scholarly journals Energetic particle parallel diffusion in a cascading wave turbulence in the foreshock region

2007 ◽  
Vol 14 (5) ◽  
pp. 587-601 ◽  
Author(s):  
F. Otsuka ◽  
Y. Omura ◽  
O. Verkhoglyadova
Keyword(s):  
Solar Wind ◽  
Pitch Angle ◽  
Homogeneous Model ◽  
Bow Shock ◽  
Isotropic Scattering ◽  
Wave Turbulence ◽  
Small Scale ◽  
Dimensional System ◽  
Inverse Cascade ◽  
Background Magnetic Field

Abstract. We study parallel (field-aligned) diffusion of energetic particles in the upstream of the bow shock with test particle simulations. We assume parallel shock geometry of the bow shock, and that MHD wave turbulence convected by the solar wind toward the shock is purely transverse in one-dimensional system with a constant background magnetic field. We use three turbulence models: a homogeneous turbulence, a regular cascade from a large scale to smaller scales, and an inverse cascade from a small scale to larger scales. For the homogeneous model the particle motions along the average field are Brownian motions due to random and isotropic scattering across 90 degree pitch angle. On the other hand, for the two cascade models particle motion is non-Brownian due to coherent and anisotropic pitch angle scattering for finite time scale. The mean free path λ|| calculated by the ensemble average of these particle motions exhibits dependence on the distance from the shock. It also depends on the parameters such as the thermal velocity of the particles, solar wind flow velocity, and a wave turbulence model. For the inverse cascade model, the dependence of λ|| at the shock on the thermal energy is consistent with the hybrid simulation done by Giacalone (2004), but the spatial dependence of λ|| is inconsistent with it.

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 Energetic particle sounding of the magnetospheric cusp with ISEE-1

2007 ◽  
Vol 25 (5) ◽  
pp. 1175-1182 ◽  
Author(s):  
K. E. Whitaker ◽  
T. A. Fritz ◽  
J. Chen ◽  
M. Klida
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Pitch Angle ◽  
Energetic Particle ◽  
Bow Shock ◽  
Local Magnetic Field ◽  
Slow Solar Wind ◽  
Energetic Ions ◽  
Cusp Region ◽  
Magnetospheric Cusp

Abstract. Observations on 30 October 1978 show the ISEE-1 spacecraft passing though the high-altitude dayside northern magnetospheric cusp region from roughly 16:00 to 18:30 UT, during a slow solar wind period (~380 km/s). More than two orders of magnitude enhancements of the cusp energetic particle (CEP) fluxes were observed along with a depressed and turbulent local magnetic field. The observed variations of the pitch angle distributions (PAD) provide a unique opportunity to determine the structure of the cusp and the origin of the CEP. Through a boundary sounding technique, the location and orientation of the cusp poleward (or backside) boundary was observed for almost 10 min during which time it appeared initially to be stationary in the GSM/GSE X-direction and then moved sunward about 0.12 Earth radii (RE). The orientation remained approximately perpendicular to the GSM/GSE X-axis until it was observed to rotate by 60 degrees in ~3 min before ISEE-1 was fully inside the cusp cavity. The cavity itself was filled with CEP fluxes displaying large anisotropies, indicative of their source being located below (Earthward) of the satellite location. The spacecraft entered from the backside of the cusp, then traveled ~4 RE through the cavity, and exited through the "top" of the cavity leaving a region of energetic ions below. The PADs demonstrate that the bow shock cannot be the main source of the observed CEPs. The CEP fluxes were measured at about 8.5 h MLT when the IMF had both an 8–10 nT duskward and southward component.

scholarly journals Turbulence and Microprocesses in Inhomogeneous Solar Wind Plasmas

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 69 ◽  
Author(s):  
Catherine Krafft ◽  
Alexander S. Volokitin ◽  
Gaëtan Gauthier
Keyword(s):  
Solar Wind ◽  
Energetic Electron ◽  
Langmuir Wave ◽  
Solar Wind Plasma ◽  
Density Fluctuations ◽  
Wave Radiation ◽  
Wave Turbulence ◽  
Small Scale ◽  
The Impact ◽  
The Waves

