This paper establishes the existence and uniqueness, and also presents a specific blow-up criterion, for solutions of the generalized magnetohydrodynamics (GMHD) equations in Lei–Lin spaces $$\mathcal {X}^s(\mathbb {R}^3)$$ , by considering appropriate values for s. More precisely, if it is assumed that the initial data $$(u_0,b_0)$$ belong to $$\mathcal {X}^{s}(\mathbb {R}^3)$$ , we demonstrate that there exists an instant of time $$T>0$$ such that $$(u,b)\in [C_{T}(\mathcal {X}^s(\mathbb {R}^3))\cap L^1_{T}({\mathcal {X}}^{s+2\alpha }(\mathbb {R}^3))]\times [C_{T}(\mathcal {X}^s(\mathbb {R}^3))\cap L^1_{T}({\mathcal {X}}^{s+2\beta }(\mathbb {R}^3))]$$ , provided that $$\alpha ,\beta \in (\frac{1}{2},1]$$ and $$\max \big \{\frac{\alpha (1-2\beta )}{\beta },\frac{\beta (1-2\alpha )}{\alpha }\big \} \le s<0$$ (here $$\alpha $$ and $$\beta $$ are related to the fractional Laplacian that appears in the GMHD system). Furthermore, we prove that if $$T^*$$ (finite) is the first blow-up instant of the solution (u, b)(x, t), then $$ \lim _{t\nearrow T^*}\Vert (u,b)(t)\Vert _{\mathcal {X}^s(\mathbb {R}^3)}=\infty $$ , whether $$\max \big \{1-2\alpha ,1-2\beta ,\frac{\alpha (1-2\beta )}{\beta },\frac{\beta (1-2\alpha )}{\alpha }\big \}< s<0$$ and $$\alpha ,\beta \in (\frac{1}{2},1]$$ .
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