Seasonal effect for polar cap sunward plasma flows at strongly northward IMF <i>B<sub>z</sub></i>

Koustov, A. V.; Yakymenko, K.; Ponomarenko, P. V.

doi:10.1002/2016ja023556

Cited by 9 publications

(22 citation statements)

References 46 publications

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“…We find the magnitude of the reverse convection cells to strengthen with increasing dipole tilt in agreement with previous empirical studies (Crooker & Rich, 1993;Pettigrew et al, 2010). Recent studies by Koustov et al (2017) and Yakymenko et al (2018) using polar radar observations confirm this seasonal preference; however, they also report a deviation of the sunward flows toward prenoon MLTs in the summer hemisphere. Our results disagree, instead suggesting a prenoon orientation for negative dipole tilt (i.e., winter-like) conditions only.…”

Section: Discussionsupporting

confidence: 91%

“…Our results disagree, instead suggesting a prenoon orientation for negative dipole tilt (i.e., winter‐like) conditions only. This discrepancy could be attributed to the limited number of events considered by Koustov et al (, 3) and Yakymenko et al (, 12) compared to the much larger number of northward IMF intervals in our strongest E sw bins (Figures m–o).…”

Section: Discussionmentioning

confidence: 57%

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Statistical Patterns of Ionospheric Convection Derived From Mid‐latitude, High‐Latitude, and Polar SuperDARN HF Radar Observations

2018

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Over the last decade, the Super Dual Auroral Radar Network (SuperDARN) has undergone a dramatic expansion in the Northern Hemisphere with the addition of more than a dozen radars offering improved coverage at mid‐latitudes (50°–60° magnetic latitude) and in the polar cap (80°–90° magnetic latitude). In this study, we derive a statistical model of ionospheric convection (TS18) using line‐of‐sight velocity measurements from the complete network of mid‐latitude, high‐latitude, and polar radars for the years 2010–2016. These climatological patterns are organized by solar wind, interplanetary magnetic field (IMF), and dipole tilt angle conditions. We find that for weak solar wind driving conditions the TS18 model patterns are largely similar to the average patterns obtained using high‐latitude radar data only. For stronger solar wind driving the inclusion of mid‐latitude radar data at the equatorward extent of the ionospheric convection can increase the measured cross‐polar cap potential (ΦPC) by as much as 40%. We also derive an alternative model organized by the Kp index to better characterize the statistical convection under a range of magnetic activity conditions. These Kp patterns exhibit similar IMF By dependencies as the TS18 model results and demonstrate a linear increase in ΦPC with increasing Kp for a given IMF orientation. Overall, the mid‐latitude radars provide a better specification of the flows within the nightside Harang reversal region for moderate to strong solar wind driving or geomagnetic activity, while the polar radars improve the quality of velocity measurements in the deep polar cap under all conditions.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 57%

Statistical Patterns of Ionospheric Convection Derived From Mid‐latitude, High‐Latitude, and Polar SuperDARN HF Radar Observations

2018

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“…As an example, we note that the effect of the Hall polarization field by latitudinal gradient might help understanding an unexplained characteristic seen in sunward flows (the reverse convection cell) reported by Koustov et al () and Yakymenko et al (). The reverse convection cell, consisting of the dawn negative and dusk positive cells, is a cell system in the dayside high‐latitude region during dominant northward IMF‐Bz and is thought to be associated with the lobe cell.…”

Section: Discussionmentioning

confidence: 99%

“…The reverse convection cell, consisting of the dawn negative and dusk positive cells, is a cell system in the dayside high-latitude region during dominant northward IMF-Bz and is thought to be associated with the lobe cell. By using the Super Dual Auroral Rader Network (SuperDARN) data (Greenwald et al, 1995), Koustov et al (2017) and Yakymenko et al (2018) showed that polar cap sunward flows between dawn and dusk reverse cells markedly shift from the noon-midnight meridian toward the prenoon sector in the summer hemisphere, while they show no such preference in the winter hemisphere.…”

