Developed for the KI-1 facility, a new bidirectional ion collector probe enables simultaneous, independent plasma measurements in two directions. It characterizes both theta-pinch background plasma and laser plasma which is produced under irradiation a polyethylene target. It measuring density, velocity, and expansion dynamics. The probe shows high sensitivity and agrees with reference instruments. Its key innovation is the ability to measure laser plasma propagation independently of the background, crucial for studying plasma-cloud interactions with magnetic fields.

We report the results of numerical simulation of the generation of intense low-frequency Alfvén waves produced by periodic laser plasma bunches under conditions of substantially pre-Alfvén expansion at Mach numbers MA ≤ 0.2. The effect of the parameters of background plasma and the mass of ions on the effective generation of waves, as well as their structure and intensity is considered.

The paper presents a comparison results of numerical simulation of the generation the Alfven and slow magnetosonic wave created by periodic laser plasma bunches in a magnetized background plasma in the pre-Alfvenic bunch expansion (MA=0.2) and MA=1. It is shown that, regardless of the mode, Alfven wave localized in a magnetic flux tube of radius Rd~1, and the efficiency of converting plasma bunches into an Alfven wave at MA = 0.2 is several times higher than the value obtained at MA = 1.

This paper describes the results of a laboratory experiment on the sub-Alfvén expansion of a quasi-spherical laser plasma cloud into a vacuum magnetic field in the regime of nonmagnetized ions. The role of Hall fields and currents in the anomalously fast dynamics of the magnetic field during the collapse phase of a diamagnetic cavity is considered. Detailed spatial measurements of the azimuthal Hall fields configuration are demonstrated and their relationship to diamagnetic cavity collapse is determined. As a result of the experiment, data were obtained confirming the hypothesis about the transfer of the main magnetic field by the movement of electrons associated with Hall currents.

В настоящей работе представлены результаты лабораторного эксперимента по разлету плазменного облака во внешнее магнитное поле, впервые демонстрирующего подавление характерных Холловских эффектов присутствием фоновой плазмы. Показано, что увеличение концентрации фоновой плазмы приводит к снижению величины Холловских магнитных полей и соответствующих токов, что, в свою очередь, изменяет характер протекания коллапса диамагнитной каверны. При подавлении Холловских эффектов динамика каверны протекает более плавным образом и задерживается по времени. Полученные данные не только обнаруживают влияние фоновой плазмы, но и подчеркивают взаимосвязь между Холловскими эффектами и аномально быстрой динамикой магнитного поля на фазе коллапса диамагнитной каверны.

Ultra-hot Jupiter Kelt9b impels to reconsider existing models of the upper atmospheres of hot exoplanets, which were previously developed using examples of G or M star systems such as HD209458b and GJ436b. The unique conditions of interaction between the radiation of an A-class star and the atmosphere necessitate kinetic modeling of excited levels of elements, primarily the hydrogen atom. Kelt9b shows the absorption for several Balmer lines and lines of a number of heavy elements, the quantitative interpretation of which is an urgent problem. In this study, for the first time, 3D modeling of the atmosphere of a planet with a close location of the Roche lobe is implemented with allowance for the aeronomy and kinetics of excited hydrogen.

Transit observations of exoplanets make it possible to measure temperature and relative abundance of various elements in their atmospheres. The infrared line of metastable helium HeI 10 830 Å is widely used to study the atmospheres of exoplanets by the transit absorption method. The emission spectra of stars have a significant impact on the physical and chemical parameters of the upper layers of the atmospheres. In this paper, we consider the features of absorption in the helium line for stars of different spectral classes by numerical simulation. The results show the key role of the star’s emission spectrum in the formation of the upper atmosphere and in the amplitude of transit absorption of exoplanets in the HeI 10 830-Å line.

ABSTRACT The numerical simulation of the HD 63433 system is performed with the aim to study upper atmospheres of two mini-Neptunes, planets b and c, interacting with the stellar wind of the parent star. The obtained results demonstrate that both exoplanets form the extended envelopes with strong supersonic outflows. The synthetic absorption profiles in the Ly α line show that under moderate stellar wind conditions, similar to those of the normal solar wind, the energetic neutral atoms contribute to the absorption in the high-velocity blue wing of the line at a level of tens per cent. The absorption in metastable helium He i(23S) line appears rather weak and below the detection limit by current instruments. An important feature revealed by the simulations is that the tail of escaping atmospheric material of the inner planet disturbs the stellar wind at orbital location of the outer planet and might, therefore, affect its observation in Ly α line.

