Spectrum of kinetic plasma turbulence at 0.3-0.9 AU from the Sun

2021 ◽  
Author(s):  
Olga Alexandrova ◽  
Vamsee Krishna Jagarlamudi ◽  
Petr Hellinger ◽  
Milan Maksimovic ◽  
Yuri Shprits ◽  
...  
Keyword(s):  
Solar Wind ◽  
Power Spectra ◽  
Plasma Turbulence ◽  
Larmor Radius ◽  
The Sun ◽  
Magnetic Fluctuations ◽  
In Situ Observations ◽  
Ion Characteristic ◽  
Characteristic Scales

<p>We investigate the spectral properties of the turbulence in the solar wind which is a weakly collisional astrophysical plasma, accessible by in-situ observations. Using the Helios search coil magnetometer measurements in the fast solar wind, in the inner heliosphere, we focus on properties of the turbulent magnetic fluctuations at scales smaller than the ion characteristic scales, the so-called kinetic plasma turbulence. At such small scales, we show that the magnetic power spectra between 0.3 and 0.9 AU from the Sun have a generic shape ~f<sup>-8/3</sup>exp(-f/f<sub>d</sub>) where the dissipation frequency f<sub>d</sub> is correlated with the Doppler shifted frequency f<sub>ρe</sub> of the electron Larmor radius. This behavior is statistically significant: all the observed kinetic spectra are well described by this model, with f<sub>d</sub>=f<sub>ρe</sub>/1.8. These results provide important constraints on the dissipation mechanism in nearly collisionless space plasmas.</p>

Solar Wind Turbulence at Kinetic Scales in the inner Heliosphere

2020 ◽  
Author(s):  
Olga Alexandrova ◽  
Vamsee Jagarlamudi ◽  
Milan Maksimovic ◽  
Petr Hellinger ◽  
Yuri Shprits ◽  
...  
Keyword(s):  
Solar Wind ◽  
Time Domain ◽  
Coherent Structures ◽  
Larmor Radius ◽  
The Sun ◽  
Magnetic Fluctuations ◽  
Magnetic Vortices ◽  
Dissipation Scale ◽  
The Time Domain ◽  
Inner Heliosphere

<p>We study magnetic fluctuations at sub-ion scales and down to sub-electron scales using Helios/SCM measurements in the inner Heliosphere and Cluster/STAFF data at the Earth's orbit. Using these data we test the generality of the kinetic spectrum and we show that it follows the ~k<sup>-8/3</sup>exp(-kl<sub>d</sub>) law at different radial distances from the Sun (k being a wavenumber). We show as well that the dissipation scale l<sub>d</sub> correlates well with the electron Larmor radius ρ<sub>e</sub> at 0.3 AU and at 1 AU. Then, in the time domain, at 1 AU, using the wavelet transform, we study the nature of magnetic fluctuations, which form the kinetic spectrum. It appears, that the spectrum is dominated by non-linear coherent structures in the form of magnetic vortices with the smallest resolved scale of the order of ρ<sub>e</sub>. Finally, we comparer our results with measurements of the Parker Solar Probe/FIELDS and, hopefully, of the Solar Orbiter/RPW in the inner Heliosphere.</p>

Understanding Solar Wind Formation by Identifying the Origins of In Situ Observations 

2021 ◽  
Author(s):  
Samantha Wallace ◽  
Nicholeen M. Viall ◽  
Charles N. Arge
Keyword(s):  
Solar Wind ◽  
Solar Wind Speed ◽  
Source Region ◽  
Heliospheric Current Sheet ◽  
Slow Solar Wind ◽  
The Sun ◽  
Flux Transport ◽  
Model Driven ◽  
In Situ Observations

