Wind Acceleration Research Articles

ATOMIUM: ALMA tracing the origins of molecules in dust forming oxygen rich M-type stars

This overview paper presentsATOMIUM, a Large Programme in Cycle 6 with the Atacama Large Millimeter/submillimeter Array (ALMA). The goal ofATOMIUMis to understand the dynamics and the gas phase and dust formation chemistry in the winds of evolved asymptotic giant branch (AGB) and red supergiant (RSG) stars. A more general aim is to identify chemical processes applicable to other astrophysical environments. Seventeen oxygen-rich AGB and RSG stars spanning a range in (circum)stellar parameters and evolutionary phases were observed in a homogeneous observing strategy allowing for an unambiguous comparison. Data were obtained between 213.83 and 269.71 GHz at high (∼0″​​.025–0″​​.050), medium (∼0″​​.13–0″​​.24), and low (∼1″) angular resolution. The sensitivity per ∼1.3 km s−1channel was 1.5–5 mJy beam−1, and the line-free channels were used to image the millimetre wave continuum. Our primary molecules for studying the gas dynamics and dust formation are CO, SiO, AlO, AlOH, TiO, TiO2, and HCN; secondary molecules include SO, SO2, SiS, CS, H2O, and NaCl. The scientific motivation, survey design, sample properties, data reduction, and an overview of the data products are described. In addition, we highlight one scientific result – the wind kinematics of theATOMIUMsources. Our analysis suggests that theATOMIUMsources often have a slow wind acceleration, and a fraction of the gas reaches a velocity which can be up to a factor of two times larger than previously reported terminal velocities assuming isotropic expansion. Moreover, the wind kinematic profiles establish that the radial velocity described by the momentum equation for a spherical wind structure cannot capture the complexity of the velocity field. In fifteen sources, some molecular transitions other than12COv = 0J = 2 − 1 reach a higher outflow velocity, with a spatial emission zone that is often greater than 30 stellar radii, but much less than the extent of CO. We propose that a binary interaction with a (sub)stellar companion may (partly) explain the non-monotonic behaviour of the projected velocity field. TheATOMIUMdata hence provide a crucial benchmark for the wind dynamics of evolved stars in single and binary star models.

Testing the Alfvén-wave Model of the Solar Wind with Interplanetary Scintillation

Abstract Understanding the mechanism(s) of solar wind acceleration is important in astrophysics and geophysics. A promising model of solar wind acceleration is known as the wave/turbulence-driven (WTD) model, in which Alfvén waves feed energy to the solar wind. In this study, we tested the WTD model with global measurements of wind speed from interplanetary scintillation (IPS) observations. For Carrington rotations in minimal and maximal activity phases, we selected field lines calculated by the potential-field source-surface method in high and midlatitudes and compared the simulated and observed wind velocities. The simulation was performed in a self-consistent manner by solving the magnetohydrodynamic equations from the photosphere to the solar wind. In high-latitude regions, the simulated solar wind velocity agrees better with the IPS observation than with the classical Wang–Sheeley empirical estimation, both in maximal and minimal activity phases. In midlatitude regions, the agreement worsens, possibly because of the inaccuracy of the WTD model and/or the magnetic-field extrapolation. Our results indicate that the high-latitude solar wind is likely to be driven by waves and turbulence and that the physics-based prediction of the solar wind velocity is highly feasible with an improved magnetic-field extrapolation.

The Zonal Wind Intraseasonal Oscillation in the Exit Region of the East Asian Subtropical Westerly Jet in Winter and Its Thermodynamic Mechanism

The six-hourly ERA-interim reanalysis data were used to analyze the intraseasonal oscillation (ISO) characteristics of the zonal wind in the exit region of the East Asian subtropical westerly jet (EAJ) during the winter (November to April). The results indicate that from East Asia to the North Pacific, the zonal wind in the upper troposphere shows significant 10–40-day oscillations, propagating eastward toward the jet exit region. The strength of the intraseasonal zonal wind anomaly increases from the lower troposphere to the upper troposphere, reaching a peak between 300 and 200 hPa. The zonal wind ISO in the jet exit area is closely related to the intraseasonal inverse temperature tendency between the north and south of the jet exit in the troposphere. In the acceleration (deceleration) phase of the intraseasonal west wind, the air temperature decreases (increases) in the north of the exit and increases (decreases) in the south of the exit. The intraseasonal temperature tendency is stronger in the north of the EAJ exit than that in the south. In the north of the EAJ exit, the intraseasonal temperature tendency is decided by the temperature advection, where the whole troposphere is controlled by the north wind in the west wind acceleration phase and controlled by the south wind in the west wind deceleration phase, so the intensity of temperature advection is strong. However, adiabatic heating plays a decisive role in affecting the temperature evolution in the south of the jet exit area, and the intraseasonal meridional wind is the opposite between the mid-upper troposphere and the lower troposphere, resulting in weak temperature advection and the weak temperature tendency. Therefore, although the zonal wind ISO in the jet exit area is the result of the joint action of the ISOs in different latitudes, the influence of mid-high latitudes is particularly important.

