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NASA NTRS1977

Observations of atomic oxygen /O/+// in the earth's magnetotail

The electrostatic analyzer aboard Imp 7 examined energy spectra of positive ions in certain streaming plasmas adjacent to the plasma sheet and within the geomagnetic tail at geocentric radial distances of about 35 R-E, revealing minor, though often persistent, secondary maxima of intensities with energy per unit charge a factor of 16 greater than that of the maxima corresponding to the dominant H(+) ions. The secondary maximum at higher E/Q was identified as a small flux of singly ionized atomic oxygen O(+), from the ionosphere. O(+) fluxes in the geomagnetic tail were about 10 to the 5th/(sq cm s) and imply O(+) upward fluxes in the upper ionosphere of about 10 to the 8th/(sq cm s). The kinetic energy of the oxygen ions is about 1-5 keV, while estimates of the global escape of the ions are about 3 x 10 to the 6th kg/yr.

Frank, L. A.↗

NASA NTRS1977

Mass-dependent channel electron multiplier operation

The absolute counting efficiency and pulse height distributions of a continuous-channel electron multiplier used in the detection of hydrogen, argon and xenon ions are assessed. The assessment technique, which involves the post-acceleration of 8-eV ion beams to energies from 100 to 4000 eV, provides information on counting efficiency versus post-acceleration voltage characteristics over a wide range of ion mass. The charge pulse height distributions for H2 (+), A (+) and Xe (+) were measured by operating the experimental apparatus in a marginally gain-saturated mode. It was found that gain saturation occurs at lower channel multiplier operating voltages for light ions such as H2 (+) than for the heavier ions A (+) and Xe (+), suggesting that the technique may be used to discriminate between these two classes of ions in electrostatic analyzers.

Fields, S. A.↗

NASA NTRS1977

Injun 5 observations of vehicle potential fluctuations at 2500 km

The AFGL spherical electrostatic analyzers aboard the polar orbiting Injun 5 satellite were designed to measure the temperature and density of the plasma as well as the vehicle potential. Significant vehicle potential fluctuations were observed at altitudes near 2500 km in the nighttime, topside ionosphere. At auroral latitudes, precipitating magnetospheric electrons frequently drove the satellite to such strongly negative potentials that the ambient electrons were shielded from instruments. In such cases, simultaneous measurements can be used to calculate the vehicle potential. Potentials of up to -40 volts were observed during impulsive precipitation events. Within the plasma trough, vehicle potentials varied between -1.5 and -4 volts, as compared with the -0.5 to -1 volt observed in the polar cap. The source of this vehicle potential enhancement was ascribed to fluxes of photoelectrons that have escaped from the sunlit conjugate ionosphere.

Sagalyn, R. C.↗

NASA NTRS1978

Heating of the ambient ionosphere by an artificially injected electron beam

An electrostatic analyzer on the electron accelerator of the Electron Echo 2 experiment showed that the electrons of the background plasma were heated to 10,000 K or more within 8 ms of the start of gun pulses. The degree of heating was dependent on the orientation of the rocket with respect to the magnetic field but was not measurably dependent on ambient electron density, neutral atmosphere density, or on the pitch angle at which the 40-keV electron beam was injected. This heating was also accompanied by an increase of plasma density. No evidence was found for an ion-free region around the rocket during gun pulses. These observations show that significant amounts of ionization are taking place around the rocket. During part of the flight a two-temperature electron distribution was found. It is believed that the high-temperature part of these distributions represents secondaries produced by the beam.

Cartwright, D. G.↗

NASA NTRS1978

Energization of polar cusp electrons at the noon meridian

Observations of electron energization in the polar cusp demonstrate the influence of the sign of the elevation angle of the interplanetary magnetic field (IMF) on the polar cusp electron spectra; the evidence indicates that the energization process occurs only at the near-noon hours of local time. The observations were made by an electrostatic analyzer on board the polar-orbiting Ariel-4 satellite. In particular, the electron intensities noted at energies greater than about 700 eV when the IMF elevation angle exceeded zero deg show an enhancement in comparison with the intensities registered at IMF elevation angles less than zero deg.

Craven, J. D.↗

NASA NTRS1978

An experiment to measure interplanetary and solar electrons

The paper describes an ISEE experiment designed to study interplanetary and solar electrons in the energy range between solar wind and galactic cosmic rays. The instrumentation is designed to identify and measure electron fluxes with high energy resolution and high sensitivity from approximately 2 keV to 1 MeV. Angular distributions of these electrons will also be obtained; in addition, energetic ions above 50 keV will be measured. Measurements of particle acceleration in solar flares, solar radio emission, interplanetary particles and shock wave acceleration, and low energy electron propagation are discussed. The instrumentation is described with emphasis on the semiconductor telescopes, the electrostatic analyzer, and the electronics.

