DOI: 10.5061/dryad.s1rn8pkk5
title: Data from: Multi-fluid MHD study of the disappearing solar wind event observed by MAVEN: Effects of solar wind density

description: Using the latest Mars Multi-fluid Magneto-hydrodynamic (MHD) model, we
 examined the extremely low solar wind density event observed by Mars
 Atmosphere and Volatile Evolution (MAVEN) on December 26, 2022. Simulation
 results show that the solar wind density plays a crucial role in plasma
 interactions. The interaction region expands significantly from less than
 2 RM under typical solar wind density conditions to more than 4 RM along
 the subsolar line for extremely low solar wind density (&lt; 0.1
 cm^-3^), consistent with MAVEN observations during the event. Under low
 solar wind density conditions, the ion pickup plume becomes smaller and is
 associated with a lower flow speed. Model results also show a nonlinear
 correlation between the solar wind density and the ion escape rates.
 Specifically, when the solar wind density is relatively high (&gt; 0.2
 cm^-3^), the total ion loss rate positively correlates with the solar wind
 density. However, when the solar wind density is extremely low, ion escape
 rates are nearly constant despite further decreases in solar wind density.
 For this event, the solar wind density dropped by over an order of
 magnitude, while the MHD model predicts the total ion escape rate reduced
 by approximately a factor of ~3. Additionally, we investigated possible
 reasons for the sudden drop in magnetic field strength during the inbound
 segment of two consecutive orbits and found that a sudden change of the
 interplanetary magnetic field (IMF) direction to radial configuration
 could also contribute to the observed field decrease.
description: # Data from: Multi-fluid MHD study of the disappearing solar wind event
 observed by MAVEN: Effects of solar wind density Dataset DOI:
 [10.5061/dryad.s1rn8pkk5](10.5061/dryad.s1rn8pkk5) ## Description of the
 data and file structure Multi-fluid MHD model results from 8 cases as
 specified in the paper.  ### Files and variables
 Fig1a_n3_3d__ful_7_n00040000.dat.zip Fig1b_n01_3d__ful_7_n00040000.dat.zip
 **Description:** 3D MHD data for Fig1a and Fig1b in ascii format. The
 variable list/unit is given below. '"X [R]" "Y
 [R]" "Z [R]" "r [amu/cm^3]" "U_x
 [km/s]" "U_y [km/s]" "U_z [km/s]" "B_x
 [nT]" "B_y [nT]" "B_z [nT]" "Pe [nPa]"
 "p [nPa]" "B1_x [nT]" "B1_y [nT]" "B1_z
 [nT]" "E [J/m^3]" "J_x [mA/m2]" "J_y
 [mA/m^2]"_z [mA/m2]"' Of these variables: * **X [R], Y [R],
 Z [R]** — position in the MSO coordinate system * **r [amu/cm³]** — total
 mass density * **U_x [km/s], U_y [km/s], U_z [km/s]** — plasma velocity
 components * **B_x [nT], B_y [nT], B_z [nT]** — total magnetic field
 components * **Pe [nPa], p [nPa]** — electron and ion plasma thermal
 pressures, respectively * **B1_x [nT], B1_y [nT], B1_z [nT]** — induced
 magnetic field components * **E [J/m³]** — electric field * **J_x [mA/m²],
 J_y [mA/m²], J_z [mA/m²]** — current density components in the MSO
 coordinate system Fig2_sat_sat2022_12_25_29_sat_n000000.dat.zip
 Fig3_sat_sat2022_12_25_29_sat_n000000.dat.zip
 Fig4_n008_sat_sat2022_12_25_28_sat_n000000.dat  **Description:** Satellite
 files for Fig2, Fig3 and Fig4 from the MHD model in ascii format. The
 variable list/unit is included in the header of the satellite files, and
 also given below. VARIABLES="it" "Year" "mn"
 "day" "hour" "min" "Sec"
 "ms" "X [R]" "Y [R]" "Z [R]"
 "r [amu/cm^3]" "U_x [km/s]" "U_y [km/s]"
 "U_z [km/s]""B_x [nT]" "B_y [nT]" "B_z
 [nT]" "pe [nPa]" "p [nPa]" "rHp
 [amu/cm3]" "HpU_x [km/s]" "HpU_y [km/s]"
