Global impact of ionospheric outflows on the dynamics of the magnetosphere and cross‐polar cap potential

Winglee, R. M.; Chua, D.; Brittnacher, M.; Parks, G. K.; Lu, G.

doi:10.1029/2001ja000214

Cited by 127 publications

(178 citation statements)

References 32 publications

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“…This reduction appears to be due to a global reduction in the intensity of the region 1 field-aligned currents and is likely linked to changes in the conductance resulting from the increased plasma density at the low-altitude simulation boundary and its effects on the electron precipitation derived from the LFM precipitation model [Fedder et al, 1995]. As suggested by Winglee et al [2002], another contributing factor may be the mass loading of the magnetosphere by the O + outflow. To isolate this effect, we will have to perform another series of simulations without electron precipitation, i.e., with fixed ionospheric conductance.…”

Section: Discussionmentioning

confidence: 99%

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Influence of cusp O⁺ outflow on magnetotail dynamics in a multifluid MHD model of the magnetosphere

et al. 2010

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[1] A multifluid version of the Lyon-Fedder-Mobarry global simulation model has been used to investigate the effects of outflowing ionospheric O + on the magnetosphereionosphere system. To quantify these effects, we specify the number density, upward parallel velocity, and temperature of the O + outflow in a limited area of the low-altitude simulation boundary representing the projection of cusp, cleft, and low-latitude boundary layer. A baseline simulation without O + outflow is compared with simulations with a range of fluxes and initial velocities. In the cases with high fluxes, it is shown that the configuration of the magnetosphere is dramatically changed. In particular, the cross-polar cap potential is reduced, the polar cap area is increased, and the nightside reconnection line is moved earthward. Furthermore, in one case, the O + outflow leads to the onset of a second substorm not seen in the other simulation runs.

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Section: Discussionmentioning

confidence: 99%

“…Winglee et al [2002] used a multifluid model of the magnetosphere and a gravitationally bound source of O + to study the impact of outflows on the magnetosphere during a storm. They found that O + outflows reduce the cross-polar cap potential and the polar cap area.…”

Section: Introductionmentioning

confidence: 99%

Influence of cusp O⁺ outflow on magnetotail dynamics in a multifluid MHD model of the magnetosphere

et al. 2010

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“…[86] In this model [Winglee et al, 2002] an increase of driving of the magnetosphere by the solar wind causes an increase in the ionospheric-plasma outflow into the magnetosphere and this plasma mass loads magnetosphere convection, which reduces the potential of the magnetosphere and the ionosphere. The present findings contradict this explanation of polar cap saturation in two manners.…”

Section: A17 Ionospheric-outflow Modelmentioning

confidence: 99%

Polar cap potential saturation, dayside reconnection, and changes to the magnetosphere

2009

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[1] Global MHD simulations of the Earth's magnetosphere using the Block-AdaptiveTree Solarwind Roe Upwind Scheme code at the Community Coordinated Modeling Center are run with a high-resolution dayside magnetopause and variable-resolution nearEarth regions to study the phenomena of polar cap saturation. In the simulations a resistive spot is maintained on the moving magnetopause to ensure that the correct dayside reconnection rate is obtained. The solar wind parameters are held fixed, and the ionospheric Pedersen conductivity is varied. Strong reduction of the cross-polar cap potential is observed, with modest increases in the cross-polar cap current, and no changes in the local and global reconnection rates. Changes in the magnetosphere associated with the saturation of the polar cap are explored: these include a weakening of the dayside magnetic field strength, an equatorward shift of the cusps, a flattening in Z of the closed field line region of the dayside magnetosphere, and a taillike stretching of the dipole field lines at the terminator. Measurements of the currents and voltages of the polar cap indicate that the solar wind acts like a current-limited voltage generator. A simple circuit model is analyzed using measurements from the MHD simulations, and physically reasonable values for the circuit elements are obtained. Nine models for polar cap saturation are assessed against the findings of the present study.

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“…High altitude measurements such as those we present in this paper does not directly deal with this controversy regarding the total outflow, as all observed particles have reached escape energy. Our interest lies in the further energization of escaping particles, and their role in the global circulation of mass and energy in the magnetospheric system (Winglee et al, 2002;Winglee, 2004) as well as the final fate of these ions (Ebihara et al, 2006). Delcourt (1994) found that centrifugal effects could be important near the frontside magnetopause.…”

Section: Introductionmentioning

confidence: 99%

An assessment of the role of the centrifugal acceleration mechanism in high altitude polar cap oxygen ion outflow

et al. 2008

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Abstract. The role of the centrifugal acceleration mechanism for ion outflow at high altitude above the polar cap has been investigated. Magnetometer data from the four Cluster spacecraft has been used to obtain an estimate of magnetic field gradients. This is combined with ion moment data of the convection drift and the field-aligned particle velocity. Thus all spatial terms in the expression for the centrifugal acceleration are directly obtained from observations. The temporal variation of the unit vector of the magnetic field is estimated by predicting consecutive measurement-points through the use of observed estimates of the magnetic field gradients, and subtracting this from the consecutively observed value. The calculation has been performed for observations of outflowing O + beams in January to May for the years 2001-2003, and covers an altitude range of about 5 to 12 R E . The accumulated centrifugal acceleration during each orbit is compared with the observed parallel velocities to get an estimate of the relative role of the centrifugal acceleration. Finally the observed spatial terms (parallel and perpendicular) of the centrifugal acceleration are compared with the results obtained when the magnetic field data was taken from the Tsyganenko T89 model instead. It is found that the centrifugal acceleration mechanism is significant, and may explain a large fraction of the parallel velocities observed at high altitude above the polar cap. The magnetic field model results underestimate the centrifugal acceleration at the highest altitudes investigated and show some systematic differences as compared to the observations in the lower altitude ranges investigated. Our results indicate that for altitudes corresponding to magnetic field values of more than 50 nT a test particle Correspondence to: H. Nilsson (hans.nilsson@irf.se) model with a steady state magnetic field model, a realistic convection model and an initial velocity of about 20 k m s −1 at 5 R E should be able to reproduce the main part of our observational results.

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Global impact of ionospheric outflows on the dynamics of the magnetosphere and cross‐polar cap potential

Cited by 127 publications

References 32 publications

Influence of cusp O⁺ outflow on magnetotail dynamics in a multifluid MHD model of the magnetosphere

Influence of cusp O⁺ outflow on magnetotail dynamics in a multifluid MHD model of the magnetosphere

Polar cap potential saturation, dayside reconnection, and changes to the magnetosphere

An assessment of the role of the centrifugal acceleration mechanism in high altitude polar cap oxygen ion outflow

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Global impact of ionospheric outflows on the dynamics of the magnetosphere and cross‐polar cap potential

Cited by 127 publications

References 32 publications

Influence of cusp O+ outflow on magnetotail dynamics in a multifluid MHD model of the magnetosphere

Influence of cusp O+ outflow on magnetotail dynamics in a multifluid MHD model of the magnetosphere

Polar cap potential saturation, dayside reconnection, and changes to the magnetosphere

An assessment of the role of the centrifugal acceleration mechanism in high altitude polar cap oxygen ion outflow

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Product

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Influence of cusp O⁺ outflow on magnetotail dynamics in a multifluid MHD model of the magnetosphere

Influence of cusp O⁺ outflow on magnetotail dynamics in a multifluid MHD model of the magnetosphere