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Nakada, M. P.

Publications and source records attributed to Nakada, M. P..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Auroral pulsations from ionospheric winds

The possibility that auroral pulsations are due to oscillatory electrical circuits in the ionosphere that are driven by the negative resistance of jet stream winds is examined. For the condenser plates, the highly conducting surfaces above the edges of the jet stream are postulated. The dielectric constant of the plasma between the plates is quite large. The current that is driven perpendicular to and by the jet stream closes along the plates and through Pedersen currents in the F region above the stream. This closed loop gives the inductance and resistance for the circuit. Periods of oscillation for this circuit appear to be in the range of Pc 1 to Pc 3. In accord with observations, this circuit appears to be able to limit the brightness of pulsations.

Nakada, M. P.↗
NASA NTRS1987

Parallel electric fields from ionospheric winds

The possible production of electric fields parallel to the magnetic field by dynamo winds in the E region is examined, using a jet stream wind model. Current return paths through the F region above the stream are examined as well as return paths through the conjugate ionosphere. The Wulf geometry with horizontal winds moving in opposite directions one above the other is also examined. Parallel electric fields are found to depend strongly on the width of current sheets at the edges of the jet stream. If these are narrow enough, appreciable parallel electric fields are produced.

Nakada, M. P.↗
NASA NTRS1980

Thermal diffusion calculations for the ionosphere of Venus

Simplified multicomponent diffusion calculations are made for the ionosphere of Venus. Large differences in temperature between electrons and ions and appreciable temperature gradients that are near those of recent measurements are used. Compositions for which binary thermal diffusion coefficients for ions are the same as multi-ion ones are examined as well as those that are quite different. An attempt to combine binary coefficients to give multi-ions ones has not been particularly successful.

Nakada, M. P.↗
NASA NTRS1979

On the foci of Tandem Wadsworth spectrographs

The horizontal foci of a Tandem Wadsworth spectrograph are calculated by using the correct ruling densities for both gratings. Results are quite different from those of previous analyses that used approximate ruling densities. Ray tracings confirm the analyses with the correct ruling densities and also indicate that this spectrograph possesses the excellent, nearly stigmatic properties found by the approximate analyses.

Nakada, M. P.↗
NASA NTRS1977

On coronal Fe abundances and temperatures from XUV emission lines

Data obtained by the OSO-7 spectroheliograph on strong XUV lines of five different Fe ions from the outer equatorial corona are presented. Interpretation of the data with a spherically symmetric model atmosphere gives average ion abundances for lines of sight at 0.3 solar radii from the limb. Fe XVI is usually more abundant than Fe XV, XIV, XII and IX, but there are times when Fe XII is more abundant than the other ions. The deviation of measured relative abundances of Fe XII, XIV, and XVI from predictions of ionization equilibrium at one temperature seems to indicate that there are appreciable temperature variations along lines of sight. Element abundances are very uncertain since they appear to depend so heavily on likely but unknown density irregularities along lines of sight.

Nakada, M. P.↗
NASA NTRS1977

On coronal temperatures, temperature gradients and compositions

Average solar wind properties at 1 AU either alone or together with the electron density distribution are used to obtain or review some results that relate coronal temperatures, temperature gradients, and compositions. Measured values of the temperature (T) and the temperature gradient parameter are used to find compositions that satisfy the equations used to obtain the results. The total energy equation may be satisfied if the thermal conductivity is reduced by considerable depletions of H(+) in the corona. The hydrostatic approximation (momentum equation) for the electron density distribution appears to require considerable depletions of H(+) in the corona.

Nakada, M. P.↗
NASA NTRS1976

Coronal temperatures and temperature gradients from OSO-7 spectroheliograms

Temperatures and temperature gradients for the outer corona are obtained from brightness gradients of EUV lines that were measured with the spectroheliograph on OSO-7. Brightness gradients show considerable deviations from isothermal model calculations that include collisional excitation and photoexcitation. A negative temperature gradient that gives both positive and negative ion-abundance gradients appears to be able to account for the discrepancy. For the 284-A of Fe XV, perhaps the strongest line from the outer corona, measurements during 1972 appear to be consistent with a temperature near 2.3 million K near the equator at about 1.3 solar radii from the solar center and with temperature-gradient values near -0.7 that extend from as low as 1.2 to about 1.8 solar radii. Temperatures from strong lines of Fe XIV and Fe XVI indicate that variations of about 200,000 K exist along lines of sight where emission is appreciable. There appears to be some agreement between these results and temperature measurements from ion abundances in the solar wind and the Doppler width of the 5303-A line.