 "HpU_z [km/s]" "HpP [nPa]" "r^O^2^p
 [amu/cm^3]" "O2pU_x [km/s]" "O2pU_y [km/s]"
 "O2pU_z [km/s]""O2pP [nPa]" "rOp [amu/cm3]"
 "OpU_x [km/s]" "OpU_y [km/s]" "OpU_z
 [km/s]""OpP [nPa]" "r^C^O^2^p [amu/cm^3]"
 "CO2pU_x [km/s]" "CO2pU_y [km/s]" "CO2pU_z
 [km/s]" "CO2pP [nPa]" "B1_x [nT]" "B1_y
 [nT]" "B1_z [nT]" "e" "J_x [mA/m2]"
 "J_y [mA/m^2]" "J_z [mA/m2]" Of these variables: *
 **it** — iteration number * **Year, mn, day, hour, min, Sec, ms** — date
 and time (year, month, day, hour, minute, second, millisecond) * **X [R],
 Y [R], Z [R]** — position in the MSO coordinate system * **r [amu/cm³]** —
 total mass density * **U_x [km/s], U_y [km/s], U_z [km/s]** — plasma
 velocity components * **B_x [nT], B_y [nT], B_z [nT]** — total magnetic
 field components * **Pe [nPa], p [nPa]** — electron and ion plasma thermal
 pressures, respectively * **rHp [amu/cm³], HpU_x [km/s], HpU_y [km/s],
 HpU_z [km/s], HpP [nPa]** — density, velocity, and pressure of H⁺ * **rO2p
 [amu/cm³], O2pU_x [km/s], O2pU_y [km/s], O2pU_z [km/s], O2pP [nPa]** —
 density, velocity, and pressure of O₂⁺ * **rOp [amu/cm³], OpU_x [km/s],
 OpU_y [km/s], OpU_z [km/s], OpP [nPa]** — density, velocity, and pressure
 of O⁺ * **rCO2p [amu/cm³], CO2pU_x [km/s], CO2pU_y [km/s], CO2pU_z [km/s],
 CO2pP [nPa]** — density, velocity, and pressure of CO₂⁺ * **B1_x [nT],
 B1_y [nT], B1_z [nT]** — induced magnetic field components * **E
 [J/m³]** — electric field * **J_x [mA/m²], J_y [mA/m²], J_z [mA/m²]** —
 current density components in the MSO coordinate system
 ‘Fig5_SWP_WIND_MAVEN_new.dat **Description:** Solar wind proxy file for
 Figure 5 in ascii format. The variable list/unit is included in the header
 of the satellite files, and also given below: VARIABLES="Year"
 "mn" "day" "hour" "min"
 "Sec" "ms" “bx” “by” “bz” 
 "H<sup>+</sup>"
 "V<sub>X</sub>" Of these variables: * **Year, mn,
 day, hour, min, Sec, ms** — date and time (year, month, day, hour, minute,
 second, millisecond) * **bx, by, bz** — magnetic field components in the
 chosen coordinate system [nT] * **H⁺** — density of protons (H⁺ ions)
 [amu/cm³] * **Vₓ** — x-component of the bulk plasma velocity [km/s]
 Fig6_7_2DXZ_density_velocity_n3n05n01.dat **Description:** 2D (XZ plane
 cut) data files for Figure6 and Figure 7. The variable list/unit is given
 below:  VARIABLES="X [R]" "Y [R]" "Z [R]"
 "r [amu/cm^3]" "U_x [km/s]" "U_y [km/s]"
 "U_z [km/s]""B_x [nT]" "B_y [nT]" "B_z
 [nT]" "pe [nPa]" "p [nPa]" "rHp
 [amu/cm3]" "HpU_x [km/s]" "HpU_y [km/s]"
 "HpU_z [km/s]" "HpP [nPa]" "r^O^2^p
 [amu/cm^3]" "O2pU_x [km/s]" "O2pU_y [km/s]"
 "O2pU_z [km/s]""O2pP [nPa]" "rOp [amu/cm3]"
 "OpU_x [km/s]" "OpU_y [km/s]" "OpU_z
 [km/s]""OpP [nPa]" "r^C^O^2^p [amu/cm^3]"
 "CO2pU_x [km/s]" "CO2pU_y [km/s]" "CO2pU_z
 [km/s]" "CO2pP [nPa]" "B1_x [nT]" "B1_y
 [nT]" "B1_z [nT]" "e" "J_x [mA/m2]"
 "J_y [mA/m^2]" "J_z [mA/m2]" Of these variables: * **X
 [R], Y [R], Z [R]** — position in the MSO coordinate system * **r
 [amu/cm³]** — total mass density * **U_x [km/s], U_y [km/s], U_z
 [km/s]** — plasma velocity components * **B_x [nT], B_y [nT], B_z [nT]** —
 total magnetic field components * **Pe [nPa], p [nPa]** — electron and ion
 plasma thermal pressures, respectively * **rHp [amu/cm³], HpU_x [km/s],
 HpU_y [km/s], HpU_z [km/s], HpP [nPa]** — density, velocity, and pressure
 of H⁺ * **rO2p [amu/cm³], O2pU_x [km/s], O2pU_y [km/s], O2pU_z [km/s],
 O2pP [nPa]** — density, velocity, and pressure of O₂⁺ * **rOp [amu/cm³],
 OpU_x [km/s], OpU_y [km/s], OpU_z [km/s], OpP [nPa]** — density, velocity,
 and pressure of O⁺ * **rCO2p [amu/cm³], CO2pU_x [km/s], CO2pU_y [km/s],
