Work Description

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| README.txt |
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Project Information
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Date: 7 March, 2024

Dataset Title: Data pertaining to manuscript titled "Wandering of the Auroral Zone 41,000 Years Ago"

Dataset Creator(s): A. Mukhopadhyay, S. Panovska, R. Garvey, M. Liemohn, N. Ganjushkina, A. Brenner, I. Usoskin, M. Balikhin, D. Welling.

Dataset Contact: Agnit Mukhopadhyay, agnitm@gmail.com

Research Abstract:
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In the recent geological past, Earth’s magnetic field reduced to 4% of the modern values and the magnetic poles moved severely apart from the geographic poles causing the Laschamps geomagnetic excursion, which happened about 41 millennia ago. The excursion lasted for about two millennia, with the peak strength reduction and dipole tilting lasting for a shorter period of 300 years. During this period, the geomagnetic field exhibited significant differences from the modern nearly-aligned dipolar field, causing non-dipole variables to mimic a magnetic field akin to the outer planets while displaying a significantly reduced magnetic strength. However, the precise magnetospheric configuration and their electrodynamic coupling with the atmosphere have remained critically understudied. Here, we present the first space plasma investigation of the exact geomagnetic conditions in the near-Earth space environment during the excursion, and show that the auroral oval, which collectively forms the aurorae borealis (Northern Lights) and australis (Southern Lights) near the poles, expanded and relocated during the large majority of the excursion. The study presents a full 3D reconstruction and analysis of the geospace system including the intrinsic geomagnetic field, magnetospheric system and the upper atmosphere, linked in sequence using feedback channels for distinct temporal epochs. The investigation finds that multipolarity of the intrinsic magnetic field caused the magnetospheric structure to change dramatically and swiftly over the course of a few centuries. These shifts profoundly impacted the formation of the auroral oval and open fieldline regions, causing them to expand and wander towards lower latitudes. The aftermath of this event undoubtedly left a profound imprint on the upper atmosphere’s composition and shaped anthropological progress during that era. Looking through a modern lens, such Laschamps-like upheavals in Earth’s space environment would plunge contemporary technology, including communication channels and satellite infrastructure, into a state of paralysis.

Methodology:
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The data contain the numerical setup and modeling results from space plasma reconstructions of the paleo space environment of Earth conducted using the LSMOD.2 model, Block Adaptive Tree Solar wind-Roe-Upwind Scheme (MATS-R-US) Model and the MAGnetosphere-Ionosphere-Thermosphere (MAGNIT) Auroral Precipitation Model. The dataset is primarily intended to support publication(s) conducted to investigate the paleomagnetic environment of Earth.

Files contained here:
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All reconstruction files for individual temporal epochs are contained. Files cover the following temporal epochs:
- 42,153 years ago (ya)
- 41,168 ya
- 40,977 ya
- 40,531 ya
- 39,900 ya

The files are distributed into four directories.

1. "LSMOD2DataFiles" - This directory contains files from paleomagnetic reconstructions conducted using the LSMOD.2 model. The following files are contained: (a) Files starting with "map_*" and ending with an extension .dat contain the magnetic intensity and inclination values for every latitude-longitude point. (b) Files starting with "map_*" and ending with an extension .png contain an image of the mapped values of the magnetic intensity and inclination values on a Mollweide projection of Earth. (c) The file "LSMOD2_dipoleMoment_dipoleTilt.dat" contains the estimated dipole moment strength and dipole tilt of Earth's magnetic field from 50,000 years ago to 30,000 years ago. (d) The file "Figure1_HiRes.png" contains a high-resolution image of Figure 1 used in the publication supported by this dataset.

2. "BATSRUSDataFiles" - This directory contains files from paleo-magnetospheric reconstructions conducted using the BATS-R-US model. The following files are contained: (a) Files starting with "x_z_*" and ending with an extension .out contain the raw magnetohydrodynamic (MHD) output in the X-Z plane. (b) Files starting with "x_z_*" and ending with an extension .png contain an image of the MHD pressure and magnetic field lines plotted in the X-Z plane. (c) The file "Figure2_HiRes.png" contains a high-resolution image of Figure 2 used in the publication supported by this dataset. The directory "BATSRUS_3d" contains the raw 3D data produced by the MHD reconstruction of the paleo-magnetosphere for each epoch.

