Modelling the radio and X-ray emission from T-Tauri flares

T-Tauri stars are known for their high levels of magnetic activity and variability. Both classical and weak-line T-Tauri stars are overluminous in the radio compared with the well-established Güdel-Benz relation between radio and X-ray luminosity for solar and main sequence stellar flares. We show that there is little difference in the observational properties of classical T-Tauri stars and weak-line T-Tauri stars. We then model a typical T-Tauri - circumstellar disc system magnetosphere to predict the radio emission from flares associated with the circumstellar disc and accretion events. We assume that energetic electrons are generated in a large-scale magnetic flux tube due to a reconnection event with the accretion disc field at 4 R. Our standard model, with a dipolar magnetic field with a strength of 2 kG at the stellar surface and non-thermal and thermal densities of 2.5 × 10¹¹ cm⁻³ and 5.0 × 10¹¹ cm⁻³ respectively, produces both X-ray and radio emission consistent with observations (logL_X = 30.5, logL_R = 16.3). Varying the model parameters, we can reproduce the observed range of radio and X-ray emission. The peak radio luminosity and the frequency of this peak (which occurs at >10 GHz and possibly beyond 100 GHz for some sets of parameters) depend on the fraction of non-thermal particles and may be used as a diagnostic of this quantity. The surface field strength was varied from 0.5 to 7 kG, with the peak flux increasing by over three orders of magnitude. The models provide a framework for constraining the properties of these sources and to guide and interpret future observations.