Preprints
https://doi.org/10.5194/hgss-2023-14
https://doi.org/10.5194/hgss-2023-14
15 Jan 2024
 | 15 Jan 2024
Status: this preprint is currently under review for the journal HGSS.

Conjugate Aurora Observations by the Gjøa and Discovery Expeditions

Alv Egeland

Abstract. During 1901 to 1912 – known as the ‘heroic period’ of Arctic and Antarctic exploration, great inroads were made not only geographic but also scientific to our knowledge of the continent. At Amundsen’s Expedition through the Northwest Passage measurements of the geomagnetic field and visual auroras were carried out for 19 months at Gjøahavn (geographic coordinates 68° 37’ 10’’ North (N); 95° 53’ 25’’West (W). Scott’s Discovery Expeditionat Cape Armitage, McMurdo (coordinates 77.86° S; 166.69° E), Antarctica, carried out same type of measurements. Their observations were carried out geomagnetically conjugate to Gjøahavn. In addition, measurements were overlapping in time during the year 1903–04. However, these two stations are located at different longitudes so there is a difference in local time between the stations of about 6 hours. Gjøahavn and Cape Armitage are conveniently located for separating disturbances in the polar cap regions caused by solar electromagnetic radiations or solar wind.

The observations were carried out for seven moths per year. This gave a unique possibility to compare conjugate characteristics of polar cap auroras. Comparing conjugate geophysical data introduce some difficulties. During the winter season at Gjøahavn, they had bright summer in Antarctica, and vis versa. Thus, simultaneous temporal, and spatial ionospheric variations can be marked different. Still, the diurnal and seasonal variations were similar. The quantity of the data from Cape Armitage was larger because there they had continuous watch of the sky.

The main findings regarding polar cap auroras are:

Low intensity bands – also called streamers, are the dominating form. The number of events in 1903 was nearly twice that in 1902 and 1904. A marked midwinter maximum was observed at both stations. Many displays were observed poleward of the oval. A large fraction was associated with weak magnetic disturbances.

The polar cap auroral forms: Theta arcs, poleward moving substorm arcs (PSA), and transpolar arcs (TA), have special geomagnetic signatures, so they can be mapped even if they are not observed visual. According to recent satellite measurements they are probably caused by polar rain and/or photoelectrons.

Alv Egeland

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hgss-2023-14', Anonymous Referee #1, 22 Jan 2024
  • CC1: 'Comment on hgss-2023-14', Fred Sigernes, 30 Jan 2024
  • RC2: 'Comment on hgss-2023-14', Anonymous Referee #2, 07 Feb 2024
Alv Egeland
Alv Egeland

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Short summary
Contemporary analysis of Amundsen’s 120 years old auroral measurements at Gjøahavn carried out simultaneous with Scott’s recordings at Cape Armitage. These observatories are geomagnetically conjugate and located poleward of the auroral oval. All auroral events was associated with weak magnetic disturbances. Maximum activity occurred midwinter. Theta arcs, poleward moving substorm arcs, and transpolar arcs dominated the polar cap. These forms have special magnetic signatures.