3. "MAGNITDataFiles" - This directory contains files from reconstruction of the paleo-aurora using the MAGNIT Auroral precipitation model. The following directories are contained: (a) The directory "RawFiles" contains the shell files at the inner boundary of the MHD domain used to compute the auroral fluxes. (b) The directory "EnergyFluxFigures" contains figures of the auroral energy flux computed by MAGNIT mapped over an orthographic projection of Earth. (c) The directory "AverageEnergyFigures" contains figures of the auroral average energy computed by MAGNIT mapped over an orthographic projection of Earth. (d) The directory "AuroralProjections" contains figures of the boundary of the auroral oval and the open-closed fieldline boundary mapped over an orthographic projection of Earth. (e) The file "Figure3_HiRes.png" contains a high-resolution image of Figure 3 used in the publication supported by this dataset. Note that for the directories containing images, each file is marked either with the suffix "_north" or "_south" to indicate the hemisphere that is plotted.

4. "AnthropogenicDataFiles" - This directory contains files that can be used to map the combined coverage of the auroral zones and open flux zones. The following files are contained: (a) The file "anthroAuroraPolyVertices.txt" contains the vertex coordinates of the polygon that demarcates the coverage area of the auroral zone during the Laschamps event. (b) The file "anthroOCFLBPolyVertices.txt" contains the vertex coordinates of the polygon that demarcates the coverage area of the open fieldlines during the Laschamps event. (c) The file "anthroActivityData.csv" contains a list of all anthropological sites that have been mapped in Figure 4 of the manuscript. References to these sites can be found in the references of the main manuscript and/or the Supplementary Information of the paper. (d) The file "Figure4_HiRes.png" contains a high-resolution image of Figure 4 used in the publication supported by this dataset.

HOW TO READ THE SIMULATION OUTPUT:
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Paleomagnetic data produced by LSMOD.2 can be visualized using a combination of linear plotting and contour plotting tools available commonly in visualization software like Python (e.g. Python/Matplotlib) or MATLAB. Standard tools to read and visualize BATS-R-US and MAGNIT output are already publicly available using IDL and Python (see SpacePy/PyBats - https://spacepy.github.io/pybats.html). For information and details about the post-processed data, visualization and analysis, please contact the authors for details. The anthropological dataset can be visualized using a shape file reader (e.g. Python/GeoPandas) and a linear plotting tool (e.g. Python/Matplotlib).

Related Publications:
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Main Publication: Mukhopadhyay, A., et al. (2024). Wandering of the Auroral Zone 41,000 Years Ago. DOI Forthcoming.

For information about the LSMOD.2 Model, please refer to the following weblink:
- Korte, M., Brown, M. (2019). LSMOD.2 - Global paleomagnetic field model for 50 -- 30 ka BP.
https://doi.org/10.5880/GFZ.2.3.2019.001

For information about the BATS-R-US model, please refer to the following publication:
- Powell, Kenneth G., et al. (1999). "A solution-adaptive upwind scheme for ideal magnetohydrodynamics." Journal of Computational Physics 154.2, 284-309. https://doi.org/10.1006/jcph.1999.6299

For information about the MAGNIT model, please refer to the following publication:
- Mukhopadhyay, Agnit, et al. (2022). "Global driving of auroral precipitation: 1. Balance of sources." Journal of Geophysical research. Space Physics 127.7 (2022). https://doi.org/10.1029/2022JA030323

For information about the Space Weather Modeling Framework, please refer to the following publications and weblinks:
1. Center for Space Environment Modeling (CSEM) - http://csem.engin.umich.edu/
2. Gombosi et al. (2021) "What sustained multi-disciplinary research can achieve: The space weather modeling framework." Journal of Space Weather and Space Climate 11, 42, https://doi.org/10.1051/swsc/2021020.
3. Toth et al. (2005). Space Weather Modeling Framework: A new tool for the space science community. J. Geophys. Res., 110, A12226, doi:10.1029/2005JA011126.
4. Toth et al. (2012). Adaptive numerical algorithms in space weather modeling, Journal of Computational Physics, Volume 231, Issue 3, https://doi.org/10.1016/j.jcp.2011.02.006.

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