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Found 97 entries in the Bibliography.

Showing entries from 51 through 97

2016

Ionospheric data assimilation with thermosphere-ionosphere-electrodynamics general circulation model and GPS-TEC during geomagnetic storm conditions

The main purpose of this paper is to investigate the effects of rapid assimilation-forecast cycling on the performance of ionospheric data assimilation during geomagnetic storm conditions. An ensemble Kalman filter software developed by the National Center for Atmospheric Research (NCAR), called Data Assimilation Research Testbed, is applied to assimilate ground-based GPS total electron content (TEC) observations into a theoretical numerical model of the thermosphere and ionosphere (NCAR thermosphere-ionosphere-electrodynamics general circulation model) during the 26 September 2011 geomagnetic storm period. Effects of various assimilation-forecast cycle lengths: 60, 30, and 10 min on the ionospheric forecast are examined by using the global root-mean-squared observation-minus-forecast (OmF) TEC residuals. Substantial reduction in the global OmF for the 10 min assimilation-forecast cycling suggests that a rapid cycling ionospheric data assimilation system can greatly improve the quality of the model forecast during geomagnetic storm conditions. Furthermore, updating the thermospheric state variables in the coupled thermosphere-ionosphere forecast model in the assimilation step is an important factor in improving the trajectory of model forecasting. The shorter assimilation-forecast cycling (10 min in this paper) helps to restrain unrealistic model error growth during the forecast step due to the imbalance among model state variables resulting from an inadequate state update, which in turn leads to a greater forecast accuracy.

Chen, C.; Lin, C.; Matsuo, T.; Chen, W.; Lee, I.; Liu, J; Lin, J.; Hsu, C.;

Published by: Journal of Geophysical Research: Space Physics Published on: 05/2016

YEAR: 2016 DOI: 10.1002/2015JA021787

Ionospheric responses to geomagnetic storms during 2015-2016 at longitude 120° E in China

Chen, Yanhong; Tianjiao, Yuan; Hua, Shen; Liu, Siqing; Wengeng, Huang; Gong, Jiancun;

Published by: Published on:

YEAR: 2016 DOI:

2015

Characteristics and mechanisms of the annual asymmetry of thermospheric mass density

In this paper, globally-averaged, thermospheric total mass density, derived from the orbits of \~5000 objects at 250, 400, and 550 km that were tracked from 1967 to 2006, has been used to quantitatively study the annual asymmetry of thermospheric mass density and its mechanism(s). The results show that thermospheric mass density had a significant annual asymmetry, which changed from year to year. The annual asymmetry at the three altitudes varied synchronously and its absolute value increased with altitudes. The results suggest that there is an annual asymmetry in solar EUV radiation that is caused by the difference in the Sun-Earth distance between the two solstices and the random variation of solar activity within a year. This change in radiation results in an annual change in the thermospheric temperature and thus the scale height of the neutral gas, and is the main cause of the annual asymmetry of thermospheric mass density. The annual asymmetry of mass density increases with altitude because of the accumulating effect of the changes in neutral temperature and scale height in the vertical direction.

Ma, RuiPing; Xu, JiYao; Wang, Wenbin; Chen, GuangMing; Yuan, Wei; Lei, Jiuhou; Burns, Alan; Jiang, Guoying;

Published by: Science China Earth Sciences Published on: 04/2015

YEAR: 2015 DOI: 10.1007/s11430-014-5020-3

annual asymmetry of thermospheric mass density; solar EUV radiation; Sun-Earth distance

Ionospheric response to CIR-induced recurrent geomagnetic activity during the declining phase of solar cycle 23

