Award Abstract # 1743118
Statistical Comparison of Auroras in Northern and Southern Hemispheres

NSF Org: AGS
Division of Atmospheric and Geospace Sciences
Recipient: THE JOHNS HOPKINS UNIVERSITY
Initial Amendment Date: August 27, 2018
Latest Amendment Date: August 27, 2018
Award Number: 1743118
Award Instrument: Standard Grant
Program Manager: Lisa Winter
AGS
 Division of Atmospheric and Geospace Sciences
GEO
 Directorate for Geosciences
Start Date: September 1, 2018
End Date: August 31, 2021 (Estimated)
Total Intended Award Amount: $303,142.00
Total Awarded Amount to Date: $303,142.00
Funds Obligated to Date: FY 2018 = $303,142.00
History of Investigator:
  • Kan Liou (Principal Investigator)
    kan.liou@jhuapl.edu
Recipient Sponsored Research Office: Johns Hopkins University
3400 N CHARLES ST
BALTIMORE
MD  US  21218-2608
(443)997-1898
Sponsor Congressional District: 07
Primary Place of Performance: Johns Hopkins University Applied Physics Laboratory
11100 Johns Hopkins Road
Laurel
MD  US  20723-6099
Primary Place of Performance
Congressional District:
03
Unique Entity Identifier (UEI): FTMTDMBR29C7
Parent UEI: GS4PNKTRNKL3
NSF Program(s): MAGNETOSPHERIC PHYSICS
Primary Program Source: 01001819DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s): 5750
Program Element Code(s): 575000
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.050

ABSTRACT

Auroral displays are an optical manifestation of the Sun-Earth connection, and studying the aurora provides understanding of this connection and their coupling. Owing to geophysical constraints (~2/3 of aurora in the southern hemisphere are above the ocean), there is a lack of information on the southern hemisphere aurora. Current knowledge of the aurora is based primarily on observations made in the Northern Hemisphere. This has prevented full understanding of the magnetosphere-ionosphere as a whole system. With the advent of satellite-based particle and optical imaging and more observations made in the southern polar regions, there is mounting evidence suggesting that auroras are not always hemispherically symmetric and/or conjugate, especially under certain conditions and certain types of aurora. Therefore, studying the aurora from both hemispheres can provide much more information about the polar wind-magnetosphere-ionosphere coupling than any single hemisphere does. This type of approach is essential because past studies have either relied on global auroral images from a single hemisphere or on combined particle data from both hemispheres. The expected results will be made available through the JHU/APL (Johns Hopkins University Applied Physics Laboratory) Auroral Particles and Images Team web site, which serves up a variety of auroral data and models, including the OVATION Prime, to the space physics community. Furthermore, the expected result can be used to update the OVATION Prime auroral model.

The goal of this proposal is to study hemispheric symmetries and asymmetries of the large-scale north and south auroral intensity to improve current knowledge of the solar wind-magnetosphere-ionosphere coupling. Specifically, the following questions are to be addressed as science objectives: (1) Are there relationships between the IMF (Interplanetary Magnetic Field) and the north-south asymmetry of the aurora? (2) Does the southern aurora respond to sunlight in a similar manner as the northern aurora does? and (3) Is there a relationship between the geomagnetic field and auroral intensity? This project consists of analyzing FUV (far-ultraviolet) auroral images acquired by NASA's TIMED/GUVI from both hemispheres. It will be carried out using (1) a large number (~6 years' worth) of near-global auroral images in the FUV band with unprecedented spectral and spatial resolution not only from the Northern Hemisphere but also from the lesser-known Southern Hemisphere and (2) the quantitative inversion of images made at certain wavelengths which can reveal characteristics of these precipitating particles such as their energy and the power they deposit in the upper atmosphere. This method has been tested in recent case studies involving GUVI data and have demonstrated the accuracy and utility of these inversions.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH

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Liou, Kan and Mitchell, Elizabeth J. "Hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation" Scientific Reports , v.10 , 2020 https://doi.org/10.1038/s41598-020-70018-w Citation Details
Liou, Kan and Sotirelis, Thomas and Mitchell, Elizabeth "Control of the EastWest Component of the Interplanetary Magnetic Field on the Occurrence of Magnetic Substorms" Geophysical Research Letters , v.47 , 2020 https://doi.org/10.1029/2020GL087406 Citation Details
Liou, Kan and Sotirelis, Thomas and Mitchell, Elizabeth J. "North-South Asymmetry in the Geographic Location of Auroral Substorms correlated with Ionospheric Effects" Scientific Reports , v.8 , 2018 https://doi.org/10.1038/s41598-018-35091-2 Citation Details
Liou, K. and Mitchell, E. "Effects of the interplanetary magnetic field y component on the dayside aurora" Geoscience Letters , v.6 , 2019 10.1186/s40562-019-0141-3 Citation Details
Liou, K. and Mitchell, E. J. "Hemispheric Asymmetry of the Premidnight Aurora Associated With the DawnDusk Component of the Interplanetary Magnetic Field" Journal of Geophysical Research: Space Physics , v.124 , 2019 10.1029/2018JA025953 Citation Details

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 Aurora Borealis (northern lights) and Auroral Australis (southern lights) are a consequence of energy relaxation of collisionally excited atoms and molecules in the upper atmosphere by collisions with energetic particles from the magnetosphere. The most spectacular auroral displays are associated with recurrent events called auroral substorms (or simply substorms), which occur predominantly close to the local midnight. It is generally thought that substorms should occur nearly simultaneously in both hemispheres at the same local time. However, such a hypothesis has not been confirmed. In this project we test this hypothesis by analyzing 2659 substorm events acquired by the Ultraviolet Imager on board the NASA satellite "Polar". We found that the averaged location for substorm onsets shows a geographic preference (see top panels), which cannot explained by current substorm theories. In the Northern Hemisphere, substorms occurred most frequently in Churchill, Canada (~90°W) and Khatanga, Siberia (~100°E), up to three times as often as in Iceland (~22°W). In the Southern Hemisphere, substorms occurred more frequently over the Antarctic ocean (~120°E), up to ~4 times more than over the Antarctic continent. Such a large difference in the longitudinal distribution of north and south substorm events defies the common belief that substorm occurrence in the NH and SH should be symmetric. A further analysis indicates that these substorm events occurred more frequently when the ionosphere was in dark than in sunlight. These geographic areas also coincide with regions where the Earth's magnetic field is largest (see bottom panels). These facts suggest that auroral substorms occur more frequently, and perhaps more intensely, when the ionospheric conductivity is lower.


Last Modified: 10/28/2021
Modified by: Kan Liou

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