Subsolar Region Research Articles

Observations of the Crustal Mini-magnetopause Reconnection at Mars

Magnetopause reconnection is a fundamental mechanism for mass and energy transfer in terrestrial planetary systems. Unlike Earth, Mars lacks a global magnetic field and instead has localized crustal magnetic fields, which can create structures morphologically similar to a scaled-down intrinsic magnetosphere, potentially forming mini-magnetospheres. In this study, we investigate reconnection in Martian mini-magnetospheres on the dayside, analyzing key characteristics of the reconnecting current sheet, and the associated ion escape rate, and comparing these features to reconnection events at the induced magnetopause documented in previous studies. Our observations reveal that, in the subsolar region, the thickness of the Martian mini-magnetopause is comparable to the upstream proton inertial length and the convective gyroradius of the magnetosheath solar wind. However, at higher solar zenith angles, this thickness increases to several times these characteristic lengths. Reconnection-driven ion escape rates at the induced magnetopause are at least 1 order of magnitude greater than those associated with mini-magnetopause reconnection. These findings provide new insights into reconnection processes at Martian boundary layers.

Magnetic field dynamics and noise analysis for space-based GW detector in far-earth orbits: A hybrid modeling approach

TianQin (TQ) mission, the sole proposed gravitational wave detection project in geocentric orbit at an altitude of approximately 105 km, traverses diverse geomagnetic regions. This paper employs a hybrid model to simulate the ambient magnetic field along the TQ orbit, investigating magnetically-induced acceleration noise under varying satellite-sun angles (SSA) and solar activity levels. The highest noise level, approximately 10−16ms−2Hz−1/2, occurs during transregional periods between the magnetosheath (MSH) and magnetotail (MTL). Noise within the MSH region is an order of magnitude lower than the former, with the MTL region exhibiting the lowest levels, although geomagnetic storms can equalize noise in both regions. Statistical analysis indicates that noise in the MTL region correlates with SSA and solar wind dynamic pressure, displaying a spectral characteristic of f−1.03±0.075, while the MSH region shows a Kolmogorov turbulence spectrum near the flank and f−0.5 at the subsolar region.

MMS Observations of Electron Vorticity in the Earth’s Magnetosheath

The Earth’s magnetosheath serves as a natural laboratory to study the transition of highly turbulent fluctuations. The fundamental information about plasma turbulences can be examined observationally with the help of electron vorticity measurements. This study presents the first statistics of the electron vorticity field in the magnetosheath by utilizing 4 yr data from NASA’s Magnetospheric Multiscale mission. In this study, the magnetosheath vorticity has a dominant perpendicular anisotropy. The vorticity field in the subsolar region is much stronger than that of magnetosheath flanks. Clear dusk-favored asymmetry for large vorticity is identified in the subsolar region. We examine that the electron flow vorticity in the turbulent magnetosheath is well anticorrelated with the electron density. The vorticity is of great importance in energy dissipation and electron heating in the magnetosheath flanks. This study can improve the current understanding of electron vorticity due to its ubiquitous role in space plasma turbulences.

Magnetopause location modeling using machine learning: inaccuracy due to solar wind parameter propagation

An intrinsic limitation of empirical models of the magnetopause location is a predefined magnetopause shape and assumed functional dependences on relevant parameters. We overcome this limitation using a machine learning approach (artificial neural networks), allowing us to incorporate general, purely data-driven dependences. For the training and testing of the developed neural network model, a data set of about 15,000 magnetopause crossings identified in the THEMIS A-E, Magion 4, Geotail, and Interball-1 satellite data in the subsolar region is used. A cylindrical symmetry around the direction of the impinging solar wind is assumed, and solar wind dynamic pressure, interplanetary magnetic field magnitude, cone angle, clock angle, tilt angle, and corrected Dst index are considered as parameters. The effect of these parameters on the magnetopause location is revealed. The performance of the developed model is compared with other empirical magnetopause models. Finally, we demonstrate and discuss the inaccuracy of magnetopause models due to the inaccurate information about the impinging solar wind parameters based on measurements near the L1 point. This inaccuracy imposes a theoretical limit on the precision of magnetopause predictions, a limit that our model closely approaches.

