An apparatus comprises a write transducer, an energy source, and a controller. The write transducer is configured to write data to a magnetic recording medium, and the energy source is configured to heat the magnetic recording medium while it is being written to by the write transducer. The controller is coupled to the write transducer and configured to adjust at least an operating power of the energy source to selectably cause bits having variable bit aspect ratios to be written to the magnetic media.