Reconstructing the magnetosphere from data using radial basis functions

Andreeva, V. A.; Tsyganenko, N. A.

doi:10.1002/2015ja022242

Cited by 30 publications

(28 citation statements)

References 32 publications

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“…We are now in the process of testing the Weimer () electric field model incorporated into IMPTAM which depends on the IMF clock angle, IMF total field and components, V SW , P SW , and AL index. For magnetic field, several of the latest models, such as the TA15 Tsyganenko and Andreeva () model and the RBF (Radial Basis Function) model (Andreeva & Tsyganenko, ; Tsyganenko & Andreeva, ) are now being considered.…”

Section: Discussionmentioning

confidence: 99%

Validation of Inner Magnetosphere Particle Transport and Acceleration Model (IMPTAM) With Long‐Term GOES MAGED Measurements of keV Electron Fluxes at Geostationary Orbit

et al. 2019

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Surface charging by keV (kiloelectron Volt) electrons can pose a serious risk for satellites. There is a need for physical models with the correct and validated dynamical behavior. The 18.5‐month (2013–2015) output from the continuous operation online in real time as a nowcast of the Inner Magnetosphere Particle Transport and Acceleration Model (IMPTAM) is compared to the GOES 13 MAGnetospheric Electron Detector (MAGED) data for 40, 75, and 150 keV energies. The observed and modeled electron fluxes were organized by Magnetic Local Time (MLT) and IMPTAM driving parameters; the observed Interplanetary Magnetic Field (IMF) BZ, BY, and |B|; the solar wind speed VSW; the dynamic pressure PSW; and Kp and SYM‐H indices. The peaks for modeled fluxes are shifted toward midnight, but the ratio between the observed and modeled fluxes at around 06 MLT is close to 1. All the statistical patterns exhibit very similar features with the largest differences of about 1 order of magnitude at 18–24 MLT. Based on binary event analysis, 20–78% of threshold crossings are reproduced, but Heidke skill scores are low. The modeled fluxes are off by a factor of 2 in terms of the median symmetric accuracy. The direction of the error varies with energy: overprediction by 50% for 40 keV, overprediction by 2 for 75 keV, and underprediction by 18% for 150 keV. The revealed discrepancies are due to the boundary conditions developed for ions but used for electrons, absence of substorm effects, representations of electric and magnetic fields which can result in not enough adiabatic acceleration, and simple models for electron lifetimes.

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Section: Discussionmentioning

confidence: 99%

Validation of Inner Magnetosphere Particle Transport and Acceleration Model (IMPTAM) With Long‐Term GOES MAGED Measurements of keV Electron Fluxes at Geostationary Orbit

et al. 2019

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“…A symmetrical RC located farther from the Earth results in a stronger effect at the subsolar magnetopause. Moreover, the shape of the ring current in the dayside magnetosphere is still not well established and may differ from a torus [Kirpichev and Antonova, 2014;Andreeva and Tsyganenko, 2016] which would also influence the magnetopause position.…”

Section: Discussionmentioning

confidence: 99%

Do we know the actual magnetopause position for typical solar wind conditions?

et al. 2016

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We compare predicted magnetopause positions at the subsolar point and four reference points in the terminator plane obtained from several empirical and numerical MHD models. Empirical models using various sets of magnetopause crossings and making different assumptions about the magnetopause shape predict significantly different magnetopause positions (with a scatter >1 RE) even at the subsolar point. Axisymmetric magnetopause models cannot reproduce the cusp indentations or the changes related to the dipole tilt effect, and most of them predict the magnetopause closer to the Earth than nonaxisymmetric models for typical solar wind conditions and zero tilt angle. Predictions of two global nonaxisymmetric models do not match each other, and the models need additional verification. MHD models often predict the magnetopause closer to the Earth than the nonaxisymmetric empirical models, but the predictions of MHD simulations may need corrections for the ring current effect and decreases of the solar wind pressure that occur in the foreshock. Comparing MHD models in which the ring current magnetic field is taken into account with the empirical Lin et al. model, we find that the differences in the reference point positions predicted by these models are relatively small for Bz=0. Therefore, we assume that these predictions indicate the actual magnetopause position, but future investigations are still needed.

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“…The next step is to decompose the toroidal and poloidal potentials ψ 1 and ψ 2 , into linear combinations of modified radial basis functions (Andreeva & Tsyganenko, ; Tsyganenko & Andreeva, )

normalψ = \sum_{i} α_{i} χ_{i}

χ_{i} ((), \overset{r}{true}; normalD, \overset{L}{true}) = \sqrt{{(\frac{normalx - R_{normali, normalx}}{{normalL}_{normalx}})}^{2} + {(\frac{normaly - R_{normali, normaly}}{{normalL}_{normaly}})}^{2} + {(\frac{normalz - R_{normali, normalz}}{{normalL}_{normalz}})}^{2} + D^{2}}

where the vectors

{\overset{true\to}{R}}_{i}

are coordinates of meshwork grid nodes and D is an adjustable regularization parameter. The advantage of this approach is the number of nodes, that is, the resolution of the reconstructed field can be adjusted in different situations.…”

Section: Methods Descriptionmentioning

confidence: 99%

Reconstruction of Local Magnetic Structures by a Modified Radial Basis Function Method

et al. 2019

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Local magnetic structures in space environments, in particular, those in the diffusion region such as magnetic nulls or separators, are very difficult to identify by satellite measurements but important for understanding of magnetic reconnection. Multi‐spacecraft missions such as Cluster or MMS, however, provide an opportunity to reconstruct the fine structures using vector data of space magnetometers. In this paper, we introduce a method for such a local reconstruction, based on the modified radial basis functions (Andreeva & Tsyganenko, 2016, https://doi.org/10.1002/2016JA023217), used previously for the global magnetic field modeling. A principal advantage of this method is its freedom from a priori assumptions on the magnetic field topology. The method has been tested on 21/2 and 3D reconnection geometries and provided a good agreement with preset models. The relative errors of null positions, γ‐line directions, and ∑‐surface normal directions are found to be below 6% even with 20% random errors added to the target magnetic field vectors in reconstruction of 3D separator model geometry. Applications of the method to the field reconstruction based on Cluster measurements are also presented and discussed.

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Reconstructing the magnetosphere from data using radial basis functions

Cited by 30 publications

References 32 publications

Validation of Inner Magnetosphere Particle Transport and Acceleration Model (IMPTAM) With Long‐Term GOES MAGED Measurements of keV Electron Fluxes at Geostationary Orbit

Validation of Inner Magnetosphere Particle Transport and Acceleration Model (IMPTAM) With Long‐Term GOES MAGED Measurements of keV Electron Fluxes at Geostationary Orbit

Do we know the actual magnetopause position for typical solar wind conditions?

Reconstruction of Local Magnetic Structures by a Modified Radial Basis Function Method

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