Bibliography

Increased Sensitivity FUV Spectrographic Imager

Schaefer, RK; Paxton, LJ; Zhang, Y; Kil, H; Liou, K;

Published by:       Published on:

YEAR: 2022     DOI:

Hemispheric Asymmetry in the Auroral Ionosphere-Thermosphere System

Liou, K; Zhang, Y-L; Paxton, LJ; Kil, H; Schaefer, R;

Published by:       Published on:

YEAR: 2022     DOI:

Hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation

Liou, Kan; Mitchell, Elizabeth;

Published by: Scientific Reports      Published on:

YEAR: 2020     DOI:

Effects of the interplanetary magnetic field y component on the dayside aurora

A dawn\textendashdusk asymmetry in many high-latitude ionospheric and magnetospheric phenomena, including the aurora, can be linked to the east\textendashwest (y) component of the interplanetary magnetic field (IMF). Owing to the scarcity of observations in the Southern Hemisphere, most of the previous findings are associated with the Northern Hemisphere. It has long been suspected that if the IMF B_y component also produces a dawn\textendashdusk asymmetry and/or a mirror image in the Southern Hemisphere as predicted by some theories. The present study explores the effect of the IMF B_y component on the dayside aurora from both hemispheres by analyzing the auroral emission data from the Global UltraViolet scanning spectrograph Imager on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics mission spacecraft from 2002 to 2007. The data set comprises 28,774 partial images of the northern hemispheric oval and 29,742 partial images of the southern hemispheric oval, allowing for a statistical analysis. It is found that even though auroras in different regions of the dayside oval respond differently to the orientation of the IMF B_y component, their responses are opposite between the two hemispheres. For example, at ~ 1400\textendash1600\ MLT in the Northern Hemisphere, where the so-called 1500\ MLT auroral hot spots occur, peak auroral energy flux is larger for negative IMF B_y comparing to positive IMF B_y. The response is reversed in the Southern Hemisphere. The present study also suggests that the total energy flux does not change with the IMF B_y orientation change. This result is consistent with a larger (smaller) convection vortex in the postnoon sector for IMF B_y \< 0 (B_y \> 0) resulting from anti-parallel merging.

Liou, K.; Mitchell, E.;

Published by: Geoscience Letters      Published on: 11/2019

YEAR: 2019     DOI: 10.1186/s40562-019-0141-3

Hemispheric Asymmetry of the Premidnight Aurora Associated With the Dawn-Dusk Component of the Interplanetary Magnetic Field

It has been known for decades that the nightside aurora in the Northern Hemisphere (NH) tends to be brighter when the interplanetary magnetic field (IMF) measured at Earth has a dawnward (negative y) component compared to a duskward (positive y) component. This asymmetric response to the polarity of IMF B_y has been explained by an interhemispheric current flowing out of the NH due to a nonuniform \textquotedblleftpenetration\textquotedblright of IMF B_y onto the magnetotail. If such a hypothesis is correct, it should predict a brighter aurora in the nightside Southern Hemisphere (SH) for positive IMF B_y than negative IMF B_y. Here we investigate this hypothesis using Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics/Global Ultraviolet Imager data. The present study not only reproduces the result previously found in NH but also shows an opposite change to its Northern Hemispheric counterpart in SH in response to the different IMF B_y polarity. When comparing north to south, for negative IMF B_y, the premidnight auroral energy flux is greater in NH than that in SH. The result becomes opposite for positive IMF B_y. This result is consistent with the hypothesis of the existence of an interhemispheric field-aligned current.

Liou, K.; Mitchell, E.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 02/2019

YEAR: 2019     DOI: 10.1029/2018JA025953

North-south Asymmetry in Dayside Auroras Associated With Local Sunlight Conditions

Mitchell, Elizabeth; Liou, Kan;

Published by:       Published on:

YEAR: 2019     DOI:

Inferring nighttime ionospheric parameters with the far ultraviolet imager onboard the ionospheric connection explorer

The Ionospheric Connection Explorer (ICON) Far Ultraviolet (FUV) imager, ICON FUV, will measure altitude profiles of OI 135.6 nm emissions to infer nighttime ionospheric parameters.

Kamalabadi, Farzad; Qin, Jianqi; Harding, Brian; Iliou, Dimitrios; Makela, Jonathan; Meier, RR; England, Scott; Frey, Harald; Mende, Stephen; Immel, Thomas;

Published by: Space science reviews      Published on:

YEAR: 2018     DOI:

Statistical Comparison of Auroras in Northern and Southern Hemispheres

Liou, Kan; , others;

Published by:       Published on:

YEAR: 2018     DOI:

Estimation of electron density in the nighttime ionosphere based on remote sensing of the 135.6 nm far ultraviolet emission

Iliou, Dimitrios;

Published by:       Published on:

YEAR: 2016     DOI:

Auroral precipitation models and space weather

Newell, Patrick; Liou, Kan; Zhang, Yongliang; Sotirelis, Thomas; Mitchell, EJ; Mitchell, Elizabeth;

Published by: Auroral dynamics and space weather      Published on:

YEAR: 2015     DOI:

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\ Kp\ or 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 toKp = 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: 06/2014

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

AURORA; precipitation; forecasting

OVATION Prime-2013: Solar Wind Driven Precipitation Model Extended to Higher Geomagnetic Activity Levels

Newell, Patrick; Liou, Kan; Zhang, Yongliang; Sotirelis, Thomas; Paxton, Larry; Mitchell, Elizabeth;

