The fate of self-aligned rolls in gravity modulated magnetoconvection

Highlights: • Gravity modulation affects thermal convection with horizontal magnetic field. • Chandrasekhar number does not affect the stability boundaries. • Oscillatory two dimensional convective rolls are found at onset. • The rolls align themselves along the magnetic field direction. • The system destabilizes and attains chaotic state soon above onset. -- Abstract: We explore the modifications brought about by gravity modulation in self-aligned two-dimensional (2D) stationary rolls and higher-order convective instabilities with horizontal magnetic field. The Chandrasekhar number plays no role in determining critical values of the forcing parameters for convection to begin. The onset is in the form of 2D rolls with periodically varying intensity. The external magnetic field is solely responsible for aligning the rolls while the induced magnetic field comes into play after three-dimensional convection sets in. Gravity modulation destabilizes the system and results in chaotic flow much earlier above onset.