Three Dimensional Structure and Energy Balance of a Coronal Mass Ejection

TL;DR

This study investigates the three-dimensional structure and energy balance of a coronal mass ejection (CME), emphasizing the necessity of continuous heating and analyzing the energy distribution within the CME plasma.

Contribution

It provides new constraints on the heating rates in CMEs, demonstrating that significant energy must go into heating, exceeding kinetic energy, and challenges the sufficiency of thermal conduction for CME heating.

Findings

Continuous heating is essential to match UVCS observations.

Approximately 75% of magnetic energy must convert into heat.

Thermal conduction alone cannot explain the observed heating.

Abstract

The Ultraviolet Coronagraph Spectrometer (UVCS) observed Doppler shifted material of a partial Halo Coronal Mass Ejection (CME) on December 13 2001. The observed ratio of [O V]/O V] is a reliable density diagnostic important for assessing the state of the plasma. Earlier UVCS observations of CMEs found evidence that the ejected plasma is heated long after the eruption. We have investigated the heating rates, which represent a significant fraction of the CME energy budget. The parameterized heating and radiative and adiabatic cooling have been used to evaluate the temperature evolution of the CME material with a time dependent ionization state model. The functional form of a flux rope model for interplanetary magnetic clouds was also used to parameterize the heating. We find that continuous heating is required to match the UVCS observations. To match the O VI-bright knots, a higher heating rate is required such that the heating energy is greater than the kinetic energy. The temperatures for the knots bright in Ly$\alpha$ and C III emission indicate that smaller heating rates are required for those regions. In the context of the flux rope model, about 75% of the magnetic energy must go into heat in order to match the O VI observations. We derive tighter constraints on the heating than earlier analyses, and we show that thermal conduction with the Spitzer conductivity is not sufficient to account for the heating at large heights.