scholarly journals Multi-Component MHD Model of Hot Jupiter Envelopes

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 422
Author(s):  
Andrey Zhilkin ◽  
Dmitri Bisikalo
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Numerical Model ◽  
Stellar Wind ◽  
Bow Shock ◽  
Model Description ◽  
Hot Jupiters ◽  
Bow Shock Wave ◽  
Field Lines ◽  
Hot Jupiter

A numerical model description of a hot Jupiter extended envelope based on the approximation of multi-component magnetic hydrodynamics is presented. The main attention is focused on the problem of implementing the completed MHD stellar wind model. As a result, the numerical model becomes applicable for calculating the structure of the extended envelope of hot Jupiters not only in the super-Alfvén and sub-Alfvén regimes of the stellar wind flow around and in the trans-Alfvén regime. The multi-component MHD approximation allows the consideration of changes in the chemical composition of hydrogen–helium envelopes of hot Jupiters. The results of calculations show that, in the case of a super-Alfvén flow regime, all the previously discovered types of extended gas-dynamic envelopes are realized in the new numerical model. With an increase in magnitude of the wind magnetic field, the extended envelope tends to become more closed. Under the influence of a strong magnetic field of the stellar wind, the envelope matter does not move along the ballistic trajectory but along the magnetic field lines of the wind toward the host star. This corresponds to an additional (sub-Alfvénic) envelope type of hot Jupiters, which has specific observational features. In the transient (trans-Alfvén) mode, a bow shock wave has a fragmentary nature. In the fully sub-Alfvén regime, the bow shock wave is not formed, and the flow structure is shock-less.

Influence of the magnetic field of stellar wind on hot jupiter’s envelopes

2019 ◽  
Vol 15 (S354) ◽  
pp. 268-279
Author(s):  
Dmitry V. Bisikalo ◽  
Andrey G. Zhilkin
Keyword(s):  
Magnetic Field ◽  
Plasma Flow ◽  
Coronal Mass Ejections ◽  
Stellar Wind ◽  
Roche Lobe ◽  
Bow Shock ◽  
Hot Jupiters ◽  
The Magnetic Field ◽  
Alfven Velocity ◽  
Hot Jupiter

AbstractHot Jupiters have extended gaseous (ionospheric) envelopes, which extend far beyond the Roche lobe. The envelopes are loosely bound to the planet and, therefore, are strongly influenced by fluctuations of the stellar wind. We show that, since hot Jupiters are close to the parent stars, magnetic field of the stellar wind is an important factor defining the structure of their magnetospheres. For a typical hot Jupiter, velocity of the stellar wind plasma flow around the atmosphere is close to the Alfvén velocity. As a result stellar wind fluctuations, such as coronal mass ejections, can affect the conditions for the formation of a bow shock around a hot Jupiter. This effect can affect observational manifestations of hot Jupiters.

scholarly journals Optical hydrogen absorption consistent with a bow shock around the hot Jupiter HD 189733 b

2015 ◽  
Vol 11 (S320) ◽  
pp. 376-381 ◽  
Author(s):  
P. Wilson Cauley ◽  
Seth Redfield ◽  
Adam G. Jensen ◽  
Travis Barman ◽  
Michael Endl ◽  
...  
Keyword(s):  
Stellar Wind ◽  
Bow Shock ◽  
Transmission Spectra ◽  
Shock Model ◽  
Hot Jupiters ◽  
Balmer Lines ◽  
Planetary Magnetic Field ◽  
Host Stars ◽  
Hot Jupiter

AbstractHot Jupiters, i.e., Jupiter-mass planets with orbital semi major axes of <10 stellar radii, can interact strongly with their host stars. If the planet is moving supersonically through the stellar wind, a bow shock will form ahead of the planet where the planetary magnetosphere slams into the the stellar wind or where the planetary outflow and stellar wind meet. Here we present high resolution spectra of the hydrogen Balmer lines for a single transit of the hot Jupiter HD 189733 b. Transmission spectra of the Balmer lines show strong absorption ~70 minutes before the predicted optical transit, implying a significant column density of excited hydrogen orbiting ahead of the planet. We show that a simple geometric bow shock model is able to reproduce the important features of the absorption time series while simultaneously matching the line profile morphology. Our model suggests a large planetary magnetic field strength of ~28 G. Follow-up observations are needed to confirm the pre-transit signal and investigate any variability in the measurement.

