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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
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

Quiet-time magnetospheric field depression at 2.3 to 3.6 R sub E

Fluxgate magnetometer data obtained by OGO-5 near perigee were used to establish the existence of large field depressions in the magnetosphere under conditions of varying degree of disturbance at distances ranging from 2.3 to 3.6 R sub E at all local times. The results also provide the average delta B at these distances when Dst, as being derived at present, is zero.

Sugiura, M.↗
NASA NTRS1973

Geophysical disturbance environment during the NASA/MPE barium release at 5 earth radii on September 21, 1971.

The geophysical disturbance environment was quiet during the NASA/MPE barium release at 5 earth radii on September 21, 1971. At the time of the release, the magnetosphere was in the late recovery phase of a principal magnetic storm, the provisional Dst value was -13 gammas, and the local horizontal disturbance at Great Whale River was near zero. Riometer and other observations indicated low-level widespread precipitation of high-energy electrons at Great Whale River before, during, and after the release. Cloudy sky at this station prevented optical observation of aurora. No magnetic or ionospheric effects attributable to the barium release were detected at Great Whale River.

Davis, T. N.↗
NASA NTRS1974

Study of low frequency hydromagnetic waves using ATS-1 data

An analysis was made of ATS-1 data to determine at what point in the magnetic storm recovery phase are oscillations most likely to begin. The catalog of hourly values of equatorial Dst was used to determine the time of main phase decrease, and a catalog of oscillations from January to May 1968 to determine onset time as observed by ATS-1. For each oscillation event at ATS-1, the nearest prior main phase decrease with a magnitude of at least -35 gamma was determined, and the time difference between the onset of the event at ATS-1 and the time of main phase decrease was measured. The resulting data indicate that the most probable time to observe onset of transverse oscillations is within 24 hours after the main phase decrease.

Cummings, W. D.↗
NASA NTRS1974

Isolated cold plasma regions: Observations and their relation to possible production mechanisms

Regions of enhanced cold plasma, isolated from the main plasmasphere along the Explorer 45 orbit on the equatorial plane, are reported using the sheath induced potentials seen by the electric field experiment. The occurrence of these regions has a strong correlation with negative enhancements of Dst, and their locations are primarily in the noon-dusk quadrant. The data support the concept that changes in large scale convection play a dominant role in the formation of these regions. Plasmatails that are predicted from enhancements of large scale convection electric fields in general define where these regions may be found. More localized processes are necessary to account for the exact configuration and structure seen in these regions and may eventually result in detachment from the main plasmasphere.

Maynard, N. C.↗
NASA NTRS1973

Equatorward shift of the cleft during magnetospheric substorms as observed by Isis 1

Isis 1 satellite observations of the cleft position during magnetospheric substorms show that the cleft shifts equatorward as the interplanetary B sub z component turns southward and substorm activity increases and that it shifts back toward higher latitudes as substorm activity subsides and B sub z returns northward. Also, unusually low latitudes for the cleft (less than 70 deg invariant latitude) were found during geomagnetic storms with significant Dst values and large negative B sub z values. Significant shifts occur in the cleft location with no accompanying effect seen in the AE index; however, B sub z is observed to be southward during these periods.

Yasuhara, F.↗
NASA NTRS1974

On correlation analysis of the Explorer 12 substorm protons with some geophysical parameters

The intensity of Explorer-12 substorm protons with energies above 140 keV observed in the far outer belt are compared with several commonly used geomagnetic indices. The parameters considered in the correlation include Davis and Sugiura's (1966) AE index that provides a measure of the magnitude of substorm intensity, the asymmetric ring-current index R(DS) that is obtained from nine low-latitude stations, Sugiura and Hendricks' (1967) Dst index representing the symmetric component of the ring current, and the planetary magnetic index Kp.

Su, S.-Y.↗
NASA NTRS1975

A study of geomagnetic storms

Twenty-one geomagnetic storm events during 1966 and 1970 were studied by using simultaneous interplanetary magnetic field and plasma parameters. Explorer 33 and 35 field and plasma data were analyzed on large-scale (hourly) and small-scale (3 min.) during the time interval coincident with initial phase of the geomagnetic storms. The solar-ecliptic Bz component turns southward at the end of the initial phase, thus triggering the main phase decrease in Dst geomagnetic field. When the Bz is already negative, its value becomes further negative. The By component also shows large fluctuations along with Bz. When there are no clear changes in the Bz component, the By shows abrupt changes at the main phase onet. On the small-scale behavior of the magnetic field and electric field (E=-VxB) studied in details for the three events, it is found that the field fluctuations in By, Bz and Ey and Ez are present in the initial phase. These fluctuations become larger just before the main phase of the storm begins. In the largescale behavior field remains quiet because the small scale variations are averaged out.

