Horizontal profile of a moving red line cusp aurora

Taguchi, S.; Chiba, Y.; Hosokawa, K.; Ogawa, Y.

doi:10.1002/2016ja023115

Cited by 4 publications

(3 citation statements)

References 34 publications

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“…The low temperature regions poleward and equatorward of the auroral oval are the polar cap and the closed magnetic field line region. The cusp can be identified as the region of enhanced F‐region electron temperature (>3000 K, Figure 3c) and density (>3 × 10 11 m −3 , Figure 3b) (Taguchi et al., 2017; Watermann et al., 1994) at 79°–82° MLAT at 18:20‐19:40 UT. The poleward velocity was enhanced all across the RISR FOV, peaking near 80° MLAT.…”

Section: Resultsmentioning

confidence: 99%

Cusp Dynamics and Polar Cap Patch Formation Associated With a Small IMF Southward Turning

et al. 2021

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The cusp is one of the most dynamic regions in the polar ionosphere. The cusp is located near noon just poleward of the open and closed magnetic field lines of the dayside magnetosphere-ionosphere system, and a variety of energy input processes from the magnetosheath and magnetopause characterize the cusp. Precipitation in the cusp is dominated by soft electrons and energetic protons, and impact ionization and precipitation heating primarily occur in the F-region ionosphere and thermosphere (Hardy et al., 1985;Skjaeveland et al., 2017). The cusp is located at the dayside convection throat, where fast flows transport plasma from closed to open field lines (Moen et al., 2001;Sandholt et al., 2003) and increases Joule heating (Shi et al., 2017). The heating in the cusp increases plasma upflows and thermospheric density (Carlson et al., 2012;Ogawa et al., 2009). In addition to the large-scale quasi-steady convection, pulsed flows propagate poleward in association with localized field-aligned currents. The footprint of the upward FACs is illuminated as discrete auroral arcs, and it is referred to as poleward moving auroral forms (PMAFs) (Oksavik et al., 2004). This transient system is characterized as a flow channel and a wedge-like current system.An important consequence of the cusp dynamics is formation of polar cap patches. During a large southward IMF, the open-closed boundary moves equatorward and photoionized plasma from the sunlit ionosphere becomes an important source of polar cap patches (

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Section: Resultsmentioning

confidence: 99%

Cusp Dynamics and Polar Cap Patch Formation Associated With a Small IMF Southward Turning

et al. 2021

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“…Poleward‐moving auroral forms (PMAFs) are frequently observed as mesoscale transient auroras in the dayside sector near magnetic noon, usually forming rayed bands in the dayside auroral oval and then separating from the oval following by drifting into the polar cap (Fasel et al, 1994; Frey et al, 2019). PMAFs' spatial size varies between 50 and 500 km in longitude and is about 50 km in latitude with a lifetime of usually less than 10 min (Fasel et al, 1992; Sandholt et al, 1990; Taguchi et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Observations of Poleward‐Moving Auroral Forms at the Equatorward and Poleward Boundaries of the Auroral Oval in Antarctica

Mende

Frey

2020

JGR Space Physics

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Poleward-moving auroral form (PMAF) is a type of dayside auroral pattern. The distinguishing characteristic of a PMAF is its separation from the auroral oval and subsequent poleward motion. It has been reported and widely accepted that PMAFs occur more frequently during periods with dominant southward interplanetary magnetic field (IMF). However, most ground-based optical observations were made near magnetic latitudes of 75 • , close to the equatorward boundary of the dayside auroral oval; therefore, PMAFs occurring at the poleward boundary were likely missed easily. Using all-sky images from two stations located on the similar magnetic meridian in Antarctica at 80 • and 75 • magnetic latitude, and taking solar wind data close to the magnetosphere by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft, we demonstrate that unlike the result from prior low-latitude single-station observations, the combined observations from both stations show an insignificant difference in the PMAF occurrence rate in the northward and southward IMF conditions and no clear sign suggesting that the southward IMF or southward turning of the IMF triggers PMAFs. With good agreements between PMAF occurrence rate and the intensity of the poleward drift, we suggest that PMAFs are more likely to be plasma patches torn away from the dayside auroral oval convecting antisunward and rather than direct foot points of reconnecting flux tubes.

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“…We examine the relationship between auroral structures and plasma flow through simultaneous observations from an all-sky imager and the European Incoherent Scatter (EISCAT) Svalbard radar (ESR). The ESR has been used in many previous studies to understand the relationships between dayside auroras and plasma flow (e.g., Lockwood et al, 2000;Moen et al, 2008;Oksavik et al, 2004;Skjaeveland et al, 2017;Taguchi et al, 2015bTaguchi et al, , 2017. To our knowledge, this is the first work to focus on discrete auroral structures equatorward of the cusp, where diffuse auroras are usually seen, using simultaneous observations obtained by an all-sky imager and the ESR.…”

Section: Introductionmentioning

confidence: 99%

Plasma Flow in the North‐South Aligned Discrete Aurora Equatorward of the Cusp

2019

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On the equatorward side of the dayside cusp there often appear diffuse auroras. In this paper, we report north-south aligned discrete aurora events and show the spatial relationships between the auroras and the plasma flow. Several events of the north-south aligned discrete auroral structures were identified using an all-sky imager at Longyearbyen, Svalbard, during the recovery of a moderately disturbed period on 8 December 2013. During a brief interval of the moderately disturbed period, the cusp shifted to higher latitudes; as a result, the field-aligned beam of the EISCAT Svalbard Radar (ESR) passed through the northern portion of the north-south aligned auroral structures. Simultaneous observations from the all-sky imager and ESR reveal that enhancements in ion temperature (caused by fast ion flow) occurred near the eastward and westward boundaries of the north-south aligned auroral structures. However, within the region of the most enhanced aurora, the ion temperature enhancements were moderately suppressed. These features indicate that the ion flow slows down in the region of electron precipitation responsible for north-south aligned auroral structures. We can quantitatively interpret the slowdown of the flow as the reduction of the electric field due to the polarization effect in the north-south aligned region of the increased Pedersen conductivity. It thus appears that the magnetospheric source of the north-south aligned discrete auroras is a limited area embedded in the region of plasma flow toward the dayside magnetopause.

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Horizontal profile of a moving red line cusp aurora

Cited by 4 publications

References 34 publications

Cusp Dynamics and Polar Cap Patch Formation Associated With a Small IMF Southward Turning

Cusp Dynamics and Polar Cap Patch Formation Associated With a Small IMF Southward Turning

Simultaneous Observations of Poleward‐Moving Auroral Forms at the Equatorward and Poleward Boundaries of the Auroral Oval in Antarctica

Plasma Flow in the North‐South Aligned Discrete Aurora Equatorward of the Cusp

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