All irreducible regular partially invariant submodels with one noninvariant function for the equations of ideal magnetohydrodynamics are constructed. The submodels are completed to involution, and partially integrated. The submodels specify Ovsyannikov vortex type motion or motion with homogeneous deformation in some spatial directions.Key words: ideal magnetohydrodynamics, partially invariant solutions, overdetermined systems of differential equations.Introduction. The notion of a partially invariant solution as a natural generalization of invariant solutions of differential equations was first proposed by Ovsyannikov [1,2]. The usefulness of this generalization is indicated by numerous examples of partially invariant solutions constructed for the equations of gas dynamics (see [3][4][5][6] and [7] and the references therein), hydrodynamics [8][9][10], the dynamics of a viscous heat-conducting gas [11], magnetohydrodynamics [12,13], plasticity equations [15,16], and the equations of other models of mechanics and physics [17][18][19]. In contrast to invariant submodels, partially invariant submodels are given by overdetermined systems of equations, which complicates their analysis but allows one to obtain classes of solutions with greater arbitrariness compared to invariant solutions.The general theory of partially invariant solutions of differential equations is set forth in [20]. The notion of the regularity of a partially invariant solution used in practice is introduced in [21]. An important property of partially invariant solutions is reducibility: in some cases, partially invariant solutions coincide with invariant solutions of the same rank. Finding the reduction of a solution is important since this eliminates need to perform the extra work of completing the equations of the submodel to involution. The known sufficient tests of reduction of some special classes of partially invariant solutions are given in [20,22].The notion of the hierarchy of partially invariant solutions was introduced in [23] to simplify and systematize the study of the set of partially invariant submodels of a given system of differential equations. The existence of the hierarchical structure reduces the construction of the set of all partially invariant submodels to the analysis of only irreducible submodels, from which all the remaining submodels are obtained by invariant reduction, which considerably simplifies the calculations.The present paper analyses the regular partially invariant solutions of the equations of ideal magnetohydrodynamics. The analysis is performed only for nonbarochronic submodels in which the pressure is a function of spatial coordinates. The set of barochronic submodels is supposed to be studied separately by analogy with the barochronic submodels in gas dynamics [24]. Eight types of irreducible submodels are identified. The equations of all submodels with one noninvariant function are completed to involution; the obtained equations of the submodel are simpler than the equations of the initial model. The fir...