Effects of geographic‐geomagnetic pole offset on ionospheric outflow: Can the ionosphere wag the magnetospheric tail?

Barakat, A. R.; Eccles, J. V.; Schunk, R. W.

doi:10.1002/2015gl065736

Cited by 19 publications

(22 citation statements)

References 27 publications

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“…Heating due to solar illumination changes the scale height of the ionosphere and enables ionospheric outflow (Maes et al, 2015). As solar illumination is modulated by the geomagnetic dipole, the dipole tilt angle also plays an important role in cold ion outflow (e.g., Barakat, Eccles, & Schunk, 2015;Kitamura et al, 2011). In addition, simulations by Cnossen and Richmond (2012) suggest that the dipole tilt angle modulating the efficiency of solar wind-magnetosphere coupling could influence Joule heating in the polar ionosphere.…”

Section: Introductionmentioning

confidence: 99%

Cold Ion Outflow Modulated by the Solar Wind Energy Input and Tilt of the Geomagnetic Dipole

Wei

André

et al. 2017

JGR Space Physics

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The solar wind energy input into the Earth's magnetosphere‐ionosphere system drives ionospheric outflow, which plays an important role in both the magnetospheric dynamics and evolution of the atmosphere. However, little is known about the cold ion outflow with energies lower than a few tens of eV, as the direct measurement of cold ions is difficult because a spacecraft gains a positive electric charge due to the photoemission effect, which prevents cold ions from reaching the onboard detectors. A recent breakthrough in the measurement technique using Cluster spacecraft revealed that cold ions dominate the ion population in the magnetosphere. This new technique yields a comprehensive data set containing measurements of the velocities and densities of cold ions for the years 2001–2010. In this paper, this data set is used to analyze the cold ion outflow from the ionosphere. We found that about 0.1% of the solar wind energy input is transformed to the kinetic energy of cold ion outflow at the topside ionosphere. We also found that the geomagnetic dipole tilt can significantly affect the density of cold ion outflow, modulating the outflow rate of cold ion kinetic energy. These results give us clues to study the evolution of ionospheric outflow with changing global magnetic field and solar wind condition in the history.

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Section: Introductionmentioning

confidence: 99%

Cold Ion Outflow Modulated by the Solar Wind Energy Input and Tilt of the Geomagnetic Dipole

Wei

André

et al. 2017

JGR Space Physics

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“…During geomagnetic storms, which occur more frequently in the equinoctial months, more energy is deposited from the magnetosphere. The large offset between the geographic and geomagnetic poles could facilitate the coupling between the ionosphere‐magnetosphere and the solar wind and probably induce a stronger response of plasma drifts to external drivers during geomagnetic storms (Ridley et al, ; Barakat et al, ; Bruinsma et al, ). When IMF B Z is southward ( B Z < 0), the upward ion drifts in the two hemispheres vary oppositely when the direction of IMF B Y component changes (Figure ), this is also consistent with the Svalgaard‐Mansurov effect.…”

Section: Observations and Discussionmentioning

confidence: 99%

“…Based on measurements from the Fast Auroral Snapshot satellite, Zhao, Jiang, Ding, et al () found that H + upflow intensity is stronger in the NH during geomagnetically quiet times, whereas its enhancement during disturbed times is more dramatic in the SH than that in the NH. In addition, Barakat et al () simulated asymmetrical diurnal variation of the ionospheric ion outflow fluxes and discussed possible contributions of the asymmetric magnetic field between the two hemispheres.…”

Section: Introductionmentioning

confidence: 99%

Hemispheric Asymmetry of the Vertical Ion Drifts at Dawn Observed by DMSP

Liu

Zhang

et al. 2018

JGR Space Physics

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Based on the measurements from Defense Meteorological Satellite Program (DMSP) F12, F13, and F15 satellites in 1995–2014, we report significant hemispheric asymmetries in vertical ion drift velocity (Vz) at dawn (0500–0700 solar local time) in geomagnetic and geographic coordinates. Vz is distributed in 0300–0900 magnetic local time sector in both the northern (NH) and southern (SH) hemispheres. The north‐south asymmetries are persistent no matter under what kind of seasonal, solar activity, and IMF conditions. In the polar cap, downward Vz is stronger in the SH. Such difference shows clear IMF BY dependence and is more significant in the local winter and/or under low solar activity conditions. In the geomagnetic coordinates, the auroral zone is dominated by upward Vz in the NH but by downward Vz in the SH statistically. In the geographic coordinates, the geographic longitudinal variation of Vz is more pronounced in the SH. The seasonal variations of high‐latitude Vz are different in the NH and SH. The average asymmetric feature of Vz largely depends on the occurrence and magnitude of ion upflow/outflow, which are modulated by the combined effects of the asymmetric magnetic field configuration between the two hemispheres, and the dynamic processes in the tightly coupled ionosphere‐thermosphere system, and their (probably nonlinear) interactions with each other.

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“…Barakat et al [] used the generalized polar wind model to simulate ionospheric outflow during the 28 September 2002 storm, close to equinox conditions. They focused on the effects of the offset between the geographic and the magnetic axes on the ionospheric ion outflow into the magnetosphere.…”

Section: Introductionmentioning

confidence: 99%

“…They examined the disturbance dynamo intensity as a function of UT and season and found significant variation in the magnitude of these electric fields for similar activity levels. Barakat et al [2015] used the generalized polar wind model to simulate ionospheric outflow during the 28 September 2002 storm, close to equinox conditions. They focused on the effects of the offset between the geographic and the magnetic axes on the ionospheric ion outflow into the magnetosphere.…”

Section: Introductionmentioning

confidence: 99%

Geomagnetic disturbance intensity dependence on the universal timing of the storm peak

et al. 2016

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The role of universal time (UT) dependence on storm time development has remained an unresolved question in geospace research. This study presents new insight into storm progression in terms of the UT of the storm peak. We present a superposed epoch analysis of solar wind drivers and geomagnetic index responses during magnetic storms, categorized as a function of UT of the storm peak, to investigate the dependency of storm intensity on UT. Storms with Dst minimum less than −100 nT were identified in the 1970–2012 era (305 events), covering four solar cycles. The storms were classified into six groups based on the UT of the minimum Dst (40 to 61 events per bin) then each grouping was superposed on a timeline that aligns the time of the minimum Dst. Fifteen different quantities were considered: seven solar wind parameters and eight activity indices derived from ground‐based magnetometer data. Statistical analyses of the superposed means against each other (between the different UT groupings) were conducted to determine the mathematical significance of similarities and differences in the time series plots. It was found that the solar wind parameters have no significant difference between the UT groupings, as expected. The geomagnetic activity indices, however, all show statistically significant differences with UT during the main phase and/or early recovery phase. Specifically, the 02:00 UT groupings are stronger storms than those in the other UT bins. That is, storms are stronger when the Asian sector is on the nightside (American sector on the dayside) during the main phase.

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Effects of geographic‐geomagnetic pole offset on ionospheric outflow: Can the ionosphere wag the magnetospheric tail?

Cited by 19 publications

References 27 publications

Cold Ion Outflow Modulated by the Solar Wind Energy Input and Tilt of the Geomagnetic Dipole

Cold Ion Outflow Modulated by the Solar Wind Energy Input and Tilt of the Geomagnetic Dipole

Hemispheric Asymmetry of the Vertical Ion Drifts at Dawn Observed by DMSP

Geomagnetic disturbance intensity dependence on the universal timing of the storm peak

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