Polar magnetic disturbances and the interplanetary magnetic field
IMP measurements on interplanetary magnetic field production of high latitude geomagnetic disturbances
GEOMAGNETIC EFFECT↗
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Boundary of trapped electrons with E more than or equal to 280 keV and disposition of current electrojets in the ionosphere
Geomagnetic latitudes of equivalent linear current at ionospheric heights obtained from DODGE satellite 38-C
Afonina, R. G.↗
Empirical response functions for a neutron multiplicity monitor
Geomagnetic latitude survey by neutron multiplicity monitor covering threshold rigidity ranges at various elevations, relating data to primary cosmic ray rigidity spectrum
Hughes, E. B.↗
Temperature and composition studies in the polar ionosphere
Suprathermal electron temperature and ion composition as function of geomagnetic latitude in polar ionosphere, using Explorer 31 mass spectrometer measurements
Bauer, S. J.↗
Experimental evidence in support of Joule heating associated with geomagnetic activity
High resolution accelerometer measurements in the altitude region 140 to 300 km from a satellite in a near-polar orbit during a period of extremely high geomagnetic activity indicate that Joule heating is the primary source of energy for atmospheric heating associated with geomagnetic activity. This conclusion is supported by the following observational evidence: (1) There is an atmospheric response in the auroral zone which is nearly simulataneous with the onset of geomagnetic activity, with no significant response in the equatorial region until several hours later; (2) The maximum heating occurs at geographic locations near the maximum current of the auroral electrojet; and (3) There is evidence of atmospheric waves originating near the auroral zone at altitudes where Joule heating would be expected to occur. An analysis of atmospheric response time to this heat shows time delays are apparently independent of altitude but are strongly dependent upon geomagnetic latitude.
Devries, L. L.↗
Average daily variations in the magnetic field as observed by ATS-5
Hourly averages of the magnetic field components are determined and analyzed using the measurements, by the magnetic field monitor (MFM) aboard the ATS-5 satellite. The data covering the time period of September 1969 through September 1971 are sorted and analyzed for various Kp values, geomagnetic latitude of the subsolar point, and local time. Local time variations are harmonically analyzed, and amplitudes and phases are given up to the fourth harmonic.
Skillman, T. L.↗
Theory on the precipitation of magnetospheric electrons at the time of a sudden commencement.
At the time of a sudden commencement or even of a sudden impulse, very-low-frequency waves can be excited. In turn, the wave turbulence drives the pitch-angle diffusion of energetic electrons trapped in the magnetosphere, causing them to be precipitated into the lower ionosphere. The distribution of this precipitation as a function of geomagnetic latitude and local time is shown to be directly related to the characteristics of the magnetic disturbances.
Perona, G. E.↗
The shape of the F-region irregularities which produce satellite scintillations Evidence for axial asymmetry.
Correlation analysis of three-station observations of satellite amplitude scintillations, recorded at London, Canada during the summer of 1968, have been interpreted to give information on the height, size and shape of the ionospheric irregularities. The irregularities had a mean height of 390 km, and when interpreted in terms of the usual axially-symmetric, field-aligned model, had a mean axial ratio of 6.5, and a mean dimension transverse to the magnetic field of 0.7 km. None of these parameters showed any systematic trend with geomagnetic latitude. The data for one of the passes analyzed were inconsistent with axial symmetry, and when examined in terms of a more general model, 3 of 9 passes showed evidence of irregularities which were elongated both along and transverse to the earth's magnetic field, the elongation transverse to the field tending to lie in a north-south direction.
Moorcroft, D. R.↗
Earth albedo neutrons from 10 to 100 MeV.
We report the measurement of the energy and angular distributions of earth albedo neutrons from 10 to 100 MeV at 40 deg N geomagnetic latitude from a balloon at 120,000 ft, below 4.65 g/sq cm. The albedo-neutron omnidirectional energy distribution is flat to 50 MeV, then decreases with energy. The absolute neutron energy distribution is of the correct strength and shape for the albedo neutrons to be the source of the protons trapped in earth's inner radiation belt.
Preszler, A. M.↗
Pitch-angle diffusion of radiation belt electrons within the plasmasphere.
Study of the formation of the quiet-time electron slot, which divides the radiation belt electrons into an inner and an outer zone. The pitch-angle diffusion of radiation belt electrons resulting from resonant interactions with the observed plasmaspheric whistler-mode wave band is quantitatively investigated. The effects of wave propagation obliquely to the geomagnetic field direction with the resulting diffusion at all cyclotron-harmonic resonances and the Landau resonance are evaluated along with the effects of interactions occuring at all geomagnetic latitudes. The results obtained account for the long-term stability of the inner radiation zone, the location of its outer edge as a function of electron energy, and the removal of electrons to levels near zero throughout the slot. Computed pitch-angle distributions and precipitation decay rates are in good agreement with slot-region observations.
