The first global kinetic simulation of Solar Wind-Magnetosphere-Moon coupling is presented. We employ a 3D particle-in-cell (PIC) electromagnetic global simulation model to study the influence of the solar wind on the outflow of Oxygen and Hydrogen from the high latitude ionosphere to the lunar surface. In the simulation, the Earth and the Moon are aligned along the Sun-Earth line (full Moon) with the moon located downstream at 60 Earth radii. Solar wind particles that reach the moon are allowed to pile up to account for charge accumulation and potential differences on the lunar surface. We use established techniques (pressure balance method) to determine the location of the magnetopause under a steady flow of northern IMF. The magnetopause stand-off distance is 8.25 Earth radii and under the solar wind conditions used (Vsw=500km/s, Bz=+2.2nT, Ni,e =5particles/cc), it is found that the quasi-neutrality condition in the solar wind plasma near the lunar surface breaks down, leading to an induced potential difference over the lunar surface. Backstreaming ions observed in the simulation are characterized and found to be diffuse with a small coefficient of reflection. Lunar wake ion and electron densities and temperatures are also analyzed, and particle fluxes refilling the wake are estimated. The results of our study will inform future studies of the solar wind's impact on the Moon in its various phases as well as on other planetary moon systems..
The boundary between the solar wind (SW) and the Earth’s magnetosphere, named the magnetopause (MP), is highly dynamic. Its location and shape can vary as a function of different SW parameters such as density, velocity, and interplanetary magnetic field (IMF) orientations. We employ a 3D kinetic Particle-In-Cell (IAPIC) code to simulate these effects. We investigate the impact of radial (B = Bx) and quasi-radial (Bz < Bx, By) IMF on the shape and size of Earth’s MP for a dipole tilt of 31o using both maximum density steepening and pressure system balance methods for identifying the boundary. We find that, compared with northward or southward-dominant IMF conditions, the MP position expands asymmetrically by 8 to 22% under radial IMF. In addition, we construct the MP shape along the tilted magnetic equator and the OX axes showing that the expansion is asymmetric, not global, stronger on the MP flanks, and is sensitive to the ambient IMF. Finally, we investigate the contribution of SW backstreaming ions by the bow shock to the MP expansion, the temperature anisotropy in the magnetosheath, and a strong dawn-dusk asymmetry in MP location.
In the present work, we consider four dipolarization front (DF) events detected by MMS spacecraft in the Earth’s magnetotail during a substorm on 23rd of July 2017 between 16:05 and 17:19 UT. From their ion scale properties, we show that these four DF events embedded in fast Earthward plasma flows have classical signatures with increases of Bz, velocity and temperature and a decrease of density across the DF. We compute and compare current densities obtained from magnetic and particle measurements and analyse the Ohm’s law. Then we describe the wave activity related to these DFs. We investigate energy conversion processes via J.E calculations and estimate the importance of the electromagnetic energy flow by computing the divergence of the Poynting vector. Finally we discuss the electromagnetic energy conservation in the context of these DFs.
We report on six dipolarization fronts (DF) embedded in fast earthward flows detected by the Magnetospheric Multiscale (MMS) mission during a substorm event on 23rd of July 2017. We analyzed the Ohm's law for each event and found that ions are mostly decoupled from the magnetic field by the Hall fields. However, the electron pressure gradient term is also contributing to the ion decoupling and likely responsible for an electron decoupling at DF. We also analyzed the energy conversion process and found that the energy in the spacecraft frame is transferred from the electromagnetic field to the plasma ($\mathbf{J}\cdot \mathbf{E}>0$) ahead or at the DF whereas it is the opposite ($\mathbf{J}\cdot \mathbf{E}<0$) behind the front. This reversal is mainly due to a local reversal of the cross-tail current indicating a substructure of the DF. In the fluid frame, we found that the energy is mostly transferred from the plasma to the electromagnetic field ($\mathbf{J}\cdot \mathbf{E'}<0$) and should contribute to the deceleration of the fast flow. However, we show that the energy conversion process is not homogeneous at the electron scales due to electric field fluctuations likely related to lower-hybrid drift waves. Our results suggest that the role of DF in the global energy cycle of the magnetosphere still deserves more investigation. In particular, statistical studies on DF require to be carried out with caution due to these electron scale substructures. Associate Editor Assigned.
