Synoptic distribution of dayside aurora: Multiple-wavelength all-sky observation at Yellow River Station in Ny-Ålesund, Svalbard

Hu, Zejun; Yang, Huigen; Huang, De‐Hong; Araki, Tohru; Sato, Natsuo; Taguchi, Makoto; Seran, Elena; Hu, Hongqiao; Liu, R.; Zhang, B.; Han, Desheng; Chen, Z.; Zhang, Q.; Liang, Jimin; Liu, S.

doi:10.1016/j.jastp.2009.02.010

Cited by 83 publications

(122 citation statements)

References 47 publications

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“…A recent auroral precipitation study by Newell et al (2009), developed using 11 years of particle data from the DMSP series satellites, also showed that the diffuse aurora is more intense post-midnight and into the morning hours and often relatively insignificant from post-noon through dusk, owing to the predominant eastward transport of electrons as a result of a combination of E × B and gradient drifting from the nightside plasma sheet. In contrast, Hu et al (2009Hu et al ( , 2012, using the ground-based all-sky imager (ASI) measurements at the Chinese Yellow River Station in Ny-Ålesund, Svalbard, surveyed the synoptic distribution of dayside aurora emissions and their potential correlation with the interplanetary magnetic field (IMF), indicating a pre-noon (07:30-09:30 MLT) "warm spot" characterized uniquely by an increase of 557.7 nm emissions, which is contributed by the emissions of the discrete and diffuse aurora, and a midday (09:30-13:00 MLT) gap of relatively weak green line emissions for the discrete and diffuse aurora. Miyoshi et al (2010) proposed a model for the energy dispersion of electron precipitation associated with pulsating auroras; the dynamic structure embedded the diffuse aurora, and conducted a time-of-flight (TOF) analysis of precipitating electrons observed by the REIMEI satellite which suggested that the modulation region of wave-induced pitch angle scattering is near the magnetic equator.…”

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confidence: 90%

Intensification of dayside diffuse auroral precipitation: contribution of dayside Whistler-mode chorus waves in realistic magnetic fields

Shi

Han

et al. 2012

Ann. Geophys.

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Abstract. Compared to the recently improved understanding of nightside diffuse aurora, the mechanism(s) responsible for dayside diffuse aurora remains poorly understood. While dayside chorus has been thought as a potential major contributor to dayside diffuse auroral precipitation, quantitative analyses of the role of chorus wave scattering have not been carefully performed. In this study we investigate a dayside diffuse auroral intensification event observed by the Chinese Arctic Yellow River Station (YRS) all-sky imagers (ASI) on 7 January 2005 and capture a substantial increase in diffuse auroral intensity at the 557.7 nm wavelength that occurred over almost the entire ASI field-of-view near 09:24 UT, i.e., ∼12:24 MLT. Computation of bounceaveraged resonant scattering rates by dayside chorus emissions using realistic magnetic field models demonstrates that dayside chorus scattering can produce intense precipitation losses of plasma sheet electrons on timescales of hours (even approaching the strong diffusion limit) over a broad range of both energy and pitch angle, specifically, from ∼1 keV to 50 keV with equatorial pitch angles from the loss cone to up to ∼85 • depending on electron energy. Subsequent estimate of loss cone filling index indicates that the loss cone can be substantially filled, due to dayside chorus driven pitch angle scattering, at a rate of ≥0.8 for electrons from ∼500 eV to 50 keV that exactly covers the precipitating electrons for the excitation of green-line diffuse aurora. Estimate of electron precipitation flux at different energy levels, based on loss cone filling index profile and typical dayside electron distribution observed by THEMIS spacecraft under similar conditions, gives a total precipitation electron energy flux of the order of 0.1 erg cm −2 s −1 with ∼1 keV characteristic energy (especially when using T01s), which can be very likely to cause intense green-line diffuse aurora activity on the dayside. Therefore, dayside chorus scattering in the realistic magnetic field can greatly contribute to the YRS ASI observed intensification of dayside green-line aurora. Besides wave induced scattering and changes in the ambient magnetic field, variations in associated electron flux can also contribute to enhanced diffuse aurora emissions, the possibility of which we cannot exactly rule out due to lack of simultaneous observations of magnetospheric particles. Since the geomagnetic activity level was rather low during the period of interest, it is reasonable to infer that changes in the associated electron flux in the magnetosphere should be small, and consequently its contribution to the observed enhanced diffuse auroral activity should be small as well. Our results support the scenario that dayside chorus could play a major role in the production of dayside diffuse aurora, and also demonstrate that changes in magnetospheric magnetic field should be considered to reasonably interpret observations of dayside diffuse aurora.

