Ionization memory of plasma emitters in a solar prominence

¹ Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
² Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
³ Institute d’Astrophysique, 98 bis Boulevard Arago, 75014 Paris, France
⁴ Istituto ricerche solari Aldo e Cele Daccó (IRSOL), Universitá della Svizzera italiana, Via Patocchi 57, 6605 Locarno-Monti, Switzerland

^⋆ Corresponding author: hbalthasar@aip.de

Received: 16 July 2024
Accepted: 7 March 2025

Abstract

Aims. In the low-collisional, partially ionized plasma (PIP) of solar prominences, uncharged emitters might show different signatures of magnetic line broadening than charged emitters. We investigate if the widths of weak metal emissions in prominences exceed the thermal line broadening by a different amount for charged and for uncharged emitters.

Methods. We simultaneously observe five optically thin, weak metal lines in the brightness center of a quiescent prominence and compare their observed widths with the thermal broadening.

Results. The inferred nonthermal broadening of the metal lines does not indicate systematic differences between the uncharged Mg b₂ and Na D₁ and the charged Fe II emitters, only Sr II is broader.

Conclusions. The additional line broadening of charged emitters can reasonably be attributed to magnetic forces. That of uncharged emitters can then come from their temporary state as ions before recombination. Magnetically induced velocities will be retained some time after recombination. Modelling PIPs then requires consideration of a memory of previous ionization states.