Statistical Observations of Proton‐Band Electromagnetic Ion Cyclotron Waves in the Outer Magnetosphere: Full Wavevector Determination

AbstractElectromagnetic Ion Cyclotron (EMIC) waves mediate energy transfer from the solar wind to the magnetosphere, relativistic electron precipitation, or thermalization of the ring current population, to name a few. How these processes take place depends on the wave properties, such as the wavevector and polarization. However, inferring the wavevector from in‐situ measurements is problematic since one needs to disentangle spatial and time variations. Using 8 years of Magnetospheric Multiscale (MMS) mission observations in the dayside magnetosphere, we present an algorithm to detect proton‐band EMIC waves in the Earth's dayside magnetosphere, and find that they are present roughly 15% of the time. Their normalized frequency presents a dawn‐dusk asymmetry, with waves in the dawn flank magnetosphere having larger frequency than in the dusk, subsolar, and dawn near subsolar region. It is shown that the observations are unstable to the ion cyclotron instability. We obtain the wave polarization and wavevector by comparing Single Value Decomposition and Ampere methods. We observe that for most waves the perpendicular wavenumber (k⊥) is larger than the inverse of the proton gyroradius (ρi), that is, k⊥ρi > 1, while the parallel wavenumber is smaller than the inverse of the ion gyroradius, that is, k‖ρi < 1. Left‐hand polarized waves are associated with small wave normal angles (θBk < 30°), while linearly polarized waves are associated with large wave normal angles (θBk > 30°). This work constitutes, to our knowledge, the first attempt to statistically infer the full wavevector of proton‐band EMIC waves observed in the outer magnetosphere.

Statistical Distribution of Whistler Mode Waves in the Martian Induced Magnetosphere Based on MAVEN Observations

AbstractWhistler mode waves are a common type of electromagnetic waves in the Martian induced magnetosphere. Using high‐resolution magnetic field data from the Magnetometer (MAG) instrument onboard Mars Atmosphere and Volatile Evolution (MAVEN) from October 2014 to November 2022, we perform a detailed analysis of the statistical distribution of the occurrence rate, averaged amplitude, peak frequency, wave normal angle and ellipticity of left‐hand and right‐hand polarized whistler mode waves in the Martian induced magnetosphere. Our results show that whistler mode waves are mainly observed in the subsolar and magnetic pileup region, with the occurrence rate of right‐hand mode waves higher than that of left‐hand mode waves. The averaged wave amplitude ranges from 0.02 to 0.13 nT and peak wave frequency ranges from 2 to 9 Hz. We also find that the wave normal angles for both left‐hand and right‐hand polarized whistler waves are relatively larger in the subsolar region and magnetic pileup region where the corresponding wave ellipticity is closer to the linear polarization. Our results are valuable to in‐depth understanding of the generation mechanism of whistler mode waves as well as their contributions to the electron dynamics in the Martian induced magnetosphere.

Disappearing Solar Wind at Mars: Changes in the Mars‐Solar Wind Interaction

AbstractOn 26 December 2022 the solar wind density dropped by over an order of magnitude and remained low for about a day. We have utilized in‐situ plasma measurements made by the Mars Atmosphere and Volatile EvolutioN mission to determine how this change affected the Mars‐solar wind interaction. During this time period, on inbound orbit segments, MAVEN sampled the terminator ionosphere, which switched from a magnetized to unmagnetized state immediately following the minimum in solar wind density. The magnetic field amplitude was typically 5–10 nT within the upper ionosphere prior to the event and consistently <1 nT after. During the event the magnetic pressure dominated immediately above the ionosphere while within the ionosphere the ionospheric plasma pressure dominated. The high altitude terminator ionosphere remained in this unmagnetized state throughout the event, suggesting that it was the new equilibrium state of the system. The terminator upper ionosphere returned to its original magnetized state once the solar wind density had recovered. The outbound orbit segments sampled the dayside subsolar region which remained magnetized throughout the event: the magnetization state of the ionosphere varied locally, dependent upon the solar zenith angle and corresponding incident solar wind dynamic pressure. Such conditions are different to the commonly reported unmagnetized ionospheric state at Venus during solar maximum conditions, where the interplanetary magnetic field is repelled from the entire dayside ionosphere. Drastic changes in the upstream solar wind are able to change the Mars‐solar wind interaction state on timescales less than one MAVEN orbit (∼3.5 hr).

