Dear,

Editorial support team

Copernicus Publications

Referee report of the manuscript gi-2024-4 (Distance of flight of cosmic-ray

muons to study dynamics of the upper muosphere).

The paper presents the concept of muosphere as the region where a high concen-

tration of muons and its limit respectively. It describes muosphere/muopause

dynamics depending on crustal density (millennia time order) or isobaric surface

height variations. The author introduces the DoF (Distance of Flight) technique

for characterizing the muosphere based on measured data of the muon flux. The

paper describes in detail the modeling process and compares it with measured

data.

The technique is interesting but its application in a concrete problem isn’t ob-

vious. It’s important to extend this technique in a real scenario and contrast it

conceptually with techniques (like LIDAR) that can perform the same work. I

recommend publishing the paper after adding the modifications listed below.

line 49. The muosphere is defined from +10 km to -10 km, however in the

equation at line 55 the muosphere thickness is 3.5×104 m.

line 54. Typo in 1.6 × 102m−2s−1.

line 53. The estimated muon abundance is ∼ 8 × 1012 muons, however solving

the equation is ∼ 9.3 × 1012 muons. I recommend to put the equation out from

the text.

line 53. In the muon abundance equation a constant integral muon flux is used,

this flux is the one measured at sea level, but not the same underground where

the muon flux significantly decreases. Does it affect the abundance calculation?

line 72. The author establishes that study of muopause dynamics contribute to

the research field and mention some cases. Could you describe, in more detail,

how the parameterization of the muosphere/muopause can contribute?

line 95. Some reports on the study of barometric and temperature effects in

the muon flux are mentioned. The Pierre Auger Observatory has made stud-

ies on the influence of atmospheric pressure/temperature (using meteorological

balloons) in cosmic ray flux, it’s important to cite them. J. Blumer et al. Atmo-

spheric Profiles at the Southern Pierre Auger Observatory and their Relevance

to Air Shower Measurement. 2005.

line 102. The author set three major identified characteristics, but only A and

B are described, is there a C?

Figure 2. The scale of the muon flux variation is not clear in the panel A. Was

equation 1 obtained form panel-B plot on Figure 2?

Figure 3. It’s important to add error bars to the plots A and B due to they

are based on data.

Figure 4. The number label on the left of the blue line is missing.

Figure 5. It’s valuable to add the line legend to both plots. The plot description

is split into two different pages and it makes the figure reading difficult.

Figure 5. Why does the curve behave different at 90◦ zenith? isn’t expected

to follow the same trend than for the other zenith angles?

line 246. If the zenith angle is close to zero the equation diverges, so ”the

spherical curvature of the Earth has to be considered (for θ = 90◦)”. Does it

mean that the angle dependence is taken into account only for θ = 90◦?

Figure 6. Add error bars to plots contained in Figure 6.

line 270. The zenith-angle integration range was set to be 50◦ − 80◦. Why?

line 294. Typo, a dot is missing. (. Three PSDs ...)

line 295. In the apparatus description, the author says that between detection

layers two absorbing layers are set (10-cm thick lead block and a 3-cm thick

stainless-steel), if you have 10 cm of lead, is it necessary to have 3 cm of stainless-

steel? why?

line 296. Typo. ”10-cm thick lead block and a 3-cm thick stainless-steel with

a thickness of 3 cm”.

line 240. Write properly equation 2-2. It’s confusing.

Equation 2-2. What is the meaning of the constant 660? where does it come

from?

Equation 1. The relationship between atmospheric pressure and muon flux is

inverse, in that way, isn’t the slope of equation 1 negative?

Please find my review in the PDF file attached.

The paper proposes an original link between sea-level muon flux measurements and assessment on the atmosphere state's equation in a whole. It introduces a neologism "muosphere" defined as the part of the atmosphere + geosphere where muon flux is relevant, in a way which still not completely clear after the reading of the article, especially on the lower border (the geosphere one) since muons penetrate the Earth over distances depending on their incident energy. The article focuses on the "muopause" but I do not see much considerations on the underground probing of the geosphere. Please develop more on both borders of your "muosphere".

The main weakness of this article is that, apart from the invention of the term "muosphere", it does not propose innovative approaches on the use of muons fluxes o derive properties of the atmosphere. It has been published in the past that muons flux is correlated to barometric observables, stratospheric temperatures etc and be used to detect transient phenomena of abrupt changes in those parameters (e.g. SSW as mentionned but not cited in the article) or to anticipate violent phenomena such as storms.

TOF methods are also well documented and I would not focus the title of the article on this item.

The real originality of the paper is the use of cyclones for the calibration of the method. I would suggest to focus more on that point and try to implement a concept close to the one of "standard candles" used is cosmology with the supernovae for instance. Please try to elaborate on this item and provide more details on the analysis tools, goodness-of-fit, likelihood analysis to assess whether the results of this method may be reproducible. 

Best regards.