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Измоденов Владислав Валерьевич

Базовая кафедра физики космоса Института космических исследований РАН

Профиль на hse.ru ↗ тел.: 15250
Публикаций
42
Языков
1
Наград
3
Конференций
0
Профиль Публикации (42) Курсы (4)

Профессиональные интересы

космическая газовая динамикаФизика плазмымагнитная гидродинамикагелиосферамежзвездная средаастросферыкинетическая теория газов

Должности

  • Профессор — Базовая кафедра физики космоса Института космических исследований РАН

Био

  • · Начал работать в НИУ ВШЭ в 2017 году.
  • · Научно-педагогический стаж: 31 год.

Образование

  • 2008 · Доктор физико-математических наук
  • 1993 · Специалитет: Московский государственный университет им. М.В. Ломоносова, специальность «Механика, прикладная математика», квалификация «Механик»

Опыт работы

  • · 1997 г.: С июля работает на механико-математическом факультете МГУ в должности младшего научного сотрудника, ассистента (с
  • · 1998 г: ), доцента (с
  • · 2002 г.: по
  • · 2010 г: ), профессора (с
  • · 2011 г.: по наст. время)
  • · 2005 г.: С по настоящее время работает в Институте космических исследований РАН заведующим лабораторией (по совмест.) «Межпланетной среды» отдела физики планет и малых тел солнечной системы

Награды и поощрения

  • · Благодарность факультета физики НИУ ВШЭ (ноябрь 2022)
  • · Надбавка за публикацию в журнале из Списка А (и приравненном к нему научном издании) (2025–2026, 2024–2025, 2023–2024)
  • · Надбавка за публикацию в международном рецензируемом научном издании (2022–2023, 2021–2022, 2019–2021, 2018–2019)

Гранты и проекты

  • — · на соискание учёной степени кандидата наук

Идентификаторы исследователя

Публикации (42)

Dust in and Around the Heliosphere and Astrospheres

2022 · ARTICLE · en

Interstellar dust particles were discovered in situ, in the solar system, with the Ulyssesmission’s dust detector in 1992. Ever since, more interstellar dust particles have been measured inside the solar system by various missions, providing insight into not only the composition of such far-away visitors, but also in their dynamics and interaction with the heliosphere. The dynamics of interstellar (and interplanetary) dust in the solar/stellar systems depend on the dust properties and also on the space environment, in particular on the heliospheric/astrospheric plasma, and the embedded time-variable magnetic fields, via Lorentz forces. Also, solar radiation pressure filters out dust particles depending on their composition. Charge exchanges between the dust and the ambient plasma occur, and pick-up ions can be created. The role of the dust for the physics of the heliosphere and astrospheres is fairly unexplored, but an important and a rapidly growing topic of investigation. This review paper gives an overview of dust processes in heliospheric and astrospheric environments, with its resulting dynamics and consequences. It discusses theoretical modeling, and reviews in situ measurements and remote sensing of dust in and near our heliosphere and astrospheres, with the latter being a newly emerging field of science. Finally, it summarizes the open questions in the field.

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Imprints of the secondary interstellar hydrogen atoms at 1 AU

2021 · ARTICLE · en

In this paper, we search for the possible imprints of the secondary interstellar hydrogen atoms created at the heliospheric boundary in the full-sky maps of the hydrogen fluxes at the Earth orbit. By using our three-dimensional time-dependent kinetic model, the maps of the hydrogen fluxes are calculated for different phases of the solar cycle and different energy ranges. It is shown that the flux maps obtained during the solar minimum conditions for the energy range 1–20 eV have specific features such as blobs and tails, which are pronounced due to a signal of the secondary component of the interstellar atoms. We investigate how these features depend on parameters of the secondary atoms far away from the Sun and found that the geometry and shape of the tails depend on the averaged velocity and kinetic temperatures of the secondary population. The results of the paper provide a strategy where and when we need to look in order to detect the secondary component of the interstellar hydrogen separately from the primary component at 1 AU. This can be important for future space missions devoted to the exploration of the heliospheric boundary.

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Влияние дисперсии скоростей пыли в межзвездной среде на ее распределение внутри гелиосферы

2021 · ARTICLE · ru

Межзвездная пыль проникает в гелиосферу из-за относительного движения Солнца в локальной межзвездной среде. На частицы межзвездной пыли в гелиосфере действуют электромагнитные силы, сила гравитационного притяжения и сила радиационного давления. Внутри гелиосферы и на ее границах, где солнечный ветер взаимодействует с плазмой межзвездной среды, распределение частиц межзвездной пыли меняется из-за действия этих сил и становится существенно неоднородным. В нашей предыдущей работе было продемонстрировано существование особенностей в распределении концентрации межзвездной пыли на расстоянии ∼0.03–10 а.е. от плоскости гелиосферного токового слоя. В настоящей статье исследуется влияние дисперсии в распределении частиц межзвездной пыли по скоростям и показано, что она сильно влияет на упомянутые особенности в распределении концентрации. Даже относительно небольшие величины дисперсии оказывают значительное влияние на распределение концентрации и сглаживают области повышенной концентрации, обнаруженные ранее.