The boundary between the solar wind (SW) and the Earth's magnetosphere, the magnetopause (MP), is highly dynamic. Its location and shape depend on SW dynamic pressure and interplanetary magnetic field (IMF) orientation. We use a 3D kinetic Particle-In-Cell code (IAPIC) to simulate an event observed by THEMIS spacecraft on July 16, 2007. We investigate the impact of radial (θBx=0◦) and non-radial (θBx=50◦) IMF on the shape and size of Earth's MP for a dipole tilt of 31◦ using maximum density gradient and pressure balance methods. Using the Shue model as a reference (MP at 10.3 RE), we find that for non-radial IMF the MP expands by 1.4 and 1.7RE along the the Sun-Earth (OX) and tilted magnetic equatorial (Tilt) axes, respectively, and it expands by 0.5 and 1.6RE for radial IMF along the same respective axes. When the effect of backstreaming ions is removed from the bulk flow, the expansion ranges are 1.0 and 1.3RE and 0.2, and 1.2RE, respectively. It is found that the percentage of backstreaming to bulk flow ions are 16.5% and 20% for radial and non-radial IMF. We also show that when the backstreaming ions are not identified, up to 40% of the observed expansion that is due to backstreaming particles can be inadvertently attributed to a change in the SW upstream properties. Finally, we quantified the temperature anisotropy in the magnetosheath, and observed a strong dawn-dusk asymmetry in the MP location, being more extended on the duskside than on the dawnside.
The habitability of the surface of any planet is determined by a complex evolution of its interior, surface, and atmosphere. The electromagnetic and particle radiation of stars drive thermal, chemical, and physical alteration of planetary atmospheres, including escape. Many known extrasolar planets experience vastly different stellar environments than those in our solar system: It is crucial to understand the broad range of processes that lead to atmospheric escape and evolution under a wide range of conditions if we are to assess the habitability of worlds around other stars. One problem encountered between the planetary and the astrophysics communities is a lack of common language for describing escape processes. Each community has customary approximations that may be questioned by the other, such as the hypothesis of H‐dominated thermosphere for astrophysicists or the Sun‐like nature of the stars for planetary scientists. Since exoplanets are becoming one of the main targets for the detection of life, a common set of definitions and hypotheses are required. We review the different escape mechanisms proposed for the evolution of planetary and exoplanetary atmospheres. We propose a common definition for the different escape mechanisms, and we show the important parameters to take into account when evaluating the escape at a planet in time. We show that the paradigm of the magnetic field as an atmospheric shield should be changed and that recent work on the history of Xenon in Earth's atmosphere gives an elegant explanation to its enrichment in heavier isotopes: the so‐called Xenon paradox.
Further to the investigation of the critical properties of the Potts model with q = 3 and 8 states in one dimension (1D) on directed small-world networks reported by Aquino and Lima, which presents, in fact, a second-order phase transition with a new set of critical exponents, in addition to what was reported in Sumour and Lima in studying Ising model on non-local directed small-world for several values of probability 0 < P < 1. In this paper the behavior of two models discussed previously, will be re-examined to study differences between their behavior on directed small-world networks for networks of different values of probability P = 0.1, 0.2, 0.3, 0.4 and 0.5 with different lattice sizes L = 10, 20, 30, 40, and 50 to compare between the important physical variables between Ising and Potts models on the directed small-world networks. We found in our paper that is a phase transitions in both Ising and Potts models depending essentially on the probability P.
While the impact of southward and northward IMF on the dynamics of Earth's magnetosphere have been extensively covered in the last 4 decades, only recently has attention been focused on radially directed IMF. Using global three-dimensional kinetic simulation, we investigate the impact of radial IMF on the general macrostructure of Earth's Magnetosphere. Purely radial (Bx only) IMF was considered in this study. The solar wind in our simulation is not aligned with Parker spiral pattern, and we considered a dipole tilt of 31o . It was found that the Magnetopause expanded to 12.8 RE along magnetic equator if compared to 10 RE typical case, and around 14 RE along sun-earth line projection. It was found that the foot of the shocked solar wind experienced a factor of 2 density increase relative to solar wind input value, and this may be caused by one of the components of the induced magnetic force close to the Magnetopause. The magnetic force (V x B ) for radial IMF is zero, until it hits the Magnetopause. It was shown that the induced magnetic force along 0X axis and directed sunward is a dragging force for plasma, which made the Magnetopause expands while (v x B)_y contribute to the dawn-dusk asymmetry. Finally, we examined the (E x B) drifts, and found that the Y-component of this drift started as early as the bow shock position. These asymmetries inside the magnetosphere and/or magnetosheath impact the solar wind magnetosphere coupling. The new version of IAPPIC includes spatial resolution of 0.1 RE, a planet tilt 31o and ion to electron mass ratio of 64.
