1,480 reputation
715
bio website
location London, United Kingdom
age
visits member for 4 years
seen yesterday

My background is in theoretical/mathematical physics [MPhys/PhD], I was a Senior Computational Fluid Dynamics Analyst in the nuclear/defence industry before selling my soul and becoming a full-time commercial software developer around 2011.


8h
awarded  Yearling
Jun
10
comment Crab pulsar radiation
The long and the short is that more can be observed and learnt by modelling the wind zone rather than the more illusive areas such as the magnetoshpere. I am not saying you can't model these areas (arxiv.org/abs/astro-ph/0402403) but many aspect of the models cannot be substantiated observationally.
Jun
10
comment Crab pulsar radiation
The dominance of pulsar modelling concerning relativistic outflow has become popular because we can detect the radiate emission from such flow and can directly compare observations with mathematical models - this is near impossible for regions inside the wind zone unless the pulsar is favorably aligned (poles directed at us). Relativistic MHD is a very well understood theory and using it we can model pulsars from there birth to their current state with astounding accuracy. From this we are able to establish the cause of a vast number of phenomena and infer details of the wind zone.
Jun
10
comment Crab pulsar radiation
The problem is that much of the physics concerning the zone down-stream of the termination shock is unknown. This is esp. true for the physical processes at work within magneto-sphere. We do not understand the intricate details of how particles are accelerated from within the magnetosphere into a KE dominated relativistic wind for example. Go beyond that, nearer to the pulsar, we know even less. "High-Energy Emission from Pulsars and their Systems: Proceedings of the First Session of the Sant Cugat Forum on Astrophysics" is a great review for all regions of study.
Jun
9
comment Crab pulsar radiation
I will try and track an article down for you.
Jun
8
comment Crab pulsar radiation
I would like to provide some calculations to back this - but I am too busy at this time. Perhaps over the weekend I will come back to this and try and provide at least an order of magnitude estimate.
Jun
8
comment Crab pulsar radiation
Any radiative energy produced inside the magnetosphere will be small compared to the energy carried off in the wind. How do I now this, well [without dusting off the pencil] if you look at the overall luminosity of the nebula coupled with it's expansion rate you can infer the energy required to inflate such a nebula (if you are happy with what I have said so far). This luminosity alone will be a vast proportion of the spin-down power of the star, hence we can say that the energy carried away in the ultrarelativistic wind dominates all other mechanisms of energy release...
Jun
8
comment Crab pulsar radiation
The spin-down power of the pulsar is spent in the generation of magnetic field in the wind zone. Outside of the rigid co-rotating plasma the wind is cold and highly collomated, in almost all models, the relativistic wind leaving the magnetosphere must be Poynting flux dominated. However, somewhere between the light cylinder and the termination shock the wind changes from Poynting flux dominated to particle flux dominated - this leads us to the termination shock where the radiation mechanisms kick in as the flow is decelerated and shock heated. As for your question...
Jun
8
comment Crab pulsar radiation
At the stellar surface, the pulsar’s huge magnetic fields and rapid rotation induce enormous electric fields within the magnetosphere, these consequently tear particles from the stellar surface and accelerate them to high energies. Plasma then fills the magnetosphere and the extreme magnetic field present is sufficient to cause the plasma to rigidly co-rotate. However, this co-rotation must cease somewhere near the light cylinder, and the particles flow along the opened magnetic field lines, carrying away energy in the form of an ultrarelativistic magnetized wind.
Jun
8
answered Crab pulsar radiation
Apr
8
comment Can universe or anything be simulated with absolute accuracy?
See here: physics.stackexchange.com/questions/63811/…
Jan
8
comment Easy formula for ultrarelativistic bremsstrahlung?
This is not taking into account magnetic field or the particles charge (both important factors), this formula does not look correct to me...
Jan
7
revised What is the relativistic calculation of travel time to Proxima Centauri?
deleted 12 characters in body
Nov
27
awarded  Necromancer
Sep
24
awarded  Autobiographer
Jul
9
comment Euler Equations, Sod shock tube & conservation
Note that the code used to display the animation is not very stable and there a lot of numerical instabilities in these simulations which are non-physical. Just something to be aware of...
Jul
7
awarded  Yearling
Jun
12
comment Deborah Number for harmonic excitation
In this case the characteristic time scale is merely the inverse of the frequency of harmonic excitation. The observational time scale is not a property that is 'applied' to the fluid, it is abstract.
Apr
10
revised Magnetic Pole Emission from Pulsars
deleted 4 characters in body
Mar
24
comment Many times speed of light
You ask a good question, one whose answer lies in the subtle difference between expansion that is faster than the speed of light and the propagation of information that is faster than the speed of light. The latter is forbidden by fundamental physical laws, but the former is allowed; that is, as long as you are not transmitting any information (like a light pulse), you can make something happen at a speed that is faster than that of light.