Electron Pitch Angle Diffusion Research Articles

Chorus wave power at the strong diffusion limit overcomes electron losses due to strong diffusion

Earth’s radiation belts consist of high-energy charged particles trapped by Earth’s magnetic field. Strong pitch angle diffusion of electrons caused by wave-particle interaction in Earth’s radiation belts has primarily been considered as a loss process, as trapped electrons are rapidly diffused into the loss cone and lost to the atmosphere. However, the wave power necessary to produce strong diffusion should also produce rapid energy diffusion, and has not been considered in this context. Here we provide evidence of strong diffusion using satellite data. We use two-dimensional Fokker-Planck simulations of electron diffusion in pitch angle and energy to show that scaling up chorus wave power to the strong diffusion limit produces rapid acceleration of electrons, sufficient to outweigh the losses due to strong diffusion. The rate of losses saturates at the strong diffusion limit, whilst the rate of acceleration does not. This leads to the surprising result of an increase, not a decrease in the trapped electron population during strong diffusion due to chorus waves as expected when treating strong diffusion as a loss process. Our results suggest there is a tipping point in chorus wave power between net loss and net acceleration that global radiation belt models need to capture to better forecast hazardous radiation levels that damage satellites.

The VLF Transmitter, Narrowband Receiver, and Tuner Investigation on the DSX Spacecraft

AbstractArtificially enhancing the pitch angle diffusion of the relativistic electrons trapped in the radiation belts with transmission of very‐low frequency (VLF) electromagnetic waves is the primary science objective of the wave‐particle interaction experiments (WPIx) on the Demonstration Science Experiments (DSX) spacecraft. The pitch angle diffusion occurs due to the interaction of stimulated whistler‐mode waves with these extremely high energy electrons. The primary payload of the DSX spacecraft is a high‐power VLF transmitter paired with a matched tuner, a two‐channel narrowband receiver, and an 81.6 m tip‐to‐tip carbon fiber longeron dipole antenna, collectively known as Transmitter, Narrowband receiver, and Tuner (TNT) instrument. TNT can execute a wide variety of programmable WPIx experiments and provide supporting in situ and remote plasma characterizations. In its main high‐power mode, the whistler stimulation on selected frequencies between 2.5 and 34 kHz is done by applying a high‐voltage signal, up to nominally 5 kV, at each transmit antenna monopole feed. Maximum power is radiated when the antenna‐plasma circuit reactance is tuned out, leading to resonance conditions at the selected frequency. In the radiation belts, the unknown and varying contributions of the ambient plasma to the total reactance have to be determined automatically and tuned out adaptively, steering the overall VLF circuit within the resonance state as DSX orbits the Earth. Auxiliary to the main WPIx mode, the low‐power relaxation sounding, remote plasma sensing, and listen‐only VLF‐HF emission spectrographic operations are used to probe the surrounding and remote plasma density and the local magnetic field strength.

The wave-particle interactions between chorus waves and electrons in the Earth radiation belts

There exists a large number of high-energy electrons and various plasma waves in the Earth’s radiation belts. The chorus waves, as a kind of whistler-mode waves can cause electrons acceleration and loss by wave-particle interactions, thus playing a vital role in the dynamic evolution of the radiation belts. To improve our understandings of such mechanisms and facilitate people to anticipate the dramatic variation of space environment, we utilized the wave and field data from Van Allen Probes to statistically study the acceleration and loss timescale of electrons by chorus waves. The first part in this paper presents the temporal-spatial distribution of the chorus characteristics and background field parameters. The second part exhibits the loss and acceleration timescales of electrons caused by chorus waves. The main results in this paper includes: As geomagnetic activity and L shells increase, the pitch angle and momentum diffusion of electrons driven by chorus waves strengthens. The dramatic acceleration of electrons by chorus waves exists in the region with lower fpe /fce . Compared with keV electrons, MeV electrons are hard to be scattered by chorus waves, and electrons be precipitated into the atmosphere within several hours during highly disturbed times.

A Test of Energetic Particle Precipitation Models Using Simultaneous Incoherent Scatter Radar and Van Allen Probes Observations.

