Modulation of the dayside diffuse auroral intensity by the solar wind dynamic pressure

Shi, Rong; Hu, Zejun; Ni, Binbin; Han, Desheng; Chen, X.; Zhou, Chen; Gu, Xudong

doi:10.1002/2014ja020180

Cited by 9 publications

(13 citation statements)

References 15 publications

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“…We therefore suggest that the unstructured DDAs observed in the morning are extension of the nightside diffuse aurora to the morning and are caused by scattering the plasma sheet electrons into loss cone by whistler-mode chorus waves, which are modulated both by compressional Pc 4-5 waves [Li et al, 2011a] and density variations [Li et al, 2011b] and are commonly observed in the dawn flank of the magnetosphere [Li et al, 2009]. Some recent studies found sudden increase of solar wind dynamic pressure can lead to enhancement of the unstructured DDAs [Shi et al, 2015;Liu et al, 2015]. This may presents indirect evidence for our suggestion because the compressional waves can modulate the chorus waves [Li et al, 2011b], and increase of solar wind dynamic pressure can certainly generate compressional waves in the magnetosphere [e.g., Han et al, 2007].…”

Section: Unstructured Ddas In the Morningmentioning

confidence: 83%

An extensive survey of dayside diffuse aurora based on optical observations at Yellow River Station

et al. 2015

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By using 7 years optical auroral observations obtained at Yellow River Station (magnetic latitude 76.24°N) at Ny-Alesund, Svalbard, we performed the first extensive survey for the dayside diffuse auroras (DDAs) and acquired observational results as follows.(1) The DDAs can be classified into two broad categories, i.e., unstructured and structured DDAs. The unstructured DDAs are mainly distributed in morning and afternoon, but the structured DDAs predominantly occurred around the magnetic local noon (MLN). (2) The unstructured DDAs observed in morning and afternoon present obviously different properties. The afternoon ones are much stable and seldom show pulsating property. (3) The DDAs are more easily observed under geomagnetically quiet times. (4) The structured DDAs mainly show patchy, stripy, and irregular forms and are often pulsating and drifting. The drifting directions are mostly westward (with speed ~5 km/s), but there are cases showing eastward or poleward drifting. ( 5) The stripy DDAs are exclusively observed near the MLN and, most importantly, their alignments are confirmed to be consistent with the direction of ionospheric convection near the MLN. (6) A new auroral form, called throat aurora, is found to be developed from the stripy DDAs. Based on the observational results and previous studies, we proposed our explanations to the DDAs. We suggest that the unstructured DDAs observed in the morning are extensions of the nightside diffuse aurora to the dayside, but that observed in the afternoon are predominantly caused by proton precipitations. The structured DDAs occurred near the MLN are caused by interactions of cold plasma structures, which are supposed to be originated from the ionospheric outflows or plasmaspheric drainage plumes, with hot electrons from the plasma sheet. We suppose that the cold plasma structures for producing the patchy DDAs are in lumpy and are more likely from the plasmaspheric drainage plumes. The cold plasma structure for producing the stripy DDAs should be in wedge like and is generated by conveying the cold plasmas from lower L-shell toward higher L-shell with magnetospheric convection, and that for producing the irregular DDAs is resulted from deforming the wedge-like structure by disturbance. The throat aurora is supposed to be projection of a newly opened flux of reconnection. In addition, we also found that structured DDAs correspond to structured electron precipitations in the ionosphere, which implies that the cold plasma structures in the magnetosphere are magnetically mapped to the ionosphere and act as a duct for producing the structured DDAs. We argue that we have presented some new observational results about DDA in this paper, which will be useful for fully understanding the DDAs.

