The connection of Type II Spicules to the Corona

TL;DR

This paper investigates whether Type II spicules heat plasma to coronal temperatures and supply mass to the solar corona, using hydrodynamical models to predict observable Doppler shifts, with current evidence being inconclusive.

Contribution

It introduces 1D hydrodynamical models with time-dependent ionization to analyze the heating and mass transfer of Type II spicules to the corona.

Findings

Models predict significant Doppler shifts of 60-90 km/s between chromosphere and corona.

Current observational data are limited and do not conclusively confirm the predicted shifts.

Future IRIS observations are needed to test the model predictions.

Abstract

We examine the hypothesis that plasma associated with "Type II" spicules is heated to coronal temperatures, and that the upward moving hot plasma constitutes a significant mass supply to the solar corona. 1D hydrodynamical models including time- dependent ionization are brought to bear on the problem. These calculations indicate that heating of field-aligned spicule flows should produce significant differential Doppler shifts between emission lines formed in the chromosphere, transition region, and corona. At present, observational evidence for the computed 60-90 km/s differential shifts is weak, but the data are limited by difficulties in comparing the proper motion of Type- II spicules, with spectral and kinematic properties of associated transition region and coronal emission lines. Future observations with the upcoming IRIS instrument should clarify if Doppler shifts are consistent with the dynamics modeled here.