Bohm diffusion - Factbites

Bohm diffusion - Factbites
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Topic: Bohm diffusion

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	David Bohm - Wikipedia, the free encyclopedia
		Bohm diffusion of a plasma in a magnetic field
		Bohm showed a deep concern for humankind and life in general, and was alarmed by what he considered an increasing imbalance of not only Man and nature, but among Peoples, as well as people, themselves.
		Bohm also made significant theoretical contributions to neuropsychology and the development of the holonomic model [1] of the functioning of the brain.
	en.wikipedia.org /wiki/David_Bohm

	ENHANCED DIFFUSION
		Abnormally fast diffusion of plasma particles across a magnetic field, not due to collisions; it is a collective phenomenon closely associated with plasma instabilities but its causes ar e not yet fully understood; Bohm diffusion and turbulent diffusion are examples of anomalus diffusion.
		Bohm diffusion and turbulent diffus ion are examples of anomalous diffusion.
		Diffusion of plasma particles across a magnetic field, faster than that corresponding to collisions.
	www.websters-online-dictionary.org /en/enhanced+diffusion.html

	DIFFUSION FACTS AND INFORMATION
		Diffusion is the movement of matter due to the movement of the individual molecules (or atoms).
		Diffusion is one kind of transport phenomenon: compare it, for example, to radiation.
		In each case, there is only a noticeable diffusion if there is a gradient: for example in thermal diffusion, if the temperature is constant, heat will move as quickly in one direction as in the other, producing no change.
	www.witwib.com /?s=diffusion

	Bohm diffusion - Wikipedia, the free encyclopedia
		Bohm diffusion is diffusion of plasma across a magnetic field with a diffusion coefficient equal to
		These eddies play a similar role to the gyro-orbits in classical diffusion, except that the physics of the turbulence can be such that the decorrelation time is approximately equal to the turn-over time, resulting in Bohm scaling.
		If the diffusion is collisional, then δ is the mean free path and τ is the inverse of the collision frequency.
	www.wikipedia.org /wiki/Bohm-diffusion

	David Bohm - Wikipedia
		Bohm war auch ein Zeitgenosse von Jiddu Krishnamurti und betreute in England die Krishnamurti-Schule Brockwood-Park mit.
		Bohm ist Begründer der bohmschen Mechanik, einer alternativen Beschreibung der Quantenmechanik.
		Bohm hat eine Reihe signifikanter Beiträge zur Physik geliefert, insbesondere im Bereich der Quantenmechanik und der Relativitätstheorie.
	de.wikipedia.org /wiki/David_Bohm

	Bohm Ford Nelson Prigogine Umezawa Quantum Theory and Bernoulli Schemes
		The diffusion processes of Nelson may be related to the diffusion calculations of fundmental physical constants, such as force strengths, in the theory under development by Michael Gibbs which in turn is related to the D4-D5-E6 physics model.
		(3) The diffusion constant VC is inversely proportional to the inertial mass of the particle, with the constant of proportionality being a universal constant hbar: VC = hbar / m.
		It is interesting that upon encountering this difficulty, David Bohm, the author of a similar theory (differing from Nelson's in that the equation of motion is deterministic), has embraced it, delighting in the principle that everything is connected to everything else."
	www.valdostamuseum.org /hamsmith/mwbn.html

	JustinFeng.com - Nuclear Fusion: An Introduction - Part 2
		Bohm diffusion does not depend on the density or conductivity of the plasma, as with classical diffusion, which means that an increase in temperature will lead to an increase in the rate of diffusion.
		Where D is the diffusion coefficient and the term ∂n/∂x is the rate at which the density n changes as you move across a gradient a distance x.
		The rate of particle diffusion is the particle flux, or the number of particles that pass through an area of one square meter per second.
	www.justinfeng.com /Fusion/Introduction2.htm

