Determine the origin of the suppressed cosmic-ray ionisation rate

Determine the physical origin of a cosmic-ray ionisation rate of approximately \(10^{-19}\,\mathrm{s}^{-1}\) in gas-rich debris disks around A-type stars, including whether stellar or disk winds can exclude cosmic rays efficiently enough to produce the value required by the primordial-remnant models.

Background

The models reproduce the observational upper limits on molecular-ion emission only when the cosmic-ray ionisation rate is strongly suppressed relative to the standard interstellar value. The authors show that attenuation by the disk wind column is insufficient, so another mechanism—such as modulation by magnetised stellar or disk winds—would be required. However, the magnetic activity of A-type stars and the efficiency of cosmic-ray exclusion in these systems are not established, making this a testable unresolved physical requirement of the primordial-remnant interpretation.

References

For gas-rich debris disks around A-type stars, however, the level of stellar magnetic activity and the efficiency of cosmic-ray exclusion are much less clear. The low value inferred here, $\zeta_{\rm CR}\sim10{-19}\,\mathrm{s}{-1}$, should therefore be regarded as a testable requirement of the present primordial-remnant interpretation, not as an established property of these systems.

— Thermochemical constraints on a primordial-origin of gas-rich debris disks  (2608.22781 - Mitani et al., 24 Aug 2026) in Section 4.2, “Implication for the cosmic-ray ionisation rate”