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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Composition of ions and neutral gases during a magnetic storm

Study of the variation in composition of ions and neutral gases on the basis of numerical solutions of a coupled differential equation system describing the fundamental properties of the ionosphere and atmosphere within the range of the thermosphere. It is shown that changes in ion composition observed during a magnetic storm can be represented by changes in neutral gas composition in the lower thermosphere. A reduction of the O/N2 ratio in the lower thermosphere starts a sequence of events that leads to an increase in neutral gas temperature, decrease in O(+) and increase in NO(+) concentration.

Chandra, S.↗
NASA NTRS1972

Changes in the distribution of low-energy trapped protons associated with the April 17, 1965, magnetic storm.

The absolute intensity of geomagnetically trapped protons in the energy ranges from 0.52 to 4.0 MeV and from 0.90 to 1.8 MeV has been measured with the solid-state proton detector on the satellite Injun 4 for the period from Mar. 1 to May 31, 1965. A study of the temporal variations of these fluxes associated with the Apr. 17, 1965, magnetic storm shows a general redistribution of these protons for L greater than 2.5. The effect of the sudden commencement was a general depression in the intensities and a hardening of the energy spectra, although the intensities recovered to their prestorm level during the initial phase. The major redistribution was apparently initiated by the polar substorm. During the recovery phase, a secondary peak developed in the intensity profile at L of about 3.5 for 0.52-MeV protons that had no counterpart at this energy at the equator. No such peak was observed for 0.9-MeV protons.

Burns, A. L.↗
NASA NTRS1972

Ogo 5 observations of LHR noise, emissions, and whistlers near the plasmapause at several earth radii during a large magnetic storm.

On May 15, 1969, Ogo 5 crossed the plasmapause during a major storm that produced severe geomagnetic disturbances (Kp up to 8-), large and rapid variations in ring-current intensity (as measured by Dst), intense low-latitude aurora, and persistent SAR arcs. Near the highly structured plasmasphere boundary, the electric- and magnetic-field sensors on Ogo 5 detected lower-hybrid-resonance noise bursts, whistlers, ELF hiss, and other discrete signals or emissions. Some LHR noise bursts were associated with whistlers, and these high-altitude phenomena resembled the corresponding ionospheric ones. This report contains a description of the VLF observations. We also show that intense ULF magnetic signals were present near the plasmapause, and we attempt to relate these observations to the predictions of various theories of proton ring-current decay and SAR-arc formation.

Scarf, F. L.↗
NASA NTRS1972

Synthesis of Jicamarca data during the great storm of March 8, 1970.

Continuous measurement of electron temperature and electron concentration during the great magnetic storm of Mar. 8, 1970, when the F2 peak rose as high as 800 km. Continuous measurements of the vertical component of E x B drift were made from 1130 to 1730 LT. A synthesis of the observed electron concentrations was made using a model that solved the time-dependent electron-ion continuity equation for O(+) and the molecular ions; the latter chemistry was included to improve the solutions at lower heights. It was found, using the observed values of vertical drift, that most of the observed features of the F2-region ionosphere were synthesized by the model. An interpretation of the synthesis that emphasizes the importance of horizontal diffusion at the equator is given. Observations are presented for Mar. 7, 8, and 9, 1970, including the Huancayo magnetograms, which display a close correlation with the drift measurements.

Woodman, R. F.↗
NASA NTRS1972

Investigation of interaction between Pc 1 and 2 and Pc 5 micropulsations at the synchronous orbit during magnetic storms.

Coincident Pc 5 and Pc 1 and 2 micropulsations were observed at the synchronous equatorial satellite ATS 1 during the main phase of 11 geomagnetic storms that occurred in 1967. The Pc 1 and 2 oscillations were quasi sinusoidal, with periods of 5-20 sec and amplitudes of 1-2 gammas. Their average polarization was transverse to the ambient magnetic field. The oscillations were elliptical and rotation was to the left in relation to the main field. The observed characteristics suggest that the Pc 1 and 2 activity was due to ion cyclotron resonance of Alfven waves with energetic protons.

