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Results for “CYCLOTRON RESONANCE”

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NASA NTRS1992

Ion-cyclotron waves at Jupiter - Possibility of detection by Ulysses

Recent thermal plasma data and a computer code by Horne (1989) are employed to evaluate the linear-path-integrated gain of waves propagating through the Io to predict the Jovian plasma-wave environment. Estimates of the nonlinear saturation amplitudes are utilized with the thermal plasma data from two frequency bands to study the convective growth of the ion-cyclotron (IC) waves. Strong cyclotron resonant damping is theorized to prevent wave propagation to the lower latitudes, and the thermal plasma and cyclotron resonant energetic ions are expected to further confine the IC waves. L-mode waves below the O(+) gyrofrequency in the equatorial region of the torus are shown to inhabit an unstable region. The IC waves probably achieve nonlinear amplitudes regardless of plasma properties due to the rapid amplification in this region. It is suggested that the Ulysses data complicate the identification of the waves because the magnetometer is not adequately sensitive and because of the low frequency of the plasma-wave detector.

Mei, YI↗

NASA NTRS1995

Deposition of diamond-like films by ECR microwave plasma

Hard amorphous hydrogenated carbon, diamond-like films are deposited using an electron cyclotron resonance microwave plasma with a separate radio frequency power bias applied to a substrate stage. The electron cyclotron resonance microwave plasma yields low deposition pressure and creates ion species otherwise unavailable. A magnetic mirror configuration extracts special ion species from a plasma chamber. Different levels of the radio frequency power bias accelerate the ion species of the ECR plasma impinging on a substrate to form different diamond-like films. During the deposition process, a sample stage is maintained at an ambient temperature of less than 100.degree. C. No external heating is applied to the sample stage. The deposition process enables diamond-like films to be deposited on heat-sensitive substrates.

Shing, Yuh-Han↗

NASA NTRS1983

On the preferential acceleration and heating of solar wind heavy ions

It is pointed out that the properties of solar wind ions heavier than H(+) have presented a puzzle to theorists for some time. The most recent theoretical efforts to explain the observations are considered, taking into account studies conducted by Dusenbery and Hollweg (1981) and Marsch et al. (1982). The first model of a wave-driven, three-fluid, supersonic solar wind is considered. Details of the resonant wave-particle interaction are discussed and the relevant equations for the model are derived. An investigation is conducted of the effects of resonant cyclotron acceleration and heating by a spectrum of nondispersive ion cyclotron waves on the model. It is found that there are serious difficulties with the hypothesis that the resonant cyclotron interaction is responsible for the preferential heating and acceleration of heavy ions in the solar wind. The model presented here is unable to produce the required energization by this mechanism. However, this model should be viewed as an approximate one, subject to possible correction by more advanced calculations.

Isenberg, P. A.↗

NASA NTRS2005

RF Stabilization for Storage of Antiprotons

Portable storage of antimatter is an important step in the experimental exploration of antimatter in propulsion applications. The High Performance Antiproton Trap (HiPAT) at NASA Marshall Space Flight Center is a Penning-Malmberg ion trap being developed to trap and store low energy antiprotons for a period of weeks. The antiprotons can then be transported for use in experiments. HiPAT is being developed and evaluated using normal matter, before an attempt is made to store and transport antiprotons. Stortd ions have inherent instabilities that limit the storage lifetime. RF stabilization at cyclotron resonance frequencies is demonstrated over a period of 6 days for normal matter ion clouds. A variety of particles have been stored, including protons, C+ ions, and H2+ ions. Cyclotron resonance frequencies are defined and experimental evidence presented to demonstrate excitation of cyclotron waves in the plasma for all three species of ions.

Pearson, J. Boise↗

NASA NTRS1989

An RF heated tandem mirror plasma propulsion study

Experimental results on a tandem mirror hybrid plume rocket involving a three-stage system of plasma injection, heating, and subsequent injection through a magnetic nozzle are presented. In the experiments, a plasma is created by breaking down the gas with electron cyclotron resonance heating at 2 kW in the central cell, and the ion species is then heated to high temperatures with ion cyclotron resonance heating at 10 kW in the end cell. A Langmuir probe measured an electron density of 2.5 x 10 to the 16th/cu m and a temperature of 100 eV in the central cell and an ion density of 1.25 x 10 to the 17th/cu m and a temperature of 500 eV in the end cell.

