  Collisionless shocks are ubiquitous structures throughout the universe. Shock
waves in space and astrophysical plasmas convert the energy of a fast-flowing
plasma to other forms of energy, including thermal and magnetic energies.
Plasma turbulence and high-amplitude electric and magnetic fluctuations are
necessary for effective energy conversion and particle acceleration. We survey
and characterize in-situ observations of reflected ions and magnetic field
amplification rates at quasi-perpendicular shocks under a wide range of
upstream conditions. We report magnetic amplification factors as high as 25
times the upstream magnetic field in our current dataset. Reflected ions
interacting with the incoming plasma create magnetic perturbations which cause
magnetic amplification in upstream and downstream regions of
quasi-perpendicular shocks. Our observations show that in general magnetic
amplification increases with the fraction of reflected ions, which itself
increases with Mach number. Both parameters plateau once full reflection is
reached. Magnetic amplification continuously increases with the inverse of the
magnetization parameter of the upstream plasma. We find that the extended foot
region upstream of shocks and nonlinear processes within that region are key
factors for intense magnetic amplification. Our observations at
non-relativistic shocks provide the first experimental evidence that below a
certain magnetization threshold, the magnetic amplification efficiency at
quasi-perpendicular shocks becomes comparable to that at the quasi-parallel
shocks.
