Abstract
The minimum temperature in the solar chromosphere is as yet unknown. The coolest gas is expected to exist in the quiet chromosphere where hot shocks travel upward through a cool background atmosphere. Analysis of observations in CO lines puts the minimum temperature of this background at or lower than 2750~K.
I will review the various physical processes that govern the temperature structure of the quiet chromosphere.
I will present results from a 2D numerical simulation that contains a reasonable approximation of all the relevant physics. The minimum temperature in this simulation is below 1900 K.
I will discuss suggestions for observations that can detect such cool pockets of gas and discuss improvements of the simulation needed to obtain a more reliable theoretical estimate of the minimum temperature.