General Comments

- Interesting approach, followed by an interesting and relevant discussion.

- I miss O+ also being cited in the Abstract.

Scientific Questions

- Line 27: Explain "stand-off distance", or change it to another word. This may not be obvious to non-native English speakers, like myself, and can cause confusion even within the field of research.

- Lines 89-90: "In deriving Equation 1, effects of generic similarities between time series (constant arrays), singularities, and absolute strength of the fields are also considered." > How are these effects considered exactly?

- Line 95: "The minimum accepted quality flag in LPW data is 50." > What does that mean, considering that the data never reached the density of 50 cm-3? What I interpreter from this is that the whole dataset should not be accepted? Or is it the opposite? Also, write the units after "50".

- Figure 1: Are you showing an example of electron depletion that is actually associated to regions of strong crustal magnetic fields? I can see from Panel a that the measurements of Bx and Bz are lower than the predicted (modeled) values. Probably the measured |B| will also be lower than the modeled |B|. How does that relate to your proximity parameter for this event? Is it considered high or low?

- Line 100: "down select": Do you mean you eliminate profiles with proximity parameter less than 5, or the opposite? "Down select" sounds ambiguous here, please use something like "eliminate", or rather "we select only", depending on what you mean.

- It would be interesting to see a map of crustal magnetic fields at Mars overlayed by the locations of the depletion events you analyse. I assume your proximity parameter could also catch events in the Northern hemisphere, far away from intense crustal fields.

- Figure 2: Are Br, Btheta and Bphi values that are measured by the spacecraft or values from the crustal magnetic field model?

- Figures 3 and 4: Please insert a scale bar next to the histograms showing number/probability of events. Right now, the histograms are only qualitative.

- Line 129/Figure 3: "depletions are found more likely around crustal magnetic fields pointing eastward". What is the physical explanation for that? Does it have to do with the preferential direction of the solar wind magnetic field, perhaps?

- Line 131/Figure 4: "(i.e., exiting the Martian surface)". Why do you think we do not see as many events for Br/|B| = -1, i.e., when the field is entering the surface?

- Line 161/Figure 6: "There is a shift towards higher O2+ variations with increase in ∆ne,s (the Colorbar)." What shift? Do you mean density variations of O2+ are larger than of O+? The sentence is confusing. Also, you say ∆ne,s but the colorbar shows ∆ne,c.

- Line 195: It lacks a sentence saying why we do not see even stronger variations in ion temperatures at altitudes higher than 400 km. Is it because the abundance of neutrals decreases? Or simply because there are not as many depletion events above 400 km?

Technical Corrections

The manuscript contains several typos. Please, carefully proofread it and fix them.

- Line 12: "crustal magnetic fields are..."

- Line 24: "~200 km"

- Line 27: "make"

- Line 54: "night"

- Line 54: (Cao et al., 2022) should be an inline citation.

- Line 72: " in Section 2"

- Line 79: "time series"

- Lines 78-79: "As such, we identified these events visually and when the density measurements exhibit sharp depletions both in timeseries and altitude profile data." > You identified the events both visually **and** when the density measurements exhibit sharp depletions? Is this correctly phrased?

- Lines 91, 93, 96: You write Panel (a), Panel b, Panel c, and Panel d. Please, be consistent.

- Line 94: "UTC"

- Figure 1: The texts of X, Y, Z, and hhmm are not corresponding to the label rows.

- Line 125: "Figure 3"

- Line 126: "... are shown below each plot."

- Line 144: "electron"

- Line 184: "ions and neutrals"

- Line 208: "due to"

- Line 209: "are listed"

- Line 230: "removes caused"?

The authors investigate how density depletions in the ionosphere of Mars are correlated with the crustal fields and show how said depletions might be connected to ion frictional heating. The paper is well written and presents different aspects of the topic taking advantage of the available MAVEN observations from several instruments. The authors define certain parameters which then use to quantify the correlation between the crustal fields and the ionospheric depletions and their connection to ion frictional heating. The plots are clear and help the reader to understand the main points of the paper. There are some parts in the paper though that need further clarification.