Victor Montagud-Camps

University of Murcia | UM · Departamento de Electromagnetismo y Electrónica

A study to determine the detection efficiency and location accuracy of the Worldwide Lightning Location Network (WWLLN) over Spain is presented by comparing data with those of the Meteorological Spanish Agency (AEMET), taken as a ground truth. The WWLLN operates a planetary distributed network of stations which detect lightning signals at a planeta...

Electromagnetic Ion Cyclotron (EMIC) waves mediate energy transfer from the solar wind to the magnetosphere, relativistic electron precipitation, or thermalization of the ring current population, to name a few. How these processes take place depends on the wave properties, such as the wavevector and polarization. However, inferring the wavevector f...

Aims. We investigated the properties of plasma turbulence at ion scales in the solar wind context. We concentrated on the behaviour of the Hall physics and the pressure strain interaction and their anisotropy owing to the ambient magnetic field. Methods. We studied the results of a three-dimensional hybrid simulation of decaying plasma turbulence u...

In plasma turbulence, energy and cross helicity are transferred across scales at a constant rate as a consequence of nonlinear interactions. In incompressible magnetohydrodynamics (MHD), the energy cascade rate of both quantities can be computed by means of the temporal evolution of second-order structure functions, known as Karman–Howarth–Monin (K...

We analyse two high-resolution 2D hybrid simulations of plasma turbulence with observation-driven initial conditions that are representative of the near-Sun and the near-Earth solar wind. The former employs values of some fundamental parameters that have been measured by the Parker Solar Probe at 0.17 au from the Sun, while, in the latter, they are...

We investigate properties of solar-wind-like plasma turbulence using direct numerical simulations. We analyze the transition from large, magnetohydrodynamic (MHD) scales to the ion characteristic ones using two-dimensional hybrid (fluid electrons and kinetic ions) simulations. To capture and quantify turbulence properties, we apply the Karman–Howar...

We investigate properties of solar wind-like plasma turbulence using direct numerical simulations. We analyze the transition from large, magnetohydrodynamic (MHD) scales to the ion characteristic ones using two-dimensional hybrid (fluid electrons, kinetic ions) simulations. To capture and quantify turbulence properties, we apply the Karman-Howarth-...

We present results of a multiscale study of Hall-magnetohydrodynamic (MHD) turbulence, carried out on a dataset of compressible nonlinear 2D Hall-MHD numerical simulations of decaying Alfvénic turbulence. For the first time, we identify two distinct regimes of fully developed turbulence. In the first one, the power spectrum of the turbulent magneti...

Observations of proton density fluctuations of the solar wind at 1 au have shown the presence of a decade-long transition region of the density spectrum above sub-ion scales, characterized by a flattening of the spectral slope. We use the proton density fluctuations data collected by the BMSW instrument on-board the Spektr-R satellite in order to d...

We derive two new forms of the Kármán–Howarth–Monin (KHM) equation for decaying compressible Hall magnetohydrodynamic (MHD) turbulence. We test them on results of a weakly compressible, 2D, moderate-Reynolds-number Hall MHD simulation and compare them with an isotropic spectral transfer (ST) equation. The KHM and ST equations are automatically sati...

We present a large statistical study of the fluctuation anisotropy in minimum variance (MV) frames of the magnetic field and solar wind velocity. We use 2, 10, 20, and 40 minute intervals of simultaneous magnetic field (the Wind spacecraft) and velocity (the Spektr-R spacecraft) observations. Our study confirms that magnetic turbulence is a composi...

We derive two new forms of the K\'arm\'an-Howarth-Monin equation for decaying compressible Hall magnetohydrodynamic (MHD) turbulence. We test them on results of a weakly-compressible, two-dimensional, moderate-Reynolds-number Hall MHD simulation and compare them with an isotropic spectral transfer (ST) equation. The KHM and ST equations are automat...

In a previous work (MGV18), we showed numerically that the turbulent cascade generated by quasi-2D structures (with wavevectors mostly perpendicular to the mean magnetic field) is able to generate a temperature profile close to the one observed in solar wind (≃1/ R ) in the range 0.2 ≤ R ≤ 1 au. Theory, observations, and numerical simulations point...

In a previous work (MGV18), we showed numerically that the turbulent cascade generated by quasi-2D structures (with wave vectors mostly-perpendicular to the mean magnetic field) is able to generate a temperature profile close to the one observed in solar wind ($\simeq 1/R$) in the range 0.2 $\le R \le$ 1 au. Theory, observations and numerical simul...

