Bott
Much as I somewhat hate this approach... Peter Davidson
Your infinity is my zero. Mantas Abazorius
If I had known the outcome of this calculation, I would never have done it. Michael Hardman

Now that everyone knows this is the new Pandora's box, they are all going to jump into it. Francois Rincon
We must think outside the axisymmetric box. Georgia Acton

This is not real, it's a Platonic absolute.---The real thing is more Platonic and more absolute. Alex Schekochihin & Anthony Field
All I've done here is sacrificed equality in favour of inequality. Per Helander
Generally, it depends. Steve Majeski
This numerical scheme works fine, but it is physically disgusting. Bruno Despres
This research is not only not finished, it has not really been started. Anatoly Spitkovsky
This is what really matters... given that "really matters" is a strong word in this context. Robbie Ewart
This was discovered accidentally, but it was an informed accident. Plamen Ivanov
Infinity is a long way away. Rafael Bailo
To solve the kinetic equation on a mesh, you really need to know what you are doing.
That's why, historically, people haven't. Rafael Bailo
Just shout if you want to chat. Robbie Ewart
They ran this simulation for a long time but not forever. Patrick Reichherzer

[these quotes are mostly from these seminars and the Vienna meetings]

Wk	Date	Time & place	Speaker & Topic	Background reading	Visitors in town
	Tue 3 Sept	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Group Meeting (organised by MICHAEL BARNES) Open mic		Yohei Kawazura (Utsunomiya U)
	Tue 10 Sept	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Group Meeting (organised by ALEX) Juan Ruiz Ruiz & Yujia Zhang will report on the 2024 Varenna-Lausanne Workshop	R. Nies's new paper
	Tue 17 Sept	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Journal Club (organised by ALEX) 1) Leo Turica will discuss Montani & Moretti "Symmetries of the electromagnetic turbulence in a tokamak edge" 2) Michael Nastac will discuss Lobo & Sayal "Theory of phase-space hydrodynamics of electron and ion holes in collisionless plasmas" 3) Robbie Ewart & Prakriti Palchoudhury will discuss Squire et al. "Rapid, strongly magnetized accretion in the zero-net-vertical-flux shearing box" 4) Prakriti Palchoudhury will discuss Johnston et al. "A unified phenomenology of ion heating in low-beta plasmas: test-particle simulations"	arXiv:2407.01241 PoP 31, 092301 (2024) arXiv:2409.05467 arXiv:2409.07015
	Surui Li leaves the group to return to Cambridge.
	Tue 24 Sept	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Seminar (organised by MICHAEL NASTAC) Lynn Wilson (NASA) --- Nonequilibrium electron velocity distribution functions in the solar wind The solar wind is a supersonic flow of ionised particles, called a plasma, streaming away from the Sun. These particles are not observed to be in thermal or thermodynamic equilibrium. This is because nearly all particle dynamics are governed by non-collisional processes and the particles experience long-range forces (i.e., Coulomb potentials of nearby, charged particles). There are multiple particle species in the solar wind as well, including, but not limited to, electrons, protons, alpha particles, and multiple charge states of heavier ions up past uranium. For the particle species that we can resolve and properly measure, we observe non-Maxwellian features in the velocity distribution functions (VDFs). In fact, no species that is properly resolved is ever observed to be a single, isotropic Maxwellian or even a bi-Maxwellian distribution. That is, all VDFs are observed to have nonthermal tails and/or multiple phase-space density peaks and/or self-similar profiles. We will focus on the electron VDFs and their nonequilibrium features with a special emphasis on the often observed self-similar VDFs, also known as flattop distributions. These are especially interesting because they may be direct evidence of phase-space compressibility and/or inelastic collisional processes, both time-irreversible phenomena. Such nonequilibrium kinetic processes are of fundamental importance in physics and at the heart of some of the biggest outstanding questions in kinetic theory.	ApJS 236, 41 (2018) +erratum ApJS 269, 62 (2023) ApJS 243, 8 (2019) ApJS 245, 24 (2019) ApJ 893, 22 (2020) Front. Astron. Space Sci. 9. 1063841 (2022) +references therein slides are here	Lynn Wilson (NASA)
	Plamen Ivanov leaves Oxford and moves to EPFL. James Edmiston moves to Oxford from Cambridge as DPhil student to work with Dmitri Uzdensky, Michael Fitzgerald & Alex Schekochihin.				Lynn Wilson (NASA)
