  Mirror modes are ubiquitous in space plasma and grow from pressure
anisotropy. Together with other instabilities, they play a fundamental role in
constraining the free energy contained in the plasma. This study focuses on
mirror modes observed in the solar wind by Solar Orbiter for heliocentric
distances between 0.5 and 1 AU. Typically, mirror modes have timescales from
several to tens of seconds and are considered quasi-MHD structures. In the
solar wind, they also generally appear as isolated structures. However, in
certain conditions, prolonged and bursty trains of higher frequency mirror
modes are measured, which have been labeled previously as mirror mode storms.
At present, only a handful of existing studies have focused on mirror mode
storms, meaning that many open questions remain. In this study, Solar Orbiter
has been used to investigate several key aspects of mirror mode storms: their
dependence on heliocentric distance, association with local plasma properties,
temporal/spatial scale, amplitude, and connections with larger-scale solar wind
transients. The main results are that mirror mode storms often approach local
ion scales and can no longer be treated as quasi-MHD, thus breaking the
commonly used long-wavelength assumption. They are typically observed close to
current sheets and downstream of interplanetary shocks. The events were
observed during slow solar wind speeds and there was a tendency for higher
occurrence closer to the Sun. The occurrence is low, so they do not play a
fundamental role in regulating ambient solar wind but may play a larger role
inside transients.
