Work Description

Date: 24 October, 2024 Title: Dataset for: Solar wind heavy ions and alpha particles within Earth�s magnetosphere and their variability with upstream conditions Authors: Stephanie Col�n-Rodr�guez, Michael W. Liemohn, and Jim Raines Contact: Stephanie Col�n-Rodr�guez stephcr@umich.edu Funding support: NSF and NASA. Grant Number: 80NSSC21K1405 Key Points: - Wind�s Suprathermal Ion Composition Spectrometer (STICS) provides measurements of the solar wind (SW) ions found in Earth�s magnetosphere. - The entry of SW heavy ions and alpha particles into the magnetosphere varies with upstream Interplanetary Magnetic Field and SW conditions. - The ratio between SW heavy ions and alpha particles exhibit a dawn-dusk asymmetry skewed towards the dawn sector of the magnetosphere. Research Overview: During its trajectory, Wind spent a significant amount of time in the magnetotail, where its SupraThermal Ion Composition Spectrometer (STICS) measured the mass and mass per charge of protons, alpha particles, and heavy ions with an energy/charge ratio up to 226 keV/e. Although STICS originally aimed to measure the abundance of these ion species in the solar wind, its measurements within the magnetosphere from 1995 to 2002 help us identify preferential entry between the different solar wind ion species. This study statistically analyzes how the ratio between solar wind heavy ions and alpha particles (Heavies Solar Wind / He2+) varies for different upstream conditions and locations within the magnetosphere: northward vs. southward Interplanetary Magnetic Field (IMF), low vs. high solar wind density (Nsw), low vs. high solar wind dynamic pressure (PDyn), slow vs. fast solar wind (Vsw), and dawn vs. dusk. Our results indicate that the HeaviesSolar Wind enter the magnetosphere more efficiently than He2+ during northward IMF and that the Heavies Solar Wind / He2+ ratios decrease during high PDyn. In addition, the Heavies Solar Wind / He2+ ratios exhibit a dawn-dusk asymmetry, highly skewed towards the dawn side for all upstream cases likely due to charge-exchange processes. Methodology: The magnetospheric Wind-STICS data is public and can be found on NASA�s Coordinated Data Analysis (CDA) Web (https://cdaweb.gsfc.nasa.gov/). Geomagnetic indexes were obtained from the OMNI Web Service (https://omniweb.gsfc.nasa.gov/ow.html). The data used in this study were combined in a .CSV file and analyzed through a series of Python (.py) scripts. All data in the .CSV files comes from the NASA CDAWeb. Files contained here: Data files: Note that all fill values are entered as either -1.00E+31, NaNs, or zeros and they might appear as blank cells when opened. The Python scripts will automatically read these as a fill value and either ignore or disregard them. 1. data_wind_9598.csv: Wind-STICS data for the years of 1995 to 1998 in 3-min cadence. Data includes: - time and date of the spacecraft: STICS DATETIME - location of the spacecraft in Geocentric-Solar-Ecliptic (GSE) coordinates X (GSE), Y (GSE) - number density of solar wind heavy ions O6+, C5+ and Fe10+ combined: n heavies (STICS) (cm-3) - number density of alpha particles: n He2+ (STICS) (cm-3) - ratio between solar wind heavy ions and alpha particles: Heavies to Alpha ratio (STICS) - Their respective errors: n err O6+ (STICS), n err C5+ (STICS), n err Fe10+ (STICS), and n err He2+ (STICS) - Average energy of alpha particles: E He2+ (STICS) (keV) - Average energy of O6+: E O6+ (STICS) (keV) - Average energy of C5+: E C5+ (STICS) (keV) - Average energy of Fe10+: E Fe10+ (STICS) (keV) - Magnetic field measured: B (Wind MFI) (nT) 2. data_wind_9802.csv: Wind-STICS data for the years of 1998 to 2002 in 3-min cadence. Data includes the same as data_wind_9598.csv with the following additions: - number density of solar wind heavy ions from ACE-SWICS at L1 O6+, C5+ and Fe10+ combined, kept constant for 2-hour intervals to match the 3-min cadence: n heavies (SWICS) (cm-3) - number density of alpha particles from ACE-SWICS at L1, kept constant for 2-hour intervals to match the 3-min cadence: n He2+ (SWICS) (cm-3) - ratio between solar wind heavy ions and alpha particles from ACE-SWICS at L1, kept constant for 2-hour intervals to match the 3-min cadence: Heavies to Alpha ratio (SWICS) 3. data_omni_9598.csv: OMNI data for geomagnetic indexes and upstream parameters for the years 1995 to 1998 in 1-minute cadence. 4. data_omni_9802.csv: OMNI data for geomagnetic indexes and upstream parameters for the years 1998 to 2002 in 1-minute cadence. 5. data_swics_9802_2hr.csv: ACE-SWICS data at L1 for the years 1998 to 2002 in 2-hour cadence. Data includes: - time and date of the spacecraft: SWICS datetime - number density of solar wind heavy ions O6+, C5+ and Fe10+ combined: n heavies (SWICS) (cm-3) - number density of alpha particles: n He2+ (SWICS) (cm-3) - ratio between solar wind heavy ions and alpha particles: Heavies to Alpha ratio (SWICS) - Helium to Oxygen ratio: He/O (SWICS) - Carbon to Oxygen ratio: C/O (SWICS) - Iron to Oxygen ratio: Fe/O (SWICS) - Relative number density of O6+ with respect to O: n O6+ rel (SWICS) (cm-3) - Relative number density of C5+ with respect to C: n C5+ rel (SWICS) (cm-3) - Relative number density of Fe10+ with respect to Fe: n Fe10+ rel (SWICS) (cm-3) - Their respective errors: He2+ err (SWICS), He/O err (SWICS), O6+ err (SWICS), C5+ err (SWICS), C/O err (SWICS), Fe10+ err (SWICS), and Fe/O err (SWICS) .py files: 1. magnetopause_bowshock_model.py: This script defines a function that obtains the averaged bowshock and magnetopause based on the empirical models by Shue et al., (1997) and Chao et al., (2002). References: Shue, J.