Science

The Civil Space Mission Area is driven by research, both basic and applied, in a variety of fields. The academic quality of our science investigations is demonstrated in many different fields of interest to NASA that fall into several broad categories: Earth's environs, atmosphere, and aeronomy; space physics, magnetospheres, and the influences of the Sun; and the planetary systems and small bodies in our solar system. All of these research interests are supported by a robust instrument development program as well as software and data processing techniques. APL instruments range from the first hyperspectral imager in space to designs for sample-return technologies.

Planetary   Earth   Heliophysics   Tools & Applications

Planetary

JHU/APL has emerged as a leading planetary science research center. Its almost 40 scientists study all aspects of solar system bodies, and work on a mixture of mutually complementary mission and research activities. The group resides within the more than 700+ strong Space Exploration Sector at APL. The Sector has the capability to implement a mission from initial conception through design, fabrication, launch, mission and science operations, data analysis and scientific research.

Earth

APL is actively conducting cutting edge research in the Earth sciences. Our major thrust areas on in remote sensing of vegetation using plant fluorescence to monitor plant health; use of Synthetic Aperture Radar data to monitor ocean winds; to measure cloud properties and weather imagery using affordable remote sensing solutions; and the study of climate change based on the development of novel techniques to monitor the Total Outgoing Radiation at the top of the atmosphere. Our research and collaborations in this area address a critical challenge as we seek to characterize the processes and our ever changing environment.

Heliophysics

JHU/APL is a leading heliophysics research center. Its almost 60 scientists study all aspects of heliophysics and work on a mixture of mutually complementary mission and research activities. The group resides within the more than 700-strong Space Exploration Sector at APL. The Sector has the capability to implement a mission from initial conception through design, fabrication, launch, operations, and data analysis.

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Tools & Applications

Gamera Logo

Gamera
Grid Agnostic MHD for Extended Research Applications


Gamera is a new magnetohydrodynamic (MHD) code for simulation of diverse magnetized plasma environments. It is a full rewrite of the high-heritage Lyon-Fedder-Mobarry (LFM) model. Gamera is a flexible, portable, user-friendly and exascale-capable code designed to take advantage of supercomputer architectures of the future.


About

Gamera is a new magnetohydrodynamic (MHD) simulation tool building and improving upon the high-heritage Lyon-Fedder-Mobarry (LFM) code. Gamera has been written completely from scratch in modern Fortran and provides a flexible, portable, and exascale-capable MHD code. Gamera features multiple improvements over LFM including: minimal external library dependence, high degree of optimization, OpenMP parallelism allowing use of heterogeneous architectures, and multiple numerics upgrades. Thus, while preserving all key numerical algorithms underlying the LFM code, Gamera provides a robust and user-friendly solution for sustainable future.

Contact info: gamera-devel@listserv.jhuapl.edu

Team

  • K. Sorathia (APL) |
  • B. Zhang (NCAR, now at U. of Hong Kong) |
  • J. Lyon (Consultant) |
  • S. Merkin (APL) |
  • L. Daldorff (APL) |
  • M. Wiltberger (NCAR)

History

LFM code was rewritten by J. Lyon, J. Fedder and C. Mobarry at NRL in the 1980's. Its heritage is traced back to pioneering work on Flux Corrected Transport (FCT) schemes in the same group (J. Boris, D. Book, S. Zalesak, K. Hain). Initial simulations started with very high order spatial interpolation schemes (e.g., 20th order), which was later reduced to 8th order standard today. Over the years, the LFM code or its derivatives have been applied to the terrestrial magnetosphere, planetary magnetospheres (Saturn, Neptune, Uranus, Venus), to inner and outer heliosphere, and regional magnetotail simulations. In 2000's the code was MPI-parallelized which allowed very high resolution simulations reproducing magnetopause boundary instabilities (Kelvin-Helmholtz) and flux-tranfer events (FTEs), ionospheric field-aligned currents with remarkable resemblence to observations, and dipolarization fronts in the magnetotail. Also in 2000's, as part of the Center for Integrated Space Weather Modeling (CISM), a geospace model coupling framework was developed, which allowed implementation of coupling with the Rice Convection Model (RCM) of the inner magnetosphere and the NCAR TIEGCM model of the ionosphere-thermosphere. Finally, in the late 2000's LFM was extended to include the capability to simulate multiple ion fluids. This extension has become known as Multi-Fluid LFM (MFLFM).