scholarly journals Magnetohydrodynamic simulations of a Uranus-at-equinox type rotating magnetosphere

2020 ◽  
Vol 633 ◽  
pp. A87 ◽  
Author(s):  
L. Griton ◽  
F. Pantellini
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Supersonic Flow ◽  
Magnetic Dipole ◽  
Stellar Wind ◽  
Rotation Axis ◽  
Spin Axis ◽  
Mhd Equations ◽  
Field Lines ◽  
The Magnetic Field

Context. As proven by measurements at Uranus and Neptune, the magnetic dipole axis and planetary spin axis can be off by a large angle exceeding 45°. The magnetosphere of such an (exo-)planet is highly variable over a one-day period and it does potentially exhibit a complex magnetic tail structure. The dynamics and shape of rotating magnetospheres do obviously depend on the planet’s characteristics but also, and very substantially, on the orientation of the planetary spin axis with respect to the impinging, generally highly supersonic, stellar wind. Aims. On its orbit around the Sun, the orientation of Uranus’ spin axis with respect to the solar wind changes from quasi-perpendicular (solstice) to quasi-parallel (equinox). In this paper, we simulate the magnetosphere of a fictitious Uranus-like planet plunged in a supersonic plasma (the stellar wind) at equinox. A simulation with zero wind velocity is also presented in order to help disentangle the effects of the rotation from the effects of the supersonic wind in the structuring of the planetary magnetic tail. Methods. The ideal magnetohydrodynamic (MHD) equations in conservative form are integrated on a structured spherical grid using the Message-Passing Interface-Adaptive Mesh Refinement Versatile Advection Code (MPI-AMRVAC). In order to limit diffusivity at grid level, we used background and residual decomposition of the magnetic field. The magnetic field is thus made of the sum of a prescribed time-dependent background field B0(t) and a residual field B1(t) computed by the code. In our simulations, B0(t) is essentially made of a rigidly rotating potential dipole field. Results. The first simulation shows that, while plunged in a non-magnetised plasma, a magnetic dipole rotating about an axis oriented at 90° with respect to itself does naturally accelerate the plasma away from the dipole around the rotation axis. The acceleration occurs over a spatial scale of the order of the Alfvénic co-rotation scale r*. During the acceleration, the dipole lines become stretched and twisted. The observed asymptotic fluid velocities are of the order of the phase speed of the fast MHD mode. In two simulations where the surrounding non-magnetised plasma was chosen to move at supersonic speed perpendicularly to the rotation axis (a situation that is reminiscent of Uranus in the solar wind at equinox), the lines of each hemisphere are symmetrically twisted and stretched as before. However, they are also bent by the supersonic flow, thus forming a magnetic tail of interlaced field lines of opposite polarity. Similarly to the case with no wind, the interlaced field lines and the attached plasma are accelerated by the rotation and also by the transfer of kinetic energy flux from the surrounding supersonic flow. The tailwards fluid velocity increases asymptotically towards the externally imposed flow velocity, or wind. In one more simulation, a transverse magnetic field, to both the spin axis and flow direction, was added to the impinging flow so that magnetic reconnection could occur between the dipole anchored field lines and the impinging field lines. No major difference with respect to the no-magnetised flow case is observed, except that the tailwards acceleration occurs in two steps and is slightly more efficient. In order to emphasise the effect of rotation, we only address the case of a fast-rotating planet where the co-rotation scale r* is of the order of the planetary counter-flow magnetopause stand-off distance rm. For Uranus, r*≫ rm and the effects of rotation are only visible at large tailwards distances r ≫ rm.

scholarly journals On the vorticity behind 3-D detached bow shock wave

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
V. N. Golubkin ◽  
G. B. Sizykh
Keyword(s):  
Shock Wave ◽  
Bow Shock ◽  
Bow Shock Wave

Vortical regime of the flow behind the bow shock wave

Shock Waves ◽  
2001 ◽  
Vol 11 (3) ◽  
pp. 229-244 ◽  
Author(s):  
V. Svetsov
Keyword(s):  
Shock Wave ◽  
Bow Shock ◽  
Bow Shock Wave

scholarly journals Unsteady flow mechanisms in the last stage of a transonic low pressure steam turbine—multistage effects and tip leakage flows

