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Goertz, C. K.

Publications and source records attributed to Goertz, C. K..

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Plasma in the Jovian current sheet

A large body of spectral data for protons with energies greater than 200 keV has been analyzed. It is concluded that the main body of plasma in the Jovian current sheet observed by Pioneer 10 on its outbound pass probably has an energy well below the lowest threshold of the Pioneer 10 detectors. This premise is examined using a semiempirical model of the magnetic field in the magnetodisk and simple magnetohydrodynamic theory. Results indicate that the dominant contribution to the plasma pressure in the region from 25 to 65 Jovian radii is from as yet unobserved protons (ions) with energies of the order of 0.1 to 10 keV.

Goertz, C. K.↗
NASA NTRS1979

The dynamics of the Jovian magnetosphere

The current status of the understanding of the dynamics of Jupiter's magnetosphere is reviewed. A brief summary is presented of the concepts and processes which were identified as being of probable importance by pre-Pioneer 10 and 11 work (both theoretical and observational). The insights provided by the in situ Pioneer flights are then discussed. The Jovian magnetosphere consists of several relatively distinct regions: the inner magnetosphere, the intermediate magnetosphere, the outer magnetosphere, a transition region just inside the magnetopause, and the magnetosheath. The basic particle and magnetic field characteristics of these regions are summarized, and the dynamical processes which are currently thought to be significant in each of them are reviewed. Finally, some outstanding questions and problems are identified for future treatment based on Pioneer data or on data from the upcoming Voyager and Galileo missions.

Goertz, C. K.↗
NASA NTRS1979

Radial diffusion of Io-injected plasma

The paper reexamines the problem of particle injection by Io and subsequent radial diffusion by flux tube interchange using a proper phase space density formulation. The mathematical formalism is developed, and the theoretical results are compared with the observations, taking into account the pitch angle and energy coverage of the detector on Pioneer 10. Two objectives are pursued: (1) to test the hypothesis of Siscoe and Chen (1977) that Io is the source for all of the plasma observed by Frank et al. (1976) inside 10 R(J); and (2) to describe a simple but flexible method intended to analyze the observations of any other plasma instrument flown through the inner Jovian magnetosphere, e.g., those on Voyager 1 and 2 and Galileo.

Goertz, C. K.↗
NASA NTRS1979

The Jovian magnetodisk

Magnetic field measurements made by the vector helium magnetometers on board Pioneers-10 and 11 reveal the existence of a current sheet (thickness of about 2 Jupiter radii) carrying an eastward current. Self-consistent studies of the current sheet show that the magnitude of the current is of the order of 0.01/Am and that the current is carried by a hot (T greater than 1 keV) plasma, the density of which varies between 1 cu cm at 30 Jupiter radii to 100 cu cm at 80 Jupiter radii. The current sheet is warped azimuthally and parallel to the magnetic dipole equator. The existence of an azimuthal field component indicates a poloidal plasma flow transporting some 10 to the 29th ions per second from Jupiter into the outer magnetosphere. It is shown that, if the outer magnetosphere is in a steady state, this plasma must be transported outward within the current sheet by a diffusion process which is faster than the one responsible for particle transport in the inner magnetosphere but slower than Bohm diffusion.

Goertz, C. K.↗
NASA NTRS1979

Further observational support for the lossy radial diffusion model of the inner Jovian magnetosphere

A mathematical model describing radial diffusion, with violation of the third adiabatic invariant and with local losses, is applied to the Pioneer 10 and 11 observations of omnidirectional integral intensities of electrons with energy exceeding 21 MeV. Local losses outside L = 3 are much stronger than synchrotron losses but weaker than the losses one would expect for strong pitch angle diffusion. If radial diffusion is driven by ionospheric winds, as was suggested by Brice and McDonough (1973), it is found that the theoretical solution which best fits the data requires that the radial diffusion coefficient equals 3 x 10 to the -9th L-cubed/s and the lifetime against local losses is approximately a few million seconds.

