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The Van Allen Probes Electric Fields and Waves (EFW) instrument provided measurements of electric fields and spacecraft floating potentials over a wide dynamic range from DC to 6.5 kHz near the equatorial plane of the inner magnetosphere between 600 km altitude and 5.8 Re geocentric distance from October 2012 to November 2019. The two identical instruments provided data to investigate the quasi-static and low frequency fields that drive large-scale convection, waves induced by interplanetary shock impacts that result in rapid relativistic particle energization, ultra-low frequency (ULF) MHD waves which can drive radial diffusion, and higher frequency wave fields and time domain structures that provide particle pitch angle scattering and energization. In addition, measurements of the spacecraft potential provided a density estimate in cold plasmas ($ < 20 eV ) from 10 to $3000~\text{cm}^{-3}$ 3000 cm − 3 . The EFW instrument provided analog electric field signals to EMFISIS for wave analysis, and it received 3d analog signals from the EMFISIS search coil sensors for inclusion in high time resolution waveform data.The electric fields and potentials were measured by current-biased spherical sensors deployed at the end of four 50 m booms in the spacecraft spin plane (spin period $\sim11~\text{sec}$ ∼ 11 sec ) and a pair of stacer booms with a total tip-tip separation of 15 m along the spin axis. Survey waveform measurements at 16 and/or 32 S/sec (with a nominal uncertainty of 0.3 mV/m over the prime mission) were available continuously while burst waveform captures at up to 16,384 S/sec provided high frequency waveforms.This post-mission paper provides the reader with information useful for accessing, understanding and using EFW data. Selected science results are discussed and used to highlight instrument capabilities. Science quantities, data quality and error sources, and analysis routines are documented.

The results of the "Pitch angle scattering of energetic electrons by bursty bulk flows (BBFs)" paper by W. W. Eshetu et al.

The concept of graphite?polyurethane coatings as efficient, electrical resistors is the focus of this paper. A 60?40 graphite?polyurethane mix (weight %) demonstrated an electrical resistivity of 40.71???mm. The graphite?polyurethane mix was coated on electrically insulating Kapton tape, which was then wrapped on a nichrome wire (nominal dimensions: 100?mm length and 1.5?mm diameter). This three-phase assembly was heated by Joule heating of the graphite?polyurethane layer. Steady state temperatures as high as 180??C were attained under free convection conditions, at a very low power requirement of about 2.5?W as opposed to about 18?W for uncoated wires. Interestingly, the effect on transients (heating and cooling times) was not as dramatic. Experiments were also performed under vacuum conditions, following which an analysis is offered regarding the different modes of heat transfer. These coatings can potentially be used as efficient resistors for highly conductive, moderately high temperature shape memory alloys (e.g.?the copper?aluminium?nickel system) or electrically insulating shape memory polymers. Any other thermally activated shape memory alloy (e.g.?the popular nickel?titanium system) may also use the coatings as resistors due to the potentially dramatic energy savings that may be realized without a dramatic adverse impact on the frequency response.

Data from satellite observations and theoretical simulations of ion heating in the magnetospheric cusp region are compiled in tables, graphs, and diagrams and discussed. Consideration is given to the mixing of ionospheric and magnetosheath plasmas, the instability of downward-flowing ring distributions of H(+) and He(2+) to lower-hybrid waves, and oxygen and hydrogen heating at finite k(parallel). A range of unstable propagation angles of + or - 20 deg about the perpendicular is estimated for M(H)/M(e) = 50, including superthermal and background electron dynamics.

