SSUSI Bibliography
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Notice:
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Found 120 entries in the Bibliography.
Showing entries from 1 through 50
| 2015 |
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A data assimilation algorithm is used to delineate the time-dependent three-dimensional ionospheric response to the 2009 sudden stratospheric warming (SSW) event. We use the Ionospheric Data Assimilation Four-Dimensional (IDA4D) algorithm to study the global ionospheric response to the 2009 SSW. This is the first study to utilize global ionospheric measurements in a data assimilation framework to unambiguously characterize atmosphere-ionosphere coupling via tidal modifications during the 2009 SSW event. Model results reveal that the dominant mode of ionospheric variability during the 2009 SSW is driven by the enhancements in westward propagating semidiurnal tide with zonal wave number 1. The IDA4D results completely characterize the tidal perturbation during the 2009 SSW for the first time and show the global 3-D structure of the tide in total electron content (TEC) and electron density. The largest ionospheric responses were seen at low latitudes, where ionospheric plasma is extremely sensitive to the zonal electric field and susceptible to modifications by tidal winds in the lower thermosphere. The ionospheric response to the warming was characterized by an increase in TEC in the morning/early afternoon sector and a decrease during the late afternoon/evening period. The effects of coupling between the stratosphere and ionosphere were strongest between 220 km and 380 km. The IDA4D results also show a reversal of asymmetry in the equatorial ionization anomaly crests occurring several days after the peak of the 2009 SSW event. We suggest that this could be a result of the equatorial fountain effect being further modified by the summer-to-winter meridional neutral winds. Azeem, I.; Crowley, G.; Honniball, C.; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2015 YEAR: 2015 DOI: 10.1002/2015JA020993 atmospheric tides; Data Assimilation; ionosphere/atmosphere interactions; sudden stratospheric warming |
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The International Reference Ionosphere \textendash Status 2013 This paper describes the latest version of the International Reference Ionosphere (IRI) model. IRI-2012 includes new models for the electron density and ion densities in the region below the F-peak, a storm-time model for the auroral E-region, an improved electron temperature model that includes variations with solar activity, and for the first time a description of auroral boundaries. In addition, the thermosphere model required for baseline neutral densities and temperatures was upgraded from MSIS-86 to the newer NRLMSIS-00 model and Corrected Geomagnetic coordinates (CGM) were included in IRI as an additional coordinate system for a better representation of auroral and polar latitudes. Ongoing IRI activities towards the inclusion of an improved model for the F2 peak height hmF2 are discussed as are efforts to develop a \textquotedblleftReal-Time IRI\textquotedblright. The paper is based on an IRI status report presented at the 2013 IRI Workshop in Olsztyn, Poland. The IRI homepage is at\ IRImodel.org. Published by: Advances in Space Research Published on: 04/2015 YEAR: 2015 DOI: 10.1016/j.asr.2014.07.032 |
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A methodology for evaluating the science benefit of adding space weather sensor data from a modest number of small satellites to the Utah State University Global Assimilation of Ionospheric Measurements\textemdashFull Physics (GAIM-FP) model is presented. Three orbital scenarios are presented, two focusing on improved coverage of narrowly specified regions of interest, and one on global coverage of the ionosphere as a whole. An Observing System Simulation Experiment is used to obtain qualitative and quantitative results of the impact of the various orbital scenarios on the ionospheric specifications. A simulated \textquotedbllefttruth\textquotedblright run of the ionosphere is obtained from a first principle model of the ionosphere/plasmasphere model and used to generate global simulated Global Positioning Satellite total electron content (GPS-TEC) data as well as in situ plasma density observations. Initially, only GPS data were assimilated by GAIM-FP, and the results of this limited run were compared to the truth run. Next, the simulated in situ plasma densities corresponding to our three orbital scenarios were assimilated together with the GPS data, and the results were compared to both the truth run and the limited GPS-TEC only GAIM-FP run. These model simulations have shown that adding a constellation of small satellites/sensors in addition to global TEC inputs does indeed converge the GAIM-FP model closer to truth in the situations described. Balthazor, Richard; McHarg, Matthew; Enloe, Lon; Mueller, Brandon; Barnhart, David; Hoeffner, Zachary; Brown, Robert; Scherliess, Ludger; Wilhelm, Lance; Published by: Radio Science Published on: 04/2015 YEAR: 2015 DOI: 10.1002/2014RS005426 |
