[Baps] Invitation to Eugene Parker's Seminar at Boston University, Monday, April 14th, 4-5PM

[Paul Withers]

Good morning,

This may be of interest to planetary scientists whose interests touch 
plasmas or physics.

Paul

-------- Original Message --------
Subject: [Csp] Invitation to Eugene Parker's Seminar at Boston 
University, Monday, April 14th, 4-5PM
Date: Tue, 08 Apr 2008 10:22:31 -0400
From: Harlan E. Spence <spence at bu.edu>
To: announce at bu-ast.bu.edu, csp at bu-ast.bu.edu, cism-bu at bu-ast.bu.edu, 
BUAS <buas at bu-ast.bu.edu>, undergrads at bu-ast.bu.edu,	nessc at bu-ast.bu.edu

Dear Colleagues,

      Please join us on Monday April 14th for a joint Center for Space
Physics (CSP) - Institute for Astrophysical Research (IAR) seminar to be
given by Professor Eugene N. Parker.  Dr. Parker is a noted space
physicist, astrophysicist, plasma physicist, and theoretical physicist.
His theoretical description of stellar winds 50 years ago was
foundational to space physics and astrophysics; his latest work
continues to challenge how we should think about the fundamental physics
of plasmas in the cosmos.

     Over his impressive career Gene Parker earned membership into the
National Academy of Sciences, was awarded the National Medal of Science,
and was honored with top prizes and medals from the American Geophysical
Union, the American Astronomical Society, and the American Physical
Society.   He is currently the S. Chandrasekhar Distinguished Service
Professor Emeritus, in the Depts. of Physics and Astronomy &
Astrophysics, the Enrico Fermi Institute, and the College at the
University of Chicago.

     Details of his talk are provided below and in the attached flier.
For those accustomed to our IAR and CSP seminar series, please note that
this seminar is on Monday afternoon and in the Photonics building.

     Please join us for Dr. Parker's provocative exposition on the "j,E
versus v,B" paradigm in astrophysical plasmas!

Best regards,
- Harlan Spence


*******************************************************************

Speaker:  PROFESSOR EUGENE N. PARKER, University of Chicago

Title:    HYDRODYNAMICS, MAGNETOHYDRODYNAMICS, AND ASTROPHYSICAL PLASMAS
            AND FIELDS

Date:     Monday, April 14th

Time:     3:30PM - Tea, Coffee and Cookies
            4:00PM - Seminar

Location: Photonics Building, Room 206
            Boston University
            8 St. Mary's St.
            Boston, MA

Map:      http://tinyurl.com/3o4smf


Abstract:
--------
It is commonly stated that hydrodynamics does not apply to collisionless
gases or plasmas, and magnetohydrodynamics does not apply to either
collisonless plasmas or partially ionized gases. Attention is directed
instead to the electric currents associated with the magnetic fields,
arguing that electric current, rather than magnetic field, is the
fundamental physical variable.  This view leads to the j,E paradigm for
the dynamics of astrophysical plasmas.  Unfortunately the equations of
Newton and Maxwell become intractable in the j,E paradigm, so workers of
that persuasion have turned to fantasies such as the electric circuit
analog to solve their problems.

In fact it is easy to show, using nothing more complicated than Gauss'
theorem, that the conservation of particles, momentum, and kinetic
energy together provide the familiar hydrodynamic equations for the
large-scale dynamics of a collisionless gas or plasma.  Then the fact
that a plasma cannot support any significant large-scale electric field
in its own moving frame of reference converts Faraday's induction
equation to the familiar magnetohydrodynamic induction equation, showing
that the magnetic field is transported bodily with the moving plasma.
Partial ionization and/or the absence of collisions do not alter this
situation.

The idea of an electric circuit analog to describe a time dependent
magnetohydrodynamic system is in qualitative error because there are
none of the inductive effects that appear in the electric circuit
analog.  In a changing magnetic field the electric current changes
freely in the manner prescribed by Ampere's law, and the plasma avoids
the inductive effects by moving always in the frame of reference in
which there is no significant electric field.  The fact is that the
electric current is a secondary physical property, driven by the
magnetic field, and having no dynamical powers to drive the plasma.

********************************************************************


________________________________________________
Harlan E. Spence
Professor of Astronomy
Boston University Department of Astronomy
and Center for Space Physics
CAS Room 410
725 Commonwealth Avenue
Boston, MA 02215
Phone: (617) 353-7421
Fax: (617) 353-6463
http://www.bu.edu/dbin/astronomy/people.php?id=23
_________________________________________________