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At least 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Observations of a free-energy source for intense electrostatic waves

Significant progress has been made in understanding intense electrostatic waves near the upper hybrid resonance frequency in terms of the theory of multiharmonic cyclotron emission using a classical loss-cone distribution function as a model. Recent observations by Hawkeye 1 and GEOS 1 have verified the existence of loss-cone distributions in association with the intense electrostatic wave events, however, other observations by Hawkeye and ISEE have indicated that loss cones are not always observable during the wave events, and in fact other forms of free energy may also be responsible for the instability. Now, for the first time, a positively sloped feature in the perpendicular distribution function has been uniquely identified with intense electrostatic wave activity. Correspondingly, we suggest that the theory is flexible under substantial modifications of the model distribution function.

Kurth, W. S.↗
NASA NTRS1980

Deceleration of the solar wind upstream from the earth's bow shock and the origin of diffuse upstream ions

Observations with the Los Alamos Scientific Laboratory/Max-Planck-Institut crossed-fan solar wind ion experiment on ISEE I reveal that the solar wind is decelerated and deflected away from the direction of the earth's bow shock as it enters that portion of the upstream region populated by diffuse bow shock ions and long-period (10-60 s) waves. Typically, the average directed velocity vector changes by 7-10 km/s as it enters the wave region. At times, average speed changes as large as 25-40 km/s are observed. Superposed upon these changes in average flow speed are large amplitude (+ or - 15) fluctuations in flow speed associated with the waves themselves. The observations suggest that the solar wind deceleration is the result of momentum transfer from reflected bow shock ions to the wind via the long-period waves as the reflected ion beams go unstable. The broad angular distributions of the diffuse ions thus appear to be produced as a consequence of the disruption of reflected ion beams.

Bame, S. J.↗
NASA NTRS1980

Magnetopause characteristics at 0840-1040 hours local time

An analysis of three-dimensional energetic particle distributions for 14 consecutive ISEE satellite orbits during magnetopause crossings and close approaches is presented. The data were collected from the Nov. 10 through Dec. 11, 1977, time period and cover local times of 0840 to 1040 hours. It was found that the magnetopause in this period defined by energetic particles can be represented as sharp particles and a well defined boundary for magnetospherically trapped particles for a wide range of magnetospheric activity and magnetosheath field conditions. The magnetopause position, orientation, and velocity were determined for all identified magnetopause crossings and close approaches using the technique of Williams (1979); it was found that the magnetopause is nearly always in motion with velocities ranging from near zero to at least plus or minus 25 km/s. Correlations with published plasma, magnetic field, and plasma wave magnetopause identifications show the energetic particle results to be accurate and an important factor in determining magnetopause characteristics and behavior.

Williams, D. J.↗
NASA NTRS1980

A test of two theories for the low-frequency cutoffs of nonthermal continuum radiation

A discussion and analysis of two theories that differently identify the low-frequency cutoffs of nonthermal continuum radiation are presented. The cold plasma theory and an alternate one proposed by Jones (1976) are compared experimentally with the use of continuum radiation data obtained in the outer magnetosphere by the Imp 6 and ISEE 1 spacecraft. It is found that the characteristics of this specific radiation are consistent with those expected of ordinary and extraordinary mode waves described by the cold plasma theory and it is shown that the cutoff frequencies occur at the local plasma frequency and R = 0 cutoff frequency as proposed by the same theory. The inconsistencies which were found between the Jones theory (1976) and observation are presented, and in addition no evidence is found for a component of continuum radiation propagating in the Z mode in the outer magnetosphere.

Shaw, R. R.↗
NASA NTRS1980

Energization of solar wind ions by reflection from the earth's bow shock

The existence of ion beams with energies a few times the solar wind energy and streaming outward from the earth's bow shock has been known for some time. To explain the observed ion energies, a simple reflection model has been proposed in which the particles gain energy by displacement parallel to the interplanetary electric field. In this model the energy gained in the reflection can be described as a function of the angles between the interplanetary magnetic field, the solar wind velocity, and the local shock normal. Ion beams under widely varying conditions have been observed in ISEE 1 and 2. For 18 cases, with beam energies ranging from approximately 1.4 to 30 times the solar wind energy, a comparison between the observed and the predicted beam energies has been made.