	Mon 30 Sept	15:45 SL Room & ZOOM (ask Alex for link)	Plasma Seminar (organised by ALEX) Pavel Kovtun (U Victoria) --- Dissipation and causality in relativistic MHD	JCAP 10(2022)039 JHEP 10(2019)034 JHEP 05(2017)001 PRD 95, 096003 (2016)	Tunde Fulop (Chalmers) Pavel Kovtun (U Victoria)
	Tue 1 Oct	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Seminar (organised by ALEX) Tunde Fulop (Chalmers) --- Running away and radiating	CPC 268, 108098 (2021) NF 64, 086033 (2024) (+references therein)
	Wed 2 Oct	11:00 SL Room & ZOOM (ask Alex for link)	Plasma Seminar (organised by ALEX) Pavel Kovtun (U Victoria) --- Effective field theory for hydrodynamic fluctuations	JHEP 02(2021)200 PRL 128, 071601 (2022) arXiv:1805.09331 J. Phys. A 45, 473001 (2012)
	Riju Dutta moves to Oxford from IISc (Bangalore) as DPhil student to work with Dan Kennedy & Alex Schekochihin. Agi Wierzchucka returns to Oxford as DPhil student to work with Dmitri Uzdensky and Alex Schekochihin. Robin Greif's postdoc stint at Oxford comes to an end.
0	Tue 8 Oct	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Group Meeting (organised by PATRICK & TUNDE) We will watch the colloquium organised by the Nobel Committee following the announcement of the 2024 Nobel Prize in Physics		Tunde Fulop (Chalmers)
I	Tue 15 Oct	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Group Meeting (organised by MICHAEL BARNES) Juan Ruiz Ruiz, Robin Greif, Robbie Ewart, and Michael Nastac will report on the APS DPP Meeting		Tunde Fulop (Chalmers)
II	Tue 22 Oct	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Group Meeting (organised by ALEX) Christopher Everett (Oxford Astro) --- 1) Kinetic modelling of astrophysical jets via a discrete momentum method; 2) Spacecraft propulsion a la magnetic reconnection	1) RAS Tech. Instr., rzae036 2) AIAA 2023-0448	Tunde Fulop (Chalmers) Dominika Maslarova (Chalmers)
III	Tue 29 Oct	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Group Meeting (organised by ALEX) 1) Barry Ginat --- Cosmological turbulence ...followed by Plasma Journal Club 2) Barry Ginat will discuss Imbrogno et al. "Long-living equilibria in kinetic astrophysical plasma turbulence"	1) preprint from author on request 2) arXiv:2408.02656	Peter Catto (MIT) Tunde Fulop, Ida Ekmark (Chalmers)
III	Robbie Ewart leaves Oxford to take up a postdoctoral fellowship with SCEECS at Princeton and Maryland.				Peter Catto (MIT) Tunde Fulop, Ida Ekmark (Chalmers)
IV	Tue 5 Nov	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Seminar (organised by TUNDE) Ida Ekmark (Chalmers) --- Fluid and kinetic modeling of runaway electron seed generation during disruptions Highly energetic runaway electron (RE) beams can be generated during tokamak disruptions, and since the RE generation is exponentially sensitive to initial plasma current, these beams pose a critical challenge for future tokamaks. Accurate simulations of tokamak disruptions are therefore essential for the development of successful mitigation strategies and safe operation. However, when simulating such disruptions, fluid plasma models are often preferred due to their low numerical cost, even though they generally are less accurate than kinetic models. We have compared simulations using both fluid and kinetic modeling of the RE seed generation for a diverse set of disruption cases in ITER and SPARC.	JPP 90, 905900306 (2024)	Tunde Fulop, Ida Ekmark (Chalmers) Per Helander (IPP Greifswald)
V	Mon 11 Nov	12:30 SL Room & ZOOM (ask Alex for link)	Plasma Seminar (organised by DMITRI) Nicolas Brughmans (KU Leuven) --- Non-axisymmetric accretion disk instabilities: new possibilities beyond the MRI Accretion disks are assumed to be turbulent as they are highly unstable to magnetic instabilities driven by shear flow, with the celebrated axisymmetric MRI accepted as basic mechanism. I will start by introducing MHD spectroscopy, which is a general framework to study the collection of (un)stable Fourier eigenmodes of MHD systems. These tools are required for a global treatment of non-axisymmetric instabilities, where nearby singularities from the overlapping MHD continua interact. I will then show how a new type of ultra-localised, non-axisymmetric instability in thin disks [1] is obtained. This Super-Alfvenic Rotational Instability (SARI) leads to unprecedented continuous 2D regions in the complex eigenfrequency plane, with eigenmodes corotating with the super-Alfvenic flow and shielded from the artificial boundaries by Alfven resonances. Finally, I will show recent work of mine that highlights how non-axisymmetric modes extend regimes accessible to instability, with growth comparable to the MRI [2], and how visualising the global MRI/SARI mode structure in time gives more insight into their nature. The Legolas code can be used in that regard to study spectra for a variety of (non-)ideal MHD equilibria.	1) ApJS 259, 65 (2022) 2) ApJ 968, 19 (2024)	Nicolas Brughmans (KU Leuven) Tunde Fulop (Chalmers) Per Helander (IPP Greifswald)
