Heating Of Solar Wind Research Articles

The Effects of Turbulence on Heliosheath Ions and Implications for Energetic Neutral Atoms

The distribution of ions in the heliosheath—the region between the heliospheric termination shock and the heliopause—is important for understanding remote observations of energetic neutral atoms (ENAs). The ion distributions were estimated previously based on hybrid simulations of the heating and evolution of solar wind and interstellar pickup ions across the solar wind termination shock, but these estimates only provide the distributions near the shock. In this work, we use self-consistent hybrid kinetic simulations to investigate the effects of turbulence on ion distributions in the heliosheath. The simulations are compared against Voyager observations, constraining the feasible amplitude and compressibility of turbulence. We find that the heating due to turbulent dissipation can lead to a significant increase in the temperature of thermal solar wind ions. Both turbulent velocity fluctuations and the heating of solar wind ions increase the charge-exchange source for ENAs at low energies (around 100 eV), where current ENA models underpredict observations by more than an order of magnitude. However, the effects of turbulence are likely not strong enough to fully explain these discrepancies.

The Independence of Magnetic Turbulent Power Spectra to the Presence of Switchbacks in the Inner Heliosphere

An outstanding gap in our knowledge of the solar wind is the relationship between switchbacks and solar wind turbulence. Switchbacks are large fluctuations, even reversals, of the background magnetic field embedded in the solar wind flow. It has been proposed that switchbacks may form as a product of turbulence and decay via coupling with the turbulent cascade. In this work, we examine how properties of solar wind magnetic field turbulence vary in the presence or absence of switchbacks. Specifically, we use in situ particle and fields measurements from Parker Solar Probe to measure magnetic field turbulent wave power, separately in the inertial and kinetic ranges, as a function of switchback magnetic deflection angle. We demonstrate that the angle between the background magnetic field and the solar wind velocity in the spacecraft frame (θ vB ) strongly determines whether Parker Solar Probe samples wave power parallel or perpendicular to the background magnetic field. Further, we show that θ vB is strongly modulated by the switchback magnetic deflection angle. In this analysis, we demonstrate that switchback deflection angle does not correspond to any significant increase in wave power in either the inertial range or at kinetic scales. This result implies that switchbacks do not strongly couple to the turbulent cascade in the inertial or kinetic ranges via turbulent wave–particle interactions. Therefore, we do not expect switchbacks to contribute significantly to solar wind heating through this type of energy conversion pathway although contributions via other mechanisms, such as magnetic reconnection, may still be significant.

In situ observations of large-amplitude Alfvén waves heating and accelerating the solar wind.

After leaving the Sun's corona, the solar wind continues to accelerate and cools, but more slowly than expected for a freely expanding adiabatic gas. Alfvén waves are perturbations of the interplanetary magnetic field that transport energy. We use in situ measurements from the Parker Solar Probe and Solar Orbiter spacecraft to investigate a stream of solar wind as it traverses the inner heliosphere. The observations show heating and acceleration of the plasma between the outer edge of the corona and near the orbit of Venus, along with the presence of large-amplitude Alfvén waves. We calculate that the damping and mechanical work performed by the Alfvén waves are sufficient to power the heating and acceleration of the fast solar wind in the inner heliosphere.

Oceanic response to tropical cyclone in the northern South China Sea observed by underwater gliders during 2018 and 2020

In this study, we mainly used in-situ observations from underwater gliders to analyze the ocean response in the northern South China Sea affected by Son-tinh (2018), Mandal et al. (2018) Mangkhut (2018)and Noul (2020). The results showed that these TCs caused 0.6 °C, 1.1 °C and 1.7 °C maximum sea surface temperature cooling respectively, which were weaker than general conditions because of long distance, weak intensity and fast movement speed. Net solar radiation, precipitation, 10-m wind and sea surface heat flux also made contribution in changes of SST. The mixed layer depth (MLD) became shallower after Son-Tinh and Noul passed through, while during Mangkhut it did not change significantly. After TCs passed through, the stratification around MLD became more obvious, with a banded distribution and stronger high-value areas of buoyancy frequency. Within 1 week after the shortest distance, the temperature and salinity responses in the upper ocean were stronger than those at the sea surface, and the gradients of temperature and salinity and their anomalies were more evident in the subsurface layer. The results of this study show that underwater glider observations are important for understanding oceanic responses to tropical cyclones and are useful for studying tropical cyclone activities.