IMF orientation values and plasma number densities are surveyed for three spacecraft, MMS, Themis and Cluster. The 4.5 seconds of data survey of MMS and the corresponding times scales of Cluster and Themis are compared with 2 seconds of PIC EM Relativistic code step time. Four IMF orientations are considered in 3D in the code simulations, South, North, Radial and duskdawn directions. The code output data will be transformed to spacecraft positions and compared accordingly. The ions and electrons dy-namics in the foreshock, reconnection, cusps dynamics and other physical parameters are considered in the cur-rent study. The updated version of the code, include, planet tilt 10 deg, space resolution of 0.1 RE and mass ratio of 64.
In this paper, we propose a 3D kinetic model (particle-in-cell, PIC) for the description of the large scale Earth’s bow shock. The proposed version is stable and does not require huge or extensive computer resources. Because PIC simulations work with scaled plasma and field parameters, we also propose to validate our code by comparing its results with the available MHD simulations under same scaled solar wind (SW) and (IMF) conditions. We report new results from the two models. In both codes the Earth’s bow shock position is found to be ≈14.8 R E along the Sun–Earth line, and ≈29 R E on the dusk side. Those findings are consistent with past in situ observations. Both simulations reproduce the theoretical jump conditions at the shock. However, the PIC code density and temperature distributions are inflated and slightly shifted sunward when compared to the MHD resultssearch directions.
The plasma conditions at Earth's magnetosheath region play a crucial role in the transfer of solar wind mass, energy and momentum to Earths magnetosphere. North, South, radial, absence and 3D IMF components are discussed independently under the same solar wind conditions. IMF cone angle impact on total pressure in the magnetosheath are examined for all IMF orientations. The links between multi-species dynamics in the foreshock, the bow shock and the magnetosheath are revisited. IAPPIC EM Relativistic code with finer cell size and reasonable ion to electron mass ratio (Modified version of Baraka2016) for simulating the global magnetosphere in 3D. The current study will serve as a foundation for future detailed case studies. Moreover, this newly modified version of the code is capable of simulating ionosphere-magnetosphere coupling in addition to plasmasphere ion outflow.
The outflow of thermal plasma from the high latitude ionosphere to the magnetosphere (polar wind) has been under investigation using observations and statistical studies for four decades in the altitude range from 1000km to ~ 10 Re, yet we are still missing a global and consistent three-dimensional time-dependent picture of the wind system at the interface between the ionosphere and the magnetosphere. Several questions remain unanswered, such as: I) How the ionospheric ions plasma impact the global structure of the magnetosphere. II) What are the energisation processes of that plasma and where they operate (plasma sheet, ring currents). III) What fraction of the supplied plasma returns to the ionosphere and with what properties after a journey in the magnetosphere; etc. Here, we use a spherical symmetric ionospheric model (International reference ionosphere IRI-2007) that we merge with 3D PIC EM Global code to simulate Magnetosphere-ionosphere coupling. Our aim is to investigate the time-dependent content and dynamics of the 3D magnetosphere in response to thermal ions plasma supply from the ionosphere. Following a comprehensive approach, in this first step, we do not consider chemical reactions nor any feedback from the magnetosphere into the ionosphere. Our newly developed 3D PIC model has a finer grid size (0.1-0.2 RE), a H+ to electron mass ratio of up to 100, includes Earth gravity and tilt of the dipole field. Most importantly, the new tool has the capability to consider distinct species with different masses and charges and to follow them in time separately in the simulation box. We present our first results for the content and dynamics of the magnetosphere following H+ and O+ supply from the ionosphere in the conditions of northern IMF of the solar wind.
