Large‐scale imaging of high‐latitude convection with Super Dual Auroral Radar Network HF radar observations

Ruohoniemi, J. M.; Baker, K. B.

doi:10.1029/98ja01288

Cited by 614 publications

(826 citation statements)

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“…The SuperDARN network of HF radars provides almost continuous measurements of ionospheric convection velocities in the auroral regions of the Northern and Southern Hemispheres (Greenwald et al, 1995;Chisham et al, 2007) and this facilitates the routine production of large scale maps of the high-latitude convection using the "Map Potential" technique (Ruohoniemi and Baker, 1998). This technique involves the mapping of line-of-sight radar velocity measurements onto an equal area polar grid and using them to derive a best-fit solution to an nth-order expansion of the electrostatic potential, expressed in spherical harmonics.…”

Section: Resultsmentioning

confidence: 99%

Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

et al. 2009

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Abstract. Using data from the Super Dual Auroral Radar Network (SuperDARN) we investigate the ionospheric convection response to magnetospheric substorms. Substorms were identified using the Far Ultraviolet (FUV) instrument on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, and were then binned according to the magnetic latitude of their onset. A superposed epoch analysis of the ionospheric convection patterns for each onset-latitude bin was then performed using radar data for the interval 60 min before onset to 90 min after. It is found that lower onset-latitude substorms are associated with generally more enhanced convection than the higher latitude substorms, although they suffer from a significant localised reduction of the flow in the midnight sector during the expansion phase. Higher-latitude substorms are associated with a significant and rapid increase in the nightside convection following substorm onset, with all onset-latitude bins showing an enhancement over onset values by ∼60 min into the expansion phase. A rudimentary inspection of the concurrent auroral evolution suggests that the duration of the flow reduction following substorm onset is dependent on the strength and duration of the expansion phase aurora and its associated conductivity enhancement.

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Section: Resultsmentioning

confidence: 99%

Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

et al. 2009

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“…Of relevance to this study are measurements of the line-ofsight velocity of F-region convection flows made by nine of the Northern Hemisphere radars. These are inverted using the spherical harmonic fitting technique described by Ruohoniemi and Baker (1998) to shape modelled electric potentials to produce maps of the ionospheric high-latitude electric potential. The electric potentials for the Northern Hemisphere were then used as input to the CTIP model in the current investigation.…”

Section: Super Dual Auroral Radar Networkmentioning

confidence: 99%

Modelling the tongue-of-ionisation using CTIP with SuperDARN electric potential input: verification by radiotomography

et al. 2009

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Abstract. Electric potential patterns obtained by the SuperDARN radar network are used as input to the Coupled Thermosphere-Ionosphere-Plasmasphere model, in an attempt to improve the modelling of the spatial distribution of the ionospheric plasma at high latitudes. Two case studies are considered, one under conditions of stable IMF B z negative and the other under stable IMF B z positive. The modelled plasma distributions are compared with sets of wellestablished tomographic reconstructions, which have been interpreted previously in multi-instrument studies. For IMF B z negative both the model and observations show a tongueof-ionisation on the nightside, with good agreement between the electron density and location of the tongue. Under B z positive, the SuperDARN input allows the model to reproduce a spatial plasma distribution akin to that observed. In this case plasma, unable to penetrate the polar cap boundary into the polar cap, is drawn by the convective flow in a tongue-of-ionisation around the periphery of the polar cap.

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“…The coordinate system is magnetic local time (MLT) and magnetic latitude (MLAT). To construct the 2-D flow pattern from the radar line of sight velocities, we employ the analysis technique developed by Ruohoniemi and Baker (1998) (see also Greenwald et al, 1995). This technique determines the solution for the distribution of electrostatic potential expressed as a series expansion in spherical harmonics (in our case of the order of 10), constrained by the line of sight measurements of the radars.…”

Section: Data Presentationmentioning

confidence: 99%

Multi-site observations of the association between aurora and plasma convection in the cusp/polar cap during a southeastward(By ~ |Bz|) IMF orientation

et al. 2003

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Abstract. In a case study we demonstrate the spatiotemporal structure of aurora and plasma convection in the cusp/polar cap when the interplanetary magnetic field (IMF) B z < 0 and B y |B z | (clock angle in GSM Y − Z plane: 135 • ). This IMF orientation elicited a response different from that corresponding to strongly northward and southward IMF. Our study of this "intermediate state" is based on a combination of ground observations of optical auroral emissions and ionospheric plasma convection. Utilizing allsky cameras at NyÅlesund, Svalbard and Heiss Island (Russian arctic), we are able to monitor the high-latitude auroral activity within the ∼10:00-15:00 MLT sector. Information on plasma convection is obtained from the SuperDARN radars, with emphasis placed on line of sight observations from the radar situated in Hankasalmi, Finland (Cutlass). A central feature of the auroral observations in the cusp/polar cap region is a ∼30-min long sequence of four brightening events, some of which consists of latitudinally and longitudinally separated forms, which are found to be associated with pulsed ionospheric flows in merging and lobe convection cells. The auroral/convection events may be separated into different forms/cells and phases, reflecting a spatiotemporal evolution of the reconnection process on the dayside magnetopause. The initial phase consists of a brightening in the postnoon sector (∼12:00-14:00 MLT) at ∼73 • MLAT, accompanied by a pulse of enhanced westward convection in the postnoon merging cell. Thereafter, the event evolution comprises two phenomena which occur almost simultaneously: (1) westward expansion of the auroral brightening (equatorward boundary intensification) across noon, into the ∼10:00-12:00 MLT sector, where the plasma convection subsequently turns almost due north, in the convecCorrespondence to: P. E. Sandholt (p.e.sandholt@fys.uio.no) tion throat, and where classical poleward moving auroral forms (PMAFs) are observed; and (2) auroral brightening at slightly higher latitudes (∼75 • MLAT) in the postnoon lobe cell, with expansion towards noon, giving rise to a clear cusp bifurcation. The fading phase of PMAFs is accompanied by a "patch" of enhanced (∼1 km/s) poleward-directed merging cell convection at high latitudes (75-82 • MLAT), e.g. more than 500 km poleward of the cusp equatorward boundary. The major aurora/convection events are recurring at ∼5-10 min intervals.

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Large‐scale imaging of high‐latitude convection with Super Dual Auroral Radar Network HF radar observations

Cited by 614 publications

References 21 publications

Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

Modelling the tongue-of-ionisation using CTIP with SuperDARN electric potential input: verification by radiotomography

Multi-site observations of the association between aurora and plasma convection in the cusp/polar cap during a southeastward(<i>B<sub>y</sub></i> <u>~</u> |<i>B<sub>z</sub></i>|) IMF orientation

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Large‐scale imaging of high‐latitude convection with Super Dual Auroral Radar Network HF radar observations

Cited by 614 publications

References 21 publications

Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

Modelling the tongue-of-ionisation using CTIP with SuperDARN electric potential input: verification by radiotomography

Multi-site observations of the association between aurora and plasma convection in the cusp/polar cap during a southeastward(&lt;i&gt;B&lt;sub&gt;y&lt;/sub&gt;&lt;/i&gt; &lt;u&gt;~&lt;/u&gt; |&lt;i&gt;B&lt;sub&gt;z&lt;/sub&gt;&lt;/i&gt;|) IMF orientation

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Multi-site observations of the association between aurora and plasma convection in the cusp/polar cap during a southeastward(<i>B<sub>y</sub></i> <u>~</u> |<i>B<sub>z</sub></i>|) IMF orientation