Goertz, C. K.↗
NASA NTRS1978

Correction to 'Recirculation of energetic particles in Jupiter's magnetosphere'

An error in Pioneer 11 data reduction software has, when present, caused a phase shift of 180 deg in the assignment of spacecraft roll angles. The corrected analysis of the pitch angle distributions of energetic particles in Jupiter's magnetosphere reveals significant proton anisotropies directed toward the planet in the southern hemisphere, contrary to the authors' (1975) original report. In the northern hemisphere, both proton and electron anisotropies are directed away from the planet, as reported previously. The revised data show that the claim of direct evidence for the hypothesis of recirculation of energetic particles in the Jovian magnetosphere is invalid. It is suggested that indirect evidence still supports the hypothesis, although the recirculation process must be weaker than originally envisioned and obscured by other processes.

Sentman, D. D.↗
NASA NTRS1978

Whistler mode noise in Jupiter's inner magnetosphere

A study is made of the amplitude and spectral extent of whistler mode noise in the inner magnetosphere of Jupiter. It is found that the 'hat-shaped' pitch angle distributions of energetic electrons (21 and 31 MeV at L=3) are consistent with those predicted in the presence of a band-limited spectrum of whistler mode noise. The equatorial maximum linear growth rate of parallel propagating whistlers are consistent with those necessary to limit the energetic electron intensities by the whistler mode instability. It is noted that the wave phase speeds before wave reflection can occur at high latitudes and that wave growth is limited to a disk-like region centered around the magnetic equator. The frequency extent of the whistler mode noise spectrum may be estimated by the range of frequencies maximally unstable to equatorial linear growth. A value is found for the spectral density of the broadband whistler mode noise necessary to balance radial diffusion of energetic electrons above the critical range, and an expression is derived for the energetic electron system response to fluctuations about the limiting flux value.

Sentman, D. D.↗
NASA NTRS1978

On the modulation of the Jovian decametric radiation by Io. I - Acceleration of charged particles

A steady-state analysis of the current circuit between Io and the Jovian ionosphere is performed, assuming that the current is carried by electrons accelerated through potential double layers in the Io flux tube. The circuit analysis indicates that electrons may be accelerated up to energies of several hundred keV. Several problems associated with the formation of double layers are also discussed. The parallel potential drops decouple the flux tube from the satellite's orbital motion.

Smith, R. A.↗
NASA NTRS1978

Energetic protons associated with interplanetary active regions 1-5 AU from the sun

Pioneer 11 has yielded data on approximately 100 energetic proton events at heliocentric distances between 1 and 2 AU. Measurements of absolute intensities, anisotropies, and crude energy spectra are studied in connection with interplanetary active regions (IAR's). It is found that in close vicinity to IAR's, the number of events observed per unit time interval is 10 times greater than in other areas of interplanetary space, and that the frequency of events has a maximum at plus or minus 5 hours of the time IAR edges are crossed. It is also noted that events in IAR vicinity have greater particle densities, softer energy spectra, and smaller time widths than other events. For many events associated with IAR's, particle anisotropies correspond to the net flow of particles along the interplanetary magnetic field toward the sun. This suggests that a mechanism in MHD shocks is responsible for local acceleration in the interplanetary medium.

Pesses, M. E.↗
NASA NTRS1977

On determining magnetospheric diffusion coefficients from the observed effects of Jupiter's satellite Io

A method is derived for determining the radial diffusion coefficient from observed satellite effects of the inner Jovian satellites on the energetic particle fluxes. The method is based on data from L values which are significantly removed from the actual sweeping region. With regard to the large losses to the protons at Io's L shell, it is suggested that in addition to satellite sweepup, the losses may be associated with an enhanced precipitation due to resonant interaction with ion cyclotron waves near Io's orbit. It is noted that such additional loss mechanisms may also apply to electrons, and that such losses may significantly affect the estimated diffusion coefficient.

