scholarly journals Parametric decay of radial Alfvén waves in the expanding accelerating solar wind

2013 ◽  
Vol 118 (12) ◽  
pp. 7507-7516 ◽  
Author(s):  
A. Tenerani ◽  
M. Velli
Keyword(s):  
Solar Wind ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Parametric Decay

scholarly journals Parametric instability, inverse cascade and the  range of solar-wind turbulence

2018 ◽  
Vol 84 (1) ◽  
Author(s):  
Benjamin D. G. Chandran
Keyword(s):  
Solar Wind ◽  
Nonlinear Evolution ◽  
Parametric Instability ◽  
Alfven Waves ◽  
Turbulence Theory ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Fast Solar Wind ◽  
Parametric Decay ◽  
Inverse Cascade

In this paper, weak-turbulence theory is used to investigate the nonlinear evolution of the parametric instability in three-dimensional low-$\unicode[STIX]{x1D6FD}$ plasmas at wavelengths much greater than the ion inertial length under the assumption that slow magnetosonic waves are strongly damped. It is shown analytically that the parametric instability leads to an inverse cascade of Alfvén wave quanta, and several exact solutions to the wave kinetic equations are presented. The main results of the paper concern the parametric decay of Alfvén waves that initially satisfy $e^{+}\gg e^{-}$, where $e^{+}$ and $e^{-}$ are the frequency ($f$) spectra of Alfvén waves propagating in opposite directions along the magnetic field lines. If $e^{+}$ initially has a peak frequency $f_{0}$ (at which $fe^{+}$ is maximized) and an ‘infrared’ scaling $f^{p}$ at smaller $f$ with $-1<p<1$, then $e^{+}$ acquires an $f^{-1}$ scaling throughout a range of frequencies that spreads out in both directions from $f_{0}$. At the same time, $e^{-}$ acquires an $f^{-2}$ scaling within this same frequency range. If the plasma parameters and infrared $e^{+}$ spectrum are chosen to match conditions in the fast solar wind at a heliocentric distance of 0.3 astronomical units (AU), then the nonlinear evolution of the parametric instability leads to an $e^{+}$ spectrum that matches fast-wind measurements from the Helios spacecraft at 0.3 AU, including the observed $f^{-1}$ scaling at $f\gtrsim 3\times 10^{-4}~\text{Hz}$. The results of this paper suggest that the $f^{-1}$ spectrum seen by Helios in the fast solar wind at $f\gtrsim 3\times 10^{-4}~\text{Hz}$ is produced in situ by parametric decay and that the $f^{-1}$ range of $e^{+}$ extends over an increasingly narrow range of frequencies as $r$ decreases below 0.3 AU. This prediction will be tested by measurements from the Parker Solar Probe.

scholarly journals On heating of solar wind protons by the breaking of large amplitude Alfvén waves

2018 ◽  
Author(s):  
Horia Comişel ◽  
Yasuhiro Nariyuki ◽  
Yasuhito Narita ◽  
Uwe Motschmann
Keyword(s):  
Solar Wind ◽  
Pitch Angle ◽  
Plasma Heating ◽  
Alfven Waves ◽  
Distribution Functions ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Parametric Decay ◽  
Angle Scattering ◽  
Velocity Distribution Functions

Abstract. By means of hybrid simulations, we present a study on plasma heating by the field-aligned parametric decay of a monochromatic left-handed polarized Alfven wave. Simultaneous multidimensional comparisons of the wave modes and proton kinetics suggest that parametric decay of Alfven waves and pitch angle scattering of solar wind protons are interrelated. Parametric decay mechanism yields counter-propagating Alfven waves that can shape and broaden via pitch angle scattering mechanism both the sunward and antisunward sides of the proton velocity distribution functions in agreement with in situ measurements of fast stream solar wind plasmas.

scholarly journals Parametric decay of parallel and oblique Alfvén waves in the expanding solar wind