The random density fluctuations observed in the solar wind plasma crucially influence on the Langmuir wave turbulence generated by energetic electron beams ejected during solar bursts. Those are powerful phenomena consisting of a chain of successive processes leading ultimately to strong electromagnetic emissions. The small-scale processes governing the interactions between the waves, the beams and the inhomogeneous plasmas need to be studied to explain such macroscopic phenomena. Moreover, the complexity induced by the plasma irregularities requires to find new approaches and modelling. Therefore theoretical and numerical tools were built to describe the Langmuir wave turbulence and the beam’s dynamics in inhomogeneous plasmas, in the form of a self-consistent Hamiltonian model including a fluid description for the plasma and a kinetic approach for the beam. On this basis, numerical simulations were performed in order to shed light on the impact of the density fluctuations on the beam dynamics, the electromagnetic wave radiation, the generation of Langmuir wave turbulence, the waves’ coupling and decay phenomena involving Langmuir and low frequency waves, the acceleration of beam electrons, their diffusion mechanisms, the modulation of the Langmuir waveforms and the statistical properties of the radiated fields’ distributions. The paper presents the main results obtained in the form of a review.

Energy Dissipation at Filamentary Structures Downstream of the Earth’s Parallel Bow Shock

2021 ◽  
Author(s):  
Harald Kucharek ◽  
Imogen Gingell ◽  
Steven Schwartz ◽  
Charles Farrugia ◽  
Karlheinz Trattner
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Energy Dissipation ◽  
Plasma Heating ◽  
Bow Shock ◽  
Small Scale ◽  
Ion Acceleration ◽  
Current Sheets ◽  
The Earth ◽  
Field Enhancements

<p>While the Earth’s bow shock marks the location at which the solar wind is thermalized, recent publications provided evidence that filamentary structures such as reconnecting current sheets at the shock ramp region may participate in the thermalization process.  Small scale filamentary structures are distinct features that are abundant at the shock and inside the magnetosheath. These structures are not limited to current sheets but include electric and magnetic field enhancements. They may consist of a single or multiple filaments.  They originate from energy dissipation at and downstream of the bow shock, in particular the parallel bow shock. </p><p>We have studied several crossings of the magnetosheath made by the MMS spacecraft, characterising and quantifying the occurrence and consequences of current sheets and field enhancements in terms of local plasma heating and ion acceleration far downstream of the shock. These observations suggest that a combination of current sheet formation, and electric field and magnetic field gradients can contribute to local downstream ion acceleration, and heating. The associated turbulence is likely a consequence of solar wind input parameters. These observations provide evidence that under certain plasma conditions these filamentary structures can play a significant role in thermalizing of the magnetosheath plasma as it propagates further downstream toward the magnetopause, thus augmenting the effect due to the bow shock itself.</p>

scholarly journals Plasma Processes in the Outer Coma

1991 ◽  
Vol 116 (2) ◽  
pp. 1145-1169 ◽  
Author(s):  
A. A. Galeev
Keyword(s):  
Solar Wind ◽  
In Situ Measurements ◽  
Bow Shock ◽  
Alfven Wave ◽  
Wind Loading ◽  
Wave Turbulence ◽  
Collective Plasma

AbstractSpacecraft encounters with comets Giacobini-Zinner and Halley revealed a great variety of collective plasma phenomena accompanying the interaction of the solar wind with comets. In this review, we discuss the theory and in situ measurements of the Alfvén wave turbulence and the solar wind loading by cometary ions, and the structure of the cometary bow shock.

