  The morpho-kinematics of the circumstellar envelope of oxygen-rich AGB star R
Leonis is probed using ALMA (Atacama Large Millimeter/submillimeter Array)
observations of the emission of molecular lines, including in particular
CO(2-1) and $^{29}$SiO(5-4). Evidence is found for an episode of enhanced mass
loss, a few centuries ago, that produced a broad expanding shell of mean radius
$\sim$6 arcsec and mean radial expansion velocity $\sim$5.5 km s$^{-1}$ .
Detailed scrutiny of its structure, as displayed by the emission of the CO(2-1)
line, reveals strong inhomogeneity and patchy morphology. Evidence is also
found, in particular from the morpho-kinematics of the emission of SiO, SO and
SO$_2$ lines probing the close neighbourhood of the star, for distinct gas
outflows covering broad solid angles in the south-eastern, south-western and
north-western quadrants, suggesting significant contribution of the convective
cell granulation in defining the pattern of mass ejection. A study of relative
molecular abundances in these outflows suggests that a Local Thermal
Equilibrium (LTE) description applies approximately beyond $\sim$10 stellar
radii from the centre of the star but not at the smaller angular separations
where the SO and SO$_2$ molecules are found to be confined. Near the stellar
disc, masers of the vibrationally excited SiO lines are found to probe
north-western parts of a layer of hot gas, consistent with the earlier
observation of an asymmetric expanding shell within 1-2 stellar radii from the
centre of the star. Globally, a picture dominated by episodic and patchy mass
ejections is found to prevail.