Whistler Waves in the Young Solar Wind: Statistics of Amplitude and Propagation Direction from Parker Solar Probe Encounters 1–11

In the interplanetary space solar wind plasma, whistler waves are observed in a wide range of heliocentric distances (from ∼20 solar radii (RS) to Jupiter’s orbit). They are known to interact with solar wind suprathermal electrons (strahl and halo) and to regulate the solar wind heat flux through scattering the strahl electrons. We present the results of applying the technique to determine the whistler wave propagation directions to the spectral data continuously collected by the FIELDS instruments on board Parker Solar Probe (PSP). The technique was validated based on the results obtained from burst mode magnetic and electric field waveform data collected during Encounter 1. We estimated the effective length of the PSP electric field antennas for a variety of solar wind conditions in the whistler wave frequency range and utilized these estimates for determining the whistler wave properties during PSP Encounters 1–11. Our findings show that (1) the enhancement of the whistler wave occurrence rate and wave amplitudes observed between 25 and 35 RS is predominantly due to the sunward-propagating whistler wave population associated with the switchback-related magnetic dips; (2) the antisunward or counterpropagating cases are observed at 30–40 RS; (3) between 40 and 50 RS, sunward and antisunward whistlers are observed with comparable occurrence rates; and (4) almost no sunward or counterpropagating whistlers were observed at heliocentric distances above 50 RS.

On the Heating of the Slow Solar Wind by Imbalanced Alfvén-wave Turbulence from 0.06 to 1 au: Parker Solar Probe and Solar Orbiter Observations

In this work we analyze plasma and magnetic field data provided by the Parker Solar Probe and Solar Orbiter missions to investigate the radial evolution of the heating of Alfvénic slow wind by imbalanced Alfvén-wave (AW) turbulent fluctuations from 0.06 to 1 au. in our analysis we focus on slow solar-wind intervals with highly imbalanced and incompressible turbulence (i.e., magnetic compressibility C B = δ B/B ≤ 0.25, plasma compressibility C n = δ n/n ≤ 0.25, and normalized cross helicity σ c ≥ 0.65). First, we estimate the AW turbulent dissipation rate from the wave energy equation and find that the radial profile trend is similar to the proton heating rate. Second, we find that the scaling of the empirical AW turbulent dissipation rate Q W obtained from the wave energy equation matches the scaling from the phenomenological AW turbulent dissipation rate Q CH09 (with Q CH09 ≃ 1.55Q W ) derived by Chandran & Hollweg based on the model of reflection-driven turbulence. Our results suggest that, as in the fast solar wind, AW turbulence plays a major role in the ion heating that occurs in incompressible slow-wind streams.

Nonlocal contributions to the turbulent cascade in magnetohydrodynamic plasmas.

We present evidence for nonlocal contributions to the turbulent energy cascade in magnetohydrodynamic (MHD) plasmas. Therefore, we revisit a well-known result derived directly from the MHD equations, i.e., the Politano and Pouquet law for the transfer of kinetic and magnetic energy in scale. We propose adding a term that accounts for nonlocal transfer and represents the influence of fluctuations from large scales due to the Alfvén effect. Supported by direct numerical simulations of homogeneous and isotropic MHD turbulence, we verify that in some plasma configurations, neglecting the additional nonlocal term might consistently overestimate energy dissipation rates and, thus, the contributions of turbulent energy dissipation potentially affecting solar wind heating, i.e., a central puzzle in space plasma physics that motivates the present work.

The Opposite Behaviors of Proton and Electron Temperatures in Relation to Solar Wind Magnetic Energy: Parker Solar Probe Observations

Solar wind heating is an outstanding issue that has been discussed for decades. Research on the connection between solar wind particle temperatures and turbulence may provide insight into this issue. Based on Parker Solar Probe observations, this paper investigates the properties of solar wind proton and electron temperatures in relation to turbulent magnetic energy, via the calculation of correlation coefficients (CCs) between particle temperatures and magnetic energy. The calculations are regulated by the spatial scale, plasma beta (β), and the angle between the solar wind velocity and background magnetic field, where the plasma beta is the ratio of plasma thermal to magnetic pressure. Results show that the correlation between proton temperature and magnetic energy is positive and can be strong with a CC exceeding 0.8. The strong correlation preferentially occurs at ion scales, with the wind velocity and background magnetic field quasi-perpendicular and over a wide beta range (β < 3.0). On the other hand, the correlation between electron temperature and magnetic energy is commonly negative, often with an intermediate or negligible CC, accordingly. The CC with an amplitude up to 0.8 can arise at larger scales with the wind velocity and background magnetic field quasi-(anti)parallel and in the low-beta case (β < 0.6). The implication of these findings on the physics of turbulent heating in the solar wind is discussed.

