Ion acceleration at dipolarization fronts in the inner magnetosphere

During geomagnetic storms plasma pressure in the inner magnetosphere is controlled by energetic ions of tens to hundreds of keV. Plasma pressure is the source of global storm time currents, which control the distribution of magnetic field and couple the inner magnetosphere and the ionosphere. Recent...

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Bibliographic Details
Published in:Journal of geophysical research. Space physics 2017-03, Vol.122 (3), p.3040-3054
Main Authors: Ukhorskiy, A. Y., Sitnov, M. I., Merkin, V. G., Gkioulidou, M., Mitchell, D. G.
Format: Article
Language:English
Subjects:
Acceleration
Activation
Electric charge
Electric fields
Fronts
Geomagnetic storms
Geomagnetism
injections
Ion acceleration
Ionosphere
Ions
Magnetic fields
Magnetic properties
Magnetic storms
Magnetism
Magnetosphere
Magnetospheres
Magnetotails
Plasma pressure
ring current
Robustness
Storms
Trapping
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Summary:During geomagnetic storms plasma pressure in the inner magnetosphere is controlled by energetic ions of tens to hundreds of keV. Plasma pressure is the source of global storm time currents, which control the distribution of magnetic field and couple the inner magnetosphere and the ionosphere. Recent analysis showed that the buildup of hot ion population in the inner magnetosphere largely occurs in the form of localized discrete injections associated with sharp dipolarizations of magnetic field, similar to dipolarization fronts in the magnetotail. Because of significant differences between the ambient magnetic field and the dipolarization front properties in the magnetotail and the inner magnetosphere, the physical mechanisms of ion acceleration at dipolarization fronts in these two regions may also be different. In this paper we discuss a new acceleration mechanism enabled by stable trapping of ions at the azimuthally localized dipolarization fronts. It is shown that trapping can provide a robust mechanism of ion energization in the inner magnetosphere even in the absence of large electric fields. Key Points Localized dipolarizations are robust mechanisms of ion acceleration in the inner magnetosphere Acceleration is enabled by stable trapping at inverse magnetic field gradient at the interface between the front and the ambient plasma The acceleration process depends on ion mass and charge state
ISSN:2169-9380
2169-9402
DOI:10.1002/2016JA023304