Estimating the temperature of solar wind particles and their anisotropies is particularly important for understanding the origin of their deviations from thermal equilibrium and the effects this has. ...In the absence of energetic events, the velocity distribution of electrons reveals a dual structure with a thermal (Maxwellian) core and a suprathermal (kappa) halo. This article presents a detailed observational analysis of these two components, providing estimations of their temperatures and temperature anisotropies, and decoding any potential interdependence that their properties may indicate. The dataset used in this study includes more than 120 000 of the distributions measured by three missions in the ecliptic within an extended range of heliocentric distances from 0.3 to over 4 AU. The core temperature is found to decrease with the radial distance, while the halo temperature slightly increases, clarifying an apparent contradiction in previous observational analyses and providing valuable clues about the temperature of the kappa-distributed populations. For low values of the power-index kappa, these two components manifest a clear tendency to deviate from isotropy in the same direction, which seems to confirm the existence of mechanisms with similar effects on both components,
e.g.
, the solar wind expansion, or the particle heating by the fluctuations. However, the existence of plasma states with anticorrelated anisotropies of the core and halo populations and the increase in their number for high values of the power-index kappa suggest a dynamic interplay of these components, mediated, most probably, by the anisotropy-driven instabilities.
Abstract
The direction and magnitude of the dipole anisotropy of ultra-high-energy cosmic rays with energies above 8 EeV observed by the Pierre Auger Observatory indicate their extragalactic origin. ...The observed dipole on Earth does not necessarily need to correspond to the anisotropy of the extragalactic cosmic-ray flux due to the effects of propagation in the Galactic magnetic field. We estimate the size of these effects via numerical simulations using the CRPropa 3 package. The Jansson-Farrar and Terral-Ferrière models of the Galactic magnetic field are used to propagate particles within the Galaxy. We identify allowed directions and amplitudes of the dipole outside the Galaxy that are compatible with the measured features of the dipole on Earth for various mass composition scenarios at the 68% and 95% confidence level.
SUMMARY
Plant species with large genomes tend to be excluded from climatically more extreme environments with a shorter growing season. Species that occupy such environments are assumed to be under ...natural selection for more rapid growth and smaller genome size (GS). However, evidence for this is available only for temperate organisms. Here, we study the evolution of GS in two subfamilies of the tropical family Zingiberaceae to find out whether species with larger genomes are confined to environments where the vegetative season is longer. We tested our hypothesis on 337 ginger species from regions with contrasting climates by correlating their GS with an array of plant traits and environmental variables. We revealed 16‐fold variation in GS which was tightly related to shoot seasonality. Negative correlations of GS with latitude, temperature and precipitation emerged in the subfamily Zingiberoidae, demonstrating that species with larger GS are excluded from areas with a shorter growing season. In the subfamily Alpinioideae, GS turned out to be correlated with the type of stem and light requirements and its members cope with seasonality mainly by adaptation to shady and moist habitats. The Ornstein–Uhlenbeck models suggested that evolution in regions with humid climates favoured larger GS than in drier regions. Our results indicate that climate seasonality exerts an upper constraint on GS not only in temperate regions but also in the tropics, unless species with large genomes find alternative ways to escape from that constraint.
Significance Statement
The question of how species can adapt to periods of drought and drought stress is of great relevance in the current period of climate change and it is also worth asking whether mechanisms of adaptation are similar in different parts of the world. Here, we focused on the poorly understood but complex biomes like monsoon forest, tropical dry forest and tropical rainforest, while using the economically important family Zingiberaceae as a model group.
We present a numerical scheme for the integration of the Vlasov–Maxwell system of equations for a non-relativistic plasma, in the hybrid approximation, where the Vlasov equation is solved for the ion ...distribution function and the electrons are treated as a fluid. In the Ohm equation for the electric field, effects of electron inertia have been retained, in order to include the small scale dynamics up to characteristic lengths of the order of the electron skin depth. The low frequency approximation is used by neglecting the time derivative of the electric field, i.e. the displacement current in the Ampere equation.
The numerical algorithm consists in coupling the splitting method proposed by Cheng and Knorr in 1976 C.Z. Cheng, G. Knorr, J. Comput. Phys. 22 (1976) 330–351. and the current advance method (CAM) introduced by Matthews in 1994 A.P. Matthews, J. Comput. Phys. 112 (1994) 102–116. In its present version, the code solves the Vlasov–Maxwell equations in a five-dimensional phase space (2-D in the physical space and 3-D in the velocity space) and it is implemented in a parallel version to exploit the computational power of the modern massively parallel supercomputers. The structure of the algorithm and the coupling between the splitting method and the CAM method (extended to the hybrid case) is discussed in detail. Furthermore, in order to test the hybrid-Vlasov code, the numerical results on propagation and damping of linear ion-acoustic modes and time evolution of linear elliptically polarized Alfvén waves (including the so-called whistler regime) are compared to the analytical solutions. Finally, the numerical results of the hybrid-Vlasov code on the parametric instability of Alfvén waves are compared with those obtained using a two-fluid approach.
