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Abstract A major challenge in understanding the process of nucleus-nucleus interactions is the examination of the processes that occur in the participant and spectator areas of interacting nuclei, considering the central nature of the reactions. Nearly thresholdless detection of the secondary charged particles is made possible by nuclear emulsion detectors (NED), which provide a complete 4πangular coverage. This work is mainly concerned with the multiplicity distributions (MD) and fluctuation of the average multiplicities of secondary charged particles (slow proton, fast proton, and shower) brought about by the collision of⁸⁴Kr-nuclei with emulsion nuclei at 1 A GeV. The MD of these particles has been computed by use of a modified cascade evaporation model (MCEM). The MD of each of the several charged secondary particles is correlated and analyzed. The observation demonstrates that the theoretical calculation results for the average multiplicities of shower particles, fast and slow protons agree well with the experimental data. Correlations seen experimentally between the multiplicities of different emitted particles are faithfully reproduced by the MCEM. There is good agreement between the experimental data and the theoretical calculation results.

A major challenge in understanding the process of nucleus-nucleus interactions is the examination of the processes that occur in the participant and spectator areas of interacting nuclei, considering the central nature of the reactions. Nearly thresholdless detection of the secondary charged particles is made possible by nuclear emulsion detectors (NED), which provide a complete 4π angular coverage. This work is mainly concerned with the multiplicity distributions (MD) and fluctuation of the average multiplicities of secondary charged particles (slow proton, fast proton, and shower) brought about by the collision of [Formula: see text]-nuclei with emulsion nuclei at 1 A GeV. The MD of these particles has been computed by use of a modified cascade evaporation model (MCEM). The MD of each of the several charged secondary particles is correlated and analyzed. The observation demonstrates that the theoretical calculation results for the average multiplicities of shower particles, fast and slow protons agree well with the experimental data. Correlations seen experimentally between the multiplicities of different emitted particles are faithfully reproduced by the MCEM. There is good agreement between the experimental data and the theoretical calculation results.

Nuclear fragmentation and its possible connection to a critical phenomenon or phase transition have been the subject of intense theoretical and experimental research on the interactivity of relativistic heavy nuclei. Relativistic heavy-ion collisions enable studies of the extended state of matter at density and temperature extremes only achieved in the hot early Universe. A significant barrier to knowing the mechanism of nucleus–nucleus interactions is the study of the processes that take place in the spectator and participant regions of interacting nuclei, and in particular, the interplay between these processes. In the present work, we have studied the multiplicity distribution of the slowest target fragments (black particles), and their dependence on the interaction of different target nuclei of emulsion. We have also study the correlation of the multiplicity distribution as a function of the collision geometry. The results are compared with other experimental data as per availability. This study reveals a striking relationship between the target fragmentation processes and collision geometry with multiplicity distributions.

Characterizing the plasma state in the near-Sun environment is essential to constrain the mechanisms that heat and accelerate the solar wind. In this study, we use Parker Solar Probe observations from Encounters 1 through 24 to investigate the radial evolution of solar wind plasma and magnetic field properties in this region. Using intervals with high field-of-view (>85%) coverage, we derive the radial profiles of magnetic field strength (∣B∣), proton density (N), bulk speed (V), total proton temperature (T), parallel (T∥) and perpendicular (T⊥) temperatures, temperature anisotropy (T⊥/T∥), plasma beta (β), Alfvén Mach number (MA), and magnetic field fluctuations (δB/B) for sub and super-Alfvénic regions. In super-Alfvénic regions, power laws of ∣B∣, N, V, and T as a function of the heliocentric distance are broadly consistent with previous Helios results at >0.3 au. The radial evolution of the components of the temperature tensor reveals distinct behavior: T⊥decreases monotonically with distance, whereas T∥ exhibits a nonmonotonic trend—decreasing in the sub-Alfvénic region, increasing just beyond the Alfvén surface. We interpret the increase in T∥ as a proxy for proton beam occurrence. We further examine the evolution of magnetic field fluctuations, finding decreasing radial/parallel fluctuations but enhanced tangential/normal/perpendicular fluctuations in the sunward direction. These fluctuations may provide free energy for beam generation and particle heating via wave–particle interactions.

Statistical classification of the Helios solar wind observations into several populations sorted by bulk speed has revealed an outward acceleration of the wind. The faster the wind, the smaller this acceleration in the 0.3–1 au radial range. In this paper, we show that recent measurements from the Parker Solar Probe (PSP) are compatible with an extension closer to the Sun of the latter Helios classification. For instance, the well-established bulk speed/proton temperature (u, T p) correlation and bulk speed/electron temperature (u, T e) anticorrelation, together with the acceleration of the slowest winds, are verified in PSP data. We also model the combined PSP and Helios data using empirical Parker-like models for which the solar wind undergoes an “isopoly” expansion: isothermal in the corona, then polytropic at distances larger than the sonic point radius. The polytropic indices are derived from the observed temperature and density gradients. Our modeling reveals that the electron thermal pressure has a major contribution in the acceleration process of slow and intermediate winds (in the range of 300–500 km s−1 at 1 au) over a broad range of distances and that the global (electron and proton) thermal energy alone is able to explain the acceleration profiles. Moreover, we show that the very slow solar wind requires, in addition to the observed pressure gradients, another source of acceleration.