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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 |
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A new technique for remote sensing of O 2 density from 140 to 180 km Observations of molecular oxygen are difficult to make in the Earth\textquoterights atmosphere between 140 and 200 km altitude. Perhaps the most accurate measurements to date have been obtained from satellite instruments that measure solar occultations of the limb. These do provide height-resolved O2 density measurements, but the nature of this technique is such that the temporal/spatial distribution of the measurements is uneven. Here a new space-based technique is described that utilizes two bright dayglow emissions, the (0,0) transition of the O2 atmospheric band and the O I (630 nm), to derive the height-resolved O2 density from 140 to 180 km. Data from the Remote Atmospheric and Ionospheric Detection System, which was placed on the International Space Station in late 2009, are used to illustrate this technique. The O2 density results for periods in May 2010 that were geomagnetically quiet and disturbed are compared to model predictions. Hecht, James; Christensen, Andrew; Yee, Jeng-Hwa; Crowley, Geoff; Bishop, Rebeeca; Budzien, Scott; Stephan, Andrew; Evans, Scott; Published by: Geophysical Research Letters Published on: 01/2015 YEAR: 2015 DOI: 10.1002/2014GL062355 |
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The Global Ultraviolet Imager (GUVI) onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite senses far ultraviolet emissions from O and N2 in the thermosphere. Transformation of far ultraviolet radiances measured on the Earth limb into O, N2, and O2 number densities and temperature quantifies these responses and demonstrates the value of simultaneous altitude and geographic information. Composition and temperature variations are available from 2002 to 2007. This paper documents the extraction of these data products from the limb emission rates. We present the characteristics of the GUVI limb observations, retrievals of thermospheric neutral composition and temperature from the forward model, and the dramatic changes of the thermosphere with the solar cycle and geomagnetic activity. We examine the solar extreme ultraviolet (EUV) irradiance magnitude and trends through comparison with simultaneous Solar Extreme EUV (SEE) measurements on TIMED and find the EUV irradiance inferred from GUVI averaged (2002\textendash2007) 30\% lower magnitude than SEE version 11 and varied less with solar activity. The smaller GUVI variability is not consistent with the view that lower solar EUV radiation during the past solar minimum is the cause of historically low thermospheric mass densities. Thermospheric O and N2 densities are lower than the NRLMSISE-00 model, but O2 is consistent. We list some lessons learned from the GUVI program along with several unresolved issues. Meier, R.; Picone, J.; Drob, D.; Bishop, J.; Emmert, J.; Lean, J.; Stephan, A.; Strickland, D.; Christensen, A.; Paxton, L.; Morrison, D.; Kil, H.; Wolven, B.; Woods, Thomas; Crowley, G.; Gibson, S.; Published by: Earth and Space Science Published on: 01/2015 YEAR: 2015 DOI: 10.1002/2014EA000035 airglow and aurora; thermosphere: composition and chemistry; thermosphere: energy deposition; remote sensing |
| 2014 |
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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 (dΦMP/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 (dΦMP/dt \> 1.2 MWb/s which roughly corresponds to\ Kp = 5+ or 6-). The range of validity is approximately 0 \< dΦMP/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 |
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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 |
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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 |
