Observations of the relationship between ionospheric central polar cap and dayside throat convection velocities, and solar wind/IMF driving

Bristow, W. A.; Amata, E.; Spaleta, J.; Marcucci, M. F.

doi:10.1002/2015ja021199

Cited by 3 publications

(5 citation statements)

References 28 publications

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“…Bristow et al . [] reported the same result with respect to

B_{z}^{-}

convection driver. Their opinion is that the central polar cap plasma flows are affected by substorm processes.…”

Section: Discussionsupporting

confidence: 67%

“…This is one of the reasons that we selected in this study two (relatively new) SuperDARN radars at DCE and MCM that have ample of data in the central polar cap. The only problematic period for the flow monitoring is winter darkness time [ Bristow et al ., ; Bristow et al ., ]. The SuperDARN radars in the Northern Hemisphere hardly detect echoes in the near magnetic pole area [e.g., Ghezelbash et al ., ] although they provide useful information at magnetic latitudes equatorward of ~83°.…”

Section: Discussionmentioning

confidence: 99%

“…Importantly, irrespective of the radar station and/or magnetic latitude of measurements, the maximum LOS velocity magnitudes are about the same, up to 300 m/s for

B_{z}^{-}

conditions and up to 200 m/s for

B_{z}^{+}

conditions. Lower velocity magnitude for

B_{z}^{+}

conditions is a well‐known feature of high‐latitude convection [e.g., Bristow et al ., ; Koustov et al ., ]. All the radars show winter maxima for antisunward flows (months 6 and 18 for DCE and MCM in the summer hemisphere and months 12 and 24 for RKN in the winter hemisphere) for both

B_{z}^{-}

and

B_{z}^{+}

conditions.…”

Section: Typical Meridional Los Velocity For Imf Bz− and Bz+mentioning

confidence: 98%

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

2017

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We use Super Dual Auroral Radar Network data to study polar cap ionospheric flow under strongly dominant positive interplanetary magnetic field Bz component. We show that the near‐noon flow along the magnetic meridian is predominantly sunward in summer. The sunward velocity increase with intensification of the external driver (the reverse convection electric field) is also faster in summer, and the rate of the increase is slightly larger for the Southern Hemisphere. The sunward flows simultaneously detected in both hemispheres are faster in the summer hemisphere. In addition, while sunward flows are aligned with the midnight‐noon line in a winter hemisphere, they are oriented toward earlier magnetic local hours in a summer hemisphere.

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“…Bristow et al . [] reported the same result with respect to

B_{z}^{-}

convection driver. Their opinion is that the central polar cap plasma flows are affected by substorm processes.…”

Section: Discussionsupporting

confidence: 67%

Section: Discussionmentioning

confidence: 99%

“…Importantly, irrespective of the radar station and/or magnetic latitude of measurements, the maximum LOS velocity magnitudes are about the same, up to 300 m/s for

B_{z}^{-}

conditions and up to 200 m/s for

B_{z}^{+}

conditions. Lower velocity magnitude for

B_{z}^{+}

B_{z}^{-}

and

B_{z}^{+}

conditions.…”

Section: Typical Meridional Los Velocity For Imf Bz− and Bz+mentioning

confidence: 98%

See 1 more Smart Citation

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

2017

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“…To insure that the SHF prior does not overly influence the solution, the variance values are set artificially high, usually σ > 150 m/s. This value was chosen based upon the observed range of plasma flow velocity for a given value of IMF driving [ Bristow et al , ].…”

Section: Local Divergence‐free Fittingmentioning

confidence: 99%

High‐spatial‐resolution velocity measurements derived using Local Divergence‐Free Fitting of SuperDARN observations

