Stable Solar Wind Research Articles

Exergy and Energy Analysis of Hydrogen Production Using Electrolysis Process Powered by Wind and Solar Energy

This study examines hydrogen production using a hybrid renewable energy system combining wind and solar energy sources. The experiment was conducted over four days, with data collected from 9:00 AM to 3:00 PM each day, focusing on solar irradiance, wind speed, and the energy and exergy efficiencies of each component—wind turbine, photovoltaic (PV) panel, and electrolyzer. Solar irradiance varied across the days, peaking at 160 W/m² but experiencing fluctuations due to weather conditions, while wind speeds ranged between 0 and 6 m/s, with the highest consistency observed on Day 3. Each component’s performance was measured by energy and exergy efficiency metrics, which revealed significant differences across the four days. The turbine’s energy efficiency ranged from 3.83% to 8.24%, with exergy efficiency slightly lower, indicating mechanical and aerodynamic losses. Solar panel energy efficiency varied from 13.42% to 22.92%, impacted by irradiance stability, while the electrolyzer consistently showed high energy efficiency, between 59.06% and 63.42%, with exergy efficiency slightly lower. Total system efficiency ranged from 43.09% to 65.30% for energy and 24.23% to 35.35% for exergy. Hydrogen production peaked on Day 1 and Day 2, reaching approximately 6000 mL, due to either stable solar or moderate wind input. Day 3, despite optimal wind speeds, produced slightly less hydrogen (5800 mL) due to limited solar input. Production on Day 4 was lowest (5000 mL), affected by high variability in both wind and solar conditions. The results demonstrate that stable solar and wind inputs are essential for maximizing hydrogen production. High variability in energy inputs leads to reduced efficiency, highlighting the importance of reliable renewable sources or energy storage solutions. Future work could focus on optimizing the exergy efficiency of each component to further improve hydrogen production and reduce energy losses, making the system more resilient and efficient for sustainable energy applications.

Does Reconnection Only Occur at Points of Maximum Shear on Mercury's Dayside Magnetopause?

AbstractMESSENGER observations of large numbers of flux transfer events (FTEs) during dayside crossings of Mercury's magnetopause have shown that the highly dynamic Hermean magnetosphere is strongly driven by frequent and intense magnetic reconnection. Since FTEs are products of reconnection, study of them can reveal information about whether reconnection sites favor points of maximum shear on the magnetopause. Here, we analyze 201 FTEs formed under relatively stable upstream solar wind conditions as observed by MESSENGER during inbound magnetopause crossings. By modeling paths of these FTEs along the magnetopause, we determine the conditions and locations of the reconnection sites at which these FTEs were likely formed. The majority of these FTE formation paths were found to intersect with high‐magnetic shear regions, defined as shear angles above 135°. Seven FTEs were found where the maximum shear angle possible between the reconnecting magnetic field lines was less than 80° and three of these had shear angles less than 70°, supporting the idea that very low‐shear reconnection could be occurring on Mercury's dayside magnetopause under this global‐scale picture of magnetic reconnection. Additionally, for the FTEs formed under these low‐shear reconnection conditions, tracing a dominant X‐line connecting points of maximum shear along the magnetopause that passes through a region of very low‐shear may be difficult to justify, implying reconnection could be occurring anywhere along Mercury's magnetopause and may not be confined to points of maximum shear.

The Relationship between Solar Wind Charge Exchange Soft X-ray Emission and the Tangent Direction of Magnetopause in an XMM–Newton Event

With the advent of soft X-ray imaging enabling global magnetopause detection, it is critical to use reconstruction techniques to derive the 3-dimensional magnetopause location from 2-dimensional X-ray images. One of the important assumptions adopted by most techniques is that the direction with maximum soft X-ray emission is the tangent direction of the magnetopause, which has not been validated in observation so far. This paper analyzes a magnetospheric solar wind charge exchange (SWCX) soft X-ray event detected by XMM–Newton during relatively stable solar wind and geomagnetic conditions. The tangent direction of the magnetopause is determined by an empirical magnetopause model. Observation results show that the maximum SWCX soft X-ray intensity gradient tends to be the tangent of the magnetopause’s inner boundary, while the maximum SWCX soft X-ray intensity tends to be the tangent of the magnetopause’s outer boundary. Therefore, it is credible to use the assumption that the tangent direction of the magnetopause is the maximum SWCX soft X-ray intensity or its gradient when reconstructing the 3-dimensional magnetopause location. In addition, since these two maxima tend to be the inner and outer boundaries of the magnetopause, the thickness of magnetopause can also be revealed by soft X-ray imaging.

