  Magnetic holes (MHs) are coherent magnetic field dips whose size ranges from
fluid to kinetic scale, ubiquitously observed in the heliosphere and in
planetary environments. Despite the longstanding effort in interpreting the
abundance of observations, the origin and properties of MHs are still debated.
In this letter, we investigate the interplay between plasma turbulence and MHs,
using a 2D hybrid simulation initialized with solar wind parameters. We show
that fully developed turbulence exhibits localized elongated magnetic
depressions, whose properties are consistent with linear MHs frequently
encountered in space. The observed MHs develop self-consistently from the
initial magnetic field perturbations, by trapping hot ions with large pitch
angles. Ion trapping produces an enhanced perpendicular temperature anysotropy
that makes MHs stable for hundreds of ion gyroperiods, despite the surrounding
turbulence. We introduce a new quantity, based on local magnetic field and ion
temperature values, to measure the efficiency of ion trapping, with potential
applications to the detection of MHs in satellite measurements. We complement
this method by analyzing the ion velocity distribution functions inside MHs.
Our diagnostics reveal the presence of trapped gyrotropic ion populations,
whose velocity distribution is consistent with a loss cone, as expected for the
motion of particles inside a magnetic mirror. Our results have potential
implications for the theoretical and numerical modelling of MHs.