Yang, T. F.↗

NASA NTRS1999

Nonlinear Effects in Single-Pass ICRF Heating

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept employs Ion Cyclotron Resonant Frequency (ICRF) heating as the main power deposition mechanism. Since the ions accelerate to the full energy in a single pass through the cyclotron resonance, their response to the RF-field will be essentially nonlinear - hence the motivation to amend the commonly used linear approach to the problem. In a collisionless plasma, the energy gain of an accelerated ion is limited by the time the particle spends at the resonance. This time is affected by: (1) incident flow velocity, (2) longitudinal grad B force, (3) ambipolar electric field, and (4) ponderomotive force of the RF-field. Our analysis shows that the grad B force is the dominant factor at low to moderate levels of RF-power. We present nonlinear scaling for the energy gain and the absorption efficiency with RF-power and plasma parameters. We also demonstrate that the nonlinear regime exhibits a steep decrease in the plasma density at the resonance.

Arefiev, A. V.↗

NASA NTRS1989

ULF waves at Comets Halley and Giacobini-Zinner - Comparison with theory

Because the Doppler shift occurring in ion-cyclotron resonance is equal and opposite to that associated with the flow of the solar wind plasma past the observer, one should be able to monitor the amplitude of waves due to the cyclotron resonant instability by examining the amplitude of waves near the gyrofrequency of the respective ions as measured in the spacecraft frame. This expectation has been checked by using one-dimensional electromagnetic hybrid simulations of two ion pickup. This simplifies the comparison of theoretical predictions of wave growth with the observations. Distant from both comets the wave amplitudes are very weak. As the comet is approached the wave amplitude grows. These observations agree qualitatively with the simulations which predict amplitudes that depend on the properties of the injected beams and the local injection rate.

Le, G.↗

NASA NTRS1994

Energy transfer between energetic ring current H(+) and O(+) by electromagnetic ion cyclotron waves

Electromagnetic ion cyclotron (EMIC) waves in the frequency range below the helium gyrofrequency can be excited in the equatorial region of the outer magnetosphere by cyclotron resonant instability with anisotropic ring current H(+) ions. As the unducted waves propagate to higher latitudes, the wave normal should become highly inclined to the ambient magnetic field. Under such conditions, wave energy can be absorbed by cyclotron resonant interactions with ambient O(+), leading to ion heating perpendicular to the ambient magnetic field. Resonant wave absorption peaks in the vicinity of the bi-ion frequency and the second harmonic of the O(+) gyrofrequrency. This absorption should mainly occur at latitudes between 10 deg and 30 deg along auroral field lines (L is greater than or equal to 7) in the postnoon sector. The concomitant ion heating perpendicular to the ambient magnetic field can contribute to the isotropization and geomagnetic trapping of collapsed O(+) ion conics (or beams) that originate from a low-altitude ionospheric source region. During geomagnetic storms when the O(+) content of the magnetosphere is significantly enhanced, the absorption of EMIC waves should become more efficient, and it may contribute to the observed acceleration of O(+) ions of ionospheric origin up to ring current energies.

Thorne, Richard M.↗

NASA NTRS1971

Photodissociation of the CH3Cl/+/ and N2O/+/ cations.

Use of the ion cyclotron resonance (icr) technique to observe the photodissociation of the cations CH3Cl(+) and N2O(+) in the gas phase. Ions were trapped in the icr cell for periods of the order of seconds, which permitted the photodissociation process to be observed with wavelength-selected light. A cyclotron resonance ejection technique was employed to show that CH3Cl(+) ions were being dissociated rather than the CH3ClH(+) ions which were also present. The photodissociation cross section for N2O(+) was found to be without strong wavelength dependence between 4000 and 6500 A. The cross section for CH3Cl(+) showed a large peak at 3150 A. Possible assignments of this peak are considered, and it is suggested that a photodissociation occurs through an ion excitation involving a change in occupation of the bonding or antibonding orbitals of the C-Cl bond.

Dunbar, R. C.↗

NASA NTRS1988

Energy dependent pitch angle distributions of auroral primary electrons

Double-layer/parallel-electric field accelerations and the subsequent electron-beam plasma interactions involving Cerenkov and anomalous cyclotron resonances are considered. It is found that these phenomena yield pitch angle distributions as noted from rocket and satellite studies. Although the electron acceleration by weak parallel electric fields forming a runaway electron tail is limited to a critical parallel energy determined by the anomalous cyclotron resonance, such a limitation does not occur with acceleration by a localized parallel electric field such as that in a double layer.