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.

Longitudinal Evolution of Storm-Enhanced Densities: A Case Study

Due to the limitations on observational data, most storm-enhanced density (SED) studies have focused on the North American sector. The complete picture of the longitudinal evolution of SEDs is still not clear. In this study, we investigated the dynamic evolution of SEDs from the European sector to the North American sector during a geomagnetic storm that occurred on the 15 July 2012, the main phase of which lasted nearly 30 h, maintaining the stable interplanetary magnetic field (IMF) and solar wind input conditions. Multiple data sets were analyzed, including convection data from the Super Dual Auroral Radar Network (SuperDARN), total electron contents (TECs) from the Madrigal database, plasma data from the Millstone Hill incoherent scatter radar (MHISR), solar wind and geomagnetic indices from OMNIWeb, and regional auroral electrojet indices from SuperMAG. The observations showed that the positions of SEDs shifted from local noon over the European sector towards dusk over the American sector and simultaneously moved to lower latitudes. The peak values of SED TECs were found to be greater in the European sector and to decrease with universal time. A double SED phenomenon appeared in the North American sector, which is the first of its kind to be reported. Further analysis showed that the temporal and spatial changes in the SEDs were associated with the eastward auroral electrojet.

In Situ Observation of Solar-flare-induced Proton Cyclotron Waves Upstream from Mars

Proton cyclotron waves (PCWs) upstream from Mars are usually interpreted as waves generated by ion/ion instabilities due to the interaction between the solar wind plasma and the pickup protons, originating from the extended hydrogen (H) exosphere of Mars. Their generation mainly depends on the solar wind properties and the relative density of the newborn protons with respect to the background solar wind. Under stable solar wind conditions, a higher solar irradiance leads to both increased exospheric H density and ionization rate of H atoms, and therefore a higher relative density, which tends to increase the linear wave growth rate. Here we show that the solar irradiance is likely to contribute significantly to PCW generation. Specifically, we present observations from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft indicating that, around the peak of the X8.2 flare on 2017 September 10, the increased solar irradiance gave rise to higher pickup H+ fluxes, which in turn excited PCWs. This result has implications for inferring the loss of hydrogen to space in early Martian history with more intense and frequent X-class flares as well as their contributions to the total loss.

Proton cyclotron and mirror instabilities in marginally stable solar wind plasma

ABSTRACT This paper formulates a velocity moment-based quasi-linear theory that combines the impacts of weakly unstable proton–cyclotron- (or, equivalently, electromagnetic ion cyclotron) and proton-mirror instabilities on the solar wind plasma initially characterized by an excessive perpendicular proton temperature anisotropy. The present formalism is an alternative to the existing model in that the weakly unstable modes are characterized by analytical formalism that involves the assumption of weak growth rate and/or fluid-theoretical dispersion relation, in place of numerical root-finding method based on the transcendental plasma dispersion function. This results in an efficient numerical platform for analyzing the quasi-linear development of the said instabilities. Such a formalism may be useful in the larger context of global solar wind modelling effort where an efficient calculation of self-consistent wave–particle interaction process is called for. A direct comparison with spacecraft observations of solar wind proton data distribution shows that the present weak growth rate formalism of quasi-linear calculation produces results that are consistent with the observation.

Characteristics of the Heliospheric Current Sheets at the Sector Boundaries: Wind Observations from 1995–2020

