EXPLORING THE STRUCTURE AND VARIABILITY OF THE TERRESTRIAL IONOSPHERE USING HIGH-RESOLUTION MODEL INPUTS

Physics-based ionospheric models show long-standing data model discrepancies, especially in the E-region (90-150 km) of the ionosphere. Although this region was the first to be discovered among other ionospheric layers, it is insufficiently explored due primarily to inaccurate representation of the details of the solar forcing and electrodynamical coupling in studies of the E-region. Therefore, this thesis explores the terrestrial ionosphere from 100 to 1000 km utilizing a physics-based ionospheric model titled `Atmospheric Ultraviolet Radiance Integrated Code' (AURIC, Strickland 1999) to address this perennial problem. AURIC calculates ionospheric electron density and photoelectron flux spectrum for Earth's atmosphere. Our study facilitates the acquisition of `state-of-the-art' high spectral resolution photoionization and photoabsorption cross sections along with high-resolution solar irradiance to AURIC. This improved representation of solar spectral irradiance and cross sections reduce the data-model discrepancy in terms of electron number density in the E-region and photoelectron flux calculation from 90 to 1000 km. During solar minima, AURIC electron density profiles showed strong agreement with observations, although the characteristic E-region peak near 105–110 km was absent in the model results. The model accurately reproduced the spectral shape of photoelectron fluxes when compared to satellite observations by Atmospheric Explorer-E and Fast Auroral Snapshot; however, the photoelectrons increased by approximately 25–50% in the low energy regime (10-60 eV) when compared with simulations conducted at low-resolution counterpart. Overall, our results clearly suggest that high-resolution cross sections and solar EUV inputs better capture the ionospheric physics, thereby contributing toward resolving ionospheric data–model discrepancies. In addition to ionospheric investigations, this thesis presents dedicated chapters on atmospheric gravity waves in Earth's lower atmosphere and coronal mass ejection propagation in solar physics, showcasing the interdisciplinary nature of space physics research.

Author

• Sakib, Md Nazmus

• AURIC
• electron density
• high-resolution cross section
• ionosphere
• photoelectron flux
• satellite data analysis

Identifier

hdl:1920/14769

OAI identifier oai:identifier

oai:MARS:1920/14769