Studies on the influence of magnetic cloud, stream interface and polar mesospheric summer echoes in the mesosphere and lower thermosphere (MLT) region using model calculations and observations.

• Main Author: Ogunjobi, Olakunle.
• Other Authors: Venkataraman, Sivakumar.
• Format: Thesis
• Language: English
• Published: 2016
• Subjects: Mesospheric thermodynamics; Magnetosphere; Mesosphere; Theses > Chemistry; Antarctic; SANAE; SANAE IV; Antarc*
• Online Access: http://hdl.handle.net/10413/12945

Ph. D. University of KwaZulu-Natal, Durban 2014. The response of Mesosphere and Lower Thermosphere (MLT) temperature to energetic particle precipitation over the Earth's polar regions is not uniform due to complex phenomena within the MLT environment. Nevertheless, the modification of MLT temperatures may require an event based study to be better observed. Three Geospace events examined in this study are: Magnetic Clouds (MC), solar wind Stream Interfaces (SI) and Polar Mesospheric Summer Echoes (PMSE). The MC is a transient ejection in the solar wind defined as the region between the preceding half of the z{ component of southward interplanetary magnetic field (IMF{Bz) and the trailing half, which contained strong northward peak or vice versa, with an accompanied large density enhancement that strongly compressed the magnetosphere. The varied instrumentation which is located not only in South African National Antarctic Expedition (SANAE) IV, but also at Halley, a same radial distance (L ~ 4) location in the Southern hemisphere, and at the vicinity of conjugate location in Northern hemisphere provide an opportunity to test the theories applied to high latitude heating rates on arrival of MC. The Halley riometer is used to monitor coincidences of absorption with arrival of a fortuitous MC that was observed on 8 November 2004. Using Monte Carlo Energy Transport Model (MCETM), the corresponding altitude of electron and proton energy distribution indicates the importance of MC triggered geomagnetic storms on mesospheric dynamics. At the arrival of SI near the Earth's bow nose, compressional streams propagate into the inner magnetosphere, where they fueled magnetospheric storms. A number of SI events were obtained close in time to the pass of temperature retrieval onboard the Thermosphere Ionosphere Mesosphere Energetic and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry (TIMED/SABER) over SANAE IV. The relationship between the ionospheric absorption measured by riometer and the layer of ...