the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 01 Feb 2024
Early auroral photography and observations at the Sodankylä Geophysical Observatory in Finland, 1927–1929
Abstract. Auroral photography started in 1927 at the Sodankylä Geophysical Observatory (SGO) by the initiative of famous Norwegian scientist Carl Störmer. In less than two years about 600 photographs of auroras were taken at Sodankylä. Some of the images were obtained simultaneously at auxiliary stations for parallactic determinations of the height of auroral arcs. Most of the pictures of auroras were vanished in the destruction of the SGO during the war in 1944. About 200 images were rescued in the archive of the Finnish Meteorological Institute where they have been recently found. These pictures of auroras are the first ones taken in Finland.
During the Polar year period 1932–1933, auroral photographing was mostly discontinued but visual observations of auroras were made instead at several sites in Lapland.
Eyvind Sucksdorff's contribution to studies of auroras was a pioneering effort, with minimal resources. In Finland, regular observations of auroras started again during the International Geophysical Year (IGY) 1957–1958.
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RC1: 'Comment on hgss-2024-1', Anonymous Referee #1, 04 Feb 2024
This is a very nice account of early auroral observations in Finland with a through-line supplied by the Sucksdorff family (husband, wife, and son). I suggest several changes for minor English corrections and have a few questions, which should be easily answered, that arose during my reading of the manuscript.
Suggestions for minor cosmetic improvements to the text:
Line 22: delete “were”
Line 26: Photographing => photography
Line 38: using => using the
Line 59: on that time => at that time
Line 60: Circle thus => Circle and thus
Line 76: Sucksdorff, => Sucksdorff
Line 78: According to => In accordance with
Line 79: photographing => photography
Line 81: glass => a glass
Line 90: the Störmer´s => Störmer’s
Line 92: buildings => the buildings
Line 94: rescued before the war and archived => archived before the war
Line 107: An Störmer camera is in the front => A Störmer camera is in front
Line 113: special => a specially
Line 116: winter => the winter of
Line 118: winter => of
Line 119: only in a => only a
Line 149: coincided => coincided with
Line 154: delete “even”
Line 155: delete “already”
Line 156: Feb => February
Line 164: the midnight => midnight
Line 170: Vanished => destroyed
Line 180: is tree => is a tree
Lines 210-211: “E. Sucksdorff introduced for Polar year plan of visual observations of auroras special graphical symbols for different types of auroras. There were about 20 …”
Suggest rewriting as: “E. Sucksdorff introduced special graphical symbols for different types of auroras for the Polar year plan of visual observations. About 20 …‘’
Line 212: for => indicated
Line 214: but continued observations => that were continued
Line 226: quadrant => a quadrant
Lines 236-237: only very few => little
Line 249: have been => were
Line 253 : On the other hand => In addition,
Line 268: research was => results were
Line 273: observation => observational
Line 279: like => such as
Line 282: 1910s => the 1910s
Line 283: 1950s => the 1950s
Questions:
Lines 179-180: “The black belt under the auroral lights is tree line across the river.” There is some ambiguity here that needs to be addressed. There is a uniform downward slanting thin black line in both of the top two images (as well as the four below) that does not suggest a tree line. Make it clear that you are not referring to this line as the tree line.
Lines 205-206: “Two full-scale manned magnetic observatories were set up for the polar years in Finland.” I am assuming one of these was at Sodankylä. Where was the other?
Lines 272-274: “The entire observation material collected in 1920s and 1930s is now in the data archive of the SGO.” But what about the 200 auroral photographs in the Helsinki FMI library?
Citation: https://doi.org/10.5194/hgss-2024-1-RC1 -
AC1: 'Reply on RC1', H. Nevanlinna, 06 Feb 2024
1st question:
The two top pictures show auroral lights over the frozen river Kitinen. The black horizontal belt under the auroral lights near the middle of the frame is the tree line on the opposite bank of the river.
2nd question:
In Finland, two full-scale manned magnetic observatories were set up temporarily for the polar years 1932–1933. They were Petsamo (69.5°N; 31.2°E) near the coast of the Arctic Sea, now in the territory of Russia, and Kajaani in East-Finland (64.2°N; 27.7°E) (Simojoki, 1978).
3rd question:
About 200 photographs of aurora rescued from the destruction of the Sodankylä observatory in 1944 and recently found in the library of the Finnish Meteorological Institute are now in the data archive of the SGO.
Citation: https://doi.org/10.5194/hgss-2024-1-AC1 -
RC2: 'Reply on AC1', Anonymous Referee #1, 06 Feb 2024
I am satisfied that the authors have addressed my questions and recommend for publication.
I do not need to see the manuscript again.
Citation: https://doi.org/10.5194/hgss-2024-1-RC2 -
AC6: 'Reply on RC2', H. Nevanlinna, 03 Mar 2024
Ok
Citation: https://doi.org/10.5194/hgss-2024-1-AC6
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AC6: 'Reply on RC2', H. Nevanlinna, 03 Mar 2024
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RC2: 'Reply on AC1', Anonymous Referee #1, 06 Feb 2024
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AC1: 'Reply on RC1', H. Nevanlinna, 06 Feb 2024
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RC3: 'Comment on hgss-2024-1', Anonymous Referee #2, 15 Feb 2024
The paper describes how the aurora observation started at SGO, as the first time regular observation inside the arctic circle as well as Finland. This started with aurora photography in 1927, i.e., during the solar maximum of cycle 16, but diminished after a few years. The photograph method was replaced by visual investigation 1932 (international polar year), continuing to 1944. This paper shows the quality of these photographs with some examples, and shows some results using the visual record.