Identification of the weak-to-strong transition in Alfvénic turbulence from space plasma

Plasma turbulence is a ubiquitous dynamical process that transfers energy across many spatial and temporal scales in astrophysical and space plasma systems. Although the theory of anisotropic magnetohydrodynamic (MHD) turbulence has successfully described natural phenomena, its core prediction of an Alfvénic transition from weak to strong MHD turbulence when energy cascades from large to small scales has not been observationally confirmed. Here we report evidence for the Alfvénic weak-to-strong transition in small-amplitude, turbulent MHD fluctuations in Earth’s magnetosheath using data from four Cluster spacecraft. Our observations demonstrate the universal existence of strong turbulence accompanied by weak turbulent fluctuations on large scales. Moreover, we find that the nonlinear interactions of MHD turbulence are crucial to the energy cascade, as they broaden the cascade directions and fluctuating frequencies. The observed connection between weak and strong MHD turbulence systems may be present in many astrophysical environments, such as star formation, energetic particle transport, turbulent dynamos, and solar corona or solar wind heating.

Counter‐Helical Magnetic Flux Ropes From Magnetic Reconnections in Space Plasmas

AbstractMagnetic flux ropes are ubiquitous in various space environments, including the solar corona, interplanetary solar wind, and planetary magnetospheres. When these flux ropes intertwine, magnetic reconnection may occur at the interface, forming disentangled new ropes. Some of these newly formed ropes contain reversed helicity along their axes, diverging from the traditional flux rope model. We introduce new observations and interpretations of these newly formed flux ropes from existing Hall Magnetohydrodynamics model results. We first examine the time‐varying local magnetic field direction at the impact interface to assess the likelihood of reconnection. Then we investigate the electric current system to describe the evolution of these structures, which potentially accelerate particles and heat the plasma. This study offers novel insights into the dynamics of space plasmas and suggests a potential solar wind heating source, calling for further synthetic observations.

Analytic Model and Magnetohydrodynamic Simulations of Three-dimensional Magnetic Switchbacks

Parker Solar Probe observations reveal that the near-Sun space is almost filled with magnetic switchbacks (“switchbacks” hereinafter), which may be a major contributor to the heating and acceleration of solar wind. Here, for the first time, we develop an analytic model of an axisymmetric switchback with uniform magnetic field strength. In this model, three parameters control the geometry of the switchback: height (length along the background magnetic field), width (thickness along radial direction perpendicular to the background field), and the radial distance from the center of switchback to the central axis, which is a proxy of the size of the switchback along the third dimension. We carry out 3D magnetohydrodynamic simulations to investigate the dynamic evolution of the switchback. Comparing simulations conducted with compressible and incompressible codes, we verify that compressibility, i.e., parametric decay instability, is necessary for destabilizing the switchback. Our simulations also reveal that the geometry of the switchback significantly affects how fast the switchback destabilizes. The most stable switchbacks are 2D-like (planar) structures with large aspect ratios (length to width), consistent with the observations. We show that when plasma beta (β) is smaller than one, the switchback is more stable as β increases. However, when β is greater than 1, the switchback becomes very unstable as the pattern of the growing compressive fluctuations changes. Our results may explain some of the observational features of switchbacks, including the large aspect ratios and nearly constant occurrence rates in the inner heliosphere.

Monofractality in the Solar Wind at Electron Scales: Insights from Kinetic Alfvén Waves Turbulence.

The breakdown of scale invariance in turbulent flows, known as multifractal scaling, is considered a cornerstone of turbulence. In solar wind turbulence, a monofractal behavior can be observed at electron scales, in contrast to larger scales where multifractality always prevails. Why scale invariance appears at electron scales is a challenging theoretical puzzle with important implications for understanding solar wind heating and acceleration. We investigate this long-standing problem using direct numerical simulations of three-dimensional electron reduced magnetohydrodynamics. Both weak and strong kinetic Alfvén waves turbulence regimes are studied in the balanced case. After recovering the expected theoretical predictions for the magnetic spectra, a higher-order multiscale statistical analysis is performed. This study reveals a striking difference between the two regimes, with the emergence of monofractality only in weak turbulence, whereas strong turbulence is multifractal. This result, combined with recent studies, shows the relevance of collisionless weak KAW turbulence to describe the solar wind at electron scales.

