Solar wind control of auroral Alfvénic power generated in the magnetotail

Zhang, Binzheng; Lotko, W.; Brambles, O. J.; Xi, Sheng; Wiltberger, M. J.; Lyon, J. G.

doi:10.1002/2013ja019178

Cited by 20 publications

(39 citation statements)

References 53 publications

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“…The simulated hemispheric broadband power increases similarly with d Φ MP /d t but with relatively large scatter. The large scatter in the simulated broadband power may be related to a significant IMF B y in the driving condition [ Zhang et al , ]. Overall, the linear fit of the scattered data points is approximately consistent with the OVATION Prime model as suggested also by the ideal test simulations discussed in section 4.1.…”

Section: Model Comparisonssupporting

confidence: 69%

Electron precipitation models in global magnetosphere simulations

et al. 2015

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General methods for improving the specification of electron precipitation in global simulations are described and implemented in the Lyon-Fedder-Mobarry (LFM) global simulation model, and the quality of its predictions for precipitation is assessed. LFM's existing diffuse and monoenergetic electron precipitation models are improved, and new models are developed for lower energy, broadband, and direct-entry cusp precipitation. The LFM simulation results for combined diffuse plus monoenergetic electron precipitation exhibit a quadratic increase in the hemispheric precipitation power as the intensity of solar wind driving increases, in contrast with the prediction from the OVATION Prime (OP) 2010 empirical precipitation model which increases linearly with driving intensity. Broadband precipitation power increases approximately linearly with driving intensity in both models. Comparisons of LFM and OP predictions with estimates of precipitating power derived from inversions of Polar satellite UVI images during a double substorm event (28-29 March 1998) show that the LFM peak precipitating power is > 4× larger when using the improved precipitation model and most closely tracks the larger of three different inversion estimates. The OP prediction most closely tracks the double peaks in the intermediate inversion estimate, but it overestimates the precipitating power between the two substorms by a factor >2 relative to all other estimates. LFMs polar pattern of precipitating energy flux tracks that of OP for broadband precipitation exhibits good correlation with duskside region 1 currents for monoenergetic energy flux that OP misses and fails to produce sufficient diffuse precipitation power in the prenoon quadrant that is present in OP. The prenoon deficiency is most likely due to the absence of drift kinetic physics in the LFM simulation.

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Section: Model Comparisonssupporting

confidence: 69%

Electron precipitation models in global magnetosphere simulations

et al. 2015

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“…Chaston et al [2007] and Zhang et al [2014] showed that Alfvénic Poynting flux convergence in the premidnight regime is several times more energetic than on the dayside and that this pattern also appears in the energetic electron fluxes. Chaston et al [2007] and Zhang et al [2014] showed that Alfvénic Poynting flux convergence in the premidnight regime is several times more energetic than on the dayside and that this pattern also appears in the energetic electron fluxes.…”

Section: Relationship Between Eof3 and Alfvén Poynting Fluxmentioning

confidence: 98%

“…We take the next step in 3-D exploration of the ionosphere by presenting the first objective characterization of the primary modes of variability of E region, height-dependent conductivities over the entire polar region using spectrally resolved in situ particle measurements from the Special Sensor J (SSJ) instrument on board the F6-F8 and F16-F18 Defense Meteorological Satellite Program (DMSP) satellites. The third mode seems to capture the conductivity effects of Alfvénic Poynting flux-driven broadband electron precipitation in the premidnight and in regions flanking the noon local time (LT) sectors [Keiling et al, 2003;Chaston et al, 2007;Zhang et al, 2014]. The first mode captures variability associated with diffuse precipitation [Newell et al, 2009].…”