These information are useful in examining the historical aurora activities and the solar cycle 16. In one would like to study these historical event, this paper helps in judging the need to examine these old data. Therefore, this paper fits publication in "History of Geo- and Space Sciences". However, some more useful information can be added for such purpose. For example, the date of photographed nights of about 100 copies that we rescued recently should be given. I made many comments to increase the value of this paper. I would like to read again after the authors take into account of them.
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line 42-48:
Topic is somewhat back and forth between photography, triangulation, and SGO observation. Could you streamline these topics: First trial and successful triangulation in 1870s, first successful photograph in 1890s, and start of both at SGU in 1880s (which is before the successful photograph). Probably, explanation of "successful" (what do you mean by it?) would help.line 46: "This technique": Could you briefly explain?
line 58: "Sodankylä geophysical observatory": capitol "G" and "O" to be consistent with abstract. Also, please use "SGU" instead of "Sodankylä observatory" afterward.
line 64-68: Explanation of the staff is not fitting to this paper. Please remove. It is enough to explain in line 76, like "... to the directer of SGO, Eyvind Sucksdorff, who is also a photographer, that....."
line 78: "According to Störmer's plan," => "As planned by Störmer". Same change for line 235.
line 89: "special cameras": What is the difference from ordinary "Störmer ́s auroral camera " that is explained in the previous paragraph (line 81-87)?
line 113: "special constructed projector": Any reference?
line 118: How many nights are taken in total during 1927-1929 and how many are rescued? Since it is solar maximum and early declining phase, it would be nice to have a list of dates of available photograph (either in the text or as the supplemental material) so that other people can easily search for historical events. Although no scientific result was derived at that time, global network of the historical data might change the situation.
line 122: "They belong to the first photographs of auroras in Finland": What about one that are tried "Sodankylä Polar year observatory 1882–1884" (line 43)? No success?
line 153: Corona is a visual form of "discrete aurora over the zenith", and better to write as "discrete aurora over the zenith (so called corona)"
line 157: "magnetic K-index increased up to 8/9": please give definition of local K=8 and K=9. Is 3-hour dB 990-1500 nT and > 1500 nT, respectively?. Also, please add K values (just write value) in Figure 5.
Figure 6: Does any of above two pictures have the same timing as one of four pictures in the lower panels? If timing is known, please add that information (ideally in the picture, otherwise in the caption).
line 205: "manned magnetic observatories": SGO and where (Helisnki?)
line 212: "20 different symbols": please make a table of these symbols, and corresponding auroral forms in the modern terminology.
line 214-216: visual observations for 750 nights means much more pictures, but at line 119-120 says "very few pictures were taken" in 1930. Are all visual observation without photographing?
line 224-225: "during 1927–1929 were not very successful". Please comment on Figure 4. Is it one of very few success case, or was the altitude determination failed for this picture without reference star?
line 240: " archive of the SGO": could you give contact method (e.g., in acknowledgement). The same for the 40-years reading data (line 246) if they are archived.
line 254-255: "increasing decadal trend": The 100 year cycle of the solar maximum peak could be due to " Centennial Gleissberg Cycles" (e.g., Feynman, J., and A. Ruzmaikin, doi:10.1002/2013JA019478).
Citation: https://doi.org/10.5194/hgss-2024-1-RC3 -
AC2: 'Reply on RC3', H. Nevanlinna, 20 Feb 2024
RC3 comment: "However, some more useful information can be added for such purpose. For example, the date of photographed nights of about 100 copies that we rescued recently should be given".AC reply: The dates of rescued auroral photographs 1927–1929 will be given in Appendix A (see below).
RC3 line 42-48: The following replaces the sentence on line 42 "Trials ...".Trials of height measurements and photography of auroras were made at the Sodankylä Polar year observatory 1882–1884. Photographs of auroras were unsuccessful because the sensitivity of the films available was too low for exposing faint auroral lights. The results of simultaneous visual triangular height measurements of auroras were unrealistic and scattering widely because the baseline was too short (4 kilometres) for accurate determinations of auroral forms observed at both ends of the baseline.
RC3 line 46: "This technique". Reply: The aurora is photographed simultaneously from two or more stations situating at mutual distances of several tens of kilometres. The sites are connected by telephone, so that the observers can direct their cameras towards the same region of sky and expose at the same time. The location of stars on the photographs fixes the astronomical orientation of auroral forms (Chapman and Bartels, 1940; Störmer, 1955).
RC3 line 58: Ok capital letters will be used as suggested.
RC3 line 64-68: The number of staff is mentioned here in order to point out that very few workers operated the observatory working on many demanding tasks.
RC3 line 78: Changed: "As planned by Störmer"
RC3 line 89: The word "special" is removed
RC3 line 113: No reference is found but in the annual report of the SGO in 1928 there is a mention that in the lack of a photo projector, the height determinations could not be done in the SGO. This was the reason to send the auroral photographs to Norway in Störmer's laboratory for analysis by an image projector. However, no information exists about the possible results.
RC3 line 118: "How many nights are taken in total during 1927-1929 and how many are rescued?" The number of rescued photographs is 226 out of total amount 592. A list of dates will be given in the appendix.
RC3 line 122: As was mentioned above the sensitivity of film used in auroral cameras during the Polar Year station Sodankylä 1883-83 was too low for successful photographing.
