{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"6085e7aa2e2f48824f1236ce0f1e8cd26686f3b5ea9bb9597c721dce96ed9e11","created":"2026-10-03T07:18:08Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"c8dd48ea15dcb9649c5856d8001fed43aecf963fc1f7ec2a5e1342deae4cc274","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"plasma.exb-low-temperature.bohm-diffusion-origin","kind":"phenomenon","literature_status":"open","n":"1","parents":[],"plain":"Since the 1940s, many magnetized gas discharges have been found to leak particles across the field at a rate falling only as one over the field strength, far faster than collisions explain. Why this simple scaling appears in so many devices has no accepted explanation.","posed_since":"1949","precise":"Cross-field diffusion in many magnetized low-temperature plasmas follows the Bohm form $D_{B} = c T_{e}/(16 e B)$ ($T_{e}$ in erg), scaling as $1/B$ rather than the classical $1/B^{2}$. Determine whether a common mechanism (E x B drift-wave turbulence, sheath-coupled instabilities, gradient-drift or Simon-Hoh modes) produces this scaling, the origin of the coefficient near 1/16, and the conditions where it fails. An answer is a theory predicting $D_{\\mathrm{perp}}$ versus $B, T_{e}$ and geometry, validated across at least two device classes.","problem_ref":null,"references":"","settled_by":"Kinetic simulations and measurements in two device classes (e.g. Penning discharges and Hall thrusters) agreeing on $D_{\\mathrm{perp}}(B, T_{\\mathrm{e}})$ and its departures from Bohm scaling.","status_note":"","title":"Why magnetized discharges often show Bohm-scaled cross-field diffusion","topic_ref":"0df27ef69105e55adf69d4d0c5a12981d908dd6ae2aae29332a8515dac4c6272"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"294f95a2aea606a2358055e507a9d41cbd9fdd435b853b586c0b88e10abc0dfd","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"c59f35dc966b83dbc991f01ffb63c62fc0dc93e7f97de0aef09af6561b210ae1","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"l4mbjC7U2VQwcrvJs6qXLQaVxQlwoX6qjUZIIkyE3LPMEYVpG1OEP69rGScPGPVisDCPNr9yl6tQ8cIsbGh6Bg"},"schema":"pubphys.envelope/1"},"record_hash":"294f95a2aea606a2358055e507a9d41cbd9fdd435b853b586c0b88e10abc0dfd","leaf_index":1837}