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Title: Evolution of Halley-type comets and meteoroid streams
Author: Sekhar, A.
ISNI:       0000 0004 5367 3452
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2014
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The overall objective of the thesis is to understand the long term orbital dynamics of comets and meteoroid streams. The initial idea focused mainly on detailed analysis of Jovian resonances in Orionids and Leonids. Special emphasis was given to study their influences in causing meteoroutbursts and storms on Earth. The theoretical simulations matched with observational records to a very good degree. This work led to the curious question as to whether any resonance mechanism could be driven due to Saturn's gravity. Subsequent analysis showed that Saturn's influences can also become vital when the order of resonance (concerning Saturn) is smaller compared to that in the adjacentJovian resonances. Compact resonant structures (due to Saturn's effects) were identified in both Orionid and Leonid streams during present times. All these calculations were done solely using a Newtonian model. This raised more questions as to whether Einstein's general relativistic effects could have any substantial role during long term (of the order of thousand years) meteor shower forecasts. Analytical and numerical analysis showed that general relativistic effects could lead to significant errors (in long term forecasts) in some particular combinations (or different epochs) of Keplerian orbital elements in certain low perihelion distance (below 0.15 AU) and low semi-major axis (below 1.5 AU) meteoroid streams. Because some low perihelion distance meteoroid streams are associated with sungrazing comets, this led to the next question regarding the reason for the absence of meteor showers from this class of comets. A detailed study using Lagrange's planetary equations showed that most sungrazers cannot make the nodes of meteoroid particles Earth intersecting at low ejection velocities (of order 10 m/s). This can be used as a convincing argument to establish the absence of spectacular meteor showers on Earth from the frequently observed sungrazers so far.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available