Search Results - "Dahlgren, H"

Dynamics of density cavities generated by frictional heating: Formation, distortion, and instability by Zettergren, M. D., Semeter, J. L., Dahlgren, H.

“…A simulation study of the generation and evolution of mesoscale density cavities in the polar ionosphere is conducted using a time‐dependent, nonlinear,…”
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Electrodynamics and energy characteristics of aurora at high resolution by optical methods by Dahlgren, H., Lanchester, B. S., Ivchenko, N., Whiter, D. K.

“…Technological advances leading to improved sensitivity of optical detectors have revealed that aurora contains a richness of dynamic and thin filamentary…”
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Coexisting structures from high- and low-energy precipitation in fine-scale aurora by Dahlgren, H., Lanchester, B. S., Ivchenko, N.

“…High‐resolution multimonochromatic measurements of auroral emissions have revealed the first optical evidence of coexisting small‐scale auroral features…”
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The optical manifestation of dispersive field-aligned bursts in auroral breakup arcs by Dahlgren, H., Semeter, J. L., Marshall, R. A., Zettergren, M.

“…High‐resolution optical observations of a substorm expansion show dynamic auroral rays with surges of luminosity traveling up the magnetic field lines…”
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Space-time variability of polar cap patches: Direct evidence for internal plasma structuring by Dahlgren, H., Perry, G. W., Semeter, J. L., St.-Maurice, J.-P., Hosokawa, K., Nicolls, M. J., Greffen, M., Shiokawa, K., Heinselman, C.

“…Coordinated observations of ionospheric variability near the geomagnetic pole using the Resolute Bay Incoherent Scatter Radar (RISR‐N), Super Dual Auroral…”
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Spatiotemporally resolved electrodynamic properties of a Sun-aligned arc over Resolute Bay by Perry, G. W., Dahlgren, H., Nicolls, M. J., Zettergren, M., St.-Maurice, J.-P., Semeter, J. L., Sundberg, T., Hosokawa, K., Shiokawa, K., Chen, S.

“…Common volume measurements by the Resolute Bay Incoherent Scatter Radar‐North (RISR‐N) and Optical Mesosphere and Thermosphere Imagers (OMTI) have been used to…”
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High-speed stereoscopy of aurora by Kataoka, R., Fukuda, Y., Uchida, H. A., Yamada, H., Miyoshi, Y., Ebihara, Y., Dahlgren, H., Hampton, D.

“…We performed 100 fps stereoscopic imaging of aurora for the first time. Two identical sCMOS cameras equipped with narrow field-of-view lenses (15° by 15°) were…”
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Monoenergetic high-energy electron precipitation in thin auroral filaments by Dahlgren, H., Ivchenko, N., Lanchester, B. S.

“…The energy distribution of the electron precipitation responsible for extremely narrow (70 m) and dynamic auroral filaments is found to be sharply peaked at…”
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Using multispectral optical observations to identify the acceleration mechanism responsible for flickering aurora by Whiter, D. K., Lanchester, B. S., Gustavsson, B., Ivchenko, N., Dahlgren, H.

“…We present an analysis of flickering (2–10 Hz) auroras observed with a state‐of‐the‐art multispectral imaging system, Auroral Structure and Kinetics, located…”
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Anomalous ISR echoes preceding auroral breakup: Evidence for strong Langmuir turbulence by Akbari, H., Semeter, J. L., Dahlgren, H., Diaz, M., Zettergren, M., Strømme, A., Nicolls, M. J., Heinselman, C.

“…Experimental results obtained with the 449‐MHz Poker Flat Incoherent Scatter Radar (PFISR) show unusual features in both the ion line and plasma line…”
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Structure and dynamics of the nightside poleward boundary: Sounding rocket and ground-based observations of auroral electron precipitation in a rayed curtain by Lynch, K. A., Hampton, D., Mella, M., Zhang, Binzheng, Dahlgren, H., Disbrow, M., Kintner, P. M., Lessard, M., Lundberg, E., Stenbaek-Nielsen, H. C.

“…The Cascades2 auroral sounding rocket provides a case study for comparing multipoint in situ ionospheric observations of a nightside auroral poleward boundary…”
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Auroral ion acoustic wave enhancement observed with a radar interferometer system by Schlatter, N. M., Belyey, V., Gustavsson, B., Ivchenko, N., Whiter, D., Dahlgren, H., Tuttle, S., Grydeland, T.

“…Measurements of naturally enhanced ion acoustic line (NEIAL) echoes obtained with a five-antenna interferometric imaging radar system are presented. The…”
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Energy and flux variations across thin auroral arcs by DAHLGREN, H, GUSTAVSSON, B, LANCHESTER, B. S, IVCHENKO, N, BRÄNDSTRÖM, U, WHITER, D. K, SERGIENKO, T, SANDAHL, I, MARKLUND, G

“…Two discrete auroral arc filaments, with widths of less than 1 km, have been analysed using multi-station, multi-monochromatic optical observations from small…”
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Direct three-dimensional imaging of polar ionospheric structures with the Resolute Bay Incoherent Scatter Radar by Dahlgren, H., Semeter, J. L., Hosokawa, K., Nicolls, M. J., Butler, T. W., Johnsen, M. G., Shiokawa, K., Heinselman, C.

“…Ionospheric plasma density structures in the dayside F‐region of the polar cap are commonly occurring events, but adequate measurements of their formation and…”
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Morphology and dynamics of aurora at fine scale : first results from the ASK instrument by DAHLGREN, H, IVCHENKO, N, SULLIVAN, J, LANCHESTER, B. S, MARKLUND, G, WHITER, D

“…The ASK instrument (Auroral Structure and Kinetics) is a narrow field auroral imager, providing simultaneous images of aurora in three different spectral bands…”
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Small-scale structures in flickering aurora by Whiter, D. K., Lanchester, B. S., Gustavsson, B., Ivchenko, N., Sullivan, J. M., Dahlgren, H.

“…A state‐of‐the‐art multispectral imager has been used to study the flickering component of an auroral event at high spatial (40 m) and temporal (32 fps)…”
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Sounding rocket study of two sequential auroral poleward boundary intensifications by Mella, M. R., Lynch, K. A., Hampton, D. L., Dahlgren, H., Kintner, P. M., Lessard, M., Lummerzheim, D., Lundberg, E. T., Nicolls, M. J., Stenbaek-Nielsen, H. C.

“…The Cascades‐2 sounding rocket was launched on 20 March 2009 at 11:04:00 UT from the Poker Flat Research Range in Alaska, and flew across a series of poleward…”
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Simultaneous observations of small multi-scale structures in an auroral arc by Dahlgren, H., Aikio, A., Kaila, K., Ivchenko, N., Lanchester, B.S., Whiter, D.K., Marklund, G.T.

“…Auroral arcs can develop small-scale distortions known as vortex streets or curls. Other common and somewhat larger spatially periodic distortions are auroral…”
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Dynamics and characteristics of black aurora as observed by high-resolution ground-based imagers and radar by Archer, J, Dahlgren, H, Ivchenko, N, Lanchester, B. S, Marklund, G. T

“…High-resolution, multi-spectral data from the ground-based low-light auroral imager ASK (Auroral Structure and Kinetics) are used to characterize the fine…”
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Radar detection of a localized 1.4 Hz pulsation in auroral plasma, simultaneous with pulsating optical emissions, during a substorm by COSGROVE, R, NICOLLS, M, DAHLGREN, H, RANJAN, S, SANCHEZ, E, DOE, R

“…Many pulsating phenomena are associated with the auroral substorm. It has been considered that some of these phenomena involve kilometer-scale Alfvén waves…”
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