Constraining the CME Core Heating and Energy Budget with SOHO/UVCS

TL;DR

This study analyzes the energy budget and core heating mechanisms of a CME observed by SOHO/UVCS, revealing that heating energy is comparable to kinetic energy and constraining models with observational data.

Contribution

It provides the first detailed observational constraints on CME core heating rates and compares them with MHD simulation predictions, highlighting the significance of heating in CME evolution.

Findings

CME core velocity is approximately 250 km/s.

Heating energy is comparable to kinetic energy in the CME.

Heating rates from simulations match observational constraints under certain assumptions.

Abstract

We describe the energy budget of a coronal mass ejection (CME) observed on 1999 May 17 with the Ultraviolet Coronagraph Spectrometer (UVCS). We constrain the physical properties of the CME's core material as a function of height along the corona by using the spectra taken by the single-slit coronagraph spectrometer at heliocentric distances of 2.6 and 3.1 solar radii. We use plasma diagnostics from intensity ratios, such as the O VI doublet lines, to determine the velocity, density, temperature, and non-equilibrium ionization states. We find that the CME core's velocity is approximately 250 km/s, and its cumulative heating energy is comparable to its kinetic energy for all of the plasma heating parameterizations that we investigated. Therefore, the CME's unknown heating mechanisms have the energy to significantly affect the CME's eruption and evolution. To understand which parameters might influence the unknown heating mechanism, we constrain our model heating rates with the observed data and compare them to the rate of heating generated within a similar CME that was constructed by the MAS code's 3D MHD simulation. The rate of heating from the simulated CME agrees with our observationally constrained heating rates when we assume a quadratic power law to describe a self-similar CME expansion. Furthermore, the heating rates agree when we apply a heating parameterization that accounts for the CME flux rope's magnetic energy being converted directly into thermal energy. This UVCS analysis serves as a case study for the importance of multi-slit coronagraph spectrometers for CME studies.