A Model of the Subpacket Structure of Rising Tone Chorus Emissions. Issue 8 (13th August 2020)

• Record Type: Journal Article
• Authors: Hanzelka, Miroslav; Santolík, Ondřej; Omura, Yoshiharu; Kolmašová, Ivana; Kletzing, Craig A.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-13
• Subjects: whistler -- chorus -- nonlinear -- subpacket -- model -- plasma; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2020JA028094
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: The nonlinear growth theory of chorus emissions is used to develop a simple model of the subpacket formation. The model assumes that the resonant current, which is released from the source to the upstream region, radiates a new whistler mode wave with a slightly increased frequency, which triggers a new subpacket. Saturation of the growth in amplitude is controlled by the optimum amplitude. Numerical solution of advection equations for each subpacket, with the chorus equations acting as the boundary conditions, produces a chorus element with a subpacket structure. This element features an upstream shift of the source region with time and an irregular growth of frequency, showing small decreases between adjacent subpackets. The influence of input parameters on the number of subpackets, the shift of the source, the frequency sweep rate, and the maximum amplitude is analyzed. The model well captures basic features of instantaneous frequency measurements provided by the Van Allen Probes spacecraft. The modeled wave field can be used in future particle acceleration studies. Key Points: A simple model of subpacket formation in rising tone chorus emissions is presented The model features drops in frequency between subpacketsand upstream shift of the source The model compares well with observations made by Van Allen Probes spacecraft in the outer radiation belt