2016

Self Cite

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A new technique for analysis of Super Dual Auroral Radar Network (SuperDARN) line‐of‐sight velocity observations enables resolving plasma convection with unprecedented spatial resolution. The technique, Local Divergence‐Free Fitting (LDFF), can be used to produce maps with a spatial resolution that is determined by the resolution of the observations rather than an arbitrary fit order. Other techniques, which express the potential as a sum of harmonic functions, limit the number of functions in the expansion to the fit order. Doing so imposes a limit on the minimum size of features that will be represented in the results. The LDFF technique is not limited by this constraint. Rather, it is limited by the resolution of the observations and the amount of regularization required by the observed noise level, which generally allows finer‐scale features to be represented. The LDFF technique is described and then applied to a synthetic data set to demonstrate its validity. Then high‐resolution convection maps are presented from an interval during which auroral observations over Alaska showed poleward boundary intensifications (PBIs) and auroral streamers. Overlays of the convection vectors on the auroral images illustrate correspondence between flow features and the auroral luminosity. Detailed comparison between the flows and images showed that the PBIs originated from polar cap boundary arcs that extended away from midnight toward earlier local times. As the arcs extended they were accompanied by enhanced shear flow. The arcs intensified then moved equatorward becoming streamers. As the arcs moved, the region of shear flow followed their motion, indicating a pattern of field‐aligned current associated with the moving arc. The observations are the most comprehensive and detailed known to the authors for such an interval and agree well with the expected plasma flows based upon magnetospheric simulations. Flow vectors generated for the interval by the spherical harmonic fit technique for the most part do not show the direct relationship between the convection and the localized luminosity features nearly as well as the LDFF results. Some of the features found in the LDFF fitting are simply not present in the results from the global fits. The LDFF technique should find application in a variety of studies where high‐spatial‐resolution estimates of plasma flows are required. The example study presented here, which examined the details of flows in the region of auroral arcs, is representative of such problems.

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“…The period of 1 h was chosen to be consistent with previous studies investigating flows in the polar cap region (e.g. Bristow et al, 2015). A 1-hour interval helps to overcome propagation delay uncertainties from the measurement location of the satellite to the point at which the observed IMF begins to drive flows in the ionosphere.…”

Section: Interplanetary Magnetic Field Data and Dipole Tilt Anglementioning

confidence: 99%

A statistical study of polar cap flow channels observed in both hemispheres using SuperDARN radars

Herlingshaw¹,

Baddeley²,

Oksavik³

et al. 2022

J. Space Weather Space Clim.

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This paper details the first large scale, interhemispheric statistical study into ionospheric fast flow (>900 m/s) channels in the polar cap using the SuperDARN radar network. An automatic algorithm was applied to 6 years of data (2010 – 2016) from 8 SuperDARN radars with coverage in the polar cap regions in both hemispheres. Over 17,000 flow channels were detected, the majority of which occurred in the dayside polar cap region. To determine a statistical relationship between the flow channels and the IMF, a Monte Carlo simulation was used to generate probability distribution functions for IMF conditions and dipole tilt angles. These were used as a baseline for comparisons with IMF conditions associated with the flow channels. This analysis showed that fast flow channels are preferentially driven by IMF By dominant conditions, suggesting that a magnetic tension force on the newly reconnected field lines is required to accelerate the ionospheric plasma to the high speeds on the dayside. The flow channels also occur preferentially during disturbed IMF conditions. Large populations of flow channels were observed on the flanks of the polar cap region. This indicates that significant momentum transfer from the magnetosphere can routinely occur on open field lines on the flanks, far from the dayside and nightside reconnection regions.

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Observations of the relationship between ionospheric central polar cap and dayside throat convection velocities, and solar wind/IMF driving

Cited by 3 publications

References 28 publications

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

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

High‐spatial‐resolution velocity measurements derived using Local Divergence‐Free Fitting of SuperDARN observations

A statistical study of polar cap flow channels observed in both hemispheres using SuperDARN radars

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Observations of the relationship between ionospheric central polar cap and dayside throat convection velocities, and solar wind/IMF driving

Cited by 3 publications

References 28 publications

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

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

High‐spatial‐resolution velocity measurements derived using Local Divergence‐Free Fitting of SuperDARN observations

A statistical study of polar cap flow channels observed in both hemispheres using SuperDARN radars

Contact Info

Product

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

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