RC3 line153: Ok. I will write "discrete aurora over the zenith (so called corona)"
RC3 line 157: "magnetic K-index increased up to 8/9" is now "the three-hour magnetic K-index increased up to 8/9". K = 8 corresponds to magnetic field amplitudes between 990 nT and 1500 nT, and when K = 9, amplitudes are > 1500 nT
RC3 Figure 6. Each of six frames in one plate was exposed one after the other in about 30 seconds intervals. The whole photographing operation in this case took a few minutes.
RC3 205: The two temporary observatories during the Polar Year 1932-1933 were Petsamo (69.5°N; 31.2°E) near the coast of the Arctic Sea, now in the territory of Russia, and Kajaani in East-Finland (64.2°N; 27.7°E).
RC3 line 212: The symbols introduced by Sucksdorff exist in hand-written paper document only. They were used in connection with visual observations mainly during the Polar Year programme 1932–1933 in Lapland. I think that these symbols are not relevant for the present manuscript in which auroral photography is the main theme. A study of the visual auroral observations based on Sucksdorff's auroral codes could be a goal for a future investigation.
RC3 line 214-216: All visual observations carried out in 1932–1940 by Sucksorff's team are without photographing, naked eye sightings only. The original material, consisting of about 750 observations, is in the archive of the SGO.In the annual reports of the SGO, compiled by Sucksdorff, there are written, "very few auroral photos were taken" in the years after 1929. However, no further information exists about these "few photographs".
RC3 line 224-225: Calculations of auroral heights were done in the Störmer's auroral laboratory in Oslo. However, no information exists about the results obtained.For the figure caption for Fig. 4: The lower edge of the auroral form is about 20 degrees above the horizon towards the brightest stars of the constellation Pegasus.
RC3 line 240: The following sentence is added: All data requests should be directed to the SGO (eija.tanskanen@sgo.fi). The data plotted in Fig. 8 will be in the Appendix B (see below).
RC3 line 254-255: The following sentence will be added after the end of line 257: This long-term trend in the annual auroral occurrence rate may be connected with the centennial Gleissberg cycle of solar activity (e.g., Feynman and Ruzmaikin, 2014).
Appendix A
______________________________________
Table 1. Dates of available auroral photographs
at the SGO 1927–1929
______________________________________
Date Number of single photos
1927
Nov 18 24
Nov 19 6
Dec 13 33
Dec 14 3
Dec 18 6
Dec 28 42
1928
Jan 27 46
Mar 11 18
Mar 13 30
1929
Feb 27 18
Total 226
______________________________________
Appendix B
________________________________________________
Table 2. Annual numbers of auroral nights1
at the SGO 1914–1954, local magnetic activity index2 (Ak),
and sunspot number3 (R)
________________________________________________
Year Number of nights Ak R
1914 43 24 16.1
1915 73 52 79.0
1916 75 68 95.0
1917 68 64 173.6
1918 26 88 134.6
1919 27 83 105.7
1920 18 57 62.7
1921 24 51 43.5
1922 16 66 23.7
1923 10 26 9.7
1924 8 26 27.9
1925 16 42 74.0
1926 29 76 106.5
1927 21 58 114.7
1928 25 64 129.7
1929 43 71 108.2
1930 48 119 59.4
1931 32 59 35.1
1932 43 76 18.6
1933 45 63 9.2
1934 32 45 14.6
1935 24 57 60.2
1936 52 63 132.8
1937 52 75 190.6
1938 39 96 182.6
1939 52 98 148.0
1940 59 97 113.0
1941 85 108 79.2
1942 51 100 50.8
1943 65 115 27.1
1944 36 66 16.1
1945 33 55.3
1946 57 70 154.3
1947 63 106 214.7
1948 72 100 193.0
1949 64 99 190.7
1950 37 113 118.9
1951 82 136 98.3
1952 52 142 45.0
1953 80 105 20.1
1954 52 70 6.6
________________________________________________
1 Finnish Meteorological Institute - meteorological yearbooks
2 Sodankylä Geophysical Observatory - magnetic yearbooks
3 Solar Influences Data Analysis Center WDC-SILSO
Citation: https://doi.org/10.5194/hgss-2024-1-AC2 -
RC5: 'Reply on AC2', Anonymous Referee #2, 20 Feb 2024
Nice explanations to my questions and nice to see the appendix. Please integrate these explanations in the text.
One thing to reserve is the explanation of the staff. Just "total three staff including director" is enough and no need to describe the detail. Such "general public reading" type information does not fit the main text (footnote or acknowledgement is ok).
Citation: https://doi.org/10.5194/hgss-2024-1-RC5 -
AC3: 'Reply on RC5', H. Nevanlinna, 20 Feb 2024
My replies on the comments sent by the RC3 will be included in the final version of the manuscript.
Citation: https://doi.org/10.5194/hgss-2024-1-AC3
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AC3: 'Reply on RC5', H. Nevanlinna, 20 Feb 2024
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RC5: 'Reply on AC2', Anonymous Referee #2, 20 Feb 2024
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AC4: 'Reply on RC4', H. Nevanlinna, 28 Feb 2024
RC4: "The description of data recovery needs more details. What is the ultimate source of information on the number of those (about 400) photographs that are not found? Maybe some observatory or personal notebooks of E. Sucksdorff (ES)."
Reply: The main sources of information about the history of auroral images taken at SGO are hand-written notebooks of Eyvind Sucksdorff for 1927–1929. There are described relevant data for each photograph (date, exposure time, orientation of camera etc.). In Appendix A there is a table showing the dates of rescued auroral photos as well as the lost ones (see below) based on Sucksdorff's notebooks.