Thomsen, M. F.↗
NASA NTRS1977

A determination of the L dependence of the radial diffusion coefficient for protons in Jupiter's inner magnetosphere

In a previous paper (Thomsen et al., 1977), a technique was proposed for estimating the radial diffusion coefficient (n) in the inner magnetosphere of Jupiter from the observations of the sweeping effect of the inner Jovian satellites on the fluxes of the energetic charged particles. The present paper extends this technique to permit the unique identification of the parameters D sub O and n, where the diffusion coefficient is assumed to be of the form D = D sub O L to the nth. The derived value of D sub O depends directly on assumptions regarding the nature and efficiency of the loss mechanism operating on the particles, while the value of n depends only on the assumed width of the loss region. The extended technique is applied to the University of Iowa Pioneer 11 proton data, leading to values of n of about O and D(6) of about 3 x 10 to the -8th (R sub J)-squared/sec, when satellite sweepup losses are assumed to be the only loss operating on the protons. The small value of n is strong evidence that the radial diffusion is driven by ionospheric winds.

Thomsen, M. F.↗
NASA NTRS1976

Radial diffusion in Jupiter's magnetosphere

Radial phase-space density profiles for equatorially mirroring particles are computed from data obtained by Pioneer 10. The profiles are consistent only with radial diffusion subject to nonadiabatic losses. It is suggested that these losses are due to pitch-angle scattering by whistler turbulence.

Baker, D. N.↗
NASA NTRS1976

The current sheet in Jupiter's magnetosphere

A theoretical model is presented for the plasma in the Jovian magnetosphere whose pressure is comparable to the corotational energy density. The model is consistent with a thin current sheet of half thickness equal to 1 or 2 Jupiter radii. The current sheet lies almost precisely in the magnetic equatorial plane and is not appreciably warped, as has been suggested previously. Warping would occur only if the plasma pressure were much less than the corotational energy density

Goertz, C. K.↗
NASA NTRS1976

Evidence for open field lines in Jupiter's magnetosphere

A model for the night-side Jovian magnetic field is derived partly on the basis of theoretical considerations and partly on the basis of the magnetic-field data obtained during the outbound leg of the path of Pioneer 10. This model can explain the observed sawtooth modulation of energetic particle fluxes in terms of closed and open field lines that cannot contain the particles. The model is applicable only to the Jovian magnetotail.

Goertz, C. K.↗
NASA NTRS1976

Plasma in the Jovian magnetosphere

The plasma in Jupiter's ionosphere is collisionless above a certain level. In the outer magnetosphere, where the rotational force dominates the gravitational force, the collisionless plasma has a beamlike distribution and gives rise to a two-stream instability. This leads to trapping of plasma in the centrifugally dominated region of the magnetosphere. Plasma is lost through recombination. The equilibrium concentration of trapped particles is calculated by assuming a balance between trapping by wave-particle interaction and loss by recombination. The results are compared with recent observations from Pioneer 10. The observations appear to require an unexplained ion-heating mechanism.

Goertz, C. K.↗
NASA NTRS1976

Jupiter's magnetotail as the source of interplanetary Jovian MeV electrons observed at earth

The source of interplanetary Jovian MeV electron enhancements observed at earth is found to be Jupiter's magnetotail. If an average solar wind speed of 400 km/sec is assumed, the main region of emission extends from about 1.0 AU downstream from Jupiter to about 2.0 AU beyond the planet. (If a value of 350 km/sec is assumed, it extends from about 0.4 AU to about 1.2 AU.) Individual 'active' zones are about 0.2 AU in length. It is proposed that interplanetary magnetic field line connection with the tail is the mechanism providing the Jovian electrons observed at earth.

Pesses, M. E.↗
NASA NTRS1975

The current sheet in Jupiter's magnetosphere

A theoretical model is presented for the plasma in the Jovian magnetosphere whose pressure is comparable to the corotational energy density. The model predicts a thin current sheet of 1 Jupiter radius to 2 Jupiter radii half-thickness. The current sheet lies almost precisely in the magnetic equatorial plane and is not appreciably warped as suggested previously.

Goertz, C. K.↗