UNB Physics Seminar Series-FR

Event date(s): September 21, 2023
Time(s): 01:15 PM - 02:15 PM
Category: Fredericton
Location: Fredericton

UNB Physics Department Seminar

When: Thursday, Sept. 21, 2023 @ 1:15-2:15 p.m.

Location: Toole Hall, Rm. 3

Speaker: Ben Reid

Title: Solar Energetic Particle Events and Their Impact on the High Latitude Ionosphere

Abstract:

Solar activity is the principal driver of ionospheric behaviour, principally through ionizing photons and coupling of the solar wind with the geomagnetic field. These are not the only mechanisms by which the sun can impact the upper atmosphere, and eruptions of solar plasma known as Coronal Mass Ejections can accelerate large populations of particles to relativistic velocities. These long-lived Solar Energetic Particle (SEP) events pose a significant radiation hazard to spacecraft and their payloads, and can penetrate the atmosphere to commercial aviation altitudes. The protons lose energy by ionizing the neutral atmosphere, causing order of magnitude increases in the overall ionization rate in the lowest reaches of the ionosphere. This increase in ionization creates significant changes to the temperatures and overall electron density in the D-region ionosphere. The resulting radiofrequency absorption causes communication blackouts in HF bands, and changes in propagation path for VLF signals. Successfully modelling the effects of an SEP event on the ionosphere requires accounting for the energy- and path-dependent trajectories of the protons through the geomagnetic field and neutral atmosphere, the complicated D-region chemistry, and the near absence of any direct measurements of the system.  These specific challenges shaped the design of the SEP module in the Assimilative Canadian High Arctic Ionospheric Model (A-CHAIM). Nonlinear data assimilation techniques like those used in A-CHAIM can help models of complex systems account for poorly understood or missing physical processes, and some of these strategies (and their limitations) will be presented.

Building: Toole Hall

Room Number: 3