Quantification of energetic electron precipitation caused by wave‐particle interactions is fundamentally important to understand the cycle of particle energization and loss of the radiation belts. One important way to determine how well the wave‐particle interaction models predict losses through pitch‐angle scattering into the atmospheric loss cone is the direct comparison between the ionization altitude profiles expected in the atmosphere due to the precipitating fluxes and the ionization profiles actually measured with incoherent scatter radars. This paper reports such a comparison using a forward propagation of loss‐cone electron fluxes, calculated with the electron pitch angle diffusion model applied to Van Allen Probes measurements, coupled with the Boulder Electron Radiation to Ionization model, which propagates the fluxes into the atmosphere. The density profiles measured with the Poker Flat Incoherent Scatter Radar operating in modes especially designed to optimize measurements in the D‐region, show multiple instances of close quantitative agreement with predicted density profiles from precipitation of electrons caused by wave‐particle interactions in the inner magnetosphere, alternated with intervals with large differences between observations and predictions. Several‐minute long intervals of close prediction‐observation approximation in the 65–93 km altitude range indicate that the whistler wave‐electron interactions models are realistic and produce precipitation fluxes of electrons with energies between 10 keV and >100 keV that are consistent with observations. The alternation of close model‐data agreement and poor agreement intervals indicates that the regions causing energetic electron precipitation are highly spatially localized.

Resonance broadening effect for relativistic electron interaction with electromagnetic ion cyclotron waves

Relativistic electron scattering by electromagnetic ion cyclotron (EMIC) waves is one of the most effective mechanisms for >1 MeV electron flux depletion in the Earth's radiation belts. Resonant electron interaction with EMIC waves is traditionally described by quasi-linear diffusion equations, although spacecraft observations often report EMIC waves with intensities sufficiently large to trigger nonlinear resonant interaction with electrons. An important consequence of such nonlinear interaction is the resonance broadening effect due to high wave amplitudes. In this study, we quantify this resonance broadening effect in electron pitch-angle diffusion rates. We show that resonance broadening can significantly increase the pitch-angle range of EMIC-scattered electrons. This increase is especially important for ∼1 MeV electrons, where, without the resonance broadening, only those near the loss cone (with low fluxes) can resonate with EMIC waves.

Multi-dimensional modeling of radiation belt electron pitch-angle diffusion coefficients caused by plasmaspheric hiss

Plasmaspheric hiss is an important wave mode in the Earth’s radiation belts. Hiss waves can scatter energetic electrons into loss cones to precipitate into the atmosphere, and therefore become an important source of fluctuations, leading the radiation belt to lose electrons . As a function of electron energy and pitch angle, the diffusion coefficient of hiss waves for radiation belt electrons is significantly influenced by the solar wind and geomagnetic activity, and also strongly depends on the spatial position, the background magnetic field, and the plasma density distribution. In order to quickly obtain the diffusion coefficients of hiss waves on electrons in the radiation belt for modelling the global dynamics of the radiation belt, we systematically calculate the diffusion coefficients of hiss waves on electrons in the radiation belt by using the full diffusion code (FDC), and build a four-dimensional matrix database of diffusion coefficients for the spatial region <i>L</i> = 1.5–6, the cold plasma parameter <i>α</i><sup>*</sup> = 3–30, electron energy 1 keV–10 MeV, and electron throw angle 0°–90°. According to the database, we can quickly obtain diffusion coefficients with different <i>L</i> and <i>α</i><sup>*</sup> values through linear interpolations. By comparing the errors between diffusion coefficients calculated by the FDC code and those linearly interpolated from the diffusion coefficient database, the accuracies of interpolated coefficients are validated, showing that most of the errors lie in 10%. The four-dimensional database of hiss wave pitch angle diffusion coefficients for radiation belt electrons and the validated linear interpolation method established in this paper can significantly reduce the time required to obtain global information about hiss wave diffusion coefficients, thereby rapidly improving the computational efficiency of carrying out simulations of spatial and temporal changes in the radiation belts over long periods of time, which in turn is expected to provide favourable conditions for the development of dynamic forecasting models of the Earth's radiation belts.

Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation

In August 2015, the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) observed precipitation of energetic (<200 keV) electrons magnetically conjugate to a region of dense cold plasma as measured by the twin Van Allen Probes spacecraft. The two spacecraft passed through the high density region during multiple orbits, showing that the structure was spatial and relatively stable over many hours. The region, identified as a plasmaspheric plume, was filled with intense hiss-like plasma waves. We use a quasi-linear diffusion model to investigate plume whistler-mode hiss waves as the cause of precipitation observed by BARREL. The model input parameters are based on the observed wave, plasma and energetic particle properties obtained from Van Allen Probes. Diffusion coefficients are found to be largest in the same energy range as the precipitation observed by BARREL, indicating that the plume hiss waves were responsible for the precipitation. The event-driven pitch angle diffusion simulation is also used to investigate the evolution of the electron phase space density (PSD) for different energies and assumed initial pitch angle distributions. The results show a complex temporal evolution of the phase space density, with periods of both growth and loss. The earliest dynamics, within the ∼5 first minutes, can be controlled by a growth of the PSD near the loss cone (by a factor up to ∼2, depending on the conditions, pitch angle, and energy), favored by the absence of a gradient at the loss cone and by the gradients of the initial pitch angle distribution. Global loss by 1-3 orders of magnitude (depending on the energy) occurs within the first ∼100 min of wave-particle interaction. The prevalence of plasmaspheric plumes and detached plasma regions suggests whistler-mode hiss waves could be an important driver of electron loss even at high L-value (L ∼6), outside of the main plasmasphere.

Empirical Loss Timescales of Slot Region Electrons due to Plasmaspheric Hiss Based on Van Allen Probes Observations

AbstractBased on Van Allen Probes observations, in this study we perform a statistical analysis of the spectral intensities of plasmaspheric hiss at L‐shells of 1.8–3.0 in the slot region. Our results show that slot region hiss power intensifies with a strong day‐night asymmetry as the level of substorm activity or L‐shell increases. Using the statistical spectral profiles of plasmaspheric hiss, we calculate the drift‐ and bounce‐averaged electron pitch angle diffusion coefficients and subsequently obtain the resultant electron loss timescales through 1‐D Fokker‐Planck simulations. We find that slot region electron loss timescales vary significantly from <1 day to several years, showing a strong dependence on electron energy, L‐shell and substorm activity. We also construct an empirical model of slot region electron loss timescales due to scattering by plasmaspheric hiss, which agrees well with the 1‐D simulation results and can be readily used in modeling the dynamics of slot region electrons.

Hot Plasma Effects on the Pitch-angle Scattering Rates of Radiation Belt Electrons Due to Plasmaspheric Hiss

Abstract Plasmaspheric hiss is known to be a major contributor to the dynamic losses of Earth’s radiation belt electrons. While previous computation attempts of hiss-driven electron losses are limited to the cold plasma approximation, in this study we find that hot plasma effects will modify the hiss dispersion relation and result in changes in the electron bounce-averaged electron pitch angle diffusion coefficients. Cold plasma approximation tends to overestimate the diffusion coefficients of ≲100 keV electrons by orders of magnitude, while the scattering efficiency of higher energy electrons is not greatly affected. As the L-shell decreases or the parameter decreases (where is the electron gyrofrequency and is the plasma frequency), the decrease of diffusion coefficients of low energy electrons caused by hot plasma effects become more pronounced. It is also shown that both the increase of hot electron abundance and temperature anisotropy can weaken the scattering efficiency of ≲100 keV electrons at almost all pitch angles, while the diffusion coefficients of higher energy electrons decrease at large pitch angles. Our study confirms the importance of including hot plasma effects in evaluations of hiss-driven scattering loss of radiation belt electrons.

Quantifying the Precipitation Loss of Radiation Belt Electrons During a Rapid Dropout Event

AbstractRelativistic electron flux in the radiation belt can drop by orders of magnitude within the timespan of hours. In this study, we used the drift‐diffusion model that includes azimuthal drift and pitch angle diffusion of electrons to simulate low‐altitude electron distribution observed by POES/MetOp satellites for rapid radiation belt electron dropout event occurring on 1 May 2013. The event shows fast dropout of MeV energy electrons at L > 4 over a few hours, observed by the Van Allen Probes mission. By simulating the electron distributions observed by multiple POES satellites, we resolve the precipitation loss with both high spatial and temporal resolutions and a range of energies. We estimate the pitch angle diffusion coefficients as a function of energy, pitch angle, and L‐shell and calculate corresponding electron lifetimes during the event. The simulation results show fast electron precipitation loss at L > 4 during the electron dropout, with estimated electron lifetimes on the order of half an hour for MeV energies. The electron loss rate shows strong energy dependence with faster loss at higher energies, which suggest that this dropout event is dominated by quick and localized scattering process that prefers higher energy electrons. The improved temporal and spatial resolutions of electron precipitation rates provided by multiple low‐altitude observations can resolve fast‐varying electron loss during rapid electron dropouts (over a few hours), which occur too fast for a single low‐altitude satellite. The capability of estimating the fast‐varying electron lifetimes during rapid dropout events is an important step in improving radiation belt model accuracy.