Abstract We report results of a statistical study of 1197 heliospheric current sheet (HCS) events associated with the sector boundaries observed by the Wind spacecraft between 1995 and 2020. The average property of the HCS events can be characterized as follows: (1) The width of the current sheets ranges between ∼600 km and 1.1 × 106 km, with an average width of 1.06 ± 2.37 × 105 km; (2) The longitude (in Geocentric Solar-Ecliptic coordinate) of the HCS normal shows a large peak at ∼210° (0° sunward pointing) and a longer tail at smaller angles; (3) The latitudinal angle (inclination) of the HCS normal shows a near symmetric distribution (peak and average ∼0°); (4) The yearly occurrence rate is relatively constant (∼46 or 3.4 events per solar rotation), without showing a clear solar cycle dependence; (5) There are solar cycle variations in the properties of the plasma and field within the current sheets and these variations follow closely with the background solar wind plasma and field; (6) A mild (∼10%) proton temperature increase within the HCS, suggesting that heating of the solar wind proton can occur within the current sheet; and (7) A sudden decrease in the proton temperature anisotropy (T ∥/T ⊥) toward unity within ∼3 hr of the HCS was identified. These results suggest that on the large scale the HCS at 1 au is a relatively stable and persistent solar wind structure throughout the solar cycle. On the small scale the HCS property is probably controlled by the dynamics of the current system, which is still poorly known.

Interhemispheric Conjugacy of Concurrent Onset and Poleward Traveling Geomagnetic Responses for Throat Aurora Observed Under Quiet Solar Wind Conditions

AbstractThroat auroras frequently observed near local noon have been confirmed to correspond to magnetopause indentations, but the generation mechanisms for these indentations and the detailed properties of throat aurora are both not fully understood. Using all‐sky camera and magnetometer observations, we reported some new observational features of throat aurora as follows. (1) Throat auroras can occur under stable solar wind conditions and cause clear geomagnetic responses. (2) These geomagnetic responses can be simultaneously observed at conjugate geomagnetic meridian chains in the Northern and Southern Hemispheres. (3) The initial geomagnetic responses of throat aurora show concurrent onsets that were observed at all stations along the meridians. (4) Immediately after the concurrent onsets, poleward moving signatures and micropositive bays were observed in the X components at higher‐ and lower‐latitude stations, respectively. We argue that these observations provide evidence for throat aurora being generated by low‐latitude magnetopause reconnection. We suggest that the concurrent onsets reflect the instantaneous responses of the reconnection signal arriving at the ionosphere, the followed poleward moving signatures reflect the antisunward dragging of the footprint of newly opened field lines, and the micropositive bays may result from a pair of field‐aligned currents generated during the reconnection. This study may shed new light on the geomagnetic transients observed at cusp latitude near magnetic local noon.

The 18 November 2015 Magnetopause Crossing: The GEM Dayside Kinetic Challenge Event Observed by MMS/HPCA

AbstractAt Earth's dayside magnetopause, the fundamental process known as magnetic reconnection is responsible for connecting geomagnetic field lines to interplanetary magnetic field lines and converting magnetic energy into particle energy and heat. As part of a coordinated analysis effort by the Geospace Environment Modeling (GEM) community to determine the reconnection location and other aspects of reconnection, a magnetopause crossing by the Magnetospheric Multiscale (MMS) mission on 18 November 2015 was selected. The crossing occurred during stable solar wind and dominantly southward interplanetary magnetic field conditions. The MMS satellites were located close to the subsolar region and observed southward accelerated ion jets during encounters with the magnetopause boundary layers, indicating the presence of an active X‐line north of the satellites. Using proton distributions from the Hot Plasma Composition Analyzer (HPCA) instruments, the distance from the spacecraft to the reconnection site was initially determined to be between 5 to 7 RE. A slight rotation of the interplanetary magnetic field caused a change of the magnetic topology at the magnetopause. This topology change produced conditions which are known to change the location of the X‐line. After the change, the location of the component reconnection line was estimated to be less than 4 RE, but most likely was much closer to the observing satellites.

Upstream Ultra‐Low Frequency Waves Observed by MESSENGER's Magnetometer: Implications for Particle Acceleration at Mercury's Bow Shock

AbstractWe perform the first statistical analysis of the main properties of waves observed in the 0.05–0.41 Hz frequency range in the Hermean foreshock by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Magnetometer. Although we find similar polarization properties to the “30 s” waves observed at the Earth's foreshock, the normalized wave amplitude (δB/|B0|∼0.2) and occurrence rate (∼0.5%) are much smaller. This could be associated with relatively lower backstreaming proton fluxes, the smaller foreshock size and/or less stable solar wind (SW) conditions around Mercury. Furthermore, we estimate that the speed of resonant backstreaming protons in the SW reference frame (likely source for these waves) ranges between 0.95 and 2.6 times the SW speed. The closeness between this range and what is observed at other planetary foreshocks suggests that similar acceleration processes are responsible for this energetic population and might be present in the shocks of exoplanets.