Variations of the magnetic field and plasma parameters near the Martian induced magnetosphere boundary

The induced magnetosphere boundary (IMB) forms between the Martian magnetosheath and the induced magnetosphere/ionosphere and is important in energy and momentum transport and particle escape at Mars. Based on MAVEN multi-instrument observations in the year 2015, we find the IMBs usually appear with distinct variations of magnetic field and plasma, though they could be disturbed occasionally, especially at large solar zenith angles (SZAs). This study focuses on the properties of the distinct IMBs. The magnetic field strength is enhanced and the magnetic fluctuations are suppressed in IMB. The solar wind particles decrease and the planetary heavy ions start to be dominant in IMB. The variation of plasma is more effective in identifying the IMB's location since it is consistent at all SZAs, while the enhancement of the magnetic field strength or the suppression of the magnetic fluctuations would become ambiguous at large SZAs. The currents in IMB exhibit the signature of field-aligned-like and have larger magnitudes at the subsolar region. The kinetic effect of multiple ion species could be important near IMB. The properties of the Martian IMB investigated here are helpful in identifying this region and understanding the Mars-solar wind interaction and the Martian ionosphere/atm evolution.

Statistical Characteristics of Electron Vortexes in the Terrestrial Magnetosheath

Utilizing the unprecedented high-resolution Magnetospheric Multiscale mission data from 2015 September to 2017 December, we perform a statistical study of electron vortexes in the turbulent terrestrial magnetosheath. On the whole, 506 electron vortex events are successfully selected. Electron vortexes can occur at four known types of magnetic structures, including 78, 42, 26, and 39 electron vortexes observed during the crossings of the current sheets, magnetic holes, magnetic peaks, and flux ropes, respectively. Except for the four types of structures, the rest of the electron vortexes are in the “Others” category, defined as unknown structures. The electron vortexes mainly occur in the subsolar region, with only a few in the flank region. The total occurrence rate of all electron vortexes is 4.86 hr–1, with, on average, 3.65 events hr−1 in the X-Y plane and 3.26 events hr−1 in the X-Z plane. The durations of most of the electron vortexes concentrate within 0.5–1.5 s and are 1.09 s on average. The electron vortexes are ion-scale structures owing to the average scale of 2.05 ion gyroradius. In addition, the means, medians, and maxima of the energy dissipation J · E′ in the electron vortexes are almost positive, implying that the electron vortex may be a potential coherent structure or channel for turbulent energy dissipation. All these results reveal the statistical characteristics of electron vortexes in the magnetosheath and improve our understanding of energy dissipation in astrophysical and space plasmas.

Dense gas and star formation in the outer Milky Way

We present maps and spectra of the HCN(1−0) and HCO+(1−0) lines in the extreme outer Galaxy, at galactocentric radii between 14 and 22 kpc, with the 13.7 m Delingha telescope. The nine molecular clouds were selected from a CO/13CO survey of the outer quadrants. The goal is to better understand the structure of molecular clouds in these poorly studied subsolar metallicity regions and the relation with star formation. The lines are all narrow, less than 2 km s−1 at half power, enabling the detection of the HCN hyperfine structure in the stronger sources and allowing us to observationally test hyperfine collision rates. The hyperfine line ratios show that the HCN emission is optically thin with column densities estimated at N(HCN) ≈ 3 × 1012 cm−2. The HCO+ emission is approximately twice as strong as the HCN (taken as the sum of all components), in contrast with the inner Galaxy and nearby galaxies where they are similarly strong. For an abundance ratio χHCN/χHCO+ = 3, this requires a relatively low-density solution for the dense gas, with n(H2) ~ 103−104 cm−3. The 12CO/13CO line ratios are similar to solar neighborhood values, which are roughly 7.5, despite the low 13CO abundance expected at such large radii. The HCO+/CO and HCO+/13CO integrated intensity ratios are also standard at about 1/35 and one-fifth, respectively. The HCN is weak compared to the CO emission, with HCN/CO ~ 1 /70 even after summing all hyperfine components. In low-metallicity galaxies, the HCN deficit is attributed to a low [N/O] abundance ratio; however, in the outer disk clouds, it may also be due to a low-volume density. At the parsec scales observed here, the correlation between star formation, as traced by 24 μm emission as is standard in extragalactic work, and dense gas via the HCN or HCO+ emission is poor, perhaps due to the lack of dynamic range. We find that the lowest dense gas fractions are in the sources at high galactic latitude (b > 2°, h ≳ 300 pc above the plane), possibly due to lower pressure.

