Magnetospheric Science Objectives of the <Emphasis Type="Italic">Juno</Emphasis> Mission

In July 2016, NASA’s Juno mission becomes the first spacecraft to enter polar orbit of Jupiter and venture deep into unexplored polar territories of the magnetosphere. Focusing on these polar regions, we review current understanding of the structure and dynamics of the magnetosphere and summarize the outstanding issues. The Juno mission profile involves (a) a several-week approach from the dawn side of Jupiter’s magnetosphere, with an orbit-insertion maneuver on July 6, 2016; (b) a 107-day capture orbit, also on the dawn flank; and (c) a series of thirty 11-day science orbits with the spacecraft flying over Jupiter’s poles and ducking under the radiation belts. We show how Juno’s view of the magnetosphere evolves over the year of science orbits. The Juno spacecraft carries a range of instruments that take particles and fields measurements, remote sensing observations of auroral emissions at UV, visible, IR and radio wavelengths, and detect microwave emission from Jupiter’s radiation belts. We summarize how these Juno measurements address issues of auroral processes, microphysical plasma physics, ionosphere-magnetosphere and satellite-magnetosphere coupling, sources and sinks of plasma, the radiation belts, and the dynamics of the outer magnetosphere. To reach Jupiter, the Juno spacecraft passed close to the Earth on October 9, 2013, gaining the necessary energy to get to Jupiter. The Earth flyby provided an opportunity to test Juno’s instrumentation as well as take scientific data in the terrestrial magnetosphere, in conjunction with ground-based and Earth-orbiting assets.     

Space Radiation Damage Measurements in the Earth Synchronous Orbit

For direct measurement of the integrated radiation dose experienced in Earth synchronous orbit, p-i-n diodes were flown as radiation dosimeters on LES-6. The diode, which has a lifetime of 10-4 seconds in the intrinsic region, was originally developed as a neutron dosimeter, but can detect 1-MeV electron fluences as low as 1013 e·cm-2. Observations over three years in orbit are presented.     

Electromagnetic waves observed by Venus Express at periapsis: Detection and analysis techniques

The magnetometer on Venus Express was designed to be able to obtain 128 Hz samples of the magnetic field from two sensors in a gradiometer configuration. This mode is used around periapsis to determine whether the signals reported at low altitudes near 100 Hz, had the properties of electromagnetic waves generated by electric discharges in the Venus atmosphere. The lack of a magnetic cleanliness program and the shortness of the magnetometer boom make this a challenging measurement. Fortunately the signals are sufficiently strong that they can be easily resolved with rather straightforward analysis techniques.     

Compact antennas for UWB applications

A report on an investigation of spherical, disc, and half-disc antennas in the frequency and time domains with the objective of developing small planar versions of the antennas. These antennas have an omni-directional impulse response in azimuth and pulse duration of 0.5-0.65 nanoseconds. In addition, the measured data show a reasonable peak received signal in a pulse communication link using two identical antennas.     

On the structure and dynamics of the thermosphere

Thermospheric temperature, composition and wind measurements from the Dynamics Explorer satellite (DE-2) are interpreted using a three dimensional, multiconstituent spectral model. The analysis accounts for tides driven by the absorbed solar radiation as well as energy and momentum coupling involving the magnetosphere and lower atmosphere. We discuss phenomena associated with the annual tide, polar circulation, magnetic storms and substorms.     

Transport of ions in presence of induced electric field and electrostatic turbulence: Source of ions injected into ring current

The transport of ions from the polar ionosphere to the inner magnetosphere during stormtime conditions has been computed using a Monte Carlo diffusion code. The effect of the electrostatic turbulence assumed to be present during the substorm expansion phase was simulated by a process that accelerated the ions stochastically perpendicular to the magnetic field with a diffusion coefficient proportional to the energization rate of the ions by the induced electric field. This diffusion process was continued as the ions were convected from the plasma sheet boundary layer to the double-spiral injection boundary. Inward of the injection boundary, the ions were convected adiabatically. By using as input an O⁺ flux of 2.8 × 10⁸ cm^?2 s^?1 (w > 10 eV) and an H⁺ flux of 5.5 × 10⁸ cm^?2 s^?1 (w > .63 eV), the computed distribution functions of the ions in the ring current were found to be in good agreement, over a wide range in L (4 to 8), with measurements made with the ISEE-1 satellite during a storm. This O⁺ flux and a large part of the H⁺ flux are consistent with the DE satellite measurements of the polar ionospheric outflow during disturbed times.     

SAMBO-GEOS: On three-dimensional substorm dynamics — A case study for 4 March 1979

For investigations of the isolated magnetospheric substorm the ground-based and satellite geophysical data are discussed. The active phase of the substorm has two parts: an active-convective phase and a classical active phase. The analysed data show that the breakup of the substorm takes place at closed and not very much stretched magnetic field lines.     

Potential sites for the perception of gravity in the acellular slime mold Physarum polycephalum.

Recently a gravisensitivity of the acellular slime mold Physarum polycephalum, which possesses no specialized gravireceptor, could be established by conducting experiments under simulated and under real near weightlessness. In these experiments macroplasmodia showed a modulation of their contraction rhythm followed by regulation phenomena. Until now the perception mechanism for the gravistimulus is unknown, but several findings indicate the involvement of mitochondria: A) During the impediment of respiration the 0g-reaction is inhibited and the regulation is reduced. B) The response to a light stimulus and the following regulation phenomena strongly resemble the behavior during exposure to 0g, the only difference is that the two reactions are directed into opposite directions. In the blue-light reaction a flavin of the mitochondrial matrix seems to be involved in the light perception. C) The contraction rhythm as well as its modulations are coupled to rhythmic changes in the levels of ATP and calcium ions, involving the mitochondria as sites of energy production and of Ca(++)-storage. So the mitochondria could be the site of the regulation and they possibly are the receptor sites for the light and gravity stimuli. Also the observation of a morphologic polarity of the slime mold's plasmodial strands has to be considered: Cross-sections reveal that the ectoplasmic wall surrounding the streaming endoplasm is much thinner on the physically lower side than on the upper side of the strand--this applies to strands lying on or hanging on a horizontal surface. So, in addition to the mitochondria, also the morphologic polarity may be involved in the perception mechanism of the observed gravisensitivity and of the recently established geotaxis. The potential role of the nuclei and of the contractile elements in the perception of gravity is also discussed.