Thermal free–free radio emission
Electron–ion acceleration produces continuum emission without capture.
Key knowledge
Electron–ion acceleration produces continuum emission without capture. For nonrelativistic Maxwellian electrons in the radio limit hν≪k_BT, the emissivity scales as j_ν∝Z²nₑnᵢT^(−1/2)g_ff, with a frequency-dependent correction factor. A thermal particle distribution alone does not make an optically thin continuum a blackbody.
Values and equations
j_ν∝Z²nₑnᵢT^(−1/2)g_ff, for hν≪k_BT
- j_ν
- spectral emission coefficient per solid angle W m⁻³ Hz⁻¹ sr⁻¹
- Z,g_ff
- ion charge number and frequency-dependent correction factor 1
- nₑ,nᵢ
- electron and ionic number densities m⁻³
- T
- electron temperature K
- h
- Planck constant J s
- ν
- photon frequency Hz
- k_B
- Boltzmann constant J K⁻¹
Conditions and scope
- One ionic species, weakly coupled dilute gas and the stated low photon-energy limit; j_ν is power per volume, frequency and solid angle. Sum ionic contributions for a mixture. The proportionality supplies no universal numerical normalization.
- Transfer and optical depth affect the measured intensity; thermal electron velocities do not establish LTE ionization balance.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read the collision integral and Maxwell average. Retained its density and temperature scaling with the logarithmic correction represented by g_ff; omitted cgs normalization, approximate impact bounds and the source's reversed path sign for optical depth.
2026-10-10 · Independent AI editorial review: All44 exact root-authored compact records, equations/variable units/conditions and140 origin edges accepted after independently reading final6/18 with bounded primary bodies and matching prior38/122 scientific fingerprints unchanged. Exact claim/edge review is distinct from combined inventory scope and separate CLE26 approval; no entire cited books or old-corpus experimental revalidation is asserted. Receipt: cosmos-completion-independent-content-and-inventory-review.1.
Entry details
Permanent link to this entry ↗- Record identity
- uni-cosmos-thermal-free-free-emission
- Revision
- core.1
- Structured reference record
- University core expansion