	Panpsychism and Pantheism: Plasma?
		Bohm discovered in high temperature gas, (plasma) that the electrons stripped from the atoms donÕt behave as individual particles but as part of a larger, organized whole.
		Bohm showed space is as real as the matter that moves through it.
		It was BohmÕs fist important discovery and this feeling of interconnectedness and wholeness runs through his life work.
	www.panpsychism.net /html/plasma.html

	Research (Günter Sigl)
		In these simulations we also found that the diffusion coefficient in the magnetic field structure considered here is about 10 times larger than often used analytical approximations such as the Bohm coefficient.
		Finally, the corresponding solid angle integrated spectra show negligible cosmic variance for diffuse sources and fit the data well both for the 0.05 and for 0.5 micro Gauss as shown on the left.
		The figure on the left shows the correlation between delay time t and energy E of arriving nucleons in a similar situation where the central field is 3 x 10**(-7) Gauss.
	astro.uchicago.edu /home/web/sigl/r2e.html

	Frequently Used Terms in Space Plasma Physics
		Diffusion process in which buildup of spatial charge creates electric fields which cause electrons and ions to leave the plasma at the same rate.
		Poleward of the diffuse aurora is the region of discrete auroral arcs produced by monoenergetic field-aligned particle beams which create a "bubbling" effect in the E-region at the end of the field lines along which they are traveling.
		Since the diffuse aurora mirrors the hot plasma sheet, it is also characterised by the same flow pattern, which is roughly zonally westward before midnight and zonally eastward after midnight.
	utd500.utdallas.edu /~kivanc/index_fut.html

	[84.02] Evidence of Bohm Diffusion in Historical Supernova Remnants
		The limits for some historical remnants are very close to the Bohm limit.
		We show that the cut-off frequencies and shock velocities can be used to set upper limits on the electron diffusion coefficient of the remnants.
		The values of the ``cut-off'' frequencies obtained by fitting the X-ray spectra with models of synchrotron emission have been used to estimate the ``maximum'' electron energies and magnetic field strengths of the remnants.
	www.aas.org /publications/baas/v36n5/aas205/1003.htm

	Proceedings of the Oklahoma Academy of Science
		Recently the author believes he has succeeded in deriving the Bohm diffusion coefficient by distorted free-path considerations (5), and the question has therefore arisen as to why the beam experiments should have yielded the results they do.
		Nevertheless the numerous and continuing references to anomalous losses and the offering of Bohm diffusion as an explanation have kept the concept alive.
		, the process of Bohm diffusion (as it was called) seemed disproved.
	digital.library.okstate.edu /oas/oas_htm_files/v58/p114_115.html

	Article - GCNEWS, Vol. 21, July 2005
		The impact of the energy-dependent diffusion on the resulting radiation spectra is demonstrated in Fig.
		Although the diffuse component can be extended to distances 100 pc and beyond, because of the enhanced product of the CR and gas densities in the central 10 pc region one should expect a bright γ-ray core within several arcminutes around Sgr A*.
		Diffuse TeV emission is also expected from interactions of cosmic rays with dense molecular clouds within the central 100 pc region.
	www.aoc.nrao.edu /~gcnews/gcnews/Recent/article.shtml

	Nonthermal Particle Acceleration and Radiation
		In the absence of 3D simulations that allow evaluation of the turbulence level and which also allow for cross field diffusion, DFA at the pair shock is not excluded as the means of creating nonthermal emission, although the constraints on the required diffusion rates clearly are rather demanding.
		Diffusive Fermi Acceleration (DFA) in transverse relativistic shocks is often invoked as the mechanism for such acceleration (see Gallant 2002 for a review).
		The pair shock may, of course, also be a nonthermal particle accelerator, as has been assumed in all MHD models for the excitation of the Crab, starting with Rees and Gunn (1974).
	astron.berkeley.edu /~anatoly/wisp/node8.html

