Evidence for a correlation between Sun‐aligned arcs and the interplanetary magnetic field direction

Berkey, F. T.; Cogger, L. L.; Ismail, S.; Kamide, Y.

doi:10.1029/gl003i003p00145

Cited by 93 publications

(54 citation statements)

References 10 publications

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“…It is well established that sun-aligned arcs occur in the polar cap during periods when the IMF has a northward component for more than an hour (LASSEN, 1972;BERKEY et al, 1976;ISMAIL and MENG, 1982;FRANK et al, 1982). The flux of electrons-producing polar cap arcs is typically in the 108 to 109/cm2-s-sr range.…”

Section: Polar Electrodynamics With Northward Imfmentioning

confidence: 99%

Interplanetary control of high latitude electrodynamics.

Burke

Doyle

1986

J. geomagn. geoelec

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This paper reviews recent observational developments concerning the influence of the solar wind (SW) and the interplanetary magnetic (IMF) field on magnetospheric processes. Examples are chosen to demonstrate that the influence of the SW/IMF is global in scope. Subsequent to sudden compressions of the magnetosphere observed by the Dynamics Explorer satellite the entire auroral oval is bombarded by previously trapped particles. Whether this is followed by a main phase storm or a theta aurora depends on the north-south polarity of the IMF . The potential drop across the polar cap is shown to correlate with the interplanetary electric field. However the potential across the polar cap is much less than the potential across the magnetosphere in the solar wind. The influence of the azimuthal component and ionospheric conductivity on the polar cap convection pattern is discussed in terms of recent observations from the Dynamics Explorer satellite . During periods of northward IMF, regions of sunward convection, with an attendant field-aligned current system, are found in the sunlit ionosphere on the day side of the magnetic dawn-dusk meridian. On the night side of this meridian and in the darkened polar cap, electric fields and field-aligned currents show filamentary structures. Electron precipitation in the polar cap varies from nearly uniform polar rain during periods of southward IMF to structured polar rain and sun-aligned arcs when the IMF has a northward component. The theta aurora detected by the imaging system on Dynamics Explorer appears in regions of sunward convection accompanied by downcoming O+ ions. This suggests that the lobes of the magnetotail are bifurcated by closed, plasma sheet field lines. At lower magnetic latitudes the systematics of the equatorward boundary of auroral electron precipitation are indirectly controlled by the interplanetary electric field. For low to moderate levels of KP, reasonable estimates of the polar cap potential may be derived from the positions of this boundary.

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Section: Polar Electrodynamics With Northward Imfmentioning

confidence: 99%

Interplanetary control of high latitude electrodynamics.

Burke

Doyle

1986

J. geomagn. geoelec

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“…The works by Lassen (1972), Berkey et al (1976) and Ismail et al (1977) had previously demonstrated that the sun-aligned F-region arcs existed inside the polar cap preferentially when the magnetic conditions were quiet or equivalently when the B z component of the IMF was directed northward. In analogy to this discovery, Buchau et al (1983) noted that the polar cap patches Ann.…”

