T HE properties of a low pressure discharge are greatly modified by the presence of a transverse magnetic field of several thousand gauss. The over-all behavior, here described, is believed to be unique to values of gas concentration for which the mean free time of the electrons is much greater than their cyclotron periodicity, and the mean free time of the ions much less than their cyclotron periodicity. The experiments were performed inside a large vacuum chamber having a volume of approximately one cubic meter. When the arc is in a large unconfined region, wind effects are observed which are not present when the discharge is in a small glass tube. Figure 1 illustrates the general appearance of an arc at 0.5 millimeter pressure, transverse to a magnetic field of 6000 gauss. The voltage gradient is approximately 100 volts/cm, and the power input and the current density are many times larger than when the magnetic field is not present. The arc column, in air or nitrogen, is pale blue and quite transparent. Although the power dissipated in the positive column of the arc is more than one-half kw/cm of arc length, the gas temperature is surprisingly low because of the cooling effect of the wind. This temperature is greatly dependent on the manner in which the wind is circulating inside the chamber, and to what extent it is cooled during the recirculating process. Observations based on the melting point of chemical salts indicate that in most cases the arc temperature is less than 600 degrees centigrade.When the air flow is blocked by placing a ceramic sheet on the ''downwind" side of the discharge, the arc flattens out against the sheet and forms a white hot surface layer. If the sheet is placed on the "upwind" side of the arc, so as to block the air from entering the region, the arc then spreads out in all directions. Under such conditions, manometer pressure measurements show that the discharge is acting like an air pump. The air pressure on the side of the ceramic sheet which is adjacent to the arc is about 20 percent of the pressure on the opposite side of the sheet.
A method for determining ambient temperature and ambient pressure in the upper atmosphere is described, using the properties of a supersonic flow field surrounding a right circular cone. The underlying fundamentals stem from basic aerodynamic principles as combined with the developments of the aerodynamics of supersonic cones by G. I. Taylor, J. W. Maccoll, and A. H. Stone. The experiment provides the necessary cone pressures, velocities and Eulerian angles, such that a Mach number characterizing the ambient space conditions may be computed. A description is given of the requisite experimental equipment and related techniques. Experimental data from two rocket-borne equipments are presented with the resulting calculated pressures and temperatures as experienced over New Mexico to approximately 70 kilometers.
Preliminary rather successful attempts to determine the ionization in the E‐layer by means of a probe technique are described. The probe current showed an extremely rapid rise between 90 and 105 km altitude. The result indicates a positive‐ion density about ten times larger than the electron density. Further measurements with improved equipment are recommended.
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