Jingtao Min


Last Name

Min

First Name

Jingtao

ORCID

0000-0001-5595-968X

Organisational unit

03734 - Jackson, Andrew / Jackson, Andrew

Filters

2023 - 20253
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Publications 1 - 3 of 3
  • Simultaneous inversion for source field and mantle electrical conductivity using the variable projection approach
    Item type: Journal Article
    Min, Jingtao; Grayver, Alexander (2023)
    Earth, Planets and Space
    Time-varying electromagnetic field observed on the ground or at a spacecraft consists of contributions from (i) electric source currents, such as those in the ionosphere and magnetosphere, and (ii) corresponding fields induced by source currents within the conductive Earth’s interior by virtue of electromagnetic induction. Knowledge about the spatio-temporal structure of inducing currents is a key component in ionospheric and magnetospheric studies, and is also needed in space weather hazard evaluation, whereas the induced currents depend on the Earth’s subsurface electrical conductivity distribution and allow us to probe this physical property. In this study, we present an approach that reconstructs the inducing source and subsurface conductivity structures simultaneously, preserving consistency between the two models by exploiting the inherent physical link. To achieve this, we formulate the underlying inverse problem as a separable nonlinear least-squares (SNLS) problem, where inducing current and subsurface conductivity parameters enter as linear and nonlinear model unknowns, respectively. We solve the SNLS problem using the variable projection method and compare it with other conventional approaches. We study the properties of the method and demonstrate its feasibility by simultaneously reconstructing the ionospheric and magnetospheric currents along with a 1-D average mantle conductivity distribution from the ground magnetic observatory data.
  • Assimilation of Ground and Satellite Magnetic Observations Unravels the Ionospheric, Magnetospheric, and Induced Fields During the May and October 2024 Geomagnetic Storms
    Item type: Journal Article
    Grayver, Alexander; Min, Jingtao; Olsen, Nils; et al. (2025)
    Geophysical Research Letters
    The geomagnetic storms of May and October 2024 were the strongest storms of solar cycle 25, with the (Formula presented.) index as low as −412 nT and auroras down to low latitudes. To investigate these extreme events, we developed a global magnetic field model of magnetospheric, ionospheric, and Earth-induced contributions obtained by assimilating magnetic observations. To leverage both ground observatory and multi-satellite magnetic data from the Swarm, CryoSat-2, GRACE-FO, and MSS-1 satellites, we used a new modeling approach to separate the magnetospheric and ionospheric sources, and to model both external and the Earth-induced fields with a 1-hr time resolution. The high spatio-temporal resolution of the model enables investigating the coupling between the mid-latitude ionospheric and magnetospheric field sources during all phases of the geomagnetic storms. The model reveals the total magnetic field disturbance at satellite and ground altitudes, providing critical input for space weather and a more accurate representation of the geomagnetic field.
  • A decade of the fast-varying ionospheric and magnetospheric magnetic fields from ground and multisatellite observations
    Item type: Journal Article
    Min, Jingtao; Grayver, Alexander (2025)
    Geophysical Journal International
    The time-varying geomagnetic field is a superposition of contributions from multiple internal and external current systems. A major source of geomagnetic variations at periods less than a few years are current systems external to the solid Earth, namely the ionospheric and magnetospheric currents, as well as associated induced currents. The separation of these three sources is mathematically underdetermined using either ground or satellite measurements alone, but becomes tractable when the two data sets are combined. Based on this concept, we developed a new geomagnetic field modelling approach that allows us to simultaneously characterize the mid-latitude ionospheric, magnetospheric and the internal induced magnetic fields using ground and satellite observations for all local times and magnetic conditions, and without prescribing any harmonic behaviour on these current systems in time, as is typical in other models. By applying this new method to a 10-yr data set of ground observatory and multisatellite measurements from 2014 to 2023, we obtained the time-series of the spherical harmonic coefficients of the ionospheric, magnetospheric and induced fields. These new time-series allow the study of complex non-periodic dynamics of the external magnetic fields during global geomagnetic storms, as well as periodicities in the magnetospheric coefficients linked to solar activities and periodic ionospheric magnetic fields linked to lunar daily variations, contributing to a more complete picture of the dynamics of the external currents and magnetosphere-ionosphere interactions, and facilitating more accurate space weather nowcast and forecast. Finally, the new approach allows for a better characterization of internal induced field sources, leading to higher quality electromagnetic transfer functions.
Publications 1 - 3 of 3