We use particle-in-cell PIC 3D Electromagnetic, relativistic global code to address large-scale problems in magnetosphere electrodynamics. Terrestrial bow shock is simulated as an example. 3D Magnetohydrodynamics model ,MHD GUMICS in CCMC project, have been used in parallel with PIC under same scaled Solar wind (SW) and IMF conditions. We report new results from the coupling between the two models. Further investigations are required for confirmations of these results. In both codes the Earth's bow shock position is found at ~14.8 RE along the Sun-Earth line, and ~29 RE on the dusk side which is consistent with past in situ observation. Both simulations reproduce the theoretical jump conditions at the shock. However, PIC code density and temperature distributions are inflated and slightly shifted sunward when compared to MHD results. Reflected ions upstream of the bow shock may cause this sunward shift for density and temperature. Distribution of reflected ions and electrons are shown in the foreshock region, within the transition of the shock and in the downstream. The current version of PIC code can be run under modest computing facilities and resources. Additionally, existing MHD simulations should be useful to calibrate scaled properties of plasma resulting from PIC simulations for comparison with observations. Similarities and drawbacks of the results obtained by the two models are listed. The ultimate goal of using these different models in a complimentary manner rather than competitive is to better understand the macrostructure of the magnetosphere.
The unusual event of Jan 21st 2005 observed by Cluster spacecrafts and other space instruments, has been considered for comparison with numerical simulations using a PIC EM Relativistic code for several solar wind plasma conditions. From the comparison using the results obtained so far, we could learn that the main difficulty of the simulation of strong events measured in situ is to properly define/find the undisturbed SW boundary conditions. The second lesson is that it is difficult for the strong and sharp jumps observed in the plasma properties to obtain a clear steady state of the magnetosphere that could be compared instantaneously with in situ measurements. We will show a detailed comparison of the plasma density, velocity components, and magnetic field components along the CL trajectory to the measured in situ data, stressing the added-value of using a PIC code to enrich our diagnostic about very short-term magnetospheric events.
Particles-In-Cell (PIC) and magnetohydrodynamics (MHD) 3D models are used to simulate Earth's magnetosphere under similar solar wind (SW) and north interplanetary magnetic field (IMF) conditions. The bow shock's position is found by both codes at a distance of ~14.8 RE along the Sun-Earth line, and ~29 RE on the dusk side, consistent with past in situ observations. Based on our comparison, running PIC and MHD models under similar input SW parameters elucidates the strengths and drawbacks of these approaches and demonstrates the use of both models in a complementary, rather than competitive, manner for a better understanding of magnetospheres.
A new approach is proposed to study the sensitivity of the Earth’s magnetosphere to the variability of the solar wind bulk velocity. The study was carried out using a three‐dimensional electromagnetic particle‐in‐cell code, with the microphysics interaction processes described by Maxwell and Lorentz equations, respectively, for the fields and particles. Starting with a solar wind with zero interplanetary magnetic field (IMF) impinging upon a magnetized Earth, the formation of the magnetospheric cavity and its elongation around the planet were modeled over time until a steady state structure of a magnetosphere was attained. The IMF was then added as a steady southward magnetic field. An impulsive disturbance was applied to the system by changing the bulk velocity of the solar wind to simulate a decrease in the solar wind dynamic pressure, followed by its recovery, for both zero and southward IMF. In response to an imposed drop in the solar wind drift velocity, a gap (air pocket) in the incoming solar wind plasma appeared moving toward Earth. The orientation of the cusps was highly affected by the depression of the solar wind for all orientation of IMF. The magnetotail lobes flared out with zero IMF due to the “air pocket” effect. With the nonzero IMF, as soon as the gap hit the initial shock of the steady magnetosphere, a reconnection between the Earth’s magnetic field and the IMF was noticed at the dayside magnetopause. During the expansion phase of the system, the outer boundary of the dayside magnetopause broke up in the absence of the IMF, yet it sustained its bullet shape when a southward IMF was included. The expansion/contraction of the magnetopause nose is almost linear in the absence of the IMF but evolves nonlinearly with a southward IMF. The system recovered its initial state on the dayside soon after the impulsive disturbance was beyond Earth for both cases of zero and nonzero IMF. Comparison with existing observations from Cluster and Interball‐1 seems to confirm many of our simulation results.
