Multiple‐Satellite Observation of Magnetic Dip Event During the Substorm on 10 October 2013

He, Zeming; Chen, Lunjin; Zhu, Hui; Xia, Zhiyang; Reeves, G. D.; Xiong, Ying; Xie, Luhua; Cao, Yong

doi:10.1002/2017gl074869

Cited by 29 publications

(60 citation statements)

References 27 publications

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“…He et al () recently reported a ∼40‐nT magnetic dip event during substorm. They investigated the evolution of the magnetic dip at different locations of the duskside ring current and the related signatures, including EMIC wave generation, using multisatellite observations.…”

Section: Introductionmentioning

confidence: 98%

Ion Injection Triggered EMIC Waves in the Earth's Magnetosphere

et al. 2018

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We present Van Allen Probe observations of electromagnetic ion cyclotron (EMIC) waves triggered solely due to individual substorm-injected ions in the absence of storms or compressions of the magnetosphere during 9 August 2015. The time at which the injected ions are observed directly corresponds to the onset of EMIC waves at the location of Van Allen Probe A (L = 5.5 and 18:06 magnetic local time). The injection was also seen at geosynchronous orbit by the Geostationary Operational Environmental Satellite and Los Alamos National Laboratory spacecraft, and the westward(eastward) drift of ions(electrons) was monitored by Los Alamos National Laboratory spacecraft at different local times. The azimuthal location of the injection was determined by tracing the injection signatures backward in time to their origin assuming a dipolar magnetic field of Earth. The center of this injection location was determined to be close to ∼20:00 magnetic local time. Geostationary Operational Environmental Satellite and ground magnetometer responses confirm substorm onset at approximately the same local time. The observed EMIC wave onsets at Van Allen Probe were also associated with a magnetic field decrease. The arrival of anisotropic ions along with the decrease in the magnetic field favors the growth of the EMIC wave instability based on linear theory analysis.

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Section: Introductionmentioning

confidence: 98%

Ion Injection Triggered EMIC Waves in the Earth's Magnetosphere

et al. 2018

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“…Previous studies have reported that the dramatic magnetic depression (decrease by 50% or more) caused by enhancement of low‐energy ring current ions (<200 keV) during storm main phase can lead to the development of energetic electrons' butterfly PAD (Ebihara et al, ; Lyons, ). In addition, recent studies have shown that less than 20% decrease of the Bz component near the equator (for convenience, hereinafter we call this phenomenon as magnetic dip or bz dip) during substorm can also create electron butterfly PADs (He et al, ; Xiong et al, ).…”

Section: Introductionmentioning

confidence: 99%

Statistical Study of Energetic Electron Butterfly Pitch Angle Distributions During Magnetic Dip Events

Xiong

Xie

et al. 2019

Geophysical Research Letters

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The magnetic dips can create the electron butterfly pitch angle distribution (PAD) in the inner magnetosphere. However, its universality is still unconfirmed. We statistically investigate the global distribution of the occurrence rate of the magnetic dip-related butterfly PAD for 466 keV and 2.1 MeV electrons using the measurements of the twin Van Allen Probes spanning from September 2012 to November 2018. The statistical results show that the magnetic dip-related butterfly PADs are mainly confined to duskside to midnight within 4.5 < L < 6, and the peak occurrence rate (30% for 466 KeV and 70% for 2.1 MeV) occurs at the duskside equator around L = 5. The parametric study results suggest that the butterfly PADs preferably occur for high energy electrons with a negative initial radial flux gradient and a nearly isotropic initial PAD, which is consistent with the statistic results. This work confirms the vital importance of the magnetic dips on the evolution of the electron PADs.Plain Language Summary A previous case study has shown that small localized depression of the background magnetic field can lead to the formation of butterfly pitch angle distribution (PAD) of the energetic electrons in the outer radiation belt. We present a statistical study to investigate the occurrence rate of the electron butterfly PAD with magnetic field depression at different locations in the near-Earth space. The statistical result shows that the magnetic field depression-related electron butterfly PAD preferably takes place at duskside equator with altitude~4 Earth radius at which the occurrence rate reaches 30% for low energy electrons (~400 keV) and 70% for high energy electrons (~2 MeV). We also apply a parametric study to understand in detail how the electron butterfly PAD is created by magnetic field depression and the result suggests that the butterfly PAD preferably occurs for high energy electrons with a negative initial radial flux gradient and a nearly isotropic initial PAD, which is consistent with Van Allen Probe observations. The results of this paper have confirmed the generality of the magnetic field depression-related electron butterfly PAD in the inner magnetosphere and improved the understating of the influence of magnetic field variation on electron PAD in the space environment.Key Points:• The occurrence rate of bz dip-related electron butterfly PADs peaks (30% for 466 keV and 70% for 2.1 MeV) at duskside equator around L = 5 • Bz dip events are common at night side and duskside within L = 4-6 and the depth of bz dips peaks (~10%) around L = 5 at MLT = 18 • Butterfly PADs preferably occur for electron with large negative radial flux gradient and isotropic initial PAD in large bz dip at high L Supporting Information:• Supporting Information S1

