English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

When the pressure of particles accelerated at shock waves is no longernegligible compared to the kinetic pressure of the gas, the linear theory ofdiffusive shock acceleration breaks down. This is expected in particular whenthe shock sweeps up preexisting cosmic rays, or when multiple shocksreaccelerate successively the same particles. To describe these systems, onehas to account for the nonlinear backreaction of the particles on themagnetohydrodynamic flow. Using an up-to-date semi-analytical model of particlereacceleration at nonlinear shocks, we show that the presence of prexistingenergetic particles strongly affects the shock profile, in such a way that thereacceleration of non thermal particles or the acceleration of particles fromthe thermal bath becomes less efficient. We further describe the evolution ofthe distribution of particles after several shocks and study the properties ofthe asymptotic solution. We detail the case of identical shocks as well as morerealistic scenarios, including the heating of the medium or superbubbleenvironments. When the particles are efficiently confined in the accelerationregion, it is generally found that the spectrum converges toward a concavesolution after a few tens of shocks, with a spectral index around 3.5 at thehighest energy. The postshock cosmic ray pressure reaches an asymptotic valueof about 4-5% of the ram pressure of one shock. Most of the shock pressure istransferred to escaping particles.

Nonlinear particle reacceleration by multiple shocks