Heliophysics Science Division
NASA's Goddard SFC
Greenbelt, MD 20771
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2009 Feb 23: New 'Blog

So I'm trying out blogging now on a site that is designed for it instead of fooling with the html here. I'll continue to post reference materials and my CV here on this page, but if you'd like to follow my thoughts to some degree, please click on the title or here to visit my blog. There's an RSS feed and everything!

2008 Mar 6: Brief History of Global Ion Kinetics

Supported by an LWS Targeted Research and Technology grant, we are further expanding our Global Ion Kinetics (GIK) approach to plasma transport in the magnetosphere. This approach uses multiple models to include the ionospheric source of plasmas in global magnetospheric dynamics. A link at the top left will take you to our results archive, which is more or less logically organized for browsing. In this and subsequent posts, I'll provide some introductory guidance to the archive, and pointers to additional documentation where appropriate. Then I'll report on our GIK progress.

Our GIK approach began with Dominique Delcourt's 1988 effort to model the 3D motion of ions in the magnetosphere. He used an empirical magnetic field model from N Tsyganenko with a simple electric field model from H Volland. Combined with gravity, this allowed a complete, albeit inconsistent description of the motion of ions within the magnetosphere. It was not a very good description of the boundary layers between the magnetosphere and the solar wind, so it wasn't very useful to describe the full interaction of the heliosphere with the magnetosphere and ionosphere.

To improve on Delcourt's early work, I suggested and proposed that the MHD computer simulations of the solar wind interaction, which were at that time becoming available, would provide the best global framework within which to compute ion trajectories including solar wind ions and ionospheric ions. Ray Walker of UCLA agreed to provide MHD simulation results for our proposal and we were funded. However, it soon became clear that the transition to finite element fields of limited resolution was numerically challenging. Barbara Giles and I were trying to use a spline interpolation scheme that had been successful with electrostatic optics, but produced unrealistic energy gains when implmented for electomagnetic fields. The problem was not with the Delcourt code, as Barbara was able to demonstrate very clearly. It was with the interpolation scheme.

As we were struggling with the finite element fields, and distracted by development of the TIDE-PSI investigation for Polar, Vahe Peroomian and Maha Abdalla of UCLA managed to get an ion trajectory code running well within their MHD simulation, and were able to do some of the work we'd been intending to do, calling it Large Scale Kinetics (LSK). However, UCLA has until recently chosen to focus mainly on the entry of solar wind plasmas into the magnetosphere. Thus their effort have been largely complementary to what we had been planning, and UCLA has done a great deal of very nice work using this method.

Mei-Ching Fok joined us and brought to the table a kinetic bounce averaged Vlasov approach she had developed with Janet Kozyra at U Michigan. This code dealt with the inner magnetosphere and required a boundary condition of plasma sources at its outer boundary, just beyond geosynchronous orbit. Mei-Ching wanted to run her inner magnetosphere inside a global MHD simulation, but realized she would need to find a way to introduce ionospheric plasmas at her outer boundary, and MHD had no solution for that. So she set about to make our GIK code work inside MHD. She soon had the Delcourt trajectory code running well in a finite element field description, making it suitable for her needs. Since then we have been steadily working toward a full implementation of all ionospheric outflows into a global MHD simulation, providing boundary conditions to the inner magnetosphere Comprehensive Ring Current Model (CRCM), which is a generalization of Mei-Ching's original inner magnetosphere code that she developed in cooperation with Dick Wolf of Rice U.

March 2006: The Ablationary Magnetosphere

Space scientists have long known that solar storms eject clouds of plasma that energize the magnetospheres and ionospheres of the planets, producing geomagnetic disturbances, auroras, and high energy particles that often damage our space assets. Until recently, it had been thought that hot solar plasmas enter and dominate geospace around the Earth during such storms. Now recent work [Nose et al. 2005] shows that the greater the storm disturbance, the more dominated storm plasmas are by oxygen ablated from the Earth's atmosphere. The largest storms reach over 95% oxygen pressure, indicating that these plasmas are part of the Earth's atmosphere and ionosphere, a tenuous and extremely hot part of the geosphere itself. This means that energy from the solar disturbance is transmitted into the Earth's ionosphere, causing it to be heated and expand outward into space around the Earth. So great is this expansion, confined within the geomagnetic cocoon of Earth, that it inflates the magnetic field, producing the characteristic weakening of the field near the equator that was the first aspect of space storms to be observed by humans. Preliminary efforts to understand and simulate these effects [Moore et al. 2005 GM159] are based on tracking the motions of oxygen ions from the auroras where they are emitted, throughout the magnetosphere, under the influence of storm time global circulation. More refined simulations are in progress that drive the auroral wind outflows locally based on the solar wind energy inputs to the ionosphere as derived from a global circulation model [Moore et al., 2006 JASTP].

