Determination of Coronal Mass Ejection physical parameters from combination of polarized visible light and UV Lyman-$\alpha$ observations

Abstract

Visible-light observations of Coronal Mass Ejections (CMEs) performed with coronagraphs and heliospheric imagers (in primis on board the SOHO and STEREO missions) have offered so far the best way to study the kinematics and geometrical structure of these fundamental events. Nevertheless, it has been widely demonstrated that only combination of multi-wavelength data (including X-ray spectra, EUV images, EUV-UV spectra, and radio dynamic spectra) can provide complete information on the plasma temperature and density distributions, non-thermal motions, magnetic fields, and other physical parameters, for both CMEs and CME-related phenomena. In this work, we analyze three CMEs by combining simultaneous data acquired in the polarized visible light by the LASCO-C2 coronagraph and in the UV H I Lyman-$\alpha$ line (1216 Å) by the UVCS spectrometer, in order to estimate the CME plasma electron density (using the polarization-ratio technique to infer the 3D structure of the CME) and temperature (from the comparison between the expected and measured Lyman-$\alpha$ intensities) along the UVCS field of view. This analysis is primarily aimed at testing the diagnostic methods that will be applied to coronagraphic observations of CMEs delivered by the Metis instrument on board the next ESA-Solar Orbiter mission. We find that CME cores are usually associated with cooler plasma ($T\sim 10^6$ K), and that a significant increase of the electron temperatures is observed from the core to the front of the CME (where $T>10^{6.3}$ K), which seems to be correlated, in all cases, with the morphological structure of the CME as derived from visible-light images.

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Cited by in corpus (10)

• The Solar Orbiter mission -- Science overview
• Metis: the Solar Orbiter visible light and ultraviolet coronal imager
• Stellar coronal mass ejections II. Constraints from spectroscopic observations
• Hot prominence detected in the core of a Coronal Mass Ejection: III. Plasma filling factor from UVCS Lyman-$\alpha$ and Lyman-$\beta$ observations
• First Determination of 2D Speed Distribution within the Bodies of Coronal Mass Ejections with Cross-Correlation Analysis
• A Coronal Mass Ejection followed by a prominence eruption and a plasma blob as observed by Solar Orbiter
• Combining White Light and UV Lyman-alpha Coronagraphic Images to determine the Solar Wind Speed: the Quick Inversion Method
• Extensive Study of a Coronal Mass Ejection with UV and WL coronagraphs: the need for multi-wavelength observations
• Hydrogen Non-Equilibrium Ionisation Effects in Coronal Mass Ejections
• Parameter effects on the total intensity of H I Lyα line for a modelled coronal mass ejection and its driven shock