Solar Jets: SDO and IRIS Observations in the Perspective of New MHD Simulations

Solar jets are observed as collimated plasma beams over a large range of temperatures and wavelengths. They have been observed in H α and optical lines for more than 50 years and called surges. The term “jet” comes from X-ray observations after the launch of the Yohkoh satellite in 1991. They are the means of transporting energy through the heliosphere and participate to the corona heating and the acceleration of solar wind. Several characteristics have been derived about their velocities, their rates of occurrence, and their relationship with CMEs. However, the initiation mechanism of jets, e.g. emerging flux, flux cancellation, or twist, is still debated. In the last decade coordinated observations of the Interface Region Imaging Spectrograph (IRIS) with the instruments on board the Solar Dynamic Observatory (SDO) allow to make a step forward for understanding the trigger of jets and the relationship between hot jets and cool surges. We observe at the same time the development of 2D and 3D MHD numerical simulations to interpret the results. This paper summarizes recent studies of jets showing the loci of magnetic reconnection in null points or in bald patch regions forming a current sheet. In the pre-jet phase a twist is frequently detected by the existence of a mini filament close to the dome of emerging flux. The twist can also be transferred to the jet from a flux rope in the vicinity of the reconnection by slippage of the polarities. Bidirectional flows are detected at the reconnection sites. We show the role of magnetic currents detected in the footprints of flux rope and quasi-separatrix layers for initiating the jets. We select a few studies and show that with the same observations, different interpretations are possible based on different approaches e.g. non linear force free field extrapolation or 3D MHD simulation.

Alpha–Proton Differential Flow of the Young Solar Wind: Parker Solar Probe Observations

Abstract The velocity of alpha particles relative to protons can vary depending on the solar wind type and distance from the Sun. Measurements from the previous spacecraft provided the alpha–proton differential velocities down to 0.3 au. The Parker Solar Probe (PSP) now enables insights into differential flows of the newly accelerated solar wind closer to the Sun for the first time. Here we study the difference between proton and alpha bulk velocities near PSP perihelia of encounters 3–7 when the core solar wind is in the field of view of the Solar Probe Analyzer for Ions instrument. As previously reported at larger heliospheric distances, the alpha–proton differential speed observed by PSP is greater for fast wind than the slow solar wind. We compare PSP observations with various spacecraft measurements and present the radial and temporal evolution of the alpha–proton differential speed. The differential flow decreases as the solar wind propagates from the Sun, consistent with previous observations. While Helios showed a small radial dependence of differential flow for the slow solar wind, PSP clearly showed this dependency for the young slow solar wind down to 0.09 au. Our analysis shows that the alpha–proton differential speed’s magnitude is mainly below the local Alfvén speed. Moreover, alpha particles usually move faster than protons close to the Sun. The PSP crossed the Alfvén surface during its eighth encounter and may cross it in future encounters, enabling us to investigate the differential flow very close to the solar wind acceleration source region for the first time.

Kelvin Wave and Its Impact on the Venus Atmosphere Tested by Observing System Simulation Experiment

At the cloud top of the Venus atmosphere, equatorial Kelvin waves have been observed and are considered to play an important role in the super-rotation. We were able to reproduce the wave in a general circulation model (GCM) by conducting an observing system simulation experiment (OSSE) with the help of a data assimilation system. The synthetic horizontal winds of the Kelvin wave produced by the linear wave propagating model are assimilated at the cloud top (~70 km) in realistic conditions, assuming they are obtained from cloud tracking of ultra-violet images (UVI) taken by the Venus orbiters. It is demonstrated using Eliassen–Palm (EP) fluxes that the reproduced Kelvin wave transports angular momentum and plays an important role in the magnitude and structure of the super-rotation, causing the acceleration and deceleration of zonal wind of ~0.1 m/s day−1. The conditions required in order to reproduce the Kelvin wave have also been investigated. It is desirable to have 24 hourly dayside satellite observations in an equatorial orbit, such as the Akatsuki Venus climate orbiter. The results of this type of data assimilation study will be useful in the planning of future observation missions to the atmospheres of planets.

