The relationship between interhemispheric asymmetries in polar ionospheric convection and the magnetic field line footpoint displacement field

Laundal, K. M.; Madelaire, Michael; Ohma, Anders; Reistad, Jone Peter; Hatch, Spencer

doi:10.3389/fspas.2022.957223

Cited by 3 publications

(3 citation statements)

References 54 publications

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“…In our study we make V 0 vary within that range in order to reproduce the balance between corotation and return flow for various geomagnetic conditions. As for the corotation speed V corotation , which only varies with geographic latitude, we set it to an approximate value of 158 m/s at 70° MLat (Laundal et al., 2022). By choosing a latitude typically within the auroral region, we ensure that the estimated corotation speed corresponds to its value in the magnetospheric PS.…”

Section: Discussionmentioning

confidence: 99%

Auroral Oval Morphology: Dawn‐Dusk Asymmetry Partially Induced by Earth's Rotation

et al. 2023

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The auroral oval morphology has been investigated in previous studies presenting maps of average auroral precipitation. However, such distributions tend to emphasize auroral intensity rather than the actual extent of the auroral oval. We develop a statistical method to characterize the auroral oval morphology by using 20 years of electron energy flux measurements from the Defense Meteorological Satellite Program/Special Sensor J (DMSP/SSJ); instead of relying on auroral oval boundaries, we derive the probability of observing aurora from a threshold of 2.109 eV/cm2/s/sr above which the total energy flux of electrons (in the energy range 1–30 keV) is defined as aurora. We then investigate the auroral occurrence probability (AOP) in the magnetic latitude‐magnetic local time (MLat‐MLT) sectors covered by DMSP for various conditions related to geomagnetic activity. Regardless of those conditions, the AOP distributions reveal a width asymmetry with a wider dawn‐to‐noon sector (06–12 MLT) compared to the dusk‐to‐midnight sector (18–24 MLT), the dawn preference getting even more pronounced as the geomagnetic activity decreases. In the context of an open magnetosphere, we investigate the relation between the observed extent asymmetry in the auroral oval and the magnetospheric plasma convection. Representing the plasma sheet magnetic flux as a one‐dimensional fluid subject to production on the nightside (closing of flux via reconnection) and loss on the dayside (opening of flux), we highlight similarities with the AOP in terms of MLT asymmetries. Finally, making use of this fluid model, we demonstrate that the corotation influence on the plasma convection pattern is consistent with the dawn‐dusk asymmetry observed in the AOP distributions.

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Section: Discussionmentioning

confidence: 99%

Auroral Oval Morphology: Dawn‐Dusk Asymmetry Partially Induced by Earth's Rotation

et al. 2023

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“…We assume a dipole magnetic field with mean magnetic field B 0 = 30 μT. In this example, we have transformed the electric potential and velocity field to an inertial frame by adding corotation (Laundal et al, 2022b). The decay factor, β, is set to 1/(3 h), i.e., the plasma decay factor is such that it takes 3 h for the plasma to decay by factor 1/e.…”

Section: Example: Solving the 2d Continuity Equationmentioning

confidence: 99%

The Lompe code: A Python toolbox for ionospheric data analysis

Hovland

Laundal

Reistad

et al. 2022

Front. Astron. Space Sci.

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A recent paper by Laundal et al. (2022c) presented a new technique to combine all available measurements of polar ionospheric electrodynamics; magnetic field measurements from ground and space, ionospheric convection data from radars and satellites, and conductance measurements; to a full 2D map within analysis regions of arbitrary resolution and extent. The technique, called Local Mapping of Polar Ionospheric Electrodynamics (Lompe), is implemented in Python (Laundal et al., 2022a). The Lompe technique combines spherical elementary current system analysis, finite element analysis on a cubed-sphere projection, the use of empirical models like the International Geomagnetic Reference Field, and visualization tools. In this paper, we go through these different components of the Lompe code and show how they are useful on their own, for example in the analysis of ground magnetometer data or data from the upcoming Electrojet Zeeman Imaging Explorer mission. We also demonstrate how to use the Lompe code to produce a coherent picture of ionospheric electrodynamics.

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“…Several other factors could contribute to the differences in the ionospheric electric potential between the northern and southern hemispheres. A previous study has shown that the mismatch in the ionospheric potential could come from the distortion of the geomagnetic field that creates the displacement in the ionospheric footprint (Laundal et al., 2022). Some other studies have also been dedicated to estimating the accuracy of the Tsyganenko model in terms of magnetic conjugacy and magnetic field vectors (Ganushkina et al., 2013; Němec & Kotková, 2021).…”

Section: Introductionmentioning

confidence: 99%

The Hemispheric Difference in Electric Potential and Electron Precipitation Observed by DMSP in the Auroral Zone

Chen,

Heelis,

Hairston

et al. 2023

JGR Space Physics

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In this case study, we focus on how hemispheric differences in the electric potential distribution in the auroral zones are related to hemispheric differences in the energetic particle precipitation that indicate the presence of field‐aligned potential drops. Utilizing data during the spring and fall equinox in 2013 and 2014 from the Defense Meteorological Satellite Program (DMSP) F16 and F17 satellites, we systematically examine simultaneous measurements of plasma drift velocity and particle precipitation in magnetically conjugate regions across the auroral zone in both hemispheres. This allows us to establish the degree to which the interhemispheric differences in ionospheric electric potential may be accounted for by field‐aligned potential drops. Thirty‐seven eligible cases examined show accelerated electron energy spectra at conjugate locations in the northern and/or southern hemispheres. Of these 37 cases, 23 show conjugate differences in electric potential that agree qualitatively with the observed electron acceleration and average energy of precipitating electrons in each hemisphere. This result suggests that the hemispheric differences in ionospheric electric potential in the auroral zone may be most frequently accounted for by field‐aligned potential drops along the magnetic flux tubes connecting conjugate points to the equatorial plane. The spatial and temporal variability of the potential distribution, electron precipitation, and magnetic field configuration could account for deviations from the normally observed situation in the remaining cases. More magnetically conjugate observations at various altitudes in both hemispheres are needed to investigate this hemispheric coupling in more detail.

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The relationship between interhemispheric asymmetries in polar ionospheric convection and the magnetic field line footpoint displacement field

Cited by 3 publications

References 54 publications

Auroral Oval Morphology: Dawn‐Dusk Asymmetry Partially Induced by Earth's Rotation

Auroral Oval Morphology: Dawn‐Dusk Asymmetry Partially Induced by Earth's Rotation

The Lompe code: A Python toolbox for ionospheric data analysis

The Hemispheric Difference in Electric Potential and Electron Precipitation Observed by DMSP in the Auroral Zone

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