Patel, V. L.↗
NASA NTRS1975

Interplanetary field and plasma during initial phase of geomagnetic storms

Twenty-three geomagnetic storm events during 1966 to 1970 were studied by using simultaneous interplanetary magnetic field and plasma parameters. Explorer 33 and 35 field and plasma data were analyzed on large-scale (hourly) and small-scale (3 min.) during the time interval coincident with the initial phase of the geomagnetic storms. The solar-ecliptic Bz component turns southward at the end of the initial phase, thus triggering the main phase decrease in Dst geomagnetic field. The By component also shows large fluctuations along with Bz. When there are no clear changes in the Bz component, the By shows abrupt changes at the main phase onset. On the small-scale, behavior of the magnetic field and electric field were studied in detail for the three events; it is found that the field fluctuations in By, Bz and Ey and Ez are present in the initial phase. In the large-scale, the behavior field remains quiet because the small-scale variations are averaged out. It appears that large as well as small time scale fluctuations in the interplanetary field and plasma help to alter the internal electromagnetic state of the magnetosphere so that a ring current could causing a geomagnetic storm decrease.

Patel, V. L.↗
NASA NTRS1974

Magnetic storm dynamics of the thermosphere

A theoretical study of the Dst component of magnetic storms is presented. The dynamic characteristics are found significantly different for Joule dissipation and electron precipitation, leading to the conclusion that the former is probably the predominant heat source for the upper thermosphere. Composition measurements on OGO-6, which reveal markedly different characteristics in N2, O and He, can be explained on the basis of energy advection and diffusive mass transport by thermospheric winds. Essential features in the F2-region response are explicable in terms of these dynamic processes. Electric field induced motions are estimated and it is concluded that resultant adiabatic heating could be significant.

Mayr, H. G.↗
NASA NTRS1974

Time response simulation of the 1975 Viking Orbiter digital tape recorder

The objective of the present study was to verify and understand in depth the performance of the speed control (frequency loop) servo of the 1975 Viking Orbiter (VO75) digital tape recorder (DTR). The time response method employed is written in the continuous system simulation language (CSSL) for the Univac 1108 computer system. In order to demonstrate the power and flexibility of the graphic interactive simulation program, four aspects of system dynamics are interactively adjusted to arrive at a number of stable system configurations that have significantly different tape transport and/or summing amplifier gain, larger static/dynamic Coulomb friction, and different system lag than envisioned in the nominal design by linear methods. Work is currently underway to derive a new higher-order DST transfer function and to simulate the servo using state-space variable techniques.

Mukhopadhyay, A. K.↗
NASA NTRS1974

Analysis of data from spacecraft relating to stratospheric warmings

A detailed study of six different stratospheric warmings is described which establishes that the magnetic indices AE, Ap, and Dst display a marked increase 1 to 3 days before warming phenomena and a marked decrease at 0 and -4 days. The definite correlation of the warming phenomena with the AE index indicates that the auroral electrojet joule heating near 100 km may be the original source of the heating that influences the atmosphere at 50 km and below. Whether this heating is the primary cause or trigger of stratospheric warmings remains to be determined.

Weiss, R.↗
NASA NTRS1975

Quiet time inflation of the inner magnetosphere in the afternoon and evening quadrants

The quiet-time depression of the magnetic field magnitude in the equatorial inner magnetosphere was studied for the interval Nov. 1971-June 1972. For periods when Kp was less than 2 and Dst was between +10 and -20 gamma, an inflated field region near the magnetic equator was found between noon and midnight. The inflation was greatest at the lowest altitude studied (L = 3) and appeared to be somewhat greater near midnight (-40 gamma) than near noon (-20 gamma). Protons of energy above 100 keV observed on the same satellite appeared to be sufficient to produce the quiet-time inflation.

