Dynamics of the Solar Chromosphere. II. Ca II H2V and K2V Grains versus Internetwork Fields

Abstract

We use the Advanced Stokes Polarimeter at the NSO/Sacramento Peak Vacuum Tower Telescope to search for spatio- temporal correlations between enhanced magnetic fields in the quiet solar internetwork photosphere and the occurrence of Ca II H2v grains in the overlying chromosphere.We address the question of whether the shocks that produce the latter are caused by magnetism-related processes,or whether they are of purely hydrodynamic nature. The observations presented here are the first in which sensitive Stokes polarimetry is combined synchronously with high- resolution Ca II H spectrometry. We pay particular attention to the nature and significance of weak polarization signals from the internetwork domain,obtaining a robust estimate of our magnetographic noise level at an apparent flux density of only 3 Mxcm^-2 . For the quiet Sun internetwork area analyzed here,we find no direct correlation between the presence of magnetic features with apparent flux density above this limit and the occurrence of H2v brightenings.This result contradicts the one-to-one correspondence claimed by Sivaraman &Livingston (1982).We also find no correspondence between H2v grains and the horizontal-?eld internetwork features discovered by Lites et al.(1996).