Radio streaks in the Lighthouse Nebula discovered with MeerKAT. Particles escaping from the tail and illuminating the ambient magnetic field

Bow-shock pulsar wind nebulae are valuable sources for investigating the dynamics of relativistic pulsar winds and the mechanisms by which they produce cosmic-ray leptons at the highest energies. The Lighthouse Nebula is one such object, famous for the high velocity of its pulsar and its long, misaligned X-ray jet, which may provide a specific escape channel for the most energetic particles. We aim to understand how the bulk of non-thermal particles is released into the interstellar medium. We focus on gigahertz radio observations, which probe lower-energy particles that are dominant in number and long-lived, thus providing a picture of how escape proceeds over long timescales. We analysed MeerKAT and ASKAP observations at 1.28 and 0.94 respectively. MeerKAT observations reveal a highly structured synchrotron nebula downstream of the pulsar PSR J1101--6101. A cometary tail extends beyond 5 from the pulsar, while we detect multiple two-sided transverse emission streaks for the first time. We detect no radio counterpart of the misaligned X-ray jet, but the spectral index map shows an apparent asymmetry, with the steepest values near the base of the jet. We interpret the radio streaks as the occasional, charge-independent release of energetic leptons from the tail into the surrounding medium, resulting from dynamical instabilities and reconfiguration in the downstream flow. Most of the particle content of the nebula is discharged into the ambient medium within several parsecs. Escaped particles light up the ambient magnetic field, which appears to have a coherence length of at least a few parsecs. The length and persistence of the streaks indicate a low level of magnetic turbulence, possibly slightly enhanced with respect to average cosmic-ray transport conditions in the Galaxy. This may result from self-generated turbulence caused by a resonant streaming instability or from past activity of the progenitor star.