Barfield, J. N.↗
NASA NTRS1972

Preconditions for the triggering of polar magnetic substorms by storm sudden commencements.

A study of 36 storm sudden commencements (ssc) for the period June 1965 to January 1967 indicates that, for the cases considered, sufficient conditions for the triggering of simultaneous polar magnetic substorm onsets were an ssc amplitude of more than 10 gamma and an average geocentric solar magnetospheric Z component of interplanetary magnetic field of less than -1 gamma over a period of at least 1/2 hour preceding the ssc. All events satisfying these conditions produced simultaneous negative-bay onsets.

Burch, J. L.↗
NASA NTRS1973

High latitude proton precipitation and light-ion density profiles during the magnetic storm initial phase

Measurements of precipitating protons and light ion densities by experiments on OGO-4 indicate that widespread proton precipitation occurs in predawn hours during the magnetic storm initial phase from the latitude of the high-latitude ion trough, or plasmapause , up to Lambda 75 deg. A softening of the proton spectrum is apparent as the plasmapause is approached. The separation of the low-latitude precipitation boundaries for 7.3 kev and 23.8 kev protons is approximately 1 deg, compared with a 3.6 deg separation which has been computed using the formulas of Gendrin and Eather and Carovillano. Consideration of probable proton drift morphology leads to the conclusion that protons ase injected in predawn hours, with widespread precipitation occurring in the region outside the plasmapause. Protons less energetic than approximately 7 kev drift eastward, while the more energetic protons drift westward, producing the observed dawn-dusk asymmetry for the lower-energy protons.

Burch, J. L.↗
NASA NTRS1972

Isis 1 observations of the high-latitude ionosphere during a geomagnetic storm.

The Isis 1 satellite has made measurements of several ionospheric and related parameters, and the results of the various measurements have been compared in detail for two north transpolar passes during the geomagnetic storm of February 3, 1969. Simultaneous measurements were made of local electron and ion densities and temperatures, electron density between the satellite and the peak of the F layer, radio noise, and particle fluxes over a wide energy range extending down to 10 eV. Several features of the ionosphere (in particular, enhancements of radio noise, scale height, and plasma temperatures) appear to be due to soft-particle (100 eV to 1 keV) precipitation, which is related to magnetospheric structure as delineated by the observation of more energetic particles. The magnetosheath particles precipitating on the dayside of the polar cap are particularly effective.

Whitteker, J. H.↗
NASA NTRS1973

The Pioneer 9 electric field experiment. III - Radial gradients and storm observations.

We present a detailed analysis of the Pioneer 9 VLF electric field observations for 20 selected storm periods covering a heliocentric range extending from 0.754 AU to 0.99 AU. Although data from only two low frequency channels are available, the results of the present study tend to confirm the preliminary speculation by Scarf and Siscoe (1971) that the turbulent E-field spectrum in the disturbed solar wind has a significant radial gradient.

Scarf, F. L.↗
NASA NTRS1973

Magnetic storm inflation in the evening sector.

Analysis of the different behavior of a double magnetic disturbance in November 1971, as observed by Explorer 45, and in December 1971, as shown by ground level magnetic observations. The time sequence of magnetic storm inflation in the evening quadrant of the magnetosphere, as determined by both series of observations, is used as the criterion of the analysis. Particular attention is given to the various phases of proton penetration into the evening quadrant of the magnetosphere during the magnetic disturbance.

Cahill, L. J., Jr.↗
NASA NTRS1973

Energy spectra and pitch angle distributions of storm-time and substorm injected protons.

Discussion of the energy spectra and pitch angle distributions of ring current protons observed with the solid-state proton detector of Explorer 45 during the main and fast recovery phases of a storm on Dec. 17, 1971. Appearances of characteristic changes in the pitch angle distributions of roughly 100-eV protons are interpreted as pitch angle dispersion of rapidly injected protons during their azimuthal drift at L values above 5.

Konradi, A.↗
NASA NTRS1973

High-latitude proton precipitation and light ion density profiles during the magnetic storm initial phase.