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 Å) of metastable helium HeI(23S) 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 (Shaikhislamov et al. 2018, 2020), the inclusion of the HeI(23S) 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 FXUV ~10 erg cm2 s-1 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 µP = 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 Khodachenko et al (2015) 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 Lyα (HI), OI, and CII lines, though the absorption at HeI(23S) line remains nearly the same.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 Lyα line. However, according to the performed 3D MHD modelling reported here, the planetary magnetic dipole field with the equatorial surface value of Bp=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.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., Kislyakova et al. 2014) and much less observational data, when only Lyα 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.This work was supported by grant № 18-12-00080 of the Russian Science Foundation and grant № 075-15-2020-780 of the Russian Ministry of Education and Science. Khodachenko, M.L., Shaikhislamov, I.F., Lammer, H., et al., 2015, ApJ, 813, 50.Shaikhislamov, I. F., Khodachenko, M. L., Lammer, H., et al., 2018, ApJ, 866(1), 47.Shaikhislamov, I. F., Khodachenko, M. L., Lammer, et al., 2020, MNRAS, 491(3), 3435-3447

The laboratory experiment on modeling a sub-Alfvénic interaction of expanding plasma cloud with vacuum magnetic field is described. We produce spherically symmetric cloud by 4-beam laser irradiation of the pellet. The presented data reveal complex dynamic of cloud deceleration and formation of two field aligned jets, development of the flute instability and rapid collapse of the diamagnetic cavity. It is shown that cavity collapse can’t be explained by plasma motion or anomalous diffusion and requires for explanation a new mechanism.

Structural instabilities that develop during pulsed injection of dense plasma jets into vacuum in the presence of an external quasi-homogeneous magnetic field are studied by high-speed photography using ICCD cameras. The experiments are carried out in the chamber of the “Krot” stand, which has record-breaking dimensions in its class of installations (diameter—3 m, length of the working section—10 m), and makes it possible to study plasma dynamics by various diagnostic methods at scales of more than 1 m both along the magnetic field and in the direction transverse to the magnetic field. During injection along the magnetic field, a transverse collimation of the flow of ionized matter and the development of a flute instability of the plasma boundary are observed, which, at the late stages of expansion, leads to the plasma leaving the injection region in the form of several jets across the field. During transverse injection, the formation of a collimated flow, a “plasma sheet,” is observed, in which, as the plasma moves across the field, inhomogeneous structures develop in the direction of injection.

We aim to narrow down the origin of the non-detection of the metastable HeI triplet at about 10830 A obtained for the hot Jupiter WASP-80b. We measure the X-ray flux of WASP-80 from archival observations and use it as input to scaling relations accounting for the coronal [Fe/O] abundance ratio to infer the extreme-ultraviolet (EUV) flux in the 200-504 A range, which controls the formation of metastable HeI. We run three dimensional (magneto) hydrodynamic simulations of the expanding planetary upper atmosphere interacting with the stellar wind to study the impact on the HeI absorption of the stellar high-energy emission, the He/H abundance ratio, the stellar wind, and the possible presence of a planetary magnetic field up to 1 G. For a low stellar EUV emission, which is favoured by the measured logR'HK value, the HeI non-detection can be explained by a solar He/H abundance ratio in combination with a strong stellar wind, or by a sub-solar He/H abundance ratio, or by a combination of the two. For a high stellar EUV emission, the non-detection implies a sub-solar He/H abundance ratio. A planetary magnetic field is unlikely to be the cause of the non-detection. The low EUV stellar flux, driven by the low [Fe/O] coronal abundance, is the likely primary cause of the HeI non-detection. High-quality EUV spectra of nearby stars are urgently needed to improve the accuracy of high-energy emission estimates, which would then enable one to employ the observations to constrain the planetary He/H abundance ratio and the stellar wind strength. This would greatly enhance the information that can be extracted from HeI atmospheric characterisation observations.

The results of modeling the Hα absorption spectrum of the atmosphere of the hot Jupiter WASP‑52b are presented. The atmosphere was modeled with a three-dimensional hydrodynamic code. Several different values of the XUV ionizing radiation were considered. The Lyα-photon transfer in the atmosphere was simulated by the Monte Carlo method. Spatial distributions of the volume density of hydrogen atoms excited to the second energy level H(2) were obtained, and absorption spectra in the Hα line were calculated. It was also shown that absorption takes place in a layer with a thickness of about 1.5 times the planetary radius, while the greatest influence on absorption is exerted by Lyα photons produced due to recombination of electrons and protons.

