ALBERT

Description: The low-energy charged particle instrument on Voyager was designed to measure the hot plasma (electron and ion energies greater, similar 15 and greater, similar 30 kiloelectron volts, respectively) component of the Jovian magnetosphere. Protons, heavier ions, and electrons at these energies were detected nearly a third of an astronomical unit before encounter with the planet. The hot plasma near the magnetosphere boundary is predominantly composed of protons, oxygen, and sulfur in comparable proportions and a nonthermal power-law tail; its temperature is about 3 x 10(8) K, density about 5 x 10(-3) per cubic centimeter, and energy density comparable to that of the magnetic field. The plasma appears to be corotating throughout the magnetosphere; no hot plasma outflow, as suggested by planetary wind theories, is observed. The main constituents of the energetic particle population ( greater, similar200 kiloelectron volts per nucleon) are protons, helium, oxygen, sulfur, and some sodium observed throughout the outer magnetosphere; it is probable that the sulfur, sodium, and possibly oxygen originate at 1o. Fluxes in the outbound trajectory appear to be enhancedfrom approximately 90 degrees to approximately 130 degrees longitude (System III). Consistent low-energy particle flux periodicities were not observed on the inbound trajectory; both 5-and 10-hour periodicities were observed on the outbound trajectory. Partial absorption of 〉 10 million electron volts electrons is observed in the vicinity of the Io flux tube.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Krimigis, S M -- Armstrong, T P -- Axford, W I -- Bostrom, C O -- Fan, C Y -- Gloeckler, G -- Lanzerotti, L J -- Keath, E P -- Zwickl, R D -- Carbary, J F -- Hamilton, D C -- New York, N.Y. -- Science. 1979 Jun 1;204(4396):998-1003.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17800439" target="_blank"〉PubMed〈/a〉

Description: Measurements of the hot (electron and ion energies 〉/=20 and 〉/= 28 kiloelectron volts, respectively) plasma environment at Jupiter by the low-energy charged particle (LECP) instrument on Voyager 2 have revealed several new and unusual aspects of the Jovian magnetosphere. The magnetosphere is populated from its outer edge into a distance of at least approximately 30 Jupiter radii (R(J)) by a hot (3 x 10(8) to 5 x 10(8) K) multicomponent plasma consisting primarily of hydrogen, oxygen, and sulfur ions. Outside approximately 30 R(J) the hot plasma exhibits ion densities from approximately 10(-1) to approximately 10(-6) per cubic centimeter and energy densities from approximately 10(-8) to 10(-13) erg per cubic centimeter, suggesting a high beta plasma throughout the region. The plasma is flowing in the corotation direction to the edge of the magnetosphere on the dayside, where it is confined by solar wind pressure, and to a distance of approximately 140 to 160 R(J) on the nightside at approximately 0300 local time. Beyond approximately 150 R(J) the hot plasma flow changes into a "magnetospheric wind" blowing away from Jupiter at an angle of approximately 20 degrees west of the sun-Jupiter line, characterized by a temperature of approximately 3 x 10(8) K (26 kiloelectron volts), velocities ranging from approximately 300 to 〉 1000 kilometers per second, and composition similar to that observed in the inner magnetosphere. The radial profiles of the ratios of oxygen to helium and sulfur to helium (〈/= 1 million electron volts per nucleon) monotonically increase toward periapsis, while the carbon to helium ratio stays relatively constant; a significant amount of sodium (Na/O approximately 0.05) has also been identified. The hydrogen to helium ratio ranges from approximately 20 just outside the magnetosphere to values up to approximately 300 inside; the modulation of this ratio suggests a discontinuity in the particle population at approximately 50 to 60 R(J). Large fluctuations in energetic particle intensities were observed on the inbound trajectory as the spacecraft approached Ganymede, some of which suggest the presence of a "wake." Five-and 10-hour periodicities were observed in the magnetosphere. Calculations of plasma flow velocities with the use of Compton-Getting formalism imply that plasma is mostly corotating to large radial distances from the planet. Thus the Jovian magnetosphere is confined by a plasma boundary (as was implied by the model of Brice and Ioannidis) rather than a conventional magnetopause. Inside the plasma boundary there exists a discontinuity at approximately 50 to 60 R(J) we have named the region inside this discontinuity the "inner plasmasphere."〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Krimigis, S M -- Armstrong, T P -- Axford, W I -- Bostrom, C O -- Fan, C Y -- Gloeckler, G -- Lanzerotti, L J -- Keath, E P -- Zwickl, R D -- Carbary, J F -- Hamilton, D C -- New York, N.Y. -- Science. 1979 Nov 23;206(4421):977-84.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17733918" target="_blank"〉PubMed〈/a〉