Context.
Solar wind evolution differs from a simple radial expansion, while wave-particle interactions are assumed to be the major cause for the observed dynamics of the electron distribution ...function. In particular, whistler waves are thought to inhibit the electron heat flux and ensure the diffusion of the field-aligned energetic electrons (Strahl electrons) to replenish the halo population.
Aims.
The goal of our study is to detect and characterize the electromagnetic waves that have the capacity to modify the electron distribution functions, with a special focus on whistler waves.
Methods.
We carried out a detailed analysis of the electric and magnetic field fluctuations observed by the Solar Orbiter spacecraft during its first orbit around the Sun, between 0.5 and 1 AU. Using data from the Search Coil Magnetometer and electric antenna, both part of the Radio and Plasma Waves (RPW) instrumental suite, we detected the electromagnetic waves with frequencies above 3 Hz and determined the statistical distribution of their amplitudes, frequencies, polarization, and
k
-vector as a function of distance. Here, we also discuss the relevant instrumental issues regarding the phase between the electric and magnetic measurements as well as the effective length of the electric antenna.
Results.
An overwhelming majority of the observed waves are right-handed circularly polarized in the solar wind frame and identified as outwardly propagating quasi-parallel whistler waves. Their occurrence rate increases by a least a factor of 2 from 1 AU to 0.5 AU. These results are consistent with the regulation of the heat flux by the whistler heat flux instability. Near 0.5 AU, whistler waves are found to be more field-aligned and to have a smaller normalized frequency (
f
/
f
ce
), larger amplitude, and greater bandwidth than at 1 AU.
Context.
Electric field measurements of the Time Domain Sampler (TDS) receiver, part of the Radio and Plasma Waves (RPW) instrument on board Solar Orbiter, often exhibit very intense broadband wave ...emissions at frequencies below 20 kHz in the spacecraft frame. During the first year of the mission, the RPW/TDS instrument was operating from the first perihelion in mid-June 2020 and through the first flyby of Venus in late December 2020.
Aims.
In this paper, we present a year-long study of electrostatic fluctuations observed in the solar wind at an interval of heliocentric distances from 0.5 to 1 AU. The RPW/TDS observations provide a nearly continuous data set for a statistical study of intense waves below the local plasma frequency.
Methods.
The on-board and continuously collected and processed properties of waveform snapshots allow for the mapping plasma waves at frequencies between 200 Hz and 20 kHz. We used the triggered waveform snapshots and a Doppler-shifted solution of the dispersion relation for wave mode identification in order to carry out a detailed spectral and polarization analysis.
Results.
Electrostatic ion-acoustic waves are the most common wave emissions observed between the local electron and proton plasma frequency by the TDS receiver during the first year of the mission. The occurrence rate of ion-acoustic waves peaks around perihelion at distances of 0.5 AU and decreases with increasing distances, with only a few waves detected per day at 0.9 AU. Waves are more likely to be observed when the local proton moments and magnetic field are highly variable. A more detailed analysis of more than 10 000 triggered waveform snapshots shows the mean wave frequency at about 3 kHz and wave amplitude about 2.5 mV m
−1
. The wave amplitude varies as
R
−1.38
with the heliocentric distance. The relative phase distribution between two components of the E-field projected in the
Y
−
Z
Spacecraft Reference Frame (SRF) plane shows a mostly linear wave polarization. Electric field fluctuations are closely aligned with the directions of the ambient field lines. Only a small number (3%) of ion-acoustic waves are observed at larger magnetic discontinuities.
Context.
In order to allow for a comparison with the measurements from other antenna systems, the voltage power spectral density measured by the Radio and Plasma waves receiver (RPW) on board Solar ...Orbiter needs to be converted into physical quantities that depend on the intrinsic properties of the radiation itself (e.g., the brightness of the source).
Aims.
The main goal of this study is to perform a calibration of the RPW dipole antenna system that allows for the conversion of the voltage power spectral density measured at the receiver’s input into the incoming flux density.
Methods.
We used space observations from the Thermal Noise Receiver (TNR) and the High Frequency Receiver (HFR) to perform the calibration of the RPW dipole antenna system. Observations of type III bursts by the Wind spacecraft are used to obtain a reference radio flux density for cross-calibrating the RPW dipole antennas. The analysis of a large sample of HFR observations (over about ten months), carried out jointly with an analysis of TNR-HFR data and prior to the antennas’ deployment, allowed us to estimate the reference system noise of the TNR-HFR receivers.
