{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"a9c4741ea7d8ab9133c8a24bce3b0a6f3e000bb89c2fd61e81ac62d6617050b5","created":"2026-10-03T07:18:08Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"8b33cdd72f7fb5e477a020b1f6a1b41bb768355803da48dc8508dec557175c97","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"plasma.reconnection.coronal-sheet-onset","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Before a solar flare, a sheet of electric current in the Sun's atmosphere slowly thins while it stores magnetic energy. Theory suggests the sheet breaks up once it is thin enough compared with its length, but the threshold and timing for a sheet that is still forming are not established.","posed_since":"","precise":"For a current sheet of length $L$ and thickness a forming under external driving in resistive or Hall MHD at Lundquist number $S = L v_A/\\eta$ of 1e12 to 1e14 (solar corona), determine the aspect ratio $a/L$ and the time at which tearing growth outpaces sheet thinning and fast (plasmoid-mediated or collisionless) reconnection begins; the ideal-tearing proposal gives $a/L \\sim S^{-1/3}$. Determine how the criterion depends on the thinning rate and on the approach to kinetic scales ($a \\sim d_i$), and predict the stored magnetic energy at onset. An answer is a criterion confirmed by driven-sheet simulations over a range of $S$ and consistent with flare-onset observations.","problem_ref":null,"references":"","settled_by":"Driven-sheet MHD and kinetic simulations over a range of S that confirm the predicted onset aspect ratio and time, with a laboratory test at the highest attainable S.","status_note":"The ideal-tearing criterion was proposed by Pucci and Velli (ApJ Letters 780, L19, https://doi.org/10.1088/2041-8205/780/2/l19); its validity for dynamically forming sheets and in observations is not established.","title":"Onset of fast reconnection in forming coronal current sheets","topic_ref":"c1057caf785ec309864fe9c3911636cf72981d9ad70fccb8c56b4c4d20d44a4f"},"content_withheld":"false","files":[],"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"7caf31dd4e833bb5953affd9f4678352fa3560a5aaca2cff9e822a7375b7eba9","schema":"pubphys.attested/1"},"id_token":null,"id_token_withheld":"false","envelope":{"attested_hash":"1590e876760