2014 ◽  
Vol 81 (1) ◽  
Author(s):  
L. Del Zanna ◽  
L. Matteini ◽  
S. Landi ◽  
A. Verdini ◽  
M. Velli
Keyword(s):  
Solar Wind ◽  
Background Field ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Parametric Decay ◽  
Direct Excitation ◽  
Oblique Propagation ◽  
Polarized Waves ◽  
Parallel Propagation ◽  
Local Background

The long-term evolution of large-amplitude Alfvén waves propagating in the solar wind is investigated by performing two-dimensional MHD simulations within the expanding box model. The linear and nonlinear phases of the parametric decay instability are studied for both circularly polarized waves in parallel propagation and for arc-polarized waves in oblique propagation. The non-monochromatic case is also considered. In the oblique case, the direct excitation of daughter modes transverse to the local background field is found for the first time in an expanding environment, and this transverse cascade seems to be favored for monochromatic mother waves. The expansion effect reduces the instability growth rate, and it can even suppress its onset for the lowest frequency modes considered here, possibly explaining the persistence of these outgoing waves in the solar wind.

scholarly journals On the origin of solar wind. Alfvén waves induced jump of coronal temperature

2007 ◽  
Vol 44 (3) ◽  
pp. 533-536 ◽  
Author(s):  
T. M. Mishonov ◽  
M. V. Stoev ◽  
Y. G. Maneva
Keyword(s):  
Solar Wind ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Coronal Temperature

scholarly journals Observations of polar patches generated by solar wind Alfvén wave coupling to the dayside magnetosphere

1999 ◽  
Vol 17 (4) ◽  
pp. 463-489 ◽  
Author(s):  
P. Prikryl ◽  
J. W. MacDougall ◽  
I. F. Grant ◽  
D. P. Steele ◽  
G. J. Sofko ◽  
...  
Keyword(s):  
Solar Wind ◽  
Electric Field ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Convection Cell ◽  
Convection Flow ◽  
Vhf Radar ◽  
Sky Imager ◽  
The Imf

Abstract. A long series of polar patches was observed by ionosondes and an all-sky imager during a disturbed period (Kp = 7- and IMF Bz < 0). The ionosondes measured electron densities of up to 9 × 1011 m-3 in the patch center, an increase above the density minimum between patches by a factor of \\sim4.5. Bands of F-region irregularities generated at the equatorward edge of the patches were tracked by HF radars. The backscatter bands were swept northward and eastward across the polar cap in a fan-like formation as the afternoon convection cell expanded due to the IMF By > 0. Near the north magnetic pole, an all-sky imager observed the 630-nm emission patches of a distinctly band-like shape drifting northeastward to eastward. The 630-nm emission patches were associated with the density patches and backscatter bands. The patches originated in, or near, the cusp footprint where they were formed by convection bursts (flow channel events, FCEs) structuring the solar EUV-produced photoionization and the particle-produced auroral/cusp ionization by segmenting it into elongated patches. Just equatorward of the cusp footprint Pc5 field line resonances (FLRs) were observed by magnetometers, riometers and VHF/HF radars. The AC electric field associated with the FLRs resulted in a poleward-progressing zonal flow pattern and backscatter bands. The VHF radar Doppler spectra indicated the presence of steep electron density gradients which, through the gradient drift instability, can lead to the generation of the ionospheric irregularities found in patches. The FLRs and FCEs were associated with poleward-progressing DPY currents (Hall currents modulated by the IMF By) and riometer absorption enhancements. The temporal and spatial characteristics of the VHF backscatter and associated riometer absorptions closely resembled those of poleward moving auroral forms (PMAFs). In the solar wind, IMP 8 observed large amplitude Alfvén waves that were correlated with Pc5 pulsations observed by the ground magnetometers, riometers and radars. It is concluded that the FLRs and FCEs that produced patches were driven by solar wind Alfvén waves coupling to the dayside magnetosphere. During a period of southward IMF the dawn-dusk electric field associated with the Alfvén waves modulated the subsolar magnetic reconnection into pulses that resulted in convection flow bursts mapping to the ionospheric footprint of the cusp.Key words. Ionosphere (polar ionosphere). Magneto- spheric physics (magnetosphere-ionosphere interactions; polar wind-magnetosphere interactions).

Sign in / Sign up

Export Citation Format

Share Document