# The collisionless hydrodynamics: On the nonexistence of collisionless shocks

Source: [The collisionless hydrodynamics: On the nonexistence of collisionless shocks](<https://www.sota2.com/research/paper/68fa49241e209131ce934e8f>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-25T07:11:36.738Z

Authors: Andrei Gruzinov

Published: 2025-01-28T23:26:02.000Z

## Abstract

Collisionless shocks, essential for astrophysics, perhaps do not exist as statistically stationary solutions. If so, any quantitative statement about a collisionless shock should be qualified by the age of the shock.   A theoretical description of the upstream of the 1+1 dimensional electrostatic collisionless shock is developed -- collisionless hydrodynamics. Peculiarities of collisionless hydrodynamics prevent a shock formation when a piston is driven into cold plasma. An exact self-similar solution is found instead; the spatial extent of the solution grows linearly in time.   Direct numerical simulations of plasma kinetics in 1+1 dimensions confirm the hydrodynamic result -- a statistically steady collisionless shock doesn't exist. Instead, at each fixed time, there is a continuous succession in space of marginally stable velocity distribution functions. The spatial support of this continuous succession grows linearly in time.

## Recorded benchmark results

A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage.

## Original sources and implementation

[Original paper](<https://arxiv.org/abs/2501.17341>)

[PDF](<https://arxiv.org/pdf/2501.17341.pdf>)