A study on the solar coronal dynamics during the post-maxima phase of the solar cycle 24 using S-band radio signals from the Indian Mars Orbiter Mission

ABSTRACT Radio signals from India’s Mars Orbiter Mission (MOM) have been used to study turbulence in the solar plasma during the post-maximum phase of solar cycle 24. S-band (2.29 GHz) radio carrier downlink signals from MOM were received at the Indian Deep Space Network, Bangalore, and frequency residuals were spectrally analysed to obtain coronal turbulence spectra at heliocentric distances ranging between 4 and 20 R⊙, corresponding to coronal regions where the solar wind is primarily accelerated. The frequency fluctuation spectrum relates to the turbulence regime in the near-Sun region. The turbulence power spectrum (the temporal spectrum of frequency fluctuations) at smaller heliocentric distances (<10 R⊙) reveals flattening in lower-frequency regions, with a spectral index αf ∼ 0.3−0.5, which corresponds to the solar wind acceleration region. For larger heliocentric distances (>10 R⊙), the curve steepens with a spectral index αf ∼ 0.7−0.8, a value close to 2/3 and indicative of a developed Kolmogorov-type turbulence spectrum. The findings are consistent with earlier results. Plausible explanations to support the theory of coronal heating by magnetohydrodynamic waves and the acceleration of the solar wind are presented. An insight into the feeble maximum of solar cycle 24 is discussed.

Thunderstorm-induced mean wind velocities and accelerations through the continuous wavelet transform

By analysing a set of thunderstorm-induced events acquired on the Italian north-west coast, the separation of the relevant wind velocity signals into a time-varying mean and a residual fluctuation is considered. It is assumed that, within a structural design process, the former is used for a quasi-steady evaluation of the aerodynamic loads and the latter to estimate the dynamic response. A procedure based on the continuous wavelet transform is proposed to obtain the time-varying mean velocity and its outcomes are compared with those of different moving average techniques. The wavelet filtering appears to provide a time-varying mean that better describes the main time variations of the original velocity signals; a decrease of the correlation between mean and residual velocities is also found. The derivative of the time-varying mean wind speed leads to a time-varying mean acceleration, whose characteristics and possible role in a design process are discussed. An estimate of the acceleration-induced contribution to the aerodynamic loads on a slender body is also carried out through the Morison equation. The force term directly related to acceleration is shown to generally have a limited influence on the total design loads, except for bodies that are considerably elongated in the flow direction.

On the solar dynamics from radio signal communication by recent solar probes

The very inquisition of the humanity always remains about its parent star of this planetary system. Scientists across the world are always egger to investigate the details of the phenomenon of the solar flares and coronal mass ejections (CMEs). There are some fundamental mysteries related to the solar coronal heating along with the acceleration of the solar wind and energetic particles. In this context we have discussed on the solar radio signal data obtained from the Parker Solar Probe (PSP) mission of National Aeronautics and Space Administration (NASA), USA in course of its journey towards the Sun and the very recent data of Solar and Heliospheric Observatory (SOHO) space probe of European Space Agency (ESA) and NASA. In this work the simultaneous and periodical analysis of the data from the SOHO and PSP will light into the delicate features of the near and far Earth observations on the solar coronal mass ejections related dynamics and that reveals some interesting facts in relation to the solar magnetic field.

Feasibility analysis of novel aerodynamic braking system for horizontal axis wind turbines

Wind energy is an eco-friendly, highly potential and sustainable energy to meet the growing demand for the energy. Wind turbine farms are set-up in the wind potential areas to generate electricity. The wind turbines are designed to function at a rated rpm. The unexpected wind acceleration and high-speed wind drastically increases the wind turbine rotor speed and damage the mechanical drive train shaft, gear box and turbine blade. The control systems are used to control the over speeding of the wind turbine at extreme wind velocity. In this novel methodology it is attempted to manage the rotational speed of the wind turbine aerodynamically by facilitating the chordwise slot or spacing over the wind turbine blade. The slot which is facilitated over the blade alters the pressure distribution between the upper side and lower side of the turbine blade that controls the rotational speed of the wind turbine rotor within the allowable limit. In this approach, the over speeding of the wind turbine blades is effectively controlled without affecting the power generation. Various parameters of the slot or spacing influences the effectiveness of the braking system. In this work, the length of the spacing on the wind turbine blade experimentally optimized.