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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 |
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The Earth\textquoterights ionosphere is a highly dynamic region that is almost constantly in a state of flux. Solar radiation, geomagnetic activity, chemical reactions, and natural dynamics all act to perturb the state of the ionosphere. The ionosphere changes on time scales of hours to days, with the fine-scale ionospheric structures that are frequently observed lacking in global physics-based models due to time-step and spatial resolution constraints. To properly specify the ionosphere, data is needed, thus data assimilation. The Utah State University GAIM-GM model uses a data assimilation method to correct a physics-based model of the ionosphere using 5 different data types, divided into 9 different data sources. Multiple data types are necessary because the data from any individual data source will not be sufficient for global reconstructions. The GAIM-GM specification (in real-time) can then be used to correct for ionospheric propagation delays, thereby improving geo-location and communications. The focus here is to show the quantitative effects that multiple data types have on GAIM-GM ionospheric specifications for a relatively quiet day (April 19) in 2012. Gardner, L.; Schunk, R.; Scherliess, L.; Sojka, J.; Zhu, L.; Published by: Space Weather Published on: 11/2014 YEAR: 2014 DOI: 10.1002/2014SW001104 |
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Local Geomagnetic Indices and the Prediction of Auroral Power The aurora has been related to magnetometer observations for centuries, and to geomagnetic indices for decades. As the number of stations and data processing power increases, just how auroral power (AP) relates to geomagnetic observations becomes a more tractable question. This paper compares Polar UVI AP observations during 1997 with a variety of indices. Local time (LT) versions of the SuperMAG auroral electrojet (SME) are introduced and examined, along with the corresponding upper and lower envelopes (SMU\ and\ SML). Also, the East\textendashwest component,\ BE, is investigated. We also consider whether using any of the local indices is actually better at predicting local AP than a single global index. Each index is separated into 24 LT indices with a sliding 3-h MLT window. The ability to predict AP varies greatly with LT, peaking at 1900 MLT, where about 75\% of the variance (r2) is predicted at 1-min cadence. The aurora is fairly predictable from 1700 MLT \textendash 0400 MLT, roughly the region in which substorms occur. AP is poorly predicted from auroral electrojet indices from 0500 MLT \textendash 1500 MLT, with the minimum at 1000\textendash1300 MLT. In the region of high predictability, the local index which works best is\ BE\ (East\textendashwest), in contrast to long-standing expectations. However using global\ SME\ is better than any local index.\ AP\ is best predicted by combining global\ SME\ with a local index:\ BE\ from 1500\textendash0300 MLT, and either\ SMU\ or\ SML\ from 0300\textendash1500 MLT. In the region of the diffuse aurora, it is better to use a 30 min average than the cotemporaneous 1-min\ SME\ value, while from 1500\textendash0200 MLT the cotemporaneous 1-min\ SME\ works best, suggesting a more direct physical relationship with the auroral circuit. These results suggest a significant role for discrete auroral currents closing locally with Pedersen currents. Published by: Journal of Geophysical Research: Space Physics Published on: 11/2014 YEAR: 2014 DOI: 10.1002/2014JA020524 Aurora; indices; auroral electrojet; Pedersen current; prediction |
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Progress toward forecasting of space weather effects on UHF SATCOM after Operation Anaconda Space weather impacts on communications are often presented as a\ raison d\textquoterightetre\ for studying space weather (e.g., Solar and Space Physics: A Science for a Technological Society, 2013). Here we consider a communications outage during Operation Anaconda in Afghanistan that may have been related to ionospheric disturbances. Early military operations occurred during the peak of solar cycle 23 when ionospheric variability was enhanced. During Operation Anaconda, the Battle of Takur Ghar occurred at the summit of a 3191 m Afghan mountaintop on 4 March 2002 when the ionosphere was disturbed and could have affected UHF Satellite Communications (SATCOM). In this paper, we consider UHF SATCOM outages that occurred