Detailed dayside auroral morphology as a function of local time for southeast IMF orientation: implications for solar wind-magnetosphere coupling

Sandholt, P. E.; Farrugia, Charles J.; Denig, W. F.

doi:10.5194/angeo-22-3537-2004

Cited by 39 publications

(71 citation statements)

References 72 publications

(131 reference statements)

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“…We shall therefore demonstrate case examples of ion drift and precipitation data obtained during dawn-dusk passes of spacecraft DMSP F13 in both the winter and summer hemispheres. The DMSP observations presented here are a continuation/extension of the preliminary results reported in Sandholt et al (2004) and in Sandholt et al (2006b).…”

Section: Introductionmentioning

confidence: 53%

“…In recent studies we demonstrated the presence of an important extra contribution to the dawn-dusk convection asymmetry and the S-M effect via solar wind -magnetosphere -ionosphere coupling acting on "old open field lines" (Sandholt et al, 2004;Farrugia et al, 2004a;Sandholt et al, 2006b;Sandholt and Farrugia, 2007a,b). This is the few hundred km wide channel of enhanced antisunward convection (our FC 2) which under certain conditions (nonzero IMF B y , ionospheric conductivity gradient) is observed at the dawn/dusk boundaries of the polar cap.…”

Section: Discussionmentioning

confidence: 99%

“…This is the newly discovered channels of enhanced antisunward convection observed on the morning (evening) side of the polar cap during positive (negative) IMF B y condition when we refer to Northern Hemisphere cases (Sandholt et al, 2004;Farrugia et al, 2004a;Sandholt et al, 2006b; P. E. Sandholt and C. J. Farrugia: Plasma flow channels at the dawn/dusk polar cap boundaries 2007a,b; Lund et al, 2008). On the basis of magnetic field and ion drift data obtained during traversals of the polar cap by satellite DMSP F13 we suggested that these flow channels are driven by the ionospheric Pedersen current closure of the HCC-LCC Birkeland current system identified by Taguchi et al (1993), Birkeland currents which flow poleward of the traditional Regions 1 and 2 (R1/R2) currents.…”

Section: Introductionmentioning

confidence: 99%

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Plasma flow channels at the dawn/dusk polar cap boundaries: momentum transfer on old open field lines and the roles of IMF By and conductivity gradients

Sandholt

Farrugia

2009

Ann. Geophys.

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Abstract. Using DMSP F13 data in conjunction with IMF data we investigate the newly discovered channels of enhanced (1.5-3 km/s) antisunward convection occurring at the dawn (06:00-09:00 MLT) or dusk (15:00-18:00 MLT) flanks of the polar cap for different combinations of IMF B y polarity, hemisphere (NH/SH) and the dawn/dusk MLTs. Dawn-side cases where this flow channel appears occur for the following combinations: NH-dawn/B y >0 and SHdawn/B y <0. The dusk-side cases are: NH-dusk/B y <0 and SH-dusk/B y >0. The flow channels are placed in the context of particle precipitation regimes/boundaries and ionospheric conductivity gradients. They are found to be threaded by "old open field lines" ("time since reconnection" >10 min) characterized by polar rain precipitation. In the dawn-side cases (NH-dawn/B y >0 and SH-dawn/B y <0) and in a Parker spiral field, the polar rain contains the "solar wind strahl" component. The convection enhancement is attributed to the Pedersen current closure of Birkeland current sheets (C1 and C2) in the polar cap (C1) and at the polar cap boundary (C2). The low ionospheric conductivity in the polar cap, particularly in the winter hemisphere, is compensated by an enhanced electric field driving the flow channel there. This is momentum transfer from the solar wind via dynamo action taking place in the combined current system of the high-and low-latitude boundary layers (HBL/LLBL). The conductivity gradient at the polar cap boundary contributes to establishing the convection channel and the associated enhancement of the dawn-dusk convection asymmetry extending beyond the dawn-dusk terminator during intervals of nonzero IMF B y component. The HBL/LLBL-ionosphere coupling via Birkeland currents C1/C2 is a source of dawn-dusk convection asymmetry and Svalgaard-Mansurov effect which must Correspondence to: P. E. Sandholt (p.e.sandholt@fys.uio.no) be added to the effect of magnetic tension acting on "newly open field lines".

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Section: Introductionmentioning

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Plasma flow channels at the dawn/dusk polar cap boundaries: momentum transfer on old open field lines and the roles of IMF By and conductivity gradients

Sandholt

Farrugia

2009

Ann. Geophys.

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“…Galperin (2002) proposed a model that explains the formation of PJ or SAPS during magnetic substorms and storms in the evening-tonighttime sector of the discontinuity region between the auroral electrojets. A detailed consideration of the interrelation between auroral luminosity, FAC and PE during magnetic disturbances in the dayside sector was given by Sandholt et al (2004).…”

Section: Current Systems Of Polar Magnetic Disturbancesmentioning

confidence: 99%

Spiral structures and regularities in magnetic field variations and auroras

Feldstein

Gromova

Förster

et al. 2012

Hist. Geo Space. Sci.