Multi-satellite observations of energy transport during an intense geomagnetic storm

Energy transport during a geomagnetic substorm is a very important process for solar wind-magnetosphere energy coupling and the energy cycle in the magnetotail. In this paper, we use magnetotail data from the five THEMIS probes and two Cluster satellites on the dayside to investigate the energy transport of one intense storm during the period from 08 March to 11 March 2008 at large spatial-temporal scales. Simultaneous observations of the five THEMIS probes indicate that there is a stronger and earlier duskward energy flux density in the near-Earth magnetotail than that in the mid-tail in the initial phase. Low energy particles inject earthward from the dusk flank. Stronger and more variable earthward energy flux density is observed in the mid-tail compared to that near Earth in the main phase; mainly caused by high-speed flow. Tailward energy flux was observed in the near-Earth and mid-tail regions during the recovery phase. Dayside data observed by two Cluster satellites show that the duskward energy flux may be related to stable solar wind input. Tailward energy flux on the dayside should experience some energy conversion process in the magnetotail before it can provide the earthward energy flux in the magnetotail for this intense storm. The strongest energy transport observed by the nightside probes occurs in the main phase. However, the strongest energy measured by the dayside satellites is in the recovery phase without intense activities, two hours later. Different features of the energy transport in the three phases of the storm may be closely related to the different physical processes such as the energy entry, westward drift, particle injection or other potential mechanisms.

Cyclic reformation of a quasi‐parallel bow shock at Mercury: MESSENGER observations

AbstractWe here document with magnetic field observations a passage of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft through Mercury's magnetosphere under conditions of a quasi‐parallel bow shock, i.e., when the direction of the upstream interplanetary magnetic field was within 45° of the bow shock normal. The spacecraft's fast transition of the magnetosheath and the steady solar wind conditions during the period analyzed allow both spatial and temporal properties of the shock crossing to be investigated. The observations show that the shock reformation process can be nearly periodic under stable solar wind conditions. Throughout the 25‐min‐long observation period, the pulsation duration deviated by at most ~10% from the average 10 s period measured. This quasiperiodicity allows us to study all aspects of the shock reconfiguration, including ultra‐low‐frequency waves in the upstream region and large‐amplitude magnetic structures observed in the vicinity of the magnetosheath‐solar wind transition region and inside the magnetosheath. We also show that bow shock reformation can be a substantial source of wave activity in the magnetosphere, on this occasion having given rise to oscillations in the magnetic field with peak‐to‐peak amplitudes of 40–50 nT over large parts of the dayside magnetosphere. The clean and cyclic behavior observed throughout the magnetosphere, the magnetosheath, and the upstream region indicates that the subsolar region was primarily influenced by a cyclic reformation of the shock front, rather than by a spatial and temporal patchwork of short large‐amplitude magnetic structures, as is generally the case at the terrestrial bow shock under quasi‐parallel conditions.

Dynamic modeling of cusp ion structures

Dispersed ion structures observed near the magnetosphere cusps have long been used to infer locations and properties of reconnection at the Earth's magnetopause. However, observations are often difficult to interpret since spacecraft move relative to a cusp ion structure, creating temporal and spatial ambiguity in the observations. Models of cusp ion structures are also limited to the cases during stable solar wind and interplanetary magnetic field (IMF) because empirical models are used to obtain the Earth's electromagnetic fields. We introduce a new model of a cusp ion structure by using the Liouville theorem particle tracer (LTPT) with the OpenGGCM 3D global MHD model. The OpenGGCM produces time‐dependent magnetospheric electromagnetic fields under various solar wind and IMF conditions, while the LTPT traces test particles backward from an observation point to the magnetosheath to map the phase space density and construct an energy‐time spectrogram. This allows our model to study cusp ion structures under dynamic solar wind and IMF conditions. In this paper, we first test our model's capability by reconstructing the cusp ion structures observed from three cusp‐crossing events of Cluster and Polar satellites. We show that the model reproduces various observed ion structures, such as normal dispersion, reverse dispersion, double dispersions, and stepped dispersion. We then show that the cusp structures observed by Cluster on 23 September 2004 and on 23 August 2003 are temporal structures caused by a sudden increase of solar wind dynamic pressure and various reconnection rates, respectively. We also show that the stepped dispersion observed by Polar on 25 August 1998 is not only spatial but also temporal, caused by two different subsolar reconnection sites during a change of the IMF clock angle. In addition, we find that the ions entering the cusp often cross the magnetopause far away from the reconnection site, even though the reconnection is the cause of precipitation, and that the magnetic configuration of the magnetosheath is also sometimes a cause of energy dispersion in a cusp structure.