Anderson, K. A.↗

NASA NTRS1978

ISEE-C solar wind plasma experiment

Two 135 deg spherical section electrostatic analyzers furnish electron and ion measurements of the solar wind on ISEE-C. Each of these instruments utilizes a divided secondary emitter system to intercept the analyzed particles. Secondary electrons selected from all of the emitters simultaneously provide fast two-dimensional measurements of the particle fluxes integrated over polar angle; at a slower rate secondary electrons are successively selected from individual emitters to provide three-dimensional measurements. Speed of the ion measurements is increased by a factor of two by using an active proton peak tracking system to reduce the total range of energy per charge which has to be covered.

Bame, S. J.↗

NASA NTRS1978

An experiment to study energetic particle fluxes in and beyond the earth's outer magnetosphere

This experiment is designed to take advantage of the ISEE Mother/Daughter dual spacecraft system to study energetic particle phenomena in the earth's outer magnetosphere and beyond. Large geometric factor fixed voltage electrostatic analyzers and passively cooled semiconductor detector telescopes provide high time resolution coverage of the energy range from 1.5 to 300 keV for both ions and electrons. Essentially identical instrumentation is placed on the two spacecraft to separate temporal from spatial effects in the observed particle phenomena.

Anderson, K. A.↗

NASA NTRS1978

ISEE-1 and ISEE-2 fast plasma experiment and the ISEE-1 solar wind experiment

Identical fast plasma experiment (FPE) systems were placed on the ISEE-1 and ISEE-2 spacecraft. The FPE consists of three high efficiency 90 deg spherical section electrostatic analyzers using large secondary emitters and discrete dynode multipliers to detect analyzed particles. Two of them, viewing in opposite directions, produce complete 2D velocity distribution measurements of both protons and electrons every spacecraft revolution. A third FPE analyzer with a divided emitter measures 3D distributions at a slower rate. ISEE-1 also carries a solar-wind experiment (SWE) to measure solar-wind ions with high resolution. The SWE is composed of two 150 deg spherical section analyzers using the same set of plates. The two acceptance fans are tilted with respect to each other so that 3D characteristics of the ion distributions can be derived.

Bame, S. J.↗

NASA NTRS1978

The electron spectrometer experiment on ISEE-1

A six-axis electron spectrometer for the ISEE-1 spacecraft is described and some typical early results presented. This instrument, designed for three-dimensional plasma distribution function studies in the solar wind, magnetosheath, outer magnetosphere, and near tail regions, has three energy ranges: 7.5-512 eV, 11-2062 eV, and 109-7285 cV, respectively. Two channel electron multipliers are used at the output of each of six cylindrical electrostatic analyzers. The total mass of two sensors and a data processing unit is 4.9 kg and the power comsumption is 3.5 W. Two hundred information bits/s telemetry rate is required.

Ogilvie, K. W.↗

NASA NTRS1979

A rocket-borne data-manipulation experiment using a microprocessor

The development of a data-manipulation experiment using a Z-80 microprocessor is described. The instrumentation is included in the payloads of two Nike Apache sounding rockets used in an investigation of energetic particle fluxes. The data from an array of solid-state detectors and an electrostatic analyzer is processed to give the energy spectrum as a function of pitch angle. The experiment performed well in its first flight test: Nike Apache 14.543 was launched from Wallops Island at 2315 EST on 19 June 1978. The system was designed to be easily adaptable to other data-manipulation requirements and some suggestions for further development are included.

Davis, L. L.↗

NASA NTRS1979

Calculation of total cross sections for charge exchange in molecular collisions

Areas of investigation summarized include nitrogen ion-nitrogen molecule collisions; molecular collisions with surfaces; molecular identification from analysis of cracking patterns of selected gases; computer modelling of a quadrupole mass spectrometer; study of space charge in a quadrupole; transmission of the 127 deg cylindrical electrostatic analyzer; and mass spectrometer data deconvolution.

