Undergraduate Honors Theses

Thesis Defended

Spring 2019

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Astronomy

First Advisor

Nick Schneider

Second Advisor

Ann-Marie Madigan

Third Advisor

Cora Randall

Abstract

Understanding the connection between the lower and upper atmospheres is key to determining the atmospheric history of Mars. One such tracer of the connection between Mars’s thermosphere and mesosphere is the nitric oxide (NO) nightglow, an atmospheric airglow phenomenon which is indicative of atmospheric flux between the nightside thermosphere and mesosphere. For my thesis, I analyze a set of altitude profiles of the NO nightglow observed by the Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile Evolution (MAVEN) mission. Using a toy model of the NO recombination, I fit the altitude profiles to determine some char- acteristic atmospheric quantities and how they change over the course of a day during particular seasons and on average between seasons. During winter, I find that the peak altitude does not vary appreciably with local time, while during equinox and summer the peak altitude decreases during evening, reaching a minimum before midnight, then increasing during the early morning hours toward dawn. Between seasons, I find the average peak altitude varies by about 20km between summer/equinox at around 70km and polar winter at around 50km. These results suggest the diurnal variation depends on daily temperature variation, while the seasonal variation exhibits a more complex connection to variables like average nighttime temperature and other factors like the dayside photodissociation rate producing atomic oxygen and nitrogen.

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