Alfvénic turbulence in high speed solar wind streams as a driver for auroral activity

D’Amicis, R.; Bruno, R.; Bavassano, B.

doi:10.1016/j.jastp.2008.05.002

Cited by 11 publications

(10 citation statements)

References 42 publications

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“…Notably absent in this study are (1) solar wind variables related to the amplitude of fluctuations in the solar wind magnetic field, velocity, number density, and ram pressure and (2) solar wind variables related to the nature of the fluctuations in the solar wind such as the Alfvenicity, the Alfven ratio, and the intermittencies. In several studies the amplitudes of solar wind fluctuations have been found to correlate with geomagnetic activity (Borovsky, ; Borovsky & Funsten, ; D'Amicis et al, , , ; Osmane et al, ) and magnetospheric ULF waves are believed to be driven by temporal variations in the solar wind ram pressure (Berube et al, ; Eriksson et al, ; Kepko et al, ; Liu et al, ; Viall et al, ). Also absent in this study is the alpha‐to‐proton density ratio α / p of the solar wind, which the authors have found to be, in general, unreliable when various α / p data sets are compared with each other (e.g., Figure 7e of Borovsky, )…”

Section: Data Sets and Methodsmentioning

confidence: 99%

“…In several studies the amplitudes of solar wind fluctuations have been found to correlate with geomagnetic activity (Borovsky, 2006;Borovsky & Funsten, 2003;D'Amicis et al, 2007D'Amicis et al, , 2009D'Amicis et al, , 2011Osmane et al, 2015) and magnetospheric ULF waves are believed to be driven by temporal variations in the solar wind ram pressure (Berube et al, 2014;Eriksson et al, 2006;Kepko et al, 2002;Liu et al, 2010;Viall et al, 2009). Also absent in this study is the alpha-to-proton density ratio α/p of the solar wind, which the authors have found to be, in general, unreliable when various α/p data sets are compared with each other (e.g., Figure 7e of Borovsky, 2016) Linear correlations are performed between the left-hand side and right-hand side of formulas (cf.…”

Section: Finally Inmentioning

confidence: 99%

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Time‐Integral Correlations of Multiple Variables With the Relativistic‐Electron Flux at Geosynchronous Orbit: The Strong Roles of Substorm‐Injected Electrons and the Ion Plasma Sheet

Borovsky

2017

JGR Space Physics

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Time‐integral correlations are examined between the geosynchronous relativistic electron flux index Fe1.2 and 31 variables of the solar wind and magnetosphere. An “evolutionary algorithm” is used to maximize correlations. Time integrations (into the past) of the variables are found to be superior to time‐lagged variables for maximizing correlations with the radiation belt. Physical arguments are given as to why. Dominant correlations are found for the substorm‐injected electron flux at geosynchronous orbit and for the pressure of the ion plasma sheet. Different sets of variables are constructed and correlated with Fe1.2: some sets maximize the correlations, and some sets are based on purely solar wind variables. Examining known physical mechanisms that act on the radiation belt, sets of correlations are constructed (1) using magnetospheric variables that control those physical mechanisms and (2) using the solar wind variables that control those magnetospheric variables. Fe1.2‐increasing intervals are correlated separately from Fe1.2‐decreasing intervals, and the introduction of autoregression into the time‐integral correlations is explored. A great impediment to discerning physical cause and effect from the correlations is the fact that all solar wind variables are intercorrelated and carry much of the same information about the time sequence of the solar wind that drives the time sequence of the magnetosphere.

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Section: Data Sets and Methodsmentioning

confidence: 99%

Section: Finally Inmentioning

confidence: 99%

Time‐Integral Correlations of Multiple Variables With the Relativistic‐Electron Flux at Geosynchronous Orbit: The Strong Roles of Substorm‐Injected Electrons and the Ion Plasma Sheet

Borovsky

2017

JGR Space Physics

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“…The dayside magnetic reconnection leads to nightside reconnection and plasma injections into the midnight sector of the magnetosphere (DeForest & McIlwain, 1971). In HSSs where there is a high level of this Alfvénic turbulence, magnetic reconnection can occur almost continuously for days or even weeks (D'Amicis et al, 2007(D'Amicis et al, , 2009(D'Amicis et al, , 2010Gonzalez et al, 2006;Guarnieri, 2006;Hajra et al, 2013;Kozyra et al, 2006;Tsurutani, Gonzalez, et al, 1995;Tsurutani et al, 2006;Tsurutani & Gonzalez, 1987;Turner et al, 2006). These intervals of Alfvénic turbulence and high geomagnetic activity have been called High-Intensity Long-Duration Continuous AE Activity (HILDCAA) intervals.…”

