Date of Award

3-2022

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Engineering Physics

First Advisor

Daniel J. Emmons, PhD

Abstract

A climatology of sporadic-E (Es) derived from a combined data set of GPS radio occultation (GPS-RO) and ground-based ionosonde soundings is presented for the period from September 2006 to February 2019. The ionosonde soundings were measured using the Lowell Digisonde International (LDI) Global Ionosphere Radio Observatory (GIRO) network consisting of 65 sites and 13,141,060 total soundings. The GPS-RO observations were taken aboard the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites and processed using two binary Es detection algorithms, totaling 9,072,922 occultations. The first algorithm is an S4 amplitude threshold calibrated to the occurrence of any blanketing Es (fbEs) with no lower limit on frequency, and the second is a threefold phase perturbation criteria calibrated to the occurrence of fbEs ≥ 3 MHz. It was found that Es primarily occurs in mid-latitude regions (10o-60o geomagnetic latitude) in the late afternoon and early evening (1500-2000SL). Auroral Es occurs later, with a peak occurrence rate (OR) between 1900-2300SL. Es has a strong seasonal dependence, where Es ORs are much higher during local summer. The effects of geomagnetic storming and solar cycle on Es ORs are also studied. Using the geomagnetic indices Kp, AE, DST, and IMF Bz, a strong positive correlation between auroral Es and geomagnetic storming was found. Equatorial and mid-latitude Es is not strongly correlated with geomagnetic activity. The solar cycle, as a function of the relative sunspot number (R), has a strong negative correlation with Es ORs. Due to a shift in the prevailing wind patterns during solar active periods, Es ORs actually decrease even though total ionosphere ionization rates increase.

AFIT Designator

AFIT-ENP-MS-22-M-096

DTIC Accession Number

AD1167033

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