Data‐derived spatiotemporal resolution constraints for global auroral imagers

Uritsky, V. M.; Donovan, E.; Trondsen, T.; Pineau, Deanna; Kozelov, B. V.

doi:10.1029/2010ja015365

Cited by 12 publications

(24 citation statements)

References 17 publications

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“…The set of multi-scale Cassini observations analysed in this study shows that Saturn's aurora displays significant variability on all timescales, from minutes to hours, and on all spatial scales, from tens of km to several thousands of km, even during quiet solar wind conditions. Therefore, as is the case with Earth's aurora (Uritsky et al, 2010;Klimas et al, 2010), at Saturn we are also likely to find spatial and temporal variability on as small a spatial scale as we can observe. The fact that variability is also observed over long timescales, shows that the short-term variability is not merely stochastic, but forms part of an intricate and evolving system.…”

Section: Multi-scale Behavior Of the Main Aurora Ovalmentioning

confidence: 56%

Simultaneous multi-scale and multi-instrument observations of Saturn’s aurorae during the 2013 observing campaign

Melin

Stallard

Cowley

et al. 2016

Icarus

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On 21 April 2013, during a co-ordinated Saturn auroral observing campaign, the northern and southern poles of the planet were observed from the NASA Infrared Telescope Facility (IRTF), Keck, and Hubble Space Telescope (HST) simultaneously with the Cassini infrared, visible, and ultraviolet remote sensing instruments. We present simultaneous multi-scale and mutli-wavelength analysis of the morphology of auroral emissions at Saturn. There is variability on every spatial and temporal scale analysed, and high spatial resolution observations distinguish variable features with sizes tens of km on the planet.The fine scale temporal and spatial features seen in the main oval itself show that complex structures present even during quiet solar wind conditions. We observe diffuse ultraviolet emissions southward of the southern midnight main oval that are not seen in the infrared.This implies a steep temperature gradient, ∼60 K over 2-4 • latitude equator wad of the main oval. Lower spatial resolution observations reveal broad-scale dynamics at both poles, variable over minutes to hours, the morphology of which is only partly consistent with a overlapping local-time fixed and co-rotating current systems. We also present the first direct comparison of simultaneous infrared, visible, and ultraviolet auroral emissions at Saturn. These emissions are co-located, even though the spatial scale and operational mode of each instrument are very different.

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Section: Multi-scale Behavior Of the Main Aurora Ovalmentioning

confidence: 56%

Simultaneous multi-scale and multi-instrument observations of Saturn’s aurorae during the 2013 observing campaign

Melin

Stallard

Cowley

et al. 2016

Icarus

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“…On the other hand, simulation results reported by van Ballegooijen et al (2011) show that turbulent heating rate increases nonlinearly (almost quadratically) with the vorticity of the footpoint motion. If the vorticity is a function of spatial scale, which is typically the case in 2D and 3D hydrodynamic and MHD turbulence (Lundgren 1982;Gilbert 1993;Politano et al 1995;Jimenez et al 1996;Bouchet & Simonnet 2009;Servidio et al 2009;Uritsky et al 2010a), this dependence provides a natural scale-dependent driving mechanism across the inertial range of turbulent scales.…”

Section: Routes To Multiscale Dissipationmentioning

confidence: 99%

“…The approach is based on a spatiotemporal tracking algorithm (Uritsky et al 2007(Uritsky et al , 2010a) that identifies image features staying for more than one sampling interval above a specified detection threshold. The features are treated as subvolumes in the three-dimensional (3D) space time, with the time history of each feature represented by a set of spatially and temporally connected pixels.…”

Section: Event Detectionmentioning

confidence: 99%

Stochastic Coupling of Solar Photosphere and Corona

Uritsky¹,

Davila²,

Ofman³

et al. 2013

ApJ

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The observed solar activity is believed to be driven by the dissipation of nonpotential magnetic energy injected into the corona by dynamic processes in the photosphere. The enormous range of scales involved in the interaction makes it difficult to track down the photospheric origin of each coronal dissipation event, especially in the presence of complex magnetic topologies. In this paper, we propose an ensemble-based approach for testing the photosphere-corona coupling in a quiet solar region as represented by intermittent activity in Solar and Heliospheric Observatory Michelson Doppler Imager and Solar TErrestrial RElations Observatory Extreme Ultraviolet Imager image sets. For properly adjusted detection thresholds corresponding to the same degree of intermittency in the photosphere and corona, the dynamics of the two solar regions is described by the same occurrence probability distributions of energy release events but significantly different geometric properties. We derive a set of scaling relations reconciling the two groups of results and enabling statistical description of coronal dynamics based on photospheric observations. Our analysis suggests that multiscale intermittent dissipation in the corona at spatial scales >3 Mm is controlled by turbulent photospheric convection. Complex topology of the photospheric network makes this coupling essentially nonlocal and non-deterministic. Our results are in an agreement with the Parker's coupling scenario in which random photospheric shuffling generates marginally stable magnetic discontinuities at the coronal level, but they are also consistent with an impulsive wave heating involving multiscale Alfvénic wave packets and/or magnetohydrodynamic turbulent cascade. A back-reaction on the photosphere due to coronal magnetic reconfiguration can be a contributing factor.

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“…An observed characteristic increase in the scaling index can be interpreted as due to formation of "coarse-grained" transient structures in the system near (a bit over) self-organized critical (SOC) state (Uritsky et al, 2002(Uritsky et al, , 2006Kozelov et al, 2004;Klimas et al, 2010). Numerical models of substorm dynamics based on the SOC idea have been actively discussed in numerous papers (Consolini, 1997;Uritsky et al, 2001;Milovanov et al, 2001;Kozelov and Kozelova, 2002a,b,c;Klimas et al, 2010;Vallières-Nollet et al, 2010). Unfortunately, up to now, no self-consistent theory has been proposed that would entirely describe a connection between the observed dynamics of auroral structures and the processes in the central plasma sheet from where substorms are believed to originate.…”

Section: Discussionmentioning

confidence: 99%

Inverse cascade in the structure of substorm aurora and non-linear dynamics of field-aligned current filaments

2011

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Abstract.We investigate time evolution of scaling index α A that characterizes auroral luminosity fluctuations at the beginning of substorm expansion. With the use of UVI images from the Polar satellite, it is shown that α A typically varies from values less than unity to ∼1.5, increasing with breakup progress. Similar scaling features were previously reported for fluctuations at smaller scales from all-sky TV observations. If this signature is interpreted in terms of non-linear interactions between scales, it means that the power of smallscale fluctuations is transferred with time to larger scales, a kind of the inverse cascade. Scaling behavior in the aurora during substorm activity is compared with that in the fieldaligned currents simulated numerically in the model of nonlinear interactions of Alfvénic coherent structures, according to the Chang et al. (2004) scenario. This scenario also suggests an inverse cascade, manifesting in clustering of smallscale field-aligned current filaments of the same polarity and formation of "coarse-grained" structures of field-aligned currents.

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Data‐derived spatiotemporal resolution constraints for global auroral imagers

Cited by 12 publications

References 17 publications

Simultaneous multi-scale and multi-instrument observations of Saturn’s aurorae during the 2013 observing campaign

Simultaneous multi-scale and multi-instrument observations of Saturn’s aurorae during the 2013 observing campaign

Stochastic Coupling of Solar Photosphere and Corona

Inverse cascade in the structure of substorm aurora and non-linear dynamics of field-aligned current filaments

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