Tests

Gamera development has followed a very rigorous approach to code verification and testing. We have performed all standard MHD tests common in astrophysical applications (e.g., Athena tests). These tests highlight the high resolving power of the Gamera algorithms, the quality of solutions on curvilinear grids, and the utility of the Ring Average technique on grids with an axis singularity.

Applications

Gamera was written in a very flexible way and allows easy adaptation to different geometries and initial/boundary conditions via user files. The primary current applications are the terrestrial magnetosphere, the inner heliosphere/solar wind, magnetospheres of outer planets, current sheets and reconnection, and MHD instabilities (e.g, Kelvin-Helmholtz and Rayleigh-Taylor.)

Algorithms

  • Curvilinear grids
    • A key distinguishing feature of the LFM/Gamera MHD algorithm is its finite-volume formulation allowing arbitrary (including non-orthogonal) hexahedral grids.
    • This allows adapting the grid to the geometry of the problem (e.g., packing more grid cells around the magnetopause in magnetospheric calculations) and overall high resolving power with a relatively small total number of grid cells.
    • Gamera improves on the previous LFM algorithm by employing a higher order metrics calculations (12th order Gaussian quadrature.)
  • Partial interface method
    • High (7th or 8th) order spatial interpolation of conserved variables.
    • Aggressive Partial Donor Cell (PDM) Limiter and Left/Right state splitting on primitive variables. Clipping and non-clipping options.
    • Flux calculation uses the gas-kinetic method. However, implementation is flexible and other flux functions can be used.
  • Constrained transport (magnetic flux are defined at cell faces, while electric field is defined at cell edges) keeps magnetic field divergenceless to round-off error.
  • Pole axis treatment (Ring Average) for spherical and cylindrical geometries.
  • Background magnetic field subtraction is necessary in magnetospheric simulations to remove the dominant planetary dipole from field calculations.
  • Conservative and semi-conservative energy equation treatment (total and plasma energy formulations.)
  • Boris correction is critical in magnetospheric simulations where Alfvén speed becomes prohibitevly large near the planet.
  • For magnetospheric applications we have also completely rewritten the ionospheric solver from the LFM code (MIX) and integrated the new Fortran code with Gamera. The new solver (dubbed reMIX) incorporates the standard LFM ionospheric conductivity model, including ionization by solar irradiance and magnetospheric electron precipitation.

Publications

Lyon, J. G., Fedder, J. A., & Mobarry, C. M. (2004). The Lyon-Fedder-Mobarry (LFM) global MHD magnetospheric simulation code. Journal of Atmospheric and Solar-Terrestrial Physics, 66, 1333. http://doi.org/10.1016/j.jastp.2004.03.020

Merkin, V. G., & Lyon, J. G. (2010). Effects of the low-latitude ionospheric boundary condition on the global magnetosphere. Journal of Geophysical Research, 115(A), A10202. http://doi.org/10.1029/2010JA015461

B. Zhang, K. Sorathia, J. Lyon, V. G. Merkin, and M. Wiltberger, Conservative Averaging-reconstruction techniques (Ring Average) for 3-D finite-volume MHD solvers with axis singularity, J. Comput. Phys. (2018), https://doi.org/10.1016/j.jcp.2018.08.020

Two more Gamera techniques papers are currently in review or in preparation. The references will be posted here as they become available.

Contact info: gamera-devel@listserv.jhuapl.edu

 
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MENTAT
The Magnetic MEridional NEUTRAL Thermospheric Wind Model


This research employs a method to derive the magnetic meridional component of equivalent neutral winds in the thermosphere from values of hmF2 derived from ionosonde measurements. The findings of this research provide an improved understanding of thermospheric winds and the resulting empirical wind model will be a useful tool for ionospheric researchers.

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SBMT
The Small Body Mapping Tool



The SBMT is an interactive tool that allows users to visualize and manipulate small body shape models in three dimensions. The Tool enables quick and easy searches for spacecraft data of a variety of small bodies. Once selected, data can be projected directly onto the irregular shapes of these bodies.

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