A labscale hybrid rocket was used to study spectral bands produced by metal combustion. Bands in the ultraviolet visible region (300-750) are of interest. The rubber-like fuel, hydroxyl-terminated polybutadiene (HTPB), was doped with a metallic salt for introduction into the plume during combustion. When introduced, the metals produce atomic line emissions as well as molecular bands due to excited forms of metallic molecules formed in combustion. The most likely molecular band emissions are from the excited states of metal oxides or metal hydroxides formed by these metals in the presence of the oxygen flow of the hybrid rocket. As the concentration of metallic dopants increases in the flame, the molecular band emissions also increase. The fashion by which they increase is observed here. The high concentrations observed for these metals result in intensity versus concentration curves that alter from the expected linear progression for manganese, magnesium and strontium. The molecular band emissions observed for calcium, barium and copper in this study followed linear progression, as does the atomic line emission for barium. The line emissions for manganese, strontium and calcium lean toward the concentration axis. The curves are attributed to self-absorption or increased interactions among mixing species as metal concentration increases in the flame. A pattern-like combustion routine for each metal can be characterized with further study. Introduction Atomic spectral techniques have been used in the past to provide diagnostics for engine health monitoring. The National Aeronautics and Space Administration (NASA) and Stennis Space Center in particular have taken interest in these studies as health monitoring techniques for the Space Shuttle Main Engine (SSME).--' These techniques depend on the relationship of excited atomic species in the motor plume to the amounts introduced by failures in the engine system. It is important that a linear or otherwise describable and reproducible relationship exist, in order to be able to quantify wear or other elemental introduction factors in the motor or engine system. Molecular emissions as seen in the normal realm of atomic spectroscopy are viewed as interference. A classic example is that encountered with analysis of barium in the presence of calcium. The analytical atomic line of barium is swamped by the presence of an overwhelming molecular emission from calcium, such as CaOH. Steps are usually taken to minimize the presence of these molecular bands in such work. However, these type precautions are not applicable to the field of engine health monitoring or in combustion diagnostics when applied to exhaust plumes. Molecular emissions are present in rocket * Graduate Student, Student Member AIAA t Professor, Member of AIAA Copyright © 2000 by Keith Hudson. Published by the American Institute of Aeronautics and Astronautcs, Inc. with permission. 1 American Institute of Aeronautics and Astronautics (c)2000 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization. combustion, and should be factored in when quantitative data is required. A thorough study of the effect of molecular emissions in exhaust plumes is necessary to determine interference, fraction of species present as molecular versus atomic and other parameters. The Hybrid Rocket Facility at the University of Arkansas at Little Rock (UALR) was constructed to provide combustion diagnostic testing, and uses a 2 X 10 inch labscale hybrid thruster.' Previous studies have revealed the usefulness of the labscale hybrid rocket system as a plume simulator for other propulsion systems, and characterized it for both atomic and molecular emissions.'' ' The presence of molecular bands was noted in these studies, both from the combustion of HTBP fuel and as formed by metallic dopants, such as manganese. In order to study tike molecular bands in rocket plumes, the labscale hybrid rocket fuel was doped with various levels of metallic salts. Combustion of these salts results in band emissions attributed to metal oxides or metal hydroxides. Some of the metals were chosen due to their presence in alloys used in certain engine components, and because they appear to have produced molecular bands in previous combustion studies.8'10'11'12'13 Other metals were added to the study based on their tendency to oxidize easily, thus are likely to produce refractory particles in combustion.

