Temperature Bounds on X-ray jets in the solar atmosphere (Master's Thesis)

Abstract

Coronal X-ray jets are small phenomena found in coronal holes, distinguished by an outward collimated plasma flow and brightening at the base of the flow. Such jets could have some impact in two questions in heliophysics, the first being that of what powers the solar wind, and the second being that of the coronal heating problem. While many properties of jets have been thoroughly studied with large sample sets, the temperature of these jets is less well known. This project looks at data taken from the Atmospheric Imaging Assembly aboard the Solar Dynamics Observatory for four jet events, three "blowout" jets and one "standard" jet, and uses regularised differential emission measure inversion to analyse their temperatures. It was found that jets have strong emissions in the 0.8-3MK range, with blowout jets also exhibiting emissions at around 10MK.

Background

For part III of the Natural Sciences Tripos (which results in an MSci degree), I specialised in Astrophysics. The nice part of working at the Institute of Astronomy (IoA) in part III is that we got to do original research for our theses, while still contained at the Centre for Mathematical Sciences (CMS), essentially remaining part of the Department of Applied Mathematics and Theoretical Physics (DAMTP). We therefore got the thrill of doing something completely new, which our friends actually doing part III in DAMTP did not, while having the far superior teaching and resources of the CMS (as compared to the IoA itself whose teaching was, for the most part, quite dire).

I worked with Prof. Helen Mason and Dr. Giulio Del Zanna, whose specialisms were in the study of the Sun, specifically the magnetohydrodynamics of our closest star.

One of the big gaps in our understanding of the Sun is known as the coronal heating problem [1] (CHP): why is the Sun’s coronal temperature 1–2M Kelvin while the photosphere is at a mere 6000 Kelvin.

My research focussed on measuring temperature bounds for tiny coronal mass ejections (CMEs). The exact mechanism for these CMEs is not known for certain, and the exact temperature ranges are not well understood either. Increasing the accuracy of our understanding of the temperature ranges will eliminate or support the various theories around these CMEs and the CHP.