Turbulent Plasmasphere Boundary Layer
Evgeny Mishin* and Anatoly Streltsov**
*Space Vehicles Directorate
**Embry- Riddle Aeronautical University
Paper # SA41C- 3495DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution ABSTRACT • Observations of plasma turbulence and heated/accelerated plasma particles in the plasmasphere boundary layer formed by reconnection- injected mesoscale hot plasma flows (MPFs) penetrating into the plasmasphere are presented. • Free energy comes from the electron diamagnetic current in the entry layer near the plasma sheet boundary, diamagnetic ion current near the inner boundary of the layer, and anisotropic (sometimes ring-like) ion distributions inside, and further inward of, the inner boundary. • Collisionless heating of the plasmaspheric particles gives downward heat and suprathermal electron fluxes sufficient to provide the F-region electron temperature greater than 6000 K. This leads to the formation of specific density troughs in the ionospheric regions in the absence of strong electric fields and upward plasma flows. • Small-scale MHD wave structures (SAPSWS) and irregular density troughs emerge on the duskside, coincident with the substorm current wedge development. Numerical simulations show that the ionospheric feedback instability significantly contributes to the SAPSWS formation.
Mishin, E. (2013), Interaction of substorm injections with the subauroral geospace: 1. Multispacecraft observations of SAID, J. Geophys. Res. Space Physics, 118, 10.1002/jgra.50548. Mishin, E., Y. Nishimura, and J. Foster (2017), SAPS/SAID revisited: A causal relation to the substorm current wedge, J. Geophys. Res. Space Physics, 122, doi:10.1002/2017JA024263. Mishin, E., and V. Sotnikov (2017), The turbulent plasmasphere boundary layer and the outer radiation belt boundary, Plasma Phys. Control. Fusion, 59, 124003, doi:10.1088/1361-6587/aa8481. Streltsov, A., & Mishin, E. (2018). Ultralow frequency electrodynamics of magnetosphere-ionosphere interactions near the plasmapause during substorms. J. Geophys. Res.: Space Physics, 123. The plasmasphere boundary layer: A power plant in the magnetosphere CRRES, Polar, Cluster, and Van Allen Probes observations strongly suggest that the plasmapause serves as a power plant in the magnetosphere converting kinetic energy of the magnetotail mesoscale plasma flows (MPFs) into the large-scale electric field. Schematic of the energy conversion on the plasmapause Substorm Injections: Mesoscale (∆Y< 3RE) Plasma Flows (MPFs)
Magnetotail reconnection: The region around the X-line
Low-β jets of a finite width, ∆Y, moving across a magnetic barrier B(x)||Z , maintain motion with the bulk speed v0||X due to the polarization field EY=-v0xB, which builds up in the front (numerous laboratory experiments).
Kinetic energy
Electric energy Short Circuiting over the Plasmapause
The polarization field builds up if the ambient plasma is unable to neutralize the polarization charge at the front. When the cold plasma density at the plasmapause exceeds ~5-10 cm-3, the polarization field is shorted out, so that the MPF’s electrons are arrested and the abrupt, dispersionless Plasma Sheet (auroral) boundary is formed.
The MPF’s (hot) ions continue moving into the plasmasphere devoid of the hot electrons. Charge neutrality is supported by the cold plasma. The subauroral electric field emerges to support the short-circuit current system in the plasmasphere. Enhanced plasma turbulence provides anomalous circuit resistivity and magnetic diffusion. Short Circuiting
Short circuiting occurs at nambient > nc = nMPF/Ac [Rozhanskii, 1986]
El. `collision’ width frequency
In the plasmasphere, ‘collisions’ are due to wave-particle interactions
To match the -3-3.5 observations ν ≅ 10 ωpe ≅ ωLHR Short-Circuiting Observations Ion de-magnetization
εmin (η) ≅e∆Φ (η) penetration of unmagnetized ions through a potential barrier
η SAID system of reference η
n0 = nc at η=0
De-magnetization of hot ions and prompt magnetic diffusion, as in plasmoid-magnetic barrier experiments [Mishin et al., 1986; Brenning et al., 2005]. orbit chaotization
Mishin, 2013 Entry Layer
. As the hot plasma inflow continues, the hot electrons accumulate near the PS boundary creating the electron pressure peak. . In a steady state, the Pressure hot electron pressure peak buildup is balanced by the diamagnetic drift resulting in tens nA/m2 azimuthal currents excitation of lower hybrid, fast magnetosonic, and EMIC waves in the entry layer. Entry Layer (cont)
. Diamagnetic lower hybrid drift instability results in the anomalous collision frequency
LHR 10fci Sotnikov et al., 1980
The r.m.s. amplitude in ν ≅ω the entry layer e LHR 0.7 mV/m
. Heating and acceleration of the plasmasphere’s particles The “hot zone” near the plasmapause The “hot zone” in the ionosphere
A scenario of subauroral ionospheric heating due to wave-particle Ionospheric structures during the SAID events interactions in the TPBL on (A) 8 April 2004 and (B) 18 March 2002 and 17 March 2013. Alfvénic features near the plasmapause
RBSP-A observations of small-scale Alfvénic features near the plasmapause during the St. Patrick’s day 2015 major storm (03/17/2015 event).
Mishin, E., Nishimura, Y. & Foster, J. (2017). SAPS/SAID revisited: A causal relation to the substorm current wedge. J. Geophys. Res.: Space Physics, 122. Two-Fluid MHD Modeling
A two-fluid MHD model describes the positive ionospheric feedback instability driven by the large- scale electric field Summary
Short-circuiting of reconnection-injected mesoscale plasma flows over the plasmapause results in formation of the turbulent plasmaspheric boundary layer (TPBL) and enhanced subauroral electric fields.
The plasmapause serves as a power plant in the magnetosphere converting kinetic energy of the mesoscale plasma flows into the large- scale electric field.
Enhanced plasma turbulence provides anomalous circuit resistivity and magnetic diffusion, as well as heating and acceleration of cold plasma particles.