Inverse cascade in simulated MHD turbulence driven by small scale source of magnetic helicity

2016 ◽  
Vol 52 (1) ◽  
pp. 261-268
Author(s):  
R. Stepanov ◽  
◽  
V. Titov ◽  
◽  
Keyword(s):  
Magnetic Helicity ◽  
Small Scale ◽  
Mhd Turbulence ◽  
Inverse Cascade

Dependence of the Properties of a Turbulent Cascade behind the Bow Shock on the Dynamics of the Solar Wind Parameters

2020 ◽  
Vol 58 (6) ◽  
pp. 478-486
Author(s):  
L. S. Rakhmanova ◽  
M. O. Riazantseva ◽  
G. N. Zastenker ◽  
Yu. I. Yermolaev ◽  
I. G. Lodkina
Keyword(s):  
Solar Wind ◽  
Bow Shock ◽  
Solar Wind Parameters ◽  
Turbulent Cascade

scholarly journals Reflection-driven magnetohydrodynamic turbulence in the solar atmosphere and solar wind

2019 ◽  
Vol 85 (4) ◽  
Author(s):  
Benjamin D. G. Chandran ◽  
Jean C. Perez
Keyword(s):  
Solar Wind ◽  
Heating Rate ◽  
Three Dimensional ◽  
Power Spectra ◽  
Inertial Range ◽  
Magnetic Flux Tube ◽  
Analytic Model ◽  
Mhd Turbulence ◽  
Background Magnetic Field ◽  
Turbulent Heating

We present three-dimensional direct numerical simulations and an analytic model of reflection-driven magnetohydrodynamic (MHD) turbulence in the solar wind. Our simulations describe transverse, non-compressive MHD fluctuations within a narrow magnetic flux tube that extends from the photosphere, through the chromosphere and corona and out to a heliocentric distance  $r$ of 21 solar radii  $(R_{\odot })$ . We launch outward-propagating ‘ $\boldsymbol{z}^{+}$ fluctuations’ into the simulation domain by imposing a randomly evolving photospheric velocity field. As these fluctuations propagate away from the Sun, they undergo partial reflection, producing inward-propagating ‘ $\boldsymbol{z}^{-}$ fluctuations’. Counter-propagating fluctuations subsequently interact, causing fluctuation energy to cascade to small scales and dissipate. Our analytic model incorporates dynamic alignment, allows for strongly or weakly turbulent nonlinear interactions and divides the $\boldsymbol{z}^{+}$ fluctuations into two populations with different characteristic radial correlation lengths. The inertial-range power spectra of $\boldsymbol{z}^{+}$ and $\boldsymbol{z}^{-}$ fluctuations in our simulations evolve toward a $k_{\bot }^{-3/2}$ scaling at $r>10R_{\odot }$ , where $k_{\bot }$ is the wave-vector component perpendicular to the background magnetic field. In two of our simulations, the $\boldsymbol{z}^{+}$ power spectra are much flatter between the coronal base and $r\simeq 4R_{\odot }$ . We argue that these spectral scalings are caused by: (i) high-pass filtering in the upper chromosphere; (ii) the anomalous coherence of inertial-range $\boldsymbol{z}^{-}$ fluctuations in a reference frame propagating outwards with the $\boldsymbol{z}^{+}$ fluctuations; and (iii) the change in the sign of the radial derivative of the Alfvén speed at $r=r_{\text{m}}\simeq 1.7R_{\odot }$ , which disrupts this anomalous coherence between $r=r_{\text{m}}$ and $r\simeq 2r_{\text{m}}$ . At $r>1.3R_{\odot }$ , the turbulent heating rate in our simulations is comparable to the turbulent heating rate in a previously developed solar-wind model that agreed with a number of observational constraints, consistent with the hypothesis that MHD turbulence accounts for much of the heating of the fast solar wind.

scholarly journals Magnetosheath pressure pulses: Generation downstream of the bow shock from solar wind discontinuities

2012 ◽  
Vol 117 (A5) ◽  
pp. n/a-n/a ◽  
Author(s):  
M. O. Archer ◽  
T. S. Horbury ◽  
J. P. Eastwood
Keyword(s):  
Solar Wind ◽  
Bow Shock ◽  
Pressure Pulses
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