Singh, N.↗

NASA NTRS1990

Ion heating by broadband low-frequency waves in the cusp/cleft

Ion heating via a cyclotron resonance process involving waves near the ion gyrofrequency is studied using data from two cusp/cleft crossings of the polar-orbiting DE 1 satellite. Observed cool O(+) distributions and wave intensities from one orbit are used as input to a Monte Carlo simulation. The results show that cyclotron resonance heating by broadband low-frequency waves can cause a major part of the ion heating observed in the cusp/cleft.

Andre, Mats↗

NASA NTRS2001

Models for X-Ray Emission from Isolated Pulsars

A model is proposed for the observed combination of power-law and thermal X-rays from rotationally powered pulsars. For gamma-ray pulsars with accelerators very many stellar radii above the neutron star surface, 100 MeV curvature gamma-rays from e(-) or e(+) flowing starward out of such accelerators are converted to e1 pairs on closed field lines all around the star. These pairs strongly affect X-ray emission from near the star in two ways. (1) The pairs are a source of synchrotron emission immediately following their creation in regions where B approx. 10(exp 10) G. This emission, in the photon energy range 0.1 keV less than E(sub X) less than 5 MeV, has a power-law spectrum with energy index 0.5 and X-ray luminosity that depends on the back-flow current, and is typically approx. 10(exp 33) ergs/ s. (2) The pairs ultimately a cyclotron resonance "blanket" surrounding the star except for two holes along the open field line bundles which pass through it. In such a blanket the gravitational pull on e(+,-) pairs toward the star is balanced by the hugely amplified push of outflowing surface emitted X-rays wherever cyclotron resonance occurs. Because of it the neutron star is surrounded by a leaky "hohlraum" of hot blackbody radiation with two small holes, which prevents direct X-ray observation of a heated polar cap of a gamma-ray pulsar. Weakly spin modulated radiation from the blanket together with more strongly spin-modulated radiation from the holes through it would then dominate observed low energy (0.1-10 keV) emission. For non-y-ray pulsars, in which no such accelerators with their accompanying extreme relativistic back-flow toward the star are expected, optically thick e1 resonance blankets should not form (except in special cases very close to the open field line bundle). From such pulsars blackbody radiation from both the warm stellar surface and the heated polar caps should be directly observable. In these pulsars, details of the surface magnetic field evolution, especially of polar cap areas, become relevant to observations. The models are compared to X-ray data from Geminga, PSR 1055-52, PSR 0656+14, PSR 1929+10, and PSR 0950+08.

Wang, F. Y.-H.↗

NASA NTRS1985

The propagation and growth of whistler mode waves generated by electron beams in earth's bow shock

In this study, the propagation and growth of whistler mode waves generated by electron beams within earth's bow shock is investigated using a planar model for the bow shock and a model electron distribution function. Within the shock, the model electron distribution function possesses a field-aligned T greater than T beam that is directed toward the magnetosheath. Waves with frequencies between about 1 and 100 Hz with a wide range of wave normal angles are generated by the beam via Landau and anomalous cyclotron resonances. However, because the growth rate is small and because the wave packets traverse the shock quickly, these waves do not attain large amplitudes. Waves with frequencies between about 30 and 150 Hz with a wide range of wave normal angles are generated by the beam via the normal cyclotron resonance. The ray paths for most of these waves are directed toward the solar wind although some wave packets, due to plasma convection travel transverse to the shock normal. These wave packets grow to large amplitudes because they spend a long time in the growth region. The results suggest that whistler mode noise within the shock should increase in amplitude with increasing upstream theta sub Bn. The study provides an explanation for the origin of much of the whistler mode turbulence observed at the bow shock.

Tokar, R. L.↗

NASA NTRS2010

Design of a Microwave Assisted Discharge Inductive Plasma Accelerator

A new plasma accelerator concept that employs electrodeless plasma preionization and pulsed inductive acceleration is presented. Preionization is achieved through an electron cyclotron resonance discharge that produces a weakly-ionized plasma at the face of a conical theta pinch-shaped inductive coil. The presence of the preionized plasma allows for current sheet formation at lower discharge voltages than those found in other pulsed inductive accelerators. The location of an electron cyclotron resonance discharge can be controlled through the design of the applied magnetic field in the thruster. A finite-element model of the magnetic field was used as a design tool, allowing for the implementation of an arrangement of permanent magnets that yields a small volume of preionized propellant at the coil face. This allows for current sheet formation at the face of the inductive coil, minimizing the initial inductance of the pulse circuit and maximizing the potential efficiency of the new accelerator.

