Magnetoviscous disc evolution and synthetic SEDs in T Tauri systems: A self-consistent 1D model

We present a self-consistent one-dimensional model for the coupled evolution of a Classical T Tauri star and its disc, integrating stellar mass, radius, and angular velocity together with the disc surface density over 10 Myr. The model combines viscous angular-momentum transport, a dipolar magnetic torque following Matt and Pudritz (2005, 2010), and pre-main-sequence Kelvin–Helmholtz contraction along a Hayashi track. The truncation radius R t emerges from the instantaneous balance between magnetic and ram pressure, allowing dynamical transitions between accretion, extended-coupling, and propeller regimes. From the resulting temperature profiles we compute multi-epoch synthetic SEDs. Spectral indices n 6 – 13 and n 13 – 31 trace an evolutionary sequence from Evolved Disc morphologies at t < 1 Myr toward Full-Disc classifications at t > 3 Myr, without entering the transitional-disc locus. A statistical comparison against 111 Class II sources in Orion A (Kim et al., 2016), performed on SEDs normalised to their mean logarithmic flux so as to probe shape rather than absolute level, yields 41 high-fidelity matches ( r > 0.7 , RMS below the first quartile), of which 71% are reproduced by evolved models ( t ≥ 3 Myr). These sources accrete at 1 – 5 × 1 0 − 9 M ⊙ yr − 1 through magnetospheres truncated at R t = 7.3 – 8.7 R ⊙ , and are consistent with surface dipolar fields of several hundred gauss to a few kilogauss; the field-free case is excluded by the stellar rotational evolution. Since the grid uses a single stellar mass, the matching constrains the evolutionary state of the disc rather than its age alone. The solver is verified against the analytic Lynden-Bell & Pringle solution and conserves global mass to better than 1 0 − 4 . These results establish a magnetoviscous baseline against which additional dispersal physics can be isolated, and provide initial conditions for radiative-transfer models. The absence of transitional-disc morphologies confirms that inner-cavity formation requires processes beyond continuous magnetoviscous dispersal.