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New unexpected flow patterns in the problem of the stellar wind interaction with the interstellar medium: stationary ideal-MHD solutions

2021 · ARTICLE · en

The astropause (heliopause for the Sun) is the tangential discontinuity separating the stellar wind from the interstellar plasma. The global shape of the heliopause is a matter of debates. Two types of the shape are under discussion: comet-like and tube-like. In the second type, the two-jets oriented towards the stellar rotation axis are formed by the action of azimuthal component of the stellar magnetic field. We explore a simplified global astrosphere in which (1) the surrounding and moving with respect to the star circumstellar medium is fully ionized, (2) the interstellar magnetic field is neglected, (3) the radial component of the stellar magnetic field is neglected as compared with the azimuthal component, and (4) the stellar wind outflow is spherically symmetric and supersonic. We present the results of numerical 3D MHD modelling and explore how the global structure depends on the gas-dynamic Mach number of the interstellar flow, M∞, and the Alfvenic Mach number in the stellar wind. It is shown that the astropause has a tube-like shape for small values of M∞. The wings of the tube are distorted towards the tail as larger as larger the Mach number is. The new (to our knowledge) result is the reverse interstellar flow in the vicinity of the astropause in the tail. The larger the interstellar Mach number is the narrower the reverse flow is. At some values of the Mach number, the stellar wind overcomes the reverse interstellar flow and moves out in downwind. In this regime, the astropause changes its topology from tube-like to sheet-like.

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Analysis of the IBEX-Lo interstellar hydrogen fluxes collected in 2009-2018 as a tool for sensing of the solar radiation pressure and the hydrogen ionization rate

2021 · ARTICLE · en

The Interstellar Boundary Explorer (IBEX) has been measuring interstellar hydrogen fluxes at 1 au since 2009. In this paper, we analysed all available data obtained with the IBEX-Lo instrument at energies 11-41 eV using our numerical kinetic model of the interstellar hydrogen distribution in the heliosphere. We performed a fitting of the data to find independently the model parameters: the ratio of the solar radiation pressure to the solar gravitation (μ0), ionization rate of hydrogen atoms at 1 au (β0), parameters of the secondary interstellar atoms at 70 au from the Sun, which provide the best agreement with the data by minimization of metric χ2. We also analysed temporal variations of the ratio of the fluxes measured in a fixed direction at energy bin 1 and energy bin 2. It is found that in 2009-2011 and 2017-2016 the ratio provided by the model is smaller than in the IBEX-Lo data, while in 2012-2015, oppositely, the model ratio is larger compared to the data. This might be caused by the incorrect separation of the measured fluxes between energy channels in the data, or by some additional physical factors that are omitted in the model. Understanding this issue may be important for the preparation of future Interstellar Mapping and Acceleration Probe mission. At this stage, we relied on the sum of the fluxes measured in energy bins 1 and 2 for comparison to model predictions.

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Effects of radiative energy losses on the structure of stellar wind interaction with the interstellar medium

2021 · ARTICLE · en

We present two-dimensional axisymmetric gas dynamic simulations of the hypersonic stellar wind interaction with the surrounding interstellar medium moving with supersonic speed in the stellar rest frame. Our model takes into account radiative losses that appear in optically thin plasma. We aim to explore the influence of radiative cooling on the size and global shapes of astrospheres. It is demonstrated in the paper that solution depends on five dimensionless parameters: 𝛾 (the adiabatic index), 𝑀∞ (the Mach number in the undisturbed interstellar medium), 𝜒 (the ratio between terminal speed and interstellar medium speed), as well as 𝛼 and 𝜃 which are related to the energy losses; 𝛼 is responsible for radiative cooling power, 𝜃 is the interstellar medium temperature divided by 104 K. Results of the simulations demonstrate that radiative losses have a significant influence on the flow pattern. The process of radiative cooling leads to an increase of density and pressure which results in compression of the interaction region and changing the position of the astropause. We also explore the growth of Kelvin-Helmholtz instability appearing at tangential discontinuities with increasing cooling power 𝛼.

