SM31A-0239
The Galileo Heavy Ion Environment--Update to the HIC Model
From 1995 to 2003, the Galileo Heavy Ion Counter (HIC) monitored the high energy (~6 to >200 MeV/nuc), heavy ion (6C to 28Ni) fluxes at Jupiter and returned data for all but 2 of the 35 orbits of the Jupiter system. HIC was based on a re-engineered Voyager Cosmic Ray System instrument and was added to gain a better understanding of the heavy ion radiation environment at Jupiter than that given by the brief flyby missions of Pioneer and Voyager. HIC, as did these spacecraft, found Oxygen and Sulfur to be the primary constituents in the heavy ion environment at Jupiter and adds Carbon to the list. The Carbon is believed to be of solar origin while Oxygen is of mixed solar origin and sputtering off the icy moons of Jupiter. Sulfur is Io-genic. In a previous study, a "HIC Model" was generated from the instrument data to provide estimates of the SEU environment for Jupiter orbiting spacecraft. This presentation updates that model and attempts to fit its findings into the overall picture of ion diffusion at Jupiter as presented by Gehrels, Stone, Cohen, and their colleagues.
SM31A-0240
Hybrid Simulations of Energetic Ion Interaction with Mini Magnetospheres
Solar energetic ions are a know hazard to both spacecraft electronics and to manned space flights, particularly in space missions that extend over a long period of time like interplanetary missions. In Coronal Mass Ejection and Solar Flare conditions the solar wind can reach speeds up to 2000 km/s and particles with energies ranging from MeV to GeV are produced. An effective protection mechanism for spacecrafts has to deal with these energetic particles as well as the regular solar wind flow, with speeds varying from 400 km/s to 700 km/s, with various density profiles and varying Interplanetary Magnetic Field (IMF) conditions. Laboratory experiments are currently under way to assess the feasibility of using a dipole like magnetic field, possibly in conjunction with a plasma source, to provide effective means of protection against solar energetic ions. Preliminary results show a plasma beam being deflected by a dipole like magnetic field generated by a permanent magnet and a mini magnetosphere being generated. We use a massively parallel 3D hybrid code, dHybrid, with kinetic ions and fluid electrons, to tackle the scenario of the interaction of plasma flows and energetic particle distributions with such dipole like fields. Several densities and velocities of the flowing plasma are considered along with different dipole field intensities. In the different setups, the plasma deflection distance varies and an ion-free bubble is created around the spacecraft. Variations in the IMF direction and intensity are also considered in the simulation setups. Results show the plasma deflection distance increasing with the density and magnetic field intensity, and decreasing with the plasma flow velocity. This simulation scenario is compared against experimental results and extrapolation to space plasma parameters is presented.
SM31A-0241
A New Perspective on Inner Zone Proton Data from 1971
The NASA Geospace Radiation Belt Storm Probes Mission will provide a new look at the inner magnetosphere, including the inner zone protons that originate from the decay of neutrons in interactions from galactic cosmic rays with the upper atmosphere. The G-RBSP mission is scheduled for launch in 2012. About forty years prior to the launch of G-RBSP, the US Air Force Orbiting Vehicle 20 (OV1-20) included instrumentation designed to capture a glimpse of the inner zone proton environment up to ~500 MeV. The Aerospace Corporation flew a Cherenkov counter on the OV1-20 propulsion module in a polar orbit of 130 km by ~1950 km; apogee was near the equator, and on-board hardware triggered the transmitter when the count rates were high. The data included singles rates, coincidence rates, and on-board magnetometer measurements. The Cherenkov counter used a fast coincidence between pairs of scintillator disk detectors to define the geometry, thus providing clean measurements in the penetrating, high-rate inner zone environment. The propulsion module re-entered about 10 days after launch in 1971. While the OV1-20 mission life was short, the data could offer an interesting look into the environment near the G-RBSP perigee. We will revisit the OV1-20 proton measurements with the perspective of the science and engineering requirements of G-RBSP as well as results from later missions that also sampled the inner zone protons from different orbits (CRRES; TSX-5; SAMPEX). This work was supported under The Aerospace Corporation's Independent Research and Development Program.
SM31A-0242
Neutron Monitors as a Tool for Specifying Solar Energetic Particle Effects on Earth and in Near-Earth Space
Neutron monitors are ground-based instruments that record the byproducts of collisions between cosmic rays and molecules in Earth's atmosphere. When linked together in real-time coordinated arrays, these instruments can make valuable contributions to the specification of major solar energetic particle events. Neutron monitors can provide the earliest alert of elevated radiation levels in Earth's atmosphere caused by the arrival of relativistic solar particles (Ground Level Enhancement or GLE). Early detection of GLE is of interest to the aviation industry because of the associated radiation hazard for pilots and air crews, especially for those flying polar routes. Network observations can also be used to map, in principle in real time, the distribution of radiation in Earth's atmosphere, taking into account the particle anisotropy which can be very large in early phases of the event. Observations from the large GLE of January 20, 2005 and December 13, 2006 will be used to illustrate these applications of neutron monitors. Supported by NSF grant ATM-0527878, the Thailand Research Fund, and the Mahidol University Postdoctoral Fellowship Program. http://neutronm.bartol.udel.edu/
SM31A-0243
Data on Radiation Belts Derived From Dosimetry Measurements in low Earth Orbits
A small particle telescope based on two silicon detectors was flown on three NASA Shuttle-to-MIR missions and on the Russian orbital station MIR behind a shielding of about 10-20 g/cm2 in low Earth orbits at 51.6 degree inclination during 1996/98. The instrument was also flown as part of DOSMAP and as part of MATROSHKA onboard the ISS during 2001/2004. The instrument was designed to measure count rates and dose rates as well as energy deposit spectra (in silicon) of the radiation inside the spacecraft. The MATROSHKA facility was mounted outside the ISS at the Russian segment. The count rate dependence on the L-parameter for crossings of the inner and outer radiation belts will presented as well as temporal changes of the South Atlantic Anomaly during the years 1996-2004.
SM31A-0244
The Precipitation of Energetic ions into Titan's Atmosphere
The Cassini MIMI instrument has observed energetic protons and oxygen ions in Saturn's&pouter magnetosphere. These ions can precipitate into Titan's atmosphere and drive several important processes. The gyroradii of these energetic ions is large compared to the size of Titan. It is thought that Titan's induced magnetosphere should not play a role in the ion precipitation process. We test weather this is indeed the case using Monte Carlo simulations of the energetic ions. We examine the spatial distribution of these energetic ions as they cross the exobase. Calculate to what degree the induced magnetosphere affects the ion flux into the exobase as a function of the incident ion energy. We also calculate how much energy these ions contribute to Titan's atmosphere, where it is deposited and some of the consequences these precipitating ions have on Titan's&patmosphere.