Frequency fluctuation of spacecraft radio signals in the circumsolar plasma

Frequency fluctuation data of monochromatic radio waves propagating through the circumsolar plasma in 1975–2002 are systematized and analyzed. The radial dependences of the intensity of the frequency fluctuations are obtained for the decimeter radio waves in the circumsolar plasma from the results of radio sounding using the Ulysses and Galileo spacecrafts. It is demonstrated that the radial profile of the rms frequency fluctuations can be approximated by a power-law function whose exponent is determined by the intensity of the plasma inhomogeneities, the velocity of solar wind, the spectral index of the spatial spectrum of the plasma fluctuations, and the outer scale of turbulence. It is also shown that three different frequency fluctuation regimes are found in the solar wind acceleration region and in the inner and outer regions of the stable solar wind.

Rice Convection Model simulation of the 18 April 2002 sawtooth event and evidence for interchange instability

We present the results of a Rice Convection Model (RCM) simulation of the 18 April 2002 sawtooth event. This event occurred as a series of quasi‐periodic substorms during fairly stable solar wind conditions. It is modeled by (1) prescribing a solar‐wind‐driven magnetic field model (T01_s) augmented by additional current loops representing the magnetic effects of the substorm current wedge and (2) by carefully specifying a substorm‐phase‐dependent plasma distribution at the RCM outer boundary at 8 Re such that a hot and attenuated plasma distribution is used after every substorm onset. The set of input parameters was adjusted to make the simulation results agree with the primary signatures of the sawtooth event, specifically the sequence of magnetic field stretching and dipolarization observed by the GOES spacecraft and the associated sharp increases and gradual decreases in the flux of energetic protons measured by the LANL/Synchronous Orbit Plasma Analyzer (SOPA) instruments on other geosynchronous spacecrafts. The results suggest the important role that higher temperature and lower density plasma‐sheet plasma plays in producing flux enhancements at geosynchronous orbit. The results also confirm that induction electric fields associated with magnetic field collapse after substorm onsets can serve as a likely mechanism for the energization of particles up to 25 keV. Synthetic high‐energy neutral atom images are compared with IMAGE/HENA measurements for 10–60 keV hydrogen atoms. Magnetic field dipolarization over a large range of local time resulted in a dramatic reduction in the plasma entropy parameter PV5/3 on the boundary. The simulation indicates that the ring current intensified 10–20 minutes after every onset, associated with the injection of low PV5/3 flux tubes through the boundary. The low PV5/3 plasma also produced an interchange convection in the inner magnetosphere, which drives Birkeland currents in a quasi‐periodic upward‐downward pattern with a lifetime of 40–60 minutes and spatial extent of 1.5–2.0 hours. The results suggest that the spatial quasi‐periodic and nearly north–south‐aligned auroral arcs observed by an IMAGE/FUV WIC detector might be caused by interchange instability.

IPS tomographic observations of 3D solar wind structure

Interplanetary scintillation (IPS) observations have been improved by development of deconvolution methods for the line-of-sight integration effect. One deconvolution method is to use a computer-assisted tomographic analysis (CAT) technique. In this work, four different kinds of CAT method have been developed. Two of them can be applied to stable solar wind structure in the solar minimum phase, one to quasi-stable solar wind, and the other can derive the three-dimensional structure of transient solar wind events, such as a CME. IPS measurements have enough spatial resolution and accuracy to collaborate with spacecraft observations and theoretical studies of the solar wind. Here, these computer assisted tomographic deconvolution methods are introduced and their application to solar wind studies is described.

