Work Description

Date: 30 April 2024

Dataset Title: May 15 2005 Theta Aurora SWMF Simulation Data & Results

Dataset Creators: Hill, Shannon C.

Dataset Contact: Hill, Shannon C. shanhill@umich.edu

Funding: University of Michigan Rackham Merit Fellowship

Key Points:
- We show first global MHD simulation event study that successfully produces a Joule heating signature that we identify as theta aurora
- Simulation associates transpolar arc signatures with reconnection at the magnetospheric flank and in the distant magnetotail
- The transpolar arc maps to a cross‐tail current disruption and field‐aligned current source region in a highly twisted magnetotail

Research Overview:
The light of the aurora observed in the Earth's atmosphere is a signature
of magnetic processes in outer space. The Sun produces hot magnetized plasma that blows through the solar
system like a wind. The Earth's magnetic field shields us from the harmful impacts of the Sun's magnetized
plasma wind. The interaction between the Earth's magnetic field and the Sun's plasma wind causes the ring of
auroral light we see in the polar regions. Sometimes the ring of auroral light grows a bar of auroral light across
its center (over the Earth's magnetic poles), transforming the ring into a structure like the Greek letter theta. We
call this the theta aurora. It is unknown what physical processes in the Earth's magnetic field create the theta
aurora. In this study we show the first realistic simulation that uses solar wind driver conditions of an observed
theta aurora event, and demonstrate that we can successfully produce the theta aurora structure in the simulation.
We find that the theta aurora's center bar of auroral light comes from multiple regions in the vast Earth's
magnetotail. This new result helps us better understand the dynamics of the Earth'sspace environment and better
protect ourselves against the Sun's hazardous plasma wind effects.

Methodology:
The data are model output from Earth's magnetosphere simulations by the Space
Weather Modeling Framework in the Geospace configuration run on the University of Michigan's Great Lakes HPC cluster.

Date Coverage:
15 May 2005 00:20UT - 08:20 UT. This is the date coverage of the
solar wind input from Wind satelite and the date coverage of the resulting
simulation output.

Instrument and/or Software specifications:
Tecplot 360 2021 R2 was used to process the GM module simulation output (the 3D simulation results in the BATS-R-US domain).
global_energetics python software (see zipped folder) used with Tecplot 360 2021
R2.

Software needed:
Tecplot 360 2021 R2
Python 3.9.0
python packages spacepy 0.5.0a0
swmfpy 2022.1
pytecplot 1.3.3
numpy 1.26.4
matplotlib 3.4.3
pandas 1.1.4
python software global_energetics (locally downloaded, see following section Files and Folders
contained here)

Files and folders contained here:

theta_aurora_paper_figures_deepblue.py - Python file that includes multiple function
definitions for processing and subsequently plotting the SWMF simulation data found in the SWMF_GM_output
folder and the SWMF_IE_output folder and the SWMF simulation *.log files. The
function defintions also use the IMF_WIND_shifted.dat file and the
20230320-19-54-supermag.csv file. The specific functions used for the final
submission of the GRL paper that cites this data set are:
theta_aurora_figure1_GRL_resubmit and theta_aurora_figure2_GRL_resubmit.

global_energetics.zip - folder of locally developed python software by Dr.
Austin Brenner at the University of Michigan used to interface with Tecplot via
python. This package is called in theta_aurora_paper_figures_new.py with the
line 'import global_energetics.extract.stream_tools as tools'.

log_e20050515-002000.log - Output file from SWMF simulation that contains the
simulation calculated SYM/H and the simulation calculated cross polar cap
potential for each hemisphere for each minute of the simulation (00:20 UT to
08:20 UT 15 May 2005). This file is used with theta_aurora_paper_figures_new.py to plot the SYM/H comparison betweem
simulation results and observations.

geoindex_e20050515-002000.log - Output file from SWMF simulation that contains
the simulation calculated AE, AL, and AU index for each minute of the simulation
(00:20 UT to 08:20 UT 15 May 2005). This file is used with
theta_aurora_paper_figures_new.py to plot the AL comparison between simulation
results and observations.

IMF_WIND_shifted.dat - The input file for the SWMF simulation. It contains the
solar wind observations from the Wind satelite at L1. The input solar wind
observations are shifted 20 minutes to account for propagation time between L1
and the magnetosphere bow shock at Earth.

20230320-19-54-supermag.csv - The supermag observations of the AL index and the
SYM/H index (called SMR and SML by supermag) used to compare to the SWMF
simulation calculations of the SYM/H and AL (found in the *.log files described
above).

The folders contain the simulation data from two separate simulation domains (IE
and GM).

- Folder SWMF_GM_output: 417 files (156.57 GB) with *.plt extension. Used with
Tecplot software. Data output between 00:35 UT to 07:49 UT 15 May 2005.
- Folder SWMF_IE_output: 481 files (5.54 GB) with *.idl extension. Used with
spacepy.pybats.rim python package. Data output between 00:21 UT to 08:19 UT 15
May 2005.

Related publication(s):
Hill, S. C., Pulkkinen, T. I., Brenner, A., Al Shidi, Q., Mukhopadhyay, A., Kullen, A., et al. (2024). Magnetospheric sources of theta aurora: A case study comparing observations with SWMF global simulation. Geophysical Research Letters, 51, e2023GL108002. https://doi.org/10. 1029/2023GL108002

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

To Cite Data:
Hill, S. C. May 15 2005 Theta Aurora SWMF Simulation Data & Results [Data set], University of Michigan - Deep Blue Data. https://doi.org/10.7302/9fgf-9459