<p>Solar wind formation can be separated into three physical steps – source, release, and acceleration – that each leave distinct observational signatures on plasma parcels.  The Wang-Sheeley-Arge (WSA) model driven by Air Force Data Assimilative Photospheric Flux Transport (ADAPT) time-dependent photospheric field maps now has the ability to connect in situ observations more rigorously to their precise source at the Sun, allowing us to investigate the physical processes involved in solar wind formation.   In this talk, I will highlight my PhD dissertation research in which we use the ADAPT-WSA model to either characterize the solar wind emerging from specific sources, or investigate the formation process of various solar wind populations.  In the first study, we test the well-known inverse relationship between expansion factor (f<sub>s</sub>) and observed solar wind speed (v<sub>obs</sub>) for solar wind that emerges from a large sampling of pseudostreamers, to investigate if field line expansion plays a physical role in accelerating the solar wind from this source region.  We find that there is no correlation between f<sub>s</sub> and v<sub>obs</sub> at pseudostreamer cusps. In the second study, we determine the source locations of the first identified quasiperiodic density structures (PDSs) inside 0.6 au. Our modeling provides confirmation of these events forming via magnetic reconnection both near to and far from the heliospheric current sheet (HCS) – a direct test of the Separatrix-web (S-web) theory of slow solar wind formation.  In the final study, we use our methodology to identify the source regions of the first observations from the Parker Solar Probe (PSP) mission.  Our modeling enabled us to characterize the closest to the Sun observed coronal mass ejection (CME) to date as a streamer blowout.  We close with future ways that ADAPT-WSA can be used to test outstanding questions of solar wind formation.</p>

scholarly journals The Global Interaction of Comets with the Solar Wind

1991 ◽  
Vol 116 (2) ◽  
pp. 1125-1144 ◽  
Author(s):  
K. R. Flammer
Keyword(s):  
Solar Wind ◽  
Heliocentric Distance ◽  
Theoretical Models ◽  
Bow Shock ◽  
Flow Transition ◽  
The Sun ◽  
In Situ Observations ◽  
Comet Halley

AbstractThe global interaction of the solar wind with a comet as it orbits the Sun is reviewed. After a brief survey of the flow transition regions observed at comet Halley is presented, theoretical models are given for the cometocentric distance of the bow shock, the cometopause, and the ionopause. In addition, predictions are made as to what heliocentric distance these boundaries should form at. The results of these models are compared with the in situ observations at comet Halley.

scholarly journals Transforming in-situ observations of CME-driven shock accelerated protons into the shock's reference frame.

2005 ◽  
Vol 23 (5) ◽  
pp. 1931-1941 ◽  
Author(s):  
I. M. Robinson ◽  
G. M. Simnett
Keyword(s):  
Solar Physics ◽  
Solar Energetic Particle ◽  
Transport Processes ◽  
Solar Energetic Particle Event ◽  
The Sun ◽  
Proton Acceleration ◽  
Angle Scattering ◽  
Peak Energy ◽  
In Situ Observations

Abstract. We examine the solar energetic particle event following solar activity from 14, 15 April 2001 which includes a "bump-on-the-tail" in the proton energy spectra at 0.99 AU from the Sun. We find this population was generated by a CME-driven shock which arrived at 0.99 AU around midnight 18 April. As such this population represents an excellent opportunity to study in isolation, the effects of proton acceleration by the shock. The peak energy of the bump-on-the-tail evolves to progressively lower energies as the shock approaches the observing spacecraft at the inner Lagrange point. Focusing on the evolution of this peak energy we demonstrate a technique which transforms these in-situ spectral observations into a frame of reference co-moving with the shock whilst making allowance for the effects of pitch angle scattering and focusing. The results of this transform suggest the bump-on-the-tail population was not driven by the 15 April activity but was generated or at least modulated by a CME-driven shock which left the Sun on 14 April. The existence of a bump-on-the-tail population is predicted by models in Rice et al. (2003) and Li et al. (2003) which we compare with observations and the results of our analysis in the context of both the 14 April and 15 April CMEs. We find an origin of the bump-on-the-tail at the 14 April CME-driven shock provides better agreement with these modelled predictions although some discrepancy exists as to the shock's ability to accelerate 100 MeV protons. Keywords. Solar physics, astrophysics and astronomy (Energetic particles; Flares and mass ejections) – Space plasma physics (Transport processes)

scholarly journals MESSENGER observations of planetary ion enhancements at Mercury’s northern magnetospheric cusp during Flux Transfer Event Showers

