Waveforms of Langmuir turbulence in inhomogeneous solar wind plasmas

International audienceModulated Langmuir waveforms have been observed by several spacecraft in various regions of the heliosphere, such as the solar wind, the electron foreshock, the magnetotail, or the auroral ionosphere. Many observations revealed the bursty nature of these waves, which appear to be highly modulated, localized, and clumped into spikes with peak amplitudes typically 3 orders of magnitude above the mean. The paper presents Langmuir waveforms calculated using a Hamiltonian model describing self-consistently the resonant interaction of an electron beam with Langmuir wave packets in a plasma with random density fluctuations. These waveforms, obtained for different profiles of density fluctuations and ranges of parameters relevant to solar type III electron beams and plasmas measured at 1 AU, are presented in the form they would appear if recorded by a satellite moving in the solar wind. Comparison with recent measurements by the STEREO and WIND satellites shows that their characteristic features are very similar to the observations

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

International audienceIn this paper we investigate the electron pitchanglediffusion coefficients in the night-side inner magnetospherearound the geostationary orbit (L 7) due to magneticfield deformation. We compare the effects of resonantwave–particle scattering by lower band chorus waves and theadiabaticity violation of electron motion due to the strongcurvature of field lines in the vicinity of the equator. Fora realistic magnetic field configuration, the nonadiabatic effectsare more important than the wave–particle interactionsfor high energy (> 1 MeV) electrons. For smaller energy,the scattering by waves is more effective than nonadiabaticone. Moreover, the role of nonadiabatic effects increases withparticle energy. Therefore, to model electron scattering andtransport in the night-side inner magnetosphere, it is importantto take into account the peculiarities of high-energy electrondynamics

Wave energy budget analysis in the Earth's radiation belts uncovers a missing energy

International audienceWhistler-mode emissions are important electromagnetic waves pervasive in the Earth's magnetosphere, where they continuously remove or energize electrons trapped by the geomagnetic field, controlling radiation hazards to satellites and astronauts and the upper-atmosphere ionization or chemical composition. Here, we report an analysis of 10-year Cluster data, statistically evaluating the full wave energy budget in the Earth's magneto-sphere, revealing that a significant fraction of the energy corresponds to hitherto generally neglected very oblique waves. Such waves, with 10 times smaller magnetic power than parallel waves, typically have similar total energy. Moreover, they carry up to 80% of the wave energy involved in wave–particle resonant interactions. It implies that electron heating and precipitation into the atmosphere may have been significantly under/over-valued in past studies considering only conventional quasi-parallel waves. Very oblique waves may turn out to be a crucial agent of energy redistribution in the Earth's radiation belts, controlled by solar activity

Timescales for electron quasi-linear diffusion by parallel and oblique lower-band chorus waves

International audience[1] The loss of relativistic electrons from the Earth's radiation belts can be described in terms of the quasi-linear pitch angle diffusion by cyclotron-resonant waves, provided that their frequency spectrum is broad enough. Chorus waves at large wave-normal angles with respect to the magnetic field are often present in CLUSTER and THEMIS measurements in the outer belt at moderate to high latitudes. An approximate analytical formulation of diffusion coefficients has been derived in the low-frequency limit, leading to a simplified analytical expression of diffusion coefficients and lifetimes for energetic trapped electrons. Large values of the wave-normal angles between the Gendrin and resonance angles are shown to induce important increases in diffusion, thereby strongly reducing the particle lifetimes (by almost two orders of magnitude). The analytical diffusion coefficients and lifetimes obtained here are found to be in a good agreement with full numerical calculations based on CLUSTER chorus waves measurements in the outer belt for electron energies ranging from 100 keV to 2 MeV. Such very oblique chorus waves could contribute to a predominantly perpendicular anisotropy of the global equatorial electron population on the dayside and to a relative isotropization at low energy under disturbed conditions. It is also suggested that they might play a significant role in pulsating auroras

