Trapped Particle Motion in Magnetodisk Fields. Issue 7 (10th July 2020)

• Record Type: Journal Article
• Authors: Guio, P.; Staniland, N. R.; Achilleos, N.; Arridge, C. S.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 7(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-07-10
• Subjects: magnetodisk -- trapped particle motion -- particle dynamics -- guiding center; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2020JA027827
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: The spatial and temporal characterization of trapped charged particle trajectories in magnetospheres has been extensively studied in dipole magnetic field structures. Such studies have allowed the calculation of spatial quantities, such as equatorial loss cone size as a function of radial distance, the location of the mirror points along particular field lines ( L ‐shells) as a function of the particle's equatorial pitch angle, and temporal quantities such as the bounce period and drift period as a function of the radial distance and the particle's pitch angle at the equator. In this study, we present analogous calculations for the disk‐like field structure associated with the giant rotation‐dominated magnetospheres of Jupiter and Saturn as described by the University College London/Achilleos‐Guio‐Arridge (UCL/AGA) magnetodisk model. We discuss the effect of the magnetodisk field on various particle parameters and make a comparison with the analogous motion in a dipole field. The bounce period in a magnetodisk field is in general smaller the larger the equatorial distance and pitch angle, by a factor as large as ∼8 for Jupiter and ∼2.5 for Saturn. Similarly, the drift period is generally smaller, by a factor as large as ∼2.2 for equatorial distances ∼20–24 R J at Jupiter and ∼1.5 for equatorial distances ∼7–11 R S at Saturn. Key Points: We express bounce and drift periods of particles trapped in magnetic field in terms of integrals dependent only on field geometry We present numerical calculation of these integrals for the Jovian and Kronian magnetodisks in the inner and middle magnetosphere We derive analytical approximations for the bounce and drift periods for Jupiter and Saturn, more accurate than the dipole expressions