| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | December 3, 2008 |
| Latest Amendment Date: | January 12, 2011 |
| Award Number: | 0836452 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Anne-Marie Schmoltner
AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | January 1, 2009 |
| End Date: | December 31, 2012 (Estimated) |
| Total Intended Award Amount: | $317,000.00 |
| Total Awarded Amount to Date: | $317,000.00 |
| Funds Obligated to Date: |
FY 2010 = $104,500.00 FY 2011 = $111,500.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
1 SILBER WAY BOSTON MA US 02215-1703 (617)353-4365 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1 SILBER WAY BOSTON MA US 02215-1703 |
| 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: |
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
This project will investigate the midnight temperature maximum (MTM), an enhancement of the neutral temperature (Tn) of roughly 50-200 K in the nighttime equatorial thermosphere. The phenomenon is created by the convergence of air near midnight at low latitudes. Current physics-based numerical models are not able to reproduce the MTM phenomenon with the amplitudes commonly observed. The implication of this inability indicates that the ion-neutral coupling between the low-latitude F-region plasma and the thermosphere and the influence of tidal forcing from below are not well understood. This project will investigate the MTM feature using ion temperature data obtained with Incoherent Scatter Radars (ISRs) from the CEDAR, Madrigal, and local databases. Specifically, since the MTM is an equatorial process, emphasis is placed on MTM characterization using data from the low-latitude Arecibo and Jicamarca ISRs. The ISR MTM will be characterized in terms of amplitude, time of occurrence, and temporal duration. A preliminary count indicates that there are ~400 days of Arecibo and Jicamarca data available for the study, distributed in a way that will allow the determination of seasonal and solar activity variations of the MTM. A ground-based climatology of MTM occurrence has been obtained with Fabry-Perot interferometers (FPIs) at Arequipa, but this climatology does not include the austral summer months (November to early March) due to cloudy conditions. The current project fills this gap with ISR ion temperature data from Jicamarca and expands the climatology to Arecibo's latitude. FPIs provide height-integrated optical information and so provide no information on the height dependence of the MTM. Radars, on the other hand, do provide results as a function of altitude. A systematic study of the height dependence of the MTM is one of the main goals of this project. Knowledge of this height dependence is crucial to any attempt to model, for example, the height penetration of tidal modes, so, as an additional goal, model comparisons of MTM characteristics will be carried out. An additional objective is the comparison of the radar data with optical (FPI and all-sky imager) and digisonde data available at Arecibo and near Jicamarca. This effort provides the first multi-diagnostic study of the MTM. All-sky imager data at El Leoncito (31.8 S) and Millstone Hill ISR (42.6 N) data will be used to study the latitudinal extent of the equatorial MTM phenomenon. The scientific question addressed in this project is: can a multi-diagnostic approach established around the temporal, altitudinal and latitudinal information provided by ISRs improve our knowledge of the MTM?
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.
In this project we studied a phenomenon related to neutral dynamics in the upper atmosphere that can be analyzed by measuring ion temperature data from incoherent scatter radars. Near midnight an enhancement in temperature, lasting for a couple of hours, usually occurs at low latitudes, the so-called midnight temperature maximum (MTM). We fitted the data with functions that take into account different tidal waves and thus we were able to characterize different MTM parameters as a function of local time, season of year and altitude. During local summer it occurs earlier. The amplitude seems to be larger at lower altitudes. It tends to last for only ~ two hours.
The advantage of using ISR technique is that allows us to study this enhancement at different altitudes. Srong MTM signatures have been found at heights close to 450 km.
In addition to the Arecibo radar, Jicamarca and Millstone Hill radar data were also analyzed. All of them showed the occurrence of the MTM. This allowed the comparison at different altitudes and latitudes. Results indicate earlier occurrence time during local summer at Jicamarca.
The results were used to validate model outputs that take into account coupling from below, showing significant day-to-day variability, reflected on data points with large scatter, both in model outputs and in the data.This is a key result that indicates parameters in the upper atmosphere are affected strongly by the behavior of processes occurring in the lower atmosphere, a clear example of the importance of understanding coupling between atmospheric regions.
The project included the contribution from several undergraduates and two graduate students. It also involved the participation of scientists from Jicamarca that allowed a strong interaction with US students.
Results have been presented at different domestic and international meetings. One student received an 'honorable mention' at the 2012 CEDAR workshop, for his poster dealing with MTM analysis at different sites. Three papers have been prepared to summarize this work: two published (Oliver et al., Ann. Geophys., 2012; Martinis et al., JASTP, 2013), and one in preparation (Hickey et al., 2013)
Last Modified: 06/03/2013
Modified by: Carlos Martinis
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