during repeated attempts to notify a Quick Reaction Force (QRF) on board an MH-47H Chinook to avoid a \textquotedbllefthot\textquotedblright landing zone at the top of Takur Ghar. During a subsequent analysis of Operation Anaconda, these outages were attributed to poor performance of the UHF radios on the helicopters and to blockage by terrain. However, it is also possible that ionospheric anomalies together with multipath effects could have combined to decrease the signal-to-noise ratio of the communication links used by the QRF. A forensics study of Takur Ghar with data from the Global Ultraviolet Imager on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics mission showed the presence of ionospheric bubbles (regions of depleted electron density) along the line of sight between the Chinook and the UHF communications satellites in geostationary orbit that could have impacted communications. The events of 4 March 2002 motivated us to develop the Mesoscale Ionospheric Simulation Testbed model, which can be used to improve warnings of potential UHF outages during future military operations. Kelly, Michael; Comberiate, Joseph; Miller, Ethan; Paxton, Larry; Published by: Space Weather Published on: 10/2014 YEAR: 2014 DOI: 10.1002/2014SW001081 |
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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 |
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The CERTO radio beacon on the C/NOFS satellite sends VHF/UHF radio signals at 150 and 400 MHz to provide measurements of integrated electron density or Total Electron Content (TEC) by an east-west chain of ground receivers in Peru. Computerized Ionospheric Tomography (CIT) is used to convert the TEC data into two-dimensional images of electron densities with maximum 5 \texttimes 5 km resolution in Longitude-Altitude space. These images are updated every 95 min as the C/NOFS satellite passes over the receiver network in its low-latitude orbit with an inclination of 12\textdegree. The 2-D, high-resolution images of the ionosphere are used to predict the impact of equatorial plasma structures on HF propagation of radar and radio signals. Electron density measurements from the NRL radio tomography chain across Peru are used for simulations of the performance by HF one-way links. HF rays from transmitter to receiver are traced through the electron density images produced by radio beacon tomography. Eight separate paths are found between a transmitter and ground receiver separated by 2000 km. A total of 36 backscatter echoes are found with unique group delay, Doppler frequency shift, phase delay, and echo amplitude. This multipath effect explains the range and Doppler spreading of observations for HF monostatic radar propagation through\ F\ layer irregularities. This type of analysis is useful for prediction and interpretation of range and Doppler observations from HF systems including over-the-horizon and SuperDARN radars, HF Geolocation Arrays, and HF communications networks. Bernhardt, Paul; Hei, Matthew; Siefring, Carl; Wilkens, Matthew; Published by: Radio Science Published on: 07/2014 YEAR: 2014 DOI: 10.1002/rds.v49.710.1002/2014RS005409 |
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Circumpolar ground-based optical measurements of proton and electron shock aurora Meridian scanning photometer (MSP) data are combined with global ultraviolet images from the Polar Ultraviolet Imager instrument to estimate the timing and propagation speed of shock auroras previously studied using solely space-based ultraviolet auroral imagery. The multispectral nature of the MSPs, including the presence of a Balmer beta channel, enables the discrimination between proton and electron aurora. Following a near-magnetic noon onset, the occurrence of auroral emissions created by shocked precipitating protons and electrons is observed to propagate tailward, along the auroral oval with speeds of several km/s, consistent with the shock propagation speed in the solar wind. In two cases, shock aurora propagation speeds along the auroral oval determined from satellite imagery are confirmed, to within calculated uncertainties, with ground-based timing. The majority of instruments detect low-energy discrete auroral arcs poleward of diffuse, higher-energy aurora. Evidence of a previously reported two-pulse proton aurora shock onset is detected at some, but not all, locations. Holmes, J.; Johnsen, M.; Deehr, C.; Zhou, X.-Y.; Lorentzen, D.; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2014 YEAR: 2014 DOI: 10.1002/2013JA019574 |
