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The orientation parameter effect of a hot Jupiter's intrinsic dipole magnetic field on the flow structure in an extended gaseous (ionospheric) envelope of the planet is studied with a three-dimensional numerical simulation. For example, the hot Jupiter HD 209458b is considered. The magnitude of the planet's magnetic momentum was set equal to 0.1 of the magnetic momentum of Jupiter. The parameters of the stellar wind's magnetic field corresponding to the case of a super-Alfvén flow regime around the planet's atmosphere was taken into account. Under such conditions, calculations have shown that a quasi-closed gaseous (ionospheric) envelope with an induced shock magnetosphere is formed around a hot Jupiter, with a detailed structure determined by the magnetic dipole's slope angle. In this case, the mass-loss rate depends on the orientation of the planet's dipole magnetic field and increases with an increasing angle between the direction to the star and the direction closest to the inner Lagrange point's magnetic pole. This is due to the electromagnetic force increase that impedes the free movement of the matter in the emerging outflow when the magnetic pole approaches the inner Lagrange point. [ABSTRACT FROM AUTHOR]

As a rule, the orbits of "hot Jupiter" exoplanets are located close to the Alfven point of the stellar wind of the host star. Many hot Jupiters could be in the sub-Alfven zone, where the magnetic pressure of the stellar wind exceeds the dynamical pressure. Therefore, the magnetic field in the wind should play an extremely important role in the process of stellar wind flowing around the atmosphere of a hot Jupiter. This must be taken into account when constructing theoretical models and interpreting observational data. Analyses show that many typical hot Jupiters should have shockless induced magnetospheres, which have no analogs in the solar system. Such magnetospheres are characterized first and foremost by the fact that there is no bow shock, and the magnetic barrier (ionopause) is formed by induced currents in upper layers of the ionosphere. This conclusion is confirmed here using three-dimensional numerical simulations of the flow of the stellar wind from the host star around the hot Jupiter HD 209458b, taking into account both the intrinsic magnetic field of the planet and the magnetic field in the wind. [ABSTRACT FROM AUTHOR]

The passage of a hot Jupiter with a quasi-closed extended envelope through a short coronal mass ejection (CME) with a small opening angle is considered. The results of three-dimensional gasdynamical simulations are used to determine the characteristics of the flow in the planet's envelope as it intersects the CME, and to infer possible observational manifestations of such an event. Two options are considered—entry of the planet into the CME at the beginning of the CME and a tangential interaction with the leading edge of the CME. The mass lost by the planet as a result of its interaction with the CME is estimated. [ABSTRACT FROM AUTHOR]

Results of a study of the influence of solar-type host stars superflares on the gas dynamics of the extended envelopes of giant exoplanets are presented. During flare events, the radiation intensity of the host star in the extreme ultraviolet and soft X-ray can increase by several orders of magnitude for a short time, leading to strong local heating of the exoplanet atmosphere on the side facing the star, with the formation of shocks in the atmosphere. Computations of the gas-dynamical response of the atmosphere of the hot Jupiter HD 209458b to characteristic superflares of solar-like stars were carried out earlier in [1] using a one-dimensional aeronomical model correctly taking into account heating and chemical processes in the atmosphere. To investigate the outflow of atmospheric gas, the results obtained with this onedimensional model were used as simple boundary conditions for computations of the three-dimensional flow structure after a flare. The results of these three-dimensional gas-dynamical computations show that the mass ejection of the flare increases the size of the envelope over several hours, which could be detected with existing observing facilities. It is shown that the mass-loss rates for the most powerful superflare considered could be enhanced by an order of magnitude over several tens of hours after the flare. [ABSTRACT FROM AUTHOR]

A one-dimensional aeronomic model of the upper atmosphere of a giant planet is used to study the reaction of the atmosphere of the hot Jupiter HD 209458b to additional heating by a stellar flare. It is shown that the absorption of additional energy from the stellar flare in the extreme ultraviolet leads to local heating of the atmosphere, accompanied by the formation of two shocks propagating in the atmosphere. Possible observational manifestations of these shocks and the feasibility of their detection are discussed. [ABSTRACT FROM AUTHOR]

The discovery of the possible existence of huge quasi-stationary envelopes around a number of hot Jupiters (i.e., with sizes appreciably exceeding their Roche lobes) and the need to correctly take into account their properties when interpreting observational data require a careful analysis of the main physical processes influencing their atmospheres. One important factor is the possibility that the planet has a magnetic field. It was shown earlier that the presence of even a modest dipolar magnetic field of a hot Jupiter (with a magnetic moment approximately 1/10 the magnetic moment of Jupiter) influences the properties of the planetary atmosphere, in particular, leading to expansion of the range of parameters for which a giant, quasi-closed envelope can form around the planet. It was also established that the presence of a planetary magnetic field reduced the mass-loss rate from the envelope, since matter flowing out from the inner Lagrange point moves perpendicular to the field lines. Three-dimensional magnetohydrodynamical (MHD) modeling on time scales appreciably exceeding the time for the formation of the envelope show that pulsations arise in the atmospheres of hot Jupiters possessing dipolar magnetic fields, with characteristic periods ~0.27 P . This behavior is easy to understand physically, since even in the case of a spherical atmosphere, the continuous expansion of the ionized atmsphere of a hot Jupiter can lead to the accumulation of matter in regions bounded by closed field lines, and to the periodic rupture of the atmosphere beyond the magnetic field. In the case considered, when the system contains a giant envelope fed by a stream of matter from the inner Lagrange point, the presence of such pulsations gives rise to appreciable variations in the gas-dynamical structure of the flow. In particular, pulsations of the atmosphere lead to tearing off of part of the flow and sharp fluctuations in the size of the envelope, leading to variations in the envelope's observational properties. [ABSTRACT FROM AUTHOR]

