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

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 modelof the interstellar hydrogen distribution in the heliosphere. We performed a fitting of the data to find independently the modelparameters: 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 byminimization of metricχ2. We also analysed temporal variations of the ratio of the fluxes measured in a fixed direction at energybin 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 incorrectseparation of the measured fluxes between energy channels in the data, or by some additional physical factors that are omitted inthe model. Understanding this issue may be important for the preparation of future Interstellar Mapping and Acceleration Probemission. At this stage, we relied on the sum of the fluxes measured in energy bins 1 and 2 for comparison to model predictions

Effect of the heliospheric interface on the distribution of interstellar hydrogen atom inside the heliosphere

This paper deals with the modeling of the interstellar hydrogen atoms (H atoms) distribution in the heliosphere. We study influence of the heliospheric interface, that is the region of the interaction between solar wind and local interstellar medium, on the distribution of the hydrogen atoms in vicinity of the Sun. The distribution of H atoms obtained in the frame of the self-consistent kinetic-gasdynamic model of the heliospheric interface is compared with a simplified model which assumes Maxwellian distribution of H atoms at the termination shock and is called often as 'hot' model. This comparison shows that the distribution of H atoms is significantly affected by the heliospheric interface not only at large heliocentric distances, but also in vicinity of the Sun at 1-5 AU. Hence, for analysis of experimental data connected with direct or undirect measurements of the interstellar atoms one necessarily needs to take into account effects of the heliospheric interface. In this paper we propose a new model that is relatively simple but takes into account all major effects of the heliospheric interface. This model can be applied for analysis of backscattered Ly-alpha radiation data obtained on board of different spacecraft.Comment: published in Astronomy Letter

Mechanisms in the pathogenesis of poststroke spasticity

Objective: to study the mechanisms of poststroke spasticity and the role of structural and functional impairments of skeletal muscles in its pathogenesis. Patients and methods. Thirty-two patients with prior hemispheric stroke and evolving spastic paresis were examined. Neurophysiological studies of upper and lower motor neuron functions and morphological, histochemical, and immunohistochemical studies of soleus muscle biopsy specimens were conducted. Results. There was diminished excitability of cortical neurons, impaired conduction along the pyramidal tracts, and hyperexcitability of the segmental apparatus of the spinal cord. The muscle exhibited myosin phenotype transformation with a preponderance of fast type II fibers, as well as a higher fiber diameter variability and a lower muscle tissue capillarization. The late periods of spasticity were marked by better conduction along the pyramidal tract, at the same time structural changes tended to increase in skeletal muscle tissue. The time course of the changes suggests that there is partial reversibility in the central nervous system and skeletal muscle, which allows elaboration of approaches to differentiated therapy for the above conditions