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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Theory and simulation of electromagnetic beam modes and whistlers

Using particle-in-cell simulations and analytical methods, a study of the nonlinear evolution of electromagnetic instabilities driven by an anisotropic electron beam in an external magnetic field is performed. The unstable waves are either whistlerlike or beam-mode-like depending on the external field strength and beam velocity. The evolution of the particle distribution differs significantly in the two regimes. Even in the presence of a faster electrostatic instability, the electromagnetic waves grow to a significant amplitude. In certain cases, an energetic tail is formed, resulting in enhanced Cerenkov emission of electrostatic waves. The initial evolution of the particle distribution is explained in terms of the interaction of a given linearly unstable wave with the self-consistent perturbed distribution.

Newman, David L.↗
NASA NTRS1989

Properties of whistler mode wave packets at the leading edge of steepened magnetosonic waves - Comet Giacobini-Zinner

The physical characteristics of high-frequency wave packets detected at the steepened edge of magnetosonic waves near Comet Giacobini-Zinner are explored, based on an examination of over 45 well-defined events. The results suggest that the wave packets play an important role in the reorientation and reduction in field magnitude from the steepened magnetosonic waves to the upstream ambient field. The observed properties of the wave packets are shown to be consistent with anomalously Doppler-shifted right-hand polarized waves.

Tsurutani, Bruce T.↗
NASA NTRS1989

Comment on 'Distribution of whistler mode bursts at Venus' by F.L. Scarf, K.F. Jordan, and C.T. Russell

Consideration is given to the study of the 100-Hz electric field noise observed from the Pioneer Venus Orbiter (PVO) by Scarf et al. (1987). It is suggested that the study incorrectly interprets the results as evidence for lightning and volcanism at Venus. Statistical evidence is presented, suggesting that the distribution of the noise is essentially random, within the zone of occurrence of ion troughs, and decreases at the lowest PVO altitudes, closest to the neutral atmosphere. It is found that the topographic clustering reported by Scarf et al. is an artifact of the variable spatial distribution of troughs and associated noise.

Taylor, Harry A., Jr.↗
NASA NTRS2024

The Global Mapping of Electron Precipitation and Ionospheric Conductance From Whistler-Mode Chorus Waves

Auroral precipitation is the second major energy source after solar irradiation that ionizes the Earth’s upper atmosphere. Diffuse electron aurora caused by wave-particle interaction in the inner magnetosphere (L < 8) takes over 60% of total auroral energy flux, strongly contributing to the ionospheric conductance and thus to the ionosphere-thermosphere dynamics. This paper quantifies the impact of chorus waves on the diffuse aurora and the ionospheric conductance during quiet, medium, and strong geomagnetic activities, parameterized by AE <100, 100 < AE < 300, and AE > 300, respectively. Using chorus wave statistics and inner-magnetosphere plasma conditions from Timed History Events and Macroscale Interactions during Substorms (THEMIS) observations, we directly derive the energy spectrum of diffuse electron precipitation under quasi-linear theory. We then calculate the height-integrated conductance from the wave-driven aurora spectrum using the electron impact ionization model of Fang et al. (Geophys. Res. Lett., 2010, 37) and the MSIS atmosphere model. By utilizing Fang’s ionization model, the US Naval Research Laboratory Mass Spectrometer and Incoherent Scattar Radar (NRLMSISE-00) model from 2000s for the neutral atmosphere components, and the University of California, Los Angeles (UCLA) Full Diffusion Code, we improve upon the standard generalization of Maxwellian diffuse electron precipitation patterns and their resulting ionosphere conductance. Our study of global auroral precipitation and ionospheric conductance from chorus wave statistics is the first statistical model of its kind. We show that the total electron flux and conductance pattern from our results agree with those of Ovation Prime model over the pre-midnight to post-dawn sector as geomagnetic activity increases. Our study examines the relative contributions of upper band chorus (UBC) and lower band chorus wave (LBC) driven conductance in the ionosphere. We found LBC waves drove diffuse electron precipitation significantly more than UBC waves, however it is possible that THEMIS data may have underestimated the upper chorus band wave observations for magnetic latitudes below 65 degrees. ° .

diffuse auroral precipitation↗