RC4: "These source documents should all be described, scanned and made publicly available in digital format. Even better if they were read to digital tables. Now nothing of such possible development is mentioned. Similarly, the photographs should be scanned and stored in a public digital archive."
Reply: The original source information is stored in tables and auroral images available have been digitized. They are in the digital archive of the SGO. However, for the moment our policy of releasing the auroral data is restricted to individual requests only which should address to the SGO (eija.tanskanen@sgo.fi).
RC4: " How does the image timing go? Judging from the temporal time evolution of auroral forms and intensity depicted in the 6 images, a likely order is clockwise from top left to end at middle left."
Reply: The image order in the plate of six single photographs was clockwise.
RC4: "As described in the manuscript, there was a vigorous photography program in Norway, which led to the improved determination of auroral height. In this situation, I was left wondering why at all Norwegians wanted to install a station in SGO? Historical order of events is missing. "
Reply: There was a plan promoted by the scientific community in Norway that the auroral photography network will be expanded outside Norway for the coming Polar Year 1932–1933. Stations in Greenland, North-Norway (Tromsö) and on Bear Island in the Arctic Sea were set up. The SGO observatory was located far away in the east from the sites of the Norwegian auroral program and could allow a more wide observation view for the auroral photography during the Polar Year.
Eyvind Sucksdorff visited Störmer's auroral laboratory in 1938 and discussed there about auroral research but no common writings exist.
RC4: "Have SGO photographic films been saved and archived in Norway?"
Reply: According to Sucksdorff's notebooks there are comments that images from Sodankylä and from the auxiliary station were sent to Oslo for further analysis. I have been in contact to Oslo University and asked if they have auroral images from the SGO but without results.
RC4: "Visual auroral observations by ES from 1932 to 1944 are said to be archived at SGO. What does it practically mean? "
All observations with related information (observer, time, location, coding, weather info etc.) must be made publicly available with related URLs included. Similarly for the "routine" observations from 1914 until 1954. What about the auroral observations by the Danes? Are these included in the same dataset?"
Reply: Results of visual auroral observations 1932–1944 carried out at the SGO and several sites in Lapland are in hand-written notebooks only. We have plans to transcribe the results in form of tables and make summaries of the observations. There are about 10 rather unorganized notebooks available including the visual observations carried out by the Danish team.
RC4: " Line 29. Contribution by ES was pioneering probably only in Finland."
Reply: This is rewritten: In Finland, Eyvind Sucksdorff´s contribution to research of auroras was a pioneering effort with minimal resources.
RC4: " Lines 83 and 89. Is frame = photograph? If yes, ignore "frame". Does 600 photographs mean 100 plates?
Reply: Yes, "frame" is changed to "photograph". Yes, c. 600 photographs mean c. 100 plates.
RC4: " Line 94. 200 photographs means about 35 paper sheets? How many exactly?
Reply: The paper copies of single photographs are larger than the originals in a plate. The size of a single paper photograph is about 4 x 4 cm. Each paper sheet consists of 10 single photographs. The number of sheets is 20.
RC4: " Statement (see lines 149-151) "The second greatest magnetic storm during this cycle, as recorded by magnetometers at Sodankylä.” "The second greatest magnetic disturbance." would be a possible statement once authors define exactly, how the intensity estimate was made, perhaps based on the local K index? "
Reply: The lines 149-151 are rewritten as follows: The February 27, 1929 magnetic storm observed at the SGO and other magnetic stations at high latitudes was one of the major magnetic storms during the solar cycle 16 (1923–1933) (e.g., Goldie, 1929; Rowland, 1929).
RC4: " Also, additional evidence on storm evolution is needed to verify if the disturbance of the previous night was part of the same storms. Surely it was not "a minor storm".
Reply: Corrected: The February 27, 1929 magnetic storm at the SGO started already in the evening hours of February 26 and ended near midday of 28th (Fig. 5).
RC4: " Fig. 6 caption would read more clearly as follows: "The two top pictures show auroral lights reflected from the frozen river Kitinen. The black belt under the auroral lights, which is the tree line on the other side of the river, is seen in all pictures, most clearly in the top row." This is the setting in all 6 photographs. The exact start and end times (hh:min:sec) of each photograph should be added to the left or right of each panel so that a rough estimate of auroral intensity and temporal order could be obtained. If these images were obtained at 30s intervals, the total time is at most 3.5 min, not 5 min as in text. "
Reply. The caption is rewritten as follows:
Figure 6. Auroral displays on February 27, 1929 as captured by a camera at the Sodankylä observatory. Each frame on the photographic plate represents auroras in intervals of about 30 seconds at about 20 h (UT) to the west. The exposure time varies between 1 to 30 seconds. The first photograph is on the top left.
The two top pictures show auroral lights reflected from the frozen river Kitinen. The black belt under the auroral lights, which is the tree line on the other side of the river, is seen in all pictures, most clearly in the top row.
Next four pictures show rapidly changing auroral forms, veils and spirals. Two bright spots are planets Jupiter (upper) and Venus (lower) in the west and about 15° from the horizon. (Photo: E. Sucksdorff¨s collection SGO).
The total time (about 5 min) is corrected: about 3.5 minutes.
RC4: " The exact start and end times (hh:min:sec) of each photograph should be added to the left or right of each panel so that a rough estimate of auroral intensity and temporal order could be obtained. "
Reply: They will be given later. There are some problems with Sucksdorff's time writings during the storm.
