{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,24]],"date-time":"2026-02-24T13:22:13Z","timestamp":1771939333931,"version":"3.50.1"},"reference-count":30,"publisher":"AIP Publishing","issue":"2","license":[{"start":{"date-parts":[[2026,2,24]],"date-time":"2026-02-24T00:00:00Z","timestamp":1771891200000},"content-version":"vor","delay-in-days":23,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003329","name":"Ministerio de Econom\u00eda y Competitividad","doi-asserted-by":"publisher","award":["PID2021-127322OB-I00"],"award-info":[{"award-number":["PID2021-127322OB-I00"]}],"id":[{"id":"10.13039\/501100003329","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003329","name":"Ministerio de Econom\u00eda y Competitividad","doi-asserted-by":"publisher","award":["PID2024-157933OA-I00"],"award-info":[{"award-number":["PID2024-157933OA-I00"]}],"id":[{"id":"10.13039\/501100003329","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["pubs.aip.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2026,2,1]]},"abstract":"<jats:p>Shock waves in plasma can be characterized according to the physical mechanisms behind their formation. When collisions are frequent, shock dissipation is mainly binary-collision driven, and the shock width (SW) is often comparable to a few mean-free-paths. In contrast, collisionless shocks rely on collective plasma processes to establish dissipation on scales far below the mean-free-path. The purpose of this study is to bridge these two regimes. Here, we present simulations using the OSIRIS particle-in-cell code with the Coulomb collision module to explore the gradual transition between collisional and collisionless shocks by varying plasma parameters that determine collisionality. We show a smooth transition of the SW in the intermediate region, where the ion plasma parameter is ND\u22481. Our numerical results confirm earlier theoretical predictions from existing theories in the asymptotic regimes, where the Mott\u2013Smith ansatz, combined with a full Bhatnagar\u2013Gross\u2013Krook (BGK) collision operator, was used to obtain the collisional-regime SW, while the classical Tidman formalism describes the collisionless limit. We demonstrate that the ion plasma parameter provides a useful metric for identifying when shocks transition from a fluid-like, mean-free-path scale to a collisionless, sub-mean-free-path scale. We discuss the importance of our results in astrophysical environments, where shock breakout causes a transition in the SW and marks the beginning of the acceleration of particles to high energies.<\/jats:p>","DOI":"10.1063\/5.0294460","type":"journal-article","created":{"date-parts":[[2026,2,24]],"date-time":"2026-02-24T12:48:58Z","timestamp":1771937338000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Bridging the gap between collisional and collisionless plasma shocks: A simulation study using OSIRIS"],"prefix":"10.1063","volume":"33","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-0595-3273","authenticated-orcid":false,"given":"Yossef Nissim","family":"Kindi","sequence":"first","affiliation":[{"name":"Bar Ilan University 1 , Ramat Gan 5290002,","place":["Israel"]}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8667-0889","authenticated-orcid":false,"given":"Asaf","family":"Pe'er","sequence":"additional","affiliation":[{"name":"Bar Ilan University 1 , Ramat Gan 5290002,","place":["Israel"]}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2030-0046","authenticated-orcid":false,"given":"Antoine","family":"Bret","sequence":"additional","affiliation":[{"name":"ETSI Industriales, Universidad de Castilla-La Mancha 2 , 13071 Ciudad Real,","place":["Spain"]},{"name":"Instituto de Investigaciones Energ\u00e9ticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real 3 , 13071 Ciudad Real,","place":["Spain"]}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2906-924X","authenticated-orcid":false,"given":"Lu\u00eds O.","family":"Silva","sequence":"additional","affiliation":[{"name":"GoLP\/Instituto de Plasmas e Fus\u00e3o Nuclear, Instituto Superior T\u00e9cnico, Universidade de Lisboa 4 , 1049-001 Lisbon,","place":["Portugal"]}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7644-7381","authenticated-orcid":false,"given":"Kevin M.","family":"Schoeffler","sequence":"additional","affiliation":[{"name":"GoLP\/Instituto de Plasmas e Fus\u00e3o Nuclear, Instituto Superior T\u00e9cnico, Universidade de Lisboa 4 , 1049-001 Lisbon,","place":["Portugal"]},{"name":"Institut f\u00fcr Theoretische Physik, Ruhr-Universit\u00e4t Bochum 5 , D-44780 Bochum,","place":["Germany"]}]}],"member":"317","published-online":{"date-parts":[[2026,2,24]]},"reference":[{"key":"2026022407485382200_c1","volume-title":"Physics of Shock Waves and High-Temperature Hydrodynamic Phenomena","year":"2002"},{"key":"2026022407485382200_c2","article-title":"Course of theoretical physics","volume-title":"Fluid Mechanics","year":"1987","edition":"2"},{"key":"2026022407485382200_c3","doi-asserted-by":"publisher","first-page":"S3","DOI":"10.1063\/1.1711088","volume":"7","year":"1964","journal-title":"Phys. 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