Section: Clockwise Rotationmentioning

confidence: 99%

Deformation of Ionospheric Potential Pattern by Ionospheric Hall Polarization

Nakamizo

Yoshikawa

2019

JGR Space Physics

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The present study shows that the ionospheric Hall polarization can deform the high‐latitude ionospheric convection field, which is widely considered to be a manifestation of the convection field in the magnetosphere. We perform the Hall polarization field separation with a potential solver by changing the conductance distribution step by step from a uniform one to a more realistic one. We adopt dawn‐dusk and north‐south symmetric distributions of conductance and region 1 (R1) field‐aligned current (FAC). The pair of the primary field of the R1 system and each gradient of off‐diagonal component of conductance tensor (Hall conductance) generates the Hall polarization field and consequently causes potential deformations as follows. (a) The equatorward gradient causes clockwise rotation. (b) The gradient across the terminator, together with the effect of the equatorward gradient, causes the dawn‐dusk asymmetry. (c) The high conductance band in the auroral region causes kink‐type deformations. In particular, a nested structure at the equatorward edge of the band in the midnight sector well resembles the Harang Reversal. Result (a) can explain the clockwise bias inexplicable by the IMF‐By effect alone, the combination of (a) and (b) can explain the clearness and unclearness in the round or crescent shapes of the dawn‐dusk cells depending on the IMF‐By polarity, and (c) suggests that the ionosphere may not need the upward‐FAC for the formation of the Harang Reversal. We suggest that the final structure of the ionospheric potential is established by the combined effects of the magnetospheric requirements (external causes) and ionospheric polarization (internal effect).

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“…It is desirable to examine the influence on the convection pattern by dipole tilt angle Ψ , since Ψ has a large influence on the lobe reconnection process (Crooker & Rich, 1993; Koustov et al., 2017; Reistad, Laundal, Østgaard, Ohma, Thomas, et al., 2019; Wilder et al., 2010; Yakymenko et al., 2018). However, the correlation between Ψ and MLT of the Cluster orbit produces highly uneven sampling of the high latitude regions when Ψ is large.…”

Section: Methodsmentioning

confidence: 99%

Quantifying the Lobe Reconnection Rate During Dominant IMF B_y Periods and Different Dipole Tilt Orientations

et al. 2021

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Lobe reconnection is usually thought to play an important role in geospace dynamics only when the Interplanetary Magnetic Field (IMF) is mainly northward. This is because the most common and unambiguous signature of lobe reconnection is the strong sunward convection in the polar cap ionosphere observed during these conditions. During more typical conditions, when the IMF is mainly oriented in a dawn‐dusk direction, plasma flows initiated by dayside and lobe reconnection both map to high‐latitude ionospheric locations in close proximity to each other on the dayside. This makes the distinction of the source of the observed dayside polar cap convection ambiguous, as the flow magnitude and direction are similar from the two topologically different source regions. We here overcome this challenge by normalizing the ionospheric convection observed by the Super Dual Aurora Radar Network (SuperDARN) to the polar cap boundary, inferred from simultaneous observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). This new method enable us to separate and quantify the relative contribution of both lobe reconnection and dayside/nightside (Dungey cycle) reconnection during periods of dominating IMF By. Our main findings are twofold. First, the lobe reconnection rate can typically account for 20% of the Dungey cycle flux transport during local summer when IMF By is dominating and IMF Bz ≥ 0. Second, the dayside convection relative to the open/closed boundary is vastly different in local summer versus local winter, as defined by the dipole tilt angle.

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Seasonal effect for polar cap sunward plasma flows at strongly northward IMF B_z

Cited by 9 publications

References 46 publications

Statistical Patterns of Ionospheric Convection Derived From Mid‐latitude, High‐Latitude, and Polar SuperDARN HF Radar Observations

Statistical Patterns of Ionospheric Convection Derived From Mid‐latitude, High‐Latitude, and Polar SuperDARN HF Radar Observations

Deformation of Ionospheric Potential Pattern by Ionospheric Hall Polarization

Quantifying the Lobe Reconnection Rate During Dominant IMF B_y Periods and Different Dipole Tilt Orientations

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Seasonal effect for polar cap sunward plasma flows at strongly northward IMF Bz

Cited by 9 publications

References 46 publications

Statistical Patterns of Ionospheric Convection Derived From Mid‐latitude, High‐Latitude, and Polar SuperDARN HF Radar Observations

Statistical Patterns of Ionospheric Convection Derived From Mid‐latitude, High‐Latitude, and Polar SuperDARN HF Radar Observations

Deformation of Ionospheric Potential Pattern by Ionospheric Hall Polarization

Quantifying the Lobe Reconnection Rate During Dominant IMF By Periods and Different Dipole Tilt Orientations

Contact Info

Product

Resources

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Seasonal effect for polar cap sunward plasma flows at strongly northward IMF B_z

Quantifying the Lobe Reconnection Rate During Dominant IMF B_y Periods and Different Dipole Tilt Orientations