Simple analytical expressions for electron pitch angle diffusion coefficients

In the present paper, we have calculated electron pitch angle diffusion coefficients due to resonant interactions with whistler mode lower band chorus (LBC), upper band chorus (UBC), and electrostatic electron cyclotron harmonic (ECH) waves. Calculations have been performed at two values of the ratio of electron plasma frequency to gyro-frequency and thirteen representative values of electron energies for the plasma sheet electrons. The numerical data of diffusion coefficients have been fitted to simple analytical expressions for each wave mode. These analytical expressions allow for simple evaluation of pitch angle diffusion coefficients for the arbitrary pitch angle, energy, the ambient magnetic field, the wave amplitude, and the ratio of plasma frequency to gyro-frequency. In the case of LBC waves, the analytical coefficients are generally within a factor of two to the numerical coefficients, except at higher pitch angles where the numerical coefficients drop to show negligible values. Likewise, also for UBC waves, the analytical coefficients are generally within a factor of two to the numerical coefficients. The analytical coefficients for ECH waves are generally in agreement with numerical coefficients. However, the analytical expressions developed for ECH waves do not reproduce sharp fluctuations, dips, and gaps, the so-called banded structure observed in the data of numerical coefficients [A. K. Tripathi et al., Phys. Plasmas 23, 042101 (2016)] The effect of the shape variation on the profile of the wave spectral intensity and the effect of cold temperature on the numerical coefficients are also investigated. Applications of the analytical expressions of diffusion coefficients are discussed.

EMIC waves and associated relativistic electron precipitation on 25–26 January 2013

AbstractUsing measurements from the Van Allen Probes and the Balloon Array for RBSP Relativistic Electron Losses (BARREL), we perform a case study of electromagnetic ion cyclotron (EMIC) waves and associated relativistic electron precipitation (REP) observed on 25–26 January 2013. Among all the EMIC wave and REP events from the two missions, the pair of the events is the closest both in space and time. The Van Allen Probe‐B detected significant EMIC waves at L = 2.1–3.9 and magnetic local time (MLT) = 21.0–23.4 for 53.5 min from 2353:00 UT, 25 January 2013. Meanwhile, BARREL‐1T observed clear precipitation of relativistic electrons at L = 4.2–4.3 and MLT = 20.7–20.8 for 10.0 min from 2358 UT, 25 January 2013. Local plasma and field conditions for the excitation of the EMIC waves, wave properties, electron minimum resonant energy Emin, and electron pitch angle diffusion coefficient Dαα of a sample EMIC wave packet are examined along with solar wind plasma and interplanetary magnetic field parameters, geomagnetic activity, and results from the spectral analysis of the BARREL balloon observations to investigate the two types of events. The events occurred in the early main phase of a moderate storm (min. Dst* = −51.0 nT). The EMIC wave event consists of two parts. Unlike the first part, the second part of the EMIC wave event was locally generated and still in its source region. It is found that the REP event is likely associated with the EMIC wave event.

Banded structures in electron pitch angle diffusion coefficients from resonant wave-particle interactions