Lyons, L. R.↗
Radio wave scintillations at equatorial regions
Radio waves, passing through the atmosphere, experience amplitude and phase fluctuations know as scintillations. A characterization of equatorial scintillation, which has resulted from studies of data recorded primarily in South America and equatorial Africa, is presented. Equatorial scintillation phenomena are complex because they appear to vary with time of day (pre-and postmidnight), season (equinoxes), and magnetic activity. A wider and more systematic geographical coverage is needed for both scientific and engineering purposes; therefore, it is recommended that more observations should be made at earth stations (at low-geomagnetic latitudes) to record equatorial scintillation phenomena.
Poularikas, A. D.↗
Calculations of neutron flux spectra induced in the earth's atmosphere by galactic cosmic rays
Calculations have been carried out to determine the neutron flux induced in the earth's atmosphere by galactic protons and alpha particles at solar minimum for a geomagnetic latitude of 42 N. Neutron flux spectra were calculated using Monte Carlo and discrete ordinates methods, and various comparisons with experimental data are presented. The magnitude and shape of the calculated neutron-leakage spectrum at the particular latitude considered support the theory that the cosmic-ray-albedo-neutron-decay mechanism is the source of the protons and electrons trapped in the Van Allen belts.
Armstrong, T. W.↗
Plasmaspheric hiss.
A relatively steady band of ELF hiss has been detected by the OGO 5 search coil magnetometer on almost every passage through the plasmasphere; except for an anomalous region of the dayside at high geomagnetic latitudes, the emissions terminate abruptly at the plasmapause and are therefore referred to as 'plasmaspheric hiss.' A preliminary statistical study of the properties of the observed whistler mode turbulence has yielded the following characteristics: the waves are band limited with a sharp lower-frequency cutoff and a more diffuse upper-frequency cutoff; power spectra show a well-defined maximum near a few hundred hertz, the peak intensities generally ranging between 10 to the minus 7th power and 0.00001 gamma squared/Hz; the wave energy is spread over a bandwidth of a few hundred hertz, and corresponding wideband amplitudes are 5 to 50 milligamma; the waves are highly turbulent in nature and show little tendency toward definite polarization.
Thorne, R. M.↗
Calculations of neutron flux spectra induced in the earth's atmosphere by galactic cosmic rays.
Calculations have been carried out to determine the neutron flux induced in the earth's atmosphere by galactic protons and alpha particles at solar minimum for a geomagnetic latitude of 42 N. Neutron flux spectra in the energy range from about 10 to the minus 8th to about 100,000 MeV at various depths in the atmosphere were calculated by using Monte Carlo and discrete ordinates methods, and various comparisons with experimental data are presented. The magnitude and shape of the calculated neutron leakage spectrum at the particular latitude considered support the theory that the cosmic ray albedo neutron decay (Crand) mechanism is the source of the protons trapped in the inner radiation belt.
Armstrong, T. W.↗
Preliminary results from the first satellite of a high-resolution germanium gamma-ray spectrometer: Description of instrument, some activation lines encountered, and studies of the diffuse spectra
Gamma radiation from terrestrial and extraterrestrial sources were investigated with a high resolution Ge(Li) spectrometer-cryogen system flown onboard a low altitude, spin stabilized, polar orbiting satellite. A brief description is given of the instrument and preliminary results obtained from earth orbit are discussed. Attempts were made to use angular distributions and geomagnetic latitude spectral variations to determine diffuse background spectrum, detect gamma ray line emissions from solar flares, and search for positron annihilation radiation coming from the direction of the galactic center.
Nakano, G. H.↗
Average daily variations in the magnetic field as observed by ATS-5
Hourly averages of the magnetic field components are determined and analyzed using the measurements of the magnetic field monitor aboard the ATS-5. The data covering the time period of September 1969 through September 1971 are sorted and analyzed for various Kp values, geomagnetic latitude of the subsolar point, and local time. Local time variations are harmonically analyzed, and amplitudes and phases are given up to the fourth harmonic.
Skillman, T. L.↗
Eleven-years inversion of the green corona emission
Study of the correlation between the green coronal emission and the polarity pattern of the interplanetary magnetic field for the years 1947-1970. Polarity data of the interplanetary magnetic field inferred from high latitude geomagnetic observations and synoptic tables of the intensity of the green corona emission line (5303 A) are used in the analysis. The analysis results indicate that the coronal features are organized in a constant pattern with respect to the 4-sector structure through the solar cycle. A sudden inversion of the coronal pattern with respect to the sector structure takes place at the solar minima.
Antonucci, E.↗
Analysis of three-component aeromagnetic data
The numerical method of obtaining three field components from total field measurements, using double Fourier series expansion, is presented. The expressions for moments of the anomalous field components over a finite area are given. The magnitude and direction of the magnetization vector indicate that the vertical component of the magnetic field calculated from total field observations is more accurate at higher geomagnetic latitudes than at lower latitudes. The opposite is true for the horizontal components. The error in determining the magnetization vector directions are significantly large over most of the range of variation of declination and inclination of the vector, demonstrating the practical limitations of computing field components from total field data even under the best of conditions.
Bhattacharyya, B. K.↗