First, we would like to thank the reviewer for the comments and suggestions which we think improved

the quality of the paper. Below we address all comments and concerns that were raised. The reviewer’s

comment is reiterated after the line number on which it occurred, and followed by our answer in italic.

Line 35: ”To make a measurement of the absolute electron density with any ISR an independent

measurement is required.” - Rephrase?

We have rephrased those sentences slightly so that it is clearer.

Line 35: ”...plasmaline...” - two words?

Fixed for all instances of the word.

Line 90: 3 TYPOs

Fixed.

Line 105: ”...a magic constant ...” - I have not seen the Deathly Hallows symbol used for this stuff

before. Although I think it is important to have fun as a scientist, as a reviewer I want to point out

that this symbol is not easy to reproduce, which may cause some frustrations with colleagues and in

future works.

We have now changed the symbol for the magic consonant to Υ, a standard Greek letter.

Line 115:  Equation - Should this be N hat?

The hat in this case is just meant to indicate that this is an estimation now. That is the uncertainty,

η is now on the other side and included in the calculations.

Line 155: ”Calculating the mean at each beam of all timesteps in the period between the blue vertical

lines gives the Flatfield density measurement at this altitude.” - Why did you pick this time? There

appears to be a density irregularity here.

We interpret the data in this timeslot as a gradient in the overall density, not an irregularity. This

becomes more apparent when looking at Figure 5, which shows the whole time series of a little more

than 3 days of data for that experiment. In this figure we can see that the selected timeslot is at

the beginning of the second day, that is when the ionospheric plasma density increases due to solar

radiation. Another indicator that this can be interpreted as a gradual increase of plasma density in

the polar ionosphere rather than a local density irregularity is that the increase happens simultane-

ously at all beams. In Figure 1, just prior to the highlighted timeslot starting around 06:00 UT in

the southernmost beam (bottom of the plot), there is a density increase that we do interpret as an

irregularity passing through the entire field of view of the radar. This increase in density appears in

all beams within the following hour, starting with the southernmost magnetic latitudes and gradually

moving toward magnetic north. We have added three sentences in the manuscript to clarify this.

Line 155 / Figure 1: Are all 19 beams being used, or is this a North-South slice through the radar

field of view?

This plot shows all 19 beams (38 in total) for each radar, arranged by the magnetic latitude of their

individual pointing direction. This is described in the text and caption.

Line 165: You should check with the RISR PIs. I was certain that any value under 1e10 m-3 was an

error.

Also, I m3 should be m−3

The reviewer is correct and it is specified in the text that this value corresponds to the approximate

lowest value that the ISR can measure. So our Darkfield differs from a traditional darkfield measure-

ment in that we can not actually measure it. In our method, it is a baseline subtraction to remove

outliers. We have added a sentence to the text to make this clearer.

Line 175: It should be noted that the AMISR beam numbers presented here correspond only to this

specific experiment and were assigned here to aid in discussion only. The actual look direction of a

given beam number may change from experiment to experiment. While each of the nearly 4000 beams

for each of RISR-C and RISR-N has a fixed number which are used by the radar operators, they are

typically not meaningful for discussing individual experiments. For each experiment, the actual look

directions of a given beam are available in the corresponding data files. -

Could be shortened.

Fixed.

Line 180: Figure 3 - The title of the figure sounds like you are talking about one beam over the span

of multiple days. Is this title misleading?

The title is correct. It is an example of one beam at a specific altitude during an experiment that

lasted multiple days.

Line 185: beam - And at a given time and altitude?

Added.

Line 190: ”...all beams at the altitude of interest....” - How wide is the altitude of interest?

The width of the altitude would be the width/size of the rangegates of the ISR data. We have changed

the text slightly to clarify.

Line 210: ”...data quality parameters were poor...” - Elaborate?

The 3 sentences that explain the data quality filtering currently in the paper are:

All data shown here was downloaded from the online databases and error-filtered as suggested in the

AMISR user manual (Lamarche, 2022). That is, electron density measurements smaller or the same

size as the error estimate, dNe, and data where the data quality parameters were poor, were excluded

(set to Not-a-number). The error estimate and data quality parameters are normal data products

provided for all RISR-N and RISR-C data.

New text: All data shown here was downloaded from the online databases and error-filtered as suggested in the

AMISR user manual (Lamarche, 2022). That is, electron density measurements smaller or the same size as the error estimate, dN e, and data

where the data quality parameter was flagged as poor, indicating the fail or success of the incoherent

scatter fitting algorithm, were excluded (set to Not-a-number). The error estimate and data quality

parameters are normal data products provided for all RISR-N and RISR-C data.

Line 245: Figure 5

For the uncorrected plot, maybe it would be helpful to put a dashed line or an arrow between RISR-N

and RISR-C (although I can kind of guess where it is).

We have now included a white dashed line in all 3 plots where the two methods are showcased.

I am confused about this method. Isn’t there a density enhancement in the center of the period indi-

cated with the two vertical blue lines

As mentioned in the previous comment on this, we interpret this as a density enhancement over all

beams simultaneously, and not as an irregularity. Our methods can be used on any density changes,

as long as they appear uniformly in all beams.

Line 280: 2 TYPOs

Fixed