Date: 12 June 2023

Dataset Title: The Equatorward and Poleward Boundaries Derived from the Auroral Images by Polar Ultraviolet Imager

Dataset Creators: Chen Wu, Aaron Ridley, Anna DeJong

Dataset Contact: Chen Wu (chenwum@umich.edu)

Funding: 80NSSC20K1581 (NASA)

Methodology:
In this work, after the removal of dayglow and smoothing, individual auroral images of the N2 Lyman-Birge-Hopfield-long (LBHl) and -short (LBHs) emissions measured by Polar Ultraviolet Imager (UVI) were segmented into different sections with the k-means clustering method. Then the background was removed, and the equatorward and poleward boundaries (EB and PB) were identified with a combination of a threshold of 110 R. Each image was binned in ¼ h magnetic local time (MLT) bins and 19 cumulative energy bins were tracked with the energy flux and the latitudinal position in each MLT bin.

Research Overview:
1.5 years of Polar UVI data was used to construct the Feature Tracking empirical model of Auroral Precipitation (FTA). A cumulative energy grid was tracked with the energy flux and the latitude position in each MLT bin for individual images. The auroral characteristics show linear relationships with the Auroral Electrojet (AE) index depending on the MLT region. Thus, the FTA model was constructed to describe the global energy flux and the averaged energy as a function of the AE index based on the LBHl and LBHs emissions. Compared with two other empirical models, FTA predicted more consistent aurora with the observations on 17 March 2013 at higher activity levels.

Files contained here:
The “lbhl” and “lbhs” folders contain the processed LBHl and LBHs emission data by Polar UVI from Jan 1997 to Jun 1998, respectively. Each daily file contains all the LBHl/LBHs images that are binned into 96 MLT bins and the 21 cumulative energy bins. Variables are listed below:

datetime: time (UT)
mlt : magnetic local time (Hour)
ebmlat: geomagnetic latitude at the equatorward boundary (Deg)
pbmlat: geomagnetic latitude at the poleward boundary (Deg)
eb_eg: brightness at the equatorward boundary (R)
pb_eg: brightness at the poleward boundary (R)
bls5 - bls95: geomagnetic latitude for the 5%-95% level grids (Deg)
bls5_eg - bls95_eg: brightness at the 5%-95% level grids (R)
peak: peak intensity in each MLT bin (R)
mlatm: peak intensity location in each MLT bin (Deg)

Fillvalue: 99999.999

Related publication(s):
Wu, C., Ridley, A. J., DeJong, A. D., & Paxton, L. J. (2021). FTA: A Feature Tracking Empirical Model Of Auroral Precipitation. Space Weather, 19, e2020SW002629. https://doi.org/10.1029/2020SW002629

Use and Access: 
This data set is made available under an Attribution-NonCommercial 4.0 International license (CC BY-NC 4.0).