DOI: 10.5061/dryad.x95x69ptg
title: Data and input supporting: Evolutionary dynamics of counter-helical magnetic flux ropes

description: Upon interaction, a pair of magnetic flux ropes can merge to form a new
 pair, each consisting of opposite helicity along their axis. Magnetic
 helicity along such new structures may annihilate and release the energy
 of the azimuthal magnetic field. In this study, we model the deformation
 dynamics of such structures within the solar wind at 1 AU. The
 perturbation front of deformation propagates along the rope axis at
 approximately the Alfvén speed. However, the process to annihilate 90% of
 the azimuthal components is much slower and is affected by the screw pitch
 of the magnetic field. Such a deformation process causes the plasma in the
 transition region between the two opposite chiralities to spin about the
 rope axis, and plasma heating is discussed accordingly. Our results
 provide insights for estimating the lifetimes of such flux ropes,
 facilitating observational efforts to identify them. This process may also
 apply to the behavior of magnetic flux ropes in other space and
 astronomical plasma environments.
description: Ideal MHD simulation of the evolution of counter-helical flux
 ropes interacting in the 1Au solar wind. BATS-R-Us code
 is used to simulate this evolution (SWMF, 2024): SWMF.
 (2024). University of Michigan space weather modeling framework
 (SWMF) [Software]. https://clasp.engin.umich.edu/research/theory-computational-methods/swmf-downloadable-software/ The data file is stored on Dryad, with input parameters on Zenodo. We want to thank the American Astronomical Society (AAS) Data Editor and Dryad editors for their assistance with presenting this submission.
description: # Evolutionary Dynamics of Counter-Helical Magnetic Flux Ropes ##
 Description of the data and file structure These data are used to plot
 figures 1-7 Each data is in a zip file. Data format: ASCII data files:
 CS3dT0h.zip to CS3dT03h.zip: 3-D SK type MFR models at t=00, 01, 02, and
 03h, as indicated in file names RL3dT00h.zip: 3d initial condition for
 Figure 2a, 3a. CL3dT00h.zip: 3d initial condition for Figure 2b, 3b.
 CH3dT00h.zip: 3d initial condition for Figure 2c, 3c. CH1d5TR.dat: line
 plot data for Figure8a CH1d5Tx0.dat: line plot data for Figure7b
 CH1d5Tx1.dat: line plot data for Figure8b VARIABLES = "Rho
 [amu/cm^3]" "U_x [km/s]" "U_y [km/s]" "U_z
 [km/s]" "B_x [nT]" "B_y [nT]" "B_z
 [nT]" "P [nPa]" "J_x [`` `mA/m^2]" "J_y [
 ```mA/m^2]" "J_z [`mA/m^2]"  "x [Mm]" "y
 [Mm]" "z [Mm]" \`mA is miuA, 1e-6Amp These data are
 generated by simulating the time-evolution of a counter-helical magnetic
 flux rope initially in the solar wind. More detailed description please
 refer to the ApJ paper with the same title and author list. Parameters
 used to run the simulation: Table 1. Parameters And Characteristic Scales
 in The Model, based on 1 AU nominal solar wind characteristics. |
 Parameters | Values | Scales\* | Values | |
 :------------------------------- | :----- | :----------------------------
 | :----- | | Plasma density *n* (/cc) | 5 | Ion inertial length *di* (Mm)
 | 0.1 | | Initial velocity shear u0 (km/s) | 0 | Proton Gyro radius *rg*
 (Mm) | 0.1 | | Plasma temperature *T* (K) | 4´105 | Thermal velocity *vth*
 (km/s) | 60 | | Max field *B0* (nT) | 9 | Alfvén Speed *V*A (km/s) | 50 |
 | MFR Radius *R0* (Mm) | 127 | Sound Speed *C*s (km/s) | 45 | | MFR
 traverse time (Minutes) | 10 | Plasma *b* | \~1 | | Normalized pitch *q* |
 4 | Domain Size (Mm) | 2000 |