c76bef9a3fc02f58902a83ab09f0fcc537973f73d34024989b5d9","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"ua2OtEeztUf0eiCmhSiRNG95jt4e_bpyiouaYm0vc3TiDTfxt6gN0Kja0jY82E-QXXVq_SEaDiVmjHc2_dQzAg"},"schema":"pubphys.envelope/1"},"ots":{"attested":["AE9wZW5UaW1lc3RhbXBzAABQcm9vZgC_ieLohOiSlAEIFZDodnYMdr75o_wC9YkCqDqwnw_MU3lz9z00AkmJtdnxIBVxp1XFr_vY6JG-1GRrc8ZoOrB5oR7DhEhfDE2cNRXFCPAgB9fUPyoLZlw3WSAbne4aEdUH3KBgcqbuCmqyVGKBj2oI8SDhBTb-BYAeFzAt-wpjEie9WxI9HcQAuYN-foLC2zAaBwjwIMVSwSEtVM3bh1YueKCASD6MMru70hmuNJNcxhETCKgBCPAg-rKQ-ADXHexHJ3hYMOIN3ezjrp6eYRGfrXztxk6MTmgI8SBI5WWS1t7Z8flsvGBE5Hb8T0f8W517Pp3rLy_9wzKg9wjxIOW1ns_c0c5c2jYSiKKGb0P9jWELAq018HKkhPTXz3YCCPAg4duurmZDAdfNGsSTw9mNvFYpVAY2z2S-jm5XHnSBx-UI8SByOXFSMcZPx-OI54voF1A1KoKCW2ZGWFJKc0hkOGWyGQjwIMIc4xq7iJ2YP27EtWYUvEm4-TQD7cayDq2XvZh74n3BCPAg3v2QXfNkDO6Xzu9061umH0rhjRfHBKza3uG2nPQbpd8I8CCtNZgmApuKULvPC9nsMCaM05arV-F3o5FTlnJCnRvdMgjwIBGYo5Vxy-d7U5zKv5vp3Ii7hJPH_BDLCzA13c47p9q7CP_wCHbghVgOFMuNCPAQPZK2lHbTMqcCYUotzOQcmQjwIJ7ruRIs6HnufKxCpmLUgeUl0aUu0ov4_3PqcppS-bddCPEgI530vHzdwz_3o9jYQ3WablSaV64Wfn7Pmby5WLyI-A0I8QRqwKw78AhITF7Tr3a1xP8Ag9_jDS75DI4sK2h0dHBzOi8vYm9iLmJ0Yy5jYWxlbmRhci5vcGVudGltZXN0YW1wcy5vcmcI8CBXWeNiWFWltfHE0nkDXsVKIykUUwuObhsnN-2fvBt98gjwIM5Vf7j68sOFgVysYMc5S09Hho-fqxYW3oQ4oKUX7JpPCPAgaKHHQB3sdd9w1hu4NMh7vmb-p0X2r4uyVKKCj1G7S28I8SAW2Mg6Bzi9ygjrrjIYB7w90fwMcxH24SsqLmzPyAMGfwjwIMQ863zlveYIpNKWVrZaDOa4vowwoOg2CcTW8gXtxK3dCPEgrZxGGAf-t8jhz_eLMUyBN1IhNrdYDRcNHWvQcwNG9woI8CCVOUHG1YXudbaFIgUYvrCIevRWvb2ubhQAo-z0duD0rQjxIDBeKerVGkO3J2eXDwdraSioXbIWsdIPEN1s8pIwJIS2CPAgV2kB3n3JZ5HwBQjpRL1CWKnqvdCjZk3RcALk6N2wHigI8CB-wbljNlfqElD25uZkNg6taS81YDRU2vfMqGVQ420O9AjxWQEAAAABJM43UU6MLMRrPlCUqossvu1q_knons5yylyWTgxZzWUAAAAAAP7___8CLgABAAAAAAAWABQrYt3E7OllKRCEmL3FL589l78_5wAAAAAAAAAAImog8ATiyw4ACAjxILmbcIO7ixv3pCtwUMZ1VQGKus54F9lZ8-w5ECD5ZuiICAjwIG6ynCyFTLPE7Rgk-0ZGCtBDyqNQx8YvaSZNHy8D8p8jCAjwIMX8zoD2Be1YWvcx_bexVPRmBX0hK-do8b8t9SarimQVCAjxIG6XtpqIEclLlhzcK1LVjqoPGrjjmLnyno8tcETMzECECAjwIF6mlfXOFY51JhrK4eze8zQlKV75OYZYqbtyi8BWxmAsCAjwIKKUcJmVoz-u-geiRV_-ZHdF0VEPXaEPFWf_JX_0e7G2CAjxIGMeD0Z5QWNKBcAEpHht007FFIILW6aSJ8f3CMkKNsneCAjwIBFr6Je8rkB7kwhPGbq0yRgFwZsvW9JhY5sXDRtrq0QwCAjwIAHAwXaus-yUgKICJB5mVvx8VZuJgjwnpb0qWPg1pi6DCAjxIAJhb8cefkVHTAMymdsxa-_i-tUua62LcpALQnPG7R9_CAjwIDvsFqBhPfAL6TCtXZd7gBWmMpx6iiZ-Ug0Jf_LlcstgCAjwIDJRBX6Q0Vge-ra-k1_g76yJWTEp6WWF13I3JpTnsZPJCAjwILykZCbkC9VQgl5gytPKKir6T9nTvKR6y05iWSHBTQgzCAgABYiWDXPXGQED45c78Ah-sGbmQAwfZwjwEAYqxtHnZiPZnJEGPx_JvKsI8SDXkqDg17YsZIrEz5acRx7mBXCKW5mKNgRYnw_-U2cpDgjxBGrArDrwCEfK6Mono428_wCD3-MNLvkMji4taHR0cHM6Ly9hbGljZS5idGMuY2FsZW5kYXIub3BlbnRpbWVzdGFtcHMub3JnCPAg10nyJ6Jn4kshQQQCKE0Lvj3hBC6nLRBVIzaPV4eh8VwI8CCQaAqWlxEbac_XOq1MOlf9iOKHEsxXspzbjK0vLpy8BwjwII3iRbRXUcDxrhAdkZmFlI15nySCSEZ7g922tF1Xln5DCPEgYYvZ1L4v4rPu_UqLfcHPtwSb2OH2GhPgVcVhhH6DpkQI8CDZCIoR20sC-uchP40oAmcLm9EJFV7xzwplj54AeVadXQjxILvLBjPFpCoz29m9Yf2qRnV7PI9GqxE8ozVQfk9QwCqrCPEgZXcMudvEoB_MJ8tqOW2PLTKAIeQBnE-1bfzptRc2gR8I8VkBAAAAAfXq-bmxWqOz7B5wKkwjzHGv2R4s7Y0Z76LqXWYNhmz0AAAAAAD-____Av0cAAAAAAAAFgAUl-skmdZDtn7Hnub6mF4HP2uVn7oAAAAAAAAAACJqIPAE4MsOAAgI8CBDmQsbEXc46Hu8DivhCBM1LGExa4TTM-wo7HpoCVjBTQgI8CCty5vkQtPHzzs8xqArOYhVSjgaDoG1ou3cojv5_P7wQQgI8SDQWB0kdXCTwbk-TqTt0QfRMyzDNLOtU1XXFgvGSRlW8wgI8CC2PKa_QCIBZtrXodq1GdEzppISMsMRDOnzr2gFjLKOAAgI8CCwQ_QF67bcFk_uJ2s0VCZmf5PGIjTmTCpt_qnVY5p_8AgI8SAbzyx7z-oxPMju6PvtQhzrJIQyH2ZAc9oyLuYemzbmZQgI8CC5bh7J74uUk91r8LwybHQFCNBC3PWeuwtMCCNFKWj19AgI8SAf4R2TUNPjaX_PWDUImpoITK0JoW89zaMKnD1wlEEi8AgI8SC2vNmdm7eyP5Ytl1yTzT0njliMdALl1ViKG-s3bG2zswgI8CCpbIVNz1GFVXdJk2zd82hBUoNFFemUPBt7IJdWEOciPwgI8CBtYdRQcrtX1FtCm1SxF7sx-5cO04U8KzbJh8fqBkyReAgI8CBHs2LGmX6gI-lV7yp1RrV7_tGfdiBAwnEFF6B6yXHzAQgI8CATotVmbXBMAixhZ-QKy5Q4lR0FusdA_wcIC1TbB7GmxAgIAAWIlg1z1xkBA-KXOw"],"envelope":["AE9wZW5UaW1lc3RhbXBzAABQcm9vZgC_ieLohOiSlAEI1_bGwXB-6TEDkljyPBhtweOhdHci75BmaV69sDeHyYLwINgF-qKJhMQ97t-qv1HRtUWESZSmwo83EOLkj87nOvXSCPAgno5hi5BHjd_o5ZoPr1_pc0jVr-MlOzR2WPDUnDD7h7AI8CD6UZxAJ6tAvcoffpyipRnXT-8cBuaUI8q6w2tD4VYNlQjxIDlDxyPHNnslGe9Vj0mV6H1CBphZBRvZjHF4VEMDftgPCPEgK4fuQK4aQoh5Cj9RDxqmXmWyYEFceURv3fAh3LkoiaUI8SBgGNyCCe7fneNHZYRnLtMmZubs2ZqE324uZJhHU18E5AjxIKisLLidrc4SayDttFWU91CK6Y9jXXvkqUwRG8TFKZFnCPEgrtdg06P_PiGLrXxo5MKrwKoHRBN3RJolGSIc0ZD_7wsI8SDw6LQ-RfhPE_v83K9oKkOzbHhdxc-f1_76FJQHtj9gCwjwIG_qk_muz-jg8UolhZs34aKKg3vvCTOQfEn-hyT2gbIDCPEgUZCxxJx-baWw4JFRfzCCtSjPn4ATBx_3FQi1O2Yo4-8I8SAQuuTPkAGyvS_wKMy9BtKvnki2puESdY2vXem8hT1uIQjwIBGYo5Vxy-d7U5zKv5vp3Ii7hJPH_BDLCzA13c47p9q7CP_wCHbghVgOFMuNCPAQPZK2lHbTMqcCYUotzOQcmQjwIJ7ruRIs6HnufKxCpmLUgeUl0aUu0ov4_3PqcppS-bddCPEgI530vHzdwz_3o9jYQ3WablSaV64Wf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