SSUSI Bibliography

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Found 29 entries in the Bibliography.

Showing entries from 1 through 29

2015

GPS phase scintillation at high latitudes during geomagnetic storms of 7\textendash17 March 2012 \textendash Part 2: Interhemispheric comparison

During the ascending phase of solar cycle 24, a series of interplanetary coronal mass ejections (ICMEs) in the period 7\textendash17 March 2012 caused geomagnetic storms that strongly affected high-latitude ionosphere in the Northern and Southern Hemisphere. GPS phase scintillation was observed at northern and southern high latitudes by arrays of GPS ionospheric scintillation and TEC monitors (GISTMs) and geodetic-quality GPS receivers sampling at 1 Hz. Mapped as a function of magnetic latitude and magnetic local time (MLT), the scintillation was observed in the ionospheric cusp, the tongue of ionization fragmented into patches, sun-aligned arcs in the polar cap, and nightside auroral oval and subauroral latitudes. Complementing a companion paper (Prikryl et al., 2015a) that focuses on the highlatitude ionospheric response to variable solar wind in the North American sector, interhemispheric comparison reveals commonalities as well as differences and asymmetries between the northern and southern high latitudes, as a consequence of the coupling between the solar wind and magnetosphere. The interhemispheric asymmetries are caused by the dawn\textendashdusk component of the interplanetary magnetic field controlling the MLT of the cusp entry of the storm-enhanced density plasma into the polar cap and the orientation relative to the noon\textendashmidnight meridian of the tongue of ionization.

Prikryl, P.; Ghoddousi-Fard, R.; Spogli, L.; Mitchell, C.; Li, G.; Ning, B.; Cilliers, P.; Sreeja, V.; Aquino, M.; Terkildsen, M.; Jayachandran, P.; Jiao, Y.; Morton, Y.; Ruohoniemi, J.; Thomas, E.; Zhang, Y.; Weatherwax, A.; Alfonsi, L.; De Franceschi, G.; Romano, V.;

Published by: Annales Geophysicae Published on: 01/2015

YEAR: 2015 DOI: 10.5194/angeo-33-657-2015

Ionosphere; ionospheric disturbance; ionospheric irregularities; polar ionosphere

2014

OVATION Prime-2013: Extension of auroral precipitation model to higher disturbance levels

OVATION Prime (OP) is an auroral precipitation model parameterized by solar wind driving. Distinguishing features of the model include an optimized solar wind-magnetosphere coupling function (dΦ_MP/dt) which predicts auroral power significantly better than\ Kpor other traditional parameters, the separation of aurora into categories (diffuse aurora, monoenergetic, broadband, and ion), the inclusion of seasonal variations, and separate parameter fits for each magnetic latitude (MLAT) \texttimes magnetic local time (MLT) bin, thus permitting each type of aurora and each location to have differing responses to season and solar wind input\textemdashas indeed they do. We here introduce OVATION Prime-2013, an upgrade to the 2010 version currently widely available. The most notable advantage of OP-2013 is that it uses UV images from the GUVI instrument on the satellite TIMED for high disturbance levels (dΦ_MP/dt \> 1.2 MWb/s which roughly corresponds to\ Kp = 5+ or 6-). The range of validity is approximately 0 \< dΦ_MP/dt <= 3.0 MWb/s (Kp\ about 8+). Other upgrades include a reduced susceptibility to salt-and-pepper noise, and smoother interpolation across the postmidnight data gap. The model is tested against an independent data set of hemispheric auroral power from Polar UVI. Over the common range of validity of OP-2010 and OP-2013, the two models predict auroral power essentially identically, primarily because hemispheric power calculations were done in a way to minimize the impact of OP-2010s noise. To quantitatively demonstrate the improvement at high disturbance levels would require multiple very large substorms, which are rare, and insufficiently present in the limited data set of Polar UVI hemispheric power values. Nonetheless, although OP-2010 breaks down in a variety of ways above\ Kp = 5+ or 6-, OP-2013 continues to show the auroral oval advancing equatorward, at least to 55\textdegree MLAT or a bit less, and OP-2013 does not develop spurious large noise patches. We will also discuss the advantages and disadvantages of other precipitation models more generally, as no one model fits best all possible uses.

