Review of "Helicity fluxes and Hemispheric helicity rule of active
regions emerging from the convection zone" by Pipin et al. (2025)

The authors use the mean-field mode of Pipin et al. (2023) to take account
of the twist released from active regions. The subject is interesting
and deserved to be published subject to additional clarifications.

1. For readers like myself who are not so familiar with the findings
of Pipin et al. (2023), it would be useful to clarify some questions
regarding their model. For example, to what extent do the BMRs correspond
to a fluctuating alpha effect with a finite average? Could this effect
alone produce a dynamo? Also, the idea that the *decay* of BMRs leads
to a dynamo effect is perplexing, so one wonders whether it is really
true and how it could be tested in future with simulations.

2. The paper seems to consider only one hemisphere. Do the authors use a
dipolar boundary condition at the equator? In principle, of course, also
quadrupolar solutions are possible and sometimes even easier to excite.

3. The relative magnetic helicity defined above Eq.(1) is problematic
because it is not additive; see
  https://ui.adsabs.harvard.edu/abs/2020A%26A...643A..26V/abstract
It would be good to address this and perhaps explicitly abandon its use,
if that was the intention. Also, it is not clear if it is related to
the H_R in Eqs.(3) and (4), where the non-script H_R does not seem to
be defined and unrelated to the script H_R, which is a volume integral.

4. Incidentally, the neglect of the vacuum permeability does not seem
to be mentioned.

5. It would be good to explain more clearly the role of magnetic helicity
of the large-scale and small-scale fields. Only the magnetic helicity
flux from the small-scale field is believed to alleviate catastrophic
(Rm-dependent) quenching.

6. In line 124, a particular helicity integral (script H, unrelated to
the earlier quantities) is introduced. It is not clear to me why it is
called heuristic. It is also defined as a volume integral and it would
be useful if one can compare it with the relative helicity introduced
earlier. Also, it is surprising that the right-hand side only contains
terms related to small-scale magnetic helicity fluxes. One would have
expected there to be also contributions from the large-scale field. Those
may be small, but a proper discussion would be useful. I don't see that
the considerations in Appendix A address this.

7. According to Bonanno (2016), as referred to in line 141, the harmonic
field representation outside the dynamo domain leads to radial sign
reversal of the magnetic helicity. Is that seen here too? It might be a
useful characteristic that would be worthwhile to compare with results
of observations and other numerical simulations.

8. In line 175, the authors talk about *the* initial helicity, but maybe
they mean *an* initial helicity. Does this discussion concern a finite
magnetic helicity only in one hemisphere?

9. Nowhere in this paper do I see a discussion about magnetic helicity
fluxes between hemispheres. This question is further obscured by the
fact that the volume integrals used in this paper do not clearly specify
which volume is meant. Also, earlier work considered magnetic helicity
densities that can vary in latitude rather than volume integrals.

10. In line 37, the authors talk about the 22-year variation of the
differential rotation. But those variations are quadratic in the magnetic
field, so their cycle should primarily be 11 years.