ORCID Profile
0000-0001-6089-426X
Current Organisation
Northumbria University
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Publisher: American Geophysical Union (AGU)
Date: 07-2023
DOI: 10.1029/2023SW003440
Abstract: Waves which couple to energetic electrons are particularly important in space weather, as they drive rapid changes in the topology and intensity of Earth's outer radiation belt during geomagnetic storms. This includes Ultra Low Frequency (ULF) waves that interact with electrons via radial diffusion which can lead to electron dropouts via outward transport and rapid electron acceleration via inward transport. In radiation belt simulations, the strength of this interaction is specified by ULF wave radial diffusion coefficients. In this paper we detail the development of new models of electric and magnetic radial diffusion coefficients derived from in‐situ observations of the azimuthal electric field and compressional magnetic field. The new models use as it accounts for adiabatic changes due to the dynamic magnetic field coupled with an optimized set of four components of solar wind and geomagnetic activity, , , , and , as independent variables (inputs). These independent variables are known drivers of ULF waves and offer the ability to calculate diffusion coefficients at a higher cadence then existing models based on Kp. We investigate the performance of the new models by characterizing the model residuals as a function of each independent variable and by comparing to existing radial diffusion models during a quiet geomagnetic period and through a geomagnetic storm. We find that the models developed here perform well under varying levels of activity and have a larger slope or steeper gradient as a function of as compared to existing models (higher diffusion at higher values).
Publisher: Authorea, Inc.
Date: 09-02-2023
DOI: 10.22541/ESSOAR.167591092.27672309/V1
Abstract: Waves which couple to energetic electrons are particularly important in space weather, as they drive rapid changes in the topology and intensity of Earth’s outer radiation belt during geomagnetic storms. This includes Ultra Low Frequency (ULF) waves that interact with electrons via radial diffusion which can lead to electron dropouts and rapid acceleration and inward transport of electrons during. In radiation belt simulations, the strength of this interaction is specified by ULF wave radial diffusion coefficients. In this paper we detail the development of new models of electric and magnetic radial diffusion coefficients derived from in-situ observations of the azimuthal electric field and compressional magnetic field. The new models use L* as it accounts for adiabatic changes due to the dynamic magnetic field coupled with an optimized set of four components of solar wind and geomagnetic activity, Bz, V, Pdyn and Sym-H, as independent variables (inputs). These independent variables are known drivers of ULF waves and offer the ability to calculate diffusion coefficients at a higher cadence then existing models based on Kp. We investigate the performance of the new models by characterizing the model residuals as a function of each independent variable and by comparing to existing radial diffusion models during a quiet geomagnetic period and through a geomagnetic storm. We find that the models developed here perform well under varying levels of activity and have a larger slope or steeper gradient as a function of L* as compared to existing models (higher radial diffusion at higher L* values).
Publisher: American Geophysical Union (AGU)
Date: 12-2020
DOI: 10.1029/2020JA028097
Abstract: We present observations of ~10–60 min solar wind dynamic pressure structures that drive large‐scale coherent ~20–100 keV electron loss from the outer radiation belt. A combination of simultaneous satellite and Balloon Array for Radiation‐belt Relativistic Electron Losses (BARREL) observations on 11–12 January 2014 shows a close association between the pressure structures and precipitation as inferred from BARREL X‐rays. Specifically, the structures drive radial ExB transport of electrons up to 1 Earth radii, modulating the free electron energy available for low‐frequency plasmaspheric hiss growth, and subsequent hiss‐induced loss cone scattering. The dynamic pressure structures, originating near the Sun and commonly observed advecting with the solar wind, are thus able to switch on scattering loss of electrons by hiss over a large spatial scale. Our results provide a direct link between solar wind pressure fluctuations and modulation of electron loss from the outer radiation belt and may explain long‐period modulations and large‐scale coherence of X‐rays commonly observed in the BARREL data set.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Jasmine Kaur Sandhu.