Auroral fragmentation into patches

Shiokawa, K.; Hashimoto, Ayumi; Hori, Tomoaki; Sakaguchi, Kaori; Ogawa, Y.; Donovan, E.; Spanswick, E.; Connors, Martin; Otsuka, Yuichi; Oyama, Shin‐ichiro; Nozawa, Satonori; McWilliams, K. A.

doi:10.1002/2014ja020050

Cited by 19 publications

(37 citation statements)

References 31 publications

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“…This may be associated with the movement of the fragmented aurora due to the flow burst. We found a good consistency between the poleward growth of the fragmented aurora (Shiokawa et al, 2014) and IL/IU ionospheric current during the FBAE near ∼23:15 UT during the substorm (please see discussion of Figure 1). However, during the BBAE we witnessed a disturbed geomagnetic condition and the continuous existence of large scale and dynamic auroral structures.…”

Section: Bouncing Boundary Auroral Emissions (Bbae)supporting

confidence: 59%

“…There is a possibility that the fragmented poleward moving auroral structures may be associated with the flow burst (Zou et al, 2009), which causes significant enhancement in the phase scintillation. The small scale aurora, which is not extended in latitudinal direction and it can be in various small shape with persistent geometry, is known as fragmented aurora (Shiokawa et al, 2014).…”

Section: Fixed Boundary Auroral Emissions (Fbae)mentioning

confidence: 99%

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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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Section: Bouncing Boundary Auroral Emissions (Bbae)supporting

confidence: 59%

Section: Fixed Boundary Auroral Emissions (Fbae)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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“…The coexistence and rough colocation of 630 nm and 557.7 nm auroral patches, with the former weaker in intensity than the latter, were also noticed in Shiokawa et al . [].…”

Section: Observationsmentioning

confidence: 99%

“…Shiokawa et al . [] reported the simultaneous observations of diffuse auroral patches at 557.7 nm and 630 nm; despite the low time resolution of their camera (12 s cadence), they were still able to show that the 630 nm auroral patches are essentially collocated with the 557.7 nm patches.…”

Section: Introductionmentioning

confidence: 99%

On the 630 nm red‐line pulsating aurora: Red‐line Emission Geospace Observatory observations and model simulations

et al. 2016

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In this study, we present observations of red‐line (630 nm) pulsating auroras using the camera system of Red‐line Emission Geospace Observatory (REGO), during a geomagnetic storm interval. We also develop a time‐dependent model to simulate the 630 nm auroral pulsations in response to modulated precipitation inputs and compare the model outputs with REGO observations. Key results are as follows. (1) Notwithstanding the long radiative timescale of the 630 nm emission, red‐line auroras can still be modulated by pulsating electron precipitations and feature noticeable oscillations, which constitute the red‐line pulsating auroral phenomena. (2) In a majority of cases, the oscillation magnitude of red‐line pulsating auroras is substantially smaller than that of the concurrent pulsating auroras seen on Thermal Emission Imaging System whitelight images (generally dominated by 557.7 nm green‐line emissions). Under certain circumstances, e.g., when the characteristic energy of the precipitation is very high, some of the pulsating auroras may not show discernible imprints on red line. (3) The altitude range contributing most to the red‐line pulsating aurora is systematically lower than that of the steady‐state red‐line aurora, since the slower O(1D) loss rate at higher altitudes tends to suppress the oscillation range of the 630 nm emission rate. (4) We find that some pulsating auroral patches are characterized by enhanced red‐to‐green color ratio during their on time, hinting that the percentage increase of the red‐line auroral component exceeds that of the green‐line auroral component for those patches. We suggest that those special patches might possibly be associated with lower energy (<1 keV) electron precipitations.

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“…Considerable progress also has been made in understanding the auroral patches in the diffuse aurora. The main driver of the auroral fragmentation has been identified as an instability that affects the balance between the earthward magnetictension force and the tailward pressure gradient force in the magnetosphere (Shiokawa et al 2014). …”

Section: Tg3: Effects Of Short-term Solar Variability On the Geospmentioning

confidence: 99%

Advancing the understanding of the Sun–Earth interaction—the Climate and Weather of the Sun–Earth System (CAWSES) II program

Tsuda

Shepherd

Gopalswamy

2015

Prog. in Earth and Planet. Sci.

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The Scientific Committee on Solar-Terrestrial Physics (SCOSTEP) of the International Council for Science (ICSU) implemented an international collaborative program called Climate and Weather of the Sun-Earth System (CAWSES), which was active from 2004 to 2008; this was followed by the CAWSES II program during the period of 2009-2013. The CAWSES program was aimed at improving the understanding of the coupled solar-terrestrial system, with special emphasis placed on the short-term (weather) and long-term (climate) variability of solar activities and their effects on and responses of Geospace and Earth's environment. Following the successful implementation of CAWSES, the CAWSES II program pursued four fundamental questions addressing the way in which the coupled Sun-Earth system operates over time scales ranging from minutes to millennia, namely, (1) What are the solar influences on the Earth' s climate? (2) How will Geospace respond to an altered climate? (3) How does short-term solar variability affect the Geospace environment? and (4) What is the Geospace response to variable inputs from the lower atmosphere? In addition to these four major tasks, the SCOSTEP and CAWSES promoted E-science and informatics activities including the creation of scientific databases and their effective utilization in solar-terrestrial physics research. Capacity building activities were also enhanced during CAWSES II, and this represented an important contribution of SCOSTEP to the world's solar-terrestrial physics community. This introductory paper provides an overview of CAWSES II activities and serves as a preface to the dedicated review papers summarizing the achievements of the program's four task groups (TGs) and the E-science component.

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Auroral fragmentation into patches

Cited by 19 publications

References 31 publications

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

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

On the 630 nm red‐line pulsating aurora: Red‐line Emission Geospace Observatory observations and model simulations

Advancing the understanding of the Sun–Earth interaction—the Climate and Weather of the Sun–Earth System (CAWSES) II program

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