Dynamics of the solar chromosphere. II. CaIIH2 nu and K-2 nu grains versusinternetwork fields

We use the Advanced Stokes Polarimeter at the NSO/Sacramento Peak Vacuum To wer Telescope to search for spatio-temporal correlations between enhanced m agnetic fields in the quiet solar internetwork photosphere and the occurren ce of Ca II H-2V grains in the overlying chromosphere. We address the quest ion of whether the shocks that produce the latter are caused by magnetism-r elated processes, or whether they are of purely hydrodynamic nature. The ob servations presented here are the first in which sensitive Stokes polarimet ry is combined synchronously with high-resolution Ca II H spectrometry. We pay particular attention to the nature and significance of weak polarizatio n signals from the internetwork domain, obtaining a robust estimate of our magnetographic noise level at an apparent flux density of only 3 Mx cm(-2). For the quiet Sun internetwork area analyzed here, we find no direct corre lation between the presence of magnetic features with apparent flux density above this limit and the occurrence of H-2V brightenings. This result cont radicts the one-to-one correspondence claimed by Sivaraman & Livingston. We also find no correspondence between H-2V grains and the horizontal-field i nternetwork features discovered by Lites et al.