Interplanetary Magnetic Field Effect on the Location of the Martian Bow Shock: MAVEN Observations

The Martian bow shock (BS) is generated with the mass-loading and magnetic pileup processes when the solar wind interacts with the Martian ionosphere. In this vein, the interplanetary magnetic field (IMF) frozen in the solar wind can affect the location of the Martian BS, which is less reported. Based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, we manually identify 10,283 BS crossings during a period of the gradually declining solar cycle phase (2014 October–2020 December) and investigate the effects of the intensity and orientation of the IMF on the Martian BS. In the Mars Solar Orbital coordinate system, our results show the following: (1) The Martian BS, including the subsolar and flank regions, linearly moves away from Mars when the IMF intensity increases, which confirms the theoretical and the MHD simulation results. (2) Under the radial IMF condition, we first demonstrate that the subsolar and flank regions of the Martian BS are situated closer to Mars compared to other IMF situations. This might be caused by the weaker magnetic pileup process and the “low-pressure magnetosheath” model under the radial IMF condition. (3) Moreover, the cross section of the Martian BS is elongated in the north–south direction when the Y component of the IMF is dominant, which is on account of the fast magnetosonic speed effect and verifies the elongation phenomenon of the terrestrial BS. The IMF intensity and orientation effects cannot be ignored and should be considered in future models of the Martian BS.

Ion-Scale Magnetic Flux Rope Generated From Electron-Scale Magnetopause Current Sheet: Magnetospheric Multiscale Observations.

We present in-depth analysis of three southward-moving meso-scale (ion-to magnetohydrodynamic-scale) flux transfer events (FTEs) and subsequent crossing of a reconnecting magnetopause current sheet (MPCS), which were observed on 8 December 2015 by the Magnetospheric Multiscale spacecraft in the subsolar region under southward and duskward magnetosheath magnetic field conditions. We aim to understand the generation mechanism of ion-scale magnetic flux ropes (ISFRs) and to reveal causal relationship among magnetic field structures, electromagnetic energy conversion, and kinetic processes in magnetic reconnection layers. Results from magnetic field reconstruction methods are consistent with a flux rope with a length of about one ion inertial length growing from an electron-scale current sheet (ECS) in the MPCS, supporting the idea that ISFRs can be generated through secondary reconnection in an ECS. Grad-Shafranov reconstruction applied to the three FTEs shows that the FTEs had axial orientations similar to that of the ISFR. This suggests that these FTEs also formed through the same secondary reconnection process, rather than multiple X-line reconnection at spatially separated locations. Four-spacecraft observations of electron pitch-angle distributions and energy conversion rate suggest that the ISFR had three-dimensional magnetic topology and secondary reconnection was patchy or bursty. Previously reported positive and negative values of , with magnitudes much larger than expected for typical MP reconnection, were seen in both magnetosheath and magnetospheric separatrix regions of the ISFR. Many of them coexisted with bi-directional electron beams and intense electric field fluctuations around the electron gyrofrequency, consistent with their origin in separatrix activities.

Effects of Force in the Martian Plasma Environment With Solar Wind Dynamic Pressure Enhancement

AbstractDisturbed solar wind dynamic pressure is one of the important external drivers which could cause significant impacts on Martian plasma environment. In this study, a 3D multifluid multispecies numerical model is established to simulate the interaction between solar wind and Mars. Functions of electromagnetic forces applied on different ion species were analyzed. We found that the total electromagnetic force peaks near bow shock (BS) and magnetic pileup boundary (MPB) with clear asymmetry features, acting to decelerate solar wind plasma across boundary layers, and compresses heavy ions toward the planet inside the MPB. For solar wind protons, electron pressure gradient force dominates near BS and Hall electric field force dominates near MPB, controlling the location of plasma boundary. Furthermore, the morphology of motional electric field force shows clear north‐south asymmetry, leading to the formation of asymmetric structures and plasma flow in Martian space environment. The response of BS, MPB to a solar wind dynamic pressure enhancement event, as well as the effects of electromagnetic forces in this process are also investigated. After the arrival of solar wind pulse, the magnitudes of electromagnetic forces increased simultaneously to balance the enhanced solar wind dynamic pressure, while the peaks of forces moved inward with BS and MPB. The magnitudes and peaks of ion velocity in subsolar region show similar variations as well, with the greater enhancement of forces leading to the greater increase of ion velocities, indicating that the changes of forces influence boundary layers through the variation of plasma speed.