Possible reasons for the non-detection of absorption in the metastable He I (2(3)S) line at transit observations of warm Neptune GJ436b, in spite of the well-pronounced strong absorption features measured earlier in Lyafor this planet, are investigated. We perform numeric simulations of the escaping upper atmosphere of this planet and its He I (2(3)S) triplet absorption with a global 3D multifluid, self-consistent hydrodynamic model. By fitting the model parameters to the lowest detection level of absorption measurements, we constrain an upper limit for the He/H abundance three times smaller than the solar value. We demonstrate that neither the significant changes of the stellar wind related to possible stellar coronal mass ejections (CMEs), or possible variations in the stellar ionization radiation, nor the presence of heavy trace elements have a crucial effect on the absorption at the 10 830 angstrom line of He I (2(3)S) triplet. The main reason of weak signature is that the region populated by the absorbing metastable helium is rather small (<3Rp), as well as the small size of the planet itself in comparison to the host star. We show that the radiation pressure force acting on the He I (2(3)S) atoms spreads them along the line of sight and around the planet, thus further reducing peak absorption.

Possible reasons for the non-detection of absorption in the metastable HeI(23S) line at transit observations of warm Neptune GJ436b, in spite of the well pronounced strong absorption features measured earlier in Lyα for this planet, are investigated. We perform numeric simulations of the escaping upper atmosphere of this planet and its HeI(23S) triplet absorption with a global 3D multi-fluid self-consistent hydrodynamic model. By fitting the model parameters to the lowest detection level of absorption measurements, we constrain an upper limit the He/H abundance three times smaller than the solar value. We demonstrate that neither the significant changes of the stellar wind related with possible stellar coronal mass ejections (CMEs), or possible variations in the stellar ionization radiation, nor the presence of heavy trace elements have crucial effect on the absorption at the 10 830 Å line of HeI(23S) triplet. The main reason of weak signature is that the region populated by the absorbing metastable helium is rather small (<3Rp), as well as the small size of the planet itself, in comparison to the host star. We show that the radiation pressure force acting on the HeI(23S) atoms spreads them along the line of sight and around the planet, thus further reducing peak absorption.

As an alternative to the traditionally considered electron cyclotron maser (ECM) mechanism of exoplanetary radio emission (RE), we study plasma maser mechanism. The latter, contrary to ECM operates in dense and weakly magnetized plasmas, where electron cyclotron frequency fc is less than Langmuir frequency fL [1]. Similar mechanism is known to contribute the generation of RE in solar corona, as well as in magnetospheres of the Solar System planets [2,3]. It is a two-step process. At first, the plasma waves are excited due to Cherenkov instability in a weakly anisotropic background plasma by a small admixture of hot electrons with a loss-cone type non-equilibrium distribution function. Then, the electromagnetic radiation at fRE arises due to, e.g., plasma wave scattering on the background ions (Rayleigh scattering, fRE = fL), or nonlinear coupling of two plasma waves (Raman scattering, fRE = 2fL). In the first case, the maser effect at plasma frequency fL takes place under certain conditions, leading to an exponential grow of the RE intensity with the growing energy of plasma waves. In the case of Raman scattering of two plasma waves, resulting in generation of the RE at doubled plasma frequency, the maser effect is absent, but the collisional dissipation of RE is significantly reduced at the same time. This improves the requirements regarding the brightness temperature of the RE source, to provide a detectable on Earth radiation flux. In both cases the frequency band of the exoplanetary RE is defined not by magnetic field, but by the structure of planetary plasmasphere and density distribution there.We evaluate the efficiency of plasma mechanism of the RE generation and its detectability on Earth for the case of hot Jupiter HD189733b, for which the 3D structure of plasmasphere is simulated with the global multi-fluid self-consistent numerical model [4], taking into account the realistic stellar wind and radiation conditions. It is shown that the RE flux at doubled plasma frequency sharply increases from several mJy at 20MHz to several tens of Jy at 4 MHz. This means that the most favorable frequency range for detection of the RE from HD189733b falls into the decameter band in vicinity of the ionospheric cut-off.1. Zaitsev, V.V., Shaposhnikov, V.E., MNRAS, 2022, 513, 4082 (DOI:10.1093/mnras/stac1140)2. Zaitsev V. V., et al., A&A, 1986, 169, 345-354 (ISSN 0004-6361)3. Zlotnik E. Y., et al., JGR Space Physics, 2016, 121, 5307-5318 (DOI: 10.1002/2016JA02265)4. Rumenskikh, M. S., et al., ApJ, 2022, 927(2):238 (DOI: 10.3847/1538-4357/ac441d)

For the first time to solve the problems of laboratory modelling of cosmophysical phenomena of an explosive nature (active experiments of the AMPTE type, with barium injections into the magnetosphere), spherical laser plasma clouds (LPCs) were produced and applied (in experiments at the KI-1 test facility of the ILP SB RAS). Use was made of the classical four-beam scheme of irradiation (regular tetrahedron) of a polyethylene target ball (∅1 cm) by CO 2 laser radiation with an energy of up to 500 J. A high degree of symmetry of the expansion of a near-spherical LPC with a moderate velocity of ∼100 km s −1 and an energy of up to 30 J has been achieved. The regimes of deceleration and formation of the spherical-LPC diamagnetic cavity were modelled for the first time, as well as the development of flute instability during the expansion of barium clouds across the geomagnetic field and the dynamics of these clouds along the field.