Results.
We obtained the effective length,
l
eff
, of the RPW dipoles and the reference system noise of TNR-HFR in space, where the antennas and pre-amplifiers are embedded in the solar wind plasma. The obtained
l
eff
values are in agreement with the simulation and measurements performed on the ground. By investigating the radio flux intensities of 35 type III bursts simultaneously observed by Wind and Solar Orbiter, we found that while the scaling of the decay time as a function of the frequency is the same for the Waves and RPW instruments, their median values are higher for the former. This provides the first observational evidence that Type III radio waves still undergo density scattering, even when they propagate from the source, in a medium with a plasma frequency that is well below their own emission frequency.
Despite the fact that the information about past accidents is an integral part of accident prevention, the information about industrial accidents is not commonly available in food and agricultural ...sectors. Spray dryer plants for dairy products are not an exception. The aim of this paper is the creation of the representative database for industrial spray drying accidents in order to identify their major causes. The paper is divided into 8 chapters. The first two chapters deal with the general information about technology of spray drying of dairy products. The third chapter provides the outputs from the authors' database containing records of 25 accidents in milk drying facilities in Europe. These accidents took place between 1999 and 2019 in six European countries. Based on the accident database, the most common causes of accidents were identified. Processes that can cause a fire, an explosion, or damage to environment are described in the fourth, fifth and sixth chapter. The seventh chapter deals with process, technical and organizational measures; these were discussed using literature research and the results of the accident database. The eighth chapter is the conclusion with a focus on further improvement of process safety through newly developed protective tools.
•The database containing records of 25 accidents in milk drying operations was created.•Based on the accident database most common causes of accidents were identified.•Parameters that influence self-heating of milk powder layer were discussed.•The explosion characteristics of a milk powder were described.•Technical and organizational measures against accidents were discussed.
The Solar Orbiter flyby of Venus on 27 December 2020 allowed for an opportunity to measure the suprathermal to energetic ions in the Venusian system over a large range of radial distances to better ...understand the acceleration processes within the system and provide a characterization of galactic cosmic rays near the planet. Bursty suprathermal ion enhancements (up to ∼10 keV) were observed as far as ∼50
R
V
downtail. These enhancements are likely related to a combination of acceleration mechanisms in regions of strong turbulence, current sheet crossings, and boundary layer crossings, with a possible instance of ion heating due to ion cyclotron waves within the Venusian tail. Upstream of the planet, suprathermal ions are observed that might be related to pick-up acceleration of photoionized exospheric populations as far as 5
R
V
upstream in the solar wind as has been observed before by missions such as Pioneer Venus Orbiter and Venus Express. Near the closest approach of Solar Orbiter, the Galactic cosmic ray (GCR) count rate was observed to decrease by approximately 5 percent, which is consistent with the amount of sky obscured by the planet, suggesting a negligible abundance of GCR albedo particles at over 2
R
V
. Along with modulation of the GCR population very close to Venus, the Solar Orbiter observations show that the Venusian system, even far from the planet, can be an effective accelerator of ions up to ∼30 keV. This paper is part of a series of the first papers from the Solar Orbiter Venus flyby.
Context.
A variety of kinetic electrostatic and electromagnetic waves develop in the solar wind and the relationship between these waves and larger scale structures, such as current sheets and ...ongoing turbulence, remain a topic of investigation. Similarly, the instabilities producing ion-acoustic waves in the solar wind are still an open question.
Aims.
The goals of this paper are to investigate electrostatic Langmuir and ion-acoustic waves in the solar wind at 0.5 AU and determine whether current sheets and associated streaming instabilities can produce the observed waves. The relationship between these waves and currents observed in the solar wind is investigated statistically.
Methods.
Solar Orbiter’s Radio and Plasma Waves instrument suite provides high-resolution snapshots of the fluctuating electric field. The Low Frequency Receiver resolves the waveforms of ion-acoustic waves and the Time Domain Sampler resolves the waveforms of both ion-acoustic and Langmuir waves. Using these waveform data, we determine when these waves are observed in relation to current structures in the solar wind, estimated from the background magnetic field.
Results.
Langmuir and ion-acoustic waves are frequently observed in the solar wind. Ion-acoustic waves are observed about 1% of the time at 0.5 AU. The waves are more likely to be observed in regions of enhanced currents. However, the waves typically do not occur at current structures themselves. The observed currents in the solar wind are too small to drive instability by the relative drift between single ion and electron populations. When multi-component ion or electron distributions are present, the observed currents may be sufficient for instabilities to occur. Ion beams are the most plausible source of ion-acoustic waves in the solar wind. The spacecraft potential is confirmed to be a reliable probe of the background electron density when comparing the peak frequencies of Langmuir waves with the plasma frequency calculated from the spacecraft potential.
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