Were cosmic magnetic seed fields primordial or astrophysical?
In plain words
Dynamos in galaxies can amplify a weak magnetic field, but they need a starting seed. The seed could come from the early universe or from the first stars and galaxies.
Precise statement
Galaxies and clusters host fields of $\sim 10^{-6}$ G coherent over $\sim 10\,\mathrm{kpc}$, amplified by dynamos from seeds $B_{\mathrm{seed}}$. Identify the origin of the seeds: Biermann battery in the first collapsed structures ($\sim 10^{-20}$ G), inflationary magnetogenesis, or first-order phase transitions. An answer identifies the origin through the void field strength, coherence length and helicity, which differ between scenarios.
What would settle it
Measured strength, coherence length and helicity of void fields compared with the predictions of each scenario.
Problems built on this one
Special cases
- Do intergalactic magnetic fields carry net helicity? · open
- What is the magnetic field strength in cosmic voids? · open
Results
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