Coronal Density Measurements Using Giant Radio Pulses of the Crab Pulsar at the Cycle 24/25 Minimum

Accurate measurements of the coronal plasma density profile, which varies with the solar cycle (SC), are necessary to elucidate the solar wind acceleration. In this study, the Crab pulsar is observed using the 327 MHz radio telescope at the Toyokawa Observatory of the Institute for Space-Earth Environmental Research of Nagoya University to investigate the coronal plasma density profile for radial distances between 5 and 60 solar radii at the SC24/25 minimum. We derive the dispersion measures (DMs) that represent the integration of plasma density along the line of sight (LOS) for giant radio pulses of the Crab pulsar. We find that the observed DMs increased above the interstellar background level when the LOS for the Crab pulsar approached the Sun in mid-June 2018 and 2019. This increase in DM is attributed to the effect of the coronal plasma. We determine the plasma density distribution by fitting a spherically symmetric model to the observed DM data. The flat radial slopes of the best-fit model are consistent with pulsar observations in the low-activity periods of past SCs, and they are attributed to the effect of the coronal hole over the south pole of the Sun. Our results show that the density level near the Sun is similar to those observed in the low activity periods of past SCs, implying recovery of the coronal plasma density from a significant reduction at the SC23/24 minimum.

Investigation of Sea Spray Effect on the Vertical Momentum Transport Using an Eulerian Multifluid-Type Model

Abstract The Eulerian multifluid mathematical model is developed to describe the marine atmospheric boundary layer laden with sea spray under the high-wind condition of a hurricane. The model considers spray and air as separate continuous interacting turbulent media and employs the multifluid E–ϵ closure. Each phase is described by its own set of coupled conservation equations and characterized by its own velocity. Such an approach enables us to accurately quantify the interaction between spray and air and pinpoint the effect of spray on the vertical momentum transport much more precisely than could be done with traditional mixture-type approaches. The model consistently quantifies the effect of spray inertia and the suppression of air turbulence due to two different mechanisms: the turbulence attenuation, which results from the inability of spray droplets to fully follow turbulent fluctuations, and the vertical transport of spray against the gravity by turbulent eddies. The results of numerical and asymptotic analyses show that the turbulence suppression by spray overpowers its inertia several meters above wave crests, resulting in a noticeable wind acceleration and the corresponding reduction of the drag coefficient from the reference values for a spray-free atmosphere. This occurs at much lower than predicted previously spray volume fraction values of ∼10−5. The falloff of the drag coefficient from its reference values is more strongly pronounced at higher altitudes. The drag coefficient reaches its maximum at spray volume fraction values of ∼10−4, which is several times smaller than predicted by mixture-type models.

Supernovae in colliding-wind binaries: observational signatures in the first year

ABSTRACT When a core-collapse supernova (SN) explodes in a binary star system, the ejecta might encounter an overdense shell, where the stellar winds of the two stars previously collided. In this work, we investigate effects of such interactions on SN light curves on time-scales from the early flash ionization signatures to approximately one year after the explosion. We construct a model of the colliding-wind shell in an orbiting binary star system and we provide an analytical expression for the shell thickness and density, which we calibrate with three-dimensional adaptive mesh refinement hydrodynamical simulations probing different ratios of wind momenta and different regimes of radiative cooling efficiency. We model the angle-dependent interaction of SN ejecta with the circumstellar medium and estimate the shock radiative efficiency with a realistic cooling function. We find that the radiated shock power exceeds typical Type IIP SN luminosity only for double red supergiant binaries with mass ratios q ≳ 0.9, wind mass-loss rates $\dot{M}\gtrsim 10^{-4}\, \rm M_\odot \, \text{yr}^{-1}$, and separations between about 50 and 1500 au. The required $\dot{M}$ increases for binaries with smaller q or primaries with faster wind. We estimate that ≪1 per cent of all collapsing massive stars satisfy the conditions on binary mass ratio and separation. Recombination luminosities due to colliding wind shells are at most a factor of 10 higher than for an otherwise unperturbed constant-velocity wind, but higher densities associated with wind acceleration close to the star provide much stronger signal.