2021 ◽  
Author(s):  
Weijie Sun ◽  
James Slavin ◽  
Anna Milillo ◽  
Ryan Dewey ◽  
Stefano Orsini ◽  
...  
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Transfer Event ◽  
Order Of Magnitude ◽  
In Situ Observations ◽  
Flux Transfer ◽  
Magnetospheric Cusp ◽  
Upward Moving ◽  
Entry Layer

Abstract At Mercury, several processes can release ions and neutrals out of the planet’s surface. Here we present enhancements of dayside planetary ions in the solar wind entry layer during flux transfer event (FTE) “showers” near Mercury’s northern magnetospheric cusp. In this entry layer, solar wind ions are accelerated and move downward (i.e. planetward) toward the cusps, which sputter upward-moving planetary ions within 1 minute. The precipitation rate is enhanced by an order of magnitude during FTE showers and the neutral density of the exosphere can vary by >10% due to this FTE-driven sputtering. These in situ observations of enhanced planetary ions in the entry layer likely correspond to an escape channel of Mercury’s planetary ions, and the large-scale variations of the exosphere observed on minute-timescales by ground-based telescopes. Comprehensive, future multi-point measurements made by BepiColombo will greatly enhance our understanding of the processes contributing to Mercury’s dynamic exosphere and magnetosphere.

MHD and Ion Kinetic Waves in Field-aligned Flows Observed by Parker Solar Probe

2021 ◽  
Vol 922 (2) ◽  
pp. 188
Author(s):  
L.-L. Zhao ◽  
G. P. Zank ◽  
J. S. He ◽  
D. Telloni ◽  
L. Adhikari ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Whistler Wave ◽  
Spectral Energy ◽  
Small Scale ◽  
The Sun ◽  
Fast Mode ◽  
Magnetic Fluctuations ◽  
Background Magnetic Field ◽  
Ion Cyclotron

Abstract Parker Solar Probe (PSP) observed predominately Alfvénic fluctuations in the solar wind near the Sun where the magnetic field tends to be radially aligned. In this paper, two magnetic-field-aligned solar wind flow intervals during PSP’s first two orbits are analyzed. Observations of these intervals indicate strong signatures of parallel/antiparallel-propagating waves. We utilize multiple analysis techniques to extract the properties of the observed waves in both magnetohydrodynamic (MHD) and kinetic scales. At the MHD scale, outward-propagating Alfvén waves dominate both intervals, and outward-propagating fast magnetosonic waves present the second-largest contribution in the spectral energy density. At kinetic scales, we identify the circularly polarized plasma waves propagating near the proton gyrofrequency in both intervals. However, the sense of magnetic polarization in the spacecraft frame is observed to be opposite in the two intervals, although they both possess a sunward background magnetic field. The ion-scale plasma wave observed in the first interval can be either an inward-propagating ion cyclotron wave (ICW) or an outward-propagating fast-mode/whistler wave in the plasma frame, while in the second interval it can be explained as an outward ICW or inward fast-mode/whistler wave. The identification of the exact kinetic wave mode is more difficult to confirm owing to the limited plasma data resolution. The presence of ion-scale waves near the Sun suggests that ion cyclotron resonance may be one of the ubiquitous kinetic physical processes associated with small-scale magnetic fluctuations and kinetic instabilities in the inner heliosphere.

scholarly journals Evidence for Particle Acceleration During Magnetospheric Substorms

1994 ◽  
Vol 142 ◽  
pp. 531-539
Author(s):  
Ramon E. Lopez ◽  
Daniel N. Baker
Keyword(s):  
Solar Wind ◽  
Particle Acceleration ◽  
Energy Release ◽  
Acceleration Of Particles ◽  
Magnetospheric Substorms ◽  
Geomagnetic Tail ◽  
Dissipation Of Energy ◽  
In Situ Observations ◽  
Current Systems

