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Context. Short-lived (100 s or less), sub-arcsec to a couple of arcsec sized features of enhanced brightenings in the narrowband images at the H2V and K2V positions of the Ca II H&K lines in the quiet Sun are known as bright grains. These bright grains are interpreted as manifestations of acoustic shock waves in the chromosphere. Aims. We aim to study time-varying stratified atmospheric properties, such as the temperature, line-of-sight (LOS) velocity, and microturbulence inferred from observations of the bright grains during such acoustic shock events. Methods. With simultaneous observations of a quiet-Sun internetwork region in the Fe I 6173 Å, Ca II 8542 Å, and Ca II K lines acquired by the CRisp Imaging Spectro-Polarimeter and the CHROMospheric Imaging Spectrometer instruments on the Swedish 1-m Solar Telescope, we performed multi-line non-local thermodynamic equilibrium inversions using the STockholm inversion Code to infer the time-varying stratified atmosphere’s physical properties. Results. The Ca II K profiles of bright grains show enhancement in the K2V peak intensities with the absence of the K2R features. At the time of maximum enhancement in the K2V peak intensities, we found average enhancements in temperature at lower chromospheric layers (at log τ500 ≃ −4.2) of about 1.1 kK, with a maximum enhancement of ∼4.5 kK. These temperature enhancements are co-located with upflows, as strong as −6 km s−1, in the direction of the LOS. The LOS velocities at upper chromospheric layers at log τ500 < −4.2 show consistent downflows greater than +8 km s−1. The retrieved value of microturbulence in the atmosphere of bright grains is negligible at chromospheric layers. Conclusions. This study provides observational evidence to support the interpretation that the bright grains observed in narrowband images at the H2V and K2V positions of the Ca II H&K lines are manifestations of upward propagating acoustic shocks against a background of downflowing atmospheres.

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We investigated the diagnostic potential of the Stokes V profile of the Hα line to probe the chromospheric line-of-sight (LOS) magnetic field (B LOS) by comparing the B LOS inferred from the weak field approximation (WFA) with that inferred from the multiline inversions of the Caii 8542 Å, Si i 8536 Å, and Fe i 8538 Å lines using the STiC inversion code. Simultaneous spectropolarimetric observations of a pore in the Ca ii 8542 Å and Hα spectral lines obtained from the SPINOR at the Dunn Solar Telescope on 2008 December 4 are used in this study. The WFA was applied on the Stokes I and V profiles of Hα line over three wavelength ranges, viz., around line core (Δλ = ±0.35 Å), line wings (Δλ = [−1.5, −0.6], and [+0.6, +1.5] Å), and full spectral range of the line (Δλ = ± 1.5 Å) to derive the B LOS. We found the maximum B LOS strengths of ∼+800 and ∼+600 G at log τ 500 = −1 and −4.5, respectively, in the pore. The morphological map of the B LOS inferred from the Hα line core is similar to the B LOS map at log τ 500 = −4.5 inferred from multiline inversions. The B LOS map inferred from the Hα line wings and full spectral range have a similar morphological structure to the B LOS map inferred at log τ 500 = −1. The B LOS estimated from Hα using WFA is weaker by a factor of ≈0.53 than that of inferred from the multiline inversions.