Distinguished First Year Scholar: Alison Roth

ISR Advisor: Dr. Charles Carrano, Senior Research Physicist, ISR

Project Title: Occurrence Morphology of Ionospheric Scintillation during the Recent Extended Solar Minimum

The ionosphere is a rarefied region of the Earth’s upper atmosphere that is partially ionized by the sun. The distribution of free electrons in the ionosphere is dictated by production from solar radiation, transport, and loss through chemical recombination. It is also subject to physical mechanisms that generate large-scale depletions and irregularities in the ambient electron density over a wide range of spatial scales (plasma turbulence). Radio waves that propagate through these irregularities experience scattering and diffraction, causing random fluctuations in amplitude and phase referred to as scintillations. The scintillation of satellite signals can severely degrade the performance of satellite communications systems, global navigation systems such as GPS, and space radars used to conduct cloud-free, day-and-night observations of the Earth’s surface. Ionospheric irregularities and scintillations constitute one of the most important space weather threats to technological systems of the modern world which increasingly rely on trans-ionospheric radio propagation.

Ionospheric scintillations are generally most intense in the equatorial region of the globe after sunset, and the occurrence morphology depends on season, longitude, and solar activity with a high degree of night-to-night variability. While much is known about the morphology of ionospheric scintillations and the physical mechanisms that cause them, their characteristics over large portions of the globe are poorly understood. This is particularly true over the African continent which, until recently, has been largely devoid of ionospheric monitoring instruments. Boston College, in conjunction with several university and government partners, operates and maintains multiple networks of ionospheric monitoring instruments around the world, with the highest concentration of instruments in Africa and South America. These networks are dedicated to furthering our understanding of the climatology and structure of ionospheric irregularities as well as their impacts on radio wave propagation.

Alison Roth, a Distinguished First-Year Scholar, is currently conducting an investigation of the climatology and onset time of ground-based scintillation observations during the recent and extended solar minimum. This solar minimum was unexpectedly prolonged and characterized by the lowest levels of solar activity encountered this century. Her investigations will help to establish whether the physical processes leading to the formation of ionospheric irregularities during this extended solar minimum period were fundamentally different, or in fact the same processes that created irregularities throughout previous solar cycles.

Alison graduated from Brentwood High School in Brentwood, TN in 2010. She is an Environmental Geosciences major and an International Studies minor in the BC Class of 2014. In addition, Alison is an active member of the College Democrats of Boston College, the 4Boston volunteer program, and the Student Admission Program.