Observational detection of drift velocity between ionized and neutral species in solar prominences

TL;DR

This study detects ion-neutral drift velocities in solar prominences, revealing transient decoupling of ion and neutral plasma motions with velocities of several hundred m/s, using high-resolution spectral data.

Contribution

It provides the first observational evidence of ion-neutral drift velocities in solar prominences through simultaneous spectral analysis of different ionization states.

Findings

Detected ion-neutral drift velocities of several hundred m/s.

Confirmed strong correlation between ion and neutral velocities in most cases.

Identified transient decoupling events with coherent drift signatures.

Abstract

We report a detection of differences in ion and neutral velocities in prominences using high resolution spectral data obtained in September 2012 at the German Vacuum Tower Telescope (Observatorio del Teide, Tenerife). A time series of scans of a small portion of a solar prominence was obtained simultaneously with a high cadence using the lines of two elements with different ionization states, namely the CaII 8542 A and the HeI 10830 A. Displacements, widths and amplitudes of both lines were carefully compared to extract dynamical information about the plasma. Many dynamical features are detected, such as counterstreaming flows, jets and propagating waves. In all the cases we find very strong correlation between the parameters extracted from the lines of both elements, confirming that both trace the same plasma. Nevertheless, we also find short-lived transients where this correlation is lost. These transients are associated with the ion-neutral drift velocities of the order of several hundred m/s. The patches of non-zero drift velocity show coherence on time-distance diagrams.