2017 ◽  
Vol 1 ◽  
pp. F4IW8S
Author(s):  
Ilias Papagiannis ◽  
Asad Raheem ◽  
Altug Basol ◽  
Anestis Kalfas ◽  
Reza Abhari ◽  
...  
Keyword(s):  
Shock Wave ◽  
Steam Turbine ◽  
Leading Edge ◽  
Bow Shock ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Bow Shock Wave ◽  
Last Stage ◽  
Two Stages

Abstract In this paper, an unsteady investigation of the last two stages of a low-pressure steam turbine with supersonic airfoils near the tip of the last stage’s rotor blade is presented. Goal is the investigation of multistage effects and tip leakage flow in the last stage of the turbine and to provide insight on the stator-rotor flow interaction in the presence of a bow-shock wave. This study is unique in a sense of combining experimental data for code validation and comparison with a numerical simulation of the last two stages of a real steam turbine, including tip-cavity paths and seals, steam modelling and experimental data used as inlet and outlet boundary conditions. Analysis of results shows high unsteadiness close to the tip of the last stage, due to the presence of a bow-shock wave upstream of the rotor blade leading edge and its interaction with the upstream stator blades, but no boundary layer separation on stator is detected at any instant in time. The intensity of the shock wave is weakest, when the axial distance of the rotor leading edge from the upstream stator trailing edge is largest, since it has more space available to weaken. However, a phase shift between the maximum values of static pressure along the suction side of the stator blade is identified, due to the shock wave moving with the rotor blades. Additionally, the bow-shock wave interacts with the blade shroud and the tip leakage flow. Despite the interaction with the incoming flow, the total tip leakage mass flow ingested in the tip-cavity shows a steady behaviour with extremely low fluctuations in time. Finally, traces of upstream stage’s leakage flow have been identified in the last stage, contributing to entropy generation in inlet and outlet of last stage’s stator blade, highlighting the importance of performing multistage simulations.

scholarly journals Venus's induced magnetosphere during active solar wind conditions at BepiColombo's Venus 1 flyby

2021 ◽  
Author(s):  
Martin Volwerk ◽  
Beatriz Sánchez-Cano ◽  
Daniel Heyner ◽  
Sae Aizawa ◽  
Nicolas André ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Coronal Mass Ejection ◽  
Interplanetary Magnetic Field ◽  
Bow Shock ◽  
Gravity Assist ◽  
Highly Active ◽  
Field Lines ◽  
Mass Ejection ◽  
The Magnetic Field

Abstract. Out of the two Venus flybys that BepiColombo uses as a gravity assist manoeuvre to finally arrive at Mercury, the first took place on 15 October 2020. After passing the bow shock, the spacecraft travelled along the induced magnetotail, crossing it mainly in the YVSO-direction. In this paper, the BepiColombo Mercury Planetary Orbiter Magnetometer (MPO-MAG) data are discussed, with support from three other plasma instruments: the Planetary Ion Camera (PICAM), the Mercury Electron Analyser (MEA) and the radiation monitor (BERM). Behind the bow shock crossing, the magnetic field showed a draping pattern consistent with field lines connected to the interplanetary magnetic field wrapping around the planet. This flyby showed a highly active magnetotail, with, e.g., strong flapping motions at a period of ~7 min. This activity was driven by solar wind conditions. Just before this flyby, Venus's induced magnetosphere was impacted by a stealth coronal mass ejection, of which the trailing side was still interacting with it during the flyby. This flyby is a unique opportunity to study the full length and structure of the induced magnetotail of Venus, indicating that the tail was most likely still present at about 48 Venus radii.

Magnetosphere of Hot Jupiter HD209458b and transit absorption in lines related to the upper atmosphere

2021 ◽  
Author(s):  
Ildar Shaikhislamov ◽  
Maxim Khodachenko ◽  
Ilya Miroshnichenko ◽  
Marina Rumenskikh ◽  
Artem Berezutsky
Keyword(s):  
Magnetic Field ◽  
Magnetic Dipole ◽  
Stellar Wind ◽  
Mass Loss Rate ◽  
Spectral Lines ◽  
Upper Atmosphere ◽  
Russian Science ◽  
Mhd Simulations ◽  
The Magnetic Field ◽  
Hot Jupiter