The influence of the dipolar magnetic field of a 'hot Jupiter' with the parameters of the object WASP-12b on the mass-loss rate from its atmosphere is investigated. The results of three-dimensional gas-dynamical and magnetohydrodynamical computations show that the presence of a magnetic moment with a strength of ~0.1 the magnetic moment of Jupiter leads to appreciable variations of the matter flow structure. For example, in the case of the exoplanet WASP-12b with its specified set of atmospheric parameters, the stream from the vicinity of the Lagrange point L is not stopped by the dynamical pressure of the stellar wind, and the envelope remains open. Including the effect of the magnetic field leads to a variation in this picture-the atmosphere becomes quasi-closed, with a characteristic size of order 14 planetary radii, which, in turn, substantially decreases the mass-loss rate by the exoplanet atmosphere (by~70%). This reduction of the mass-loss rate due to the influence of the magnetic fieldmakes it possible for exoplanets to form closed and quasi-closed envelopes in the presence of more strongly overflowing Roche lobes than is possible without a magnetic field. [ABSTRACT FROM AUTHOR]

A self-consistent, aeronomic model of the upper atmosphere of a 'hot Jupiter' including reactions involving suprathermal photoelectrons is presented. This model is used to compute the height profiles of the gas density, velocity, and temperature in the atmosphere of the exoplanet HD 209458b. It is shown that including suprathermal electrons when computing the heating and cooling functions reduces the mass loss rate of the atmosphere by a factor of five. [ABSTRACT FROM AUTHOR]

The results of three-dimensional numerical simulations of the gas dynamics of the atmosphere of a 'hot Jupiter' exoplanet during the passage of a coronal mass ejection (CME) from the central star are presented. These computations assumed the parameters for the stellar wind and the CME to be typical of the solar values. The characteristic variations of the flow pattern are considered for quasi-closed and closed (but appreciably distorted by the gravitational influence of the star) gaseous envelopes of the exoplanet. It is shown that a typical CME is sufficient to tear off the outer part of an asymmetric envelope that is located beyond the Roche lobe and carry it away from the exoplanet. This leads to a substantial increase in the mass-loss rate from the exoplanet envelope during the passage of CMEs. The mass-loss rate grows by about a factor of 11 for a closed envelope, and by about a factor of 14 for a quasi-closed envelope. Possible evolutionary consequences of the loss of part of the atmosphere during the passage of CMEs are discussed. [ABSTRACT FROM AUTHOR]

The possibility of explaining the collected data for the hot Jupiter WASP-12b using a model with a stationary, quasi-closed, aspherical envelope around the exoplanet is considered. The influence of variations of the parameters of the stellar wind on the size and shape of the quasi-closed envelope is considered, and the maximum size of the envelope is determined to be Δ φ ≃ 0.17 ( φ is the orbital phase of the planet measured from the position of the main minimum). In order for the UV eclipse to begin at the phase indicated by observations with the Hubble Space Telescope, φ ≃ 0.83, the size of the envelope must be Δ φ ≃ 0.12, or 21 R ( R is the radius of the planet). This size is in very good agreement with theoretical estimates obtained assuming solar parameters for the stellar wind. Unfortunately, this conclusion is not firm, since the available observations begin at phase φ ≃ 0.83, hindering any conclusions about the character of the light curve at earlier phases. In the case of a quasi-closed or an open envelope, the UV eclipse could begin at earlier phases, φ ≃ 0.78 and φ ≃ 0.7, respectively. Determining the true nature of the envelope of WASP-12b will require additional UV observations beginning from a phase earlier than the phase corresponding to the eclipse of a quasi-closed envelope of the maximum size, φ < 0.78. [ABSTRACT FROM AUTHOR]

According to the compuations results obtained by Bisikalo et al. (2013) for the gas-dynamical effect of stellar winds on exoplanet atmospheres, three types of gaseous envelopes can form around hot Jupiters: closed, quasi-closed, and open. The type of envelope that forms depends on the position of the frontal collision point (where the dynamical pressure of the wind is equal to the pressure of the surrounding atmosphere) relative to the Roche-lobe boundaries. Closed envelopes are formed around planets whose atmospheres lie completely within their Roche lobes. If the frontal collision point is located outside the Roche lobe, the atmospheric material begins to flow out through the Lagrangian points L and L, which can result in the formation of quasi-closed (if the dynamical pressure of the stellar wind stops the outflow through L) or open gaseous envelopes. The example of the typical hot Jupiter HD 209458b is considered for four sets of atmospheric parameters, to determine the mass-loss rates for the different types of envelopes arising with these parameters. The mass-loss rates based on the modeling results were estimated to be Ṁ ≤ 10 g/s for a closed atmosphere, Ṁ ≃ 3 × 10 g/s for a quasi-closed atmosphere, and Ṁ ≃ 3 × 10 g/s for an open atmosphere. The matter in the closed and quasi-closed atmospheres flows out mainly through L, and the matter in open envelopes primarily through L. [ABSTRACT FROM AUTHOR]