Published by:       Published on:

YEAR: 2014     DOI:

Statistical comparison of isolated and non-isolated auroral substorms

The present study compares isolated and non-isolated substorms in terms of their global morphology and energy deposition. The analysis is based on a list of geomagnetic substorm onsets identified with magnetometer data from SuperMAG and published previously by Newell and Gjerlove (2011a). Isolated substorms are defined as those with separation of two consecutive onsets no less than 3 h. The auroral data are obtained from the global ultraviolet imager (GUVI) on board the TIMED satellite and are rebinned into typical magnetic latitude-magnetic local time maps. The auroral maps are then averaged in 1 min intervals to show the dynamic change of the aurora. The three phases of the substorm are clearly demonstrated in both isolated and non-isolated substorms. However, there are noticeable differences between the two types of substorms: (1) While the nighttime auroral power for both types of substorms slightly increases in the growth phase, isolated (non-isolated) substorms are associated with smaller (greater) nighttime auroral power. (2) In the expansion phase, isolated substorms are associated with greater and more explosive energy release than non-isolated substorms. (3) The time for the recovery phase is ~2 times longer for isolated than for non-isolated substorms. (4) The winter-to-summer auroral power ratio is approximately constant throughout the three substorm phases and the ratio is larger for isolated (~30\%) than that for non-isolated (~10\%) substorms. It is also found that the polar cap area increases during the growth phase until ~10 min prior to the magnetic substorm onset and decreases rapidly thereafter. The decrease is found to result from the closure of the nightside polar cap associated with substorm expansion. It is found that the observed differences between the two types of substorms simply reflect the differences in the solar wind and EUV drivers. Thus, we conclude that there is no intrinsic difference between isolated and non-isolated substorms in terms of auroral energy release and subsequent auroral power decay.

Liou, Kan; Newell, Patrick; Zhang, Yong-Liang; Paxton, Larry;

Published by: Journal of Geophysical Research: Space Physics      Published on: 05/2013

YEAR: 2013     DOI: 10.1002/jgra.50218

auroral power; auroral substorm; GUVI; SuperMAG; TIMED

TIMED/GUVI observation of solar illumination effect on auroral energy deposition

Liou, K.; Zhang, Y.-L.; Newell, P.; Paxton, L.; Carbary, J.;

Published by: Journal of Geophysical Research      Published on: Jan-01-2011

YEAR: 2011     DOI: 10.1029/2010JA016402

Predictive ability of four auroral precipitation models as evaluated using Polar UVI global images

Newell, P.; Sotirelis, T.; Liou, K.; Lee, A.; Wing, S.; Green, J.; Redmon, R.;

Published by: Space Weather      Published on: Jan-01-2010

YEAR: 2010     DOI: 10.1029/2010SW000604

Ionospheric control of auroral occurrence

Liou, Kan; Zhang, Yongliang; Newell, Patrick; Paxton, Larry;

Published by:       Published on:

YEAR: 2009     DOI:

Oscillations of the equatorward boundary of the ion auroral oval – radar observations

Three SuperDARN radars in the afternoon-midnight sector of the auroral oval detected a boundary oscillation, originating near ∼1800 MLT sector. Analysis of the phase of the oscillations measured in three meridians indicates that the disturbance has a longitudinally (azimuthally) isolated source and away from which it propagates. The eastward and westward phase speeds are 2.6 and 3.6 km/s respectively and the period is roughly 28 minutes. An examination of the geo-synchronous magnetic field inclination also revealed oscillations similar to the oscillations of the boundary. Solar wind and IMF conditions were steady during the period except for variations of the IMF By component. The IMF By component showed variations similar to the oscillations in the boundary and the geo-synchronous magnetic field inclination. During reduced and negative IMF By, the boundary was moving equatorward, while during increased or positive IMF By it was moving poleward. The variations in the magnetic field inclination measured at geosynchronous orbit by the GOES satellites were consistent with these boundary motions: decreases (more stretched) and increases (more dipolar) in the inclination corresponded to equatorward and poleward moving boundaries, respectively. Polar cap convection also showed changes in the direction of the convection in response to the change in the IMF By component. Observed oscillation of the boundary can be explained by stretching of the tail field lines due to asymmetric merging associated with changes in the By component of the interplanetary magnetic field.

Jayachandran, P.; Sato, N.; Ebihara, Y.; Yukimatu, A.; Kadokura, A.; MacDougall, J.; Donovan, E.; Liou, K.;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2008     DOI: https://doi.org/10.1029/2007JA012870

Boundary oscillation; SuperDARN radars; Convection

Synoptical Auroral Ovals: A Comparison study with TIMED/GUVI Observations

Liou, K; Paxton, L; Zhang, Y;

Published by:       Published on:

YEAR: 2007     DOI:

Investigating the state of the Sun-Earth system during extreme events: First science results of a worldwide online conference series

Kozyra, JU; Shibata, K; Fox, NJ; Basu, S; Coster, AJ; Davila, JM; Gopalswamy, N; Liou, K; Lu, G; Mann, IR; , others;

Published by:       Published on:

YEAR: 2006     DOI:

AJ (JHMI)

Lui, ATY; Chapman, SC; Liou, K; Newell, PT; Meng, CI; Brittnacher, M; Parks, GK; Williams, DJ; McEntire, RW; Christon, SP; , others;

Published by: JOHNS HOPKINS APL TECHNICAL DIGEST      Published on:

YEAR: 2000     DOI: