Heating the Polar Atmosphere – Solar Storms & Space Debris

Importance of the area of research concerned:

Debris in low Earth orbit is a growing, major hazard for satellites; even small pieces can cause significant damage and there are upwards of a million objects smaller than 10 cm diameter. The lifetime of this debris is governed by changes in upper atmospheric density (in the thermosphere), which induces drag and de-orbits debris; climate changes has resulted in a slow, downward density trend in the thermosphere. Solar radiation is the biggest factor in causing the atmosphere to expand and increase drag; the next, and more variable, factor is Space Weather. Solar storms lead to (Joule) heating of the polar thermosphere and increase drag but there is still much we do not yet understand about their impact and models for predicting global density perform poorly. We need to improve our understanding of atmospheric joule heating and its predictability to help guard against the threat of space debris.

Project summary:

Outcomes from the project will improve our predictive capability of space debris and so help to protect our satellite infrastructure that passes through low Earth orbit. The project will use data take over several decades from ionospheric radar in the arctic to determine the levels and variability of joule heating in response to different types of Space Weather. Together with a better estimate of solar irradiance, this will be used to constrain a global climate model to determine the thermosphere change relative to unconstrained model runs on varying timescales.

What the student will do:

From 25 years (over 2 solar cycles) of solar wind data the student will identify instances of two types of space weather events: co-rotating interaction regions (CIR) and coronal mass ejections (CME). They will then combine data from the EISCAT radars (www.eiscat.com) with measurements of the ionospheric electric field from the SuperDARN network of radars (http://vt.superdarn.org/tiki-index.php) to get values of joule heating. Using the times of CMEs and CIR they will perform superposed epoch analyses to build up a temporal and spatial pattern of the average event and the extremes. These will be applied to the Whole Atmosphere Community Climate Model –X (WACCM-X) to identify changes in thermosphere density and the impact this would have on satellite orbits. The effects of the solar cycle variability in the EUV irradiance will also be included. A long model run will be carried out to establish the cumulative effect on the satellite environment.