&lt;p&gt;Using the global 3D multi-fluid HD and its extension to MHD we simulated the measured HD209458b transit absorption depths at the FUV lines, and at the NIR line (10830 &amp;#197;) of metastable helium HeI(2&lt;sup&gt;3&lt;/sup&gt;S) triplet, paying attention to possible change of the absorption profiles due to the presence of planetary intrinsic magnetic field. As continuation of our previous studies of HD209458b (&lt;em&gt;Shaikhislamov et al. 2018, 2020&lt;/em&gt;), the inclusion of the HeI(2&lt;sup&gt;3&lt;/sup&gt;S) line into consideration and the comparison with corresponding measurements allows to constrain the helium abundance by He/H ~ 0.02, and stellar XUV flux at 1 a.u. by &lt;em&gt;F&lt;/em&gt;&lt;sub&gt;XUV &lt;/sub&gt;~10 erg cm&lt;sup&gt;2&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt; at 1 a.u. For the first time, we studied the influence of the planetary dipole magnetic field with a model which self-consistently describes the generation of the escaping upper atmospheric flow of a magnetized hot Jupiter, formation of magnetosphere and its interaction with the stellar wind. We simulated the absorption in the most of spectral lines for which measurements have been made. MHD simulations have shown that the planetary magnetic dipole moment &amp;#181;&lt;sub&gt;P&lt;/sub&gt; = 0.61 of the Jovian value, which produces the magnetic field equatorial surface value of 1 G, profoundly changes the character of the escaping planetary upper atmosphere. The total mass loss rate in this case is reduced by 2 times, as compared to the non-magnetized planet. In particular, we see the formation of the dead- and the wind- zones around the planet with the different character of plasma motion there. The 3D MHD modelling also confirmed the previous 2D MHD simulations result of &lt;em&gt;Khodachenko et al (2015) &lt;/em&gt;that the escaping PW forms a thin magnetodisk in the equatorial region around the planet. The significantly reduced velocity of PW at the low altitudes around the planet, and especially at the night side, results in the stronger photo-ionization of species and significantly lower densities of the corresponding absorbing elements. Altogether, the reduced velocities and lower densities result in significant decrease of the absorption at Ly&amp;#945; (HI), OI, and CII lines, though the absorption at HeI(2&lt;sup&gt;3&lt;/sup&gt;S) line remains nearly the same.&lt;/p&gt; &lt;p&gt;As it was shown in our previous papers, the dense and fast stellar wind, interacting with the escaping upper atmosphere of HD209458b, generates sufficient amount of Energetic Neutral Atoms (ENAs) to produce significant absorption in the high-velocity blue wing of the Ly&amp;#945; line. However, according to the performed 3D MHD modelling reported here, the planetary magnetic dipole field with the equatorial surface value of B&lt;sub&gt;p&lt;/sub&gt;=1 G prevents the formation of ENAs, especially in the trailing tail. This effect opens a possibility to constrain the range of planetary magnetic field values for the evaporating hot Jupiters and warm Neptunes in the stellar-planetary systems where sufficiently strong SW is expected.&lt;/p&gt; &lt;p&gt;The presented results fitted to the available measurements indicate that the magnetic field of HD209458b should be at least an order of magnitude less than that of the Jupiter. This conclusion agrees with the previous estimates, based on more simplified models (e.g., &lt;em&gt;Kislyakova et al. 2014&lt;/em&gt;) and much less observational data, when only Ly&amp;#945; absorption was considered. We believe that the application of 3D MHD models simulating the escape of upper atmospheres of hot exoplanets and the related transits at the available for measurement spectral lines, sensitive to the dynamics of planetary plasma affected by the MF, opens a way for probing and quantifying of exoplanetary magnetic fields and sheds more light on their nature.&lt;/p&gt; &lt;p&gt;This work was supported by grant &amp;#8470; 18-12-00080 of the Russian Science Foundation and grant &amp;#8470; 075-15-2020-780 of the Russian Ministry of Education and Science.&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt; &lt;p&gt;Khodachenko, M.L., Shaikhislamov, I.F., Lammer, H., et al., 2015, ApJ, 813, 50.&lt;/p&gt; &lt;p&gt;Shaikhislamov, I. F., Khodachenko, M. L., Lammer, H., et al., 2018, ApJ,&amp;#160;866(1), 47.&lt;/p&gt; &lt;p&gt;Shaikhislamov, I. F., Khodachenko, M. L., Lammer, et al., 2020, MNRAS,&amp;#160;491(3), 3435-3447&lt;/p&gt;

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