{
  "slug": "thermal-asperity",
  "term": "Thermal asperity",
  "aliases": [
    "thermal-asperity event"
  ],
  "definition": "A thermal asperity is a transient magnetoresistive read-signal disturbance caused by frictional heating during contact with a disk asperity or particle.",
  "note": "The sensor's temperature-dependent resistance can add a nonmagnetic disturbance to the readback signal [abatement]. This names the thermal signal event, not the surface bump itself.\n\nNon-contact baseline disturbance is different: changing head-disk clearance can change cooling of a biased sensor without frictional heating [heat-flux]. The CML follow-up models this with two-dimensional heat conduction and warns that neglected out-of-plane conduction may overestimate temperature [response].\n\nThe non-contact estimate on report 97016's printed page 14 compares about 0.008 ohm with a normal magnetic readback excursion of 0.5% of 30 ohms, or 0.15 ohm. This gives roughly 5% of that signal, not 5% of total sensor resistance. The abstract and conclusion instead give about 10%; no corrected value is asserted. This is not a contact-thermal-asperity amplitude [heat-flux].",
  "status": "unknown",
  "advantages": [],
  "limitations": [
    {
      "text": "These historical MR-head mechanisms do not provide a universal modern-drive amplitude, SMART diagnosis or fleet failure rate.",
      "citationIds": [
        "heat-flux",
        "response",
        "abatement"
      ]
    }
  ],
  "related": [
    "head-disk-interface",
    "flying-height",
    "giant-magnetoresistive-head",
    "touchdown-sensor"
  ],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "citations": [
    {
      "id": "abatement",
      "title": "Klaassen and van Peppen: Electronic abatement of thermal interference in (G)MR head output signals (1997), IBM author record; DOI 10.1109/20.617425",
      "url": "https://research.ibm.com/publications/electronic-abatement-of-thermal-interference-in-gmr-head-output-signals",
      "accessed": "2026-10-28"
    },
    {
      "id": "heat-flux",
      "title": "Zhang and Bogy: Variation of the Heat Flux between a Slider and the Air Bearing when the Slider Flies over an Asperity, CML report 97016, introduction and model",
      "url": "https://cml.berkeley.edu/wp-content/uploads/blue-reports/97016.pdf",
      "accessed": "2026-10-28"
    },
    {
      "id": "response",
      "title": "Zhang and Bogy: Temperature Response of a MR Head When It Flies over an Asperity, CML report 98001, sections 1, 5.2 and 6",
      "url": "https://cml.berkeley.edu/wp-content/uploads/blue-reports/98001.pdf",
      "accessed": "2026-10-28"
    },
    {
      "id": "analysis",
      "title": "Hesela: HDD mechanical faults, evidence and diagnostic limits",
      "url": "https://hesela.com/analyses/hdd-mechanical-failure-points/",
      "accessed": "2026-10-28"
    }
  ],
  "updated": "2026-10-28",
  "provenance": [
    "Source synthesis, not a new experiment. The CML model and discussion sections were checked beyond their abstracts; the IBM record supplies an author-hosted abstract, not full-text circuit verification."
  ]
}