Engineering topics

Monson, S. J.

Publications and source records attributed to Monson, S. J..

16 records

NASA NTRS2011

Large Amplitude Whistlers in the Magnetosphere Observed with Wind-Waves

We describe the results of a statistical survey of Wind-Waves data motivated by the recent STEREO/Waves discovery of large-amplitude whistlers in the inner magnetosphere. Although Wind was primarily intended to monitor the solar wind, the spacecraft spent 47 h inside 5 R(sub E) and 431 h inside 10 R(sub E) during the 8 years (1994-2002) that it orbited the Earth. Five episodes were found when whistlers had amplitudes comparable to those of Cattell et al. (2008), i.e., electric fields of 100 m V/m or greater. The whistlers usually occurred near the plasmapause. The observations are generally consistent with the whistlers observed by STEREO. In contrast with STEREO, Wind-Waves had a search coil, so magnetic measurements are available, enabling determination of the wave vector without a model. Eleven whistler events with useable magnetic measurements were found. The wave vectors of these are distributed around the magnetic field direction with angles from 4 to 48deg. Approximations to observed electron distribution functions show a Kennel-Petschek instability which, however, does not seem to produce the observed whistlers. One Wind episode was sampled at 120,000 samples/s, and these events showed a signature that is interpreted as trapping of electrons in the electrostatic potential of an oblique whistler. Similar waveforms are found in the STEREO data. In addition to the whistler waves, large amplitude, short duration solitary waves (up to 100 mV/m), presumed to be electron holes, occur in these passes, primarily on plasma sheet field lines mapping to the auroral zone.

Kellogg, P. J.↗

NASA NTRS2010

Electron Trapping and Charge Transport by Large Amplitude Whistlers

Trapping of electrons by magnetospheric whistlers is investigated using data from the Waves experiment on Wind and the S/WAVES experiment on STEREO. Waveforms often show a characteristic distortion which is shown to be due to electrons trapped in the potential of the electrostatic part of oblique whistlers. The density of trapped electrons is significant, comparable to that of the unperturbed whistler. Transport of these trapped electrons to new regions can generate potentials of several kilovolts, Trapping and the associated potentials may play an important role in the acceleration of Earth's radiation belt electrons.

Kellogg, P. J.↗

NASA NTRS1993

Measurement of direct current electric fields and plasma flow speeds in Jupiter's magnetosphere

During the encounter of Ulysses with Jupiter, we have measured two components of the dc electric field and deduced from them the flow speed in the Io toms, as well as the presence of a polar cap region end what we interpret as a cleft region. Within the toms the flow speed is approximately equal to the speed of a plasma corotating with Jupiter but has significant deviations. The dominant deviations have an apparent period of the order of Jupiter's rotation period, but this might be a latitudinal effect. Other important periods are about 40 min and less than 25 min.

Kellogg, Paul J.↗

NASA NTRS1992

Low frequency magnetic signals associated with Langmuir waves

With the URAP experiment on Ulysses, low frequency signals with a magnetic component in close time correlation with electrostatic Langmuir waves at the plasma frequency are observed. In most, if not all, of these cases, the Langmuir waves are part of a Type III solar burst. This effect is investigated and it is shown that the low frequency waves are in the whistler mode and are most likely due to nonlinear effects involving Langmuir waves.

Kellogg, Paul J.↗

NASA NTRS1992

Evidence for Langmuir wave collapse in the interplanetary plasma

With the Fast Envelope Sampler part of the URAP experiment on Ulysses, there is observed much rapidly varying structure in plasma waves in the solar wind. Extremely narrow (1 ms) structures observed together with electrostatic Langmuir waves, as well as some broader Langmuir wave packets are discussed.

Kellogg, Paul J.↗

NASA NTRS1992

Observations of VHF emissions from 50-mA electron beam injections in the ionosphere that are associated with beam-induced discharges

Results are presented of observations of strong VHF plasma waves with amplitudes in excess of 0.1 mV/m (Hz)1/2 associated with 50 mA electron beam injections in the ionosphere. Data from three swept-frequency receivers carried on two daughter payloads are analyzed to determine the emission spectra of the electron beam for various energies and currents. These results were obtained from the rocket-borne experiment SCEX 3, NASA flight 39.002 UE, launched February 1, 1990. The accelerator payload also carried photometers, which measured luminosity at wavelengths of 391.4 and 380.5 nm. Several times during electron gun activity the measured luminosity increased much faster than proportional to the beam current. This nonlinear increase is evidence that a discharge is occurring in the vicinity of the accelerator payload. It is inferred from the uniform distribution of the luminosity around the accelerator payload that the observed discharge extends significantly outside the beam cylinder.