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“…As they moved closer to the plasmapause, these particles were energized enough and could depress the magnetic field according to the diamagnetic effect (Gurgiolo et al, ; He, Chen, et al, ; Xia et al, ; Xiong et al, ). The magnetic dip in the inner magnetosphere is important for both the generation of butterfly PADs of electrons (Xiong et al, ) and electromagnetic ion cyclotron wave (He, Chen, et al, ; Remya et al, ). The magnetic field dip led to the decreasing of the energetic electron flux (Figure e) due to conservation of the first adiabatic invariant of electrons, consistent with earlier observations (He, Chen, et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…The magnetic dip in the inner magnetosphere is important for both the generation of butterfly PADs of electrons (Xiong et al, ) and electromagnetic ion cyclotron wave (He, Chen, et al, ; Remya et al, ). The magnetic field dip led to the decreasing of the energetic electron flux (Figure e) due to conservation of the first adiabatic invariant of electrons, consistent with earlier observations (He, Chen, et al, ). In this case, butterfly PADs were also observed by VAP‐A at the energy of 31 keV (not shown).…”

Section: Discussionmentioning

confidence: 99%

Multi‐instrument Observations of Mesoscale Enhancement of Subauroral Polarization Stream Associated With an Injection

et al. 2019

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Subauroral polarization streams (SAPS) prefer geomagnetically disturbed conditions and strongly correlate with geomagnetic indexes. However, the temporal evolution of SAPS and its relationship with dynamic and structured ring current and particle injection are still not well understood. In this study, we performed detailed analysis of temporal evolution of SAPS during a moderate storm on 18 May 2013 using conjugate observations of SAPS from the Van Allen Probes (VAP) and the Super Dual Auroral Radar Network (SuperDARN). The large-scale SAPS (LS-SAPS) formed during the main phase of this storm and decayed due to the northward turning of the interplanetary magnetic field. A mesoscale (approximately several hundreds of kilometers zonally) enhancement of SAPS was observed by SuperDARN at 0456 UT. In the conjugate magnetosphere, a large SAPS electric field (∼8 mV/m) pointing radially outward, a local magnetic field dip, and a dispersionless ion injection were observed simultaneously by VAP-A at L shell = 3.5 and MLT = 20. The particle injection observed by VAP-A is likely associated with the particle injection observed by the Geostationary Operational Environmental Satellite 15 near 20 MLT. Magnetic perturbations observed by the ground magnetometers and flow reversals observed by SuperDARN reveal that this mesoscale enhancement of SAPS developed near the Harang reversal and before the substorm onset. The observed complex signatures in both space and ground can be explained by a two-loop current wedge generated by the perturbed plasma pressure gradient and the diamagnetic effect of the structured ring current following particle injection.

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Multiple‐Satellite Observation of Magnetic Dip Event During the Substorm on 10 October 2013

Cited by 29 publications

References 27 publications

Ion Injection Triggered EMIC Waves in the Earth's Magnetosphere

Ion Injection Triggered EMIC Waves in the Earth's Magnetosphere

Statistical Study of Energetic Electron Butterfly Pitch Angle Distributions During Magnetic Dip Events

Multi‐instrument Observations of Mesoscale Enhancement of Subauroral Polarization Stream Associated With an Injection

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