{"id":41702,"date":"2026-05-26T06:35:57","date_gmt":"2026-05-26T04:35:57","guid":{"rendered":"https:\/\/karmaka.de\/?p=41702"},"modified":"2026-05-26T06:35:58","modified_gmt":"2026-05-26T04:35:58","slug":"shock-wave-formation-in-the-thermosphere-by-an-earthgrazing-fireball-empirical-evidence-for-volatile-enhanced-hydrodynamic-shielding","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=41702","title":{"rendered":"Shock wave formation in the thermosphere by an earthgrazing fireball: Empirical evidence for volatile-enhanced hydrodynamic shielding"},"content":{"rendered":"\n<p>Elizabeth A. Silber, Denis Vida, Miro Ronac Giannone, Jamie Shepherd, Sarah Albert, Daniel C. Bowman, Tammy Do, Margaret Campbell-Brown, Peter Jenniskens, Reynold E. Silber<\/p>\n\n\n\n<p>Icarus<br>Available online 25 May 2026, 117184<\/p>\n\n\n\n<p><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0019103526002502\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>LINK<\/strong><\/a><\/p>\n\n\n\n<p>&#8220;Highlights<\/p>\n\n\n\n<ul>\n<li>First optical\u2013infrasound detection of thermospheric shock from an earthgrazer.<\/li>\n\n\n\n<li>Shock formation occurs at ~92\u202fkm under exceptionally low dynamic pressure.<\/li>\n\n\n\n<li>Volatile release amplifies hydrodynamic shielding in rarefied flow.&#8221;<\/li>\n<\/ul>\n\n\n\n<p class=\"justify-text\">&#8220;Hydrodynamic shielding is a theoretically well-established but observationally elusive and experimentally difficult-to-replicate phenomenon with implications that extend far beyond meteor physics. Rare earthgrazing meteoroids with infrasound signatures that penetrate to the ground can be used to probe hydrodynamic shielding that leads to strong shock formation at high altitude. Here, we report the first coordinated optical and multi-station infrasound observations of a centimeter-scale earthgrazing fireball that generated sustained cylindrical line shock at thermospheric altitudes near 92\u202fkm. The event was recorded by numerous optical stations and three infrasound arrays, allowing trajectory reconstruction, ablation behavior, acoustic source localization, and shock characteristics. Optical observations indicate early mechanical erosion and ablation\/evaporation at exceptionally low dynamic pressure, consistent with a cometary or a porous, volatile-bearing CM chondritic object. Independent infrasound detections localize shock generation to multiple points along a 164\u202fkm trajectory segment near perigee. Weak-shock modeling yields a consistent blast radius of ~30\u202fm, implying an acoustic-equivalent source size far exceeding the physical dimensions of the ~45\u202fg nucleus. We demonstrate that classical gas dynamics and ablation-driven hydrodynamic shielding alone cannot account for these observations under ambient thermospheric conditions. We show that volatile release provides the additional flow-field density enhancement required to amplify hydrodynamic shielding, reduce the effective local Knudsen number, and sustain a shock envelope capable of radiating detectable infrasound. These results demonstrate that small, volatile-rich meteoroids can transiently establish continuum-like flow in rarefied environments.&#8221;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Elizabeth A. Silber, Denis Vida, Miro Ronac Giannone, Jamie Shepherd, Sarah Albert, Daniel C. Bowman, Tammy Do, Margaret Campbell-Brown, Peter Jenniskens, Reynold E. Silber IcarusAvailable online 25 May 2026, 117184 LINK &#8220;Highlights &#8220;Hydrodynamic shielding is&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[96,97],"tags":[2762,934,3187,141,2351],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/41702"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=41702"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/41702\/revisions"}],"predecessor-version":[{"id":41703,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/41702\/revisions\/41703"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=41702"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=41702"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=41702"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}