Solar prominence modelling and plasma diagnostics at ALMA wavelength

Rodger, A. and Labrosse, N. (2017) Solar prominence modelling and plasma diagnostics at ALMA wavelength. Solar Physics, 292(9), 130. (doi:10.1007/s11207-017-1161-9)

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Abstract

Our aim is to test potential solar prominence plasma diagnostics as obtained with the new solar capability of the Atacama Large Millimeter/submillimeter Array (ALMA). We investigate the thermal and plasma diagnostic potential of ALMA for solar prominences through the computation of brightness temperatures at ALMA wavelengths. The brightness temperature, for a chosen line of sight, is calculated using the densities of electrons, hydrogen, and helium obtained from a radiative transfer code under non-local thermodynamic equilibrium (non-LTE) conditions, as well as the input internal parameters of the prominence model in consideration. Two distinct sets of prominence models were used: isothermal-isobaric fine-structure threads, and large-scale structures with radially increasing temperature distributions representing the prominence-to-corona transition region. We compute brightness temperatures over the range of wavelengths in which ALMA is capable of observing (0.32 – 9.6 mm), however, we particularly focus on the bands available to solar observers in ALMA cycles 4 and 5, namely 2.6 – 3.6 mm (Band 3) and 1.1 – 1.4 mm (Band 6). We show how the computed brightness temperatures and optical thicknesses in our models vary with the plasma parameters (temperature and pressure) and the wavelength of observation. We then study how ALMA observables such as the ratio of brightness temperatures at two frequencies can be used to estimate the optical thickness and the emission measure for isothermal and non-isothermal prominences. From this study we conclude that for both sets of models, ALMA presents a strong thermal diagnostic capability, provided that the interpretation of observations is supported by the use of non-LTE simulation results.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Labrosse, Dr Nicolas and RODGER, ANDREW
Authors: Rodger, A., and Labrosse, N.
College/School:College of Science and Engineering
College of Science and Engineering > School of Physics and Astronomy
Journal Name:Solar Physics
Publisher:Springer
ISSN:0038-0938
ISSN (Online):1573-093X
Published Online:04 September 2017
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in Solar Physics 292(9): 130
Publisher Policy:Reproduced under a Creative Commons license

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
714151STFC DTPMartin HendryScience & Technology Facilities Council (STFC)ST/N504075/1S&E P&A - PHYSICS & ASTRONOMY
631581Consolidated grant in solar and astrophysical plasmasLyndsay FletcherScience & Technology Facilities Council (STFC)ST/L000741/1S&E P&A - PHYSICS & ASTRONOMY