| 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! 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. François Rincon 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 |
It is
better to be roughly right than precisely wrong. Maynard
Keynes 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. Matt Kunz 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 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. François Rincon You can never be too happy with the state of your closure. Amitava Bhattacharjee For this plot, 1 is 6.--- Weeell, not even. Steve Cowley and Steve Balbus Это качественное объяснение недостаточно качественное. 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 What is modelling? You run a simulation, you compare. If it coincides, great! If it doesn't coincide, fuck! Felix Parra We are stuck at x=0. Felix Parra I have seen papers where the student wasn't the problem. Michael Hardman |
| Wk | Date |
Time
& place |
Speaker & Topic |
Background reading |
Comings and goings (incl. visitors in town) |
| Thu Jan 3 |
No seminar (Happy New Year!) |
||||
| 0 |
Thu Jan 10 |
No seminar |
|||
| I |
Thu Jan 17 |
11:00 501 DWB |
Plasma
Seminar (organised
by FELIX) Albert Mollen (IPP Greifswald) --- Impurity transport in stellarator plasmas |
PPCF 60, 084001 (2018) PRL 118, 155002 (2017) |
Albert Mollen (IPP Greifswald) |
| II |
Thu Jan 24 |
11:00 501 DWB |
Plasma
Seminar (organised
by ALEX & ARCHIE) Jack Hare (Imperial) --- Magnetic reconnection, instabilities and turbulence in pulsed-power driven plasmas |
PRL 118, 085001 (2017) PoP 24, 102703 (2017) |
Jack Hare (Imperial) |
| III |
Thu Jan 31 |
11:00 501 DWB |
Plasma
Seminar (organised
by ALEX) Denis St-Onge (Princeton) --- Turbulent dynamo in a collisionless magnetized plasma The Universe is
magnetized. While magnetic-field strengths of just ~10^{-18} G are
required to achieve this both in our Galaxy and in clusters of
galaxies, observations of Faraday rotation, Zeeman splitting, and
synchrotron emission all make the case of ubiquitous ~μG fields. That
these systems are not content with hosting weaker fields is surprising,
at least until one realizes that the energy density of a ~μG field is
comparable to that of the observed turbulent motions. It is then
natural to attribute the amplification and sustenance of (at least the
random component of) the interstellar and intracluster magnetic fields
to the fluctuation (or “turbulent”) dynamo. In this talk, we will
explore the various ways in which plasma microphysics makes
magnetic-field amplification in weakly collisional plasmas by
macroscale turbulent motions possible, with application to the
intracluster medium of galaxy clusters.
|
ApJ 863, L25 (2018) |
Matt Kunz, Denis St-Onge (Princeton) |
| IV |
Thu Feb 7 |
11:00 501 DWB |
Plasma
Group Meeting (organised
by ALEX) Free discussion [if that fails, Alex Schekochihin --- Nonlinear MHD dynamo and reconnection revisited] |
||
| V |
Thu Feb 14 |
11:00 501 DWB |
Plasma
Group Meeting (organised
by ALEX) Catherine Felce (Merton) --- A toy 2D model for multi-scale electron and ion plasma turbulence This is based on a summer research project at Princeton with Greg Hammett and Noah Mandell. |
project report on request |
|
| VI |
Thu Feb 21 |
11:00 501 DWB |
Plasma
Seminar (organised
by ALEX) Archie Bott --- Investigating turbulent amplification of magnetic fields with laser-plasma experiments |
DPhil thesis from on author on request |
Roger Blandford (Stanford) |
| Fri Feb 22 |
14:00 D Sciama LT |
Theoretical Physics Colloquium: Roger Blandford (Stanford) --- Extreme astrophysics The electromagnetic
spectrum has been opened up from meter radio waves to 100 TeV photons
and augmented with 10 - 300 Hz gravitational wave, MeV - PeV neutrinos
and MeV - ZeV (160 Joule) cosmic ray messages. Consequently, there is a
high rate of discovery and understanding of phenomena whose explanation
invokes accepted physics - classical (including general relativity),
atomic, nuclear and particle (including QED) processes - in extreme
environments. The richness of the discovery space can be epitomized by
describing some new observations and ideas pertaining to relativistic
jets formed by massive spinning black holes, Ultra High Energy Cosmic
Rays accelerated by strong shock waves surrounding rich clusters of
galaxies and Fast Radio Bursts, generated by neutron stars with 100 GT
magnetic fields.