Section: Introductionmentioning

confidence: 99%

High‐latitude ionospheric conductivity variability in three dimensions

McGranaghan

Knipp

Matsuo

2016

Geophysical Research Letters

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We perform the first ever global‐scale, altitude‐dependent analysis of polar ionospheric conductivity variability using spectrally resolved in situ satellite particle measurements. With an empirical orthogonal function analysis we identify three primary modes of three‐dimensional variability related to ionospheric footprints of the quiet and disturbed geospace environment: (1) perturbation of the quasi‐permanent auroral oval, (2) differing projections of electron precipitation during southward and northward interplanetary magnetic field, and (3) a likely imprint of variation in Alfvénic Poynting flux deposition. Together, these modes account for >50% of the total conductivity variability throughout the E region ionosphere. Our results show that height‐integrated conductance and height‐dependent conductivities are distinctly different, underscoring the importance of studying the ionosphere in three dimensions. We provide the framework for future three‐dimensional global analysis of ionosphere‐magnetosphere coupling.

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“…Zhang et al () have recently studied the influence of IMF clock angle

ϕ_{smallIMF} = \tan^{- 1} (B_{y} / B_{z})

on nightside and dayside generation of Alfvénic power using the Lyon‐Fedder‐Mobarry (LFM) global MHD model coupled with the MIX Magnetosphere‐Ionosphere Solver (Merkin & Lyon, ). In their study, Alfvénic Poynting flux is primarily defined on the basis of Polar spacecraft observations at 4–6 R E of large‐amplitude Alfvén waves within a frequency band between approximately 2 and 20 mHz, which overlaps with Pc4–Pc5 bands.…”

Section: Introductionmentioning

confidence: 99%

“…This predicted dependence of the “Alfvénic cusp” is opposite the observed dependence of direct‐entry precipitation, which moves prenoon under dawnward IMF and postnoon under duskward IMF (e.g., Zhou et al, ). Furthermore, Zhang et al () report that the linear relationship between southward IMF magnitude and hemispheric integrated Alfvénic power becomes nonlinear when IMF B y is large, which could suggest that Alfvénic power driven by IMF B z may be produced by a different mechanism than the Alfvénic power driven by IMF B y .…”

Section: Introductionmentioning

confidence: 99%

IMF Control of Alfvénic Energy Transport and Deposition at High Latitudes

et al. 2017

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We investigate the influence of the interplanetary magnetic field (IMF) clock angle ϕIMF on high‐latitude inertial Alfvén wave (IAW) activity in the magnetosphere‐ionosphere transition region using Fast Auroral SnapshoT (FAST) satellite observations. We find evidence that negative IMF Bz coincides with nightside IAW power generation and enhanced rates of IAW‐associated electron energy deposition, while positive IMF Bz coincides with enhanced dayside wave and electron energy deposition. Large ( ≳0.3em0.3em0.3em5 nT) negative IMF By coincides with enhanced postnoon IAW power, while large positive IMF By coincides with enhanced but relatively weaker prenoon IAW power. For each ϕIMF orientation we compare IAW Poynting flux and IAW‐associated electron energy flux distributions with previously published distributions of Alfvénic Poynting flux over ∼2–22 mHz, as well as corresponding wave‐driven electron energy deposition derived from Lyon‐Fedder‐Mobarry global MHD simulations. We also compare IAW Poynting flux distributions with distributions of broad and diffuse electron number flux, categorized using an adaptation of the Newell et al. (2009) precipitation scheme for FAST. Under negative IMF Bz in the vicinity of the cusp (9.5–14.5 magnetic local time), regions of intense dayside IAW power correspond to enhanced diffuse electron number flux but relatively weaker broadband electron precipitation. Differences between cusp region IAW activity and broadband precipitation illustrate the need for additional information, such as fields or pitch angle measurements, to identify the physical mechanisms associated with electron precipitation in the vicinity of the cusp.

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Solar wind control of auroral Alfvénic power generated in the magnetotail

Cited by 20 publications

References 53 publications

Electron precipitation models in global magnetosphere simulations

Electron precipitation models in global magnetosphere simulations

High‐latitude ionospheric conductivity variability in three dimensions

IMF Control of Alfvénic Energy Transport and Deposition at High Latitudes

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