We report the XMM- Newton observation of a large X-ray flare from the Herbig Ae star V892 Tau .
The apparent low mass companion of V892 Tau , V892 Tau NE , is unresolved by XMM- Newton .
Nevertheless there is compelling evidence from combined XMM- Newton and Chandra data that the origin of the flare is the Herbig Ae star V892 Tau .
During the flare the X-ray luminosity of V892 Tau increases by a factor of \sim 15 , while the temperature of the plasma increases from kT \simeq 1.5 keV to kT \simeq 8 keV .
From the scaling of the flare event , based on hydrodynamic modeling , we conclude that a 500 G magnetic field is needed in order to confine the plasma .
Under the assumptions that a dynamo mechanism is required to generate such a confining magnetic field and that surface convection is a necessary ingredient for a dynamo , our findings provide indirect evidence for the existence of a significant convection zone in the stellar envelope of Herbig Ae stars .