| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | August 1, 2013 |
| Latest Amendment Date: | June 4, 2015 |
| Award Number: | 1158206 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Ruth S. Lieberman
AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | August 1, 2013 |
| End Date: | July 31, 2016 (Estimated) |
| Total Intended Award Amount: | $300,000.00 |
| Total Awarded Amount to Date: | $300,000.00 |
| Funds Obligated to Date: |
FY 2014 = $100,000.00 FY 2015 = $100,000.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
3112 LEE BUILDING COLLEGE PARK MD US 20742-5100 (301)405-6269 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
College Park MD US 20742-5141 |
| 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): | AERONOMY |
| Primary Program Source: |
01001415DB NSF RESEARCH & RELATED ACTIVIT 01001516DB 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
The objective of this project is to develop theory, modeling and simulations of low frequency waves during ionospheric heating. A key focus will be the midlatitude ionosphere, and in particular, the upcoming heating experiments using the Arecibo facility, with coordinated measurements at its conjugate region in Argentina. The heating of the ionospheric plasma by modulated high frequency waves leads to physical processes with a wide range of scales. Ionospheric modification experiments have shown the generation of low frequency waves in the presence of the natural current systems, the electrojets, and recent results show the wave generation even in their absence.
Three simulation codes will be used: the first for simulations of low frequency waves and associated processes in the high-latitude region, with a nearly vertical magnetic field. The second code is designed for a general orientation of the magnetic field and will be used for studies of the mid-latitude region. The third code will have a general magnetic field geometry and will simulate the mid-latitude region and its coupling to the high- and low-latitudes, including the effects on the conjugate region. The simulations will also explore the generation of low frequency waves during heating of the low-latitude ionosphere.
Meso-scale phenomena are critical during ionospheric heating and will be the focus of this research. These efforts will enable the development of a comprehensive ionospheric heating model by elucidating the leading processes that bridge the phenomena at micro- and macro-scales. The heating experiments allow the use of the ionosphere as a natural laboratory for exploring fundamental processes, in particular a variety of plasma phenomena.
This work will lead to a better understanding of ionospheric processes which are relevant to telecommunications and satellite technologies, as well as space weather. A graduate student will be trained in the plasma physics of the ionosphere and large-scale numerical simulations. Undergraduate and high school students, including several from under-represented minority groups, will participate in the project and gain direct experience and encouragement to pursue science and technology.
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.
The research goals of the project are to develop thoery, modeling and simulations of low frequency hydromagnetic waves generated during radio frequency heating of the ionosphere, and to study their propagation to the ground and the magnetosphe. While the studies cover the plasma processes in the ionosphere in general, the understanding of the processes during ionospheric heating in the mid-latitude ionosphere is a key objective. Unlike the high latitude region with the auroral electrojet and the equatorial region with the equatorial electrojet, the mid-latitude region has no large scale current system, thus making it more complex and interesting. These studies are expected to be directly relevant to the heating experiments at Arecibo facility.
The major activities were on the development of the numerical simulation codes for studies of the plasma phenomena during radio frequency heating of the ionosphere. The wave propagation code for mid-latitude ionosphere was developed considering the curved geometry of the magnetic field n the mid-latitude region. Another effort was adaptation of a kinetic code to study plasma kinetic processes and turbulence excited by the heating. Comparison with experiments in the high-latitude ionosphere was another significant effort during the grant period.
The generation of hydromagnetic waves during heating of the mid-latitude ionosphere is found to produce a pressure gradient due to the heating, leading to a diamagnetic current which in turn excites magnetosonic waves propagating across the magnetic field. These waves become Alfven waves at lower altitudes due to a change in the relative strengths of the Pederson and Hall conductivities. The Alfven waves however propagate in a different manner as the magnetic field has curved geometry, and the upward propagating waves meet a resonance layer beyond which they can not propagate. This resonance where the wave frequency matches the local ion cyclitron frequency plays a significant role as the waves are mostly unable to propagate to the magnetosphere due to absorption. This result has important implications in the efforts to mitigate the harmful effects of energetic particles in the radiation belt by high power waves launched from the ground.
The numerical simulation codes developed in the project provide versatile tools for studies of wave propagation in conducting media. and can be adapted for applications to other systems. The project provided partial support to three graduate students who completed their thesis research programs during the grant period..
Last Modified: 11/18/2016
Modified by: A. Surjalal Sharma
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