The Earth bow shock is created by the supersonic solar wind flowing onto the geomagnetic field. The front of this shock is curved, standing around the Earth from the dayside. The bow shock is of great interest in space plasma investigation as it contains important physics ranging from kinetic to global scales. Interaction of the supersonic solar wind with Earth magnetosphere (magnetopause) creates fast mode magnetosonic waves that travel back upstream, combine and steepen to form the bow shock wave. The distance to the bow shock is then the sum of the magnetopause distance and the magnetosheath thickness. [Merka and Szabo and references therein] It has been established been well established that the bow shock (and the magnetopause) scales with the solar wind ram pressure Psw[Binsack and Vasyliunas, 1968; Formisano, 1979] . We are trying though to simulate the position of the bow shock by using a modified Tristan PIC EM Relativistic Code. By doing so, we will help the science community to use our model to better understand the shock physics in our geospace.
The Earth’s bow shock is created by the supersonic solar wind flowing onto the geomagnetic field. The front of this shock is curved, standing around the Earth from the dayside. The bow shock is of great interest in space plasma investigation as it contains important physics ranging from kinetic to global scales. Interaction of the supersonic solar wind with Earth’s magnetosphere (magnetopause) creates fast mode magnetosonic waves that travel back upstream, combine and steepen to form the bow shock wave. The distance to the bow shock is then the sum of the magnetopause distance and the magnetosheath thickness. [Merka and Szabo and references therein] It has been established been well established that the bow shock (and the magnetopause) scales with the solar wind ram pressure Psw[Binsack and Vasyliunas, 1968; Formisano, 1979] . We are trying though to simulate the position of the bow shock by using a modified Tristan PIC EM Relativistic Code. By doing so, we will help the science community to use our model to better understand the shock physics in our geospace. The Earth’s bow shock is created by the supersonic solar wind flowing onto the geomagnetic field. The front of this shock is curved, standing around the Earth from the dayside. The bow shock is of great interest in space plasma investigation as it contains important physics ranging from kinetic to global scales. Interaction of the supersonic solar wind with Earth’s magnetosphere (magnetopause) creates fast mode magnetosonic waves that travel back upstream, combine and steepen to form the bow shock wave. The distance to the bow shock is then the sum of the magnetopause distance and the magnetosheath thickness. [Merka and Szabo and references therein] It has been established been well established that the bow shock (and the magnetopause) scales with the solar wind ram pressure Psw[Binsack and Vasyliunas, 1968; Formisano, 1979] . We are trying though to simulate the position of the bow shock by using a modified Tristan PIC EM Relativistic Code. By doing so, we will help the science community to use our model to better understand the shock physics in our geospace.
A new approach is proposed to study the sensitivity of the Earth Magnetosphere to the variability of the Solar Wind bulk velocity. A numerical particles in cell (PIC) method initially proposed by Buneman (1993) has been adopted and modified to carry out the study. Space was stretched as cubic boxes of dimension 155x105x105 Re filled with 2 million of Solar Wind particles, with Earth is located at 60x52x53 Re. The magnetic field of Earth was hypothetically set to zero, and then switched on. The formation of the magnetospheric cavity and its elongation around the planet was observed to evolve with time until a steady state topology of the system is attained with the classical structure of a magnetosphere. We also found that the cavity is repopulated by clouds of particles from the Solar Wind, producing the current sheet-- a thin plasma sheet that stands at the equatorial plane. The study was carried out with the very basic elements of the interaction processes as described by Maxwell and Lorentz equations. IMF was then included as a steady southward magnetic field. Drift velocity of the Solar Wind was changed to simulate compression/depression of the system. 3-D analysis of the response of the magnetosphere dayside to that variation was studied, and the corresponding relaxation time of the magnetopause interface was measured. In response to the Solar Wind drift velocity imposed drop-off, a ~ 15 Re gap in the incoming Solar Wind plasma appeared moving toward Earth. As soon as the gap hit the initial shock of the steady magnetosphere, a reconnection between the Earth magnetic field and IMF was noticed at the dayside magnetopause when IMF was included. Injection of nightside of the magnetosphere by energetic particles due to magnetic erosion and reconnection is observed. During the expansion phase of the disturbance, the outer boundary of the dayside magnetopause broke up during the absence of the IMF as it responded to the reduction of the ram pressure, whilst sustained its bullet shape with a thin layer of plasma walling its boundary when a southward IMF was included. The expansion/contraction of the magnetopause nose position side was almost linear in the absence of IMF but shrank when IMF was included. Thanks to the complete view provided by the PIC code on particles and fields present in the system, a simple statistical and time analysis is presented aimed to explain the forces and physics processes in play during the travel of the depression gap through the simulation box. The system recovered to its initial state on the dayside soon after the impulse disturbance was beyond the Earth position.