Resolving the enigmatic solar wind disappearance event of 11 May 1999

On 11 and 12 May 1999, the Earth was engulfed by an unusually low‐density (<1 cm−3) and low‐velocity (<350 km s−1) solar wind for a period of over 1 day. Extensive studies of this unusual event that occurred during Carrington rotation 1949 (CR1949), using both ground‐based and space‐based in situ observations, have not as yet been able to identify the cause or the solar source of this event. Using solar wind velocity measurements from the four‐station IPS observatory of the Solar‐Terrestrial Environment Laboratory (STEL), Toyokawa, Japan, we investigate the structure of the solar wind in May 1999 during CR1949. IPS observations from STEL were used to make tomographic velocity maps to identify and delineate the extent and morphology of the stable solar wind flows during CR1949 in the vicinity of the Earth. Combined with in situ measurements of the interplanetary magnetic field (IMF), potential field computations of the solar magnetic fields in the period, and HeI 10830Å observations of coronal hole boundaries during CR1949, we have identified the source region of the unusual flows and have shown that the flow responsible for the “disappearance event” was a stable unipolar flow originating in the vicinity of a large midlatitude active region AR8525, located at ∼18°N and between heliographic longitudes 280° and 300°. Earlier workers have speculated that such events may be caused by the large‐scale restructuring of the solar magnetic field at the maximum of each solar cycle. However, by identifying the solar source and nature of this event, we believe that at least in this particular case, the association with global, large‐scale solar phenomena like the periodic 11‐year solar polar field reversal is most likely to be coincidental.

Spatial and Temporal Cusp Structures Observed by Multiple Spacecraft and Ground Based Observations

Downward precipitating ions in the cusp regularly exhibit sudden changes in ion energy distributions, forming distinctive structures that can be used to study the temporal/spatial nature of reconnection at the magnetopause. When observed simultaneously with the Polar, FAST, and Interball satellites, such cusp structures revealed remarkably similar features. These similar features could be observed for up to several hours during stable solar wind conditions. Their similarities led to the conclusion that large-scale cusp structures are spatial structures related to global ionospheric convection patterns created by magnetic merging and not the result of temporal variations in reconnection parameters. The launch of the Cluster fleet allows cusp structures to be studied in great detail and during changing solar wind conditions using three spacecraft with identical plasma and field instrumentation. In addition, Cluster cusp measurements are linked with ionospheric convection cells by combining the satellite observations with SuperDARN radar observations that are used to derive the convection patterns in the ionosphere. The combination of satellite observations with ground-based observations during variable solar wind conditions shows that large-scale cusp structures can be either spatial or temporal. Cusp structures can be described as spatial features observed by satellites crossing into spatially separated flux tubes. Cusp structures can also be observed as poleward-traveling (temporal) features within the same convection cell, most probably caused by variations in the reconnection rate at the magnetopause.

Plasma depletion layer: the role of the slow mode waves

Abstract. The plasma depletion layer (PDL) is a layer on the sunward side of the magnetopause with lower plasma density and higher magnetic field compared to their corresponding values in the upstream magnetosheath. The depletion layer usually occurs during northward (IMF) conditions with low magnetic shear across the magnetopause. We have previously validated the Raeder global model by comparing the computed formation of a magnetosheath density depletion with in-situ observations. We also have performed a detailed force analysis and found the varying roles that different MHD forces play along the path of a plasma parcel flowing around the magnetopause. That study resulted in a new description of the behavior of magnetosheath magnetic flux tubes which better explains the plasma depletion along a flux tube. The slow mode waves have been observed in the magnetosheath and have been used to explain the formation of the PDL in some of the important PDL models. In this study, we extend our former work by investigating the possible role of the slow mode waves for the formation of the PDL, using global MHD model simulations. We propose a new technique to test where a possible slow mode front may occur in the magnetosheath by comparing the slow mode group velocity with the local flow velocity. We find that the slow mode fronts can exist in certain regions in the magnetosheath under certain solar wind conditions. The existence and location of such fronts clearly depend on the IMF. We do not see from our global simulation results either the sharpening of the slow mode front into a slow mode shock or noticeable changes of the flow and field in the magnetosheath across the slow mode front, which implies that the slow mode front is not likely responsible for the formation of the PDL, at least for the stable solar wind conditions used in these simulations. Also, we do not see the two-layered slow mode structures shown in some observations and proposed in certain PDL models. Instead, we see only a one-layered spatial PDL structure under the stable solar wind conditions used in this study.