Section: Alfvénic Turbulence Effects On Geomagnetic Activity and The mentioning

confidence: 99%

A Review of Alfvénic Turbulence in High‐Speed Solar Wind Streams: Hints From Cometary Plasma Turbulence

et al. 2018

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Solar wind turbulence within high‐speed streams is reviewed from the point of view of embedded single nonlinear Alfvén wave cycles, discontinuities, magnetic decreases (MDs), and shocks. For comparison and guidance, cometary plasma turbulence is also briefly reviewed. It is demonstrated that cometary nonlinear magnetosonic waves phase‐steepen, with a right‐hand circular polarized foreshortened front and an elongated, compressive trailing edge. The former part is a form of “wave breaking” and the latter that of “period doubling.” Interplanetary nonlinear Alfvén waves, which are arc polarized, have a ~180° foreshortened front and with an elongated trailing edge. Alfvén waves have polarizations different from those of cometary magnetosonic waves, indicating that helicity is a durable feature of plasma turbulence. Interplanetary Alfvén waves are noted to be spherical waves, suggesting the possibility of additional local generation. They kinetically dissipate, forming MDs, indicating that the solar wind is partially “compressive” and static. The ~2 MeV protons can nonresonantly interact with MDs leading to rapid cross‐field (~5.5% Bohm) diffusion. The possibility of local (~1 AU) generation of Alfvén waves may make it difficult to forecast High‐Intensity, Long‐Duration AE Activity and relativistic magnetospheric electrons with great accuracy. The future Solar Orbiter and Solar Probe Plus missions should be able to not only test these ideas but to also extend our knowledge of plasma turbulence evolution.

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“…It has been established that when the solar wind magnetic field is northward (wherein the viscous interaction should dominate over the reconnection interaction), the level of geomagnetic activity is controlled to some degree by the amplitude of magnetic field fluctuations in the upstream solar wind [ Borovsky and Gosling , ; Borovsky and Funsten , ; Borovsky and Steinberg , ; Borovsky , , D ' Amicis et al ., , , , ; Lyons et al ., ; Kim et al ., ]. Borovsky and Funsten [] tested this observationally being careful to reduce the effect of solar wind turbulence amplitude acting as a proxy for other solar wind parameters.…”

Section: The Viscous Interactionmentioning

confidence: 99%

Physics‐based solar wind driver functions for the magnetosphere: Combining the reconnection‐coupled MHD generator with the viscous interaction

Borovsky

2013

JGR Space Physics

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[1] Driver functions for the Earth's magnetosphere-ionosphere system are derived from physical principles. Two processes act simultaneously: a reconnection-coupled MHD generator  and a viscous interaction.  accounts for the dayside reconnection rate, the length of the reconnection X line, and current saturation limits for the solar wind generator. Two viscous drivers are derived: Bohm viscosity ℬ and the freestream-turbulence effect  . A problematic proxy effect is uncovered wherein the viscous driver functions also describe the strength of reconnection. Two magnetospheric-driver functions written in terms of upstream solar wind parameters are constructed:  + ℬ and  +  . The driver functions are tested against seven geomagnetic indices. The reaction of the geomagnetic indices to  + ℬ and  +  is nonlinear: Nonlinear versions of the driver functions are supplied. Applying the driver functions at multiple time steps yields correlation coefficients of~85% with the AE and Kp indices; it is argued that multiple time stepping removes high-frequency uncorrelated signal from the drivers. Autocorrelation-function analysis shows strong 1 day and 1 year periodicities in the AE index, which are not in the solar wind driver functions; correspondingly, high-pass and low-pass filtering finds uncorrelated signal at 1 day and 1 year timescales. Residuals (unpredicted variance) between the geomagnetic indices and the driver functions are analyzed: The residuals are anticorrelated with the solar wind velocity, the solar F 10.7 radio flux, and the solar wind current saturation parameter. Removing diurnal, semiannual, and annual trends from the indices improves their correlation with the solar wind driver functions. Simplified versions of the driver functions are constructed: The simplified drivers perform approximately as well as the full drivers.

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Alfvénic turbulence in high speed solar wind streams as a driver for auroral activity

Cited by 11 publications

References 42 publications

Time‐Integral Correlations of Multiple Variables With the Relativistic‐Electron Flux at Geosynchronous Orbit: The Strong Roles of Substorm‐Injected Electrons and the Ion Plasma Sheet

Time‐Integral Correlations of Multiple Variables With the Relativistic‐Electron Flux at Geosynchronous Orbit: The Strong Roles of Substorm‐Injected Electrons and the Ion Plasma Sheet

A Review of Alfvénic Turbulence in High‐Speed Solar Wind Streams: Hints From Cometary Plasma Turbulence

Physics‐based solar wind driver functions for the magnetosphere: Combining the reconnection‐coupled MHD generator with the viscous interaction

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