Polar and Cluster observations of a dayside inverted-V during conjunction

Menietti, J. D.; Frahm, R. A.; Korth, A.; Mozer, F. S.; Khotyaintsev, Yuri V.

doi:10.5194/angeo-25-543-2007

Cited by 3 publications

(3 citation statements)

References 51 publications

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“… Menietti and Smith [1993] presented examples of dayside inverted Vs for IMF B Z negative which they attributed to the low‐latitude boundary layer (LLBL), on closed or freshly open flux. As pointed out in a recent work by Menietti et al [2007] it is still not clear if dayside inverted Vs are magnetically connected to reconnection sites or not. Moen et al [2004a] observed the connection between PMAFs and ion up‐flow events observed by ESR.…”

Section: Discussionmentioning

confidence: 94%

“…(2) The quasi‐stationary nature and the bipolar form of the RFE flow disturbance seem consistent with an inverted V type potential structure. Inverted Vs is a commonly observed phenomenon near the dayside OCB [ Burch et al , 1990; Menietti and Smith , 1993; Menietti et al , 2007]. Electron beams of <1 keV on the dayside will not give rise to significant conductivity gradients and the shape of the magnetospheric E‐field discontinuity will be conserved when mapped down onto the ionosphere.…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

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On the relationship between thin Birkeland current arcs and reversed flow channels in the winter cusp/cleft ionosphere

et al. 2008

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[1] In this paper we study reversed flow events (RFEs) that seem regulated by Birkeland current arcs in the winter cusp ionosphere above Svalbard. An RFE is a longitudinally elongated, 100-200 km wide channel, in which the flow direction is opposite to the background convection, persisting for 10-20 min. The RFE onset occurs with the brightening of a discrete arc near the open-closed boundary. The auroral arc is situated exactly at a sharp clockwise flow reversal, consistent with a converging electric field and an upward field-aligned current. One category of RFEs propagates into the polar cap in tandem with poleward moving auroral forms, while another category of RFEs moves with the cusp/cleft boundary. The RFE phenomenon is addressed to a region void of electron precipitation, and in lack of direct sunlight the E-region conductivity will be very low. We propose two possible explanations: (1) the RFE channel may be a region where two MI current loops, forced by independent voltage generators, couple through a poorly conducting ionosphere and (2) the reversed flow channel may be the ionospheric footprint of an inverted V-type coupling region. Electron beams of <1 keV will not give rise to significant conductivity gradients, and the form of a discontinuity in the magnetospheric electric field will be conserved when mapped down to the ionosphere, although reduced in amplitude. These two explanations may be related in the sense that the boundary discontinuity in the magnetospheric electric field in (1) may be the driver for the inverted V in (2).

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Section: Discussionmentioning

confidence: 94%

Section: Summary and Concluding Remarksmentioning

confidence: 99%

On the relationship between thin Birkeland current arcs and reversed flow channels in the winter cusp/cleft ionosphere

et al. 2008

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“…: SEARCHING FOR ULF SIGNATURES OF THE CUSP however, that such discrete green line activity embedded within bright red auroral activity is typical of cusp/cleft auroral emissions. Except for the ''midday gap'' of about 2 h around noon [Dandekar and Pike, 1978], cusp/cleft auroras are known to have discrete components [Sandholt et al, 1990;Burch et al, 1990;Menietti and Smith, 1993;Menietti et al, 2007;Moen et al, 2008]. 0 -5 Hz spectrograms of search coil magnetometer data for this day (not shown) revealed similar activity between 1 and 5 Hz: they showed weak higher-frequency tails of the broadband [17] This day was typical of all 6 days listed in Table 2, in that no increase in broadband ULF wave power could be associated with the presence of increased soft electron precipitation characteristic of the cusp.…”

Section: A06217mentioning

confidence: 99%

Searching for ULF signatures of the cusp: Observations from search coil magnetometers and auroral imagers in Svalbard

et al. 2009

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[1] Spacecraft traveling through the cusp at a variety of altitudes have consistently found the cusp to be filled with intense, often irregular power in the upper ULF frequency range. Some ground-based studies have observed narrowband waves in this same frequency range in the vicinity of the cusp foot point, but it has not been possible with magnetometers alone to either confirm or deny a cusp source for these waves. We report here on the first simultaneous, collocated observations of a set of induction magnetometers installed at three near-cusp sites on Svalbard and an all-sky auroral imager located at Longyearbyen. Data during northern winters of 2006-2007 and 2007-2008, when the cusp foot point was in darkness, showed occasional broadband noise when energetic particle precipitation occurred overhead, but on most days no broadband ULF power was observed above the noise level near noon when only soft cusp precipitation or poleward moving auroral forms occurred overhead. However, on 3 days, including 15 January 2007, several bursts of band-limited Pc 1-2 waves were observed in association with regions of intense soft precipitation that peaked near the poleward edge of the cusp. Their properties are consistent with an origin in the plasma mantle, as observed in a recent satellite-ground study by Engebretson et al. (2005). These observations confirm that even intense cusp precipitation is not effective in generating ion cyclotron waves that penetrate to the ground, if it is embedded within the central regions of the cusp, whereas regions of enhanced precipitation at the poleward edge of the cusp are associated with observed waves.

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