The work is interesting, and could be a new contribution, however the work could more clearly justify their conclusions and analysis to better place it in a historical and scientific context. This paper contains numerous typos and grammatical errors in addition to points which require technical corrections.

The Abstract is not concise, e.g. line 36-39 are not clearly tied to the historical observations. Needs to be rewritten after extensive revisions.

The sections of the paper are poorly organized and labeled and do not structurally support what are cited as the primary points in the work.

The Introduction is missing background information on the time period compared to the relevant solar cycle.

Figure 1 shows a 1962 field model. The image is unclear and not possible to read.

Line 101-103; very confusing; is this necessary?

Line 104-109. Confusing in that Figure 1 refers to a 1962 model whereas this text refers to 1900,1905, and 1970. How the recalculation is done is not clear, is this reflected in Table 1?

The table 1 is not clear. Magnetic latitudes coordinates for the two stations should be given. Why Cape Armitage is a variable amount of time east of Gjoahavn is not explained. Where average substorm onset times come from is not explained. Critically, the times of magnetic local times depend on what field model is used. This is not explained.

Line 117 refers to one station but does not identify which one.

Line 197 Figure 3 does not cite a date for its magnetic field model.

Line 214 Figure 4 does not explain how it is generated. It does not explain at precisely what time the polar arcs were observed.

Line 222, the “largest magnetic disturbances” are not clearly identified. The ones at the end of the time period on the 5^th (right hand side of the figure, Z component) appear the largest to me, but are not on the same day (the 4^th?) as the arcs in question.

Line 227 Figure 5 the label on this chart are hard to read. What this Figure is trying to show is not explained. The source of this figure is not included.

Line 264, the color is not cited in the quotation so not sure where this statement is coming from

Line 279 instead of the term ‘polar cap aurora’ it should be investigated whether these observations were far enough north to be called cusp aurora. This can be seen from Longyearbyen near noon in mid-winter and are reddish and rare. Any observations near local noon when it is dark at these high latitudes deserve special attention.

Line 282, Table 2. This table should note whether the compiled stats from multiple crew members includes reports on the same day, which might yield an over-counting of reports compared to a true rate.

Line 317. 1903 being the strongest storms of the century is not cited. The reference to the Halloween storm 100 years later seems like an off-hand comment and is not scientifically justified.

The term streamer may not be identified correctly to the auroral research. Streamer in the modern literature refers to a specific north-south form. However, back in the day it seems more likely to refer to what is now called an auroral ray, or vertical element reaching toward the zenith. This would seem to need to be investigated and explained in the paper, since it is cited as a central point. Importantly, statistics characterizing the numbers of reports and properly coding their identified characteristics is not included anywhere in the document.

Sections 6.1, 6.2, and 6.3 should be removed as they are not conclusive. To be included they would need to clearly identify a specific case study example for each case, including historical reports and magnetometer readings alongside modern reports and magnetometer readings in the scientific literature. Section 6.2 would be interesting alone if developed into a more extensive case study showing observations from both hemispheres.

For 6.1 and 6.3 the use of other modern terms is not strongly justified. An interesting part of the paper is tying the magnetometer observations to particular station observations. In particular it is likely that since the aurora was largely equatorward of the polar cap stations, that the lack of magnetic disturbances is explainable and expected. Modern-day north-south chains of magnetic disturbances during substorms show this effect I believe.

Line 530-535 this is speculative and not conclusive based on analysis of the polar historical observations – recommend to leave out most of this. It is also not cited to the modern literature.

The sources of data for this paper are not shared or openly available. The paper would be stronger if these data were available to others.

Line 557 The paper’s last line is odd, and not cited. I am not familiar with the generation process cited as "electromagnetic radiations from the Sun". Aurora is generally driven by the solar wind, which includes generally includes electromagnetic radiations from the Sun. These stations may include some rare observations of high latitude cusp aurora which is the only type of aurora directly driven by solar wind precipitation on the atmosphere, as opposed to from the solar wind transferring energy into the magnetosphere, which through dayside and nightside reconnection processes can be precipitated on the nightside.

Figure 6 is highly problematic in that it appears to be assuming an oval at an average Kp of 2 to interpret the location of all the observations relative to the auroral oval. This is not justified and should be removed.

Figure 9 is confusing and should be in local magnetic time.

The auroral observation should peak at magnetic midnight if the observations were continuously made, thus the Gjoahavn observations do not represent an absolute rate, this should be clarified for the reader. The number of days with aurora from the 2 hemispheres covers different amounts of time and is not normalized. The red labels for CA are also confusing and do not appear consistent with the first table.

Review report on paper: Conjugate Aurora Observations by the Gjøa and Discovery Expedition,  Author Alv Egeland 

This paper is concerned with history of the first, overlapping in time, aurora and magnetic observations fulfilled in the Northern and Southern polar caps during the 1902-1904 years. The measurements were carried out with the same type of instruments at Gjøahavn (Greenland) in course of the Amundsen’s Expedition through the Northwest Passage and at Cape Armitage (Antarctic) in course of the Scott’s Discovery Expedition.  Both stations were arranged within the polar cap, near the auroral oval poleward boundary and at the almost same geomagnetic longitude (the station Cape Armitage lies in range of 60 min east of Gjøahavn in magnetic time). The observations were carried out for seven months per year that ensured the unique possibility to reveal the conjugate aurora in the polar caps.  There were firstly displayed the “sun-aligned arcs”, positioned within the polar caps and not associated with magnetic disturbances, as well as the poleward moving substorm arcs (PSA), associated with the onset of an auroral substorm. Physical meaning of these phenomena, discovered more 100 years ago, became evident only after the space research epoch beginning.

The paper adequately covers the observations fulfilled in course of expeditions, their advantages and limitations, and their priority. There is no question that paper will be very beneficial to all people who is interesting in ways and means of development of the contemporary science.

But there are following remarks:

1. Meaning of the received results in relation to modern space physics should be described more clearly.
2. I am not expert in English (unfortunately). But, it seems me that English in paper (style, first of all) is unsatisfactory.
3. I recommend changing the paper title as follows: “Conjugate Aurora Observations in Greenland and Antarctic by Amundsen’s Expedition through the Northwest Passage and Scott’s Discovery Expedition”.

                The paper is recommended to publication with regard to these remarks.