Cross‐tail expansion of dipolarizing flux bundles

Liu, Jiang; Angelopoulos, V.; Zhou, X.‐Z.; Yao, Zhonghua

doi:10.1002/2015ja020997

Cited by 35 publications

(40 citation statements)

References 60 publications

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“…Maximum V x is achieved d t ≈40 s at R > 15 R E (green curve) and at d t ∼ 0 at R < 15 R E . The y component of the velocity does not depend on R , however, which is consistent with cross‐tail expansion of DFBs [ Liu et al , ]. An increase in [ V × B ] y is similar at all distances and lasts ≈40 to 50 s, regardless of distance.…”

Section: Discussionsupporting

confidence: 82%

Average thermodynamic and spectral properties of plasma in and around dipolarizing flux bundles

et al. 2015

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Recent observations have suggested that spatially localized flows of high‐temperature, low‐density plasma carrying a dipolarized magnetic field (dipolarizing flux bundles, DFBs) play a key role in hot plasma transport toward the inner magnetosphere. What controls plasma heating in DFBs and how do thermodynamic parameters (such as density, temperature, pressure, and specific entropy) and spectral properties of the DFB population depend on ambient plasma sheet properties and geocentric distance R remains unknown. By statistical analysis of 271 DFB events detected by the Time History of Events and Macroscale Interactions during Substorms mission during the 2008–2009 tail seasons, we find that on average, plasma inside DFBs is a factor of 0.6 less dense and a factor of 1.5 to 2 hotter than ambient tail plasma. The radial profiles of average thermodynamic parameters inside and outside DFBs are similar; when fitted by the κ‐function, their energy spectra have similar κ‐exponents, but a factor of 2 larger peak energies inside DFBs. Our analysis suggests that average DFB plasma properties are closely linked to those of the ambient plasma sheet population. Estimations show that on average, adiabatic heating of the ambient plasma in the increased magnetic field is the major factor in DFB plasma heating.

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Section: Discussionsupporting

confidence: 82%

Average thermodynamic and spectral properties of plasma in and around dipolarizing flux bundles

et al. 2015

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“…Assuming that P3 and P4 encountered the same DFB, we can estimate the size of the DFB's XY cross section using equation (3) of Liu, Angelopoulos, Zhou, et al (), which gives a DFB width of ~3 R E (dotted semicircles in Figure ). This width is typical for a DFB in the 6–10 R E downtail region, where it has significantly expanded in Y compared to its earlier stages (Liu et al, ). Such a typical DFB, along with its trailing DFBs (probably also with other DFBs in other local times), can excite Pi2 waves that occupy a large volume of space extending from the plasma sheet to the plasmasphere, transporting energy to both lower (Figures d and k) and higher (Figure d) L shells.…”

Section: Discussionmentioning

confidence: 89%

Ultralow Frequency Waves Deep Inside the Inner Magnetosphere Driven by Dipolarizing Flux Bundles

et al. 2017

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Dipolarizing flux bundles (DFBs) are small flux tubes (typical cross‐tail scale of 1–3 RE) in the nightside magnetosphere that have magnetic field more dipolar than the background. They are generated at or beyond 20 RE downtail and then travel earthward. Although DFBs usually stop before reaching the geosynchronous orbit (GEO), they may still transfer some portion of their energy into the inner magnetosphere by radiating ULF waves. We show the clearest evidence of this process, to date, using in situ data from a fleet of spacecraft and ground stations. We illustrate that a typical DFB stopped before reaching GEO but excited Pi2 waves that filled a volume of space extending from the plasma sheet to deep inside the plasmasphere. This event provides the first in situ, direct link between stopped DFBs and ULF waves deep inside the inner magnetosphere (as deep as L = 3). The waves were attenuated when traveling away from the DFB, but even at L = 3 (XGSM = −2.2), they were still traveling with a significant earthward Poynting flux. In addition, we observed evidence of interaction between these waves and electrons at GEO.

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“…On the other hand, Zhou M et al () found that some DFs originating from reconnection were quite narrow in the out‐of‐plane direction (in the tail, the out‐of‐plane direction is close to the dawn‐dusk direction). These small‐scale DFs may either expand or merge to form larger DFs during their propagation towards Earth (Liu J et al, ). We should note that these small‐scale structures may be the ripples on DFs, as reported recently in 3‐D PIC simulation and magnetospheric multiscale (MMS) observations (Vapirev et al, ; Pan DX et al, ).…”

Section: Discussion and Summarymentioning

confidence: 99%

Small-scale dipolarization fronts in the Earth′s magnetotail

Huang¹,

Zhou²,

et al. 2019

Earth and Planetary Physics

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Previous studies suggest that dipolarization fronts (DFs) are 1 to 3R E (R E is the earth radius) wide in the dawn‐dusk direction. Recent kinetic simulations have found that DFs may break up into small‐scale structures after they are produced by reconnection. Motivated by this simulation, we revisited the scale size of DFs in the dawn‐dusk direction by using Cluster observations during the years when the inter‐distance among Cluster spacecraft was between 1000 and 2000 km. We selected the DFs that were detected by more than one spacecraft and estimated the radii of these DFs by a simple geometrical analysis, which is based on comparison of DF normals observed by different spacecraft. We found a few DFs that were only a few ion inertial lengths in the dawn‐dusk direction. These results point out the importance of multi‐scale coupling during the evolution of DFs.

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Cross‐tail expansion of dipolarizing flux bundles

Cited by 35 publications

References 60 publications

Average thermodynamic and spectral properties of plasma in and around dipolarizing flux bundles

Average thermodynamic and spectral properties of plasma in and around dipolarizing flux bundles

Ultralow Frequency Waves Deep Inside the Inner Magnetosphere Driven by Dipolarizing Flux Bundles

Small-scale dipolarization fronts in the Earth′s magnetotail

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