Abstract
AbstractThe 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 RJ at Jupiter and ∼1.5 for equatorial distances ∼7–11 RS at Saturn.
Highlights
The Earth's internal magnetic field is, to a good approximation, dipolar, and charged particles in the magnetosphere can remain trapped in this field, according to their kinetic energy, pitch angle, and equatorial distance
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
Various studies involving charged particle dynamics such as ring current modeling (Brandt et al, 1981a; Carbary et al, 2009), energetic neutral atom (ENA) dynamics (Carbary & Mitchell, 2014), energetic particle injection dynamics (Mauk et al, 2005; Paranicas et al, 2007; 2010), and weathering process by charged particle bombardment (Nordheim et al, 2017, 2018), rely on these kinds of calculations assuming the dipolar approximation provided by Thomsen and Van Allen (1980)
Summary
The Earth's internal magnetic field is, to a good approximation, dipolar, and charged particles in the magnetosphere can remain trapped in this field, according to their kinetic energy, pitch angle, and equatorial distance. The second invariant, J, is associated with the meridional component of motion along the magnetic field between the two mirror points in each hemisphere and implies that the particle moves so as to preserve the length of the particle trajectory between the two mirror points, even in the presence of electric fields or slow time-dependent fields compared to the bouncing period. For a particle moving in an inhomogeneous magnetic field, keeping only the first-order term ∇B in the Taylor expansion of B about the guiding center of the particle's motion, inserting in Newton's law, and averaging over a gyroperiod leads to the following expression for the magnetic gradient drift velocity (Baumjohann & Treumann, 1996). But in the general case equation (9) has to be considered to compute vc
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