NOTE: Roger is also giving an Occam Lecture at Merton, "Confirmation, Conviction and Cosmology", on Monday 25 February. |
|||
| VII |
Thu Feb 28 |
11:00 501 DWB |
Plasma
Group Meeting (organised
by FELIX) Alessandro Geraldini (Maryland) --- Making stellarator surfaces great again |
Roger Blandford (Stanford) Alessandro Geraldini (Maryland) |
|
| Fri Mar 1 |
14:00 D Sciama LT |
Special Astro/Plasma
Seminar: Payel Das (Oxford) --- The nearby Universe: our window into gigayears of galaxy evolution |
|||
| VIII |
Thu Mar 7 |
11:00 501 DWB |
Plasma Seminar (organised
by MICHAEL & YOHEI) Makoto Sasaki (Kyushu U, Japan) --- Spatio-temporal dynamics of turbulence trapped in geodesic acoustic modes Prediction
of the spatial profile of tubulence is an important subject in studies
of magnetically confined plasmas. The spatial profile of turbulence is
determined not only by the local gradient of the density and
temperature, but also by the nonlocal processes such as the interaction
of the flow shear and the turbulence spreading. In this seminar, a
novel role of the sheared flow on the turbulence is presented. The
trapping of the turbulence by the flow is shown to be important for
determining their spatial propagation and profile, and this effect is
comparable to that by the turbulence spreading.
|
Sci. Rep. 7, 16767 (2017) PoP 25, 012316 (2018) |
Makoto Sasaki (Kyushu U, Japan) |
| 14:00 D Sciama LT |
Special Astro/Plasma
Seminar: Ralph Schoenrich (Oxford) ---Exploring the Milky Way with Gaia |
||||
| 9 |
Thu Mar 14 |
11:00 501 DWB |
Plasma
Seminar (organised
by MICHAEL & NICOLAS) Quentin Wargnier (Ecole Polytechnique) --- Mathematical modeling and high fidelity adaptive simulations of astrophysical plasmas with accurate transport: application to a partially ionized plasma under solar chromospheric conditions This contribution deals
with the fluid modeling of multicomponent magnetized plasmas in
thermo-chemical non-equilibrium from the partially- to fully-ionized
collisional regimes, aiming at simulating magnetic reconnection in Sun
chromosphere conditions. Such fluid models are required for large-scale
simulations by relying on high performance computing. The fluid model
is derived from a kinetic theory approach, yielding a rigorous
description of the dissipative and non-equilibrium effects and a
well-identified mathematical structure. We start from a general
system of equations that is obtained by means of a multiscale
Chapman-Enskog method, based on a non-dimensional analysis accounting
for the mass disparity between the electrons and heavy particles,
including the influence of the electromagnetic field and transport
properties. The latter are computed by using a spectral Galerkin method
based on a converged Laguerre-Sonine polynomial approximation. Then, in
the limit of small Debye length with respect to the characteristic
scale in the solar chromosphere, we derive a two-temperature
single-momentum multicomponent diffusion model coupled to Maxwell's
equations, which is able to describe fully- and partially-ionized
plasmas, valid for the whole range of solar chromosphere conditions.
The second contribution is the development and verification of an
accurate and robust numerical strategy based on a massively parallel
code with adaptive mesh refinement capability. We rely on the canop
code, based on two libraries: P4EST for the adaptive mesh refinement
(AMR) capability and MUTATION++ for computing the transport properties
with a high level of accuracy, in order to ensure that the full
spectrum of scales and the dynamics of the magnetic reconnection
process are captured. Finally, we present a 2D and 3D magnetic
reconnection configuration in solar chromospheric conditions and assess
the potential of the numerical strategy for simulating astrophysical
plasmas.
|
Marc
Massot, Quentin Wargnier (Ecole Polytechnique) Yohei Kawazura leaves the group to take up post at Tohoku U. (Japan) |
|
| 10 |
Thu Mar 21 |
11:00 501 DWB |
Plasma Journal Club (organised
by DAVID) Paper to be discussed: "Rotating MHD turbulence" by Bell and Nazarenko Some additional/background reading (suggested by Alex): MHD turbulence: review Rotating turbulence: a view; another view; experiment (and references therein) |
||
| Thu Mar 28 |
11:00 501 DWB |
Plasma Group Meeting (organised
by FELIX) Jason Parisi --- Toroidal and slab ETG dominance in JET pedestals |
preprint from author on request |
||
| 31 Mar - 5 Apr |
Univ |
International Conference on High-Energy-Density Science |
Henrik Latter (Cambridge) |
||
| Thu Apr 4 |
11:00 Dobson Rm AOPP |
Plasma Group Meeting (organised
by ALEX) Plamen Ivanov --- Update on zonal-flow-controlled saturation of ITG turbulence (new results) |
|||
| Thu Apr 11. |
11:00 501 DWB |
Plasma Group Meeting (organised
by MICHAEL) TBA |
|||
| 15-17 Apr |
Sherwood Meeting in Princeton |
||||
| Thu Apr 18. |
No seminar |
||||