Feasibility study on Generalized-Aurora Computed Tomography

Tanaka, Yoshimasa; Asô, T.; Gustavsson, B.; Tanabe, Kunio; Ogawa, Y.; Kadokura, Akira; Miyaoka, Hiroshi; Sergienko, T.; Brändström, Urban; Sandahl, I.

doi:10.5194/angeo-29-551-2011

Cited by 19 publications

(35 citation statements)

References 25 publications

(21 reference statements)

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“…For this campaign, four CCD imagers of the Auroral Large Imaging System (ALIS) (Brändström 2003), two all-sky electron-multiplying CCD (EMCCD) imagers of the MIR-ACLE network (Syrjäsuo et al 1998;Sangalli et al 2011), and an all-sky EMCCD imager and all-sky Watec imagers (AWIs) installed at the EISCAT radar site in Tromsø (TRO), Norway, by the NIPR (Ogawa et al 2013) were operated. The goal of this campaign was to reconstruct the three-dimensional (3D) distribution of the auroral emission and horizontal distribution of the energy spectra of precipitating electrons from the multiple auroral images using the tomographic inversion technique (Aso et al 1998;Gustavsson 1998;Tanaka et al 2011). In this paper, however, we focus on the characteristics of three auroral surges observed during the substorm on March 8-9, 2013.…”

Section: Methodsmentioning

confidence: 99%

Eastward-expanding auroral surges observed in the post-midnight sector during a multiple-onset substorm

et al. 2015

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We present three eastward-expanding auroral surge (EEAS) events that were observed intermittently at intervals of about 15 min in the post-midnight sector (01:55-02:40 MLT) by all-sky imagers and magnetometers in northern Europe. It was deduced that each surge occurred just after each onset of a multiple-onset substorm, which was small-scale and did not clearly expand westward, because they were observed almost simultaneously with Pi 2 pulsations at the magnetic equator and magnetic bay variations at middle-to-high latitudes associated with the DP-1 current system. The EEASs showed similar properties to omega bands or torches reported in previous studies, such as recurrence intervals of about 15 min, concurrence with magnetic pulsations with amplitudes of several tens of nanotesla, horizontal scales of 300-400 km, and occurrence of a pulsating aurora in a diffuse aurora after the passage of the EEASs. Furthermore, the EEASs showed similar temporal evolution to the omega bands, during which eastward-propagating auroral streamers occurred simultaneously in the poleward region, followed by the formation of north-south-aligned auroras, which eventually connected with the EEASs. Thus, we speculate that EEASs may be related to the generation process of omega bands. On the other hand, the EEASs we observed had several properties that were different from those of omega bands, such as greater eastward propagation speed (3-4 km/s), shorter associated magnetic pulsation periods (4-6 min), and a different ionospheric equivalent current direction. The fast eastward propagation speed of the EEASs is consistent with the speed of eastward expansion fronts of the substorm current wedge reported in previous studies. The difference in the ionospheric current between the EEASs and omega bands may be caused by a large temporal variation of the surge structure, compared with the more stable wavy structure of omega bands.

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Section: Methodsmentioning

confidence: 99%

Eastward-expanding auroral surges observed in the post-midnight sector during a multiple-onset substorm

et al. 2015

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“…The inversion technique has been developed with the construction of ground-based camera networks such as the Aurora Large Imaging System (ALIS) (Steen and Brändström, 1993;Gustavsson, 1998). Tanaka et al (2011) recently developed a new method of generalized ACT (GACT) that reconstructs the energy and spatial distributions of precipitating electrons from multi-instrument data. Suitably separated ground-based imaging systems, with a separation distance of several tens of km, can now therefore be thought of as a single "meta-instrument" accessing a dimension which cannot be resolved through a single-site measurement.…”

Section: Published By Copernicus Publications On Behalf Of the Europementioning

confidence: 99%

Stereoscopic determination of all-sky altitude map of aurora using two ground-based Nikon DSLR cameras

et al. 2013

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A new stereoscopic measurement technique is developed to obtain an all-sky altitude map of aurora using two ground-based digital single-lens reflex (DSLR) cameras. Two identical full-color all-sky cameras were set with an 8 km separation across the Chatanika area in Alaska (Poker Flat Research Range and Aurora Borealis Lodge) to find localized emission height with the maximum correlation of the apparent patterns in the localized pixels applying a method of the geographical coordinate transform. It is found that a typical ray structure of discrete aurora shows the broad altitude distribution above 100 km, while a typical patchy structure of pulsating aurora shows the narrow altitude distribution of less than 100 km. Because of its portability and low cost of the DSLR camera systems, the new technique may open a unique opportunity not only for scientists but also for night-sky photographers to complementarily attend the aurora science to potentially form a dense observation network

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“…[105] Finally, Tanaka et al [2011] made a general contribution to multi-instrumental data sets to build a strategy to exploit in unison existing and future 3-D observatories such as ALIS and the incoming incoherent scatter radar EISCAT_3D in Northern Scandinavia.…”

Section: Appendix A: Main Results With Alismentioning

confidence: 99%

“…[106] Acknowledgments. This article is dedicated to Ingrid Sandahl (1949-2011, who was the inspiration and principal investigator of ALIS. She will be deeply missed.…”

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confidence: 99%

Estimating energy spectra of electron precipitation above auroral arcs from ground‐based observations with radar and optics

et al. 2013

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[1] In 2008, coordinated radar-optical auroral observations were organized in Northern Scandinavia using the European Incoherent Scatter Radar (EISCAT) and the Auroral Large Imaging System (ALIS). A bright auroral arc was imaged on 5 March 2008 from four ground-based stations, remaining stable between 18:41 and 18:44 UT and coinciding with increased electron densities. This work presents a unified inversion framework deriving the electron energy spectrum from either optical (N + 2 1NG(0, 1) emission at 4278 Å) or radar (electron density) observations. An updated forward model of the ionosphere based on a 1-D kinetic Monte Carlo model is described, characterizing the linear system to invert. The 3-D blue volume emission rate is first estimated with an iterative reconstruction technique. Also presented is a novel way to calculate an accurate initial guess for auroral tomography taking into account the horizontal/vertical nonuniformity of the emission region. This technique supersedes the often-used Chapman profile as initial guess when high spatial resolution is needed. The second step, performed for the first time with ALIS optical observations, uses the forward model to retrieve from the emission rates the 2-D latitude/longitude map of the electron energy spectrum. The same model and inversion methods are finally applied to the EISCAT electron density profiles to derive the temporal energy spectrum of precipitating electrons along the magnetic zenith. Energy spectra from radar and optics are in good agreement. Results suggest that the arc is generated by a complex energy spectrum reminiscent of dispersive Alfvén waves with two main peaks (2.5, 6 keV) and a typical latitudinal width of 7.5 km.Citation: Simon Wedlund, C., H. Lamy, B. Gustavsson, T. Sergienko, and U. Brändström (2013), Estimating energy spectra of electron precipitation above auroral arcs from ground-based observations with radar and optics,

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Feasibility study on Generalized-Aurora Computed Tomography

Cited by 19 publications

References 25 publications

Eastward-expanding auroral surges observed in the post-midnight sector during a multiple-onset substorm

Eastward-expanding auroral surges observed in the post-midnight sector during a multiple-onset substorm

Stereoscopic determination of all-sky altitude map of aurora using two ground-based Nikon DSLR cameras

Estimating energy spectra of electron precipitation above auroral arcs from ground‐based observations with radar and optics

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