We have recently installed a low-light-level, all-sky-imager (ASI) at the astronomical observatory in Asiago, Italy (45.8 N, 11.5 E, 41 N geomagnetic). The field-of-view for such a system can yield reliable observations from zenith down to about five degrees elevation angle. Atmospheric emissions arise from different altitudes and thus the spatial region observed by an ASI depends on the specific wavelength (and process) involved. For 6300 A emissions from atomic oxygen, diffuse aurora occur at ~200 km, ambient airglow at ~300 km and so-called Stable Auroral Red (SAR) arcs at ~400 km. From the Asiago site, the FOV at 400 km spans latitudes extending from southern Scandanavia to Northern Africa. For a magnetic latitude of 50 N, longitudes observed to the north extend from Ireland to Belarus. For a magnetic latitude of 30 N, longitudes to the south can be observed from Spain to Turkey. The SAR arc that occurred during the geomagnetic storm 26-27 September 2011 was, we think, the first-ever such event imaged from the ground in Europe. The SAR arc’s location throughout the night maps to the inner magnetosphere where the plasmapause and inner edge of the ring current coincide. The spatial-temporal positions of these features determine the lowest latitudes of magnetosphere-ionospheric energy input during space weather events. We show that an all-sky-imager can thus be used to provide real-time information of this boundary over most of Europe—and thus the low-latitude limit of the radiowave scintillations associated with SAR arcs. Moreover, such information can be used for retrospective validations of global models that predict the latitude extent of space weather effects.
Imaging Space Weather Over Europe from a Single Site
MENDILLO, MICHAEL JOSEPH;Barbieri C.;Umbriaco G.
2012
Abstract
We have recently installed a low-light-level, all-sky-imager (ASI) at the astronomical observatory in Asiago, Italy (45.8 N, 11.5 E, 41 N geomagnetic). The field-of-view for such a system can yield reliable observations from zenith down to about five degrees elevation angle. Atmospheric emissions arise from different altitudes and thus the spatial region observed by an ASI depends on the specific wavelength (and process) involved. For 6300 A emissions from atomic oxygen, diffuse aurora occur at ~200 km, ambient airglow at ~300 km and so-called Stable Auroral Red (SAR) arcs at ~400 km. From the Asiago site, the FOV at 400 km spans latitudes extending from southern Scandanavia to Northern Africa. For a magnetic latitude of 50 N, longitudes observed to the north extend from Ireland to Belarus. For a magnetic latitude of 30 N, longitudes to the south can be observed from Spain to Turkey. The SAR arc that occurred during the geomagnetic storm 26-27 September 2011 was, we think, the first-ever such event imaged from the ground in Europe. The SAR arc’s location throughout the night maps to the inner magnetosphere where the plasmapause and inner edge of the ring current coincide. The spatial-temporal positions of these features determine the lowest latitudes of magnetosphere-ionospheric energy input during space weather events. We show that an all-sky-imager can thus be used to provide real-time information of this boundary over most of Europe—and thus the low-latitude limit of the radiowave scintillations associated with SAR arcs. Moreover, such information can be used for retrospective validations of global models that predict the latitude extent of space weather effects.
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