Context :

Aims : To study spatially-resolved chromospheric oscillations of the quiet Sun in the mm-domain at a resolution of a few arcsec , typically 2.4″ \times 4.5″ .

Methods : We used Atacama Large millimeter and sub-millimeter Array ( ALMA ) time-series of interferometric observations of the quiet Sun obtained at 3 mm with a 2-s cadence and a spatial resolution of a few arcsec .
The observations were performed on March 16 , 2017 and seven 80″ \times 80″fields-of-view going from disk center to limb were covered , each one observed for 10 min , therefore limiting the frequency resolution of the power spectra to 1.7 mHz .
For each field of view , masks for cell and network were derived , and the averaged power spectral densities ( PSDs ) for the entire field of view , cell and network were computed .
The resulting power spectra were fitted with an analytical function in order to derive the frequency and the root-mean-square ( rms ) power associated with the peaks .
The same analysis , over the same fields of view and for the same intervals , was performed for simultaneous Atmospheric Imaging Assembly ( AIA ) image sequences in 1600 Å .

Results : Spatially-resolved chromospheric oscillations at 3 mm , with frequencies of 4.2 \pm 1.7 mHz are observed in the quiet Sun , in both cell and network .
The coherence length-scale of the oscillations is commensurate with the spatial resolution of our ALMA observations .
Brightness-temperature fluctuations in individual pixels could reach up to a few hundred K , while the spatially averaged power spectral densities yield rms in the range \approx 55-75 K , i.e. , up to \approx 1 \% of the averaged brightness temperatures and exhibit a moderate increase towards the limb .
For AIA 1600 Å the oscillation frequency is 3.7 \pm 1.7 mHz .
The relative rms is up to 6 % of the background intensity , with a weak increase towards disk center ( cell , average ) .
ALMA 3 mm time-series lag AIA 1600 Å by \approx 100 s , which corresponds to a formation-height difference of \approx 1200 km , representing a novel determination of this important parameter .

Conclusions : The ALMA oscillations that we detected exhibit higher amplitudes than those derived from the lower ( \approx 10″ ) resolution observations at 3.5 mm by White et al .
( 2006 ) .
Chromospheric oscillations are , therefore , not fully resolved at the length-scale of the chromospheric network , and possibly not even at the spatial resolution of our ALMA observations .
Any study of transient brightenings in the mm-domain should take into account the oscillations .