Net current measurements and secondary electron emission characteristics of the Voyager plasma science experiment and their impact on data interpretation

The Voyager Plasma Science (PLS) instrument is capable of returning integral (DC) current measurements, similar in some respects to measurements made with a Langmuir probe or a retarding potential analyzer, although there are significant differences. The integral measurements were made during a calibration sequence in the solar wind, during Cruise Science Maneuvers, and within the magnetospheres of Jupiter and Saturn by Voyager 1. After the failure of the PLS experiment following the Saturn encounter, that instrument was placed in the DC return mode returning possibly usable data from early 1981 through early 1985. The DC return measurements are difficult to interpret and are above threshold values only for relatively large fluxes; the determination of the measured current level is dependent on the operating temperature of the preamplifiers which further complicates the interpretation. Nevertheless, these measurements can be used to determine the efficiency of the suppressor grid at preventing the loss of secondary electrons off the collector plate. Some DC return measurements have been invaluable in aiding in the interpretation of some electron plasma measurements not previously understood. It is found that electron spectra can be significantly modified by the presence of second generation secondary electrons produced by either first generation secondaries or photoelectrons on the support ring of the negative high voltage modulator grid within the instrument housing

The Outer Heliosphere: Solar Wind, Cosmic Ray and VLF Radio Emission Variations

The Voyager 1 and 2 spacecraft now 45 astronomical units (AU) from Earth continue to monitor the outer heliosphere field and particles environment on a daily basis during their journey to the termination shock of the solar wind. Strong transient shocks continue to be detected in the solar wind plasma. The largest of these are associated with Global Merged Interaction Regions (GMIR's) which, in turn, block cosmic ray entry into the inner heliosphere and are apparently responsible for triggering the two major episodes of VLF radio emissions now thought to come from the heliopause. Distance estimates to the termination shock are consistent with those determined from observations of anomalous cosmic rays. Current observations and implications for heliospheric structure are discussed

Mission Design for the Innovative Interstellar Explorer Vision Mission

The Innovative Interstellar Explorer, studied under a NASA Vision Mission grant, examined sending a probe to a heliospheric distance of 200 Astronomical Units (AU) in a "reasonable" amount of time. Previous studies looked at the use of a near-Sun propulsive maneuver, solar sails, and fission reactor powered electric propulsion systems for propulsion. The Innovative Interstellar Explorer's mission design used a combination of a high-energy launch using current launch technology, a Jupiter gravity assist, and electric propulsion powered by advanced radioisotope power systems to reach 200 AU. Many direct and gravity assist trajectories at several power levels were considered in the development of the baseline trajectory, including single and double gravity assists utilizing the outer planets (Jupiter, Saturn, Uranus, and Neptune). A detailed spacecraft design study was completed followed by trajectory analyses to examine the performance of the spacecraft design options

Coronal disturbances and their effects on the dynamics of the heliosphere

The Sun blows out the solar wind which propagates into the interplanetary medium and forms the heliosphere about 100 AU across. The solar activity causes various types of time-dependent phenomena in the solar wind from long-lived corotating interaction regions to shorter on duration but more extreme events like coronal mass ejections. As these structures propagate outward from the Sun, they evolve and interact with each other and the ambient solar wind. Voyager 1 and 2 provided first unique in-situ measurements of these structures in the outer heliosphere. In particular, Voyager observations in the heliosheath, the outermost region of the heliosphere, showed highly variable plasma flows indicating effects of solar variations extending from the Sun to the heliosphere boundaries. Most surprisingly, Voyager 1 data shows shocks and pressure waves beyond the heliosphere in the interstellar medium. Important questions for the future Interstellar Probe mission are (1) how do the heliosphere boundaries respond to solar variations? (2) how do disturbances evolve in the heliosheath? and (3) how far does the Sun influence extend into the interstellar medium? This talk will review observations and recent modeling efforts demonstrating highly variable and dynamic nature of the global heliosphere in response to disturbances originated in the Sun's atmosphere.https://ui.adsabs.harvard.edu/abs/2019EPSC...13.1229P/abstractPublished versio

The dynamics of the low energy plasma in the Jovian magnetosphere

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1980.Vita.Bibliography: leaves 140-156.by Ralph L. McNutt, Jr.Ph.D

The Constitutionality of the American Legion Plan to Perpetuate Peace

The popularly named Universal Draft bill espoused by the American Legion was the occasion of extended hearings before the War Policies Commission in March, 1931. During those hearings many questions were raised concerning the powers of the Congress and of the President. The material of this article was incorporated in a memorandum prepared and filed in response to those questions by Mr. McNutt, Mr. O\u27Neil and Colonel Robbins, acting on behalf of the American Legion. Mr. McNutt and Mr. O\u27Neil are Past National Commanders of the Legion and are members of the Indiana and Nebraska bars, respectively. Colonel Robbins is Chairman of the National Defense Committee, former Assistant Secretary of War, and a member of the Iowa bar

The Constitutionality of the American Legion Plan to Perpetuate Peace

The popularly named Universal Draft bill espoused by the American Legion was the occasion of extended hearings before the War Policies Commission in March, 1931. During those hearings many questions were raised concerning the powers of the Congress and of the President. The material of this article was incorporated in a memorandum prepared and filed in response to those questions by Mr. McNutt, Mr. O\u27Neil and Colonel Robbins, acting on behalf of the American Legion. Mr. McNutt and Mr. O\u27Neil are Past National Commanders of the Legion and are members of the Indiana and Nebraska bars, respectively. Colonel Robbins is Chairman of the National Defense Committee, former Assistant Secretary of War, and a member of the Iowa bar

Detailed analysis of low energy plasma data under the Voyager Uranus data analysis program

Research effort included the PLS data analysis program where modifications to the data fitting procedure and elimination of possible noise and electron contamination were made. The analysis code corrections were used in checking the Neptune data gathered during the Voyager 2 encounter and for analyzing selected plasma spectra from the warm Io torus. A major task accomplished was the summary of Uranus-related research in the U.S. National Report to the International Union of Geodesy and Geophysics for the 1987 - 1990 quadrennium. A limited amount of work was accomplished on assessing the Pedersen conductivity of the ionosphere and comparing it with inferred values from shielding by the Uranian ring current. Under this grant there has been a great deal of effort expended on identifying and classifying plasma waves and oscillations in the magnetosheath and solar wind downstream from Uranus. Large amplitude oscillations in plasma parameters are found in the magnetosheath, with density changes of up to a factor of ten occurring on times scales of minutes. New algorithms developed for analyzing the inbound bow shock crossing of Neptune will probably be applied to a more detailed analysis of the Uranus shock in the near future