Simulation of O + upflows created by electron precipitation and Alfvén waves in the ionosphere

The relationship between dispersive Alfvén waves (DAWs), magnetospheric activity, and O+ ion outflow/energy density is examined using measurements from the Van Allen Probes. We show that correlated DAW activity and O+ outflow/energization is a characteristic feature of the inner magnetosphere during active conditions and during storms persists for several hours over large L‐shell and azimuthal ranges of the plasma sheet. Though enhanced during substorm and storm active periods, these correlated features are most intense during geomagnetic storms. Comparisons show a linear relationship between DAW electric (and magnetic) field energy density and outflowing O+ energy. Statistical measurements from a large number of storms also reveal a linear relationship between DAW energy density and gross enhancements in energetic O+ energy densities. These observations support the notion that DAWs play an important role in the energization of O+ ions into and within the inner magnetosphere.

Section: Discussionmentioning

confidence: 99%

Dispersive Alfvén Wave Control of O⁺ Ion Outflow and Energy Densities in the Inner Magnetosphere

Hull

Chaston

Bonnell

et al. 2019

“…Observations performed within the ionosphere by radars [Wahlund et al, 1992;Kagan et al, 1996] and rockets [Whalen et al, 1978;Lynch et al, 2007] along with modeling [Sydorenko and Rankin, 2013] have shown how electron precipitation at energies typical of those observed in dispersive Alfvén waves drive collisional heating and outward expansion of ionospheric electrons leading to ion upflows. These upflows may supply ionospheric ions to altitudes where they can experience electric fields in the Alfvén wave sufficient to drive trapping in the wave potential [Lysak, 1986] and/or the breakdown of gyromotion [Cole, 1976;Johnson and Cheng, 2001;Chen et al, 2001].…”

Section: Discussionmentioning

confidence: 99%

Extreme ionospheric ion energization and electron heating in Alfvén waves in the storm time inner magnetosphere

Chaston

Bonnell

Wygant

et al. 2015

We report measurements of energized outflowing/bouncing ionospheric ions and heated electrons in the inner magnetosphere during a geomagnetic storm. The ions arrive in the equatorial plane with pitch angles that increase with energy over a range from tens of eV to > 50 keV while the electrons are field aligned up to ~1 keV. These particle distributions are observed during intervals of broadband low‐frequency electromagnetic field fluctuations consistent with a Doppler‐shifted spectrum of kinetic Alfvén waves and kinetic field line resonances. The fluctuations extend from L ≈ 3 out to the apogee of the Van Allen Probes spacecraft at L ≈ 6.5. They thereby span most of the L shell range occupied by the ring current. These measurements suggest a model for ionospheric ion outflow and energization driven by dispersive Alfvén waves that may account for the large storm time contribution of ionospheric ions to magnetospheric energy density.

“…Note that the polarization term in (5) is different from that used, e.g., in Sydorenko and Rankin [2013] and Lysak [1997]. It is obtained by retaining the first-order time derivative term in the left-hand side of equation (4) in Lysak [1997] and substituting there the stationary drift velocity.…”

Section: Model Descriptionmentioning

confidence: 99%

“…The simulation code developed by Sydorenko and Rankin [2013] is used in this study to investigate the IFI. Chemical reactions, field-aligned ion motion, and heating of electrons and ions are omitted for simplicity.…”

Section: Model Descriptionmentioning

confidence: 99%

“…Here 1,2 are dipole coordinates, h 1,2,3 are dipole metric factors, and subscripts 1, 2, and 3 denote directions along the geomagnetic field, across the field line in the meridional plane, and in the azimuthal direction, respectively; see the definition in Sydorenko and Rankin [2013]. Subscripts e and denote electron and ion species, respectively (the list of ion species includes H + , N + , O + , N + 2 , NO + , and O + 2 ); and Ω denote frequencies of collisions with neutrals and gyromotion, respectively; T is the temperature, and [(u ⋅ ∇)u] 1 is the convective derivative term defined in Sydorenko and Rankin [2013]. In the ion velocity equation (5), the first term in the right-hand side corresponds to the ion polarization current in an Alfvén wave modified by collisions; the second term, where P ≡ e∕m (Ω 2 + 2 ) is the Pedersen mobility, corresponds to the Pedersen conductivity current.…”

Section: Model Descriptionmentioning

confidence: 99%

See 1 more Smart Citation

The stabilizing effect of collision‐induced velocity shear on the ionospheric feedback instability in Earth's magnetosphere

Sydorenko

Rankin

2017

Self Cite

The feedback instability in the ionospheric Alfvén resonator in Earth's magnetosphere is examined using a two‐dimensional multifluid numerical model of coupled ionosphere and magnetosphere. Two simulation configurations are used to demonstrate that the instability occurs under an assumption that is unrealistic for Earth's ionosphere. In the first configuration, a flat sheet height‐integrated conducting boundary replaces the ionospheric E layer. In the second configuration, plasma dynamics in a simplified E layer is resolved ignoring ion production, loss, and diffusion. For the same parameters (plasma and neutral density profiles and convection electric field), the instability develops only with the flat sheet boundary. When the E layer is resolved, the variation of ion‐neutral collision frequencies with altitude produces vertical shear in the horizontal ion flow velocity. The shear prevents density perturbations from remaining field aligned, causing them to decay rather than grow. It is suggested that the instability cannot occur in Earth's ionosphere because ion‐neutral collision frequencies always have a significant variation with altitude through the E layer.