	ITC13 Abstract 100 Last Page
		The upper limit corresponds to the absence of trapping and is the well-known Bohm diffusion coefficient.
		It determines the decrease of the diffusion coefficient and the modification of its scaling law in the parameters of the turbulence.
		It is already known that in the quasilinear case corresponding to K<1 the shape of the spectrum does not influence the asymptotic diffusion coefficient D. Only the average wave number appears in the expression of D. We show that at K>1 the shape of the spectrum has a strong influence on the diffusion coefficient.
	www.nifs.ac.jp /itc/itc13/abstract/abstract100.html

	Bohm Diffusion Details
		Since we need only 0.1--0.01 of the limiting Bohm diffusion rate, we have shown that it is not unreasonable to expect significant stochastic acceleration of these electrons during their lengthy residence in the trap.
		If we assume it picks up the 20 mV/m electric field in half a gyroradii and then scatters by 180$^\circ$\ (Bohm diffusion), then it will gain 1.2keV in each half gyroperiod, or 1 MeV in about 4 seconds, where the maximum energy limit is reached when the gyroradius is approximately the trap scale size.
		The plasma wave experiment finds 20--100 mV/m electric fields in the cusp.
	cspar181.uah.edu /RbS/GRL5/grl5a.html

	lowfreq_xport.html
		Being an empirical scaling law, Bohm diffusion is not a physical model in itself.
		Rossnagel and Kaufman claimed that data from their magnetron experiments agreed with the Bohm diffusion law for cross-field diffusion.
		For cases where plasma transport is dominated by diffusion, the particle confinement time,
	dusty.physics.uiowa.edu /~goree/papers/lowfreq_xport.html

	Astron. Astrophys. 354, 915-930 (2000)
		of the diffusion coefficient: since faster diffusion of more energetic particles tends to smooth out the gradients of the distribution function
		An essential part of the diffusive shock acceleration process is given by the adiabatic compression term in Eq.
		These terms describe the rate of diffusive and convective exchange of particles between the two zones.
	aa.springer.de /papers/0354003/2300915/sc3.htm

	UMSI 2001 Annual Report: Thomas W. Jones, Fellow
		By adopting this analytic solution, a numerical treatment of the plasma-physical injection model at a strong quasi-parallel shock was devised and incorporated into the combined gas dynamics and the CR diffusion-convection code.
		The basic theory of diffusive shock acceleration was considered, as well as some of the key issues that still prevent astronomers from a full understanding of its outcomes.
		One of the key questions to understanding the efficiency of diffusive shock acceleration of the cosmic rays (CRs) is the injection process from thermal particles.
	www.msi.umn.edu /general/Reports/ar2001/depts/IT/jones.html

	NERSC 2001 Annual Report: Science Highlights: Fusion Energy Sciences
		The diffusion is in a gyroBohm scaled regime.
		Cases closer to threshold with more rotational velocity shear show Bohm, scaled diffusion.
	www.nersc.gov /news/annual_reports/annrep01/sh_FES_08.html

	stability in plasmas
		In particular, the universal drift-dissipative instability was founded (together with R.Z.Sagdeev) which may exists both in the fully ionized plasma and partially ionized one (like the ionospheric plasma) and results to the very dangerous (for a plasma confinement in magnetic mirrors, for example, in tokamaks) turbulent Bohm diffusion.
	www.iki.rssi.ru /mss04/s1.htm

	The problem of stability
		Moiseev S.S., Sagdeev R.Z. On the Bohm diffusion coefficient.
		Zaslavsky G.M., Moiseev S.S., Oraevsky V.N. On the turbulent diffusion in weakly ionized magnetized plasmas.
	www.iki.rssi.ru /mss04/l1.htm

