Energy Conversion and Dissipation at Dipolarization Fronts: A Statistical Overview

Zhong, Zhihong; Deng, Xiaohua; Zhou, Meng; Q., W.; Tang, Rongxin; Khotyaintsev, Yuri V.; Giles, B. L.; Russell, C. T.; Burch, J. L.

doi:10.1029/2019gl085409

Cited by 56 publications

(78 citation statements)

References 61 publications

(117 reference statements)

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“…Journal of Geophysical Research: Space Physics is comparable with ion dissipation in some events (Figure 5j), but its average effect along downtail direction is more insignificant than that of ions (Figure 5i), which is consistent with recent MMS observations (Zhong et al, 2019). Based on magnetohydrodynamic (MHD) simulation, Birn and Hesse (2005) showed that load regions expand azimuthally and dissipation becomes stronger in the near-Earth region (see Figure 7 in their paper).…”

Section: 1029/2020ja028568supporting

confidence: 85%

“…Many researches have suggested that huge amounts of energy stored in the magnetic field are converted into plasma at the DF (S. Y. Huang, Fu, et al, 2015;Khotyaintsev et al, 2017;Zhong et al, 2019). The global effect of this conversion is even comparable to the reduction of the global magnetotail flux during intervals of geomagnetic activity (Angelopoulos et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…The variation of magnetic energy in the magnetotail is determined by two factors: conversion between different forms and transport between different regions (Birn & Hesse, 2005). Many researches have suggested that huge amounts of energy stored in the magnetic field are converted into plasma at the DF (S. Y. Huang, Fu, et al, 2015; Khotyaintsev et al, 2017; Zhong et al, 2019). The global effect of this conversion is even comparable to the reduction of the global magnetotail flux during intervals of geomagnetic activity (Angelopoulos et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Magnetic Energy Conversion and Transport in the Terrestrial Magnetotail Due to Dipolarization Fronts

et al. 2020

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Dipolarization front (DF) is an important region involved with energy conversion and flux transport in the planet's magnetotail. Using observation data from the recent Magnetospheric Multiscale (MMS) mission, we have identified and analyzed 215 DF events. Significant magnetic energy conversion and transport are observed at the DFs, which show strong dawn-dusk asymmetry. We find that the transport process dominates the change of local magnetic energy. Nearly 70% of the events show net Poynting flux flowing into the DF region. Such effect is more significant than local magnetic energy dissipation, averagely. When DF approaches the near-Earth region, the net flow-in Poynting flux decreases and magnetic energy dissipation increases. Our results suggest that the downstream magnetic energies of transient magnetic reconnections in the midtail may be transported to the near-Earth region by one DF event after another. These intensive strikes to the magnetosphere in the near-planet region may drive stronger storms, compared with the previous knowledge about DF. Plain Language Summary Dipolarization front (DF), a sharp boundary with a scale of ion inertial length, is frequently observed at the nightside of the terrestrial magnetosphere. It is widely believed that DF plays a key role in magnetic flux transport and energy conversion in the magnetotail. Reliable data from Magnetospheric Multiscale (MMS) give us an opportunity to investigate the magnetic energy conversion and transport associated with DF. We have statistically studied 215 DF events and found that the magnetic dissipation increases when DF moves toward the near-Earth region. It is interesting that the change of local magnetic energy mainly results from the net inflow Poynting flux, which is much larger than the magnetic energy dissipation in the midtail. These results suggest that DF has a long lifetime during the transport in the magnetotail and might produce a more intense impact on the inner magnetosphere and ionosphere.

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Section: 1029/2020ja028568supporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetic Energy Conversion and Transport in the Terrestrial Magnetotail Due to Dipolarization Fronts

et al. 2020

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“…A large amount of magnetic energy is transferred to plasma ( J · E > 0) at DFs (Angelopoulos et al, 2013; Huang et al, 2012, 2015; Zhong et al, 2019). The released magnetic energy can heat and accelerate particles, which results in the enhancement of plasma temperature and high‐energy electron/ion flux frequently observed at/behind DFs (Deng et al, 2010; Fu et al, 2011, 2012; Ohtani et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Force and Energy Balance of the Dipolarization Front