AbstractMagnetospheric substorms represent the episodic dissipation of energy stored in the geomagnetic tail that was previously extracted from the solar wind. This energy release produces activity throughout the entire magnetosphere-ionosphere system, and it results in a wide variety of phenomena such as auroral intensifications and the generation of new current systems. All of these phenomena involve the acceleration of particles, sometimes up to several MeV. In this paper we present a brief overview of substorm phenomenology. We then review some of the evidence for particle acceleration in Earth’s magnetosphere during substorms. Such in situ observations in this most accessible of all cosmic plasma domains may hold important clues to understanding acceleration processes in more distant astrophysical systems.Subject headings: acceleration of particles — Earth — solar wind

Large-scale electron solar wind parameters of the inner heliosphere with Parker Solar Probe/FIELDS

2020 ◽  
Author(s):  
Karine Issautier ◽  
Mingzhe Liu ◽  
Michel Moncuquet ◽  
Nicole Meyer-Vernet ◽  
Milan Maksimovic ◽  
...  
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Statistical Study ◽  
Solar Wind Speed ◽  
The Sun ◽  
Solar Wind Parameters ◽  
Power Law Index ◽  
Probe Mission ◽  
Inner Heliosphere

<p>We present in situ properties of electron density and temperature in the inner heliosphere obtained during the three first solar encounters at 35 solar radii of the Parker Solar Probe mission. These preliminary results, recently shown by Moncuquet et al., ApJS, 2020, are obtained from the analysis of the plasma quasi-thermal noise (QTN) spectrum measured by the radio RFS/FIELDS instrument along the trajectories extending between 0.5 and 0.17 UA from the Sun, revealing different states of the emerging solar wind, five months apart. The temperature of the weakly collisional core population varies radially with a power law index of about -0.8, much slower than adiabatic, whereas the temperature of the supra-thermal population exhibits a much flatter radial variation, as expected from its nearly collisionless state. These measured temperatures are close to extrapolations towards the Sun of Helios measurements.</p><p>We also present a statistical study from these in situ electron solar wind parameters, deduced by QTN spectroscopy, and compare the data to other onboard measurements. In addition, we focus on the large-scale solar wind properties. In particular, from the invariance of the energy flux, a direct relation between the solar wind speed and its density can be deduced, as we have already obtained based on Wind continuous in situ measurements (Le Chat et al., Solar Phys., 2012). We study this anti-correlation during the three first solar encounters of PSP.</p>

scholarly journals The RPW Low Frequency Receiver (LFR) on Solar Orbiter: in-situ LF electric and magnetic field measurements of the solar wind expansion

2020 ◽  
Author(s):  
Thomas Chust ◽  
Olivier Le Contel ◽  
Matthieu Berthomier ◽  
Alessandro Retinò ◽  
Fouad Sahraoui ◽  
...  
Keyword(s):  
Solar Wind ◽  
Low Frequency ◽  
Field Measurements ◽  
Solar Wind Plasma ◽  
Wind Condition ◽  
The Sun ◽  
Nasa Mission ◽  
Magnetic Field Measurements ◽  
Electric And Magnetic Field

<p>Solar Orbiter (SO) is an ESA/NASA mission for exploring the Sun-Heliosphere connection which has been launched in February 2020. The Low Frequency Receiver (LFR) is one of the main subsystems of the Radio and Plasma Wave (RPW) experiment on SO. It is designed for characterizing the low frequency (~0.1Hz–10kHz) electromagnetic fields & waves which develop, propagate, interact, and dissipate in the solar wind plasma. In correlation with particle observations it will help to understand the heating and acceleration processes at work during its expansion. We will present the first LFR data gathered during the Near Earth Commissioning Phase, and will compare them with MMS data recorded in similar solar wind condition.</p>

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