Hallock, Ashley K.↗

NASA NTRS2017

Identifying Ultra Low Frequency Waves in the Lunar Plasma Environment Using Trajectory Analysis and Resonance Conditions

Abstract Recent studies show that localized crustal magnetic fields on the lunar surface can reflect a significant portion of the incoming solar wind protons. These reflected ions can drive a wide range of plasma waves. It is difficult to determine the intrinsic properties of low-frequency waves with single-spacecraft observations, which can be heavily Doppler shifted. We describe a technique to combine trajectory analysis of reflected protons with the Doppler shift and resonance conditions to identify ultralow-frequency waves at the Moon. On 31 January 2014 plasma waves were detected by one of the Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) probes as it approached the lunar wake; these waves were not detected by the second ARTEMIS probe located upstream in the undisturbed solar wind. The observed waves had a frequency below the local ion cyclotron frequency and had right-hand circular polarization in the reference frame of the Moon. By solving the Doppler shift and the cyclotron resonance equations, we determined the conditions for reflected ions to excite the observed waves. Simulated trajectories of reflected ions correspond to ARTEMIS ion observations and support the hypothesis that reflected ions are the primary driver of the waves. By combining trajectory analysis with the resonance conditions, we identify scenarios where ions that satisfy the resonance conditions are present in the right location to generate the observed waves. Using this method, we can uniquely identify the observed waves as upstream propagating right-hand polarized waves, subject to the assumption that they are generated by cyclotron resonance with ions.

Magnetic↗

NASA NTRS2002

Variable Specific Impulse Magnetoplasma Rocket Engine

An engine is disclosed, including a controllable output plasma generator, a controllable heater for selectably raising a temperature of the plasma connected to an outlet of the plasma generator, and a nozzle connected to an outlet of the heater, through which heated plasma is discharged to provide thrust. In one embodiment, the source of plasma is a helicon generator. In one embodiment, the heater is an ion cyclotron resonator. In one embodiment, the nozzle is a radially diverging magnetic field disposed on a discharge side of the heater so that helically travelling particles in the beater exit the heater at high axial velocity. A particular embodiment includes control circuits for selectably directing a portion of radio frequency power from an RF generator to the helicon generator and to the cyclotron resonator so that the thrust output and the specific impulse of the engine can be selectively controlled. A method of propelling a vehicle is also disclosed. The method includes generating a plasma, heating said plasma, and discharging the heated plasma through a nozzle. In one embodiment, the nozzle is a diverging magnetic field. In this embodiment, the heating is performed by applying a radio frequency electro magnetic field to the plasma at the ion cyclotron frequency in an axially polarized DC magnetic field.

Franklin R Chang-Diaz↗

NASA NTRS1995

The soft gamma-ray spectrum of A0535+26: Detection of an absorption feature at 110 keV by OSSE

We present soft gamma-ray observations by the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory (GRO) of the transient X-ray binary pulsar A0535+26. The observations were made 1994 February 8-17, immediately prior to the peak of a giant outburst. The phase averaged spectrum is complex and cannot be described by a single-component model. We find that structure in the spectrum above 100 keV can best be modeled by an absorption feature near 110 keV, which we interepret as the signature of cyclotron resonant scattering. Because of OSSE's 45 keV threshold, we are unable to make a definitive statement on the presence of a 55 keV absorption line; however, we can conclude that if this line does exist, it must have a smaller optical depth than the line at 110 keV. A first harmonic (=fundamental) cyclotron resonance at 110 keV corresponds to a magnetic field strength at the surface of the neutron star of approximately 1 x 10(exp 13) G (approximately 5 x 10(exp 12) G if the first harmonic is at 55 keV).

Grove, J. E.↗

NASA NTRS2010

Design of a Microwave Assisted Discharge Inductive Plasma Accelerator

The design and construction of a thruster that employs electrodeless plasma preionization and pulsed inductive acceleration is described. Preionization is achieved through an electron cyclotron resonance discharge that produces a weakly-ionized plasma at the face of a conical theta pinch-shaped inductive coil. The presence of the preionized plasma allows for current sheet formation at lower discharge voltages than those employed in other pulsed inductive accelerators that do not employ preionization. The location of the electron cyclotron resonance discharge is controlled through the design of the applied magnetic field in the thruster. Finite element analysis shows that there is an arrangement of permanent magnets that yields a small volume of resonant magnetic field at the coil face. Preionization in the resonant zone leads to current sheet formation at the coil face, which minimizes the initial inductance of the pulse circuit and maximizes the potential electrical efficiency of the accelerator. A magnet assembly was constructed around an inductive coil to provide structural support to the selected arrangement of neodymium magnets. Measured values of the resulting magnetic field compare favorably with the finite element model.

Hallock, Ashley K.↗