BepiColombo mission confirms stagnation region of Venus and reveals its large extent

The second Venus flyby of the BepiColombo mission offer a unique opportunity to make a complete tour of one of the few gas-dynamics dominated interaction regions between the supersonic solar wind and a Solar System object. The spacecraft pass through the full Venusian magnetosheath following the plasma streamlines, and cross the subsolar stagnation region during very stable solar wind conditions as observed upstream by the neighboring Solar Orbiter mission. These rare multipoint synergistic observations and stable conditions experimentally confirm what was previously predicted for the barely-explored stagnation region close to solar minimum. Here, we show that this region has a large extend, up to an altitude of 1900 km, and the estimated low energy transfer near the subsolar point confirm that the atmosphere of Venus, despite being non-magnetized and less conductive due to lower ultraviolet flux at solar minimum, is capable of withstanding the solar wind under low dynamic pressure.

Storm‐Time Magnetopause: Pressure Balance

AbstractThe magnetopause is treated as a boundary where the pressure of the incoming solar wind is balanced by the pressure of the geomagnetic field and the plasma pressure inside the magnetopause is often neglected. However, published studies of pressure balance at the magnetopause reveal an excess of the magnetosheath pressure. Moreover, our survey of about 50,000 THEMIS magnetopause crossings shows that about 1% of them exhibits even larger magnetic field in the magnetosheath than in the magnetosphere. A subsequent analysis of crossings observed in the subsolar region under a southward interplanetary magnetic field shows the pressure of the dense cold ion population as an important component of the total magnetospheric pressure. This component is too cold to be registered by standard ion analyzers but its density can reach 300 cm−3. The second effect connected with a presence of cold plasma population is a reduction of the reconnection rate that slows down the transport of the magnetic flux down the tail and leads to magnetic pile‐up in the subsolar magnetosheath.

A magnetohydrodynamic simulation of the dayside magnetic reconnection between the solar wind and the Martian crustal field

Using a three-dimensional multispecies magnetohydrodynamic model, we study the effects of the orientation of the interplanetary magnetic field (IMF), solar wind dynamic pressure (Pd), and the location of the intense crustal field, on the dayside magnetic reconnection between the solar wind and the Martian crustal field. Our main results are as follows: (1) Different IMF orientations result in different magnetic field configurations and reconnection conditions on the Martian dayside. When the intense crustal field is located on the dayside, the dayside magnetic reconnection tends to occur in the region with solar zenith angles (SZA) ≈45° in the southern hemisphere for the IMF with a southward component. When the IMF has a northward component, the magnetic field lines are piled up in the same place and the Martian magnetic pileup boundary (MPB) appears as a local bulged “mini-magnetopause”. Under the pure radial IMF, the magnetic reconnection is absent, which might be due to the presence of additional outward magnetic tension and kinetic effects. (2) Dayside reconnection can change the shape of the Martian MPB, while the bow shock is weakly affected. When the IMF has a southward component, the dayside magnetic reconnection happens and the MPB is located closer to Mars with a “cusp” shape. When the IMF has a northward component, the Martian MPB expands with a local bulged “mini-magnetopause”. For the pure radial IMF condition, the subsolar region of the MPB is located closer to Mars than that under other IMF directions. The influence of the IMF cone angles on the Martian bow shock is much less than that on the MPB, and the bow shock locations are very close to the model results of another author found in the literature. (3) With increasing Pd, the size of the crustal field region decreases and the draped fields correspondingly move to lower altitudes where the IMF and crustal field have the same direction. When the IMF has a southward component and the magnetic reconnection occurs at SZA ≈ 45°, the reconnection site, the region of the closed topology of the crustal field, and the draped IMF, do not change much with increasing Pd. We suggest that the multipolar crustal magnetic fields can protect the solar wind IMF from further reconnecting with the crustal field to a lower altitude when Pd is enhanced.