Newell, P.; Liou, K.; Zhang, Y.; Sotirelis, T.; Paxton, L.; Mitchell, E.;

Published by: Space Weather Published on: Jan-06-2014

YEAR: 2014 DOI: 10.1002/swe.v12.610.1002/2014SW001056

Aurora; forecasting; precipitation

Correction of astigmatism and coma using analytic theory of aberrations in imaging spectrometer based on concentric off-axis dual reflector system

A specific imaging spectrometer based on a concentric off-axis dual reflector system is proposed, free of astigmatism and coma. The described imaging spectrometer consists of four spherical mirrors and a plane grating. The analytic theory of aberrations and the optical path-length concept are used to derive the astigmatism elimination and coma removal. It is shown that the astigmatism in these imaging spectrometers is eliminated by characterizing three angles, and the coma is corrected when unequal mirror radii are configured in collimating and condensing optics. The developed aberration principle is verified by comparing the performance of the astigmatism-eliminated spectrometer with the spectrometer which has neither astigmatism nor coma.

Chen, Ting; Tang, Yi; Zhang, Li; Chang, Yue; Zheng, Cheng;

Published by: Applied Optics Published on: Jan-01-2014

YEAR: 2014 DOI: 10.1364/AO.53.000565

Equatorial broad plasma depletions associated with the enhanced fountain effect

Lee, Woo; Kil, Hyosub; Kwak, Young-Sil; Paxton, Larry; Zhang, Yongliang; Galkin, Ivan; Batista, Inez;

Published by: Journal of Geophysical Research: Space Physics Published on: Jan-01-2014

YEAR: 2014 DOI: 10.1002/jgra.v119.110.1002/2013JA019137

The International Reference Ionosphere 2012 \textendash a model of international collaboration

The International Reference Ionosphere (IRI) project was established jointly by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI) in the late sixties with the goal to develop an international standard for the specification of plasma parameters in the Earth\textquoterights ionosphere. COSPAR needed such a specification for the evaluation of environmental effects on spacecraft and experiments in space, and URSI for radiowave propagation studies and applications. At the request of COSPAR and URSI, IRI was developed as a data-based model to avoid the uncertainty of theory-based models which are only as good as the evolving theoretical understanding. Being based on most of the available and reliable observations of the ionospheric plasma from the ground and from space, IRI describes monthly averages of electron density, electron temperature, ion temperature, ion composition, and several additional parameters in the altitude range from 60\ km to 2000\ km. A working group of about 50 international ionospheric experts is in charge of developing and improving the IRI model. Over time as new data became available and new modeling techniques emerged, steadily improved editions of the IRI model have been published. This paper gives a brief history of the IRI project and describes the latest version of the model, IRI-2012. It also briefly discusses efforts to develop a real-time IRI model. The IRI homepage is at\ http://IRImodel.org.

Bilitza, Dieter; Altadill, David; Zhang, Yongliang; Mertens, Chris; Truhlik, Vladimir; Richards, Phil; McKinnell, Lee-Anne; Reinisch, Bodo;

Published by: Journal of Space Weather and Space Climate Published on: Jan-01-2014

YEAR: 2014 DOI: 10.1051/swsc/2014004

Statistical relationship between large-scale upward field-aligned currents and electron precipitation

