Analysis of Voyager Observations of
Ion and Electron Phase Space Densities in the Magnetospheres
of Jupiter and Saturn, Mark Paonessa, Ph.D. Dissertation,
Univ. of Kansas, 1983.
Data from the Low Energy Charged Particle
experiment aboard the Voyager spacecraft were used
to calculate ion and electron phase space densities
in the magnetospheres of Jupiter and Saturn. These
were calculated at constant first and non-zero
second adiabatic invariants using real pitch angle
and energy spectrum information. These calculations
are used to infer the nature of charged particle
sources, losses, and transport in the inner
magnetospheric regions. Traditional dipolar as well
as current, non-dipolar models were used to
represent the planetary magnetic fields of Jupiter
and Saturn. At Jupiter the general nature of the
transport is consistent with inward diffusion from
the outer magnetosphere, combined with losses near
the orbit of Io. These apparent losses are not
consistent with simple satellite sweeping by Io
alone. It has been suggested that another loss
mechanism is at work, possibly pitch angle
scattering in the strong limit. At Saturn the data
are also consistent with a picture of inward
diffusion from the magnetospheric boundary, though
there is evidence for a source of low energy ions in
the inner magnetosphere. The O4 and Z3 magnetic
field models proposed for Jupiter and Saturn do not
change the nature of these conclusions
significantly.
Voyager 2 Encounter with Ganymede's Wake: Hydromagnetic
and Electrodynamic Process, Gul Tariq, Ph.D. Dissertation,
Univ. of Kansas, 1984.
Voyager 2's passage through the corotation wake
region of Ganymede found disturbances in the
energetic particle and magnetic field data. To
explain the nature of the disturbances, an
investigation of the interaction of the Jovian
plasma with Ganymede is carried out. A series of
computer simulations, supported by appropriate
theories, are made. Three different aspects of the
interaction are studied: (1) A magnetic field model
is proposed to describe Alfvenic disturbances caused
by Ganymede. Numerical simulations show that the
interaction of ensembles of ions with perturbed
fields modulates the energies of the ions. The
amount of modulation depends on the Alfven mach
number of the ambient plasma, the ion energy and the
pitch angle of the ions. (2) The electrodynamic
processes associated with the plasma-Ganymede
interaction and the plasma expansion into the cavity
are simulated using a particle-in-cell method. The
distribution of ions, potentials, ion and electron
thermal and drift energies in the wake region are
obtained. (3) Using linear MHD theory, conditions
for excitation and growth of the Kelvin-Helmholtz
instability are investigated. Theoretical conditions
for the existence of magnetosonic waves and
transverse Alfven waves are also examined.
An Analysis of the Performance of the Magnetic Deflection
System in the Voyager Low Energy Charged Particle
Experiment, Sheela Shodhan, Master's Thesis, Univ. of
Kansas, 1988. (The entire thesis is onlinehere.)
The Beta and the Gamma detectors
employed in the Low Energy Magnetospheric Particle
Analyzer (LEMPA) sensor subsystem of the Low Energy
Charged Particle Experiment (LECP) onboard Voyagers
1 and 2 primarily measure low energyณ15
keV electrons.
This thesis based upon the method of Wu [5]
presents the responses of these detectors for
different incident electron energies by developing
numerical models for the magnetic field and sensor
subsystem geometry and by developing numerical
procedures to follow the particle trajectories
inside the sensor subsystem.
We find that for both the detectors, the
geometric factors increase with energy, reach a
maximum and then decrease with increasing energy.
For the Gamma detector, the maximum is at about
E=500 keV while for the Beta detector, the maximum
is at about E=160 keV.
The Impact of Trapped Radiation on
Natural Satellites Imbedded in Planetary Magnetospheres, E.
V. Bell II, Ph.D. Dissertation, Univ. of Kansas, 1989.
Multiple spacecraft encounters with the
magnetospheric regions surrounding the gaseous
giants in our solar system have shown time and
spatial variations in the durably trapped particle
population and the magnetic field itself. Many
of the proposed mechanisms for these variations
involve the interaction of the ambient medium with
the natural satellites imbedded in the
magnetosphere. Several studies have been made of
this interaction, with varying degrees of success,
but few have combined all of the complexities which
the problem has required. Data taken by Voyager 1
during its flyby of Europa's orbit is used as a case
study in the complications of traditional
approaches. A means of resolving some of these
difficulties is presented. A method for tracing
particles from their observation point by the
spacecraft is used to explain some of the energy and
pitch angle dependencies of the Voyager 1
observations.
Observations by Voyager 1 of the Low
Energy Ion Component of Anomalous Cosmic Rays from 83 AU to
91 AU, Chris Mosley, Ph.D. Dissertation, Union Institute and
University, 2005.
Observations made by Voyager
1 of the low energy ion component of the anomalous
cosmic rays from 83 AU (astronomical units) to 91
AU, which relates to the years 2002 and 2003, are
studied. During this time period, specifically
2002/200 to 2003/044, Voyager 1 encountered a
previously unobserved environment, which may be
indicative of the first encounter with the
termination shock. This period is therefore of
extreme importance, and may have a profound impact
on current theory pertaining to the termination
shock. Investigation of this period involved
the calculation of a count rate for the main
particle species (protons, alpha particles, and
oxygen) to study changes in the particle density,
and the comparison of the resulting fluxes with
those done at other energies to see if there is
consistency in the energy spectrum. Also, temporal
correlations are done to study the count rate
behavior between the first and second halves of 2002
at Voyager 1, and for 2002 at Voyager 2 for the
three main particle species. The results of these
investigations will be used to infer whether or not
the signature characteristics of a termination shock
crossing, as described by the MHD equations, were
present during the 2002/200 to 2003/044 period.
Further, the kinetic
pressure components parallel and perpendicular to
the interplanetary magnetic field are calculated for
the 2002/200 to 2003/044 period to see if the
conditions were sufficient for a firehose or mirror
plasma instability to occur. If so, then this could
give an alternate explanation of the Voyager 1
observations, as well as the need of a MHD-described
termination shock.
Results indicate that the
observations by Voyager 1 during this period can be
interpreted as showing the characteristics of a
MHD-described termination shock. However, during
this period conditions were sufficient for a
firehose instability to occur as well, allowing a
possible alternative explanation.
Therefore, a definitive
resolution as to what Voyager 1 observed during
2002/200 to 2003/044, whether a MHD-described
termination shock or a plasma instability region of
some other phenomenon, is still unknown, and
continued analysis of this period is needed to
arrive at a more conclusive answer.