Paschmann, G.↗
NASA NTRS1980

On temperature and speed of He/2+/ and O/6+/ ions in the solar wind

First results on fluid parameters of heavy ions in the solar wind from ISEE-1 mass spectrometer data are presented. Temperatures and speeds of the He(2+) and O(6+) ions have been determined for about 150 hours of data in late 1977. It is found that the temperatures are roughly proportional to atomic mass of the ion species. When temperatures are comparatively low, this proportionality does not hold for H(+). At high speeds and high temperatures the minor ions stream somewhat faster than H(+), but there is on average practically no difference between speeds of He(2+) and O(6+).

Schmidt, W. K. H.↗
NASA NTRS1980

A cosmic-ray age based on the abundance of Be-10

The paper discusses a measurement of the isotopic composition of galactic cosmic-ray beryllium made with high resolution aboard the ISEE 3 spacecraft. The isotope fractions of Be-7, Be-9, and Be-10 were determined; the abundance of the radioactive isotope Be-10 is used to deduce the cosmic-ray confinement time of 8,400,000/yr and an interstellar gas density of 0.33 atoms/cu cm in the confinement volume. Errors in the propagation model parameters which result in comparable uncertainties are discussed.

Wiedenbeck, M. E.↗
NASA NTRS1980

Distribution functions of type III electrons observed in interplanetary space

Simultaneous energetic electron and solar radio observations from the ISEE-3 spacecraft of several solar type III radio bursts are analyzed and discussed. Two types of electron events are found: (1) normal flare associated electron events in the 20 to greater than 100 keV range, and (2) low energy, 2 to 10 keV, electron events which appear to be associated with individual type III bursts from low frequency type III storms. The arrival direction and frequency of the radio emission are identified and the temporal behavior of the in situ radio intensity and the electron intensity are compared. Calculations of the electron velocity distribution function parallel to the magnetic field are made, implying that for electron events above 20 keV, scattering in the pitch angle is significant in modifying this function.

Lin, R. P.↗
NASA NTRS1980

Whistler mode wave packets in the earth's foreshock region

Measurements of the velocity of discrete whistler-mode wave packets in the region upstream of the earth's bow shock are presented. Data from the dual magnetometers aboard the ISEE 1 and 2 spacecraft was used to determine the time delay between the appearance of a wavefront at each spacecraft in order to obtain the wave velocity in the spacecraft frame, and from it the intrinsic wave phase velocity. Results from the 11 events characterized by sufficiently large velocities reveal the wave packets to exhibit a nearly perfectly circular polarization with the packet field rotating in the left-hand sense about the ambient field direction in the spacecraft frame. In the plasma rest frame, these waves are found to be right-handed polarized waves with frequencies several times the proton gyrofrequency which are attempting to propagate upstream against the solar wind but are in fact being carried towards the earth by the solar wind flow.

Hoppe, M.↗
NASA NTRS1980

Type 2 solar radio events observed in the interplanetary medium. Part 1: General characteristics

Twelve type 2 solar radio events were observed in the 2 MHz to 30 kHz frequency range by the radio astronomy experiment on the ISEE-3 satellite over the period from September 1978 to December 1979. These data provide the most comprehensive sample of type 2 radio bursts observed at kilometer wavelengths. Dynamic spectra of a number of events are presented. Where possible, the 12 events were associated with an initiating flare, ground based radio data, the passage of a shock at the spacecraft, and the sudden commencement of a geomagnetic storm. The general characteristics of kilometric type 2 bursts are discussed.

Cane, H. V.↗
NASA NTRS1981

Evidence for magnetic field reconnection at the Earth's magnetopause

Eleven passes of the ISEE satellites through the frontside terrestrial magnetopause were identified, where the plasma velocity in the magnetopause and boundary layer was substantially larger than in the magnetosheath. The nature of the plasma flow, magnetic field, and energetic particle fluxes in these regions were examined, with a view to determining whether the velocity enhancements can be explained by magnetic field reconnection.