The temporal and latitudinal dependences of turbulence driven by pickup ions in the outer heliosphere

The distribution of turbulence in the heliosphere remains a mystery, due to the complexity in not only modeling the turbulence transport equations but also identifying the drivers of turbulence that vary with time and spatial location. Beyond the ionization cavity (a few astronomical units (AU) from the Sun), the turbulence is driven predominantly by freshly created pickup ions (PUIs), in contrast to the driving by stream shear and compression. Understanding the source characteristics is necessary to refine turbulence transport models and interpret measurements of turbulence and solar wind temperature in the outer heliosphere. Using a recent latitude-dependent solar wind speed model and the ionization rate of neutral interstellar hydrogen (H), we investigate the temporal and spatial variation in the strength of low-frequency turbulence driven by PUIs from 1998 to 2020. We find that the driving rate is stronger during periods of high solar activity and at lower latitudes in the outer heliosphere. The driving rates for parallel and anti-parallel propagating (relative to the background magnetic field) slab turbulence have different spatial and latitude dependences. The calculated generation rate of turbulence by PUIs is an essential ingredient to investigate the latitude dependence of turbulence in the outer heliosphere, which is important to understand the heating of the distant solar wind and the modulation of cosmic rays.

Electron–Ion Heating Partition in Imbalanced Solar-wind Turbulence

A likely candidate mechanism to heat the solar corona and solar wind is low-frequency “Alfvénic” turbulence sourced by magnetic fluctuations near the solar surface. Depending on its properties, such turbulence can heat different species via different mechanisms, and the comparison of theoretical predictions to observed temperatures, wind speeds, anisotropies, and their variation with heliocentric radius provides a sensitive test of this physics. Here we explore the importance of normalized cross helicity, or imbalance, for controlling solar-wind heating, since it is a key parameter of magnetized turbulence and varies systematically with wind speed and radius. Based on a hybrid-kinetic simulation in which the forcing’s imbalance decreases with time—a crude model for a plasma parcel entrained in the outflowing wind—we demonstrate how significant changes to the turbulence and heating result from the “helicity barrier” effect. Its dissolution at low imbalance causes its characteristic features—strong perpendicular ion heating with a steep “transition-range” drop in electromagnetic fluctuation spectra—to disappear, driving a larger fraction of the energy into electrons and parallel ion heat, and halting the emission of ion-scale waves. These predictions seem to agree with a diverse array of solar-wind observations, offering to explain a variety of complex correlations and features within a single theoretical framework.

Estimates of Proton and Electron Heating Rates Extended to the Near-Sun Environment

A central problem of space plasma physics is how protons and electrons are heated in a turbulent, magnetized plasma. The differential heating of charged species due to dissipation of turbulent fluctuations plays a key role in solar wind evolution. Measurements from previous heliophysics missions have provided estimates of proton and electron heating rates beyond 0.27 au. Using Parker Solar Probe (PSP) data accumulated during the first 10 encounters, we extend the evaluation of the individual rates of heat deposition for protons and electrons to a distance of 0.063 au (13.5 R ⊙) in the newly formed solar wind. The PSP data in the near-Sun environment show different behavior of the electron heat conduction flux from what was predicted from previous fits to Helios and Ulysses data. Consequently, the empirically derived proton and electron heating rates exhibit significantly different behavior than previous reports, with the proton heating becoming increasingly dominant over electron heating at decreasing heliocentric distances. We find that the protons receive about 80% of the total plasma heating at ≈13 R ⊙, slightly higher than the near-Earth values. This empirically derived heating partition between protons and electrons will help to constrain theoretical models of solar wind heating.

Implementasi Proses Manufaktur Pembangkit Listrik Bertenaga Angin Dan Surya Di Pesisir Pantai Matras

Indonesia is a country rich in natural resources and natural resources. These natural resources can be in the form of wind and solar heat, wind and solar heat can be utilized as an alternative to power generation with the type of power generator in the form of wind turbines and solar panels. In certain areas there are still many that require a supply of electric power, for example in the Turun Aban Beach area. At that location there is no electricity supply at all. Meanwhile, the fishermen at the Turun Aban Beach location often carry out the process of transporting their catch at night. Therefore, to meet the needs of these fishermen, they can use alternative power generators in the form of wind turbines and solar panels. Coastal areas have great potential for wind speed and solar heat. This research examines the process of implementing wind and solar power generators that will be used as alternative lighting for fishermen on the Turun Aban Beach, Matras Bangka Village. The process of making the tool will be carried out at the PolmanBabel Mechanical Workshop. Making this tool will go through several stages such as cutting the frame material, welding, turning and also assembling the electrical circuit on the tool.

