Spatial scaling of optical fluctuations during substorm-time aurora

Kozelov, B. V.; Rypdal, Kristoffer

doi:10.5194/angeo-25-915-2007

Cited by 17 publications

(15 citation statements)

References 28 publications

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“…This was previously reported by Kozelov and Rypdal (2007) by TV allsky observations. For larger spatial scales observed by the Polar UVI imager, a similar temporal variation of the roughness exponent of self-affine auroral surfaces was reported by Uritsky et al (2006).…”

Section: Introductionsupporting

confidence: 77%

“…2 above and in the previous studies (e.g. Uritsky et al, 2006;Kozelov and Rypdal, 2007), we conclude that the involved non-linear interactions between scales indicate an inverse energy cascade. In our study this is shown from examining time evolution of scaling index α A of auroral fluctuations at the beginning of substorm expansion by Polar imaging observations.…”

Section: Discussionmentioning

confidence: 71%

“…Oguti, 1975;Trondsen and Cogger, 1998). Later, scale-free statistics of the aurora was evidenced within frameworks of self-organized criticality and, alternatively, of intermittent turbulence that were invoked to Correspondence to: B. V. Kozelov (boris.kozelov@gmail.com) describe auroral dynamics as a manifestation of transients in the magnetosphere-ionosphere system (Uritsky et al, 2002;Kozelov, 2003;Kozelov et al, 2004;Kozelov and Rypdal, 2007;Klimas et al, 2010). In both approaches, power law distributions of various auroral characteristics over temporal and/or spatial scale, a signature of scale-independent regime, were stated.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionsupporting

confidence: 77%

Section: Discussionmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

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

2011

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“…There are many problems that remain open for future consideration. In particular, the assumption regarding the classical geometry (d = 2) of small-scale emission regions will need to be verified, especially for the range L < 100 km where fractal behavior of substorm time optical aurora has been documented [Kozelov and Rypdal, 2007]. The isotropic a is another ad hoc assumption requiring additional data validation and adjustment.…”

Section: Discussionmentioning

confidence: 99%

Data‐derived spatiotemporal resolution constraints for global auroral imagers

et al. 2010

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[1] We present new data-derived constraints on spatiotemporal resolution of global auroral imagers. The reported results are based on an extensive set of images from two previously flown instruments, POLAR UVI and IMAGE WIC, processed using the event detection methodology developed by Uritsky et al. (2002Uritsky et al. ( , 2003Uritsky et al. ( , 2006. We use the cross-scale analysis of ground-based and spacecraft observations of auroral emission regions by Kozelov et al. (2004) to derive the power law exponent relating spatial and temporal scales of auroral precipitation events, and estimate the normalization factor entering this relation using the satellite data. Our results show the existence of a nontrivial scaling relation between the relaxation time and the spatial dimension of auroral emission events. We use this relation as a proxi to the resolution scaling function providing non-redundant combinations of spatial and temporal resolution of an optimized auroral imager consistent with the dynamics of multiscale auroral precipitation.Citation: Uritsky, V. M., E. Donovan, T. Trondsen, D. Pineau, and B. V. Kozelov (2010), Data-derived spatiotemporal resolution constraints for global auroral imagers,

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“…In contrast to statistical approaches dealing with individual auroral images Kozelov and Rypdal, 2007), our study involved spatiotemporal tracking of emission events as briefly explained below. In most cases, this tracking made it possible to identify the precipitation events that co-evolved simultaneously in multiple auroral locations and could not be resolved otherwise (Uritsky et al, 2002).…”

Section: Detection Of Spatiotemporal Eventsmentioning

confidence: 99%

Collective dynamics of bursty particle precipitation initiating in the inner and outer plasma sheet

Uritsky

Donovan²,

Klimas³

et al. 2009

Ann. Geophys.

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Abstract.Using multiscale spatiotemporal analysis of bursty precipitation events in the nighttime aurora as seen by the POLAR UVI instrument, we report a set of new statistical signatures of high-and low-latitude auroral activity, signaling a strongly non-uniform distribution of dissipation mechanism in the plasma sheet. We show that small-scale electron emission events that initiate in the equatorward portion of the nighttime auroral oval (scaling mode A 1 ) have systematically steeper power-law slopes of energy, power, area, and lifetime probability distributions compared to the events that initiate at higher latitudes (mode B). The low-latitude group of events also contain a small but energetically important subpopulation of substorm-scale disturbances (mode A 2 ) described by anomalously low distribution exponents characteristic of barely stable thermodynamic systems that are prone to large-scale sporadic reorganization. The high latitude events (mode B) can be accurately described by a single set of distributions exponents over the entire range of studied scales, with the exponent values consistent with globally stable self-organized critical (SOC) behavior. The lowand high latitude events have distinct inter-trigger time statistics, and are characterized by significantly different MLT distributions. Based on these results we conjecture that the inner and outer portions of the plasma sheet are associated with two (or more) mechanisms of collective dynamics that may represent an interplay between current disruption and magnetic reconnection scenarios of bursty energy conversion in the magnetotail.

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Spatial scaling of optical fluctuations during substorm-time aurora

Cited by 17 publications

References 28 publications

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

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

Data‐derived spatiotemporal resolution constraints for global auroral imagers

Collective dynamics of bursty particle precipitation initiating in the inner and outer plasma sheet

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