	Magnetized Target Fusion
		For the larger Bohm requirement of 10 MJ, the required liner kinetic energy would be tens of MJs, a few times the final plasma energy.
		One striking difference between the MFE and MTF regimes of density is that Bohm is an acceptable possibility at MTF density, while as shown in Fig.
		Heat conduction is the diffusion of cold particles up the gradient and hot particles down the gradient with no net flux of particles.
	fusionenergy.lanl.gov /Documents/MTF/Why_MTF/Why-MTF-Comments.html

	tsurutani_ab105.html
		We show an example where the diffusion rate of 1 MeV protons is 0.1 times the Bohm diffusion rate.
		We develop analytic expressions for the amount of displacement per interaction and use Monte Carlo type calculations to determine diffusion rates as a function of particle energy.
		Charged particle interactions with the MDs lead to particle guiding center displacements and particle cross-field diffusion.
	www.srl.caltech.edu /ACE/ACE2000/abstracts/interplanetary/tsurutani_ab105.html

	bohm diffusion - OneLook Dictionary Search
		Tip: Click on the first link on a line below to go directly to a page where "bohm diffusion" is defined.
		Bohm Diffusion : Eric Weisstein's World of Physics [home, info]
		We found 2 dictionaries with English definitions that include the word bohm diffusion:
	public.onelook.com /?w=bohm+diffusion

	Monday morning, 6 November 1995, 09:30
		The Bohm diffusion model leads to pessimistic heat flux thicknesses of 1.5-3cm, and maximum heat fluxes of \leq 6 MW/m^2 on the divertor plates.
		Plasma outboard SOL thickness, and divertor and limiter heat fluxes in the NSTX, are estimated using Bohm diffusion and marginal MHD stability models, for heating powers of up to 11MW.
		Carbon- fiber composite tiles of 4cm thickness are therefore needed to limit surface temperatures to \leq 1000 ^\circ\mboxC for full power heating pulses lasting 5 sec.
	flux.aps.org /meetings/BAPSDPP95/abs/S1Q14.html

	JT-60U MONTHLY SUMMARY
		The ion thermal diffusivity, chi-i, shows a gyro-Bohm like diffusion different from the Bohm like diffusion of chi-i previously obtained for L-mode plasmas in JT-60U.
		Preliminary results from the two cases with Ip/Bt = 0.86 MA/1.86 T and 1.5 MA/3.08 T show that the thermal energy confinement time, tau-Eth, has the strong rho* dependence, which is almost like gyro-Bohm type scaling.
		Major results from high triangularity, shear reversal and high-bp experiments conducted in this March and April run-period were assessed to showed remarkable progress in performance at high current regions.
	www-jt60.naka.jaeri.go.jp /english/html/May96.html

	Research
		Furthermore, Osaka University tried to include unclear anomalous electron diffusions by changing a Bohm diffusion coefficient at each high magnetic field strength in order to fit a calculated performance to the measured one.
		The model includes first ionization by direct electron-neutral collisions, electron-neutral elastic collisions, Bohm diffusion (anomalous diffusion); channel wall losses of ion flux and electron energy flux with secondary electron emission effect.
		The influences of magnetic field strength and acceleration channel length were mainly examined.
	yoshikawa.me.es.osaka-u.ac.jp /en/research.html

	Study of the plasma pre-sheath in magnetron discharges dominated by Bohm diffusion of electrons
		The cross-field transport of electrons is assumed to be dominated by Bohm diffusion (and mobility) in the mutually perpendicular electric and magnetic fields, while ions created by electron impact ionization fall directly to the cathode.
		Using an electron energy balance equation and treating the sheath as a source of electron heat flux, the plasma parameter profiles are solved in the pre-sheath, above the sputter trench.
		Solutions show a fall in electron temperature with distance from the sheath-edge, with plasma densities rising by a factor of typically three or four from sheath-edge to plasma.
	stacks.iop.org /0963-0252/7/572

	transport - definition from Biology-Online.org
		See: classical transport, neoclassical transport, anomalous tranport, diffusion, ambipolar diffusion, Bohm diffusion, classical diffusion, neoclassical diffusion, anomalous diffusion, energy transport, ripple transport.
		Energy losses from a plasma due to transport processes are a central problem in fusion energy research.
	www.biology-online.org /dictionary/transport

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