Effects of geomagnetic secular variations on cosmic ray access to the terrestrial environment

Taking advantage of the cutoff computations performed for more than a hundred locations from 1955 to 1995 [every 5 years; Shea, M.A., Smart, D.F. Vertical cutoff rigidities for cosmic ray stations since 1955, in: Proceedings of the ICRC 2001, Hamburg, Copernicus Gesellschaft, vol. 10, pp. 4063–4066, 2001], we carefully checked the relationship between the vertical cutoff rigidity and the McIlwain parameter introduced by Shea et al. [Shea, M.A., Smart, D.F., Gentile, L.C. Estimating cosmic ray vertical cutoff rigidities as a function of the McIlwain L-parameter for different epochs of the geomagnetic field. Phys. Earth Planet. Int., 48, 200–205, 1987]. We derived an updated algorithm that can be used outside the polar and equatorial regions, avoiding time consuming computations. Results for the European area and 1990 epoch suggest that the fast evaluation is accurate within 0.1 GV in 26 out of the 30 considered locations.     

Global and local geospace modeling in ISTP

The objective of the University of Maryland ISTP theory project is the development of the analytical and computational tools, which, combined with the data collected by the space and ground-based ISTP sensors, will lead to the construction of the first causal and predictive global geospace model. To attain this objective a research project composed of four complementary parts is conducted. First the global interaction of the solar wind-magnetosphe re system is studied using three-dimensional MHD simulations. Appropriate results of these simulations are made available to other ISTP investigators through the Central Data Handling Facility (CDHF) in a format suitable for comparison with the observations from the ISTP spacecrafts and ground instruments. Second, simulations of local processes are performed using a variety of non-MHD codes (hybrid, particle and multifluid) to study critical magnetospheric boundary layers, such as the magnetopause and the magnetotail. Third, a strong analytic effort using recently developed methods of nonlinear dynamics is conducted, to provide a complementary semi-empirical understanding of the nonlinear response of the magnetosphere and its parts to the solar wind input. The fourth part will be conducted during and following the data retrieval and its objective is to utilize the data base in conjunction with the above models to produce the next generation of global and local magnetospheric models. Special emphasis is paid to the development of advanced visualization packages that allow for interactive real time comparison of the experimental and computational data. Examples of the computational tools and of the ongoing investigations are presented.     

The Solar Wind Around Pluto (SWAP) Instrument Aboard New Horizons

The Solar Wind Around Pluto (SWAP) instrument on New Horizons will measure the interaction between the solar wind and ions created by atmospheric loss from Pluto. These measurements provide a characterization of the total loss rate and allow us to examine the complex plasma interactions at Pluto for the first time. Constrained to fit within minimal resources, SWAP is optimized to make plasma-ion measurements at all rotation angles as the New Horizons spacecraft scans to image Pluto and Charon during the flyby. To meet these unique requirements, we combined a cylindrically symmetric retarding potential analyzer with small deflectors, a top-hat analyzer, and a redundant/coincidence detection scheme. This configuration allows for highly sensitive measurements and a controllable energy passband at all scan angles of the spacecraft.     

Synchrotron Radiation from Galactic Sources: What We Can Learn About Particle Acceleration

I review the observations of galactic synchrotron sources, focusing on shell supernova remnants (SNRs), with particular attention to attributes that constrain the properties of electron acceleration. Radio observations provide information on source fluxes, spectral index, morphology, and polarization. Recent observations give us strong reason to believe that several young SNRs show synchrotron X-ray emission. Even if X-rays are thermal, however, limits can be set on the maximum energy to which electrons can be accelerated without a spectral break, since no galactic SNR is observed to have X-ray emission (due to any source) as bright as the extrapolation from radio frequencies of radio synchrotron emission. If synchrotron X-rays are detected or inferred, their morphology and spectrum provide important information on mechanisms governing acceleration to the highest energies. I describe models of synchrotron emission from SNRs and their comparison with observations. Finally, I describe the tasks ahead for both observers and theoreticians, to make better use of what SNR synchrotron emission tells us about particle acceleration.     

An Application of Kalman Filtering and Time Averaging to Inertial Guidance Evaluation

A method is developed for estimating circular error probable values and circular error probable rate values of an inertial navigation system using the concepts of Kalman filtering and time averaging.     

Space nuclear power: technology, policy, and risk considerations in human missions to Mars

There is a large discrepancy between potential needs for nuclear propulsion and power systems for the human exploration of Mars and the current status of R&D funding, public opinion, and governmental support for these technologies. Mission planners and spacecraft designers, energized by the recent claims of possible discovery of life on Mars and responding to increased public interest in the human exploration of Mars, frequently propose nuclear reactors and radioisotope thermoelectric generators (RTGs) for interplanetary spacecraft propulsion and for power supply on the surface of Mars. These plans and designs typically assume that reactors will be available "on-the-shelf," and do not take the extensive R&D costs required to develop such reactors into consideration. However, it is likely that current U.S. policies, if unchanged, will prohibit the launch of nuclear reactors and large RTGs in response to a perceived risk by the public.     

The Onset of Long Term Modulation in the Heliosphere in Cycle 23

The combination of Voyager 1 (77.9 AU, 34.4° N) and Voyager 2 (61.2 AU, 24.5° S) at moderate heliolatitudes in the distant heliosphere and Ulysses with its unique latitudinal surveys in the inner heliosphere along with IMP 8 and other satellites at 1 AU constitutes a network of observatories that are ideally suited to study cosmic rays over the solar minimum of cycle 22 and the onset of solar activity and the long term cosmic ray modulation of cycle 23. Through 2000.7 there have been three well-defined step decreases in the cosmic ray intensity at 1 AU with the cumulative effect being in good agreement with the net decrease in cycle 21 at a comparable time in the solar cycle. Over this period the intensity changes at Ulysses are similar to those at 1 AU. In the distant heliosphere the initial decreases appear to be smaller than those at 1 AU. However the full effects of the interplanetary disturbances producing the most recent and largest step decrease in the inner heliosphere have not yet reached V-2. This revised version was published online in August 2006 with corrections to the Cover Date.