Physics Department Seminar Series-FR

Event date(s): February 08, 2024
Time(s): 01:15 PM - 02:15 PM
Category: Fredericton
Location: Fredericton

Join us for the weekly Physics seminar series!

Date: February 8, 1:15-2:15 p.m.

Location: Toole Hall, Room 3

Speaker: Kaili Song

Title: Investigating the Fresnel scale from ionospheric scintillation spectra

Abstract: Trans-ionospheric radio signals recorded on the ground exhibit random amplitude and phase fluctuations, which are attributed to irregularities in the ionospheric electron density. Studying ground-based measurements of these radio signals can significantly contribute to our understanding of plasma instability mechanisms responsible for the development of these ionospheric structures. In this regard, radio signals emitted by the Global Positioning System (GPS) satellites recorded by the Canadian High Arctic Ionospheric Network (CHAIN) GPS receivers are exploited to analyze both amplitude and phase fluctuations.

The current ionospheric scintillation paradigm posits that amplitude fluctuations arise from diffraction caused by Fresnel scale ionospheric structures, while refraction is responsible for signal phase variations. The amplitude power spectrum profile consistently displays a rollover frequency, which is not equal to the Fresnel frequency under the Taylor hypothesis. The phase screen approximation is used to further investigate this phenomenon and identify an empirical relation between the rollover and Fresnel frequencies. Notably, we have found that the rollover frequency is consistently greater than the Fresnel frequency. Moreover, upon refining the cut-off frequency to mitigate refractive effects on the phase power spectrum, we have found the cut-off frequency to consistently exceed the rollover frequency. Furthermore, the Fresnel frequency extracted from two-component phase spectra tends to be larger than the rollover frequency. Based on our findings, we conjecture that the Fresnel scales are associated with ionospheric irregularities, which cause scintillation. 

Building: Toole Hall

Room Number: 3