Generation of high‐frequency electric field activity by turbulence in the Earth's magnetotail

• Published in: Journal of geophysical research. Space physics 2015-03, Vol.120 (3), p.1845-1866
• Main Authors: Stawarz, J. E., Ergun, R. E., Goodrich, K. A.
• Format: Article
• Language: English
• Subjects: Alfvén waves; Braking; bursty bulk flows; double layers; Electric fields; Energy dissipation; flow braking; Fluid dynamics; Fluid flow; Geophysics; Magnetohydrodynamics; magnetotail; Nonlinearity; Plasma physics; Turbulence; Turbulent flow
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1002/2014JA020166

Bursty bulk flow (BBF) events, frequently observed in the magnetotail, carry significant energy and mass from the tail region at distances that are often greater than 20 RE into the near‐Earth plasma sheet at ∼10 RE where the flow is slowed and/or diverted. This region at ∼10 RE is referred to as the BBF braking region. A number of possible channels are available for the transfer or dissipation of energy in BBF events including adiabatic heating of particles, the propagation of Alfvén waves out of the BBF braking region and into the auroral region, diverted flow out of the braking region, and energy dissipation within the braking region itself. This study investigates the generation of intense high‐frequency electric field activity observed within the braking region. When present, these intense electric fields have power above the ion cyclotron frequency and almost always contain nonlinear structures such as electron phase space holes and double layers, which are often associated with field‐aligned currents. A hypothesis in which the observed high‐frequency electric field activity is generated by field‐aligned currents resulting from turbulence in the BBF braking region is considered. Although linear Alfvén waves can generate field‐aligned currents, based on theoretical calculations, the required currents are likely not the result of linear waves. Observations from the Time History of Events and Macroscale Interactions during Substorms satellites support the picture of a turbulent plasma leading to the generation of nonlinear kinetic structures. This work provides a possible mechanism for energy dissipation in turbulent plasmas. Key Points Strong electric field activity generated by intense field‐aligned currents Intense currents generated by turbulence in bursty bulk flow braking region This work provides mechanism for energy dissipation in turbulent plasmas