Simultaneous observations of Birkeland currents by the constellation of Iridium satellites and N₂\ Lyman-Birge-Hopfield (LBH) auroral emissions measured by the Global Ultraviolet Imager (GUVI) onboard the Thermosphere, Ionosphere, and Mesosphere Energetics and Dynamics (TIMED) satellite are used to establish relationships between large-scale upward field-aligned currents and electron precipitation during stable current configurations. The electron precipitation was inferred from GUVI data using a statistical relationship between LBH intensity and electron energy flux. LBH emissions with \>5\% contribution from protons, identified by Lyman-alpha intensity, were excluded from the analysis. The Birkeland currents were derived with a spatial resolution of 3\textdegree in latitude and 2 h in local time. For southward interplanetary magnetic field (IMF), the electron precipitation occurred primarily within and near large-scale upward currents. The correspondence was less evident for northward IMF, presumably because the spatial variability is large compared to the areas of interest so that the number of events identified is smaller and the derived statistical distributions are less reliable. At dusk, the correlation between upward current and precipitation was especially high, where a larger fraction of the electron precipitation is accelerated downward by a field-aligned potential difference. Unaccelerated electron precipitation dominated in the morning sector, presumably induced by scattering of eastward-drifting energetic electrons into the loss cone through interaction with whistler-mode waves (diffuse precipitation) rather than by field-aligned acceleration. In the upward Region 1 on the dayside, where the electron precipitation is almost exclusively due to field-aligned acceleration, a quadratic relationship between current density and electron energy flux was observed, implying a linear current-voltage relationship in this region. Current density and electron energy flux in the regions of the large-scale upward currents from pre-midnight through dawn to noon are essentially uncorrelated, consistent with diffuse electron precipitation dominating the incident energy flux.

Korth, Haje; Zhang, Yongliang; Anderson, Brian; Sotirelis, Thomas; Waters, Colin;

Published by: Journal of Geophysical Research: Space Physics Published on: 08/2014

YEAR: 2014 DOI: 10.1002/2014JA019961

auroral emissions; Birkeland currents; current-precipitation relationship; current-voltage relationship; electron precipitation

In situ spatiotemporal measurements of the detailed azimuthal substructure of the substorm current wedge

The substorm current wedge (SCW) is a fundamental component of geomagnetic substorms. Models tend to describe the SCW as a simple line current flowing into the ionosphere toward dawn and out of the ionosphere toward dusk, linked by a westward electrojet. We use multispacecraft observations from perigee passes of the Cluster 1 and 4 spacecraft during a substorm on 15 January 2010, in conjunction with ground-based observations, to examine the spatial structuring and temporal variability of the SCW. At this time, the spacecraft traveled east-west azimuthally above the auroral region. We show that the SCW has significant azimuthal substructure on scales of 100 km at altitudes of 4000\textendash7000 km. We identify 26 individual current sheets in the Cluster 4 data and 34 individual current sheets in the Cluster 1 data, with Cluster 1 passing through the SCW 120\textendash240 s after Cluster 4 at 1300\textendash2000 km higher altitude. Both spacecraft observed large-scale regions of net upward and downward field-aligned current, consistent with the large-scale characteristics of the SCW, although sheets of oppositely directed currents were observed within both regions. We show that the majority of these current sheets were closely aligned to a north-south direction, in contrast to the expected east-west orientation of the preonset aurora. Comparing our results with observations of the field-aligned current associated with bursty bulk flows (BBFs), we conclude that significant questions remain for the explanation of SCW structuring by BBF-driven \textquotedblleftwedgelets.\textquotedblright Our results therefore represent constraints on future modeling and theoretical frameworks on the generation of the SCW.

Forsyth, C.; Fazakerley, A.; Rae, I.; Watt, C.; Murphy, K.; Wild, J.; Karlsson, T.; Mutel, R.; Owen, C.; Ergun, R.; Masson, A.; Berthomier, M.; Donovan, E.; Frey, H.; Matzka, J.; Stolle, C.; Zhang, Y.;

Published by: Journal of Geophysical Research: Space Physics Published on: 02/2014

YEAR: 2014 DOI: 10.1002/2013JA019302

Aurora; Field-aligned current; Magnetosphere; Substorm current wedge; Wedgelets

2013

Reply to comment on \textquotedblleftEmpirical relationship between electron precipitation and far-ultraviolet auroral emissions from DMSP observations\textquotedblright

Sotirelis, Thomas; Korth, Haje; Hsieh, Syau-Yun; Zhang, Yongliang; Morrison, Daniel; Paxton, Larry;

Published by: Journal of Geophysical Research: Space Physics Published on: Jan-10-2013

YEAR: 2013 DOI: 10.1002/jgra.v118.1010.1002/jgra.50507

Nightside midlatitude ionospheric arcs: TIMED/GUVI observations

Zhang, Yongliang; Paxton, Larry; Kil, Hyosub;

