scholarly journals The dynamics of current carriers in standing Alfvén waves: Parallel electric fields in the auroral acceleration region

2002 ◽  
Vol 107 (A7) ◽  
Author(s):  
Andrew N. Wright
Keyword(s):  
Electric Fields ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Acceleration Region ◽  
Auroral Acceleration Region

scholarly journals Assessing the global Alfvén wave power flow into and out of the auroral acceleration region during geomagnetic storms

2019 ◽  
Vol 5 (6) ◽  
pp. eaav8411 ◽  
Author(s):  
Andreas Keiling ◽  
Scott Thaller ◽  
John Wygant ◽  
John Dombeck
Keyword(s):  
Energy Flow ◽  
Geomagnetic Storms ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Societal Implications ◽  
Alfvén Waves ◽  
Acceleration Region ◽  
Large Space ◽  
Fourfold Increase ◽  
Auroral Acceleration Region

Geomagnetic storms are large space weather events with potentially tremendous societal implications. During these storms, the transfer of energy from the solar wind into geospace is largely increased, leading to enhanced energy flow and deposition within the magnetosphere and ionosphere. While various energy forms participate, the rate of total Alfvén wave energy flowing into the auroral acceleration region—where the magnetosphere and ionosphere couple—has not been quantified. Here, we report a fourfold increase in hemispherical Alfvénic power (from 2.59 to 10.05 GW) over a largely expanded oval band covering all longitudes and latitudes between 50° and 85° during the main storm phase compared with nonstorm periods. The Poynting flux associated with individual Alfvén waves reached values of up to about 0.5 W/m2 (mapped to ionospheric altitude). These results demonstrate that Alfvén waves are an important component of geomagnetic storms and associated energy flow into the auroral acceleration region.

scholarly journals An Auroral Alfvén Wave Cascade

2021 ◽  
Vol 8 ◽  
Author(s):  
C. C. Chaston
Keyword(s):  
Space Plasma ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Acceleration Region ◽  
Electrical Currents ◽  
Auroral Acceleration Region ◽  
Field Lines ◽  
Auroral Arcs

Folding, kinking, curling and vortical optical forms are distinctive features of most bright auroral displays. These forms are symptomatic of non-linear forcing of the plasma above auroral arcs resulting from the intensification of electrical currents and Alfvén waves along high-latitude geomagnetic field-lines during periods of disturbed space weather. Electrons accelerated to energies sufficient to carry these currents impact the atmosphere and drive visible emission with spatial structure and dynamics that replicate the morphology and time evolution of the plasma region where the acceleration occurs. Movies of active auroral displays, particularly when combined with conjugate in-situ fields and plasma measurements, therefore capture the physics of a driven, non-linearly evolving space plasma system. Here a perspective emphasizing the utility of combining in-situ measurements through the auroral acceleration region with high time and spatial resolution auroral imaging for the study of space plasma turbulence is presented. It is demonstrated how this special capacity reveals the operation of a cascade of vortical flows and currents through the auroral acceleration region regulated by the physics of Alfvén waves similar to that thought to operate in the Solar wind.

scholarly journals Large parallel electric fields, currents, and density cavities in dispersive Alfvén waves above the aurora

2007 ◽  
Vol 112 (A5) ◽  
pp. n/a-n/a ◽  
Author(s):  
C. C. Chaston ◽  
A. J. Hull ◽  
J. W. Bonnell ◽  
C. W. Carlson ◽  
R. E. Ergun ◽  
...  
Keyword(s):  
Electric Fields ◽  
Alfven Waves ◽  
Alfvén Waves

scholarly journals Thermal electron anisotropy driven by kinetic Alfven waves in the Earth's magnetotail

2020 ◽  
Author(s):  
Alexander Lukin ◽  
Anton Artemyev ◽  
Evgeny Panov ◽  
Rumi Nakamura ◽  
Anatoly Petrukovich ◽  
...  
Keyword(s):  
Electric Fields ◽  
Electromagnetic Waves ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Plasma Flows ◽  
Thermal Electron ◽  
Electron Population ◽  
Electron Field ◽  
Kinetic Alfvén Waves

Abstract. Thermal and subthermal electron populations in the Earth's magnetotail are usually characterized by pronounced field-aligned anisotropy that contributes to generation of strong electric currents within the magnetotail current sheet. Formation of this anisotropy requires electron field-aligned acceleration, and thus likely involves field-aligned electric fields. Such fields can be carried by various electromagnetic waves generated by fast plasma flows interacting with ambient magnetotail plasma. In this paper we consider one of the most intense observed wave emissions, kinetic Alfven waves, that often accompany fast plasma flows in the magnetotail. Using two tail seasons (2017, 2018) of MMS observations we have collected statistics of 80 fast plasma flows (or bursty bulk flows) events with distinctive enhancement of intensity of broadband electromagnetic waves (kinetic Alfven waves). We show correlation the intensity of electric fields of kinetic Alfven waves and characteristics of electron anisotropy distributions: the parallel electron anisotropy increases with magnitude of the wave parallel electric field. Also the energy range of this electron anisotropic population is well within the expected acceleration range for assumed kinetic Alfven waves. Our results indicate an important role of KAWs in production of thermal field-aligned electron population typically observed in the Earth's magnetotail.

Hybrid magnetohydrodynamic–kinetic model of standing shear Alfvén waves

2003 ◽  
Vol 69 (4) ◽  
pp. 277-304 ◽  
Author(s):  
PETER A. DAMIANO ◽  
R. D. SYDORA ◽  
J. C. SAMSON
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Cold Plasma ◽  
Electron Distribution Function ◽  
Alfven Waves ◽  
Mhd Equations ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Model Parameters ◽  
Shear Alfven Waves

We have developed a hybrid magnetohydrodynamics (MHD) –kinetic box model valid for standing shear Alfvén waves using the cold plasma MHD equations coupled to a system of kinetic electrons. The guiding centre equations are used for the motion of the electrons and the system is closed via an expression for the field-aligned electric field in terms of the perpendicular electric field and moments of the electron distribution function. The perpendicular electric fields are derived from the ideal MHD approximation. We outline the basic model equations and method of solution. Simulations are then presented comparing the hybrid model results with a cold plasma MHD model. Landau damping is shown to heavily damp the standing shear Alfvén wave in the hybrid simulations when $v_{th} \ge V_{A}$. The damping rate is shown to be in good agreement with the theoretical rate calculated for the model parameters.

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