Ioup, J.↗

NASA NTRS1980

Hourly average values of solar wing parameters (flow rate and ion temperatures) according to data of measurements of the Venera-9 and Venera-10 automatic interplanetary stations on an Earth-Venus during the period June 1975 - April 1976

Four electrostatic analyzers with channel electron multipliers as detectors were used to measure solar wind ionic flow. The axes of the fields of vision of two of these analyzers were directed along the axis of the automatic interplanetary station, oriented towards the Sun, while the other two were turned in one plane at angles of +15 deg and -15 deg. The full hemisphere of the angular diagram of each analyzer was approximately 5 deg. The energetic resolution was approximately 6%, and the geometric energy was 0.002 sq cm ave. keV. Each analyzer covered an energetic range of approximately 10 in eight energetic intervals. Spectral distributions were processed in order to obtain the velocity and temperature of the protons. Tabular data show the hour interval (universal time) and the average solar wind velocity in kilometers per second.

Vaysberg, O. L.↗

NASA NTRS1979

Fluctuations of inverted V electron fluxes

Fluctuations of low-energy electron fluxes during an inverted V event on Nov. 5, 1975 were detected by fixed-energy electrostatic analyzers used in the LEE (low-energy electron) experiment onboard the AE-D satellite. The flux fluctuations were observed at energies of 0.78, 1.38, and 2.62 keV, when these energies were below that of the monoenergetic beam. This suggests that the fluctuations might occur over a wide range of energies. The fluctuations were confined within a pitch angle of 15 degrees, the amplitude increasing with decreasing pitch angle. The oscillation frequencies centered around 1.75 Hz. Fluctuations at two energies were generally correlated. The heating of secondary electrons, deduced from an analysis of the distribution function, is attributed to anomalous heating by electron plasma wave turbulence, whose intensity was modulated by a low-frequency wave. The results are consistent with a model, according to which auroral precipitating electron beams enhance the anomalous resistivity at the topside ionosphere through parametric instabilities.

Lin, C. S.↗

NASA NTRS1980

Rocket measurements of energetic particles in the midlatitude precipitation zone

Measurements of energetic ion and electron properties as a function of altitude in the midlatitude zone of nighttime energetic particle precipitation are reported. The measurements of particle fluxes, energy spectra and pitch angle distributions were obtained by a Langmuir probe, six energetic particle spectrometers and an electrostatic analyzer on board a Nike Apache rocket launched near the center of the midlatitude zone during disturbed conditions. It is found that the incident flux was primarily absorbed rather than backscattered, and consists of mainly energetic hydrogen together with some helium and a small energetic electron component. Observed differential energy spectra of protons having an exponential energy spectrum, and pitch angle distributions at various altitudes indicate that the energetic particle flux decreases rapidly for pitch angles less than 70 deg. An energetic particle energy flux of 0.002 ergs/sq cm per sec is calculated which indicates the significance of energetic particles as a primary nighttime ionization source for altitudes between 120 and 200 km in the midlatitude precipitation zone.

Voss, H. D.↗

NASA NTRS1981

Determining the electron energy distribution near the plasma potential in the earth's ionosphere

A determination of the plasma potential using an electrostatic analyzer is described in which the potential difference between the instrument slit system and surrounding plasma is minimized. Data obtained from rocket-borne instrumentation demonstrate the viability of this technique for electron fluxes between thermal energies (about 0.5 V) and suprathermal energies (many volts).

Sharp, W. E.↗

NASA NTRS1981

Inference of the ring current ion composition by means of charge exchange decay

The analysis of data from the Explorer 45 (S3-A) electrostatic analyzer in the energy range 5-30 keV has provided some new results on the ring current ion composition. It has been well established that the storm time ring current has a decay time of several days, during which the particle fluxes decrease nearly monotonically. By analyzing the measured ion fluxes during the several day storm recovery period and assuming that beside hydrogen other ions were present and that the decays were exponential in nature, three separate lifetimes for the ions were established. These fitted decay lifetimes are in excellent agreement with the expected charge exchange decay lifetimes for H(+), O(+) and He(+) in the energy and L value range of the data.

Smith, P. H.↗

NASA NTRS1981

Non-E x B ordered ion beams upstream of the earth's bow shock

The unexpected appearance of spin modulations in the fixed voltage electrostatic analyzer detectors on ISEE 1 and 2 has made it possible to study the plasma properties of the upstream ions in high time resolution. Using an isotropic flowing Maxwellian distribution to model the count rate modulations, estimates have been obtained of the local plasma temperature and three-dimensional flow velocity of the observed upstream ion population. It is found that in almost all of the observations of upstream particles there exist beam-like ions with temperatures in the range 5-80 eV. Their flow velocities cannot be ordered by E x B. This last point separates these observations from the previously reported reflected and diffuse populations of upstream ions. Mechanisms that can gyrophase bunch the ions reflected at the bow shock are discussed as a method of explaining the data.

Gurgiolo, C.↗