NASA Scientific and Technical Aerospace Reports

walls and more. I will also list what I believe to be important new modeling objectives. Finally, I will speculate on what is
happening with the magnetic field near the nose of the heliosphere. My conclusion is that models of GCR modulation rarely
incorporate even crudely realistic magnetic fields so it is a wonder that they are as successful as they are and no surprise that
there are still important discrepancies between GCR modulation observations and the models.
Author
Heliosphere; Solar Magnetic Field; Magnetic Fields; Sun; Mathematical Models
20040068142 NASA Marshall Space Flight Center, Huntsville, AL, USA
Properties of Longitudinal Flux Tube Waves, III, Wave Propagation in Solar and Stellar Wind Flows
Cuntz, M.; Suess, S. T.; 2004; 1 pp.; In English; No Copyright; Avail: Other Sources; Abstract Only
We discuss the analytic properties of longitudinal tube waves taking into account ambient wind flows. This is an extension
of the studies of Papers I and II, which assumed a mean flow speed of zero and also dealt with a simplified horizontal pressure
balance. Applications include the study of longitudinal flux tube waves in stars with significant mass loss and heating and
dynamics of plumes in the solar wind. Slow magnetosonic waves, also called longitudinal waves, have been observed in solar
plumes and are likely an important source of heating. We show that the inclusion of ambient wind flows considerably alters
the limiting shock strength as well as the energy damping length of waves.
Author
Stellar Winds; Solar Wind; Magnetoacoustic Waves; Wave Propagation; Longitudinal Waves
20040068151 NASA Ames Research Center, Moffett Field, CA, USA
High-Order Simulation of Non-Linear Oscillations and Shocks in the Solar Atmosphere
Bryson, S.; Kosovichev, A.; Levy, D.; 2004; 2 pp.; In English; Presenation at the International Conference on Spectral and
High-Order Methods, 21-25 Jun. 2004, Providence, RI, USA
Contract(s)/Grant(s): 704-40-42; No Copyright; Avail: Other Sources; Abstract Only
The solar atmosphere presents a rich source of highly non-linear magneto-hydrodynamic phenomena: strong gradients
and forcing terms result in both large shocks and oscillations. The additional requirements of energy balance and initialization
in hydrostatic equilibrium compound the challenge of this problem. A wealth of observational data allows us to check the
results of our simulations. The problem of simulating the solar atmosphere provides, in addition to an interesting system in
its own right, a challenging testbed for high-order shock-capturing methods. We discuss the challenge of simulating solar
atmospheric phenomena, concentrating on various high-order central methods ranging from second to fourth order. Our
method is based on the central-upwind scheme of Kurganov, Noelle and Petrova, which we extend to high order via various
interpolants. We investigate various initial data for our simulations, corresponding to observed conditions in different regions
of the solar surface: the normal quiet sun and sunspots. When non-oscillatory using second- and third-order methods, we are
able to reproduce non-trivial observational results. In particular we find a correlation between initial data and both the shock
speeds and particle oscillation spectra that match observations in the corresponding regions. When using fourth-order WENO
interpolants, we find that while the individual shock profiles at any given time appear non-oscillatory, spurious oscillations
appear in the fields after long time integrations. The issue of initialization in hydrostatic equilibrium raises difficult issues.
Careful treatment of the gravitational source term can reduce violations of hydrostatic equilibrium, but difficulties remain,
primarily due to discontinuities in the piecewise-polynomial reconstructions. In the case of the Euler equations in gravity, the
use of high-order methods reduces the violation of hydrostatic equilibrium to a sufficiently low level for the above described
results to be obtained. Including various energy flux terms in the equations, however, leads to severe instability when
hydrostatic balance is violated. We discuss various strategies to address this problem, including adaptive grid methods.
Author
Hydrostatics; Nonlinearity; Oscillations; Solar Atmosphere; Sun; Upwind Schemes (Mathematics); Simulation
20040068269 NASA Marshall Space Flight Center, Huntsville, AL, USA
External and Internal Reconnection in Two Filament-Carrying Magnetic-Cavity Solar Eruptions
Sterling, Alphonse C.; Moore, Ronald L.; [2004]; 3 pp.; In English; No Copyright; Avail: Other Sources; Abstract Only
We observe two near-limb solar filament eruptions, one of 2000 February 26 and the other of 2002 January 4. For both
we use 195 Angstroms Fe XII images from the Extreme-Ultraviolet (EUV) Imaging Telescope (EIT) and magnetograms from
the Michelson Doppler Imager (MDI), both on the Solar and Heliospheric Observatory (SOHO) satellite. For the earlier event
we also use soft X-ray telescope (SXT), hard X-ray telescope (HXT), and Bragg Crystal Spectrometer (BCS) data from the
Yohkoh satellite, and hard X-ray data from the BATSE experiment on the Compton Gamma Ray Observatory (CGRO). Both
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