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Modelling of the interstellar dust distribution under the influence of the interstellar magnetic field

2021 · ARTICLE · en

Due to the relative motion of the Sun, the interstellar dust (ISD) particles can penetrate into the heliosphere. Three main forces influence the ISD motion in the heliosphere and near its boundaries: the solar gravitational force, the radiation pressure force and the electromagnetic force. Our general goal is to create a model of the ISD distribution in the heliosphere and, particularly, find regions of the increased ISD number density. In our previous works ([13], [3]) we investigated the peculiarities of the ISD distribution in the heliosphere/astrospheres and the effects of velocity dispersion on these peculiarities. Here we study the influence of the interstellar magnetic field on the ISD distribution in the outer heliospheric interface. For this purpose, we also calculate the electric charge of the ISD particles, which depends mainly on the currents of surrounding plasma ions and electrons, secondary emitted electrons and photoelectrons. We demonstrate the filtration of the ISD particles in the vicinity of the heliopause: small ISD particles align along the lines of the interstellar magnetic field and don’t penetrate into the heliosphere and, on the contrary, the interstellar magnetic field almost doesn’t affect the motion of big ISD particles. We also show that regions of the increased ISD number density appear in the vicinity of the heliopause and discuss mechanisms of their origin.

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Signature of a Heliotail Organized by the Solar Magnetic Field and the Role of Nonideal Processes in Modeled IBEX ENA Maps: A Comparison of the BU and Moscow MHD Models

2021 · ARTICLE · en

Energetic neutral atom (ENA) models typically require post-processing routines to convert the distributions of plasma and H atoms into ENA maps. Here we investigate how two kinetic-MHD models of the heliosphere (the BU and Moscow models) manifest in modeled ENA maps using the same prescription and how they compare with Interstellar Boundary Explorer (IBEX) observations. Both MHD models treat the solar wind as a single-ion plasma for protons, which include thermal solar wind ions, pick-up ions (PUIs), and electrons. Our ENA prescription partitions the plasma into three distinct ion populations (thermal solar wind, PUIs transmitted and ones energized at the termination shock) and models the populations with Maxwellian distributions. Both kinetic-MHD heliospheric models produce a heliotail with heliosheath plasma that is organized by the solar magnetic field into two distinct north and south columns that become lobes of high mass flux flowing down the heliotail; however, in the BU model, the ISM flows between the two lobes at distances in the heliotail larger than 300 au. While our prescription produces similar ENA maps for the two different plasma and H atom solutions at the IBEX-Hi energy range (0.5–6 keV), the modeled ENA maps require a scaling factor of ∼2 to be in agreement with the data. This problem is present in other ENA models with the Maxwellian approximation of multiple ion species and indicates that either a higher neutral density or some acceleration of PUIs in the heliosheath is required.

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The Development of a Split-tail Heliosphere and the Role of Non-ideal Processes: A Comparison of the BU and Moscow Models

2021 · ARTICLE · en

Global models of the heliosphere are critical tools used in the interpretation of heliospheric observations. There are several three-dimensional magnetohydrodynamic (MHD) heliospheric models that rely on different strategies and assumptions. Until now only one paper has compared global heliosphere models, but without magnetic field effects. We compare the results of two different MHD models, the BU and Moscow models. Both models use identical boundary conditions to compare how different numerical approaches and physical assumptions contribute to the heliospheric solution. Based on the different numerical treatments of discontinuities, the BU model allows for the presence of magnetic reconnection, while the Moscow model does not. Both models predict collimation of the solar outflow in the heliosheath by the solar magnetic field and produce a split tail where the solar magnetic field confines the charged solar particles into distinct north and south columns that become lobes. In the BU model, the interstellar medium (ISM) flows between the two lobes at large distances due to MHD instabilities and reconnection. Reconnection in the BU model at the port flank affects the draping of the interstellar magnetic field in the immediate vicinity of the heliopause. Different draping in the models cause different ISM pressures, yielding different heliosheath thicknesses and boundary locations, with the largest effects at high latitudes. The BU model heliosheath is 15% thinner and the heliopause is 7% more inwards at the north pole relative to the Moscow model. These differences in the two plasma solutions may manifest themselves in energetic neutral atom measurements of the heliosphere.

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Современный взгляд на солнечный ветер от микро- до макромасштабов

2020 · ARTICLE · ru

Солнечный ветер — поток плазмы, истекающий из солнечной короны, интересен и как переносчик солнечной активности, и как пример бесстолкновительной плазмы. Приведены основные результаты российских исследований последних лет. Оригинальная МГД-модель позволила интерпретировать раздвоение гелиосферного токового слоя в годы максимума активности как обусловленное квадрупольной компонентой гелиомагнитного поля. На масштабах порядка миллионов километров солнечный ветер состоит из солнечных транзиентных образований. В этой части решена одна из фундаментальных проблем, обеспечивающих геомагнитный прогноз, — показано, что можно предполагать стабильность межпланетного магнитного поля на временах около трёх часов. На малых масштабах (сотни—тысячи километров) формируются локальные структуры, которые могут быть рассмотрены и индивидуально, и статистически, в рамках турбулентного каскада.

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Курсы (4)