  Phase space holes, double layers and other solitary electric field
structures, referred to as time domain structures (TDSs), often occur around
dipolarization fronts in the Earth's inner magnetosphere. They are considered
to be important because of their role in the dissipation of the injection
energy and their potential for significant particle scattering and
acceleration. Kinetic Alfv\'en waves are observed to be excited during
energetic particle injections, and are typically present in conjunction with
TDS observations. Despite the availability of a large number of spacecraft
observations, the origin of TDSs and their relation to kinetic Alfv\'en waves
remains poorly understood to date. Part of the difficulty arises from the vast
scale separations between kinetic Alfv\'en waves and TDSs. Here, we demonstrate
that TDSs can be excited by electrons in nonlinear Landau resonance with
kinetic Alfv\'en waves. These electrons get trapped by the parallel electric
field of kinetic Alfv\'en waves, form localized beam distributions, and
subsequently generate TDSs through beam instabilities. A big picture emerges as
follows: macroscale dipolarization fronts first transfer the ion flow (kinetic)
energy to kinetic Alfv\'en waves at intermediate scale, which further channel
the energy to TDSs at the microscale and eventually deposit the energy to the
thermal electrons in the form of heating. In this way, the ion flow energy
associated with dipolarization fronts is effectively dissipated in a cascade
from large to small scales in the inner magnetosphere.