Song

Zhou

et al. 2020

JGR Space Physics

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We have performed a particle-in-cell simulation to understand the dynamic evolution of the dipolarization front during its early stage after ejected by magnetic reconnection, focusing on the force and energy balance around the dipolarization front. We track the temporal evolution of the force and different energy channels in the Lagrangian frame of the dipolarization front. We find that the curvature force continuously accelerates the dipolarization front moving outward, while the thermal pressure gradient force hinders the movement of the DF. The DF is accelerated outward because the total force is positive. The maximum value of B z at the DF gradually increases during the outward propagation of the front. Although the dipolarization front is the site with significant energy conversion from the magnetic field to plasma, that is, J • E > 0, the compression of the magnetic field by the convergent flow at the front leads to the gradual enhancement of B z. The released magnetic energy bulk accelerates and heats the plasma. The plasma thermal energy increases at the front that is primarily due to the work of the pressure gradient (v • (∇ • P) > 0), while the enthalpy flux emitted from the front reduces the thermal energy. Both the pressure-strain interaction −(P′ • ∇) • v and the pressure dilation p∇ • v contribute to the ion and electron temperature enhancement. Our results are important for revealing the dynamic evolution of the dipolarization fronts and will aid us to understand the energy transport in the disturbed magnetotail. Plain Language Summary Dipolarization front is a common structure in Earth's magnetotail. As a derivant of magnetic reconnection, the dipolarization front is generated at the X-line and propagates earthward. Scientists believe that dipolarization fronts play important roles in the energetics of the magnetotail; however, many details of this process are missing. Using particle simulation, we are able to study the force and energy balance around the dipolarization front in detail. We find that it is the curvature force that accelerates the dipolarization front moving away from the reconnection site. At the dipolarization front, different energy channels exchange. Poynting flux feeds the magnetic energy, which is dissipated to heat plasma around the front. The energy exchange and transport at the dipolarization front will shed new light on understanding the energy cycle in our magnetosphere.

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“…Observations of a dipolarization front by MMS on 24 June 2017 (adapted from Zhong et al, 2019). Panels (a)–(d) show the variations of B z component in GSM coordinates observed by MMS1, MMS2, MMS3, and MMS4, respectively.…”

Section: Application: Determining the Geometry Of The Magnetotail Dfsmentioning

confidence: 99%

Determination of the Configurations of Boundaries in Space

Zeng

Zhang

et al. 2020

JGR Space Physics

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This research aims to determine the geometrical configurations of boundary surfaces in the space environment, based on multiple spacecraft measurements. To achieve this, the Normal Field Analysis (NFA) method is presented here. With multipoint observations, the three-dimensional gradient of the normal of boundary layers can be obtained, and the principal curvatures and principal directions of the surfaces can be deduced. The correctness of the method is then verified. Two initial applications have been carried out. The first is to determine the geometrical features of the Earth's bow shock where it is found that, with a one-dimensional approximation, the surface of the bow shock has a rotational conicoid shape with eccentricity about 0.82, consistent with previous studies. Second, the method is also used to analyze two magnetotail dipolarization fronts showing that the dipolarization fronts are hyperbolic paraboloids or saddle surfaces with negative Gaussian curvatures. The south-north scale of the dipolarization fronts is about 0.835-3.98 R E , and the dawn-dusk/azimuthal scale is about 1.58-1.92 R E , confirming previous studies. The method presented can also be applied to investigate the geometries of the magnetopause, plasmapause, and other boundaries. Plain Language Summary Boundary layers commonly exist in space plasma environments and play important roles in the dynamical evolution of physical processes in space. In this research, we have presented an efficient method for determining the geometry of boundary surfaces, based on Cluster and MMS multispacecraft measurements. From multipoint measurements of the normal to boundaries, the gradient of the normal is obtained, and the principal curvatures of the surface can be deduced. Initial applications have been made for the determination of the geometrical features of the Earth's bow shock and magnetotail dipolarization fronts, confirming the efficiency of the new method. The method presented can also be applied to investigate other boundaries such as the magnetopause and plasmapause.

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Energy Conversion and Dissipation at Dipolarization Fronts: A Statistical Overview

Cited by 56 publications

References 61 publications

Magnetic Energy Conversion and Transport in the Terrestrial Magnetotail Due to Dipolarization Fronts

Magnetic Energy Conversion and Transport in the Terrestrial Magnetotail Due to Dipolarization Fronts

Force and Energy Balance of the Dipolarization Front

Determination of the Configurations of Boundaries in Space

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