Electron pitch angle (Dαα) and momentum (Dpp) diffusion coefficients have been calculated due to resonant interactions with electrostatic electron cyclotron harmonic (ECH) and whistler mode chorus waves. Calculations have been performed at two spatial locations L = 4.6 and 6.8 for electron energies ≤10 keV. Landau (n = 0) resonance and cyclotron harmonic resonances n = ±1, ±2, … ±5 have been included in the calculations. It is found that diffusion coefficient versus pitch angle (α) profiles show large dips and oscillations or banded structures. The structures are more pronounced for ECH and lower band chorus (LBC) and particularly at location 4.6. Calculations of diffusion coefficients have also been performed for individual resonances. It is noticed that the main contribution of ECH waves in pitch angle diffusion coefficient is due to resonances n = +1 and n = +2. A major contribution to momentum diffusion coefficients appears from n = +2. However, the banded structures in Dαα and Dpp coefficients appear only in the profile of diffusion coefficients for n = +2. The contribution of other resonances to diffusion coefficients is found to be, in general, quite small or even negligible. For LBC and upper band chorus waves, the banded structures appear only in Landau resonance. The Dpp diffusion coefficient for ECH waves is one to two orders smaller than Dαα coefficients. For chorus waves, Dpp coefficients are about an order of magnitude smaller than Dαα coefficients for the case n ≠ 0. In case of Landau resonance, the values of Dpp coefficient are generally larger than the values of Dαα coefficients particularly at lower energies. As an aid to the interpretation of results, we have also determined the resonant frequencies. For ECH waves, resonant frequencies have been estimated for wave normal angle 89° and harmonic resonances n = +1, +2, and +3, whereas for whistler mode waves, the frequencies have been calculated for angle 10° and Landau resonance. Further, in ECH waves, the banded structures appear for electron energies ≥1 keV, and for whistler mode chorus waves, structures appear for energies >2 keV at L = 4.6 and above 200 eV for L = 6.8. The results obtained in the present work will be helpful in the study of diffusion curves and will have important consequences for diffuse aurora and pancake distributions.

Pitch-angle diffusion of electrons through growing and propagating along a magnetic field electromagnetic wave in Earth's radiation belts

The diffusion of electrons via a linearly polarized, growing electromagnetic (EM) wave propagating along a uniform magnetic field is investigated. The diffusion of electrons that interact with the growing EM wave is investigated through the autocorrelation function of the parallel electron acceleration in several tens of electron gyration timescales, which is a relatively short time compared with the bounce time of electrons between two mirror points in Earth's radiation belts. Furthermore, the pitch-angle diffusion coefficient is derived for the resonant and non-resonant electrons, and the effect of the wave growth on the electron diffusion is discussed. The results can be applied to other problems related to local acceleration or the heating of electrons in space plasmas, such as in the radiation belts.

Bounce‐ and MLT‐averaged diffusion coefficients in a physics‐based magnetic field geometry obtained from RAM‐SCB for the 17 March 2013 storm

AbstractLocal acceleration via whistler wave and particle interaction plays a significant role in particle dynamics in the radiation belt. In this work we explore gyroresonant wave‐particle interaction and quasi‐linear diffusion in different magnetic field configurations related to the 17 March 2013 storm. We consider the Earth's magnetic dipole field as a reference and compare the results against nondipole field configurations corresponding to quiet and stormy conditions. The latter are obtained with the ring current‐atmosphere interactions model with a self‐consistent magnetic field (RAM‐SCB), a code that models the Earth's ring current and provides a realistic modeling of the Earth's magnetic field. By applying quasi‐linear theory, the bounce‐ and Magnetic Local Time (MLT)‐averaged electron pitch angle, mixed‐term, and energy diffusion coefficients are calculated for each magnetic field configuration. For radiation belt (∼1 MeV) and ring current (∼100 keV) electrons, it is shown that at some MLTs the bounce‐averaged diffusion coefficients become rather insensitive to the details of the magnetic field configuration, while at other MLTs storm conditions can expand the range of equatorial pitch angles where gyroresonant diffusion occurs and significantly enhance the diffusion rates. When MLT average is performed at drift shell L=4.25 (a good approximation to drift average), the diffusion coefficients become quite independent of the magnetic field configuration for relativistic electrons, while the opposite is true for lower energy electrons. These results suggest that, at least for the 17 March 2013 storm and for L≲4.25, the commonly adopted dipole approximation of the Earth's magnetic field can be safely used for radiation belt electrons, while a realistic modeling of the magnetic field configuration is necessary to describe adequately the diffusion rates of ring current electrons.

Investigation of EMIC wave scattering as the cause for the BARREL 17 January 2013 relativistic electron precipitation event: A quantitative comparison of simulation with observations

AbstractElectromagnetic ion cyclotron (EMIC) waves were observed at multiple observatory locations for several hours on 17 January 2013. During the wave activity period, a duskside relativistic electron precipitation (REP) event was observed by one of the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) balloons and was magnetically mapped close to Geostationary Operational Environmental Satellite (GOES) 13. We simulate the relativistic electron pitch angle diffusion caused by gyroresonant interactions with EMIC waves using wave and particle data measured by multiple instruments on board GOES 13 and the Van Allen Probes. We show that the count rate, the energy distribution, and the time variation of the simulated precipitation all agree very well with the balloon observations, suggesting that EMIC wave scattering was likely the cause for the precipitation event. The event reported here is the first balloon REP event with closely conjugate EMIC wave observations, and our study employs the most detailed quantitative analysis on the link of EMIC waves with observed REP to date.

