Climatological characteristics of the auroral ionosphere in terms of electric field and ionospheric conductance

Ahn, B.‐H.; Emery, B. A.; Kroehl, H. W.; Kamide, Y.

doi:10.1029/1999ja900043

Cited by 27 publications

(29 citation statements)

References 34 publications

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“…In the following we label them "polar cap" (PC: MLAT > 70 • ), and "auroral zone" (AZ: 60 • ≤ MLAT ≤ 70 • ). Polar cap Hall currents are found to flow predominantly westward on the dawn side and eastward on the dusk side, meaning they are directed sunward on both sides (e.g., Ahn et al, 1999). In the auroral zone the auroral electrojets are located flowing anti-sunward both on the dawn and dusk sides, the inverse of polar cap Hall currents.…”

Section: Dependence Of Hall Currents On Season and Imfmentioning

confidence: 99%

Global characteristics of auroral Hall currents derived from the Swarm constellation: dependences on season and IMF orientation

Huang¹,

Lühr

Wang³

2017

Ann. Geophys.

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Abstract. On the basis of field-aligned currents (FACs) and Hall currents derived from high-resolution magnetic field data of the Swarm constellation, the average characteristics of these two current systems in the auroral regions are comprehensively investigated by statistical methods. This is the first study considering both current types determined simultaneously by the same spacecraft in both hemispheres. The FAC distribution, derived from the novel Swarm dualspacecraft approach, reveals the well-known features of Region 1 (R1) and Region 2 (R2) FACs. At high latitudes, Region 0 (R0) FACs appear on the dayside. Their flow direction, up or down, depends on the orientation of the interplanetary magnetic field (IMF) B y component. Of particular interest is the distribution of auroral Hall currents. The prominent auroral electrojets are found to be closely controlled by the solar wind input, but we find no dependence of their intensity on the IMF B y orientation. The eastward electrojet is about 1.5 times stronger in local summer than in winter. Conversely, the westward electrojet shows less dependence on season. As to higher latitudes, part of the electrojet current is closed over the polar cap. Here the seasonal variation of conductivity mainly controls the current density. During local summer of the Northern Hemisphere, there is a clear channeling of return currents over the polar cap. For positive (negative) IMF B y a dominant eastward (westward) Hall current circuit is formed from the afternoon (morning) electrojet towards the dawn side (dusk side) polar cap return current. The direction of polar cap Hall currents in the noon sector depends directly on the orientation of the IMF B y . This is true for both signs of the IMF B z component. Comparable Hall current distributions can be observed in the Southern Hemisphere but for opposite IMF B y signs. Around the midnight sector the westward substorm electrojet is dominating. As expected, it is highly dependent on magnetic activity, but it shows only little response to season and IMF B y polarity. An important finding is that all the IMF B y dependences of FACs and Hall currents practically disappear in the dark winter hemisphere.

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Section: Dependence Of Hall Currents On Season and Imfmentioning

confidence: 99%

Global characteristics of auroral Hall currents derived from the Swarm constellation: dependences on season and IMF orientation

Huang¹,

Lühr

Wang³

2017

Ann. Geophys.

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“…Since they came into operation in 1960s, incoherent scatter radars in the polar region have significantly contributed to our understanding of the polar ionosphere as well as the solar windmagnetosphere-ionosphere coupling (e.g., Brekke et al, 1974;Kamide and Brekke, 1975;Kamide and Vickrey, 1983;Araki et al, 1989;Peymirat and Fontaine, 1997;Thayer, 1998a, b;Fujii et al, 1999;Ahn et al, 1999;Sugino et al, 2002). Based on Chatanika radar measurements, Ahn et al (1999) examined the climatological characteristics of the auroral ionosphere in terms of the electric field and ionospheric conductivity.…”

Section: Introductionmentioning

confidence: 99%

“…Based on Chatanika radar measurements, Ahn et al (1999) examined the climatological characteristics of the auroral ionosphere in terms of the electric field and ionospheric conductivity. They reported that the Hall conductance distribution associated with the eastward electrojet in the post-noon sector is mainly determined by the Sun, while the major part of the westward electrojet in the midnight-post-midnight sector is closely associated with precipitating electrons.…”

Section: Introductionmentioning

confidence: 99%

Electrodynamical characteristics of the polar ionosphere over the auroral and polar cap regions based on incoherent scatter radar measurements

Kwak¹,

Ahn²,

Emery³

et al. 2006

Journal of Atmospheric and Solar-Terrestrial Physics

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“…It is clear from Figures 2A,B,G that during the poleward movement of the auroral structures, ionospheric current in the nightside auroral zone were high. Following Guo et al (2012), Kamide and Kokubun (1996), and Ahn et al (1999Ahn et al ( , 2000, the increased IU/IL is related with the enhanced electric field and Hall conductance, which is mostly associated with the enhanced auroral particle precipitation around the local midnight sector.…”

Section: Bouncing Boundary Auroral Emissions (Bbae)mentioning

confidence: 99%

The Behaviors of Ionospheric Scintillations Around Different Types of Nightside Auroral Boundaries Seen at the Chinese Yellow River Station, Svalbard

Priyadarshi

Zhang

et al. 2018

Front. Astron. Space Sci.

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Dynamical nightside auroral structures are often observed by the all sky imagers (ASI) at the Chinese Yellow River Station (CYRS) at Ny-Ålesund, Svalbard, located in the polar cap near poleward edge of the nightside auroral oval. The boundaries of the nightside auroral oval are stable during quiet geomagnetic conditions, while they often expand poleward and pass through the overhead area of CYRS during the substorm expansion phase. The motions of these boundaries often give rise to strong disturbances of satellite navigations and communications. Two cases of these auroral boundary motions have been introduced to investigate their associated ionospheric scintillations: one is Fixed Boundary Auroral Emissions (FBAE) with stable and fixed auroral boundaries, and another is Bouncing Boundary Auroral Emissions (BBAE) with dynamical and largely expanding auroral boundaries. Our observations show that the auroral boundaries, identified from the sharp gradient of the auroral emission intensity from the ASI images, were clearly associated with ionospheric scintillations observed by Global Navigation Satellite System (GNSS) scintillation receiver at the CYRS. However, amplitude scintillation (S 4 ) and phase scintillation (σ φ ) respond in an entirely different way in these two cases due to the different generation mechanism as well as different IMF (Interplanetary Magnetic Field) condition. S 4 and σ φ have similar levels around the FBAE, while σ φ was much stronger than S 4 around BBAE. The BBAE were associated with stronger particle precipitation during the substorm expansion phase. IU/IL, appeared to be a good indicator of the poleward moving auroral structures during the BBAE as well as FBAE.

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Climatological characteristics of the auroral ionosphere in terms of electric field and ionospheric conductance

Cited by 27 publications

References 34 publications

Global characteristics of auroral Hall currents derived from the Swarm constellation: dependences on season and IMF orientation

Global characteristics of auroral Hall currents derived from the Swarm constellation: dependences on season and IMF orientation

Electrodynamical characteristics of the polar ionosphere over the auroral and polar cap regions based on incoherent scatter radar measurements

The Behaviors of Ionospheric Scintillations Around Different Types of Nightside Auroral Boundaries Seen at the Chinese Yellow River Station, Svalbard

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