Global distribution of whistler‐mode chorus waves observed on the THEMIS spacecraft

Li, W.; Thorne, R. M.; Angelopoulos, V.; Bortnik, J.; Cully, C. M.; Ni, Binbin; Contel, O. Le; Roux, A.; Auster, U.; Magnes, W.

doi:10.1029/2009gl037595

Cited by 306 publications

(536 citation statements)

References 46 publications

(57 reference statements)

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“…We also assume a dipole field configuration and constant plasma density n = 0.5 cm −3 for all runs. We find that, in order to cause precipitation loss of 5 keV CPS electrons in a strong diffusion limit, a chorus intensity of ∼30 pT (L = 8) to 10 pT (L = 10) is required; such amplitudes are rarely detected by THEMIS at these distances in postmidnight sectors [Li et al, 2009;W. Li, private communication, 2009].…”

Section: Discussionmentioning

confidence: 99%

“…Nemzek et al [1995] noted that the minimum plasma density (n > 5 cm −3 ) and the density gradient required by the FCM model were unreachable from geosynchronous data; they are more unlikely to satisfy in the outer magnetosphere; e.g., n was observed as ∼0.3 cm −3 in our event (see Figure 2). Li et al [2009Li et al [ , 2010 found that the chorus wave intensity tends to be rather weak and the plasma density is usually below 1 cm −3 at L∼8-10 in postmidnight sectors (0100-0500 MLT). To make a more quantitative evaluation of the diffusion rate led by the chorus and the ECH wave at L = 8-10, we run a few simulations based upon quasi-linear wave-diffusion theories [e.g., Summers and Thorne, 2003;Lyons, 1974] and simplified models of wave spectra: Ni et al [2008] for the chorus and Horne and Thorne [2000] for the ECH.…”

Section: Discussionmentioning

confidence: 99%

“…One of the key advantages of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission is that the probes routinely traverse the equatorial magnetosphere at L = 8-11, the heart of the CPS. By virtue of this extended radial coverage, Li et al [2009] investigated new features of chorus waves at L > 7. In this event study we will present the first conjunctive study of ECH emissions and PsAs occurring in the outer magnetosphere based upon THEMIS observations.…”

Section: Introductionmentioning

confidence: 99%

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THEMIS observations of electron cyclotron harmonic emissions, ULF waves, and pulsating auroras

et al. 2010

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[1] We present multiprobe, multi-instrument observations of the electron cyclotron harmonic (ECH) emissions and ultralow-frequency (ULF) waves from Time History of Events and Macroscale Interactions during Substorms (THEMIS) and explore their potential linkage to the concurrent ground-observed pulsating auroras (PsA) on 4 January 2009. The ECH emissions were observed as discrete packets modulated by the ULF flapping motion of the neutral sheet around the probes. Combining different data sets of the ECH observations, we infer that the ECH emission intensities were strongly fluctuating and contained multi-time scale fine structures. The distribution of PsA patches featured longitudinal "wavelength" in concert with the in situ ULF wave characteristics inferred from a cross-phase analysis. The overall activeness of the PsA correlated with the in situ-measured energetic electron fluxes and ECH wave intensities. We suggest that ECH waves played the key role in the pitch angle diffusion of the plasma sheet electrons that led to the PsA, while the ULF waves structured the plasma sheet and imposed a macroscopic effect over the spatial distribution of the PsA.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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THEMIS observations of electron cyclotron harmonic emissions, ULF waves, and pulsating auroras

et al. 2010

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“…The chorus waves are frequently observed from the nightside through dawn to the dayside equatorial magnetosphere [e.g., Meredith et al, 2001;Li et al, 2009]. Therefore, the chorus wave is a primary candidate that interacts with plasma sheet electrons in the morning sector and causes them to precipitate into the atmosphere.…”

Section: Evaluation Of Theoretical Loss Time Scales Based On Pitch Anmentioning

confidence: 99%

Transport and loss of the inner plasma sheet electrons: THEMIS observations

et al. 2011

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[1] Using the electron data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft measurements from 2007 to 2009, we derived global phase space density (PSD) distributions of plasma sheet electrons (2-100 eV/nT) to examine the transport process of the electrons to the inner magnetosphere and possible loss mechanisms of plasma sheet electrons during the convective transport. The inner boundaries of the electron plasma sheet were determined by the observed global distributions and compared with the Alfvén boundaries that were calculated by the sum of the simple corotation and convection electric field models. This comparison confirms the previous results that the large-scale convection electric field controls the electron transport to the inner magnetosphere. The gradual decrease in PSD is observed from the dawn to the dayside sector, indicating the existence of some loss mechanisms in the morning sector. The loss time scales estimated from the PSD distributions were compared with the theoretical ones based on the quasi-linear diffusion theory using an empirical wave model of whistler mode chorus. We also estimated the required wave amplitudes that can explain the estimated loss time scales. It is shown that whistler mode chorus has a sufficient power to scatter the plasma sheet electrons, and the required wave amplitudes are roughly consistent with the CRRES statistical survey of the chorus wave amplitude. We suggest that the loss of plasma sheet electrons in the morning sector is mainly induced by pitch angle scattering by whistler mode chorus.

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“…The spatial distribution of chorus can give clues about what parameters may affect the excitation of chorus, and has been studied extensively in previous work (e.g., Li et al, 2009;Meredith et al, 2014). Using THEMIS data, Li et al (2009) found that chorus waves have a higher occurrence rate at dayside, although no difference between rising tone and falling tone chorus was made.…”

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confidence: 99%

A statistical study of spatial distribution and source region size of chorus waves using Van Allen Probes data

Teng¹,

Tao²,

Li³

et al. 2018

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Abstract. Spatial distribution and source region size of chorus waves are important parameters in understanding their generation. In this work, we analyze over 3 years of continuous wave burst mode data from Van Allen Probes and build a data set of rising and falling tone chorus. For the L shell range covered by Van Allen Probes data (3.5 ≤ L ≤ 7), statistical results demonstrate that the sector where rising tones are most likely to be observed is the dayside during geomagnetically quiet and moderate times and the dawnside during active times. Moreover, rising tone chorus waves have a higher occurrence rate near 5 the equatorial plane, while the falling tone chorus waves have a higher possibility to be observed at lower L-shell and higher magnetic latitude. By analyzing the direction of Poynting wave vector, we statistically investigate the chorus source region size along a field line, and compare the results with previous theoretical estimates. Our analysis confirms previous conclusions that both rising tone and falling tone chorus waves are generated near the equatorial plane, and shows that previous theoretical estimates roughly agree with the observation within a factor of two. Our results provide important insights into further 10 understanding of chorus generation.

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Global distribution of whistler‐mode chorus waves observed on the THEMIS spacecraft

Cited by 306 publications

References 46 publications

THEMIS observations of electron cyclotron harmonic emissions, ULF waves, and pulsating auroras

THEMIS observations of electron cyclotron harmonic emissions, ULF waves, and pulsating auroras

Transport and loss of the inner plasma sheet electrons: THEMIS observations

A statistical study of spatial distribution and source region size of chorus waves using Van Allen Probes data

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