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Section: Unstructured Ddas In the Morningmentioning

confidence: 83%

An extensive survey of dayside diffuse aurora based on optical observations at Yellow River Station

et al. 2015

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“…Previous studies have suggested that whistler‐mode chorus waves also contribute to the production of dayside diffuse aurora (Ni et al., 2014; Nishimura et al., 2013; Shi et al., 2012, 2014). Chorus wave induced electron precipitation is found to be strongest from the nightside to dawn sectors over 4 < L < 6.5 (Ma et al., 2020).…”

Section: Summary and Discussionmentioning

confidence: 99%

Diffuse Auroral Electron Scattering by Electrostatic Electron Cyclotron Harmonic Waves in the Dayside Magnetosphere

Lou

Cao

et al. 2021

Geophysical Research Letters

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Although electrostatic electron cyclotron harmonic (ECH) waves are frequently observed in the dayside magnetosphere, their effects on the formation of dayside diffuse aurora remain poorly understood. In this study, we quantitatively evaluate the efficiency of dayside ECH wave scattering in producing the electron diffuse aurora precipitation during a typical ECH wave event by calculating the quasi‐linear bounce‐averaged scattering rates. We find that dayside ECH waves can efficiently pitch angle scatter diffuse auroral electrons on timescales of a few hours to ∼1 day over a broad range of electron energy and equatorial pitch angle α eq, that is, from ∼300 eV to 10 keV with α eq from the loss cone to 45°. Especially for ∼300 eV–2 keV electrons, the scattering rates can even approach the strong diffusion limit, resulting in an almost fully filled loss cone. Our results confirm the significant role of ECH waves in driving the dayside diffuse aurora.

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“…During the purely dynamic pressure enhancement or the impact of interplanetary (IP) shocks (with high dynamic pressures and southward IMFs), global auroras can be brightened gradually from the dayside to the nightside (termed "compression auroras" or "shock auroras") (Du et al, 2011;Holmes et al, 2014;Liou et al, 2007;Meurant et al, 2004;Ni et al, 2016;Nomura et al, 2016;Peng et al, 2011;Shi et al, 2014;Tsurutani et al, 2001;Yang et al, 2011;Zhou & Tsurutani, 1999;Zhou et al, 2003;Zhang et al, 2008). The large disturbances in solar wind not only directly affect the magnetospheric plasma wave intensity and the auroral brightness but also cause geomagnetic storms or magnetospheric substorms.…”

Section: Introductionmentioning

confidence: 99%

The Effects of Solar Wind Dynamic Pressure Changes on the Substorm Auroras and Energetic Electron Injections on 24 August 2005

Wang

2018

JGR Space Physics

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After the passage of an interplanetary (IP) shock at 06:13 UT on 24 August 2005, the enhancement (>6 nPa) of solar wind dynamic pressure and the southward turning of interplanetary magnetic field (IMF) cause the earthward movement of dayside magnetopause and the drift loss of energetic particles near geosynchronous orbit. The persistent electron drift loss makes the geosynchronous satellites cannot observe the substorm electron injection phenomenon during the two substorm expansion phases (06:57–07:39 UT) on that day. Behind the IP shock, the fluctuations (~0.5–3 nPa) of solar wind dynamic pressure not only alter the dayside auroral brightness but also cause the entire auroral oval to swing in the day‐night direction. However, there is no Pi2 pulsation in the nightside auroral oval during the substorm growth phase from 06:13 to 06:57 UT. During the subsequent two substorm expansion phases, the substorm expansion activities cause the nightside aurora oval brightening from substorm onset site to higher latitudes, and meanwhile, the enhancement (decline) of solar wind dynamic pressure makes the nightside auroral oval move toward the magnetic equator (the magnetic pole). These observations demonstrate that solar wind dynamic pressure changes and substorm expansion activities can jointly control the luminosity and location of the nightside auroral oval when the internal and external disturbances occur simultaneously. During the impact of a strong IP shock, the earthward movement of dayside magnetopause probably causes the disappearance of the substorm electron injections near geosynchronous orbit.

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Modulation of the dayside diffuse auroral intensity by the solar wind dynamic pressure

Cited by 9 publications

References 15 publications

An extensive survey of dayside diffuse aurora based on optical observations at Yellow River Station

An extensive survey of dayside diffuse aurora based on optical observations at Yellow River Station

Diffuse Auroral Electron Scattering by Electrostatic Electron Cyclotron Harmonic Waves in the Dayside Magnetosphere

The Effects of Solar Wind Dynamic Pressure Changes on the Substorm Auroras and Energetic Electron Injections on 24 August 2005

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