Section: Introductionmentioning

confidence: 99%

Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets

Valladares

Alcaydé

Rodriguez³

et al. 1999

Ann Geophysicae

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Abstract. We report important results of the ®rst campaign specially designed to observe the formation and the initial convection of polar cap patches. The principal instrumentation used in the experiments comprised the EISCAT, the Sondrestrom, and the Super DARN network of radars. The experiment was conducted on February 18, 1996 and was complemented with additional sensors such as the Greenland chain of magnetometers and the WIND and IMP-8 satellites. Two dierent types of events were seen on this day, and in both events the Sondrestrom radar registered the formation and evolution of large-scale density structures. The ®rst event consisted of the passage of traveling convection vortices (TCV). The other event occurred in association with the development of large plasma jets (LPJ) embedded in the sunward convection part of the dusk cell. TCVs were measured, principally, with the magnetometers located in Greenland, but were also con®rmed by the line-of-sight velocities from the Sondrestrom and SuperDARN radars. We found that when the magnetic perturbations associated with the TCVs were larger than 100 nT, then a section of the high-latitude plasma density was eroded by a factor of 2. We suggest that the number density reduction was caused by an enhancement in the O + recombination due to an elevated T i , which was produced by the much higher frictional heating inside the vortex. The large plasma jets had a considerable (>1000 km) longitudinal extension and were 200±300 km in width. They were seen principally with the Sondrestrom, and Super-DARN radars. Enhanced ion temperature (T i ) was also observed by the Sondrestrom and EISCAT radars. These channels of high T i were exactly collocated with the LPJs and some of them with regions of eroded plasma number density. We suggest that the LPJs bring less dense plasma from later local times. However, the recent time history of the plasma¯ow is important to de®ne the depth of the density depletion. Systematic changes in the latitudinal location and in the intensity of the LPJs were observed in the 2 min time resolution data of the SuperDARN radars. The eect of the abrupt changes in the LPJs location is to create regions containing dayside plasma almost detached from the rest of the oval density. One of these density features was seen by the Sondrestrom radar at 1542 UT. The data presented here suggest that two plasma structuring mechanisms (TCVs and LPJs) can act tens of minutes apart to produce higher levels of density structures in the near noon F-region ionosphere.

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“…Before that a multitude of localised observations of high-latitude aurora had been made (e.g. Mawson, 1916;Davis, 1960;Denholm, 1961;Denholm and Bond, 1961;Davis, 1963;Eather and Akasofu, 1969;Berkey et al, 1976;Lassen and Danielsen, 1978), but because of the limited field of view of imagers located on the ground or onboard low-altitude spacecraft, the global nature of some of these arcs was not recognised. Valladares et al (1994) performed a comprehensive statistical study of the occurrence of high-latitude arcs and their dependence on the IMF, based on all-sky images.…”

Section: Discussionmentioning

confidence: 99%

“…Frank et al, 1986;Menietti and Burch, 1987;Marklund et al, 1991;Obara et al, 1993;Blomberg and Marklund, 1993;Blomberg and Cumnock, 2005). In addition, as the IMF becomes more northward both the Region 1 to Region 2 and the NBZ to Region 1 current ratios increase (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…For southward IMF the intense auroral activity is usually confined to the region known as the auroral oval, whereas for northward IMF considerable auroral activity is often encountered poleward of this region (e.g. Davis, 1963;Berkey et al, 1976;Lassen and Danielsen, 1978). The existence of auroral arcs at very high latitudes was established early on (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Transpolar aurora: time evolution, associated convection patterns, and a possible cause

et al. 2005

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Abstract. We present two event studies illustrating the detailed relationships between plasma convection, field-aligned currents, and polar auroral emissions, as well as illustrating the influence of the Interplanetary Magnetic Field's ycomponent on theta aurora development. The transpolar arc of the theta aurorae moves across the entire polar region and becomes part of the opposite side of the auroral oval. Electric and magnetic field and precipitating particle data are provided by DMSP, while the POLAR UVI instrument provides measurements of auroral emissions. Ionospheric electrostatic potential patterns are calculated at different times during the evolution of the theta aurora using the KTH model. These model patterns are compared to the convection predicted by mapping the magnetopause electric field to the ionosphere using the Paraboloid Model of the magnetosphere. The model predicts that parallel electric fields are set up along the magnetic field lines projecting to the transpolar aurora. Their possible role in the acceleration of the auroral electrons is discussed.

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Evidence for a correlation between Sun‐aligned arcs and the interplanetary magnetic field direction

Cited by 93 publications

References 10 publications

Interplanetary control of high latitude electrodynamics.

Interplanetary control of high latitude electrodynamics.

Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets

Transpolar aurora: time evolution, associated convection patterns, and a possible cause

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