Synchrotron emission
Definition: Broadband radiation from relativistic charged particles accelerated transverse to a magnetic field.
Why it matters here: It is needed to answer If the magnetic field is four times stronger but the observed characteristic frequency is unchanged, how must gamma change? State the scaling and one assumption. and to interpret A power-law continuum is consistent with optically thin synchrotron emission, but spectral curvature can signal cooling or absorption.
Relationships: Use it with Polarization and Spectral index; the lecture model is \(\nu_c\simeq 4.2\times10^6 B_{\rm G}\gamma^2\ {\rm Hz}\).
Boundary or common confusion: The single-electron characteristic frequency ignores the broad synchrotron kernel, pitch-angle distribution, and self-absorption; a measured spectral peak is not automatically nu_c.
Spectral index
Definition: The exponent describing how flux density changes with observing frequency in a power-law spectrum.
Why it matters here: It is needed to answer If the magnetic field is four times stronger but the observed characteristic frequency is unchanged, how must gamma change? State the scaling and one assumption. and to interpret A power-law continuum is consistent with optically thin synchrotron emission, but spectral curvature can signal cooling or absorption.
Relationships: Use it with Synchrotron emission and Free-free emission; the lecture model is \(\nu_c\simeq 4.2\times10^6 B_{\rm G}\gamma^2\ {\rm Hz}\).
Boundary or common confusion: The single-electron characteristic frequency ignores the broad synchrotron kernel, pitch-angle distribution, and self-absorption; a measured spectral peak is not automatically nu_c.
Free-free emission
Definition: Thermal continuum produced when electrons accelerate in the Coulomb fields of ions.
Why it matters here: It is needed to answer If the magnetic field is four times stronger but the observed characteristic frequency is unchanged, how must gamma change? State the scaling and one assumption. and to interpret A power-law continuum is consistent with optically thin synchrotron emission, but spectral curvature can signal cooling or absorption.
Relationships: Use it with Spectral index and Brightness temperature; the lecture model is \(\nu_c\simeq 4.2\times10^6 B_{\rm G}\gamma^2\ {\rm Hz}\).
Boundary or common confusion: The single-electron characteristic frequency ignores the broad synchrotron kernel, pitch-angle distribution, and self-absorption; a measured spectral peak is not automatically nu_c.
Brightness temperature
Definition: The temperature a blackbody would need in the Rayleigh-Jeans limit to reproduce a measured specific intensity.
Why it matters here: It is needed to answer If the magnetic field is four times stronger but the observed characteristic frequency is unchanged, how must gamma change? State the scaling and one assumption. and to interpret A power-law continuum is consistent with optically thin synchrotron emission, but spectral curvature can signal cooling or absorption.
Relationships: Use it with Free-free emission and Polarization; the lecture model is \(\nu_c\simeq 4.2\times10^6 B_{\rm G}\gamma^2\ {\rm Hz}\).
Boundary or common confusion: The single-electron characteristic frequency ignores the broad synchrotron kernel, pitch-angle distribution, and self-absorption; a measured spectral peak is not automatically nu_c.
Polarization
Definition: The orientation and coherence state of the electric field, recorded through Stokes parameters.
Why it matters here: It is needed to answer If the magnetic field is four times stronger but the observed characteristic frequency is unchanged, how must gamma change? State the scaling and one assumption. and to interpret A power-law continuum is consistent with optically thin synchrotron emission, but spectral curvature can signal cooling or absorption.
Relationships: Use it with Brightness temperature and Synchrotron emission; the lecture model is \(\nu_c\simeq 4.2\times10^6 B_{\rm G}\gamma^2\ {\rm Hz}\).
Boundary or common confusion: The single-electron characteristic frequency ignores the broad synchrotron kernel, pitch-angle distribution, and self-absorption; a measured spectral peak is not automatically nu_c.