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Abstract. The conception of spiral shaped precipitation regions, where solar corpuscles penetrate the upper atmosphere, was introduced into geophysics by C. Størmer and K. Birkeland at the beginning of the last century. Later, in the course of the XX-th century, spiral distributions were disclosed and studied in various geophysical phenomena. Most attention was devoted to spiral shapes in the analysis of regularities pertaining to the geomagnetic activity and auroras.We review the historical succession of perceptions about the number and positions of spiral shapes, that characterize the spatial-temporal distribution of magnetic disturbances. We describe the processes in the upper atmosphere, which are responsible for the appearance of spiral patterns. We considered the zones of maximal aurora frequency and of maximal particle precipitation intensity, as offered in the literature, in their connection with the spirals.We discuss the current system model, that is closely related to the spirals and that appears to be the source for geomagnetic field variations during magnetospheric substorms and storms. The currents in ionosphere and magnetosphere constitute together with field-aligned (along the geomagnetic field lines) currents (FACs) a common 3-D current system. At ionospheric heights, the westward and eastward electrojets represent characteristic elements of the current system. The westward electrojet covers the longitudinal range from the morning to the evening hours, while the eastward electrojet ranges from afternoon to near-midnight hours. The polar electrojet is positioned in the dayside sector at cusp latitudes. All these electrojets map along the magnetic field lines to certain plasma structures in the near-Earth space. The first spiral distribution of auroras was found based on observations in Antarctica for the nighttime-evening sector (N-spiral), and later in the nighttime-evening (N-spiral) and morning (M-spiral) sectors both in the Northern and Southern Hemispheres. The N-and M-spirals drawn in polar coordinates form an oval, along which one observes most often auroras in the zenith together with a westward electrojet.The nature of spiral distributions in geomagnetic field variations was unabmibuously interpreted after the discovery of the spiral's existence in the auroras had been established and this caused a change from the paradigm of the auroral zone to the paradigm of the auroral oval. Zenith forms of auroras are found within the boundaries of the auroral oval. The oval is therefore the region of most frequent precipitations of corpuscular fluxes with auroral energy, where anomalous geophysical phenomena occur most often and with maximum intensity.S. Chapman and L. Harang identified the existence of a discontinuity at auroral zone latitudes (Φ ∼ 67• ) around midnight between the westward and eastward electrojets, that is now known as the Harang discontinuity. After the discovery of the auroral oval and the position of the westward electrojet along the oval, it turned out, that there is no disco...

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“…CC BY 4.0 License. disturbances was given by Sandholt et al (2004). As shown there, the strong convection channel is located on the dawn side of the polar cap for IMF By>0, and on the dusk side for By<0 conditions.…”

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confidence: 99%

Dynamics of the electrojet during intense magnetic disturbances

Gromova

Förster

Feldstein

et al. 2018

Preprint

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The PE is situated at MLat∼73• on the dayside during geomagnetically quiet periods and the recovery phase of a magnetic storm, and it shifts equatorward during intense substorms and 25 the main phase of a storm.6. There is no connection between MLat and the current density I in the PE with the magnetospheric ring current DR (index SYM/H).7. There is a correlation between the current density I in the PE and the partial ring current in the magnetosphere (PRC, index ASYM/H), but practically no correlation of this index with 30MLat of the PE.8. Substorms that occur before and during the beginning of a storm main phase are acompanied in the daytime by the appearance of an eastward electrojet (EE) at MLat∼64• , and then also by a westward electrojet (WE). In the nighttime sector the WE appears at MLat∼64• .9. During the development of the main storm phase, the daytime EE and the nighttime WE shift 35 toward subauroral latitudes of MLat∼56• and intensify up to I∼1.5 A/m. Both electrojets persist during the main phase of the storm. The WE is then located about 6• closer to the pole than the EE during evening hours and about 2 • -3• during daytime hours.Keywords. high-latitude magnetic variations, magnetic storm phases, interplanetary magnetic field, Hall current modelling, equivalent ionospheric currents, current systems in the magnetosphere, polar 40

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Detailed dayside auroral morphology as a function of local time for southeast IMF orientation: implications for solar wind-magnetosphere coupling

Cited by 39 publications

References 72 publications

Plasma flow channels at the dawn/dusk polar cap boundaries: momentum transfer on old open field lines and the roles of IMF <I>B<sub>y</sub></I> and conductivity gradients

Plasma flow channels at the dawn/dusk polar cap boundaries: momentum transfer on old open field lines and the roles of IMF <I>B<sub>y</sub></I> and conductivity gradients

Spiral structures and regularities in magnetic field variations and auroras

Dynamics of the electrojet during intense magnetic disturbances

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Detailed dayside auroral morphology as a function of local time for southeast IMF orientation: implications for solar wind-magnetosphere coupling

Cited by 39 publications

References 72 publications

Plasma flow channels at the dawn/dusk polar cap boundaries: momentum transfer on old open field lines and the roles of IMF &lt;I&gt;B&lt;sub&gt;y&lt;/sub&gt;&lt;/I&gt; and conductivity gradients

Plasma flow channels at the dawn/dusk polar cap boundaries: momentum transfer on old open field lines and the roles of IMF &lt;I&gt;B&lt;sub&gt;y&lt;/sub&gt;&lt;/I&gt; and conductivity gradients

Spiral structures and regularities in magnetic field variations and auroras

Dynamics of the electrojet during intense magnetic disturbances

Contact Info

Product

Resources

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Plasma flow channels at the dawn/dusk polar cap boundaries: momentum transfer on old open field lines and the roles of IMF <I>B<sub>y</sub></I> and conductivity gradients

Plasma flow channels at the dawn/dusk polar cap boundaries: momentum transfer on old open field lines and the roles of IMF <I>B<sub>y</sub></I> and conductivity gradients