Goerke, R. T.↗

NASA NTRS1990

Observation of an antenna-plasma instability

This paper investigates the conditions leading to, and the causes of, the phenomenon observed during a rocket flight (to 585-km altitude) of an occasionally occurring narrow-band signal on an electric antenna whose frequency was found to vary as the rocket turned. The amplitude also varied by a factor larger than can be explained by variable coupling to the plasma; maximum oscillation amplitude occurred when the antenna was aligned with the earth's magnetic field. A tentative explanation of this phenomenon is given, suggesting that the signals on the antenna were caused by an interacton of the flowing plasma with sheath waves around the antenna.

Kellogg, P. J.↗

NASA NTRS1984

Observation of double-layer-like structures at rocket altitudes

Two hundred and thirty large amplitude electric field pulses in a rocket flight to an apogee of 585 km over an aurora have been observed. While the limitations of the instrumentation only allow limits to be set on the characteristics of these pulses, the limits are nevertheless significant. A typical lower limit on the potential jump of the pulses is about .4 volts. Many of the pulses show structure at a frequency very close (less than 2 percent) to the proton-cyclotron frequency.

Kellogg, P. J.↗

NASA NTRS1984

Further studies of auroral roar

Extended observations of auroral roar, a weak radio emission near the second harmonic of the electron cyclotron frequency, are reported. A total of 69 events were recorded and analyzed. Data for frequency band, duration, and local time of occurrence are presented. The height of the generation region is estimated to be 275-575 km.

Kellogg, P. J.↗

NASA NTRS1983

A second kind of Beam-Plasma Discharge (BPD): Rocket and laboratory results

It is shown that there are two types of beam plasma discharge observed in rocket shots. The second BPD transition (BPD2) is characterized by a very broad featureless emission extending from much less than the cyclotron frequency to several times the plasma frequency. The characteristic spectra observed close to the beam plasma discharge region are deformed by the intervening plasma when observations are made at a distance from the injection field line and lead to spectra which must be interpreted with care. In one case, the Bernstein mode at 2 fce seems to be a remnant of the broad, featureless spectrum of BPD2.

Kellogg, P. J.↗

NASA NTRS1982

Recent observations of beam plasma interactions in the ionosphere and a comparison with laboratory studies of the beam plasma discharge

Experimental results from an electron beam injection rocket flight (27:010 AE) launched into an active aurora are summarized. The rocket carried an accelerator which injected programmed electron beams of less than 100 ma at 2 and 4 kV into the ionospheric plasma over the altitude range 120-240 km. A major objective of the experiment was the study of beam-plasma interactions and the possible identification of the ignition of the beam-plasma discharge (BPD) which had been intensively studied in the laboratory. A qualitative assessment of the data indicates that BPD ignition was produced by both 10 ma and Im beams at 2 and 4 kV. Many of the observed characteristics are similar to the BPD characteristics observed in the laboratory.

Bernstein, W.↗

NASA NTRS1979

Further laboratory measurements of the beam-plasma discharge

The paper presents laboratory measurements of the beam-plasma discharge (BPD) produced when an energetic electron beam traverses an initially neutral gas. The results show that the critical beam current is related to energy, magnetic field, and the system length by an empirical relationship at pressures below 2 times 10 to the -5th power torr. This relationship describes the accumulation of ambient plasma density collisionally produced by the beam to a critical value at which ignition occurs. Additional measurements of the narrow-band cyclotron-related waves observed at beam currents below BPD threshold do not clearly establish whether this instability is a precursor to the BPD.

Bernstein, W.↗

NASA NTRS1979

Radio emissions from the aurora

Observations are reported of radio waves in the range 2.5-6 MHz, emitted by the aurora. Two distinct types of emissions are seen: bursts, which are broad band emissions with a time scale of the order of .1 sec, and roars, which are narrow band (300 kHz) emissions with a time scale of ten minutes.

Kellogg, P. J.↗

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

Rocket observation of high frequency waves over a strong aurora

High frequency waves in two frequency bands above the electron gyro frequency (1.6 MHz and 2.3 MHz) were observed by radio receivers carried on a sounding rocket as it passed over a strong aurora. Only the line at 2.3 MHz has a large magnetic component. Both 0.4s and 4s periods are present in much of the emissions. Good correlation is seen for a short time between the 2.3 MHz waves and 1.9 keV electrons detected on board the rocket.

Kellogg, P. J.↗

NASA NTRS1976

Whistler mode plasma waves observed on Electron Echo 2

Observations of whistler-mode waves associated with beams of electrons injected into the ionosphere are reported. The measurements are from the plasma-wave experiments carried on the Electron Echo 2 sounding rocket launched on September 24, 1972. Over 2000 electron injections were made with durations of 8 ms and 64 ms and pitch angles from 0 to 180 deg. The electric field receivers carried on the ejected nose cone observed strong whistler waves in the range from less than 100 kHz up to the electron cyclotron frequency of 1400 kHz. The whistler characteristics fall into four distinct types depending on pitch angle and gun energy. Both frequency and amplitude showed strong dependence on time from the start of the pulse and pitch angle. Cases of enhancement at the leading edge of a gun pulse, growth during a pulse, and echoes after the end of a pulse were all observed.

Monson, S. J.↗