Reconstruction of electron precipitation characteristics from a set of multiwavelength digital all‐sky auroral images

Janhunen, P.

doi:10.1029/2000ja000263

Cited by 26 publications

(33 citation statements)

References 18 publications

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“…(31) and (32) demonstrated by Murison et al (1985) for the KRM method. Two-dimensional ionospheric conductance distributions are quite difficult to obtain from direct measurements, but estimates may be derived from satellite or all-sky camera images and riometer data (e.g., Lummerzheim et al, 1991;Janhunen, 2001;Aksnes et al, 2005;Senior et al, 2008). However, these estimates rely on semi-empirical formulas that first relate optical emissions to the flux and characteristic energy of the precipitating electrons, which are then used to estimate the height-integrated conductances.…”

Section: Krm and Fac-based Electric Field Calculationmentioning

confidence: 99%

Analysis of ionospheric electrodynamic parameters on mesoscales – a review of selected techniques using data from ground-based observation networks and satellites

Vanhamäki

Amm

2011

Ann. Geophys.

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Abstract. We present a review of selected data-analysis methods that are frequently applied in studies of ionospheric electrodynamics and magnetosphere-ionosphere coupling using ground-based and space-based data sets. Our focus is on methods that are data driven (not simulations or statistical models) and can be used in mesoscale studies, where the analysis area is typically some hundreds or thousands of km across. The selection of reviewed methods is such that most combinations of measured input data (electric field, conductances, magnetic field and currents) that occur in practical applications are covered. The techniques are used to solve the unmeasured parameters from Ohm's law and Maxwell's equations, possibly with help of some simplifying assumptions. In addition to reviewing existing data-analysis methods, we also briefly discuss possible extensions that may be used for upcoming data sets.

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Section: Krm and Fac-based Electric Field Calculationmentioning

confidence: 99%

Analysis of ionospheric electrodynamic parameters on mesoscales – a review of selected techniques using data from ground-based observation networks and satellites

Vanhamäki

Amm

2011

Ann. Geophys.

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“…The capability of using ASC images for estimating the energy fluxes of precipitating electrons will open new possibilities in statistical studies of the magnetosphere-ionosphere coupling processes causing the visual aurora. Since the inversion method was first published by Janhunen (2001), an option for emission physics improvements (see Sect. 3.2) has been included in the inversion program.…”

Section: Introductionmentioning

confidence: 99%

“…The arc was located close to the zenith of ASC field-of-view at Kevo, while the FAST footpoint passed near Kilpisjärvi, on 3 November 1998 at 17:36 UT (Janhunen, 2001;Janhunen et al, 2000). Only green line images from the Kevo station were used in the inversion (no blue images were recorded at that time) and as the ASCs were not yet intensity calibrated an approximation of one digital unit corresponding to about 100 R was used.…”

Section: Introductionmentioning

confidence: 99%

“…Kirkwood, 1988). The inversion method by Janhunen (2001) uses multi-wavelength all-sky camera (ASC) images and solves both inversions as a single problem. The geometry and the emission physics are combined and, as a result, the electron differential number flux as a function of geographical latitude, longitude and precipitating energy is achieved.…”

Section: Introductionmentioning

confidence: 99%

“…An inversion method for reconstructing the precipitating electron energy flux from a set of multi-wavelength digital all-sky camera (ASC) images has recently been developed by Janhunen (2001). Preliminary tests suggested that the inversion is able to reconstruct the position and energy characteristics of the aurora with reasonable accuracy.…”

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Testing an inversion method for estimating electron energy fluxes from all-sky camera images

et al. 2004

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Abstract. An inversion method for reconstructing the precipitating electron energy flux from a set of multi-wavelength digital all-sky camera (ASC) images has recently been developed by Janhunen (2001). Preliminary tests suggested that the inversion is able to reconstruct the position and energy characteristics of the aurora with reasonable accuracy. This study carries out a thorough testing of the method and a few improvements for its emission physics equations.We compared the precipitating electron energy fluxes as estimated by the inversion method to the energy flux data recorded by the Defense Meteorological Satellite Program (DMSP) satellites during four passes over auroral structures. When the aurorae appear very close to the local zenith, the fluxes inverted from the blue (427.8 nm) filtered ASC images or blue and green line (557.7 nm) images together give the best agreement with the measured flux values. The fluxes inverted from green line images alone are clearly larger than the measured ones. Closer to the horizon the quality of the inversion results from blue images deteriorate to the level of the ones from green images. In addition to the satellite data, the precipitating electron energy fluxes were estimated from the electron density measurements by the EISCAT Svalbard Radar (ESR). These energy flux values were compared to the ones of the inversion method applied to over 100 ASC images recorded at the nearby ASC station in Longyearbyen. The energy fluxes deduced from these two types of data are in general of the same order of magnitude. In 35% of all of the blue and green image inversions the relative errors were less than 50% and in 90% of the blue and green image inversions less than 100%.This kind of systematic testing of the inversion method is the first step toward using all-sky camera images in the way in which global UV images have recently been used to estimate the energy fluxes. The advantages of ASCs, compared to the space-born imagers, are their low cost, good spatialCorrespondence to: N. Partamies (noora.partamies@fmi.fi) resolution and the possibility of continuous, long-term monitoring of the auroral oval from a fixed position.

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Incoherent scatter radar‐FAST satellite common volume observations of upflow‐to‐outflow conversion

Sánchez

Strømme

2014

JGR Space Physics

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Incoherent scatter radar measurements from the Sondrestrom Research Facility and the European Incoherent Scatter Svalbard radar have been combined with all-sky images, polar convection measurements, and FAST particle and field measurements to quantify the contribution of different magnetosphere-ionosphere coupling processes to the extraction efficiency of ions from the ionosphere. Upflowing ions are traced from their source vertically and horizontally to determine where and when they are likely to intersect the acceleration region observed by FAST. The duration and location of auroral emissions are used to estimate the size and duration of the acceleration region. The upflow-to-outflow efficiency is estimated for three periods of polar cap boundary intensifications and streamers during substorm recovery and steady magnetospheric convection. The extraction efficiency of conics ranges between 0.1%, for the lowest amplitude of broadband extremely low frequency waves, and 5%, for the highest-amplitude waves sampled. Simultaneous measurements of all-sky images and magnetic field-aligned radar measurements show that the most intense ion upflux occurs adjacent to the boundary of intense electron precipitation characteristic of polar cap boundary intensifications and streamers, suggesting that the most efficient acceleration mechanisms couple ionospheric heating at F region altitude with dispersive Alfvén waves that grow from horizontal gradients in electric field and conductivity.

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Reconstruction of electron precipitation characteristics from a set of multiwavelength digital all‐sky auroral images

Cited by 26 publications

References 18 publications

Analysis of ionospheric electrodynamic parameters on mesoscales – a review of selected techniques using data from ground-based observation networks and satellites

Analysis of ionospheric electrodynamic parameters on mesoscales – a review of selected techniques using data from ground-based observation networks and satellites

Testing an inversion method for estimating electron energy fluxes from all-sky camera images

Incoherent scatter radar‐FAST satellite common volume observations of upflow‐to‐outflow conversion

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