RC4: " Figure 8. While the number of auroral nights gives some information about the occurrence of auroras, the more correct way is to present the fraction of the nights with auroras to the number of all nights that were "available" for auroras to be observed. So, in addition to the figure of absolute numbers, authors should present these fractions. Otherwise, the study is rather futile. As seen in the figure, there are times when auroral occurrence and magnetic activity are very different, even differently located over the cycle. Also, the multi-decadal rise is dubiously large in auroras. These differences are, very likely, due to the variable weather conditions, which would be corrected by the above fractions."
Reply: We have added new data to the auroral data shown in Fig. 8 (see below) The data is taken from the compilation of visual auroral data by Legrand and Simon (1987). The data collection comprises of several thousands auroral records from sub-auroral latitudes in the northern hemisphere from the years 1780–1979This data series correlates reasonable well with the time variation of auroras obtained form the SGO during 1914–1954. However, there are certain anomalies in the SGO curve when magnetic activity and auroral occurrence are quite different due probably varying weather and cloudy conditions. The original conclusion that there has been an increasing trend in the occurrence of aurora 1914-1954 at SGO is still valid.
[Legrand, J.-P. and Simon, P.A., 1987. Two hundred years of auroral activity (1780–1979). Annales Geohysicae, 5, 161–167].
There is a picture attached in the end of the reply sheet showing the correlation between global aa-index and auroral occurrence number derived by Legrand & Simon. The linear correlation for the years 1914–1954 is +0.79.
RC4: "Mention in text and in caption what is the magnetic activity index used here."
Reply: The magnetic activity index is the annual mean of daily Ak number taken from the magnetic yearbooks of the SGO.
RC4 line 205. "Line 205. Mention which observatories."
Reply: The two temporary observatories during the Polar Year 1932-1933 were Petsamo (69.5°N; 31.2°E) near the coast of the Arctic Sea, now in the territory of Russia, and Kajaani in East-Finland (64.2°N; 27.7°E).
RC4: " Line 241-242. This is an odd sentence. Auroral occurrence studies are also part of auroral studies."
Reply: This sentence is now: Independent from auroral studies, Visual observations of the occurrence of auroras were made in connection with daily meteorological observations at the Sodankylä observatory since the founding of the observatory in 1914.
RC4: " Line 156. Ref to Fig. 5 must be earlier in text.
Reply: Corrected
RC4: " Line 254. It is multi-decadal, not decadal."
Reply. Ok. Corrected.
RC4: " Line 272. Write: auroras obtained almost one hundred years ago are the first ones in Finland."
Reply: Ok. Corrected
RC4: " References are relevant except for all the three papers by Tanskanen. Neither Tanskanen et al., 2005, nor Tanskanen, 2009, deals with auroral observations. "
Reply: Tanskanen et al. (2005) and Tanskanen (2009) found that the largest substorm numbers and peak amplitudes were found during the declining solar cycle phases. Their analysis was derived using magnetic data from the solar cycle 1993–2003. This similar to conclusion here that auroral occurrence rate is generally enhanced during the declining phase of a solar cycle.
RC4: " Tanskanen, 2022, is not even a scientific paper. "
Reply: Ok. This reference is deleted.
RC4: " The centennial increase in geomagnetic activity was found by Mayaud in 1972".
Reply: Yes. The reference Mayad (1972) is added in the reference list.
Mayaud, P.N.: The aa Indices: A 100-Year series characterizing the magnetic activity. Journal of Geophysical Research, 77, 6870–6874, https://doi.org/10.1029/JA077i034p06870, 1972.
Appendix A
_________________________________
Table 1a. Dates1 of available auroral photographs
at the SGO 1927–1929
________________________________________
Date Number of single photos
1927
Nov 18 24
Nov 19 6
Dec 13 33
Dec 14 3
Dec 18 6
Dec 28 42
1928
Jan 27 46
Mar 11 18
Mar 13 30
1929
Feb 27 18
Total 226
______________________________________
Table 1b. Dates1 of photographs lost
in the war 1944
______________________________________
Date Number of single photos
1928
Dec 6 9
1929
Jan 29 18
Feb 17 11
Feb 27 147
Mar 7 12
Mar 8 40
Mar 11 42
Mar 14 78
Mar 27 27
Total 384
_____________________________________
1 The data is based on original hand-written
notebooks by E. Sucksdorff
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AC2: 'Reply on RC3', H. Nevanlinna, 20 Feb 2024
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RC4: 'Comment on hgss-2024-1', Anonymous Referee #3, 20 Feb 2024
This manuscript discusses the history of the earliest auroral photography observations in Finnish Lapland since 1927, and visual observations in 1914-1954. The text may be interesting for an audience of science history. However, there is very little of scientific results included or extracted from these observations, largely, as explained in the manuscript, due to the failure of the intended main aim of auroral photography in determining the height of the different types of auroras. In this situation, the most important scientific contribution of this manuscript would be a detailed description of the recovery of the material and its archival in a publicly available dataset (including related URLs). Unfortunately, this is not sufficiently done in this manuscript and needs to be finished before the manuscript is worthy of publication. I have also other important reservations on the scientific part of this manuscript as detailed below.
The description of data recovery needs more details. What is the ultimate source of information on the number of those (about 400) photographs that are not found? Maybe some observatory or personal notebooks of E. Sucksdorff (ES)
These source documents should all be described, scanned and made publicly available in digital format. Even better if they were read to digital tables. Now nothing of such possible development is mentioned. Similarly, the photographs should be scanned and stored in a public digital archive.
If these 200 images, which were found in the archive of the FMI, were now just moved to another archive at SGO, without making them publicly and digitally available, science would not much advance. The quality of this manuscript is marginal without its material being simultaneously prepared for a digitally available archive.