Electron–Ion Temperature Ratio in Astrophysical Shocks

Collisionless shock waves in supernova remnants and the solar wind heat electrons less effectively than they heat ions, as is predicted by kinetic simulations. However, the values of T e /T p inferred from the Hα profiles of supernova remnant shocks behave differently as a function of Mach number or Alfvén Mach number than what is measured in the solar wind or predicted by simulations. Here we determine T e /T p for supernova remnant shocks using Hα profiles, shock speeds from proper motions, and electron temperatures from X-ray spectra. We also improve the estimates of sound speed and Alfvén speed used to determine Mach numbers. We find that the Hα determinations are robust and that the discrepancies among supernova remnant shocks, solar wind shocks, and computer-simulated shocks remain. We discuss some possible contributing factors, including shock precursors, turbulence, and varying preshock conditions.

Whistler waves generated inside magnetic dips in the young solar wind: Observations of the search-coil magnetometer on board Parker Solar Probe

Context. Whistler waves are electromagnetic waves produced by electron-driven instabilities, which in turn can reshape the electron distributions via wave–particle interactions. In the solar wind they are one of the main candidates for explaining the scattering of the strahl electron population into the halo at increasing radial distances from the Sun and for subsequently regulating the solar wind heat flux. However, it is unclear what type of instability dominates to drive whistler waves in the solar wind. Aims. Our goal is to study whistler wave parameters in the young solar wind sampled by Parker Solar Probe (PSP). The wave normal angle (WNA) in particular is a key parameter to discriminate between the generation mechanisms of these waves. Methods. We analyzed the cross-spectral matrices of magnetic field fluctuations measured by the search-coil magnetometer (SCM) and processed by the Digital Fields Board (DFB) from the FIELDS suite during PSP’s first perihelion. Results. Among the 2701 wave packets detected in the cross-spectra, namely individual bins in time and frequency, most were quasi-parallel to the background magnetic field; however, a significant part (3%) of the observed waves had oblique (&gt; 45°) WNA. The validation analysis conducted with the time series waveforms reveal that this percentage is a lower limit. Moreover, we find that about 64% of the whistler waves detected in the spectra are associated with at least one magnetic dip. Conclusions. We conclude that magnetic dips provide favorable conditions for the generation of whistler waves. We hypothesize that the whistlers detected in magnetic dips are locally generated by the thermal anisotropy as quasi-parallel and can gain obliqueness during their propagation. We finally discuss the implications of our results for the scattering of the strahl in the solar wind.

Parametric analysis of heat flux inhibition in the solar wind: a macroscopic quasilinear approach

Abstract Magnitudes of electron temperature anisotropy and solar wind heat flux are defined with different physical mechanisms e.g. microinstabilities, interparticle collisions, and adiabatic expansion. In the dilute space plasma limit, the present study assumes the interplay between anisotropic core-halo electron components, their relative drift, and relative density of the halo electrons to determine the dynamics of backward and forward-propagating whistler heat flux instabilities along the ambient magnetic field. To investigate the feedback effects of these micro-instabilities in reshaping solar wind distributions and the total heat flux regulation, we formulate quasilinear kinetic equations on the basis of taking the macroscopic velocity moments. For the same input parameters of linear analysis, numerical solutions of the quasilinear equations indicate the time-scale variations, electrons and protons population, wave intensities, and constraints on the heat flux. In future perspective of the global-kinetic solar wind model, the present formalism may be an important step with the inclusion of radial and nonthermal effects.

Parker Solar Probe Observations of High Plasma β Solar Wind from the Streamer Belt

In general, slow solar wind from the streamer belt forms a high plasma β equatorial plasma sheet around the heliospheric current sheet (HCS) crossing, namely, the heliospheric plasma sheet (HPS). Current Parker Solar Probe (PSP) observations show that the HCS crossings near the Sun could be full or partial current sheet (PCS) crossings, and they share some common features but also have different properties. In this work, using the PSP observations from encounters 4–10, we identify streamer belt solar wind from enhancements in plasma β, and we further use electron pitch angle distributions to separate it into HPS solar wind around the full HCS crossings and PCS solar wind in the vicinity of PCS crossings. Based on our analysis, we find that the PCS solar wind has different characteristics as compared with HPS solar wind: (a) the PCS solar wind could be non-pressure-balanced structures rather than magnetic holes, and the total pressure enhancement mainly results from the less reduced magnetic pressure; (b) some of the PCS solar wind is mirror-unstable; and (c) the PCS solar wind is dominated by very low helium abundance but varied alpha–proton differential speed. We suggest that the PCS solar wind could originate from coronal loops deep inside the streamer belt, and it is pristine solar wind that still actively interacts with ambient solar wind; thus, it is valuable for further investigations of the heating and acceleration of slow solar wind.