“…In particular, the presence of a heat source or sink may give rise to the idea of penetrative convection where part of the layer has a tendency to move whereas the remainder of the layer will remain motionless until a certain point when movement in the rest of the layer "penetrates" into the stable layer and a resultant motion then ensues, cf. Altawallbeh et al [1], van den Berg et al [3], Berlengiero et al [4], Capone et al [5,6,7], Capone 1 & de Luca [8], Capone et al [9], Capone & Rionero [10], Carr [11], Chasnov & Tse [13], Hetsroni et al [19], Hill [20,21], Imamura et al [23], Kirillov et al [26], Krishnamurti [27], Kuznetsova & Sibgatullin [28], Larson [29,30], Machado et al [32], Mharzi et al [33], Papanicolaou et al [36], Prudhomme & Jasmin [37], Saravan & Nayaki [47], Shalbaf et al [49], Siddheshwar & Titus [51], Storesletten & Titus [52], Straughan [53,55,54,60,62], and Straughan & Walker [64]. Straughan [54], section 17.2, pp.…”