Our SMART instrument payload for the MMS mission, led by J. L. Burch of Southwest Research Institute (SwRI), was selected for development. The GSFC role is to develop the Fast Plasma Instrument (FPI). Resolution of rapidly moving short length scale features requires observations from closely-spaced platforms with a measurement cadence less than 30 ms. The FPI exceeds this demanding requirement by acquiring full sky, high-resolution (11deg) electron plasma velocity distributions every 25 ms. FPI also delivers four full sky, medium-resolution (45deg) distributions every 6 ms, for unprecedented access to electron scale dynamics within the reconnection diffusion region. Data compression and burst memory management provide at least 16 minutes of high time resolution data during each orbit of the four MMS spacecraft. Each spacecraft will intelligently downlink the data sequences that contain the greatest amount of temporal structure. For both electrons and ions, FPI will realize these specifications by means of eight half-top-hat energy analyzers. Each analyzer has a 180-deg x 6-deg fan-shaped field of view (FOV) aligned with the s/c spin axis, and is fitted with lateral FOV deflection electrodes. The analyzers are packaged as four Dual Electron Spectrometers and four Dual Ion Spectrometers on each spacecraft. When distributed properly around the spacecraft, these packages provide an instantaneous full-sky view that is independent of spacecraft spin rate. This approach makes available a very large instantaneous aperture for plasma measurements at the high sensitivity required for short exposure measurements. FPI is based on flight heritage from Cluster/PEACE, Geotail/LEP, Polar/Hydra, and Rosetta/IES.

March 2005: Interstellar Boundary EXplorer Selected for Development

Our proposal for the IBEX mission, led by D. J. McComas of Southwest Research Institute (SwRI), was selected for development. The GSFC role consists of science support and development of the Conversion Surface Unit for the IBEX-Lo sensor, which has an energy range similar to that of our IMAGE/LENA imager. IBEX-Lo is a single pixel atomic spectrometer with a very large aperture. The Conversion Surface Unit supports the conical conversion surface, viewing through an annular aperture, collimator, and charged particle rejector.

1 November 2004: Magnetospheric Constellation Mission STDT Report Update Released

An updated synopsis of the report on the Magnetospheric Constellation (MC) Mission has been in preparation for the past year and a half, and a draft is now complete and available for comment online. At this time an electronic version is available in Adobe PDF format that can readily be printed on a local printer. In the future, as permitted by available funding, we are prepared to release a final printed version with a CD-ROM containing a number of graphics and movie products related to the mission. Other materials including the original 2001 STDT report may be found and downloaded from the MC site. MC has been studied and defined by a NASA-appointed Science and Technology Definition Team appointed by the former Sun-Earth Connections Theme. Comments or questions should be directed to the project study scientist Tom Moore (thomas.e.moore@nasa.gov), or to the Chair of the STDT, Harlan Spence (spence@bu.edu).

Owing to technical problems with this site, some materials may not be present that were formerly found here. Recovery is underway. In the meantime if you are looking for "public" files that were here, please let me know by email using the feedback link and I'll expedite them to you...

15 June 2001: Magnetospheric Constellation Mission STDT Report Released

A report on the Magnetospheric Constellation: Dynamic Response and Coupling Observatory (DRACO) has been in preparation for the past two years, and is now complete and available online. Either hard copy or electronic versions can be requested at the link above. The hard copy version comes with a short introductory movie on CD-ROM, and an animated card that illustrates one possible form of magnetotail dynamics that requires a constellation approach for definitive study. A much more revealing movie of this simulated magnetotail behavior can be downloaded from the report site. MC-DRACO is an approved mission of the Solar Terrestrial Probes Program of the NASA Sun Earth Connections Theme, and has been studied and defined by a NASA-appointed Science and Technology Definition Team, as identified in the report.

April 2001: IMAGE Mission Featured in Scientific American

The Imager for Magnetopause to Aurora Global Exploration (IMAGE) mission (see link at left) is the subject of a feature article in the April 01 Scientific American. A paper by PI Jim Burch describes space storms and the pioneering new observations of space weather made by IMAGE. Please visit the IMAGE site for more information about this exciting mission.

26 January 2001: IMAGE Mission Featured in Science

The Imager for Magnetopause to Aurora Global Exploration (IMAGE) mission (see link at left) is a cover story in Science magazine this month. A paper by PI Jim Burch et al. chronicles the pioneering new observations of space weather made by IMAGE. Never before have we been able to see the plasma clouds swirling around the earth as they form and dissipate during geospace storms. This first publication on IMAGE results features images of the cold plasmas in scattered extreme ultraviolet sunlight, and the hot plasmas of the ring current in energetic neutral atom glow, as shown in the linked image. On the left is a blue EUV image showing formation of a spiral plasma tail on the left side of the plasmasphere, around the Earth. The plasmasphere temperature is around 5000°C or 9000°F. On the right is an image of the "ring" of hot plasma just outside the plasmasphere, carrying electrical current around the Earth. The temperature of the ring current is about 1 Billion °C or 1.8 Billion °F. Of course, these images don't do justice to the dynamic behavior of these two important plasma regions near the Earth. Please visit the IMAGE site for more information about this exciting mission.