Measurements of precipitating protons and light ion densities by experiments on Ogo 4 indicate that widespread proton precipitation occurs in predawn hours during the magnetic storm initial phase from the latitude of the high-latitude ion trough, or plasmapause, up to latitudes greater than 75 deg. A softening of the proton spectrum is apparent as the plasmapause is approached. The separation of the low-latitude precipitation boundaries for 7.3-keV and 23.8-keV protons is less than about 1 deg, compared with a 3.6-deg separation that has been computed by using the formulas of Gendrin and Eather and Carovillano. Consideration of probable proton drift morphology leads to the conclusion that protons are injected in predawn hours, widespread precipitation occurring in the region outside the plasmapause. Protons less energetic than 7 keV drift eastward, whereas the more energetic protons drift westward, producing the observed dawn-dusk asymmetry for the lower-energy protons.

Burch, J. L.↗
NASA NTRS1974

On the source of flare-ejecta responsible for geomagnetic storms

It is shown that magnetic bottles as the sources of moving metric type 4 bursts are not responsible for the development of geomagnetic storms, despite the fact that shock waves producing type 2 bursts are the sources of the interplanetary shock waves, which produce SSC's on the geomagnetic field. These magnetic bottles, in general, tend to move in the solar envelope with the speed of several hundred Km/sec at most, which is much slower than that of the motion of type 2 radio sources.

Sakurai, K.↗
NASA NTRS1974

Thermal structure of the Martian atmosphere during the dissipation of the dust storm of 1971

The secular variation of the thermal structure of the Martian atmosphere during the dissipation phase of the 1971 dust storm is examined, using temperatures obtained by the infrared spectroscopy investigation on Mariner 9. For the latitude range -20 to -30, the mean temperature at the 2mb level is found to decrease from approximately 220K in mid-December 1971 to about 190K by June 1972 while for the 0.3mb level a decrease from 203K to 160K is observed. Over the same period, the amplitude of the diurnal temperature wave also decreased. Assuming a simplified radiative heating model, the dust optical depth is found to decrease approximately exponentially with an e-folding time of about 60 days at both the 0.3 and 2mb levels. Stokes-Cunningham settling alone cannot account for this behavior. Sedimentation models which include both gravitational settling and vertical mixing are developed in an effort to explain the time evolution of the dust.

Conrath, B. J.↗
NASA NTRS1974

Electron contamination in a mid-latitude soft X-ray astronomy experiment during an intense magnetic storm

A large area X-ray sky survey payload was launched from White Sands Missile Range (106 deg W 32 deg N) on 1 Nov. 1972 at 0530 hours U.T. The launch time coincided with intense geomagnetic activity (3 hour K sub p index = 8) following a solar flare. The data have been analyzed to determine possible contamination of X-ray data by large fluxes of low energy electrons that can precipitate down to low altitudes during magnetic storms. There is clear evidence in the data for low energy electrons of 10 - 50 keV contributing appreciably at about 200 km altitude in the 1 - 10 keV X-ray energy channels of the proportional counters used for the X-ray observations. The McIlwain parameters L and B for this altitude at White Sands are 1.25 and 0.46G, respectively.

Naranan, S.↗
NASA NTRS1974

The dynamical responses of the thermosphere due to a geomagnetic storm

A theoretical model for the dynamic responses to geomagnetic storms in the thermosphere is derived from magnetohydrodynamic theory. The validity claim for this model is based on the assumption that the thermosphere behaves like an electrically conductive fluid. In order to test the proposed model, a numerical example is presented. Recommendations for improving the model are also offered.

Wu, S. T.↗
NASA NTRS1974

Observations of neutral winds in the auroral E region during the magnetospheric storm of August 3-9, 1972

Auroral zone E-region neutral winds have been derived from simultaneous measurements of ion drift velocities in different altitudes by the incoherent radar facility at Chatanika, Alaska, on a quiet day before and during the great magnetospheric storm of Aug. 3-9, 1972. The neutral wind expected for a day-night pressure asymmetry appears to be strongly opposed by ion drag and local pressure gradients in the auroral oval.

Brekke, A.↗