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  • 11
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    Digital techniques for ULF wave polarization analysis (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Digital power spectral and wave polarization analysis are powerful techniques for studying ULF waves in the earth's magnetosphere. Four different techniques for using the spectral matrix to perform such an analysis have been presented in the literature. Three of these techniques are similar in that they require transformation of the spectral matrix to the principal axis system prior to performing the polarization analysis. The differences in the three techniques lie in the manner in which determine this transformation. A comparative study of these three techniques using both simulated and real data has shown them to be approximately equal in quality of performance. The fourth technique does not require transformation of the spectral matrix. Rather, it uses the measured spectral matrix and state vectors for a desired wave type to design a polarization detector function in the frequency domain. The design of various detector functions and their application to both simulated and real data will be presented.
    Keywords: COMMUNICATIONS AND RADAR
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  • 12
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    The statistical character of Pc 4 magnetic pulsations at synchronous orbit (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A statistical study of 215 magnetic pulsation events identified on the basis of waveform and period as Pc 4 (45- to 150-s period) observed at synchronous orbit by ATS 6 is reported. The study was designed to be similar to that done with Pc 3 (10- to 45-s period) by Arthur et al. (1977). These Pc 4 are found to occur most often near 1800 local time but are observed at all local times. The dominant period is approximately 100 s, but a secondary peak in the distribution occurred at approximately 53 s. They tend to be nearly linearly polarized, principally transverse to the ambient magnetic field. The Pc 4 are found to divide naturally into two classes (radial and azimuthal) on the basis of the azimuth of the major axis of polarization. These classes divide further into low-frequency (less than or equal to 0.015 Hz) and high-frequency (greater than or equal to 0.015 Hz) classes. These four classes organize the remaining wave characteristics quite well. Division of the Pc 4 events into these classes does not lead to identification of a single source mechanism as it did with Pc 3. However, some correspondence between the classes and various proposed mechanisms does exist.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 86; Mar. 1
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  • 13
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    Simultaneous ground-satellite observations of Pi 2 magnetic pulsations and their high frequency enhancement (1980)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Pi 2 magnetic pulsations are a frequent occurrence at the earth's surface and have been shown to be clearly correlated with substorm expansion onset. These pulsations are also observed in space at synchronous orbit at the same time as they are seen on the ground at the satellite conjugate point. This brief report describes three days in 1969 on which Pi 2 magnetic pulsations were simultaneously observed at the synchronous satellite ATS 1 and at Tungsten, N.W.T., Canada, near the foot of the ATS 1 magnetic field line. These Pi 2 bursts all exhibit the characteristic waveform and frequency, as well as an 0.3 Hz enhancement, at both locations. This high frequency enhancement appears to be an integral part of Pi 2 bursts both on the surface and at synchronous orbit and should be considered in the development of models of generation mechanisms.
    Keywords: GEOPHYSICS
    Type: Planetary and Space Science; 28; Aug. 198
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  • 14
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    Significant initial results from the environmental measurements experiment on ATS-6 (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The Applications Technology Satellite (ATS-6), launched into synchronous orbit on 30 May 1974, carried a set of six particle detectors and a triaxial fluxgate magnetometer. The particle detectors were able to determine the ion and electron distribution functions from 1 to greater than 10 to the 8th power eV. It was found that the magnetic field is weaker and more tilted than predicted by models which neglect internal plasma and that there is a seasonal dependence to the magnitude and tilt. ATS-6 magnetic field measurements showed the effects of field-aligned currents associated with substorms, and large fluxes of field-aligned particles were observed with the particle detectors. Encounters with the plasmasphere revealed the existence of warm plasma with temperatures up to 30 eV. A variety of correlated waves in both the particles and fields were observed: pulsation continuous oscillations, seen predominantly in the plasmasphere bulge; ultralow frequency (ULF) standing waves; ring current proton ULF waves; and low frequency waves that modulate the energetic electrons. In additon, large scale waves on the energetic-ion-trapping boundary were observed, and the intensity of energetic electrons was modulated in association with the passage of sector boundaries of the interplanetary magnetic field.
