World first complex optical instrumental observations of aurora in the Arctic in 1899?1900

International audienceThis report presents data and analysis of visual, photographic and auroral spectral data, obtained by the Russian astronomer J. Sykora from the Russian-Swedish expedition to Spitsbergen during the 1899?1900 winter season, which are historically significant for auroral studies. These data seem to be the first instrumental observations of auroral spectra in the Arctic and some of the emissions discovered have world priority. The second known photos in the world of aurora from the Arctic and undoubtedly the first ones for geomagnetic latitudes of about 75° in the Spitsbergen Archipelago were obtained. The results of the expedition are discussed from a modern point of view and compared with our knowledge of the 21st century. A description of the equipment and methods that were used by Russian astronomers is presented. Both photographic and spectral devices using registration by photographic plates were used, along with special methods of their development and enhancement. Some statistical analysis was done on the basis of the expedition reports and diaries. This analysis shows that by using Sykora's data it was possible to discover the auroral oval or instantaneous auroral distribution over the polar region. Analysis of photographic samples and sketches of the aurora demonstrate typical auroral form outlines as they are described today. Spectral plates exposed for several hours to auroral lights revealed not only the main auroral emissions, which were well-known at that time, but several other unidentified weak emissions, which were rediscovered and interpreted years later. Keywords. History of geophysics (Atmospheric sciences, instruments and techniques

Variations of auroral hydrogen emission near substorm onset

The results of coordinated optical ground-based observations of the auroral substorm on 26 March 2004 in the Kola Peninsula are described. Imaging spectrograph data with high spectral and temporal resolution recorded the Doppler profile of the Hα hydrogen emission; this allows us to estimate the average energy of precipitating protons and the emission intensity of the hydrogen Balmer line. Two different populations of precipitating protons were observed during an auroral substorm. The first of these is associated with a diffuse hydrogen emission that is usually observed in the evening sector of the auroral oval and located equatorward of the discrete electron arcs associated with substorm onset. The average energy of the protons during this precipitation was ~20–35 keV, and the energy flux was ~3x10<sup>–4</sup>Joule/m<sup>2</sup>s. The second proton population was observed 1–2min after the breakup during 4–5min of the expansion phase of substorm into the zone of bright, discrete auroral structures (N-S arcs). The average energy of the protons in this population was ~60 keV, and the energy flux was ~2.2x10<sup>–3</sup>Joule/m<sup>2</sup>s. The observed spatial structure of hydrogen emission is additional evidence of the higher energy of precipitated protons in the second population, relative to the protons in the diffuse aurora. We believe that the most probable mechanism of precipitation of the second population protons was pitch-angle scattering of particles due to non-adiabatic motion in the region of local dipolarization near the equatorial plane.<p><b>Keywords.</b> Auroral ionosphere; Particle precipitation; Storms and substorm

Results from the intercalibration of optical low light calibration sources 2011

Following the 38th Annual European Meeting on Atmospheric Studies by Optical Methods in Siuntio in Finland, an intercalibration workshop for optical low light calibration sources was held in Sodankylä, Finland. The main purpose of this workshop was to provide a comparable scale for absolute measurements of aurora and airglow. All sources brought to the intercalibration workshop were compared to the Fritz Peak reference source using the Lindau Calibration Photometer built by Wilhelm Barke and Hans Lauche in 1984. The results were compared to several earlier intercalibration workshops. It was found that most sources were fairly stable over time, with errors in the range of 5–25%. To further validate the results, two sources were also intercalibrated at UNIS, Longyearbyen, Svalbard. Preliminary analysis indicates agreement with the intercalibration in Sodankylä within about 15–25%

Comparison and significance of auroral studies during the Swedish and Russian bilateral expedition to Spitsbergen in 1899–1900

Results of measurements and visual observations of aurora at Spitsbergen, carried out by the joint Swedish-Russian expedition during 1899–1900, are described. Auroral observations took place during the great bilateral Arc-of-Meridian expedition, which was patronized by the Swedish Royal Family and the Russian Imperial Family. The Russian-Swedish Arc-of-Meridian measurements were closely coordinated but auroral measurements from the two sites in the Spitsbergen Archipelago were almost independent of each other. The basic auroral data for our presentation are reports of the Russian astronomer Josef Sykora and the Swedish geophysicist Jonas Westman. Both scientists used similar types of photo cameras and spectrographs, which were the best at that time and were made in Potsdam by Toepfer. Detailed descriptions of the optical devices and the system of spectral calibration are presented. A Toepfer spectrograph, possibly the one used by Westman, is still kept at IRF in Kiruna. We present a comparative analysis of auroral data from the Russian and Swedish stations on three themes: visual observations of aurora, describing features of auroral forms and giving us statistical data on aurora occurrence and the heights of aurora, photos of aurora, and auroral spectra. It is shown that the observations contain enough data to construct an auroral oval and to determine the heights of aurora. The expedition obtained the first photographic observations of the aurora in the Arctic. The auroral spectra demonstrate a high spectral resolution and show not only the main auroral emissions in the blue-green spectral range but also some weak emissions in the violet and ultraviolet region. All data are interpreted from a modern point of view. The Russian-Swedish 1899–1900 expedition carried out the first complex auroral investigations in the Arctic using optical instruments and presented well documented data and new results

World first complex optical instrumental observations of aurora in the Arctic in 1899−1900

This report presents data and analysis of visual, photographic and auroral spectral data, obtained by the Russian astronomer J. Sykora from the Russian-Swedish expedition to Spitsbergen during the 1899–1900 winter season, which are historically significant for auroral studies. These data seem to be the first instrumental observations of auroral spectra in the Arctic and some of the emissions discovered have world priority. The second known photos in the world of aurora from the Arctic and undoubtedly the first ones for geomagnetic latitudes of about 75° in the Spitsbergen Archipelago were obtained. The results of the expedition are discussed from a modern point of view and compared with our knowledge of the 21st century. A description of the equipment and methods that were used by Russian astronomers is presented. Both photographic and spectral devices using registration by photographic plates were used, along with special methods of their development and enhancement. Some statistical analysis was done on the basis of the expedition reports and diaries. This analysis shows that by using Sykora's data it was possible to discover the auroral oval or instantaneous auroral distribution over the polar region. Analysis of photographic samples and sketches of the aurora demonstrate typical auroral form outlines as they are described today. Spectral plates exposed for several hours to auroral lights revealed not only the main auroral emissions, which were well-known at that time, but several other unidentified weak emissions, which were rediscovered and interpreted years later. Keywords. History of geophysics (Atmospheric sciences, instruments and techniques