Published by: Journal of Geophysical Research: Space Physics Published on: Jan-06-2013

YEAR: 2013 DOI: 10.1002/jgra.50327

Empirical relationship between electron precipitation and far-ultraviolet auroral emissions from DMSP observations

Sotirelis, Thomas; Korth, Haje; Hsieh, Syau-Yun; Zhang, Yongliang; Morrison, Daniel; Paxton, Larry;

Published by: Journal of Geophysical Research: Space Physics Published on: Jan-03-2013

YEAR: 2013 DOI: 10.1002/jgra.50157

An interhemispheric comparison of GPS phase scintillation with auroral emission observed at the South Pole and from the DMSP satellite

Prikryl, Paul; Zhang, Yongliang; Ebihara, Yusuke; Ghoddousi-Fard, Reza; Jayachandran, Periyadan; Kinrade, Joe; Mitchell, Cathryn; Weatherwax, Allan; Bust, Gary; Cilliers, Pierre;

Published by: Annals of Geophysics Published on:

YEAR: 2013 DOI:

Multi-Instrument Observations at High Latitudes

Miller, E; Paxton, L; Schaefer, RK; Weiss, M; Wolven, BC; Zhang, Y;

Published by: Published on:

YEAR: 2013 DOI:

SSUSI: A Newly Available Resource for the Upper Atmosphere Community to Study the Global Response of the Coupled Ionosphere Thermosphere System

The Global Ultraviolet Imager (GUVI) on TIMED was actually the 7th wide field of regard instrument built by APL. Five SSUSI instruments were built by APL and delivered, calibrated and ready for flight between 1994 and 1996. Another instrument, the Near Infrared Spectrograph was flown on the NASA NEAR mission using the SSUSI optical design. The first SSUSI flight was in 2003 on the DMSP F16 spacecraft. Two others have flown since then on DMSP F17 and F18. Two more await flight with the next slated for a Spring 2014 launch on DMSP F19. Recently, the SSUSI data have been made publicly releasable so they are, in principle, available to the research community. However, there are no funds to actually provide access to these products. We are working with various partners to provide a venue to access to the many products we routinely produce. SSUSI provides data products that both monitor the state of the auroral regions and yields a detailed picture of the ionosphere. SSUSI gives us the ability to observe the dynamics of these systems during storm and quiet periods throughout an entire solar cycle. The near polar orbit of the DMSP satellite provided excellent coverage of the auroral oval during solar minimum. During storm times, the high inclination orbit allows us to track the progress of the storm with 30 minute revisit time. In this presentation, we will also discuss the ability of SSUSI to image ionospheric dynamics and provide 3D images of the ionosphere. These data, when combined with assimilative data techniques provides a powerful new capability for examining the small and large scale structure of the ionosphere in a way that is not accessible to either GOLD or ICON.

Paxton, L.; Schaefer, R.~K.; Weiss, M.; Wolven, B.~C.; Zhang, Y.; Miller, E.; Bust, G.~S.; Romeo, G.;

Published by: AGU Fall Meeting Abstracts Published on:

YEAR: 2013 DOI:

0355 ATMOSPHERIC COMPOSITION AND STRUCTURE Thermosphere: composition and chemistry; 2407 IONOSPHERE Auroral ionosphere; 2415 IONOSPHERE Equatorial ionosphere; 7954 SPACE WEATHER Magnetic storms

SSUSI Aurora Forecast Model

Hsieh, S.~W.; Zhang, Y.; Schaefer, R.~K.; Romeo, G.; Paxton, L.;

Published by: AGU Fall Meeting Abstracts Published on:

YEAR: 2013 DOI:

2431 IONOSPHERE Ionosphere/magnetosphere interactions; 2447 IONOSPHERE Modeling and forecasting; 2704 MAGNETOSPHERIC PHYSICS Auroral phenomena; 2722 MAGNETOSPHERIC PHYSICS Forecasting

UV Remote Sensing Data Products-Turning Data Into Knowledge

Weiss, M; Paxton, L; Schaefer, RK; Comberiate, J; Hsieh, SW; Romeo, G; Wolven, BC; Zhang, Y;

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