Have SGO photographic films been saved and archived in Norway?Visual auroral observations by ES from 1932 to 1944 are said to be archived at SGO. What does it practically mean? All observations with related information (observer, time, location, coding, weather info etc) must be made publicly available with related URLs included. Similarly for the "routine" observations from 1914 until 1954. What about the auroral observations by the Danes? Are these included in the same dataset?
Note also that visual auroral observations also need be supplied by information on meteorological conditions for the whole time interval of observations in order to know on how many days auroras could have occurred for the weather (see also later).As described in the manuscript, there was a vigorous photography program in Norway, which led to the improved determination of auroral height. In this situation, I was left wondering why at all Norwegians wanted to install a station in SGO? Historical order of events is missing.
Line 115 mentions "..no information exists about the results of the height analysis in Oslo". Introduction says the contrary. Or does this refer to SGO observations? I would like to have a bit more information on whether SGO observations were used or not? What do Störmer's publications tell about this? Did ES have any collaborative research papers with Störmer and if yes, were SGO observations used there?Statement (see lines 149-151) "The second greatest magnetic storm during this cycle, as recorded by magnetometers at Sodankylä..". Since the magnetic disturbances at SGO are mainly due to auroral and FAC currents, not due to the ring current which measures the intensity of storms, it is misleading to talk about the intensity of a magnetic storm based on SGO observations. "The second greatest magnetic disturbance.." would be a possible statement once authors define exactly, how the intensity estimate was made, perhaps based on the local K index? Also, additional evidence on storm evolution is needed to verify if the disturbance of the previous night was part of the same storms. Surely it was not "a minor storm".
Fig. 6 caption would read more clearly as follows: "The two top pictures show auroral lights reflected from the frozen river Kitinen. The black belt under the auroral lights, which is the tree line on the other side of the river, is seen in all pictures, most clearly in the top row." This is the setting in all 6 photograph. The exact start and end times (hh:min:sec) of each photograph should be added to the left or right of each panel so that a rough estimate of auroral intensity and temporal order could be obtained. If these images were obtained at 30s intervals, the total time is at most 3.5 min, not 5 min as in text.
How does the image timing go? Judging from the temporal time evolution of auroral forms and intensity depicted in the 6 images, a likely order is clockwise from top left to end at middle left. This has to be checked and the related auroral dynamics discussed in detail. There surely is some information about the structure of the auroral camera in ES notes.Figure 8. While the number of auroral nights gives some information about the occurrence of auroras, the more correct way is to present the fraction of the nights with auroras to the number of all nights that were "available" for auroras to be observed. So, in addition to the figure of absolute numbers, authors should present these fractions. Otherwise, the study is rather futile. As seen in the figure, there are times when auroral occurrence and magnetic activity are very different, even differently located over the cycle. Also, the multi-decadal rise is dubiously large in auroras. These differences are, very likely, due to the variable weather conditions, which would be corrected by the above fractions.
Mention in text and in caption what is the magnetic activity index used here. A URL is also need for that.
References are relevant except for all the three papers by Tanskanen. Neither Tanskanen et al., 2005, nor Tanskanen, 2009, deals with auroral observations. First relevant papers on auroras exist by Silverman and by Feynman in the 1980s, and on geomagnetic activity even earlier, starting from the book by Chapman and Barrels in 1940. Tanskanen, 2022, is not even a scientific paper. The centennial increase in geomagnetic activity was found by Mayaud in 1972. Several papers, in addition to Lockwood, 2001, have studied the connection of this increase to solar and heliospheric parameters.Minor notes:
Line 29. Contribution by ES was pioneering probably only in Finland.
Lines 83 and 89. Is frame = photograph? If yes, ignore "frame". Does 600 photographs mean 100 plates?
Line 94. 200 photographs means about 35 paper sheets? How many exactly?
Line 156. Ref to Fig. 5 must be earlier in text.
Line 205. Mention which observatories.
Line 241-242. This is an odd sentence. Auroral occurrence studies are also part of auroral studies.
Line 254. It is multi-decadal, not decadal.
Line 272. Write: auroras obtained almost one hundred years ago are the first ones in Finland.
Citation: https://doi.org/10.5194/hgss-2024-1-RC4 -
AC4: 'Reply on RC4', H. Nevanlinna, 28 Feb 2024
RC4: "The description of data recovery needs more details. What is the ultimate source of information on the number of those (about 400) photographs that are not found? Maybe some observatory or personal notebooks of E. Sucksdorff (ES)."
Reply: The main sources of information about the history of auroral images taken at SGO are hand-written notebooks of Eyvind Sucksdorff for 1927–1929. There are described relevant data for each photograph (date, exposure time, orientation of camera etc.). In Appendix A there is a table showing the dates of rescued auroral photos as well as the lost ones (see below) based on Sucksdorff's notebooks.
RC4: "These source documents should all be described, scanned and made publicly available in digital format. Even better if they were read to digital tables. Now nothing of such possible development is mentioned. Similarly, the photographs should be scanned and stored in a public digital archive."
Reply: The original source information is stored in tables and auroral images available have been digitized. They are in the digital archive of the SGO. However, for the moment our policy of releasing the auroral data is restricted to individual requests only which should address to the SGO (eija.tanskanen@sgo.fi).
RC4: " How does the image timing go? Judging from the temporal time evolution of auroral forms and intensity depicted in the 6 images, a likely order is clockwise from top left to end at middle left."
Reply: The image order in the plate of six single photographs was clockwise.