An unprecedented in situ observation of the prompt formation of a new electron radiation belt along with the direct measurement of magnetic fields and electric fields was obtained by the CRRES satellite which was fortuitously situated at a distance of 2.55 RE near the equatorial plane at a local time of 0300 MLT during the March 24, 1991 SSC. A simulation shows that electrons with energies of a few MeV at L>6 were energized up to 40 MeV and transported to L≊2.5 during a fraction of their drift period. The energization process conserves the first adiabatic invariant and is enhanced due to resonance of the electron drift motion with the time‐varying electric field. Our simulation results reproduce the observed electron drift echoes and show that the interplanetary shock impacted the magnetosphere between 1500 and 1800 MLT. These results which were previously reported are extended by including more observations and more simulation diagnostics. We show that individual electrons can gain energy at the rate of hundreds of keV/s by interacting with the wave, that many previously trapped electrons are lost into interplanetary space, and that the relativistic electron distribution is greatly affected at all L>2 by the passage of the interplanetary shock.An unprecedented in situ observation of the prompt formation of a new electron radiation belt along with the direct measurement of magnetic fields and electric fields was obtained by the CRRES satellite which was fortuitously situated at a distance of 2.55 RE near the equatorial plane at a local time of 0300 MLT during the March 24, 1991 SSC. A simulation shows that electrons with energies of a few MeV at L>6 were energized up to 40 MeV and transported to L≊2.5 during a fraction of their drift period. The energization process conserves the first adiabatic invariant and is enhanced due to resonance of the electron drift motion with the time‐varying electric field. Our simulation results reproduce the observed electron drift echoes and show that the interplanetary shock impacted the magnetosphere between 1500 and 1800 MLT. These results which were previously reported are extended by including more observations and more simulation diagnostics. We show that individual electrons can gain energy at the rate of ...

The point raised by Omura (this issue) in his comment is well taken, and the authors have computed power spectra of the relevant quantities in their simulations to test the mechanism proposed by Omura et al. (1988) for parallel ion heating by electromagnetic ion cyclotron (EMIC) waves as it applies to the simulations of Omura et al. (1985) and Qian et al. (1990). The power spectra shown here were computed at a fixed point in space over the time interval 600-1000{Omega}{sup {minus}1}, inverse units of the hydrogen gyrofrequency, during the saturation phase of the instability, for the parameters of run II described by Qian et al. in their Figure 4. One sees a dominant peak at zero frequency, which supports the mechanism proposed by Omura et al. (1985, 1988) subsequent to their original simulations. At a lower amplitude one may observe components at frequencies 0.2, 0.374, and 0.64{Sigma}. They agree that the trapping mechanism by a stationary electrostatic potential has the most significant contribution to the parallel heating of cold ions. This heating involves sloshing of ions in an effective stationary potential well which is proportional to the perturbed magnetic field. The increase in the perturbed magnetic field increases themore » effective potential. This heating mechanism is different from acceleration by a wave with a finite phase velocity. Additional ion acceleration may be due to finite phase velocity waves and to stochastic heating by two counterstreaming waves.« less

Two related aspects of the linear mode conversion mechanism are considered: (1) the controlled heating of suprathermal ions in the ionosphere and magnetosphere over a powerful VLF/ELF transmitter using lower hybrid (LH) waves excited by the electromagnetic (EM) transmitter signals through linear mode conversion; (2) the excitation of intense LH waves in the auroral regions through the linear conversion of VLF/ELF EM auroral hiss, and the subsequent heating of ions by the excited LH waves. Experimental results are used to demonstrate that strong LH waves can be excited by EM waves down to frequencies as low as 2 kHz in the subauroral low-altitude magnetosphere. It is also shown that an approximately 250 kW VLF/ELF transmitter operating in the subauroral region at 2 kHz could excite sufficiently intense LH waves to heat suprathermal 1 eV H(+) ions and 16 eV O(+) ions to roughly 50 eV in a region extending in altitude from 1000 to 5000 km above the transmitter with a horizontal scale of about 500 km. If coherent wave stochastic heating occurs, the O(+) energy gain could be as large as 200 eV.

Electrostatic shocks and double layers are defined, discussed and compared with anomalous resistivity. It is suggested that turbulence and anomalous resistivity may provide local modification of particle distribution functions essential to the production of electrostatic shocks and double layers in space plasmas.

The coherent three-wave decay of a linearly unstable electrostatic hydrogen cyclotron (EHC) wave into stable EHC and ion acoustic modes is considered. The general problem of the three weakly interacting electrostatic normal modes in a Maxwellian plasma is discussed. EHC is examined in a fluid description, and the results are used to guide a similar study in a Vlasov plasma system intended to model the aurora acceleration region parameters. The time dependence of the decay in a simple three-wave interaction is presented in order to show how wave saturation can arise.