Analysis of the Duration of Rising Tone Chorus Elements

Journal Article · Fri Dec 29 00:00:00 EST 2017 · Geophysical Research Letters

DOI:https://doi.org/10.1002/2017GL075824· OSTI ID:1415164

Teng, S.  ^[1]; Tao, X.  ^[1]; Xie, Y.  ^[1]; Zonca, F.  ^[2]; Chen, L.  ^[3]; Fang, W. B. ^[1]; Wang, S. ^[1]

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1. CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Sciences University of Science and Technology of China Hefei China, Collaborative Innovation Center of Astronautical Science and Technology China
2. ENEA C. R. Frascati Frascati Italy, Institute of Fusion Theory and Simulation and Department of Physics Zhejiang University Hangzhou China
3. Institute of Fusion Theory and Simulation and Department of Physics Zhejiang University Hangzhou China, Department of Physics and Astronomy University of California Irvine CA USA

Abstract The duration of chorus elements is an important parameter to understand chorus excitation and to quantify the effects of nonlinear wave‐particle interactions on energetic electron dynamics. In this work, we analyze the duration of rising tone chorus elements statistically using Van Allen Probes data. We present the distribution of chorus element duration ( τ ) as a function of magnetic local time (MLT) and the geomagnetic activity level characterized by auroral electrojet ( A E ) index. We show that the typical value of τ for nightside and dawnside is about 0.12 s, smaller than that for dayside and duskside by about a factor of 2 to 4. Using a previously developed hybrid code, DAWN, we suggest that the background magnetic field inhomogeneity might be an important factor in controlling the chorus element duration. We also report that τ is larger during quiet times and shorter during moderate and active periods; this result is consistent with the MLT dependence of τ and the occurrence pattern of chorus waves at different levels of geomagnetic activity. We then investigate the correlation between τ and the frequency chirping rate (Γ). We show that, from observation, τ scales with Γ as , suggesting that statistically the frequency range of chorus elements ( τ Γ) should be roughly the same for different elements. These findings should be useful to the further development of a theoretical model of chorus excitation and to the quantification of nonlinear wave‐particle interactions on energetic electron dynamics.

• Sponsoring Organization: USDOE
• OSTI ID: 1415164
• Journal Information: Geophysical Research Letters, Journal Name: Geophysical Research Letters Vol. 44 Journal Issue: 24; ISSN 0094-8276
• Publisher: American Geophysical Union (AGU)
• Country of Publication: United States
• Language: English