A novel weighting method for satellite magnetic data and a new global magnetic field model

Abstract. Data assimilation using Kalman filters provides an effective way of understanding both spatial and temporal variations in the outer electron radiation belt. Data assimilation is the combination of in situ observations and physical models, using appropriate error statistics to approximate the uncertainties in both the data and the model. The global magnetic field configuration is one essential element in determining the adiabatic invariants for the phase space density (PSD) data used for the radiation belt data assimilation. The lack of a suitable global magnetic field model with high accuracy is still a long-lasting problem. This paper employs a physics-based magnetic field configuration for the first time in a radiation belt data assimilation study for a moderate storm event on 19 December 2002. The magnetic field used in our study is the magnetically self-consistent inner magnetosphere model RAM-SCB, developed at Los Alamos National Laboratory (LANL). Furthermore, we apply a cubic spline interpolation method in converting the differential flux measurements within the energy spectrum, to obtain a more accurate PSD input for the data assimilation than the commonly used linear interpolation approach. Finally, the assimilation is done using an ensemble Kalman filter (EnKF), with a localized adaptive inflation (LAI) technique to appropriately account for model errors in the assimilation and improve the performance of the Kalman filter. The assimilative results are compared with results from another assimilation experiment using the Tsyganenko 2001S (T01S) magnetic field model, to examine the dependence on a magnetic field model. Results indicate that the data assimilations using different magnetic field models capture similar features in the radiation belt dynamics, including the temporal evolution of the electron PSD during a storm and the location of the PSD peak. The assimilated solution predicts the energy differential flux to a relatively good degree when compared with independent LANL-GEO in situ observations. A closer examination suggests that for the chosen storm event, the assimilation using the RAM-SCB predicts a better flux at most energy levels during storm recovery phase but is slightly worse in the storm main phase than the assimilation using the T01S model.

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A case study of the plasma in the magneto-sheath using the numerical magnetosheath-magnetosphere model and THEMIS measure-ments

MATEC Web of Conferences ◽

10.1051/matecconf/201814503004 ◽

2018 ◽

Vol 145 ◽

pp. 03004

Author(s):

Polya Dobreva ◽

Olga Nitcheva ◽

Monio Kartalev

Keyword(s):

Magnetic Field ◽

Field Model ◽

Specific Aspect ◽

Plasma Parameters ◽

Ion Density ◽

Magnetic Field Model ◽

Wind Spacecraft ◽

The Mean ◽

The Magnetic Field

This paper presents a case study of the plasma parameters in the magnetosheath, based on THEMIS measurements. As a theoretical tool we apply the self-consistent magnetosheath-magnetosphere model. A specific aspect of the model is that the positions of the bow shock and the magnetopause are self-consistently determined. In the magnetosheath the distribution of the velocity, density and temperature is calculated, based on the gas-dynamic theory. The magnetosphere module allows for the calculation of the magnetopause currents, confining the magnetic field into an arbitrary non-axisymmetric magnetopause. The variant of the Tsyganenko magnetic field model is applied as an internal magnetic field model. As solar wind monitor we use measurements from the WIND spacecraft. The results show that the model quite well reproduces the values of the ion density and velocity in the magnetosheath. The simlicity of the model allows calulations to be perforemed on a personal computer, which is one of the mean advantages of our model.

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Design and Validation of a New Algorithm for the Online Computation of the Earth’s Magnetic Field Model

AIAA Modeling and Simulation Technologies Conference ◽

10.2514/6.2015-1590 ◽

2015 ◽

Cited By ~ 1

Author(s):

Farid Gulmammadov

Keyword(s):

Magnetic Field ◽

Field Model ◽

Earth’S Magnetic Field ◽

Online Computation ◽

Magnetic Field Model ◽

Earth's Magnetic Field

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CO2 — A Champ Magnetic Field Model

First CHAMP Mission Results for Gravity, Magnetic and Atmospheric Studies ◽

10.1007/978-3-540-38366-6_32 ◽

2003 ◽

pp. 220-225 ◽

Cited By ~ 16

Author(s):

Richard Holme ◽

Nils Olsen ◽

Martin Rother ◽

Hermann Lühr

Keyword(s):

Magnetic Field ◽

Field Model ◽

Magnetic Field Model

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By Cam: A Multipole Magnetic Field Model

Cataclysmic Variables - Astrophysics and Space Science Library ◽

10.1007/978-94-011-0335-0_119 ◽

1995 ◽

pp. 426-426 ◽

Cited By ~ 1

Author(s):

Paul A. Mason ◽

G. Chanmugam ◽

I. L. Andronov ◽

S. V. Koleskinov ◽

E. P. Pavlenko ◽

...

