Motion of charged particles in pulsar magnetospheres
Zachariades, Haris Andrea
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https://hdl.handle.net/2142/18911
Description
Title
Motion of charged particles in pulsar magnetospheres
Author(s)
Zachariades, Haris Andrea
Issue Date
1992
Doctoral Committee Chair(s)
Jackson, E.A.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
charged particles
pulsar magnetospheres
Lorentz-Dirac equation
Language
en
Abstract
The motion of charges in the magnetosphere of pulsars is studied from two complementary
points of view: (i) For the case of aligned magnetic and rotational axes
we solve a fluid version of the Lorentz-Dirac equation, in the Landau approximation,
for a two-component plasma. We start from an approximately force-free initial condition
and numerically integrate the equations of motion for a time equal to 1.6%
of one stellar rotation period. We find that the system tends to a charge-separated
state in which a negative charge region above the poles is separated by a vacuum gap
from a positive charge region near the equator. We see the formation of force-free
regions and a tendency of the vacuum gap to spread as the integrations proceed. The
energies attained by the charges are only mildly relativistic and radiation reaction
does not play an important role during the integrations. The negative charge above
the polar region is electrostatically bound and there is a force-free region towards
which negative charge tends to flow. Some positive charge is magnetically confined
near the stellar equator and other positive charge crosses magnetic field lines moving
outward to the region beyond the light cylinder. The outward motion of positive
charge is due to the relative magnitudes of the electric and magnetic fields. (ii) For
the case of non-aligned axes we study the single particle dynamics for electrons movlll
ing in the region beyond the light cylinder, again using the Landau approximation
to the Lorentz-Dirac equation. The effect of the inner magnetosphere is taken into
account by adding a central attractive charge. We find that there exists a class of solutions
corresponding to bounded orbits beyond the light cylinder. In an independent
particle picture, particles started with different initial conditions within the basin of
attraction of this class of orbits eventually form corotating patterns beyond the light
cylinder. For a frequently occuring particle configuration we find emission from radio
to 1-ray frequencies with a spectrum different than that of synchrotron radiation.
We also show the existence of phase locked dynamics for this system. These results
suggest a possible structure of the outer magnetosphere of a non-aligned pulsar.
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