Об учете возмущения траектории КА солнечным ветром при численных расчетах межпланетного движения
In this work, we present for the first time the Lyman α intensities measured by Voyager 1/UVS in 2003–2014 (at 90–130 AU from the Sun). During this period Voyager 1 measured the Lyman α emission in the outer heliosphere at an almost fixed direction close to the upwind (i.e.“ toward the interstellar flow). The data show an unexpected behavior in 2003–2009: the ratio of observed intensity to the solar Lyman α flux is almost constant. Numerical modeling of these data is performed in the frame of a state-of-the-art self-consistent kinetic-MHD model of the heliospheric interface. The model results, for various interstellar parameters, predict a monotonic decrease of intensity not seen in the data. We propose two possible scenarios that explain the data qualitatively. The first is the formation of a dense layer of hydrogen atoms near the heliopause. Such a layer would provide an additional backscattered Doppler-shifted Lyman α emission, which is not absorbed inside the heliosphere and may be observed by Voyager. About 35 R of intensity from the layer is needed. The second scenario is an external nonheliospheric Lyman α component, which could be galactic or extragalactic. Our parametric study shows that ∼25 R of additional emission leads to a good qualitative agreement between the Voyager 1 data and the model results.
We investigate quasi-adiabatic dynamics of charged particles in strong current sheets (SCSs) in the solar wind, including the heliospheric current sheet (HCS), both theoretically and observationally. A self-consistent hybrid model of an SCS is developed in which ion dynamics is described at the quasi-adiabatic approximation, while the electrons are assumed to be magnetized, and their motion is described in the guiding center approximation. The model shows that the SCS profile is determined by the relative contribution of two currents: (i) the current supported by demagnetized protons that move along open quasi-adiabatic orbits, and (ii) the electron drift current. The simplest modeled SCS is found to be a multi-layered structure that consists of a thin current sheet embedded into a much thicker analog of a plasma sheet. This result is in good agreement with observations of SCSs at ∼1 au. The analysis of fine structure of different SCSs, including the HCS, shows that an SCS represents a narrow current layer (with a thickness of ∼104 km) embedded into a wider region of about 105 km, independently of the SCS origin. Therefore, multi-scale structuring is very likely an intrinsic feature of SCSs in the solar wind.
Fluxes of energetic protons in the range from 30 keV up to several MeV measured at the Voyager 1/2spacecraft downstream of the heliospheric termination shock can be explained by shock-drift acceleration theory, which includes variations of the magnetic field direction in a vicinity of the shock. The variations can be connected with the sector structure of the interplanetary magnetic field near the solar equatorial plane. Theoretical fluxes of accelerated protons are calculated numerically in the framework of a 3D kinetic-magnetohydrodynamic model of the interaction of the solar wind and local interstellar medium.
In framework of the feasibility studies for the Venus-D project several options for placing a spacecraft in a low orbit near a planet orbit were studied.
The goal of these studies is to determine the optimal variant of spacecraft delivery into a near-Venus orbit. The criterion of optimization is the payload mass.
Several scenarios of transfer from interplanetary orbit onto low Venus orbit are considered beginning from the classical method of applying a rocket engine velocity impulse. As an alternative concept the direct entry into atmosphere is analyzed supposing that after atmospheric drag deceleration the spacecraft leaves the atmosphere, achieving an orbit with apocenter above the atmosphere and pericenter below the planet’s surface. By applying appropriate velocity impulses, the spacecraft is finally transferred into low orbit. The problem of optimal control of aerodynamic forces during this maneuver is solved. It is supposed that the lift force during aerobraking maneuver changes its direction by rotating the spacecraft about its longitudinal axis.
Also intermediate methods to reach low orbit are analyzed when initially the spacecraft is transferred into a high elliptical orbit by engine impulse and by later successive comparatively small aerobraking maneuvers. The maximum overload during these maneuvers is determined by the maximum allowed temperature on the surface of the heat shield of the spacecraft.
Comparison of the described methods is presented taking into account the payload mass, technical risks and overall duration of maneuvers.