A variety of energy sources, ranging from dynamic processes, such as magnetic reconnection and waves, to quasi-steady terms, such as plasma pressure, may contribute to the acceleration of the solar wind. We utilize a combination of charged particle and magnetic field observations from the Parker Solar Probe (PSP) to attempt to quantify the steady-state contribution of the proton pressure, the electric potential, and the wave energy to the solar wind proton acceleration observed by PSP between 13.3 and ∼100 solar radii (R ☉). The proton pressure provides a natural kinematic driver of the outflow. The ambipolar electric potential acts to couple the electron pressure to the protons, providing another definite proton acceleration term. Fluctuations and waves, while inherently dynamic, can act as an additional effective steady-state pressure term. To analyze the contributions of these terms, we utilize radial binning of single-point PSP measurements, as well as repeated crossings of the same stream at different distances on individual PSP orbits (i.e., fast radial scans). In agreement with previous work, we find that the electric potential contains sufficient energy to fully explain the acceleration of the slower wind streams. On the other hand, we find that the wave pressure plays an increasingly important role in the faster wind streams. The combination of these terms can explain the continuing acceleration of both slow and fast wind streams beyond 13.3 R ☉.

A rarefaction region (RR) occurs at the trailing edge of the fast solar wind stream. It comes from an area of small longitudinal extent on the solar surface and exhibits a fine and complex structure. In our study, we did a superposed epoch analysis of the proton and α parameters across the RR and observed their gradual evolution. We did not find any clear boundary between the fast and slow solar winds inside the RR because a majority of our observations show that most of the RR plasma corresponds to the fast solar wind; only the α–proton drift velocity decreases from the beginning of the RR. We investigate different ways of its reduction in interplanetary space and show that this feature is likely associated with the mirroring of the multicomponent solar wind. Nevertheless, considering the observed solar wind characteristics and taking into account the mutual relations between the proton and α parameters, we define the composition boundary where the α relative abundance and α–proton temperature ratio change abruptly from the values typical for the fast wind toward slow wind values. This boundary is the most probable candidate for the stream interface. Based on these findings, we speculate that the RR formation starts already near the Sun and formulate two possible scenarios.

In situ observations by Parker Solar Probe (PSP) suggest that the heliospheric current sheet (HCS) undergoes near-continuous magnetic reconnection close to the Sun, in stark contrast to scarce observations of this phenomenon in the HCS at 1 au. Situated at the boundary between sectors of opposite interplanetary magnetic field polarity, reconnection in the HCS has important consequences for magnetic topology and plasma dynamics in the slow solar wind. We report observations of a reconnection outflow in the HCS near the Alfvén transition region in PSP’s 17th solar encounter, featuring plasma jetting, proton temperature enhancement, and electron heat flux dropout. Embedded within the exhaust is a non-force-free flux rope plasmoid exhibiting counterstreaming strahl electrons, indicating connection at both ends to the Sun in an otherwise disconnected region of the magnetic field. The flux rope features diminished isotropic proton temperature and lower bulk speed compared to the remainder of the HCS exhaust. Its oblique orientation and different plasma properties imply that the flux rope originates from a different reconnection site to the HCS exhaust, suggesting PSP has intercepted a flux-rope-like streamer blob produced at the helmet streamer. Remote observations show several comparable blobs traveling in a distant coronal ray, demonstrating the possibility that the in situ flux rope is a streamer blob. The combination of in situ and remote observations demonstrates the role of magnetic reconnection in HCS dynamics, contributing to a growing understanding of this fundamental mechanism and its impact on the young solar wind.

The opening of the Torpedo CLC-0 chloride (Cl−) channel is known to be regulated by two gating mechanisms: fast gating and slow (common) gating. The structural basis underlying the fast-gating mechanism is better understood than that of the slow-gating mechanism, which is still largely a mystery. Our previous study on the intracellular proton (H+i)-induced inhibition of the CLC-0 anionic current led to the conclusion that the inhibition results from the slow-gate closure (also called inactivation). The conclusion was made based on substantial evidence such as a large temperature dependence of the H+i inhibition similar to that of the channel inactivation, a resistance to the H+i inhibition in the inactivation-suppressed C212S mutant, and a similar voltage dependence between the current recovery from the H+i inhibition and the recovery from the channel inactivation. In this work, we further examine the mechanism of the H+i inhibition of wild-type CLC-0 and several mutants. We observe that an anion efflux through the pore of CLC-0 accelerates the recovery from the H+i-induced inhibition, a process corresponding to the slow-gate opening. Furthermore, various inactivation-suppressed mutants exhibit different current recovery kinetics, suggesting the existence of multiple inactivated states (namely, slow-gate closed states). We speculate that protonation of the pore of CLC-0 increases the binding affinity of permeant anions in the pore, thereby generating a pore blockage of ion flow as the first step of inactivation. Subsequent complex protein conformational changes further transition the CLC-0 channel to deeper inactivated states.