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A Method to Calculate the Ionospheric LBH Dayglow Emissions for Large Field of View LBH dayglow emissions in the ionosphere, produced by the photoelectrons impact on the nitrogen molecules, are the most prominent molecular signals in the far ultraviolet range. Imaging the LBH dayglow emissions from the space can be a powerful method to monitor the state of the upper atmosphere. According to direct excitation theory and spherical geometry, the spectral characteristics of the LBH emission are analyzed and a revised method (RAURIC) to calculate the column emission rate of the LBH dayglow emissions for large field of view is given. Two main limitations of AURIC, that are the definition of the observation azimuth angle and the treating of the solar zenith angle as a constant along a line of sight, are improved in RAURIC. The column emission rates of the LBH bands in the range of 140\~180 nm are calculated with the method. Comparisons with results from AURIC show great agreement in nadir, while RAURIC should be used in other lines of light, especially for large field of view. This work provides a solid basis for simulating the image of ionospheric LBH dayglow emissions and the data inversion technique. Yong-Chao, ZHANG; Fei, HE; Xiao-Xin, ZHANG; Bo, CHEN; Published by: Chinese Journal of Geophysics Published on: 03/2014 YEAR: 2014 DOI: 10.1002/cjg2.2014.57.issue-210.1002/cjg2.20099 |
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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 |
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Published by: Journal of Geophysical Research: Space Physics Published on: Jan-10-2013 YEAR: 2013 DOI: 10.1002/jgra.v118.1010.1002/jgra.50505 |
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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 |
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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 |
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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 |
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Published by: Published on: |
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Knight, HK; Galkin, IA; Reinisch, BW; Paxton, L; Published by: Published on: |
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Kinrade, Joe; Mitchell, Cathryn; Paxton, Larry; Bust, Gary; Published by: Published on: |
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Geophysical Monograph SeriesSpace WeatherSpace Weather-Lessons from the Meteorologists Published by: Published on: YEAR: 2013 DOI: 10.1029/GM125p0031 |
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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: |
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The Mesoscale Ionospheric Simulation Testbed (MIST) Regional Data Assimilation Model The Mesoscale Ionospheric Simulation Testbed (MIST) provides a regional nowcast and forecast of electron density values and has sufficient resolution to include equatorial plasma bubbles. The SSUSI instrument on the DMSP F18 satellite has high-resolution nightly observations of plasma bubbles at 8 PM local time throughout the current solar maximum. MIST can assimilate SSUSI UV observations, GPS TEC measurements, and SCINDA S4 readings simultaneously into a single scintillation map over a region of interest. MIST also models ionospheric physics to provide a short-term UHF scintillation forecast based on assimilated data. We will present examples of electron density and scintillation maps from MIST. We will also discuss the potential to predict scintillation occurrence up to 6 hours in advance using observations of the equatorial arcs from SSUSI observations at 5:30 PM local time on the DMSP F17 satellite. Comberiate, J; Kelly, MA; Miller, E; Paxton, L; Published by: Published on: |
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Multi-Instrument Observations at High Latitudes Miller, E; Paxton, L; Schaefer, RK; Weiss, M; Wolven, BC; Zhang, Y; Published by: Published on: |
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Schaefer, RK; Wolven, BC; Paxton, L; Romeo, G; Selby, C; Hsieh, SW; Published by: Published on: |
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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: 0355 ATMOSPHERIC COMPOSITION AND STRUCTURE Thermosphere: composition and chemistry; 2407 IONOSPHERE Auroral ionosphere; 2415 IONOSPHERE Equatorial ionosphere; 7954 SPACE WEATHER Magnetic storms |