Lee, Y. C.↗
NASA NTRS1975

Isolated cold plasma regions - Observations and their relation to possible production mechanisms

Regions of enhanced cold plasma, isolated from the main plasmasphere along the Explorer 45 (53-A) orbit in the equatorial plane, have been detected by using the sheath-induced potentials seen by the electric field experiment. The occurrence of these regions has a strong correlation with negative enhancements of Dst, and their locations are primarily in the noon-dusk quadrant. The data support the concept that changes in large-scale convection play a dominant role in the formation of these regions. Plasma tails that are predicted from enhancements of large-scale convection electric fields in general define where these regions may be found. More localized processes are necessary to account for the exact configuration and structure seen in these regions and may eventually result in detachment from the main plasmasphere.

Maynard, N. C.↗
NASA NTRS1976

ELF hiss associated with plasma density enhancements in the outer magnetosphere

The low-frequency narrow hiss bands associated with plasma-density enhancements in the magnetosphere near and beyond L = 4 have been studied with the search coil magnetometer and ion mass spectrometer data from OGO 5. ELF hiss is found to accompany most of the detached plasmas in the outer magnetosphere and to be sharply limited by the steep ion-density gradient at their boundary. The observations indicate that the hiss originates in and is ducted by the plasma-density enhancements. In a particularly favorable case after an interval of low AE and Dst indices, a series of enhanced plasma-density peaks was observed between L = 4 and L = 6 in the afternoon local-time sector. In this case, it was possible to develop an empirical relation among hiss amplitude, plasma density, and L by using in situ simultaneous measurements.

Chan, K.-W.↗
NASA NTRS1977

The impact of satellite soundings upon the NMC analysis and forecast system

The importance of satellite-derived soundings on National Meteorological Center weather analysis and forecast was studied by comparing summertime DST (Aug. 18-Sept. 4, 1975) forecasts generated by analyses with and without both the operational VTPR soundings from NOAA-4 and the experimental soundings derived from the infrared and microwave instruments aboard Nimbus-6. Objective and subjective procedures, including evaluation of standard skill scores and judgment by skilled synopticians, was used to evaluate the importance of satellite data. The investigation shows that satellite data do not aid numerical weather prediction in the Northern Hemisphere.

Tracton, M. S.↗
NASA NTRS1977

A statistical method for time-continuous assimilation of remote sounding temperatures

A time-continuous statistical method is presented for the four-dimensional assimilation of remote sounding temperatures based on radiometric measurements from polar-orbiting satellites. This method is applied to DST-6 data from the NOAA-4 and Nimbus-6 satellites. Experiments are reported in which the state of the atmosphere throughout the test period was determined using a varying amount of satellite data and in which different methods were used for their assimilation. Data from the NOAA-4 satellite only, from Nimbus-6 only, and from both satellites together were used; the methods tested include different variations of the statistical method as well as more traditional methods. The conclusions are that: (1) satellite-derived temperature data can have a modest, but statistically significant positive impact on numerical weather prediction in the two-to-three day range; (2) this impact is highly sensitive to the quantity of data available; and (3) the assimilation method plays a major role in the magnitude of the impact for the same data.

Ghil, M.↗
NASA NTRS1979

Nighttime ionization by energetic particles at Wallops Island in the altitude region 120 to 200 km

Five Nike Apache rockets, each including an energetic particle spectrometer and an electron density-electron temperature experiment, have been launched from Wallops Island (L = 2.6) near midnight under varying geomagnetic conditions. On the most recent of these (5 January 1978) an additional spectrometer with a broom magnet, and a 391.4 nm photometer were flown. The data from this flight indicate that the energetic particle flux consists predominantly of protons, neutral hydrogen and possibly other energetic nuclei. The energy spectrum becomes much softer and the flux more intense with increasing Kp for 10-100 keV. The pitch angle distribution at 180 km is asymmetrical with a peak at 90 deg indicating that the majority of particles are near their mirroring altitude. Ionization rates are calculated based on the measured energy spectrum and mirror height distribution. The resulting ionization rate profile is found to be nearly constant with altitude in the region 120 to 200 km. The measured energetic particle flux and calculated ionization rate from the five flights are found to vary with magnetic activity (based on the Kp and Dst indexes) in the same way as the independently derived ionization rates deduced from the electron density profile.

Voss, H. D.↗