AC06
Follow a radio pulse across the plasma
A radio flash arrives in a sweep of frequencies. Follow its passage through free electrons, derive the delay and polarization rotation, then repeat an analysis on measured CHIME intensity. The polarization chapter uses a separate synthetic Q/U experiment.
L1
Why low radio frequencies arrive late
Free electrons stretch a cosmic radio flash across time. Its sweep, tail and polarization carry different clues about the path.
L2
From electron motion to a radio delay
Derive the cold-plasma delay, calculate an electron column, and separate frequency dispersion from causal pulse scattering.
L3
Fit the rotating polarization vector
Derive a Q/U rotation fit, understand half-turn aliases, and integrate real frequency-channel responses before fitting.
L3
Replay a measured CHIME radio flash offline
Check the axes, masks and hash of FRB20180725A, compare residual dedispersion, and diagnose a fragile tail fit.
L4
Read a Faraday spectrum without turning it into a distance map
Read pinned RM-synthesis equations and figures, calculate band limits, and connect scattering and plasma-lens models to testable signatures.
Send a radio pulse through the screen
Sources and calculation scope
- Pandhi et al. (2024), CHIME/FRB polarimetry, arXiv v2
Version 2, 2 May 2024. Sections I.1, II.1–II.2: Stokes data, redshift weighting and calibration. The text of equation 2 lists kpc alongside coefficient 0.812; this course uses the dimensionally consistent pc normalization from NRAO.
- Cordes et al. (2017), Lensing of FRBs by plasma structures, arXiv v1
Version 1, 20 March 2017; Section 2, equations 1–4 and Figures 1–4. Read as a Gaussian-lens prediction; no lens inversion or source-mechanism inference is claimed.
- Condon & Ransom, Essential Radio Astronomy, Appendix D
D.1–D.2, equations D.14–D.27: cold-plasma group velocity and magnetic rotation. Consulted 28 October 2026. The text uses Gaussian units; the chapter derives the SI delay coefficient separately.
- Condon & Ransom, Essential Radio Astronomy, Chapter 6
Section 6.2, equations 6.44–6.46 and Figure 6.5: dispersion and pulse broadening. The inverse-fourth-power scattering law is a model choice here.
- CHIME/FRB first catalog data and waterfall documentation
The public FRB20180725A example distinguishes wfall from model_wfall. DOI 10.11570/21.0007, catalog version 210806.vFINAL; input range extraction and all array conventions are frozen in the companion provenance file. The historical time-unit label conflicts with the actual millisecond axis; the current tutorial and numerical sample spacing resolve it.
- CHIME/FRB official public-data tutorials
Current public-data products, processed intensity and millisecond time axis. Intensity products contain no Q/U. Public data-use statement requests the relevant CHIME citation; no explicit Creative Commons grant was located.
- Brentjens & de Bruyn (2005), Faraday Rotation Measure Synthesis, arXiv v2
Version 2, 2 November 2005. Sections 2, 4 and 6; equations 3–9 and 63–66. Read for Faraday depth, the transfer function, angle aliases and observing-band limits; this is a reading guide and a one-component numerical experiment, not a reproduction of the paper’s sky observations.
- Schnitzeler & Lee (2014), Rotation measure synthesis revisited, arXiv v1
Version 1, 5 November 2014. Section 2, equations 1–6, and Section 3: a finite frequency response differs from a rectangular response in wavelength squared. The simulation integrates rectangular frequency channels.
- Geyer & Karastergiou (2016), revisiting pulsar scattering
Section 2.1, equations 1–3: the one-sided exponential assumes an infinite isotropic thin screen with a Gaussian angular distribution. Finite and anisotropic screens alter the response.