Ultralow Frequency Electrodynamics of Magnetosphere‐Ionosphere Interactions Near the Plasmapause During Substorms

Мишин

2020

JGR Space Physics

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Ultralow frequency (ULF) electromagnetic waves are regularly detected by satellites near the plasmapause during substorms. Usually, the small‐scale waves are observed embedded in the large‐scale, quasi‐stationary electric field. We suggest that the small‐scale waves are generated in the ionosphere by the interactions between the large‐scale field and irregularities in the ionospheric density/conductivity. Under certain conditions, these waves can be trapped in the global magnetospheric resonator and amplified by the positive feedback interactions with the ionosphere. To verify this hypothesis, we model with a two‐fluid magnetohydrodynamics code structure and amplitude of the ULF waves simultaneously observed near the plasmapause by the Defense Meteorological Satellite Program satellite at low altitudes and the Combined Release and Radiation Effects satellite at high altitudes. Simulations reproduce in good, quantitative detail the structure and amplitude of the observed waves. In particular, simulations reproduce a “spiky” character of the electric field observed by the Defense Meteorological Satellite Program satellite at low altitude, which is a characteristic feature of ULF waves produced by the ionospheric feedback instability.

Section: Introductionmentioning

confidence: 82%

ULF Waves Generated Near the Plasmapause by the Magnetosphere‐Ionosphere Interactions

Мишин

2020

JGR Space Physics

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“…Their presence with two SAID channels can be understood using the observation that the inner boundary of the substorm plasma sheet is controlled by the plasmapause (e.g., Mishin, ), while the plasmapause is controlled by the cross‐tail,

E_{C}

, and SAID/SAPS electric fields (Goldstein et al, ). Figuratively, the plasmapause acts as a magnetosphere “power plant” (Streltsov & Mishin, ) converting the kinetic energy of earthbound‐ejected mesoscale plasma flows (MPFs) into the SAID electric field as follows.…”

Section: Discussionmentioning

confidence: 99%

“…The magnetospheric part describes dispersive Alfvén waves in an axisymmetric dipole magnetic field using equations for the electron parallel momentum and continuity of the density and current. The ionospheric part is given by a system of equations, which connects the electric field and the plasma density in the ionosphere with the FAC density,

j_{false‖}

, and forms a positive feedback loop,

δ normalΣ false(δ n false) \to δ j_{false‖} \to δ n

(see Streltsov & Mishin (,b) for details).…”

Section: Modeling the Picket Fence Structurementioning

confidence: 99%

“…In a 2‐D model, without the Hall current, the Pedersen current, which closes the east‐west‐aligned sheets of upward and downward FACs, has the form of a strip between the current sheets. Thus, the IFI‐generated structures are simply east‐west‐aligned strips of smaller dimensions determined by the wavelength of the most unstable Alfvén wave (Streltsov & Mishin, ; Streltsov & Foster, ; Streltsov & Mishin, , b). With a finite Hall conductance, the total ionospheric current flows under some angle to the direction of the driving field,

E_{X}

.…”

Section: Modeling the Picket Fence Structurementioning

confidence: 99%

See 1 more Smart Citation

STEVE and the Picket Fence: Evidence of Feedback‐Unstable Magnetosphere‐Ionosphere Interaction

Mishin

Geophysical Research Letters

2019

This paper aims to extend the understanding of Strong Thermal Emission Velocity Enhancement (STEVE) and the Picket Fence related to strong subauroral ion drifts (SAID). We numerically demonstrated that precipitating energetic electrons are critical for the structuring of the Picket Fence. It is created by feedback-unstable magnetosphere-ionosphere interactions driven by the SAID electric field when the Hall conductance created by energetic (≥1 keV) electrons exceeds the Pedersen conductance. We show that thermal excitation of the red-line emission in STEVE is inhibited by inelastic collisions with molecular nitrogen. Suprathermal (≤500 eV) electrons coming from the turbulent plasmasphere appear to be the major source. We also show that the chemiluminescencent and radiative attachment reactions do not explain the short-wavelength part of the STEVE continuum and argue that accounting for vibrational excitation may resolve the problem. Atmosphere's upwelling due to enhanced ion-neutral drag leads to the increased abundance of molecular components relative to atomic oxygen.

“…Once created in the equatorial magnetosphere, the electric field propagates along the magnetic field into the ionosphere. That is, the plasmapause works as a power plant converting via short‐circuiting the kinetic energy of MPFs into subauroral electromagnetic energy (Streltsov & Mishin, ).…”

Section: Introductionmentioning

confidence: 99%

Prebreakup Arc Intensification due to Short Circuiting of Mesoscale Plasma Flows Over the Plasmapause

Mishin

2020

JGR Space Physics

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The prebreakup arc at the inner edge of the auroral boundary is intensified upon arrival of an auroral streamer-the ionospheric signature of the earthbound mesoscale plasma flows (MPF). Yet the cause of electron precipitation enhancement only in this region remains unclear. We suggest that the intensified precipitation comes from the turbulent plasmasphere boundary layer (TPBL) that forms due to short circuiting of MPFs over the presubstorm plasmapause and overlaps with the plasma sheet (PS) inner boundary. Resonance interaction of the PS electrons with intense low-frequency plasma waves leads to enhanced precipitation from this narrow region. Indeed, the DMSP spacecraft observations near the substorm onset show intensified electron fluxes in a narrow region near the auroral boundary, which maps into the TPBL. The same pattern observed in conjunction with postonset auroral streamers points to the common mechanism, which is the short-circuiting process. Therefore, we suggest that the enhanced precipitation into the prebreakup arc is causally related to the MPFs' short circuiting over the plasmapause.We examine this problem using a concept of MPFs' short circuiting over the plasmapause (Mishin & Puhl-Quinn, 2007;Mishin et al., 2010Mishin, 2013) that explains the essential features of subauroral ion drifts (SAID). In this concept, low-ram pressure MPFs penetrate into the inner magnetosphe owing to the polarization field emerging at the forefront, as established in laboratory experiments (e.g., Brenning et al., 2005). This self-similar process breaks apart when the dense cold plasma at the presubstorm plasmapause shorts out the polarization charge. As a result, the MPF's (hot) electrons come to a halt hereby creating a steep, energy-independent PS/auroral boundary (cf. Newell & Meng, 1987), which is close to the prebreakup boundary owing to the steep density gradient at the plasmapause.The inflowing MPF's electrons pile up near the stopping point and create a narrow peak in the electron pressure, which creates the electron diamagnetic drift driving intense plasma turbulence (Mishin et al., 2010;Mishin & Sotnikov, 2017). Meanwhile, the MPF's ions move further inward until the nascent SAID electric field stops them. Thus, SAID inside of the plasmapause emerge just before the substorm breakup or pseudobreakup. Once created in the equatorial magnetosphere, the electric field propagates along the magnetic field into the ionosphere. That is, the plasmapause works as a power plant converting via short-circuiting the kinetic energy of MPFs into subauroral electromagnetic energy (Streltsov & Mishin, 2018).Most important for the purpose of this paper is that intense plasma waves develop in a narrow boundary layer (TPBL) enclosing the plasmapause around the MPF's stopping point (Mishin et al., 2010;Mishin, 2013). The TPBL overlaps with the PS inner edge, thence resonance wave-particle interactions cause enhanced precipitation into the prebreakup arc. This assumption is investigated in the rest of this paper using selected DMSP