| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | June 4, 2018 |
| Latest Amendment Date: | July 24, 2020 |
| Award Number: | 1834451 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Lisa Winter
AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | September 1, 2017 |
| End Date: | August 31, 2021 (Estimated) |
| Total Intended Award Amount: | $319,837.00 |
| Total Awarded Amount to Date: | $319,837.00 |
| Funds Obligated to Date: |
FY 2017 = $128,044.00 FY 2018 = $137,373.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
6220 CULEBRA RD SAN ANTONIO TX US 78238-5166 (210)522-2231 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
TX US 78238-5166 |
| 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: |
01001718DB NSF RESEARCH & RELATED ACTIVIT 01001819DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
The effects of oxygen ions, flowing out of the ionosphere, on the processes that allow mass, energy, and momentum from the solar wind to penetrate into the magnetosphere is an open question of critical importance in understanding the way the Geospace system works to protect the Earth. This is also a critical element affecting how space weather disturbances are generated in our vicinity. The Geospace system is composed of: (1) the upper regions of our atmosphere, (2) the ionosphere (which is an embedded layer of ions within this region), and (3) the magnetosphere (which is the extension of the Earth's magnetic field into space). The solar wind is the hot upper atmosphere of the sun, which gravity is unable to contain, blowing outward carrying with it solar magnetic fields. Only a few percent of the energy in the solar wind actually leaks into the magnetosphere, which acts as a magnetic shield, but this is enough to power severe space weather disturbances near the Earth. One way solar wind mass and energy leaks into the magnetosphere is through magnetic reconnection which is, essentially, the breaking of the Earth's magnetic field lines and joining with the interplanetary magnetic field lines, accompanied by explosive energy releases. In another process, solar wind momentum and mass are transmitted across the magnetopause through large vortices (called Kelvin-Helmholtz waves) that develop at the interface between the fast solar wind and the much slower magnetospheric plasma. However during disturbed space weather conditions, heated ionospheric oxygen ions flow outward and mix with the hotter more tenuous hydrogen ions in the dayside magnetosphere. Their presence alters the conditions for magnetic reconnection and for the formation of Kelvin-Helmholtz waves. This modulates the entry of the solar wind in unknown ways. This project will combine a coordinated set of spacecraft and ground-based observations with global models to investigate how these processes change in the presence of cooler denser ionospheric-origin oxygen ions and what controls the amount of these oxygen ions that reach the magnetosphere. New knowledge about how the Geospace system works is expected to result from this investigation. The broader impacts are significant including: the further training of a postdoctoral researcher who is also a co-I on the project, the support of two female scientists (one being the PI), which contributes to diversity in the field, and a plan for participating in outreach activities involving high school and undergraduate students. Knowledge gained from this work will also be of interest to researchers studying solar system, astrophysical and laboratory plasmas and will in the long-term be an important component in improving the ability to forecast space weather disturbances of importance to society.
The methodology of the study will combine both statistical and case studies of coordinated observations that connect the dayside magnetopause with outflows from the upper ionosphere or plasmaspheric drainage plumes from the inner magnetosphere. The coordinated observations of magnetosphere and ionosphere parameters will be taken from the MMS, THEMIS, Cluster, Van Allen Probes, DMSP, and FAST satellite datasets; solar wind parameters from ACE and Wind satellites upstream of the Earth; and information on the magnetopause/magnetosphere from ground-based observations including magnetograms, radar and all-sky imagers. Simulations of the global magnetosphere will be used to aid in interpreting the observations.
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 objective of the project is to understand and quantify the effects of cold dense and/or heavy plasma populations on the two major dynamics of Earth?s magnetopause: magnetic reconnection. vs. Kelvin-Helmholtz instability. The cold dense and/or heavy components can participate in and modulate dayside reconnection while they can facilitate the excitation of Kelvin-Helmholtz instability.
Our statistics of the magnetopause crossing events using the data from MMS, THEMIS, and Cluster in terms of IMF (attached figure) indicate that 1) plasmaspheric plume-origin cold ions are often observed in the dusk section and show a positive correlation with Kp index; 2) the ionospheric outflow events show the largest occurrence rate around the subsolar magnetopause; 3) The plume (outflow) events tend to occur during southward (northward) IMF; 4) the occurrence rates of both plumes and outflows increase with the SW dynamic pressure; 5) both reconnection and Kelvin-Helmholtz waves show a positive correlation with Kp. The reconnection (Kelvin-Helmholtz) events show the larger occurrence rate during southward (northward) IMF, as expected; 6) more (37%) magnetic reconnection events occurred than Kelvin-Helmholtz wave events at the presence of cold ion populations at the magnetopause; 7) however, a significant percentage of the reconnection events occurred within/along the boundaries of the large-scale Kelvin-Helmholtz waves developed along the dusk magnetopause, thus, indicating cooperation between Kelvin-Helmholtz waves and magnetic reconnection, which is prominent in the dusk sector.
Our statistical studies indicated the importance of nonlinearly-developed Kelvin-Helmholtz waves, which produce multiple kinetic layers facilitating reconnection. In particular, we emphasize following new findings: 1) we often observe enhanced electron vorticity in the reconnection layer. Although flow vorticity has been widely used in fluid and plasma physics, it has not been frequently used in reconnection physics. We used MMS data to understand the cause of the enhancement of electron vorticity and what information can be deduced from the direction and magnitude of electron vorticity to delineate the electron diffusion region. 2) Multi-site reconnection both in and out of the velocity shear plane results in the generation of flux transfer events (FTEs) on the boundary of Kelvin-Helmholtz vortices which contain cold/heavy populations. We focused on detailed investigation of both 2-D and 3-D structures of the FTE developed along the KHW. 3) We studied/reported a bifurcated current sheet observed at the boundary of Kelvin-Helmholtz vortices to enhance our understanding of the formation and structure of asymmetric reconnection current sheets in the presence of flow shear, density asymmetry, and guide field, which have been rarely studied. We investigated intense electrostatics waves observed on the magnetosheath side of the Kelvin-Helmholtz vortex boundary and the role of cold ions in generating/modulating those waves. The result indicate that these waves may pre-heat a magnetosheath population that is to participate into the reconnection process, leading to two-step energization of the magnetosheath plasma entering into the magnetosphere via Kelvin-Helmholtz vortex-driven reconnection. This strongly indicates that the cold/heavy ions affect reconnection and Kelvin-Helmholtz instability both directly via regulating their dynamics and indirectly via wave generations.
Our study on the role of cold and/or heavy ions on the the magnetic reconnection and Kelvin-Helmholtz waves gives broader impacts since magnetic-field-shear-driven reconnection and flow-velocity-shear-driven Kelvin Helmholtz instability are the two most fundamental physical processes occurring in the heliosphere and the universe. They are crucial in the solar wind-magnetosphere coupling and key to our ability in space weather forecasts under a variety of external interplanetary conditions and structures.
We published total thirteen papers and one book chapter with this NSF grant acknowledged during the entire period of the project.
Last Modified: 11/01/2021
Modified by: Kyoung-Joo Hwang
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