On the fragility of Alfvén waves in a stratified atmosphere

ABSTRACTComplete asymptotic expansions are developed for slow, Alfvén, and fast magnetohydrodynamic waves at the base of an isothermal 3D plane stratified atmosphere. Together with existing convergent Frobenius series solutions about z = ∞, matchings are numerically calculated that illuminate the fates of slow and Alfvén waves injected from below. An Alfvén wave in a two-dimensional model is 2.5D in the sense that the wave propagates in the plane of the magnetic field but its polarization is normal to it in an ignorable horizontal direction, and the wave remains an Alfvén wave throughout. The rotation of the plane of wave propagation away from the vertical plane of the magnetic field pushes the plasma displacement vector away from horizontal, thereby coupling it to stratification. It is shown that potent slow–Alfvén coupling occurs in such 3D models. It is found that about 50 per cent of direction-averaged Alfvén wave flux generated in the low atmosphere at frequencies comparable to or greater than the acoustic cut-off can reach the top as Alfvén flux for small magnetic field inclinations θ, and this increases to 80 per cent or more with increasing θ. On the other hand, direction-averaged slow waves can be 40 per cent effective in converting to Alfvén waves at small inclination, but this reduces sharply with increasing θ and wave frequency. Together with previously explored fast–slow and fast–Alfvén couplings, this provides valuable insights into which injected transverse waves can reach the upper atmosphere as Alfvén waves, with implications for solar and stellar coronal heating and solar/stellar wind acceleration.

Whistler instability driven by the sunward electron deficit in the solar wind

Context. Solar wind electrons play an important role in the energy balance of the solar wind acceleration by carrying energy into interplanetary space in the form of electron heat flux. The heat flux is stored in the complex electron velocity distribution functions (VDFs) shaped by expansion, Coulomb collisions, and field-particle interactions. Aims. We investigate how the suprathermal electron deficit in the anti-strahl direction, which was recently discovered in the near-Sun solar wind, drives a kinetic instability and creates whistler waves with wave vectors that are quasi-parallel to the direction of the background magnetic field. Methods. We combined high-cadence measurements of electron pitch-angle distribution functions and electromagnetic waves provided by Solar Orbiter during its first orbit. Our case study is based on a burst-mode data interval from the Electrostatic Analyser System (SWA-EAS) at a distance of 112 RS (0.52 au) from the Sun, during which several whistler wave packets were detected by Solar Orbiter’s Radio and Plasma Waves (RPW) instrument. Results. The sunward deficit creates kinetic conditions under which the quasi-parallel whistler wave becomes unstable. We directly test our predictions for the existence of these waves through solar wind observations. We find whistler waves that are quasi-parallel and almost circularly polarised, propagating away from the Sun, coinciding with a pronounced sunward deficit in the electron VDF. The cyclotron-resonance condition is fulfilled for electrons moving in the direction opposite to the direction of wave propagation, with energies corresponding to those associated with the sunward deficit. Conclusions. We conclude that the sunward deficit acts as a source of quasi-parallel whistler waves in the solar wind. The quasilinear diffusion of the resonant electrons tends to fill the deficit, leading to a reduction in the total electron heat flux.

The survival of multiphase dusty clouds in hot winds

ABSTRACT Much progress has been made recently in the acceleration of ∼104 K clouds to explain absorption line measurements of the circumgalactic medium and the warm, atomic phase of galactic winds. However, the origin of the cold, molecular phase in galactic winds has received relatively little theoretical attention. Studies of the survival of ∼104 K clouds suggest efficient radiative cooling may enable the survival of expelled material from galactic discs. Alternatively, gas colder than 104 K may form within the outflow, including molecules if dust survives the acceleration process. We explore the survival of dusty clouds in a hot wind with three-dimensional hydrodynamic simulations including radiative cooling and dust modelled as tracer particles. We find that cold ∼103 K gas can be destroyed, survive, or transformed entirely to ${\sim}10^4\,$ K gas. We establish analytic criteria distinguishing these three outcomes that compare characteristic cooling times to the system’s ‘cloud crushing’ time. In contrast to typically studied ∼104 K clouds, colder clouds are entrained faster than the drag time as a result of efficient mixing. We find that while dust can in principle survive embedded in the accelerated clouds, the survival fraction depends critically on the time dust spends in the hot phase and on the effective threshold temperature for destruction. We discuss our results in the context of polluting the circumgalactic medium with dust and metals, as well as understanding observations suggesting rapid acceleration of molecular galactic winds and ram-pressure-stripped tails of jellyfish galaxies.

Parker's Solar Wind Model for a Polytropic Gas.

Parker’s hydrodynamic isothermal solar wind model is extended to apply for a more realistic polytropic gas flow that can be caused by a variable extended heating of the corona. A compatible theoretical formulation is given and detailed numerical and systematic asymptotic theoretical considerations are presented. The polytropic conditions favor an enhanced conversion of thermal energy in the solar wind into kinetic energy of the outward flow and are hence shown to enhance the acceleration of the solar wind, thus indicating a quicker loss of the solar angular momentum.

