We consider the weak turbulence of whistler waves in the in low-β inner magnetosphere of the earth. Whistler waves, originating in the ionosphere, propagate radially outward and can trigger nonlinear induced scattering by thermal electrons provided the wave energy density is large enough. Nonlinear scattering can substantially change the direction of the wave vector of whistler waves and hence the direction of energy flux with only a small change in the frequency. A portion of whistler waves return to the ionosphere with a smaller perpendicular wave vector resulting in diminished linear damping and enhanced ability to pitch-angle scatter trapped electrons. In addition, a portion of the scattered wave packets can be reflected near the ionosphere back into the magnetosphere. Through multiple nonlinear scatterings and ionospheric reflections a long-lived wave cavity containing turbulent whistler waves can be formed with the appropriate properties to efficiently pitch-angle scatter trapped electrons. The primary consequence on the earth’s radiation belts is to reduce the lifetime of the trapped electron population.

Summary form only given. Recent observations of the VLF waves with frequencies close to so-called lower hybrid resonance frequency have shown that amplitudes of the observed waves are 20–30 dB smaller than those obtained in VLF propagation models. Nonlinear interactions have been suggested1 to account for the missing mechanism of energy losses in the current propagation models. Our study2 of nonlinear induced scattering in electrostatic limit based on a novel 3D code which includes so-called vector nonlinearity pinned the above nonlinear mechanism as a very likely source of this discrepancy. The results virtually reproduce the Demeter satellite observations of intense broadband lower hybrid (LH) electrostatic waves generated by whistler-mode waves from the VLF transmitter NWC. Here we present the results of the extension of the numerical model to electromagnetic (whistler) limit and discuss possible ways of doing the modeling in realistic geometry, essential for obtaining the correct spatial distribution of attenuation of the pump wave emitted from spacecraft through various latitude/longitude as well as altitude regions of the ionosphere.

Submitted for the DPP10 Meeting of The American Physical Society The strahl as a source of electrostatic whistler waves in the solar wind turbulence VALENTIN SHEVCHENKO, VITALY GALINSKY, ECE UCSD — According to observations, the solar wind electron distribution consists of a dense core component (95% of the total electron density) and the suprathermal population (5%) that consists of halo with Maxwellian distribution with hotter temperature and of so-called strahl with a narrow pitch angle distribution directed along the magnetic field. This distribution can be unstable with regards to excitation of lower hybrid waves at anomalous Doppler resonance when the energy source of instability is parallel motion of electrons.1 We investigated the nonlinear dynamics of instability in local approximation by using a hybrid method on resonant numeric simulations. The dynamics of wave power spectrum as well as the strahl distribution function were studied for different distribution function over parallel velocities of strahl electrons. The halo formation is discussed. 1Shevchenko V., and V. Galinsky, Nonlinear Processes in Geophysics (submitted) (2010). Valentin Shevchenko ECE UCSD Date submitted: 21 Jul 2010 Electronic form version 1.4

Sweeping mechanism of absorption of Alfven wave energy in the divergent solar wind is modeled using a scale-separation approach1. MHD waves are excited through reconnection at the sun with frequencies below the local ion cyclotron frequency. The fluctuations with highest frequencies will be absorbed by heavy ions as the wave packet propagates within the lower corona in the outward direction in decreasing magnetic field. At larger distances smaller frequencies will fall in cyclotron resonance with heavy ions but the wave absorption can eventually stop as the heavy ions form the shell-like distribution. Amplitude at these frequencies can even grow due to secondary cyclotron instability2. Part of the wave spectrum can reach at some distance the cyclotron frequency of ?-particles where the same picture will take place. The remaining low frequency part of the spectrum that falls in cyclotron resonance with protons at larger distances from the sun will be responsible for the solar wind heating and acceleration. We answer the questions: “Will the wave spectrum be completely absorbed by minor heavy ions and α-particles?” and “Do we need some additional mechanism of generation of the MHD waves interacting with protons?”

We study the heavy ion acceleration due to cyclotron interaction with both right‐ and left‐hand polarized MHD waves propagating along the magnetic field in the outward direction in the divergent solar wind. It is shown in test‐particle approximation that heavy ions can overcome the gap between the maximum resonant velocity for left‐handed waves and minimum resonant velocity for right‐handed waves and acquire the average parallel velocity on the order of local Alfven speed relative to the protons.

As a result of cyclotron interaction with Alfvén waves propagating from the sun, pitch angle diffusion of resonant particles takes place and a shell-like distribution function of resonant ions is formed at each distance from the sun. Stability of the solar wind ion shell-like distribution function with respect to excitation of waves at larger distances is addressed. It is shown in linear approximation, that in the case when the phase velocity of Alfvén waves decreases with distance, ions with shell distribution excite outward propagating Alfvén waves with smaller phase velocities when they advance to larger distances. The nonlinear dynamics of the wave spectrum as well as the evolution of the ion distribution function are studied. The characteristic spectrum at the high-frequency edge of the magnetohydrodynamic fluctuations is explained.

The theoretical study of alpha particle acceleration at a quasi-parallel shock due to interaction with Alfven waves self-consistently excited in both upstream and downstream regions was conducted using a scale- separation model. The model uses conservation laws and resonance conditions to find where waves will be generated or dumped and hence particles will be pitch--angle scattered as well as the change of the wave energy due to instability or damping. It includes in consideration the total distribution function (the bulk plasma and high energy tail), so no any assumptions (e.g. seed populations, or some ad-hoc escape rate of accelerated particles) are required. In previous studies heavy ions were treated as perfect test particles, they only experienced the Alfven turbulence excited by protons and didn't contribute to turbulence generation. In contrast to this approach, we consider the ion scattering on hydromagnetic turbulence generated by both protons and ions themselves. It is important for alpha particles with their relatively large mass-loading parameter p p m n m n P α α = that defines efficiency of the wave excitation by alpha particles. The energy spectra of alpha particles are found and compared with those obtained in test particle approximation.