Редкая форма поражения ладоней и подошв при красном плоском лишае

Lichen planus is a disease characterized by a large variety of clinical forms and morphological patterns. Localized rash on the palms and soles is considered rare and may create certain problems in diagnosis if it is present as an isolated finding in the absence of typical papular rash on the skin and mucous membranes, and such problems may be solved by histological examination. We report a case of a 41-year-old male with palmoplantar lichen planus. The disease was characterized by pruritic erythematous well-defined plaques dotted wit h multiple, punctate brown keratotic plugs on the palms and soles, which were difficult to separate when scraping. Histological examination revealed changes in the excretory ducts of eccrine sweat glands. We suggest that the presented case is a unique clinicopathologic variant of palmoplantar lichen planus that may be designated by the term “lichen planoporitis.”Красный плоский лишай - заболевание, отличающееся большим разнообразием клинических форм и проявлений. Локализация высыпаний на ладонях и подошвах считается редкой и в случае изолированного поражения, при отсутствии типичных папулезных высыпаний на коже и слизистых оболочках, создает определенные диагностические затруднения, разрешить которые позволяет гистологическое исследование. Приведено описание случая ладонно-подошвенного красного плоского лишая у 41-летнего мужчины. Заболевание проявлялось зудящими кератотическими бляшками с множественными точечными плотными роговыми пробками коричневого цвета, с трудом отделявшимися при поскабливании. При гистологическом исследовании были выявлены изменения выводных протоков эккринных потовых желез. Представленный крайне редкий клинико-морфологический вариант ладонно-подошвенного красного плоского лишая может быть обозначен термином «lichen planoporitis»

Wave-particle interactions in the outer radiation belts

Data from the Van Allen Probes have provided the first extensive evidence of non-linear (as opposed to quasilinear) wave-particle interactions in space, with the associated rapid (fraction of a bounce period) electron acceleration, to hundreds of keV by Landau resonance, in the parallel electric fields of time domain structures (TDS) and very oblique chorus waves. The experimental evidence, simulations, and theories of these processes are discussed

Electron beam relaxation in inhomogeneous plasmas

International audienceIn this work, we studied the effects of backgroundplasma density fluctuations on the relaxation of electronbeams. For the study, we assumed that the level of fluctuationswas so high that the majority of Langmuir waves generatedas a result of beam-plasma instability were trappedinside density depletions. The system can be considered as agood model for describing beam-plasma interactions in thesolar wind. Here we show that due to the effect of wave trapping,beam relaxation slows significantly. As a result, thelength of relaxation for the electron beam in such an inhomogeneousplasma is much longer than in a homogeneousplasma. Additionally, for sufficiently narrow beams, processof relaxation is accompanied by transformation of significantpart of the beam kinetic energy to energy of acceleratedparticles. They form the tail of the distribution and cancarry up to 50% of the initial beam energy flux

Determining the wavelength of Langmuir wave packets at the Earth's bow shock

International audienceThe propagation of Langmuir waves in plasmas is known to be sensitive to density fluctuations. Such fluctuations may lead to the coexistence of wave pairs that have almost opposite wave-numbers in the vicinity of their reflection points. Using high frequency electric field measurements from the WIND satellite, we determine for the first time the wavelength of intense Langmuir wave packets that are generated upstream of the Earth's electron foreshock by energetic electron beams. Surprisingly, the wavelength is found to be 2 to 3 times larger than the value expected from standard theory. These values are consistent with the presence of strong inhomogeneities in the solar wind plasma rather than with the effect of weak beam instabilities

A statistical study of the cross-shock electric potential at low Mach number, quasi-perpendicular bow shock crossings using Cluster data

International audience[1] The cross-shock electrostatic potential at the front of collision-less shocks plays a key role in the distribution of energy at the shock front. Multipoint measurements such as those provided by the Cluster II mission provide an ideal framework for the study of the cross-shock potential because of their ability to distinguish between temporal and spacial variations at the shock front. We present a statistical study of the cross-shock potential calculated for around 50 crossings of the terrestrial bow shock. The statistical dependency of the normalized (with resect to upstream ion kinetic energy) cross-shock potential (F K) on the upstream Alfvén Mach number is in good agreement with analytical results that predict decrease of F k with increasing Mach number