The integral spectrum for low‐energy electrons has been measured with detailed definition of temperature and number density throughout the IMP 2 orbit. Electrons are found to have a Maxwellian distribution at energies below 2.0 ev with a component of higher energy. The electron temperature typically increases from above the ionosphere as the square of the radial distance, whereas the number density decreases approximately as the inverse cube of the distance out to 5 RE. From 5 to 15.9 RE (apogee) the temperature remains between 1.0 and 2.0 ev, and the number density remains between 25 and 50 electrons/cm−3. It is verified that the observed positive ion density of 25–50 cm−3 is in agreement with the number of electrons observed per unit volume in the solar wind region. The location of the magnetopause is not evident in the low‐energy electrons; however, a small temperature increase is noted at the shock boundary. An intensity increase is noted in the energetic electron component in the magnetosheath. Data for a six‐month period covering a 180° sector of the earth's environment is reported on.
These observations constitute the first integral measurements in the solar wind region of charged particle spectra in the energy range 0–45 ev. Our observations of the number density are in disagreement with presently accepted solar wind theory but are not inconsistent with previous measurements of the streaming ions.
Measurement of the electron integral spectrum yields electron temperatures ranging from 1 to 4 × 105 °K and having an average value of 1.82 × 105 °K, electron densities having an average value of 4.6 cm−3, and electron‐temperature anisotropies ranging from 1 to 1.4. The electron temperature is found to be independent of solar‐wind speed over the range of 290 to 675 km sec−1. Comparison of the simultaneous alignment of the local magnetic‐field vector with the direction of the electron‐temperature anisotropy reveals a high correlation. Necessary conditions for the fire‐hose instabilities were satisfied in the electron and proton components of the solar‐wind plasma immediately behind an interplanetary shock.
A statistical study of atmospheric‐electric and pertinent meteorological data collected in Argentia, Newfoundland, from January through September 1955, shows that fogs produce a decrease in the electrical conductivity with a concurrent increase in potential gradient. A quantitative analysis of the data shows that during fog (horizontal visibility less than ½ mile, ceiling less than 200 ft) the average conductivity was less than 0.65 times the monthly mean 92 pct of the time and the average potential gradient was more than 2.0 times the monthly mean 87 pct of the time. From one to two hours preceding the onset of fog the conductivity decreased and the potential gradient increased in about 70 pct of the events. One hour prior to dissipation of fog conductivity increased and potential gradient decreased in 75 pct of the events. Similar studies should be made in additional areas to determine whether the Newfoundland results are unique or may be encountered more generally.
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.
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