Far ultraviolet instrument technology

Paxton, L. J.; Schaefer, R. K.; Zhang, Yongliang; Kil, H.

doi:10.1002/2016ja023578

Cited by 67 publications

(71 citation statements)

References 111 publications

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“…Images of polar auroral emissions are built up in swathes over a time period of approximately 20 min, as each DMSP spacecraft moves along their polar Sun-synchronous orbital path (Paxton et al, 2018). The images available in the SSUSI public archive have been corrected for dayglow, and radiances are rectified to pierce-point equivalent nadir pointing by the SSUSI project team (Liou et al, 2011;Paxton et al, 2017;Strickland et al, 1995Strickland et al, , 2004Zhang & Paxton, 2008). The high-latitude polar cap of each hemisphere is observed approximately every 1.5 hr by an individual spacecraft.…”

Section: Datamentioning

confidence: 99%

The Evolution of Long‐Duration Cusp Spot Emission During Lobe Reconnection With Respect to Field‐Aligned Currents

et al. 2020

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We track a remarkably bright and persistent auroral cusp spot emission in the high‐latitude Northern Hemisphere polar cap, well inside the main auroral oval, for approximately 11 hr on 16 and 17 June 2012. The auroral emissions are presented in both the Lyman‐α and Lyman‐Birge‐Hopfield bands, as observed by the Special Sensor Ultraviolet Spectrographic Imager on board two of the Defense Meteorological Satellite Programme spacecraft, and supported by detections of precipitating particles by the same spacecraft. The auroral observations are accompanied by patterns of field aligned currents, obtained from the Active Magnetosphere and Planetary Electrodynamics Response Experiment, along with ionospheric convection patterns from the Super Dual Auroral Radar Network. These data provide unprecedented coverage of a cusp spot, unusually seen in both electron and proton aurora. The location and movement of the auroral emissions, current systems, and ionospheric convection patterns are extremely distorted under the northward to Y‐component‐dominated interplanetary magnetic field. The cusp spot emission region is associated with the sunward flow region of the ionosphere. Ion dispersion signatures are detected on traversal of the region of brightest proton auroral emissions. Proton‐excited Lyman‐α emissions are most evident following impulses of high solar wind density. The auroral emissions, field‐aligned current patterns, and ionospheric convection are consistent with a model of a compressed magnetosphere under strongly northward interplanetary magnetic field, following an impact of an Interplanetary Coronal Mass Ejection and associated magnetic cloud at the magnetopause, inducing high‐latitude lobe reconnection that progresses increasingly tailward during the presented interval.

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Section: Datamentioning

confidence: 99%

The Evolution of Long‐Duration Cusp Spot Emission During Lobe Reconnection With Respect to Field‐Aligned Currents

et al. 2020

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“…Images of the auroras are built up in swaths as the satellites move along their polar Sun‐synchronous orbital paths, building up a scan of the polar auroral emissions in approximately 20 min. Dayglow removal algorithms are applied to the data by the SSUSI project team (Liou et al, ; Paxton et al, ; Strickland et al, , ; Zhang & Paxton, ). Dayglow is removed per pixel, maximizes at 80° solar zenith angle, and falls off smoothly and sharply with increasing solar zenith angle and along the cross‐track direction from the dayside to the nightside.…”