ABSTRACT We simulate with a global 3D aeronomy code two warm Neptunes in the TOI-421 system and show that both planets experience significant escape of their upper atmospheres. The double shock structures, generated around the planets in course of their interaction with the stellar wind (SW) plasma flow are revealed. The calculations of stellar Ly α transit absorption by the planets reveal that it reaches a detectable level only for a moderate or strong SW, with a sufficiently high density. In this case, the energetic neutral atoms provide significant absorption at the high velocity blue wing of the Ly α line, whereas the corresponding transit light curves exhibit an early ingress and extended egress features. With the same code, we also modelled the absorption at the position of the 10 830 Å line of the metastable helium, showing that it can be detected only for the farthest planet of the considered two, if the helium abundance is comparable to the solar value.

Magnetospheres are formed when plasma flow interacts with an external source of the magnetic field. Objects (with a size comparable to or less than the ion inertial length or ion gyroradius) formed by relatively weak magnetic field sources are called minimagnetospheres since they are rather different from more common large planetary magnetospheres. Moon surface has regions called Lunar Magnetic Anomalies (LMAs) where the remanent magnetization of the Lunar crust provides sources of the magnetic field strong enough to stand off the solar wind. These fields produce minimagnetospheres of the size of the several ion inertial lengths (or gyroradii) or below, typically having weakly structured topology and mostly non-dipolar nature. In this study, we combine numerical simulations and laboratory experiments to investigate ion scattering and basic properties of a non-dipolar minimagnetosphere. A series of laboratory experiments were carried out on the KI-1 facility (Novosibirsk, Russia) to investigate minimagnetosphere properties for the case of a quadrupolar magnetic field source. The experiment consists of a vacuum chamber, of 5 m length and 1.2 m diameter (with a residual pressure of ~10-7 Torr) filled with a moving plasma. The quadrupolar magnetic field is generated by two coils connected in anti-parallel. The experimental results are supported by the Particle-in-Cell (PIC) three-dimensional simulations using code iPIC3D which capture the full kinetic behavior of the interaction. We report several important results based on both the experiment and numerical simulations: 1) a majority of particles is reflected by the Hall electric field formed due to the formation of the magnetopause electron current; however, a hotter portion of the inbound distribution also experiences magnetic deflection closer to the B field source; 2) reflecting electrostatic potential is smaller in the quadrupolar case (if compared to dipolar minimagnetosphere); 3) numerical simulations reproduce well the ion reflection pattern seen in the laboratory experiment, but simulations show slightly less reflected ions which might be attributed to unsteady processes developing during each laboratory run.

A 3D fully self-consistent multifluid hydrodynamic aeronomy model is applied to simulate the hydrogen-helium expanding upper atmosphere of the hot Jupiter HD189733b, and related absorption in the Ly alpha line and the 10830 angstrom line of metastable helium. We studied the influence of a high-energy stellar flux, a stellar wind, and Ly alpha cooling to reproduce the available observations. We found that to fit the width of the absorption profile of the 10830 angstrom line the escaping upper atmosphere of the planet should be close to the energy-limited escape achieved with significantly reduced Ly alpha cooling at the altitudes with an H i density higher than 3 x 10(6) cm(-3). Based on the performed simulations, we constrain the helium abundance in the upper atmosphere of HD189733b to be a rather low value of He/H similar to 0.005. We show that under the conditions of a moderate stellar wind similar to that of the Sun the absorption of the Ly alpha line takes place mostly within the Roche lobe due to thermal broadening at a level of about 7%. For an order of magnitude stronger wind, a significant absorption of about 15% at high blueshifted velocities of up to 100 km s(-1) is generated in the bowshock region, due to Doppler broadening. These blueshifted velocities are still lower than those (similar to 200 km s(-1)) detected in one of the observations. We explain the differences between the performed observations, though not in all of the details, by stellar activity and the related fluctuations of the ionizing radiation (in the case of the 10830 angstrom line), and the stellar wind (in the case of the Ly alpha line).