Features of stable diffuse arcs observed by means of auroral tomography

Abstract

Abstract. In this paper we study the spatial distribution of optical volume emission rates and peculiarities of the luminosity intensity within weak diffuse auroral arcs recovered by means of auroral tomography. The tomographic images are obtained from sets of scanning multi-channel photometer data obtained in February 1999 on the Kola Peninsula in Russia at three sites of a chain extending 226 km along the geomagnetic meridian. The 427.8-and 557.7-nm emissions of a 15-s time resolution observed within one hour during low geomagnetic activity are analyzed. We found that the intensity profile of an individual arc along the geomagnetic meridian has an inverted-V-shape. The luminosity maximum altitude decrease by 4-14 km at about 140 km distance in the south-north direction can be observed during two or more diffuse arcs. The parameters of the precipitating electron flux are obtained from an integral equation, which determines the best relationship between the 427.8-nm intensity height profile and an arbitrary particle energy spectrum. A dimensionless function of the energy dissipation is used as the core in the integral equation. The estimated average energy of electron flux, which generated the isolated diffuse arc, is 1-2 keV higher in the central part of the arc in comparison to values at its borders.

Ground-based observations of diffuse auroral structures in conjunction with Reimei measurements

“…Recently, however, there has been increased interest in understanding the diffuse auroral emissions (Horne et al, 2003;Dashkevich et al, 2007;Ni et al, 2008;Sergienko et al, 2008). In particular, periodically varying (spatially and temporally) structure within the diffuse aurora can be used to study wave activity (Johnstone et al, 1993; Correspondence to: M. Samara (msamara@swri.edu) Thorne, 2000;Meredith et al, 2000;Peticolas et al, 2002).…”

Feasibility study on Generalized-Aurora Computed Tomography

“…In this paper, we present the concrete algorithm of the G-ACT in detail, based on Aso et al (2008), and test the feasibility of this method by numerical simulation. We apply this method to some specific cases, in which we assume a simple but realistic electron energy distribution, station location, and observational noise.…”

“…Thus, it is possible for us to combine all these data to allow reconstruction of the precipitating electron flux. Aso et al (2008) have proposed a concept of a generalized tomographic inversion technique to reconstruct the differential flux of auroral precipitating electrons from multi-instrument data using a Bayesian model. We call this method as a GeneralizedAurora Computed Tomography (G-ACT).…”

“…), it is assumed that the wavelength of 427.8 nm is used for all the stations, because this wavelength corresponds to a simple emission process. The details of ALIS are described in Brändström (2003). The EISCAT UHF radar is assumed to be operating in CP1 mode, which measures plasma parameters along the geomagnetic field line direction from Tromsø (Elevation angle of 77.4 degrees and azimuth angle of 185.8 degrees).…”

“…In previous studies, the determination of the altitude of auroral emissions was performed by using a meridian scanning photometer chain or stereo TV cameras (Romick and Belon, 1967;Stenbaek-Nielsen and Halliman, 1979;Vallance Jones et al, 1991;Dashkevich et al, 2007). The tomographic inversion technique for aurora analysis has been developed with the construction of ground-based camera networks such as the Auroral Large Imaging System (ALIS) (Gustavsson, 1998;Brändström, 2003). In particular, algebraic reconstruction techniques (ARTs) such as MART (Muliplicative Algebraic552 Y.-M. Tanaka et al: Feasibility study on Generalized-Aurora Computed Tomography Reconstruction Technique) were often adopted for the reconstruction algorithm (Gordon et al, 1970;Tanabe 1971).…”