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confidence: 90%

Intensification of dayside diffuse auroral precipitation: contribution of dayside Whistler-mode chorus waves in realistic magnetic fields

Shi

Han

et al. 2012

Ann. Geophys.

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“…In the proposed approach, an approximate inference algorithm based on variational approximation [16] is used to estimate Equation (5). By dropping the nodes w and the edges between θ and z, and adding the variational parameters γ and ϕ , a family of variational distribution (as shown in Figure 6), which is then utilized to approximate the likelihood function, can be obtained.…”

Section: The Likelihood Function Of the I-th Aurora Image Is Written mentioning

confidence: 99%

“…In 2000, the Polar Research Institute of China (PRIC) divided auroras into arc auroras and corona auroras. In addition, the corona auroras were subdivided into radiation corona auroras, hot-spot corona auroras, and drapery corona auroras [5], as shown in Figure 2. Aurora classification has important research significance, and it has attracted the interest of researchers in the field of computer vision.…”

Section: Introductionmentioning

confidence: 99%

Aurora Image Classification Based on Multi-Feature Latent Dirichlet Allocation

et al. 2018

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Due to the rich physical meaning of aurora morphology, the classification of aurora images is an important task for polar scientific expeditions. However, the traditional classification methods do not make full use of the different features of aurora images, and the dimension of the description features is usually so high that it reduces the efficiency. In this paper, through combining multiple features extracted from aurora images, an aurora image classification method based on multi-feature latent Dirichlet allocation (AI-MFLDA) is proposed. Different types of features, whether local or global, discrete or continuous, can be integrated after being transformed to one-dimensional (1-D) histograms, and the dimension of the description features can be reduced due to using only a few topics to represent the aurora images. In the experiments, according to the classification system provided by the Polar Research Institute of China, a four-class aurora image dataset was tested and three types of features (MeanStd, scale-invariant feature transform (SIFT), and shape-based invariant texture index (SITI)) were utilized. The experimental results showed that, compared to the traditional methods, the proposed AI-MFLDA is able to achieve a better performance with 98.2% average classification accuracy while maintaining a low feature dimension.

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“…CYRS, Svalbard has installed an optical observation system in November 2003 (Liu et al, 2005;Hu et al, 2009), which consists of three all-sky cameras (ASI) supplied with the narrow-band filters centered at 427.8, 557.7, and 630.0 nm. We are only using the observations from 557.7 and 630.0 nm cameras in this paper.…”

Section: All Sky Imager (Asi) Datamentioning

confidence: 99%

“…The station location makes it possible to observe longer time aurora during winter nights of the arctic regions. More details about this optical system are available in Liu et al (2005) and Hu et al (2009). We also present the keograms extracted along the meridian line from the ASI data for showing the time-series appearance of auroral emissions.…”

Section: All Sky Imager (Asi) Datamentioning

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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Synoptic distribution of dayside aurora: Multiple-wavelength all-sky observation at Yellow River Station in Ny-Ålesund, Svalbard

Cited by 83 publications

References 47 publications

Intensification of dayside diffuse auroral precipitation: contribution of dayside Whistler-mode chorus waves in realistic magnetic fields

Intensification of dayside diffuse auroral precipitation: contribution of dayside Whistler-mode chorus waves in realistic magnetic fields

Aurora Image Classification Based on Multi-Feature Latent Dirichlet Allocation

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

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