RC4: "As described in the manuscript, there was a vigorous photography program in Norway, which led to the improved determination of auroral height. In this situation, I was left wondering why at all Norwegians wanted to install a station in SGO? Historical order of events is missing. "
Reply: There was a plan promoted by the scientific community in Norway that the auroral photography network will be expanded outside Norway for the coming Polar Year 1932–1933. Stations in Greenland, North-Norway (Tromsö) and on Bear Island in the Arctic Sea were set up. The SGO observatory was located far away in the east from the sites of the Norwegian auroral program and could allow a more wide observation view for the auroral photography during the Polar Year.
Eyvind Sucksdorff visited Störmer's auroral laboratory in 1938 and discussed there about auroral research but no common writings exist.
RC4: "Have SGO photographic films been saved and archived in Norway?"
Reply: According to Sucksdorff's notebooks there are comments that images from Sodankylä and from the auxiliary station were sent to Oslo for further analysis. I have been in contact to Oslo University and asked if they have auroral images from the SGO but without results.
RC4: "Visual auroral observations by ES from 1932 to 1944 are said to be archived at SGO. What does it practically mean? "
All observations with related information (observer, time, location, coding, weather info etc.) must be made publicly available with related URLs included. Similarly for the "routine" observations from 1914 until 1954. What about the auroral observations by the Danes? Are these included in the same dataset?"
Reply: Results of visual auroral observations 1932–1944 carried out at the SGO and several sites in Lapland are in hand-written notebooks only. We have plans to transcribe the results in form of tables and make summaries of the observations. There are about 10 rather unorganized notebooks available including the visual observations carried out by the Danish team.
RC4: " Line 29. Contribution by ES was pioneering probably only in Finland."
Reply: This is rewritten: In Finland, Eyvind Sucksdorff´s contribution to research of auroras was a pioneering effort with minimal resources.
RC4: " Lines 83 and 89. Is frame = photograph? If yes, ignore "frame". Does 600 photographs mean 100 plates?
Reply: Yes, "frame" is changed to "photograph". Yes, c. 600 photographs mean c. 100 plates.
RC4: " Line 94. 200 photographs means about 35 paper sheets? How many exactly?
Reply: The paper copies of single photographs are larger than the originals in a plate. The size of a single paper photograph is about 4 x 4 cm. Each paper sheet consists of 10 single photographs. The number of sheets is 20.
RC4: " Statement (see lines 149-151) "The second greatest magnetic storm during this cycle, as recorded by magnetometers at Sodankylä.” "The second greatest magnetic disturbance." would be a possible statement once authors define exactly, how the intensity estimate was made, perhaps based on the local K index? "
Reply: The lines 149-151 are rewritten as follows: The February 27, 1929 magnetic storm observed at the SGO and other magnetic stations at high latitudes was one of the major magnetic storms during the solar cycle 16 (1923–1933) (e.g., Goldie, 1929; Rowland, 1929).
RC4: " Also, additional evidence on storm evolution is needed to verify if the disturbance of the previous night was part of the same storms. Surely it was not "a minor storm".
Reply: Corrected: The February 27, 1929 magnetic storm at the SGO started already in the evening hours of February 26 and ended near midday of 28th (Fig. 5).
RC4: " Fig. 6 caption would read more clearly as follows: "The two top pictures show auroral lights reflected from the frozen river Kitinen. The black belt under the auroral lights, which is the tree line on the other side of the river, is seen in all pictures, most clearly in the top row." This is the setting in all 6 photographs. The exact start and end times (hh:min:sec) of each photograph should be added to the left or right of each panel so that a rough estimate of auroral intensity and temporal order could be obtained. If these images were obtained at 30s intervals, the total time is at most 3.5 min, not 5 min as in text. "
Reply. The caption is rewritten as follows:
Figure 6. Auroral displays on February 27, 1929 as captured by a camera at the Sodankylä observatory. Each frame on the photographic plate represents auroras in intervals of about 30 seconds at about 20 h (UT) to the west. The exposure time varies between 1 to 30 seconds. The first photograph is on the top left.
The two top pictures show auroral lights reflected from the frozen river Kitinen. The black belt under the auroral lights, which is the tree line on the other side of the river, is seen in all pictures, most clearly in the top row.
Next four pictures show rapidly changing auroral forms, veils and spirals. Two bright spots are planets Jupiter (upper) and Venus (lower) in the west and about 15° from the horizon. (Photo: E. Sucksdorff¨s collection SGO).
The total time (about 5 min) is corrected: about 3.5 minutes.
RC4: " The exact start and end times (hh:min:sec) of each photograph should be added to the left or right of each panel so that a rough estimate of auroral intensity and temporal order could be obtained. "
Reply: They will be given later. There are some problems with Sucksdorff's time writings during the storm.
RC4: " Figure 8. While the number of auroral nights gives some information about the occurrence of auroras, the more correct way is to present the fraction of the nights with auroras to the number of all nights that were "available" for auroras to be observed. So, in addition to the figure of absolute numbers, authors should present these fractions. Otherwise, the study is rather futile. As seen in the figure, there are times when auroral occurrence and magnetic activity are very different, even differently located over the cycle. Also, the multi-decadal rise is dubiously large in auroras. These differences are, very likely, due to the variable weather conditions, which would be corrected by the above fractions."