Section: Datamentioning

confidence: 99%

The Association of High‐Latitude Dayside Aurora With NBZ Field‐Aligned Currents

et al. 2018

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The relationship between auroral emissions in the polar ionosphere and the large-scale flow of current within the Earth's magnetosphere has yet to be comprehensively established. Under northward interplanetary magnetic field (IMF) conditions, magnetic reconnection occurs at the high-latitude magnetopause, exciting two reverse lobe convection cells in the dayside polar ionosphere and allowing ingress of solar wind plasma to form an auroral "cusp spot" by direct impact on the atmosphere. It has been hypothesized that a second class of NBZ auroras, High-latitude Dayside Aurora, are produced by upward field-aligned currents associated with lobe convection. Here we present data from the Special Sensor Ultraviolet Spectrographic Imager instrument and from the Active Magnetosphere and Planetary Electrodynamics Response Experiment, from January 2010 to September 2013, in a large statistical study. We reveal a northward IMF auroral phenomenon that is located adjacent to the cusp spot and that is colocated with a region of upward electrical current in the clockwise-rotating lobe cell. The emission only occurs in the sunlit summer hemisphere, demonstrating the influence of the conductance of the ionosphere on current closure. In addition, fast solar wind speed is required for this emission to be bright. The results show that dayside auroral emission is produced by IMF-magnetosphere electrodynamic coupling, as well as by direct impact of the atmosphere by the solar wind, confirming the association of High-latitude Dayside Aurora with NBZ currents. Plain Language SummaryUnder certain incoming solar wind conditions, patches of aurora are sometimes found not in the main bright auroral oval but inside the normally otherwise dark polar cap region. These patches of auroral emissions are colocated with regions of upward flowing electrical current. We present a study of these emissions using nearly 3 years of data from both the North and South Hemispheres, combining simultaneous observations of the polar cap at ultraviolet wavelengths, and measurements of field-aligned currents. This builds on the previous work of other authors, who observed these auroral emissions in the Northern Hemisphere only. The upward current associated auroral emissions occur when the incoming interplanetary magnetic field is northward and are shown to only be observable in the summer hemisphere. This implies a dependence on the conductance of the ionosphere, via photoionization, on the appearance of these auroras.

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“…Far‐ultraviolet auroral images were also available from space, at least during times of favorable overpasses by one of the DMSP F16 to F18 satellites. These images were obtained using the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) hyperspectral imaging instruments, which were recently reviewed by Paxton et al (). They provide hyperspectral images of the aurora and airglow from space, with 160 spectral samples that cover an overall wavelength range from 115 to 180 nm.…”

Section: Instrumentationmentioning

confidence: 99%

Multiinstrument Studies of Thermospheric Weather Above Alaska

et al. 2018

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We describe how space weather impacts thermospheric winds above Alaska, using an array of ground and space-based instrumentation. Forcing of the thermosphere is observed using coherent (Super Dual Auroral Radar Network) and incoherent (Poker Flat Incoherent Scatter Radar) radars to measure ion convection, plus ground and space-based imagers to map auroral precipitation. The primary emphasis in this work is to determine the neutral thermospheric wind response at F region heights to these drivers, using an array of ground-based all-sky imaging Fabry-Perot spectrometers that record Doppler spectra of optical emissions at 630-nm wavelength, originating from a height of around 240 km. Line-of-sight winds are derived from Doppler shifts and, because each instrument only directly measures this one component, considerable postprocessing must be applied to infer the full three-component vector velocity field. Several techniques for doing so are identified, and a detailed description is presented of the hybrid algorithm used here. Results show that thermospheric winds at these latitudes respond strongly to magnetospheric drivers associated with the aurora over length scales down 100 km or less, and on time scales as short as 15 min. These scales are considerably smaller than those resolved by previous observations, or those captured in semiempirical models such as the Horizontal Wind Model or global-scale first principle models such as the Thermospheric Global Circulation Model and its relatives. Divergence and vorticity commonly occur in the observed horizontal wind fields, over regions spanning hundred of kilometers across and with magnitudes exceeding 0.5 × 10 − 3 s −1 . Plain Language Summary This article combines data from multiple instruments to show howEarth's aurora and flows of ionosphere plasma perturb winds in the neutral atmosphere at 240-km altitude. It shows how atmospheric weather at this height is driven by space weather.

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Far ultraviolet instrument technology

Cited by 67 publications

References 111 publications

The Evolution of Long‐Duration Cusp Spot Emission During Lobe Reconnection With Respect to Field‐Aligned Currents

The Evolution of Long‐Duration Cusp Spot Emission During Lobe Reconnection With Respect to Field‐Aligned Currents

The Association of High‐Latitude Dayside Aurora With NBZ Field‐Aligned Currents

Multiinstrument Studies of Thermospheric Weather Above Alaska

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