Global Distribution of the Solar Wind Speed Reconstructed from Improved Tomographic Analysis of Interplanetary Scintillation Observations between 1985 and 2019

Abstract Computer-assisted tomography (CAT) for interplanetary scintillation (IPS) observations enables the determination of the global distribution of solar wind speed. We compared solar wind speeds derived from the CAT analysis of IPS observations between 1985 and 2019 with in situ observations conducted by the near-Earth and Ulysses spacecraft. From this comparison, we found that solar wind speeds from the IPS observations for 2009–2019 were systematically higher than the in situ observations, whereas those for the period until 2008 were in good agreement with the in situ observations. Further, we found that the discrepancy between IPS and the in situ observations is improved by changing the power index of the empirical relation between the solar wind speed and density fluctuations. The CAT analysis using an optimal value for the power index determined from the comparison between IPS and in situ observations revealed long-term variations in the solar wind speed distribution over three cycles, leading to a better understanding of the time-varying global heliosphere. We found that polar solar winds become highly anisotropic at the Cycle 24/25 minimum, which is a peculiar aspect of this minimum. The IPS observations showed general agreement with the Parker Solar Probe observations around the perihelion of Orbit 1; this supports the reliability of the CAT analysis. The results of this study suggest that the physical properties of solar wind microturbulence may vary with a long-term decline in the solar activity, which provides important implication on the solar wind acceleration.

A statistical evaluation of ballistic backmapping for the slow solar wind: The interplay of solar wind acceleration and corotation

Abstract Mapping solar wind plasma back to its source is often achieved using the ‘two-step ballistic backmapping’ method. Solar wind observations are mapped through the heliosphere to the edge of a PFSS model, by assuming a constant speed, radial, plasma flow. Tracing field lines through the model gives the source location at 1 R⊙ The heliospheric mapping component hinges upon the argument that two known sources of error, stemming from solar wind acceleration and non-radial flow, effectively cancel. This assumption has not been tested statistically. In this study, we evaluate the heliospheric portion of two-step backmapping, in addition to mapping using models with explicit radial acceleration, and azimuthal velocity, vφ, derived from angular momentum conservation. We estimate longitudinal mapping offsets, Δφ, between 326 Earth-observed crossings of the heliospheric current sheet (HCS), and corresponding crossings at 2.5 R⊙ from PFSS models. While the detailed solar wind models can be optimised to produce Δφ in good average agreement with HCS crossing data, the ballistic mapping performs almost as well, although all residuals have a sizeable standard deviation σ ∼ 16○. We conclude that the proposed error cancellation likely contributes to the good performance of ballistic mapping. However, interplanetary acceleration and the height of effective solar wind corotation are both smaller than previously assumed. Our results further suggest that early Parker Solar Probe observations of large vφ around 36 R⊙ do not represent the overall solar wind, due to the requirement for it to be balanced by increased acceleration.

The origin of Galactic cosmic rays as revealed by their composition

ABSTRACT Galactic cosmic rays (GCRs) are thought to be accelerated in strong shocks induced by massive star winds and supernova explosions sweeping across the interstellar medium. But the phase of the interstellar medium from which the CRs are extracted has remained elusive until now. Here, we study in detail the GCR source composition deduced from recent measurements by the AMS-02, Voyager 1, and SuperTIGER experiments to obtain information on the composition, ionization state, and dust content of the GCR source reservoirs. We show that the volatile elements of the CR material are mainly accelerated from a plasma of temperature ≳ 2 MK, which is typical of the hot medium found in Galactic superbubbles energized by the activity of massive star winds and supernova explosions. Another GCR component, which is responsible for the overabundance of 22Ne, most likely arises from acceleration of massive star winds in their termination shocks. From the CR-related gamma-ray luminosity of the Milky Way, we estimate that the ion acceleration efficiency in both supernova shocks and wind termination shocks is of the order of 10−5. The GCR source composition also shows evidence for a preferential acceleration of refractory elements contained in interstellar dust. We suggest that the GCR refractories are also produced in superbubbles, from shock acceleration and subsequent sputtering of dust grains continuously incorporated into the hot plasma through thermal evaporation of embedded molecular clouds. Our model explains well the measured abundances of all primary and mostly primary CRs from H to Zr, including the overabundance of 22Ne.