We consider first the procedures used to measure properties of the 3D spectra and then of 1D spectra.

We use here EBM simulations to study the generation of the spectral anisotropy in the distance range [0.2,1] AU, which as seen previously (Sect. 4.3.1) is different in the fast and slow wind at 1 AU. Here, we present the initial parameters that will be used to study spectral anisotropy in the expanding solar wind.

The EBM equations assume the MHD closure, that is, that proton temperature is isotropic. This assumption is not always valid. As it can be seen from 2D cuts of the 3D velocity distribution functions of protons, while the core of the velocity distribution function for slow winds is isotropic, the distribution for fast winds is perpendicular to the m...

Thanks to the deployment of satellite probes in the heliosphere since the 90s (Ulysses, Helios, ACE, Wind...), solar wind is one of the few examples of astrophysical plasmas in which in-situ measurements can be made. Since the launch of these probes, it has been possible to recover data from solar wind plasma using several types of instruments. Fro...

The 1D hydrodynamic description of turbulence presented in the previous chapter has proven to be useful as a first approach to understand the development of turbulence in the expanding box simulations. However the 3D MHD model introduced in Sect. 2.2, the EBM equations, is clearly more realistic. In this chapter, we detail the initial properties of...

We adopt a one-fluid description (Magnetohydrodynamics or MHD) of the solar wind plasma. A fluid description describes the plasma in terms of the evolution of its macroscopic variables: density, velocity, pressure, heat flux, ...and the evolution of the magnetic and electric fields, \(\mathbf B \) and \(\mathbf E \), given by Maxwell’s equations. I...

A qualitative picture of turbulence in every day life is given by random patterns (usually eddies) forming in the wake of a solid obstacle facing a flow, or air turbulence forming for instance above a tea cup. Turbulence can be found in a variety of contexts, such as geophysical flows, gravitational waves, interstellar medium, or the Solar Wind. He...

In the previous chapter we saw that under reasonable initial conditions at 0.2 AU it is possible to generate a proton temperature profile close to \(R^{-1}\) in the [0.2, 1] AU interval, solely from the contribution of turbulent heating, starting with a gyrotropic initial spectrum with \(M=1\), \(\epsilon =0.2\). It is thus interesting to generaliz...

In the following, we show how the initial energy spectrum, cross helicity and expansion affect spectral anisotropy. We have checked that after an initial phase, the spectra don’t depend on the choice of these initial parameters. In the zero cross-helicity case, spectral anisotropy bas been analyzed by VG16. Our results will be compared with those o...

We consider here the evolution of a 1D spectrum in the expanding (radial) wind, that is, with wavevectors all aligned in a given direction. We consider two cases: wavevectors in the radial direction, and wavevectors in a transverse direction (perpendicular to the radial). Based on these assumptions, we present a model of turbulent heating that is t...

The first hydrodynamic theory of the origin of thesolar wind was published by Parker [12]. He remarked that a strong difference in thermal pressure between the high atmosphere (corona) and interstellar plasma could lead to a global supersonic wind at a few solar radii. Parker’s theory required a source of internal (thermal) energy which had to be t...

Abstract Kinetic-scale fluctuations in magnetized collisionless plasmas, such as a solar wind, attract attention owing to their vital role in the dynamics of the dissipation of free energy to random particle motion. As the free energy cascades in the inertial range of turbulence, fluctuations at ion characteristic scales become more compressible. M...

Recent studies of turbulence-driven solar winds indicate that fast winds are obtained only at the price of unrealistic bottom boundary conditions: too large wave amplitudes and small frequencies. In this work, the incompressible turbulent dissipation is modeled with a large-scale von Karman–Howarth–Kolmogorov-like phenomenological expression (\(Q_{...

This book presents two important new findings. First, it demonstrates from first principles that turbulent heating offers an explanation for the non-adiabatic decay of proton temperature in solar wind. Until now, this was only proved with reduced or phenomenological models. Second, the book demonstrates that the two types of anisotropy of turbulent...

The aim of this thesis is the study of the development of turbulence in the solar wind between 0.2 and 1 astronomical unit (AU) from the Sun (i.e. Earth’s orbit). The study is done by solving the magnetohydrodynamics equations (MHD) after subtracting the mean radial flow. The two aspects of turbulence that interest us are the 3D structure of the en...

The heating of the solar wind is key to understanding its dynamics and acceleration process. The observed radial decrease of the proton temperature in the solar wind is slow compared to the adiabatic prediction, and it is thought to be caused by turbulent dissipation. To generate the observed 1/R decrease, the dissipation rate has to reach a specif...