Effect of EMIC waves on relativistic and ultrarelativistic electron populations: Ground‐based and Van Allen Probes observations

AbstractWe study the effect of electromagnetic ion cyclotron (EMIC) waves on the loss and pitch angle scattering of relativistic and ultrarelativistic electrons during the recovery phase of a moderate geomagnetic storm on 11 October 2012. The EMIC wave activity was observed in situ on the Van Allen Probes and conjugately on the ground across the Canadian Array for Real‐time Investigations of Magnetic Activity throughout an extended 18 h interval. However, neither enhanced precipitation of >0.7 MeV electrons nor reductions in Van Allen Probe 90° pitch angle ultrarelativistic electron flux were observed. Computed radiation belt electron pitch angle diffusion rates demonstrate that rapid pitch angle diffusion is confined to low pitch angles and cannot reach 90°. For the first time, from both observational and modeling perspectives, we show evidence of EMIC waves triggering ultrarelativistic (~2–8 MeV) electron loss but which is confined to pitch angles below around 45° and not affecting the core distribution.

Electron pitch-angle diffusion: resonant scattering by waves vs. nonadiabatic effects

Abstract. In this paper we investigate the electron pitch-angle diffusion coefficients in the night-side inner magnetosphere around the geostationary orbit (L ~ 7) due to magnetic field deformation. We compare the effects of resonant wave–particle scattering by lower band chorus waves and the adiabaticity violation of electron motion due to the strong curvature of field lines in the vicinity of the equator. For a realistic magnetic field configuration, the nonadiabatic effects are more important than the wave–particle interactions for high energy (> 1 MeV) electrons. For smaller energy, the scattering by waves is more effective than nonadiabatic one. Moreover, the role of nonadiabatic effects increases with particle energy. Therefore, to model electron scattering and transport in the night-side inner magnetosphere, it is important to take into account the peculiarities of high-energy electron dynamics.

Statistical model of electron pitch angle diffusion in the outer radiation belt

We calculated the bounce averaged electron pitch angle diffusion coefficients using the statistical characteristics of lower band chorus activity collected by the Cluster mission from 2001–2009. Nine years of Cluster observations provide the distributions of the θ angle between wave vectors and the background magnetic field; and the distributions of the wave total intensity Bw2 for relatively wide ranges of the magnetic latitude λ, the magnetic local times, and the Kp indices. According to Cluster observations, the probability of observing a larger Bw2 increases with λ and depends upon the magnetic local time and Kp. We compared the obtained results with the diffusion coefficients that were calculated under an assumption of parallel whistler wave propagation with a constant intensity Bw2 = 104 pT2. The last calculations substantially underestimated pitch angle diffusion for the small equatorial pitch angles, αeq, but likely overestimates for αeq > 60°. An important increase in for αeq < 30° can be explained by a large mean value for the θ distribution and by an increase of Bw2 at λ > 15°. We took the probability density distribution of the wave mean amplitude into consideration instead of the averaged value. The obtained distribution of the diffusion coefficients indicated that approximately 20% of the most intense waves can provide the main portion of pitch angle diffusion for the dawn/day sector. For the dusk/night sector, wave intensity was significantly weaker and the relative importance of intense waves was not clearly pronounced.

Evolution of the Electron Distribution Function in the Whistler Wave Turbulence of the Solar Wind

The electron distribution functions from the solar corona to the solar wind are determined in this paper by considering the effects of the external forces, of Coulomb collisions and of the wave – particle resonant interactions in the plasma wave turbulence. The electrons are assumed to be interacting with right-handed polarized waves in the whistler regime. The acceleration of electrons in the solar wind seems to be mainly due to the electrostatic potential. Wave turbulence determines the electron pitch-angle diffusion and some characteristics of the velocity distribution function (VDF) such as suprathermal tails. The role of parallel whistlers can also be extended to small altitudes in the solar wind (the acceleration region of the outer corona), where they may explain the energization and the presence of suprathermal electrons.