Abstract
Abstract. The strong increase in the flux of relativistic electrons during the recovery phase of magnetic storms and during other active periods is investigated with the help of Hamiltonian formalism and simulations of test electrons which interact with whistler waves. The intensity of the whistler waves is enhanced significantly due to injection of 10-100 keV electrons during the substorm. Electrons which drift in the gradient and curvature of the magnetic field generate the rising tones of VLF whistler chorus. The seed population of relativistic electrons which bounce along the inhomogeneous magnetic field, interacts resonantly with the whistler waves. Whistler wave propagating obliquely to the magnetic field can interact with energetic electrons through Landau, cyclotron, and higher harmonic resonant interactions when the Doppler-shifted wave frequency equals any (positive or negative) integer multiple of the local relativistic gyrofrequency. Because the gyroradius of a relativistic electron may be the order of or greater than the perpendicular wavelength, numerous cyclotron, harmonics can contribute to the resonant interaction which breaks down the adiabatic invariant. A similar process diffuses the pitch angle leading to electron precipitation. The irreversible changes in the adiabatic invariant depend on the relative phase between the wave and the electron, and successive resonant interactions result in electrons undergoing a random walk in energy and pitch angle. This resonant process may contribute to the 10-100 fold increase of the relativistic electron flux in the outer radiation belt, and constitute an interesting relation between substorm-generated waves and enhancements in fluxes of relativistic electrons during geomagnetic storms and other active periods.Key words. Magnetospheric physics (energetic particles · trapped; plasma waves and instabilities; storms and substorms)
Highlights
Magnetic storms cause some of the largest geomagnetic®eld deformations
The phase space of a near-integrable dynamical system with two degrees of freedom consists of regular regions and chaotic domains which surround the separatrices around resonances
With the increase in the perturbation amplitude the chaotic regions cover an increasingly larger phase space and in a presence of a large amplitude wave overlapping between resonance layers leads to a global stochasticity (e.g., Lichtenberg and Lieberman, 1992)
Summary
Conservation of the three invariants during the main phase of the storm together with Liouville's theorem requires that the enhanced ring current, which decreases the inner magnetospheric magnetic ®eld, causes a decrease in the electronux as the electrons move to higher L shells. During active times theux increase of very energetic electrons >3 MeV at lower L shells often precede the increase of electrons with the same ®rst and second adiabatic invariant at higher L and results in a peak of the distribution f L around. The HIST instrument on the POLAR satellite (Blake et al, 1996) measured numerous large enhancements in f L at low L shells during active periods, including the January CME event (Selesnick and Blake 1997, 1998). Enhancement in the high energy electronuxes at lower L-Shells (Paulikas and Blake, 1979) indicates a possible existence of additional processes which operate at this region where a local heating mechanism may be operative for relativistic electrons
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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
