What drives episodic accretion in young low-mass stars ?

In this talk, I shall briefly outline the evidences of episodic accretion events in the early stages of young low-mass stars when they were still accreting gas from the protoplanetary discs. These short duration episodic accretion outbursts (FUors / EXors) significantly affect the pre-main sequence evolution of the star and planet formation. In the
main part of the talk, I shall present the insights we obtained on what drives these episodic outbursts from our long-term multi-wavelength observations of a very peculiar outburst source V899 Mon. V899 Mon underwent a short period break in its outburst in 2011, during which we could monitor the changes in accretion rate and mass outflow. Our recent high resolution spectrum from South African Telescope (SALT), shows interesting clumpy velocity structures in outflow. I shall present various quantitative estimates and results from our observations, and conclude with why we propose the break in outburst was caused by instabilities in magnetospheric accretion. The ongoing 3D radiative transfer modelling to model the physical and chemical evolution in these dynamic protoplanetary discs, which can be detected from ALMA, will also be discussed in the end.