V	Tue 12 Nov	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Seminar (organised by ALEX) William Morris (UKAEA) --- Fusion plants and (some of) what they need	slides from JPP colloquium PPCF 64, 064002 (2022)
VI	Tue 19 Nov	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Group Meeting (organised by MICHAEL BARNES) Megan Evans --- Turbulence in a 2D large-aspect-ratio tokamak model with magnetic and flow shear [DPhil transfer presentation]	report from author on request	Tunde Fulop (Chalmers) Chris Hamilton (IAS Princeton) Per Helander (IPP Greifswald)
VII	Tue 26 Nov	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Group Meeting (organised by MICHAEL BARNES) Lucas McConnell --- Importance of kinetic effects in the scrape-off-layer using the Moment Kinetics Code [DPhil transfer presentation]	report from author on request	Tunde Fulop (Chalmers) Chris Hamilton (IAS Princeton) J.-B. Fouvry, Sofia Flores, Anwar El Rhirhayi (IAP)
VIII	Tue 3 Dec	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Seminar (organised by TUNDE) Louis Richard (Uppsala) --- Ion and electron heating in symmetric magnetic reconnection jets Magnetic reconnection is a ubiquitous plasma process powering some of the most extreme energy sources in the visible Universe. The reconfiguration of the magnetic field topology results in converting electromagnetic energy into bulk flows and accelerating charged particles. The reconnection outflow, in particular, plays a crucial role in plasma heating associated with magnetic reconnection. Using the Earth's magnetotail as a laboratory, we study how the reconnection outflow deposits its energy into the surrounding plasma. We present a comprehensive analysis of the magnetic reconnection outflows and the associated energy conversion mechanisms using NASA's Magnetospheric Multiscale spacecraft. Our study reveals that the reconnection outflow dissipates its energy through the generation of turbulence [1]. This turbulent energy transfer substantially contributes to the magnetic reconnection energy budget. We show that the non-adiabatic ion motion in the strongly curved magnetic fields associated with the reconnection outflow results in fast scattering and heating of thermal ions [2]. In contrast, ions with higher energies get accelerated by the convective electric field on the scale of the reconnection outflow [3]. Furthermore, our analysis also reveals that electrons are efficiently heated by a magnetic field-aligned electric field, which develops to maintain macroscopic quasi-neutrality [4]. This study illuminates the intricate interplay of various physical processes within the reconnection outflow, advancing our understanding of energy dissipation and particle energization associated with magnetic reconnection.	1) PRL 132, 105201 (2024) 2) PRL 131, 115201 (2023) 3) JGR 127, e2022JA030430 (2022) 4) preprint from author on request	Tunde Fulop (Chalmers) Chris Hamilton (IAS Princeton) Anwar El Rhirhayi (IAP) Louis Richard (Uppsala)
9	Tue 10 Dec	14:00 SL Room & ZOOM (ask Alex for link)	Plasma Group Meeting (organised by DAN KENNEDY) Harry Dudding (UKAEA) --- Applying the method of multiple scales to the Maxwell-Vlasov system Plasma physics models often rely on a priori assumptions about the relative importance of terms in governing equations. While these assumptions simplify analysis, they can also restrict the model's validity. This talk presents an application of the method of multiple scales (MMS) [1] to the Maxwell-Vlasov system, constructing a uniformly valid hierarchy of equations for plasma dynamics. Unlike conventional approaches, the MMS framework avoids fixed assumptions about the expansion parameter's relationship to physical parameters, introducing independent fast- and slow-scale coordinates in space and time. The additional degrees of freedom introduced by the new coordinates enable the systematic elimination of secular terms, yielding an explicit Reynolds-like turbulence average. The resulting equations encompass established regimes such as kinetic MHD and gyrokinetics. Key insights include a strongly magnetised electromagnetic analogue of Landau damping, and novel terms in gyrokinetic-like equations that account for kinetic MHD effects and Langmuir waves. Implications for global gyrokinetic models and their predictive capabilities are also explored.	1) MMS tutorial	Tunde Fulop (Chalmers)
10	Tue 17 Dec	No seminar. Beecroft Building closed for power testing.			Robbie Ewart (Princeton) Tunde Fulop (Chalmers)
	Tue 24 Dec	No seminar. Merry Xmas!
	Tue 31 Dec	No seminar. Happy NY!

Hilary Term of 2025