Reply: We have added new data to the auroral data shown in Fig. 8 (see below) The data is taken from the compilation of visual auroral data by Legrand and Simon (1987). The data collection comprises of several thousands auroral records from sub-auroral latitudes in the northern hemisphere from the years 1780–1979This data series correlates reasonable well with the time variation of auroras obtained form the SGO during 1914–1954. However, there are certain anomalies in the SGO curve when magnetic activity and auroral occurrence are quite different due probably varying weather and cloudy conditions. The original conclusion that there has been an increasing trend in the occurrence of aurora 1914-1954 at SGO is still valid.
[Legrand, J.-P. and Simon, P.A., 1987. Two hundred years of auroral activity (1780–1979). Annales Geohysicae, 5, 161–167].
There is a picture attached in the end of the reply sheet showing the correlation between global aa-index and auroral occurrence number derived by Legrand & Simon. The linear correlation for the years 1914–1954 is +0.79.
RC4: "Mention in text and in caption what is the magnetic activity index used here."
Reply: The magnetic activity index is the annual mean of daily Ak number taken from the magnetic yearbooks of the SGO.
RC4 line 205. "Line 205. Mention which observatories."
Reply: The two temporary observatories during the Polar Year 1932-1933 were Petsamo (69.5°N; 31.2°E) near the coast of the Arctic Sea, now in the territory of Russia, and Kajaani in East-Finland (64.2°N; 27.7°E).
RC4: " Line 241-242. This is an odd sentence. Auroral occurrence studies are also part of auroral studies."
Reply: This sentence is now: Independent from auroral studies, Visual observations of the occurrence of auroras were made in connection with daily meteorological observations at the Sodankylä observatory since the founding of the observatory in 1914.
RC4: " Line 156. Ref to Fig. 5 must be earlier in text.
Reply: Corrected
RC4: " Line 254. It is multi-decadal, not decadal."
Reply. Ok. Corrected.
RC4: " Line 272. Write: auroras obtained almost one hundred years ago are the first ones in Finland."
Reply: Ok. Corrected
RC4: " References are relevant except for all the three papers by Tanskanen. Neither Tanskanen et al., 2005, nor Tanskanen, 2009, deals with auroral observations. "
Reply: Tanskanen et al. (2005) and Tanskanen (2009) found that the largest substorm numbers and peak amplitudes were found during the declining solar cycle phases. Their analysis was derived using magnetic data from the solar cycle 1993–2003. This similar to conclusion here that auroral occurrence rate is generally enhanced during the declining phase of a solar cycle.
RC4: " Tanskanen, 2022, is not even a scientific paper. "
Reply: Ok. This reference is deleted.
RC4: " The centennial increase in geomagnetic activity was found by Mayaud in 1972".
Reply: Yes. The reference Mayad (1972) is added in the reference list.
Mayaud, P.N.: The aa Indices: A 100-Year series characterizing the magnetic activity. Journal of Geophysical Research, 77, 6870–6874, https://doi.org/10.1029/JA077i034p06870, 1972.
Appendix A
_________________________________
Table 1a. Dates1 of available auroral photographs
at the SGO 1927–1929
________________________________________
Date Number of single photos
1927
Nov 18 24
Nov 19 6
Dec 13 33
Dec 14 3
Dec 18 6
Dec 28 42
1928
Jan 27 46
Mar 11 18
Mar 13 30
1929
Feb 27 18
Total 226
______________________________________
Table 1b. Dates1 of photographs lost
in the war 1944
______________________________________
Date Number of single photos
1928
Dec 6 9
1929
Jan 29 18
Feb 17 11
Feb 27 147
Mar 7 12
Mar 8 40
Mar 11 42
Mar 14 78
Mar 27 27
Total 384
_____________________________________
1 The data is based on original hand-written
notebooks by E. Sucksdorff
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AC5: 'Reply on AC4', H. Nevanlinna, 28 Feb 2024
The comment was uploaded in the form of a supplement: https://hgss.copernicus.org/preprints/hgss-2024-1/hgss-2024-1-AC5-supplement.pdf
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AC5: 'Reply on AC4', H. Nevanlinna, 28 Feb 2024
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AC7: 'Reply on RC4', H. Nevanlinna, 06 Mar 2024
Corrections to Fig. 6. (Magnetic storm Feb 27, 1929)
The corrected times (UT hh:mm:ss) for the six photographs and the exposure times (in brackets) are as follows:
1st row from left to right: 18:28:01 (16), 18:28:39 (8),
2nd row: 18:28:57 (11), 18:29:38 (11)
3rd row: 18:31:04 (9), 18:32:40 (12)
Total time 4 min 19 sec
Citation: https://doi.org/10.5194/hgss-2024-1-AC7
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AC4: 'Reply on RC4', H. Nevanlinna, 28 Feb 2024
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AC8: 'Comment on hgss-2024-1', H. Nevanlinna, 06 Mar 2024
I have replied to the questions and comments sent by the three referees. Is something still missing?
Citation: https://doi.org/10.5194/hgss-2024-1-AC8 -
AC9: 'Comment on hgss-2024-1', H. Nevanlinna, 18 Mar 2024
In the revised manuscript sent Mar 18 to HSGG blue lines are changes based on comments given by RC3, the red ones by RC4.
There are new text:
Lines 55–58 Lemström's contribution to Polar year results from Sodankylä 1882- 1884
Lines 223–239 concern Störmer's observations and photographs of the magnetic storm of 26–28 February, 1929
Lines 286–289 deal with observations of low altitude auroras by Störmer and E. Sucksdorff
New referencies are in red
Appendix A is completed by the dates of auroral photographs lost in the war 1944
Appendix B contains the numerical data depicted in Fig. 8
Citation: https://doi.org/10.5194/hgss-2024-1-AC9
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