Dartmouth Events

Physics & Astronomy - Senior Honor Thesis - Clara Goldberger, Dartmouth College

Title: "A new method of estimating density profiles of Auroral roars and observation of presence of a lower density gap"

Tuesday, May 31, 2022
2:00pm – 3:00pm
Wilder 115
Intended Audience(s): Public
Categories: Lectures & Seminars

Abstract: Charged particles from the sun create an electron density in the ionosphere and their interaction emits the colorful light and radio waves known as the aurora. This thesis will focus on roars, one type of auroral radio emission, which are emitted from the topmost layer of the ionosphere, also known as the F region. We have three sets of data describing roars and the electron density of the ionosphere. One set describing these roars have been collected by antennas located in Sondrestrom, Greenland and this data includes the direction of the arrival of the rays emitted from the roar. Additionally, density profiles of the ionosphere can be obtained from the Incident Scatter Radar (ISR), also at Sondrestrom, but unfortunately these profiles are only recorded occasionally. Lastly, there are electron density profiles models of the ionosphere from the International Reference Ionosphere (IRI), but this data is from a model. The first step of my project involved determining the necessary shift of the IRI electron density profiles to match the ISR profiles on ~20 selected days. The second step of the project is determining, for those shifts, the percentage of roar signals that reach the same altitude as the known source altitude of a roar emission with the same frequency: the origin is matched with the origin of the 2fce roar emission. I determined a consistent percentage of rays that meet this condition that indicates that the IRI data has been shifted to match the ISR data. The development of this procedure will hopefully make the density estimation of the IRI model more accurate and usable more frequently than the ISR is available. While working to determine the required shift percentages, 2D color plots of the electron density were made from the ISR data and there is a common reoccurrence of a lower density gap in the region poleward of the auroral arc. For a second part of this thesis, I discuss if this gap is real, by determining frequency of occurrence and previous observation in other papers. I also discuss a future project of taking many horizontal cuts of the density profiles at the height at which they occur and superimposing them. If this gap is still present in the superimposed cuts, it would confirm the density gap. I then hope to analyze what the implications are on radio wave propagation and where the waves are seen.

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Meeting ID: 958 0314 2133
Passcode: Goldberger


For more information, contact:
Tressena Manning

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