 CO2pU_z [km/s], CO2pP [nPa]** — density, velocity, and pressure of CO₂⁺ *
 **B1_x [nT], B1_y [nT], B1_z [nT]** — induced magnetic field components *
 **E [J/m³]** — electric field * **J_x [mA/m²], J_y [mA/m²], J_z
 [mA/m²]** — current density components in the MSO coordinate system
 Fig8_1D_pressure_n3n008.dat **Description:** 1D pressure files for Figure8
 VARIABLES="X [R]" "Y [R]" "Z [R]" "r
 [amu/cm^3]" "U_x [km/s]" "U_y [km/s]" "U_z
 [km/s]""B_x [nT]" "B_y [nT]" "B_z [nT]"
 "pe [nPa]" "p [nPa]" "rHp [amu/cm3]"
 "HpU_x [km/s]" "HpU_y [km/s]" "HpU_z [km/s]"
 "HpP [nPa]" "r^O^2^p [amu/cm^3]" "O2pU_x
 [km/s]" "O2pU_y [km/s]" "O2pU_z [km/s]""O2pP
 [nPa]" "rOp [amu/cm3]" "OpU_x [km/s]" "OpU_y
 [km/s]" "OpU_z [km/s]""OpP [nPa]" "r^C^O^2^p
 [amu/cm^3]" "CO2pU_x [km/s]" "CO2pU_y [km/s]"
 "CO2pU_z [km/s]" "CO2pP [nPa]" "B1_x [nT]"
 "B1_y [nT]" "B1_z [nT]" "e" "J_x
 [mA/m2]" "J_y [mA/m^2]" "J_z [mA/m2]"
 "B" "U" "P_B" "P_D"
 "P_T" "Uh" "P_Dh" "B0"
 "P_B0" Of those variables, the beginning list of the variables
 are the same as listed in Fig 6 & 7. The meaning of additional
 variable are listed below. ·      **B** — magnetic field strength [nT]
 ·      **U** — flow speed [km/s] ·      **P_B, P_D, P_T** — plasma
 magnetic pressure, dynamic pressure, and total pressure [nPa] ·     
 **U_h** — horizontal flow speed [km/s] ·      **P_Dh** — horizontal
 dynamic pressure [nPa] ·      **B₀** — crustal magnetic field strength
 [nT] ·      **P_B0** — magnetic pressure of the crustal magnetic field
 [nPa] Fig9_flux_nsw.dat **Description:** escape rates for all cases
 VARIABLES = "swden" "O<sup>+" "O^+
 div" "O<sub>2</sub><sup>+" "O_2^+
 div" "CO<sub>2</sub><sup>+" "CO_2^+
 div" "total ion loss" "total mass loss" Of these
 variables: * **swden** — solar wind density * **O⁺** — escape rate of O⁺ *
 **O₂⁺** — escape rate of O₂⁺ * **CO₂⁺** — escape rate of CO₂⁺ * **total
 ion loss** — total ion escape rate (in number) * **total mass loss** —
 total mass escape rate Fig10_rIMF_3d__mhd_6_n0040000.dat
 **Description:** 3D MHD data for Fig10 for radial IMF case. The variable
 list/unit is given below:  VARIABLES="X [R]" "Y [R]"
 "Z [R]" " "B_x [nT]" "B_y [nT]"
 "B_z [nT]" Of these variables: * **X [R], Y [R], Z [R]** —
 position in the MSO coordinate system * **B_x [nT], B_y [nT], B_z [nT]** —
 total magnetic field components
 Fig11_n008_rimf_sat_sat2022_12_25_29_sat_n000000_.dat.zip
 **Description:** Satellite files for Fig11 for radial IMF case from the
 MHD model in ascii format. The variable list/unit is included in the
 header of the satellite files, and also given below:
 VARIABLES="it" "Year" "mn" "day"
 "hour" "min" "Sec" "ms" "X
 [R]" "Y [R]" "Z [R]" "r [amu/cm^3]"
 "U_x [km/s]" "U_y [km/s]" "U_z
 [km/s]""B_x [nT]" "B_y [nT]" "B_z [nT]"
 "pe [nPa]" "p [nPa]" "rHp [amu/cm3]"
 "HpU_x [km/s]" "HpU_y [km/s]" "HpU_z [km/s]"
 "HpP [nPa]" "r^O^2^p [amu/cm^3]" "O2pU_x
 [km/s]" "O2pU_y [km/s]" "O2pU_z [km/s]""O2pP
 [nPa]" "rOp [amu/cm3]" "OpU_x [km/s]" "OpU_y
 [km/s]" "OpU_z [km/s]""OpP [nPa]" "r^C^O^2^p
 [amu/cm^3]" "CO2pU_x [km/s]" "CO2pU_y [km/s]"
 "CO2pU_z [km/s]" "CO2pP [nPa]" "B1_x [nT]"
 "B1_y [nT]" "B1_z [nT]" "e" "J_x
 [mA/m2]" "J_y [mA/m^2]" "J_z [mA/m2]" **Of these,
 the variables have the same definitions as those listed in Figures 2–4.**
 ## Code/software The MAVEN data used in this study are available through
 the Planetary Data System
 ([http://ppi.pds.nasa.gov/mission/MAVEN](http://ppi.pds.nasa.gov/mission/MAVEN)). The BATS-R-US code is publicly available at [https://github.com/SWMFsoftware/BATSRUS](https://github.com/SWMFsoftware/BATSRUS).
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