The siphonic energy transfer between hot solar wind and cold martian ionosphere through open magnetic flux rope

A mechanism for energy transfer from the solar wind to the Martian ionosphere through open magnetic flux rope is proposed based on the observations by Mars Atmosphere and Volatile EvolutioN (MAVEN). The satellite was located in the dayside magnetosheath at an altitude of about 700 km above the northern hemisphere. Collisions between the hot solar wind protons and the cold heavy ions/neutrals in the subsolar region can cool the protons and heat the heavy ions. As a result, the magnetosheath protons are siphoned into the ionosphere due to the thermal pressure gradient of protons and the heated heavy ions escape along the open magnetic field lines. Although direct collisions in the lower-altitude region were not detected, this physical process is demonstrated by MAVEN measurements of enhanced proton density, decreased proton temperature and oppositely directed motions of hot and cool protons within the flux rope, which are very different from the observational features of the flux transfer events near the Earth’s magnetopause. This mechanism could universally exist in many contexts where a collisionless plasma region is connected to a collisional plasma region. By reconstructing the magnetic geometry and the cross-section of the flux rope using the Grad-Shafranov technique, the ion loss rates are quantitatively estimated to be on the order of 1023 s−1, which is much higher than previously estimated.

Overshoot Structure Near the Earth’s Subsolar Magnetopause Generated by Magnetopause Motions

For magnetopause crossing events, the observed magnetospheric magnetic fields in the vicinity of the subsolar magnetopause frequently present an overshoot structure; that is, in small vicinity of the magnetopause, the closer to the magnetopause, the stronger the magnetospheric magnetic field is. In this investigation, an automatic identification algorithm is developed to rapidly and effectively search the magnetopause crossing events using THEMIS data from 2007 to 2021. Nearly 59% of magnetopause crossing events identified near the subsolar region appear an overshoot structure. The statistical result shows that, for overshoot cases, the normalized change rate of magnetospheric magnetic field near the magnetopause is linearly related to the normalized magnetopause velocity, which means that the overshoot structure may be caused by the redistribution of the magnetospheric magnetic field due to the rapid magnetopause motion.

Photoelectron Butterfly Pitch-angle Distributions in the Martian Ionosphere Based on MAVEN Observations

Using pitch-angle-resolved electron fluxes recorded by the Mars Atmosphere and Volatile Evolution spacecraft over 5 yr, we present a detailed analysis of the occurrence patterns of photoelectron butterfly pitch-angle distributions (PADs) in the Martian ionosphere. Statistical analysis indicates that Martian photoelectron butterfly PADs favorably occur near the moderate crustal magnetic fields with a strength of 10–30 nT on the dayside and 10–15 nT on the nightside. The nightside occurrence rates are much higher. Furthermore, dayside butterfly PADs prefer to occur near the vertical magnetic field lines in the ionosphere, and the significant day-to-night transport of photoelectrons evades the nightside strongest magnetic anomaly regions. These features strongly support the idea that Martian photoelectron butterfly PADs are more likely to occur in eclipse or near the terminator and that they mainly form due to the adiabatic evolution of photoelectrons that transport along the closed cross-terminator magnetic field lines. Despite the negligible energy dependence in the darkness, the occurrence rate of dayside butterfly PADs observed at higher altitudes and near the subsolar region increases with energy, presumably related to the increased proportion of electrons from the solar wind when measured at relatively higher electron energies, which, however, is limitedly understood and deserves future investigation. Our comprehensive observations suggest the diverse influence of Martian magnetic topology on the ionospheric plasma in different spatial regions, and, in turn, analysis of their influence allows us a better understanding of the intricate Martian global magnetic system.

A Case Study of the Induced Magnetosphere Boundary at the Martian Subsolar Region

Abstract One Martian induced magnetosphere boundary (IMB) crossing at the subsolar region is analyzed here with multiple instruments on board MAVEN. Properties of the magnetic field and particles around the IMB are evaluated. We find different trends of variation in magnetic field components at the two sides of an interface coincident with the previously defined ion composition boundary. This case shows the IMB at the Martian dayside could be divided into three parts: two regions (denoted as R1 and R2), with different field and plasma properties, and an interface between them. Currents found in R1 and R2 are flowing in antiparallel, and the current density in R2 (at lower altitude) is significantly larger than that in R1 (at higher altitude). Results indicate the interaction between Mars and the solar wind could induce strong currents in the IMB, which are with antiparallel current directions and separated by an interface where the ion composition changes. This could be a typical feature that occurred during the interaction between the solar wind and the nonmagnetized planets.