The Magneto-Hydro-Dynamics Muddle ** Under_Construction Jan-2019 **
*** This represents the personal, scientific perspective of C. Fred Driscoll ****
This Website will provide links to nascent plasma theory describing the
Electric Fields of The Sun and Solar Wind. Here, plasma particles and currents
are analyzed including gravito-electric and photo-electric effects,
which are inherently precluded in MHD.
The gravito-electric field arises in all gravitating plasmas due to the proton/electron mass disparity:
gravity causes concentration of protons, and electron thermal pressure causes (miniscule) charge separation
and a (significant) electric field.
The photo-electric field arises from outward photon drag on un-bound electrons, and becomes significant
in the outer Photosphere and Corona. Protons (accompanied by electrons) are accelerated to keV energies
in the low-collisionality plasma "sheath" of the Corona.
Here, further atomic- and plasma-physics analysis is needed to quantify the "opacity"
of the (weakly correlated) plasmas of the outer Photosphere and Corona.
This is described briefly in AGU_2018_Poster
This simple model of Solar electric fields is broadly precluded by the pervasive scientific
murkiness of "The MHD Muddle", which has descended from plasma physics onto astro-physics.
Thus, a second aspect of this Website is to characterize the scientific "Chimeras"
created within The MHD Muddle.
Closest to home is is the 60-year old "consensus-standard" Chimera of The Parker Magnetic Spiral (TPMS) :
a rotating, spiralized, dipolized-monopole magnetic field rooted in and emanating from the Sun.
This Chimera brutalizes so much of standard Electro-Magnetism that it can only exist
within the realm of Ideal MHD.
The Ideal MHD equations descend from the (broadly valid) Maxwell-Lorentz equations
for particles and fields, through a process of assumptions and approximations, originally called
The MHD equations have fewer variables and are much more "tractable" than the full equations,
so MHD "solutions" are obtained more easily. Unfortunately, little analysis is devoted to
physical processes which do not fit into the (putative) "MHD regime."
When an explanation for an observed process is "sorely needed", theorists tend
to be imaginative, so as to "engineer" an acceptable explanation.
Scientific rigor then requires that the MHD solution be checked to verify
that the assumptions and approximations are valid; but in practice, this is rarely done.
Scientific rigor is then further bypassed if the available experimental data is interpreted "loosely",
so as to provide "support" for the desired theory.
For the Parker Spiral Chimera, loose interpretation consists of conflating the purported
persistent magnetic spiral with the observed fluctuating magnetic fields.
The MHD Muddle regime offers fertile ground for "imagineering" supported by "boosterism",
since assumptions readily become givens, through use of "mantra phrases" such as
--"Stuck on field-lines"
--"Moving field lines"
--"Particle streamline is a field-line"
MHD mutilation of Maxwell's Equations
The "Geometric" Maxwell-Lorentz equations describe Electro-Magnetic fields and the (non-entropic) dynamics from EM forces acting on (classical) charged particles. The equations display a single fundamental parameter, e^2, which sets the energy (or size) scale. The equations are Lorentz-invariant, with discrete charge being fully conserved. Fluid equations are obtained by conceptually "infinitely partitioning" the particles, keeping e/m constant. This eliminates discrete charge and introduces non-invariant charge density, while conserving total charge, mass, and energy, and introducting entropic pressure. This process eliminates particle collisions and particle correlation energies, with collisional resistivity being re-instated in a "constitutive" Ohm's law.
Standard MHD Assumptions
then eliminate all charge, describing a charge-neutral, "conducting" massive fluid,
wherein mass and momentum are completely separate from the (disembodied) current,
which is required to have only transverse (spin) components.
This eliminates several important plasma characteristics:
-- No Electric Potential Energy
-- No E parallel to B
-- No Thermo-Electric Effect
-- No Gravo-Electric Effect
-- No Capacitive Effects
-- No Charge-density waves
-- Modified Inductance
Ideal MHD conveniently adds an "infinite conductivity" assumption,
giving permanence to magnetic field "lines" (which are otherwise dissipated),
leading to appealing psychological mantras, such as :
-- Moving B-lines
-- B-lines "Frozen-In" to moving plasma
-- Plasma "stuck on" B-lines
-- Moving B-lines are "particle streamlines"
Causality is Eliminated with an additional assumption :
-- the "Maxwell displacement current" is negligible (i.e. zero).
This makes the equations more "tractable" by eliminating the propagation of causal effects.
-- No Causality (time-retardation)
-- No Photons
In traditional MHD "imagineering", causality is reversed, and currents are caused only by the changes in pre-existing magnetic fields.
That is, cosmical MHD denigrates the
"curious popular notion that
the electric current causes the magnetic fields in the cosmos",
and "the even more curious notion that
the electric current is the more fundamental dynamical variable"
The Parker Magnetic Spiral is the "traditional" model
of the interplanetary magnetic field around our Sun.
Unfortunately, TPMS violates Maxwell's equations,
and is contradicted by extensive spacecraft measurements.
The measurements show fluctuating magnetic fields on many
temporal and spatial scales. Historically, satellite data analysts have been able to
find "support" for a persistent rotating dipolized-monopole spiral with
"ballerina-skirt sectors" from the magnitudes and directional probabilities of
measured near-zero-mean fluctuations.
For historians of science, TPMS is destined to be an exemplar of
"imagineering" supported by "boosterism".
For today's space scientists, one should ask :
Can NASA's "Parker Solar Probe"
... retire ...
"The Parker Magnetic Spiral" ?
Contact : cfd_MHDm (atsi) sdphi0 () ucsd () edu