    Keywords: LAUNCH VEHICLES AND SPACE VEHICLES
    Type: NASA-TP-1101 , G-7702-F15
    Format: application/pdf
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  • 15
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    Interplanetary magnetic field conditions associated with synchronous orbit observations of Pc3 magnetic pulsations (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; Nov. 1
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  • 16
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    Micropulsations in the morning sector. I - Ground observations of 10- to 45-second waves Tungsten, Northwest Territories, Canada (1973)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 78; Dec. 1
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  • 17
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    Micropulsations in the morning sector. II - Satellite observations of 10to 45-s waves at synchronous orbit, ATS 1 (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A study of 13 wave events having 10- to 45-s periods and observed by ATS 1 in the morning sector reveals that these events, which have been called band-limited pulsations and are thought to be related to Pi 1, appear actually to be Pc 3. Digital power-spectral and coherency analysis was used to determine the characteristics of the wave activity. The average peak frequency of the events (about 0.04 Hz) and their generally narrow-band nature correspond closely with the characteristics of Pc 3. The local-time distribution of the events (peaking at 0900 LT) and their less than complete association with substorms also correspond more closely with Pc 3 characteristics. The orientation of the major axis of the polarization ellipse for these events was predominantly azimuthal, which agrees more closely with the east-west polarization of Pi 1 observed on the ground. However, some examples of radial orientation were observed in the satellite data.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 80; Dec. 1
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  • 18
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    Micropulsations in the morning sector. III - Simultaneous ground-satellite observations of 10- to 45-s period waves near L = 6.6 (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A search for simultaneous 10- to 45-s waves at the synchronous orbit at the location of ATS 1 and at Tungsten, Northwest Territories, Canada (near the foot of the ATS 1 field line), during 1969 resulted in the identification of only one event. This event occurred near 0900-1000 LT and was identified as a Pc 3 event. By combining 1967 data from College, Alaska (near the same L shell as ATS 1), with ATS 1 data, 90 simultaneous events were identified. Analysis of 60 of these events led to the conclusion that Pi 1 are rarely, if ever, observed on the magnetic equator at synchronous orbit, even when Pi 1 activity is present on the ground near the conjugate point. Pc 3, on the other hand, are common at synchronous orbit. A statistical study of the Pc 3 occurring at ATS 1 during simultaneous College wave activity indicated characteristics similar to those observed at ATS 6.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 82; July 1
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  • 19
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    Lunar Explorer 35 - 1967-1968 measurements of picogram dust particle flux in selenocentric space. (1969)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Picogram dust particle flux in selenocentric space measurement by Lunar Explorer 35, showing enhancement during meteor showers
    Keywords: SPACE SCIENCES
    Type: COSPAR, PLENARY MEETING; May 11, 1969 - May 24, 1969; PRAGUE; CZECHOSLOVAKIA
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  • 20
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    Pc 3 magnetic pulsations and precipitation of energetic electrons (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The synchronous altitude satellite ATS 1 data and near-conjugate measurements of bremsstrahlung X-rays and ground magnetic variations were used to analyze an event of modulated auroral zone electron precipitation and magnetic pulsations in the Pc range. Transverse, azimuthal, nearly linearly polarized waves observed at ATS 1, ground magnetic pulsations at College, Alaska, and intervals of modulated electron precipitation centered on local magnetic moon, and noted in the X-ray data from Fort Yukon, Alaska, are discussed, noting that the origin of the Pc 3 waves is attributed to local field line resonances induced by Kelvin-Helmholtz instability at the magnetopause. The wave resonance model can explain observed differences in the pulsation activity at the ground, balloon, and satellite if account is taken of the spatial sensitivities of the techniques and the location of observing sites with respect to the probable location of resonant field lines. The data suggest that electron precipitation pulsations will correlate with Pc 3 magnetic pulsations when substorm injections coupled with azimuthal drift provide enhanced energetic particle fluxes with dayside resonance regions.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 84; Aug. 1
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