A statistical study on O&amp;lt;sup&amp;gt;+&amp;lt;/sup&amp;gt; flux in the dayside magnetosheath

Slapak, Rikard; Nilsson, Hans; Westerberg, Lars-Göran

doi:10.5194/angeo-31-1005-2013

Cited by 21 publications

(31 citation statements)

References 26 publications

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“…The authors mentioned two transport processes leading to ion escape through the plasma sheet: a plasmoid that is formed by a tailward injection of a helical magnetic field structure and the transport of ions coming from the lobe or plasma mantle region to the distant neutral line. Other studies have shown that ion heating and acceleration in the cusp and mantle instead lead to escape into the magnetosheath for these ions (Nilsson et al, 2006Nilsson, 2011;Slapak et al, 2013). A statistical study on O + flux from Slapak et al (2013) estimated the total escape flux observed in the dayside magnetosheath to be ∼ 7 × 10 24 s −1 .…”

Section: Introductionmentioning

confidence: 98%

“…Other studies have shown that ion heating and acceleration in the cusp and mantle instead lead to escape into the magnetosheath for these ions (Nilsson et al, 2006Nilsson, 2011;Slapak et al, 2013). A statistical study on O + flux from Slapak et al (2013) estimated the total escape flux observed in the dayside magnetosheath to be ∼ 7 × 10 24 s −1 . Nilsson (2011) similarly estimated the escaping flux in the cusp and plasma mantle to be of the order of 10 25 s −1 .…”

Section: Introductionmentioning

confidence: 98%

“…The polar cap is the whole region of open magnetic field lines mapping mainly to the magnetotail lobes. Ion outflow occurs from all of these regions, but the oxygen outflow from the cusp and mantle is most intense and also most likely to escape into interplanetary space Slapak et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Relative outflow enhancements during major geomagnetic storms – Cluster observations

et al. 2017

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Abstract. The rate of ion outflow from the polar ionosphere is known to vary by orders of magnitude, depending on the geomagnetic activity. However, the upper limit of the outflow rate during the largest geomagnetic storms is not well constrained due to poor spatial coverage during storm events. In this paper, we analyse six major geomagnetic storms between 2001 and 2004 using Cluster data. The six major storms fulfil the criteria of Dst < −100 nT or Kp > 7+. Since the shape of the magnetospheric regions (plasma mantle, lobe and inner magnetosphere) are distorted during large magnetic storms, we use both plasma beta (β) and ion characteristics to define a spatial box where the upward O + flux scaled to an ionospheric reference altitude for the extreme event is observed. The relative enhancement of the scaled outflow in the spatial boxes as compared to the data from the full year when the storm occurred is estimated. Only O + data were used because H + may have a solar wind origin. The storm time data for most cases showed up as a clearly distinguishable separate peak in the distribution toward the largest fluxes observed. The relative enhancement in the outflow region during storm time is 1 to 2 orders of magnitude higher compared to less disturbed time. The largest relative scaled outflow enhancement is 83 (7 November 2004) and the highest scaled O + outflow observed is 2 × 10 14 m −2 s −1 (29 October 2003).

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 98%

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Relative outflow enhancements during major geomagnetic storms – Cluster observations

et al. 2017

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“…Zong et al (2001), Marcucci et al (2004), Kasahara et al (2008) and Slapak et al (2012). A statistical study of O + in the high-latitude dayside magnetosheath was made by Slapak et al (2013), showing that O + is common, contributing 0.7 × 10 25 s −1 to the total O + escape flux. The total O + escape flux of the mantles and the dayside magnetosheath is similar to the total O + cusp outflow flux of 2 × 10 25 s −1 , as reported by Yau and André (1997).…”

Section: Introductionmentioning

confidence: 99%

“…strongly northward IMF) in order for the mechanism to take place. Slapak et al (2013) made a statistical estimate of the total O + escape flux in the dayside magnetosheath, with the assumption that all observed O + would escape. A central question is whether this assumption is feasible or if O + trapping related to dual-lobe reconnection events is significant.…”

