  We review the modulation stability of parallel propagating/field aligned
Whistler Mode Chorus waves propagating in a warm plasma from a formal
perspective with a focus on wave-particle interactions. The modulation
instability criteria is characterised by a curvature of the dispersion relation
for Whistler mode waves and a condition on the ratio between the group velocity
$c_g$ and the electron sound speed $c_{s,e}$. We also demonstrate the in order
to investigate the spatiotemporal evolution of the envelope and the formation
of packets, one necessarily needs to account for the motion of ions within the
system, leading to an ionic influence on the modulation instability threshold
determined by the ion fraction of the plasma. Finally, we demonstrate that
chirping may be captured when higher order effects are included within the
spatiotemporal evolution of the amplitude. This yields not only an explicit
expression for the sweep rate but identifies a possible origin for the power
band gap that occurs at half the electron gyrofrequency. Numerical validation
demonstrates that the interaction between wave packets is a source for the
emergence of tones observed within mission data, and such interactions may be a
major source of the electron energisation which Whistler-Mode chorus are
responsible for.
