Steep plasma depletion in dayside polar cap during a CME‐driven magnetic storm

Sakai, Jun; Taguchi, S.; Hosokawa, K.; Ogawa, Y.

doi:10.1029/2012ja018138

Cited by 5 publications

(4 citation statements)

References 30 publications

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“…More recently, Sakai et al . [] demonstrated, by using data from the EISCAT Svalbard radar, that similar large‐scale blobs of high‐density solar EUV plasma were produced in close association with switchings of the IMF B y .…”

Section: Discussion and Summarymentioning

confidence: 99%

Periodicities of polar cap patches

et al. 2013

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[1] A highly sensitive all-sky electron multiplier charge-coupled device airglow imager has been operative in Longyearbyen, Norway since October 2011. The imager captures 630.0 nm all-sky images with an exposure time of 4 s, which is about 10 times shorter than that achieved by conventional cooled CCD imagers. This allows us to visualize the structure of polar cap patches without blurring effects and better estimate their periodicities. We present, as one of the first results from the imager, an event of successive appearance of patches on the night of 21 December 2011. A time series of the optical intensity at zenith showed modulations having two distinguished periods, one at 40 min and the other at 5-12 min. One possible explanation is that such a coexistence of two different periodicities is a manifestation of simultaneous occurrence of patch generation processes on the 40 min periodicity was created by large-scale reconfiguration of the dayside convection pattern while the 5-12 min modulations were closely associated with mechanisms driven by pulsed reconnection on the dayside magnetopause. Such a combined effect of multiple patch generation processes may play a role in structuring patches; thus, it would be of particular importance for evaluating the space weather effects in the trans-ionospheric communications environment in the polar cap.

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Section: Discussion and Summarymentioning

confidence: 99%

Periodicities of polar cap patches

et al. 2013

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“…For example, one of the widely accepted mechanisms is that the sudden changes in east‐west component of the interplanetary magnetic field (interplanetary magnetic field B y ) controls the entry of high‐density plasma into the polar cap from lower latitude regions. Recently, Sakai et al [] showed a clear observational evidence for the above mechanism and showed that a sudden change of B y from positive to negative may result in a steep decrease in the local electron density observed by the EISCAT (European Incoherent Scatter) Svalbard Radar.…”

Section: Introductionmentioning

confidence: 99%

Storm time enhancements of 630.0 nm airglow associated with polar cap patches

et al. 2014

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We examined the brightness of 630.0 nm airglow, I630, associated with polar cap patches observed during a magnetic storm that occurred on 22 January 2012. Brightness was measured using an all‐sky imager (ASI) located at Longyearbyen, Svalbard. The observed I630 was compared with the F region electron density observed by the European Incoherent Scatter Svalbard Radar (ESR). The I630 was positively correlated with the F2 layer peak electron density, NmF2, and inversely correlated with the altitude of the F2layer peak electron density, hmF2, as expected from the known relationship between these parameters. To estimate the altitude of the peak emission of the airglow, we performed model calculations of the volume emission rate, V630, under quiet and disturbed conditions, using Mass Spectrometer Incoherent Scatter modeled neutral gas profiles and the electron density profile obtained from the ESR data. In order to validate the V630 calculation, I630 was calculated by integrating the V630 along altitude and then compared with the ASI‐observed I630. During the observation periods the measured brightness frequently exceeded the calculated I630; we infer that in most cases, low‐energy particle precipitation is responsible for the extra brightness. However, when there was less particle precipitation, the observed values were in good agreement with the calculated values. Under the magnetically disturbed conditions during our observations, the model calculation showed that the altitude of V630 peak increases, the thickness of the emission layer increases, and patch brightness increases.

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“…Zhang et al [2011] demonstrated that patch formation may be sensitive to IMF |B y |. It has been demonstrated that variability in the IMF B y strength can regulate patch structuring [e.g., Zhang et al, 2011;Sakai et al, 2013]. Oksavik et al [2010] traced a polar cap patch back to its probable entry region in the dusk cell during IMF B y positive condition.…”

Section: Introductionmentioning

confidence: 99%

On the symmetry of ionospheric polar cap patch exits around magnetic midnight

et al. 2015

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In this paper we examine how polar cap patches, which have been frozen into the antisolar flow over the polar cap, are transported into the nighttime auroral oval. First we present a detailed case study from 12 January 2002, with continuous observations of polar cap patches exiting into the nighttime auroral oval in the Scandinavian sector. Satellite images of the auroral oval and all-sky camera observations of 630.0 nm airglow patches are superimposed onto Super Dual Auroral Radar Network convection maps. These composite plots reveal that polar cap patches exit on both the dusk and on the dawn convection cells. Then we present statistics based on 8 years of data from the meridian scanning photometer at Ny-Aalesund, Svalbard, to investigate the possible interplanetary magnetic field (IMF) B y influence on the distribution of patch exits around magnetic midnight. The magnetic local time distribution of patch exits is almost symmetric around magnetic midnight, independent of IMF B y polarity. Synthesizing these observations with previous results, we propose a three-step mechanism for why patch material exits symmetrically around midnight. First, intake of patch material occurs on both convection cells for both IMF B y polarities. Second, plasma intake by transient magnetopause reconnection stretches the newly cut polar cap patches into dawn-dusk elongated forms during their transport into the polar cap. And finally at exit, dawn-dusk elongated patches are split and diverted toward both the dawn and dusk flanks when grabbed by transient tail reconnection.

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Steep plasma depletion in dayside polar cap during a CME‐driven magnetic storm

Cited by 5 publications

References 30 publications

Periodicities of polar cap patches

Periodicities of polar cap patches

Storm time enhancements of 630.0 nm airglow associated with polar cap patches

On the symmetry of ionospheric polar cap patch exits around magnetic midnight

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