Section: Introductionmentioning

confidence: 99%

O<sup>+</sup> transport in the dayside magnetosheath and its dependence on the IMF direction

et al. 2015

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Abstract. Recent studies have shown that the escape of oxygen ions (O + ) into the magnetosheath along open magnetic field lines from the terrestrial cusp and mantle is significant. We present a study of how O + transport in the dayside magnetosheath depends on the interplanetary magnetic field (IMF) direction. There are clear asymmetries in the O + flows for southward and northward IMF. The asymmetries can be understood in terms of the different magnetic topologies that arise due to differences in the location of the reconnection site, which depends on the IMF direction. During southward IMF, most of the observed magnetosheath O + is transported downstream. In contrast, for northward IMF we observe O + flowing both downstream and equatorward towards the opposite hemisphere. We observe evidence of dual-lobe reconnection occasionally taking place during strong northward IMF conditions, a mechanism that may trap O + and bring it back into the magnetosphere. Its effect on the overall escape is however small: we estimate the upper limit of trapped O + to be 5 %, a small number considering that ion flux calculations are rough estimates. The total O + escape flux is higher by about a factor of 2 during times of southward IMF, in agreement with earlier studies of O + cusp outflow.

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Centrifugal acceleration at high altitudes above the polar cap: A Monte Carlo simulation

Abudayyeh¹,

Barghouthi²,

Slapak³

et al. 2015

JGR Space Physics

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A Monte Carlo simulation was used to study the outflow of O+ and H+ ions along three flight trajectories above the polar cap up to altitudes of about 15 RE. Barghouthi (2008) developed a model on the basis of altitude and velocity‐dependent wave‐particle interactions and a radial geomagnetic field which includes the effects of ambipolar electric field and gravitational and mirror forces. In the present work we improve this model to include the effect of the centrifugal force, with the use of relevant boundary conditions. In addition, the magnetic field and flight trajectories, namely, the central polar cap (CPC), nightside polar cap (NPC), and cusp, were calculated using the Tsyganenko T96 model. To simulate wave‐particle interactions, the perpendicular velocity diffusion coefficients for O+ ions in each region were determined such that the simulation results fit the observations. For H+ ions, a constant perpendicular velocity diffusion coefficient was assumed for all altitudes in all regions as recommended by Nilsson et al. (2013). The effect of centrifugal acceleration was simulated by considering three values for the ionospheric electric field: 0 (no centrifugal acceleration), 50, and 100 mV/m. It was found that the centrifugal acceleration increases the parallel bulk velocity and decreases the parallel and perpendicular temperatures of both ion species at altitudes above about 4 RE. Centrifugal acceleration also increases the temperature anisotropy at high altitudes. At a given altitude, centrifugal acceleration decreases the density of H+ ions while it increases the density of O+ ions. This implies that with higher centrifugal acceleration more O+ ions overcome the potential barrier. It was also found that aside from two exceptions centrifugal acceleration has the same effect on the velocities of both ions. This implies that the centrifugal acceleration is universal for all particles. The parallel bulk velocities at a given value of ionospheric electric field were highest in the cusp followed by the CPC followed by the NPC. In this study a region of no wave‐particle interaction was assumed in the CPC and NPC between 3.7 and 7.5 RE. In this region the perpendicular temperature was found to decrease with altitude due to perpendicular adiabatic cooling.

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A statistical study on O<sup>+</sup> flux in the dayside magnetosheath

Cited by 21 publications

References 26 publications

Relative outflow enhancements during major geomagnetic storms – Cluster observations

Relative outflow enhancements during major geomagnetic storms – Cluster observations

O<sup>+</sup> transport in the dayside magnetosheath and its dependence on the IMF direction

Centrifugal acceleration at high altitudes above the polar cap: A Monte Carlo simulation

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A statistical study on O&lt;sup&gt;+&lt;/sup&gt; flux in the dayside magnetosheath

Cited by 21 publications

References 26 publications

Relative outflow enhancements during major geomagnetic storms – Cluster observations

Relative outflow enhancements during major geomagnetic storms – Cluster observations

O&lt;sup&gt;+&lt;/sup&gt; transport in the dayside magnetosheath and its dependence on the IMF direction

Centrifugal acceleration at high altitudes above the polar cap: A Monte Carlo simulation

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A statistical study on O<sup>+</sup> flux in the dayside magnetosheath

O<sup>+</sup> transport in the dayside magnetosheath and its dependence on the IMF direction