| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | January 27, 2009 |
| Latest Amendment Date: | March 7, 2011 |
| Award Number: | 0842388 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Rachel Walker-Kulzick
AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | April 1, 2009 |
| End Date: | March 31, 2014 (Estimated) |
| Total Intended Award Amount: | $302,300.00 |
| Total Awarded Amount to Date: | $302,300.00 |
| Funds Obligated to Date: |
FY 2010 = $100,241.00 FY 2011 = $106,147.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
3100 MARINE ST Boulder CO US 80309-0001 (303)492-6221 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
3100 MARINE ST Boulder CO US 80309-0001 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | MAGNETOSPHERIC PHYSICS |
| Primary Program Source: |
01001011DB NSF RESEARCH & RELATED ACTIVIT 01001112DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Electrons in Earth's radiation belts can have serious effects on spacecraft electronics through radiation damage and deep dielectric charging. The physical mechanisms governing the variability of these energetic electrons are still hot topics of debate. The paradigm for explaining the creation of the electron radiation belts has recently been shifting from one using only the theory of radial diffusion to one including an important role for plasma waves. The interaction of plasma waves with the electrons can result in in situ heating. This project will investigate the relative contribution of radial diffusion and in situ heating to the enhancement of MeV electrons inside geosynchronous orbit. An internal source term will be added to a currently existing radial diffusion model. Measurements of electrons using Los Alamos National Laboratory (LANL) satellite data at geosynchronous orbit will be used to determine the source population. Realistic loss rates will be determined from data taken from the SAMPEX satellite. The model results will then be compared to GPS satellite measurements inside geosynchronous orbit. In this way, it will be possible to determine how much enhancement of the MeV electrons measured by GPS can be attributed to inward radial transport and how much to in situ heating.
This project will include research and training for graduate students. The results will enhance our ability to predict an important space weather phenomenon.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Through the years, four graduate students have been partially supported by this grant. Some of them have already graduated. They have all been working toward a better understanding what physical mechanisms are responsible for create the energetic particles in the Earth's magnetosphere, aka, radiation belts.
The relativistic electron population in the outer radiation belt is extremely volatile during periods of enhanced geomagnetic activity. During these times, it is constantly subjected to processes, such as loss, transport, and acceleration, which all compete and blend to affect the net electron population in the outer belt. The result is that geomagnetic storms can deplete, enhance, or cause little effect on the outer radiation belt. A detailed understanding of loss, source, and transport is required to fully understand the dynamics of Earth’s natural particle accelerator.
Acceleration mechanisms, which replenish the relativistic electron content, can be classified into two broad categories: radial transport and internal acceleration. Radial transport mechanisms can again be broadly classified into two subcategories: radial diffusion and sudden injection, both of which violate the third adiabatic invariant. Radial transport requires an electron source population at high L, such as the plasma sheet in the tail of the magnetosphere. Radial transport by diffusion in the third adiabatic invariant is a result of incoherent scattering by ULF waves in the Pc4–5 band.
Sudden injection, which is nondiffusive, can occur from a strong interplanetary shock, for example. Both of these mechanisms are well associated with geomagnetic activity.
These graduate students have been working under the supervision of the of PI of this grant. They developed their skills of data processing and analysing, as well as computer simulations. They published their work in peer-reviewed journals and contribute significantly to the research community.
Last Modified: 04/01/2014
Modified by: Xinlin Li
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