Two dimensional hybrid simulations of small scale obstacles in the solar wind
Hopcroft, Matthew William (2001) Two dimensional hybrid simulations of small scale obstacles in the solar wind. PhD thesis, University of Warwick.
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The structure and dynamics of the solar wind interaction with two small
scale obstacles (of the order of a pickup ion gyroradius) is examined. These are a
comet, comparable to Grigg-Skjellerup, and a weakly ionospheric planet. We also
perform a pilot study of an intrinsically magnetized planet in such flow, in preparation
for a future three-dimensional simulation. Here, we use two-dimensional hybrid
simulations (particle ions, fluid electrons) and consider different solar wind Alfven
Mach number flow (MA) and interplanetary magnetic field orientation relative to
this plane. This allows control of the available wave types.
The cometary simulations display magnetosonic "turbulence" as MA is increased,
when the field is perpendicular to the simulation plane. If we allow parallel
propagating modes by setting the field parallel to the plane, we find the "turbulence"
significantly changes in scale and extent, suggesting resonant growth of Alfven ion
cyclotron waves in the presence of magnetosonic "turbulence" occurs. Free energy
is available from picked up cometary ions. The process depends on the cometary ion
density, which strongly varies, and we conclude this explains the broadband nature
of the disturbances.
In the perpendicular field orientation, the planetary source produces a novel
two tail structure which continuously strips the planetary ionosphere. We find these
tails have very distinct characteristics, resulting in the wake being filled relatively
quickly downstream, by complex structure. At higher MAl magnetosonic "turbulence"
again appears. Switching the field parallel to the plane causes massive field
line draping and pile-up, and causes instability. A long lasting wake appears, and
we conclude that a three-dimensional simulation is required.
The magnetized ionospheric planet pilot study proved difficult to scale accurately
in two dimensions. The planetary field failed to penetrate the solar wind,
however it appears the simulation would be stable and achieve equilibrium in three
|Item Type:||Thesis or Dissertation (PhD)|
|Subjects:||Q Science > QB Astronomy|
|Library of Congress Subject Headings (LCSH):||Solar wind -- Mathematical models, Comets -- Mathematical models, Planets -- Mathematical models|
|Official Date:||March 2001|
|Institution:||University of Warwick|
|Theses Department:||Department of Physics|
|Supervisor(s)/Advisor:||Chapman, Sandra C.|
|Sponsors:||Engineering and Physical Sciences Research Council (EPSRC) ; Particle Physics and Astronomy Research Council (Great Britain) (PPARC)|
|Extent:||xxii, 181 p.|
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