Nakada, M. P.↗
NASA NTRS1975

OSO-7 results on coronal emission near 304 A

The spectral composition and spatial distribution of equatorial coronal emission near 304 A is examined. Spectral scans indicate that the predominant line is from Si XI. Comparisons of observations with calculations of intensity changes with altitude indicate that collisional excitation is important near the sun but that photoexcitation becomes dominant beyond about 1.3 solar radii from the solar center. Observed and calculated intensities are in approximate agreement for abundances and electron densities that are within the range of observed values.

Nakada, M. P.↗
NASA NTRS1975

Abundance of Fe relative to H at 1.5 solar radii

The abundance of Fe relative to H is obtained by using resonantly scattered intensities of lambda 284 of Fe XV that were measured with OSO-7 and resonantly scattered intensities of L-alpha of H I that were obtained by Gabriel (1971). Because of possible differences in electron densities along lines of sight for these non-simultaneous measurements and in relative calibrations, results are rather uncertain but still indicate that the average Fe abundance relative to H in the corona appears to be at least as large as a recent photospheric abundance. Some limitations in using this method for obtaining abundances are examined for future experiments with simultaneous measurements and well calibrated detectors.

Nakada, M. P.↗
NASA NTRS1974

Polarization results of solar X-rays from OSO-7

Polarization measurements of solar X-ray events that were obtained with an instrument on OSO-7 are presented. The results appear to be consistent with the results of Tindo et al. on the existence and magnitudes of polarization. A comparison with polarization predictions when X-rays are produced by radial beams of electrons gives two examples of deviations from such a model.

Nakada, M. P.↗
NASA NTRS1974

Some effects of diffusion on the flow of ions in the solar wind

The contribution of diffusive effects to the near equality of flow velocities of H+ and heavier ions of the solar wind at 1 AU is examined. Frictional drag on heavy ions from average solar wind fluxes of H+ appears to make an appreciable contribution to equalizing velocities. The frictional drag on H+ due to the presence of heavy ions may make an appreciable contribution to equalizing flow velocities, since compensating increases in coronal temperatures may be required in order to give solar wind velocities for H+. However, rather large enhancements of heavy ions near the sun appear to be required. If appreciable enhancements of heavy ions extend beyond about 2.5 solar radii, significant increases in heavy ion temperatures above H+ temperatures may be produced. This temperature difference may contribute to equalizing flow velocities and may contribute to the explanation of measured temperature differences at 1 AU between H+ and He++.

Nakada, M. P.↗
NASA NTRS1974

Effects of heavy ions on electron temperatures in the solar corona and solar wind

The effects of the reduction in the thermal conductivity due to heavy ions on electron temperatures in the solar corona and solar wind are examined. Large enhancements of heavy ions in the corona appear to be necessary to give appreciable changes in the thermal gradient of the electrons. These enhancements, if they should occur, may contribute to the understanding of some low values of solar wind temperature measurements at 1 AU.

Nakada, M. P.↗
NASA NTRS1973

Acceleration of heavy ions by radiation pressure.

The possible acceleration of heavy ions by the resonance scattering of radiation near bright stellar objects is examined. Planck spectra are assumed. At any radiation temperature, heavy-ion energies are found to be limited by aberration and Doppler effects. Photoionization is found to limit maximum radiation temperatures and energies for each ion. Collisional ionization by ambient electrons and ions may further limit heavy-ion energies. Because of these limitations, the production of the more energetic cosmic rays by this mechanism appears to be very improbable. If supernova radiation temperatures are high enough, they may produce heavy ions with energies up to several hundreds of MeV per nucleon. O and B stars appear to be able to accelerate certain heavy ions to 200 and 80 MeV per nucleon, respectively.

Nakada, M. P.↗
NASA NTRS1972

Heavy ions from interplanetary dust.

Most atoms that are evaporated from interplanetary dust near the sun are quickly ionized and are probably carried away by the interplanetary magnetic field and the solar wind. The contribution of these heavy ions to the solar-wind flux has been estimated by using estimates of the mass required to maintain the zodiacal cloud. This contribution appears to be small compared with the heavy-ion flux of coronal origin. Many ions from dust remain singly ionized; some of these, such as Ca(+), can resonantly scatter solar radiation. The contribution of this interplanetary glow to the background of twilight glow has been estimated. Interplanetary glow may be detectable. Some atoms from dust may be accelerated by radiation pressure before being ionized. Estimates of velocities and fluxes for Fe indicate that this acceleration is not very effective.

Nakada, M. P.↗