Keyword(s):

Magnetic Field ◽

Field Model ◽

Magnetic Field Model

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Retrieving lithospheric magnetisation distribution from magnetic field models

Geophysical Journal International ◽

10.1093/gji/ggz471 ◽

2019 ◽

Cited By ~ 1

Author(s):

V Lesur ◽

F Vervelidou

Keyword(s):

Magnetic Field ◽

Cost Function ◽

Spherical Harmonic ◽

Field Model ◽

Harmonic Model ◽

Whole Process ◽

Magnetic Field Model ◽

The Cost ◽

Spherical Harmonic Model ◽

The Magnetic Field

Summary We investigate to which extent the radially averaged magnetisation of the lithosphere can be recovered from the information content of a spherical harmonic model of the generated magnetic field when combined with few simple hypotheses. The results obtained show firstly that a hypothesis of magnetisation induced by a field of internal origin, even over a localised area, is not sufficient to recover uniquely the radially averaged magnetisation and, secondly, that this magnetisation can be recovered when a constant magnetisation direction is assumed. An algorithm to recover the magnetisation direction and distribution is then described and tested over a synthetic example. It requires to introduce a cost function that vanishes when estimated in a system of coordinates with its Z axis aligned with the magnetisation direction. Failing to find a vanishingly small value for the cost function is an indication that a constant magnetisation direction is not a valid hypothesis for the studied magnetic field model. The range of magnetisation directions that are compatible with the magnetic field model and a given noise level, can also be estimated. The whole process is illustrated by analysing a local, isolated maximum of the Martian magnetic field.

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Velocity-Magnetic Field Correlation of Pulsars

International Astronomical Union Colloquium ◽

10.1017/s0252921100040999 ◽

1996 ◽

Vol 160 ◽

pp. 49-50

Author(s):

Naoki Itoh ◽

Takemi Kotouda

Keyword(s):

Magnetic Field ◽

Constant Magnetic Field ◽

Field Model ◽

Transverse Velocity ◽

Distribution Model ◽

Recent Measurement ◽

Apparent Correlation ◽

Magnetic Field Model ◽

Field Correlation ◽

The Magnetic Field

Monte Carlo simulations of the evolution of pulsars are carried out in order to compare with the recent measurement of the pulsar transverse velocity by Lyne & Lorimer (1994). The new electron density distribution model of Taylor & Cordes (1993) is adopted in the simulation. Accurate pulsar orbits in the Galactic gravitational field are calculated. It is found that the constant magnetic field model of pulsars can account for the new measurement of the pulsar transverse velocity and the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars. The present finding confirms the validity of the constant magnetic field model of pulsars and consolidates the idea that the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars is caused by observational selection effects.

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A high resolution lithospheric magnetic field model over southern Africa based on a joint inversion of CHAMP, Swarm, WDMAM and ground magnetic field data

10.5194/se-2018-26 ◽

2018 ◽

Author(s):

Foteini Vervelidou ◽

Erwan Thébault ◽

Monika Korte

Keyword(s):

Magnetic Field ◽

Southern Africa ◽

Field Model ◽

Joint Inversion ◽

Field Measurements ◽

Magnetic Field Data ◽

Magnetic Field Model ◽

Lithospheric Magnetic Field ◽

The Mean ◽

Ground Magnetic

Abstract. We derive a lithospheric magnetic field model up to equivalent Spherical Harmonic degree 1000 over southern Africa. We rely on a joint inversion of satellite, near-surface and ground magnetic field data. The input data set consists of magnetic field vector measurements from the CHAMP satellite, across-track magnetic field differences from the Swarm mission, the World Digital Magnetic Anomaly Map and magnetic field measurements from repeat stations and three local INTERMAGNET observatories. For the inversion scheme, we use the Revised-Spherical Cap Harmonic Analysis (R-SCHA), a regional analysis technique able to deal with magnetic field measurements obtained at different altitudes. The model is carefully assessed and displayed at different altitudes and its spectral content is compared to high resolution global lithospheric field models. By comparing the shape of its spectrum to a statistical power spectrum of Earth's lithospheric magnetic field, we infer the mean magnetic thickness and the mean magnetization over southern Africa.

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