-H., Chao, J. K., Fu, H. C., Russell, C. T., Song, P., Khurana, K. K., & Singer, H. J. (1997, 5). A new functional form to study the solar wind control of the magnetopause size and shape. Journal of Geophysical Research: Space Physics, 102, 9497-9511. doi: 10.1029/97JA00196 Chao, J., Wu, D., Lin, C.-H., Yang, Y.-H., Wang, X., Kessel, M., . . . Lepping, R. (2002). Models for the size and shape of the earth�s magnetopause and bow shock. In (p. 127-135). doi: 10.1016/S0964-2749(02)80212-8 2. stats_reader_9502.py: This script reads the data and creates a 2-dimensional Histogram of all measurements for the total magnetospheric crossings. A Welch�s t-test is performed with the SciPy.Stats function to compare the dawn and dusk total measurements. 3. stats_split_9502_1hr_averaged.py: This script splits the data corresponding to a particular upstream condition which is averaged up to 1 hour before the measured point. A Welch�s t-test is performed with the SciPy.Stats function to compare the measurements between upstream subcategories. For example, negative vs. positive IMF Bz. 4. stats_dawndusk_IMF_9502.py: This script splits the measurements within a particular IMF upstream condition into dawn and dusk and performs a Welch�s t-test with the SciPy.Stats function to compare these. 5. stats_dawndusk_sw_9502.py: This script splits the measurements within a particular solar wind upstream condition into dawn and dusk and performs a Welch�s t-test to compare these. 6. L1_swics_9802.py: This scrip reads the ACE-SWICS data for the years of 1998 to 2002 and performs a Welch�s t-test the SciPy.Stats function to compare the measurements between upstream subcategories at the L1 point. For example, negative vs. positive IMF Bz. 7. stats_energy_9502.py: This script creates a 2-dimensional Histogram of all the data for the total averaged energy of the individual solar wind species within the magnetosphere: He2+, O6+, C5+, and Fe10+ 8. stats_gyroradii_9502.py: This script calculates the gyroradii of He2+ and O6+ and creates a 2-dimensional Histogram of all the data for both the sheath region and within the magnetosphere. 9. stats_velocity_9502.py: This script calculates the total velocity of He2+, O6+, C5+, and Fe10+ within the sheath region and creates a 2-dimensional Histogram of all the data. 10. tau_charge_exchange_exb_gc.py: This script calculates the charge-exchange time of He2+ and O6+ within the E/q range of 60 � 230 keV/q for different geocentric distances and compares it to the gradient curvature and ExB drifts these particles would do as they drift through the inner magnetosphere. Update Notice: .py Files have been updated from their original version to account for the calculation of uncertainties and the performance of the Welch's t-test on the logarithmic values of the solar wind heavy ions to alpha particles ration (i.e., Heavies Solar Wind / He2+). This change was necessary as these values are normally distributed in logarithmic-space. Therefore, the Welch's t-test must be performed on the logarithmic values. Detailed instructions on how to run the codes: - Download all .CSV and .py files to the same folder. All code runs assuming they are under the same directory name. - Each .py file takes data from the .CSV files. All data in the .CSV files comes from the NASA CDAWeb. - Download the necessary Python Libraries (listed below) and have Python 3.9.13 installed. - Those .py files that start with the word 'stats_' can take between 30-45 minutes to run. This is due to 1) the averaging of OMNI data values needed for the final outcome, and 2) the for loops and if statements that work to disregard measurements taken either downstream or upstream of the magnetopause or bow shock. Python Libraries Needed: - NumPy: https://numpy.org/install/ - Pandas: https://pandas.pydata.org/docs/getting_started/install.html - Datetime: https://pypi.org/project/DateTime/ - Matplotlib: https://matplotlib.org/stable/install/index.html - Matplotlib.patches: https://matplotlib.org/stable/api/patches_api.html - Matplotlib.colors: https://matplotlib.org/stable/api/colors_api.html - SciPy: https://scipy.org/install/ - SciPy.Stats: https://docs.scipy.org/doc/scipy/reference/stats.html - cdasws: https://pypi.org/project/cdasws/ - AstroPy: https://docs.astropy.org/en/stable/install.html - SymPy: https://docs.sympy.org/latest/install.html Python Version: Python 3.9.13 Related publication: Col�n-Rodr�guez, S., Liemohn, M. W., & Raines, J. M (2024). Solar wind heavy ions and alpha particles within Earth�s magnetosphere and their variability with upstream conditions. Journal of Geophysical Research Space Physics. To be submitted in October 2024. Use and Access: This data set is made available under a Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0). To Cite Data: Col�n-Rodr�guez, S., Liemohn, M., Raines, J., Lepri, S. Dataset for: Solar wind heavy ions and alpha particles within Earth�s magnetosphere and their variability with upstream conditions [Data set], University of Michigan - Deep Blue Data. https://doi.org/10.7302/mg8s-qz25 Readme txt file