Local time resolved dynamics of field‐aligned currents and their response to solar wind variability

He, Maosheng; Vogt, Joachim; Lühr, H.; Sorbalo, Eugen

doi:10.1002/2014ja019776

Cited by 12 publications

(15 citation statements)

References 30 publications

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“…When IMF turns to the west, the reconnection topology and the particle transport reverse. This IMFy‐controlling azimuthal polarity coincides with the scenario in Figures d–f which was also suggested to account for the dayside polarity of field‐aligned current azimuthal distribution at Earth [e.g., He et al , , ].…”

Section: Results and Discussion: σB Distribution Under Different Solsupporting

confidence: 83%

Solar wind controls on Mercury's magnetospheric cusp

Vogt

Heyner³

et al. 2017

JGR Space Physics

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This study assesses the response of the cusp to solar wind changes comprehensively, using 2848 orbits of MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) observation. The assessment entails four steps: (1) propose and validate an approach to estimate the solar wind magnetic field (interplanetary magnetic field (IMF)) for MESSENGER's cusp transit; (2) define an index σ measuring the intensity of the magnetic disturbance which significantly peaks within the cusp and serves as an indicator of the cusp activity level; (3) construct an empirical model of σ as a function of IMF and Mercury's heliocentric distance rsun, through linear regression; and (4) use the model to estimate and compare the polar distribution of the disturbance σ under different conditions for a systematic comparison. The comparison illustrates that the disturbance peak over the cusp is strongest and widest extending in local time for negative IMF Bx and negative IMF Bz, and when Mercury is around the perihelion. Azimuthal shifts are associated with both IMF By and rsun: the cusp moves toward dawn when IMF By or rsun decrease. These dependences are explained in terms of the IMF Bx‐controlled dayside magnetospheric topology, the component reconnection model applied to IMF By and Bz, and the variability of solar wind ram pressure associated with heliocentric distance rsun. The applicability of the component reconnection model on IMF By indicates that at Mercury reconnection occurs at lower shear angles than at Earth.

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Section: Results and Discussion: σB Distribution Under Different Solsupporting

confidence: 83%

Solar wind controls on Mercury's magnetospheric cusp

Vogt

Heyner³

et al. 2017

JGR Space Physics

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“…EOF analysis is frequently used in oceanographic and atmospheric sciences. In space physics, EOF analysis has been applied in ionospheric modeling, studies of auroral field‐aligned currents, and investigations of the high‐latitude electric field and geomagnetic variations [ He et al ., , , ; Matsuo et al ., ; Xu and Kamide , ].…”

Section: Construction Of Emvimmentioning

confidence: 99%

“…The resultant regression coefficients β s are shown in Figure and discussed in the following section 4.2. Following He et al [], ridge regression (also known as Tikhonov L2‐norm regularization ) is carried out to stabilize the regression, and to handle the potential multicollinearity in which the control variables are mutually correlated. The regression yields a determination coefficient R 2 for each of the EOF scores.…”

Section: Construction Of Emvimmentioning

confidence: 99%

“…The standardized regression coefficients β s, yielded from the regressions and shown in Figure , provide a measure of the relative importance of the control variables [ Afifi and Clark , ; He et al ., ]. Figure suggests the most important variable controlling EOF1 and EOF2 are the IMF z and IMF y component, respectively.…”

Section: Magnetic Configuration From Noon To Midnightmentioning

confidence: 99%

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EMVIM: An empirical model for the magnetic field configuration near Venus

Vogt

Zhang

et al. 2016

JGR Space Physics

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More than 2000 orbits of Venus Express magnetic field measurements are condensed into Empirical Model of Venusian Induced Magnetic fields (EMVIM), an empirical model to quantify the magnetic configuration in the Venusian magnetosphere at low altitude (<500 km) as a function of the upstream solar wind magnetic field (IMF components) and the solar activity index F10.7 as control variables. Empirical orthogonal function (EOF) analysis is used to construct a set of data‐derived basis functions that are associated with different fundamental magnetospheric processes. The most important basis function represents the magnetic draping configuration of the IMFz component while the second important one represents the draping of the IMFy component. Solar wind‐magnetosphere interactions are quantified through regression analysis of EOF amplitudes and the control variables. Combining the basis functions with regression coefficients results in a model with a determination coefficient R2 of 0.29. As an applicational example, the model is used to quantify the density of the terminator end of the tail current JE in terms of cross‐flow IMF component and F10.7 as JEnormalA⋅km−1=3.75⋅()IMF⊥+0.2640.25emnormalnnormalTnormalnnormalT−0.0190⋅()IMF⊥⋅F10.7+30.30.25emnormalnnormalT⋅solar flux unit0.25em()10.25emnormalsnormalfnormalu0.25em=0.25em10−220.25emnormalW0.25emm−20.25emHz−1normalnnormalT⋅normalsnormalfnormalu−0.00182⋅()F10.72−72370.25emnormalsnormalfnormalu2sfu2, showing that the current strength is anticorrelated with solar activity.

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“…The FAC densities, especially in the night side, promptly respond to the onset of storm-time substorms. The fact that the R1/R2 current intensity is controlled most efficiently by substorm evolution was pointed out by He et al (2014). On Ann.…”

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confidence: 98%

<i>Swarm</i> field-aligned currents during a severe magnetic storm of September 2017

Lukianova¹

2019

Preprint

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Abstract. Swarm satellites observations are used to characterize the extreme behavior of large- and small-scale field-aligned currents (FACs) during the severe magnetic storm of September 2017. Evolution of the current intensities and the equatorward displacement of FACs are analyzed while the satellites cross the pre-midnight, pre-noon, dusk and dawn sectors in both hemispheres. The equatorward boundaries of FACs mainly follow the dynamics of ring current (as monitored in terms of the SYM-H index). The minimum latitude of the FAC boundaries is limited to 50° MLat, below which saturation occurs. The FAC densities are very variable and may increase dramatically, especially in the nightside ionosphere during the storm-time substorms. At the peak of substorm, the average FAC densities reach 3 μA/m2, while the quite level is below 0.1 μA/m2. The dawn–dusk asymmetry is manifested in the enhanced dusk-side R2 FACs in both hemispheres. Filamentary high-density structures are always observed confirming that a substantial fraction of R1/R2 FACs is composed of many small-scale currents. In the pre-noon sector, the bipolar structures (7.5 km width FACs of opposite polarities adjacent to each other) dominate, while in the post-midnight sector the upward and downward FACs tend to form more latitudinally extended structures of a certain polarity. The most intense small-scale FACs (up to ~80 μA/m2) is observed just in the post-midnight sector. Simultaneous magnetic and plasma perturbations indicate that this structure is likely a current system of a mesoscale auroral arc.

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Local time resolved dynamics of field‐aligned currents and their response to solar wind variability

Cited by 12 publications

References 30 publications

Solar wind controls on Mercury's magnetospheric cusp

Solar wind controls on Mercury's magnetospheric cusp

EMVIM: An empirical model for the magnetic field configuration near Venus

<i>Swarm</i> field-aligned currents during a severe magnetic storm of September 2017

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Local time resolved dynamics of field‐aligned currents and their response to solar wind variability

Cited by 12 publications

References 30 publications

Solar wind controls on Mercury's magnetospheric cusp

Solar wind controls on Mercury's magnetospheric cusp

EMVIM: An empirical model for the magnetic field configuration near Venus

&lt;i&gt;Swarm&lt;/i&gt; field-aligned currents during a severe magnetic storm of September 2017

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<i>Swarm</i> field-aligned currents during a severe magnetic storm of September 2017