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Hsieh, S.~W.; Zhang, Y.; Schaefer, R.~K.; Romeo, G.; Paxton, L.; Published by: AGU Fall Meeting Abstracts Published on: 2431 IONOSPHERE Ionosphere/magnetosphere interactions; 2447 IONOSPHERE Modeling and forecasting; 2704 MAGNETOSPHERIC PHYSICS Auroral phenomena; 2722 MAGNETOSPHERIC PHYSICS Forecasting |
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Stormtime Magnetosphere-Ionosphere-Thermosphere Interactions and Dynamics Doherty, Patricia; Burke, William; Marcos, Frank; Delay, Susan; Published by: Published on: |
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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; Published by: Published on: |
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Validation of Auroral Oval Models Using DMSP SSUSI Published by: Published on: |
| 2012 |
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Knight, HK; Strickland, DJ; Correira, J; Hecht, JH; Straus, PR; Published by: Journal of Geophysical Research: Space Physics (1978\textendash2012) Published on: |
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| 2011 |
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A downward revision of a recently reported proton auroral LBH emission efficiency Correira, J.; Strickland, D.; Evans, J.; Knight, H.; Hecht, J.; Published by: Journal of Geophysical Research Published on: Jan-01-2011 YEAR: 2011 DOI: 10.1029/2010JA016016 |
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Comparison of solar energy flux Q$_EUV$ (\lt 45 nm) from SSUSI, GUVI, EVE, SEE, and SEM Correira, J.; Evans, J.~S.; Strickland, D.~J.; Published by: AGU Fall Meeting Abstracts Published on: AND ASTRONOMY / Instruments and techniques; AND ASTRONOMY / Solar irradiance; AND ASTRONOMY / Ultraviolet emissions; ASTROPHYSICS; [7538] SOLAR PHYSICS; [7549] SOLAR PHYSICS; [7594] SOLAR PHYSICS |
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Empirical Relationship Between LBH Auroral Emissions and Particle Precipitation Hsieh, SW; Sotirelis, T; Korth, H; Zhang, Y; Paxton, LJ; Published by: Published on: |
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Estimating Dayside Regions of Dayglow-Free 135.6 nm UV Radiances for Data Assimilation Aiello, J; Toigo, AD; Demajistre, R; Schaefer, RK; Paxton, LJ; Published by: Published on: |
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Comberiate, J; Demajistre, R; Schaefer, RK; Zhang, Y; Paxton, LJ; Published by: Published on: |
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Solar rotational effects in the ionosphere and thermosphere Talaat, ER; Hsieh, SW; Smith, D; Zhu, X; Published by: Published on: |
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Study on spectrograph for ionosphere: a broadband imaging instrument prototype for far-ultraviolet Yu, Lei; Wang, Shu-rong; Lin, Guan-yu; Published by: Published on: YEAR: 2011 DOI: 10.1117/12.895219 |
| 2010 |
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Near real-time assimilation in IRI of auroral peak E-region density and equatorward boundary Zhang, Yongliang; Paxton, Larry; Bilitza, Dieter; Doe, Rick; Published by: Advances in Space Research Published on: Jan-10-2010 YEAR: 2010 DOI: 10.1016/j.asr.2010.06.029 |
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Coordinated UV imaging of equatorial plasma bubbles using TIMED/GUVI and DMSP/SSUSI Comberiate, Joseph; Paxton, Larry; Published by: Space Weather Published on: Jan-01-2010 YEAR: 2010 DOI: 10.1029/2009SW000546 |
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Continued Development and Validation of the USU GAIM Models Published by: Published on: |
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Equatorial Plasma Bubble Climatology and Scintillation Forecasting from DMSP/SSUSI Comberiate, J.; Paxton, L.~J.; Published by: AGU Fall Meeting Abstracts Published on: [2415] IONOSPHERE / Equatorial ionosphere; [2494] IONOSPHERE / Instruments and techniques; [6969] RADIO SCIENCE / Remote sensing; [7924] SPACE WEATHER / Forecasting |
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A new proton auroral extrapolation method applied in the estimation of FUV emission yields Knight, HK; Strickland, DJ; Correira, J; Evans, JS; Hecht, JH; Published by: Published on: |
| 2009 |
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Does the polar cap disappear under an extended strong northward IMF? Zhang, Yongliang; Paxton, Larry; Newell, Patrick; Meng, Ching-I.; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: Jan-12-2009 YEAR: 2009 DOI: 10.1016/j.jastp.2009.09.005 |