Sonnerup, B. U. O.↗
NASA NTRS1980

Structure of the low latitude boundary layer

Observations at high temporal resolution of the frontside magnetopause and plasma boundary layer, made with the LASL/MPE fast plasma analyzer onboard the ISEE 1 and 2 spacecraft, revealed a complex quasiperiodic structure of some of the observed boundary layers. A cool tailward streaming boundary layer plasma was seen intermittently, with intervening periods of hot tenuous plasma which has properties similar to the magnetospheric population. While individual encounters with the boundary layer plasma last only a few minutes, the total observation time may extend over one hour or more.

Sckopke, N.↗
NASA NTRS1981

Observations of interplanetary energetic charged particles from gamma-ray line solar flares

Observations of interplanetary energetic ions from the 7 June, 21 June and 1 July 1980 gamma ray line solar flares are presented. The observations are from the Max-Planck-Institut/University of Maryland Ultra Low Energy Wide Angle Telescope aboard the ISEE-3 spacecraft. Both June flares produced relatively low intensity proton events at earth with peak intensities at 10-20 MeV approximately 5 x .01 protons square cm sec sr MeV)-1. Neither flare showed evidence of being enriched in either 3He or Fe at approximately 1 MeV/nucleon. The 1 July flare produced no observable ion or electron enhancements.

Pesses, M. E.↗
NASA NTRS1981

Research in Space Physics at the University of Iowa

Currently active projects conducted to extend knowledge of the energetic particles and the electric, magnetic, and electromagnetic fields associated with Earth, other celestial bodies, and the interplanetary medium are summarized. These include investigations and/or instruments for Hawkeye 1; Pioneers 10 and 11; Voyagers 1 and 2; ISEE; IMP 8; Dynamics Explorer; Galileo; Spacelab and Orbital flight test missions; VLBI; and the International Solar Polar mission. Experiments and instruments proposed for the future international comet mission, the origin of plasmas in the Earth's environment mission, and the NASA active magnetospheric particle tracer experiment are mentioned.

Vanallen, J. A.↗
NASA NTRS1980

Energetic particles in space

A review is presented of observations of suprathermal particles in the interplanetary medium along with new data on low energy particles from experiments aboard the ISEE spacecraft. Energy spectra of protons in the near earth atmosphere are plotted in the rest frame of the solar wind noting that at energies above 10 to the 9th eV, the galactic cosmic ray electron component has an unattenuated access into the heliosphere. Solar transient events such as flares accelerate and release energetic particles into the interplanetary medium; flare particle fluxes generate shock waves propagating past 1 AU following the event. It is concluded that the energy spectra for shock wave accelerations show a characteristic shape in accordance with the power law with a rapid steepening at high energies.

Lin, R. P.↗
NASA NTRS1980

Gamma-ray burst source locations

Instrumentation for observing cosmic gamma-ray bursts has been provided for widely separated spacecraft, including the Pioneer Venus Orbiter, ISEE-3, Helios-B, Venera 10 and 11, and Prognoz 7. Simultaneous observations have been made of several gamma bursts with various combinations of these spacecraft and near-earth satellites. Locations of the gamma-burst sources have been calculated for those events where precise timing and ephemeris data are available. The results of optical and HEAO-B observations of the resultant error boxes will be discussed.

Evans, W. D.↗
NASA NTRS1980

A measurement of the isotopic composition of galactic cosmic ray carbon, nitrogen and oxygen

The paper reports the results of an investigation of the isotopic composition of galactic cosmic ray carbon, nitrogen and oxygen (80-230 MeV/amu) made using the U.C. Berkeley HKH instrument aboard the ISEE-3 spacecraft. The combination of high mass resolution and a large statistical sample makes possible a precise determination of the relative isotopic abundances for these elements. In local interplanetary space the following values are found: C-13/C = 0.067 + or - 0.008, N-15/N = 0.54 + or - 0.03, O-17/O less than 0.027, and O-18/O - 0.019 + or - 0.003.

Wiedenbeck, M. E.↗
NASA NTRS1980

The energy spectrum of cosmic ray electrons, 5-150 MeV in late 1978 and early 1979

The University of Chicago cosmic ray electron detector was launched aboard the ISEE-3 spacecraft on August 12, 1978. The energy spectrum of electrons measured in 1978 is nearly identical to that measured in 1968 by OGO-5. During the period of our investigation we observe quiet time increases in the electron flux which are of Jovian origin. These increases are restricted to energies below about 25 MeV but appear to have an energy dependence that peaks around 15 MeV.

Evenson, P.↗