This paper presents an epoch analysis of global ionosphere responses to recurrent geomagnetic activity during 79 corotating interaction region (CIR) events from 2004 to 2009. The data used were GPS total electron content (TEC) data from the Madrigal Database at the Massachusetts Institute of Technology Haystack Observatory and the electron density (Ne) data obtained from CHAllenging Minisatellite Payload (CHAMP) observations. The results show that global ionosphere responses to CIR events have some common features. In high and middle latitudes, the total electron content (TEC) showed a significant positive response (increased electron densities) in the first epoch day. A negative TEC response occurred at high latitudes of the American sector following the positive response. The CHAMP Ne showed a daytime positive response in all latitudes and a nighttime negative response in the subauroral region. These negative TEC and Ne responses were found to be related to thermospheric composition (O/N₂) changes during the storms. At all latitudes, the maximum of the TEC positive effect always occurred at 2\textendash6 h after the CIR starting during local daytime and 10\textendash18 h later for the CIR onset during local nighttime. Case studies indicate that the TEC and Ne positive response had a strong dependence on the southward component (Bz) of the interplanetary magnetic field and solar wind speed. This suggests that penetration electric fields that were associated with changes in solar winds might play a significant role in the positive ionospheric response to storms. During the recovery time of the CIR-produced geomagnetic activity, the TEC positive disturbance at low latitudes sometimes could last for 2\textendash4 days, whereas at middle to high latitudes the disturbance lasted only for 1 day in most cases. A comparison of the ionospheric responses between the American, European and Asian sectors shows that the ionosphere response in the North American sector was stronger than that in the other two regions. The response of f_oF₂ to the CIR events in middle to high latitudes showed a negative response for 2\textendash3 days after the first epoch day. This is different from the response of TEC, which was mostly positive during the same period of time.

Chen, Yanhong; Wang, Wenbin; Burns, Alan; Liu, Siqing; Gong, Jiancun; Yue, Xinan; Jiang, Guoying; Coster, Anthea;

Published by: Journal of Geophysical Research: Space Physics Published on: 02/2015

YEAR: 2015 DOI: 10.1002/2014JA020657

CIR events; epoch study; Ionospheric response; recurrent geomagnetic activity

The long-duration positive storm effects in the equatorial ionosphere over Jicamarca

The long-duration positive storm (LPS) in the equatorial regions is relatively poorly understood. In this report, we conducted a statistical analysis of the LPS effects in the equatorial ionosphere over Jicamarca (12.0\textdegreeS, 283.2\textdegreeE) in 1998\textendash2010. There are 250 geomagnetic storms (minimum Dst \< -50 nT) in 1998\textendash2010, but the ionosonde observations at Jicamarca are available only for 204 storms. A total of 46 LPSs are identified in terms of the criterion that the storm time relative deviation of peak density of F₂ layer (N_mF₂) exceeds 25\% for more than 6 h. A salient feature is that the occurrence of LPSs tends to decay approximately exponentially on the following days after the main phase of geomagnetic storms. The ratios of the number of equatorial LPSs to that of geomagnetic storms have no obvious dependence on season and solar activity. During the daytime LPSs, the disturbed zonal electric field is mostly westward, as indicated from the geomagnetic field changes in the equatorial American region. For the nighttime LPSs, the significant uplifting of F₂ layer caused by an eastward electric field is the most important feature. Therefore, the disturbed electric field should play an essential role in forming the equatorial LPSs.

Kuai, Jiawei; Liu, Libo; Liu, Jing; Zhao, Biqiang; Chen, Yiding; Le, Huijun; Wan, Weixing;

Published by: Journal of Geophysical Research: Space Physics Published on: 02/2015

YEAR: 2015 DOI: 10.1002/2014JA020552

ionospheric long-duration positive storms

2014

A study of GPS ionospheric scintillations observed at Shenzhen

Ionospheric scintillation variations are studied using GPS measurements at the low latitude station of Shenzhen (22.59\textdegreeN,\ 113.97\textdegreeE), situated under the northern crest of the equatorial anomaly region, from the Chinese Meridian Project. The results are presented for data collected during the current phase of rising solar activity (low to high solar activity) from December 2010 to April 2014. The results show that GPS scintillation events were largely a nighttime phenomenon during the whole observation period. Scintillation events mainly occurred along the inner edge of the northern crest of the equatorial anomaly in China. The occurrence of scintillations in different sectors of the sky was also investigated, and the results revealed that it is more likely for the scintillations to be observed in the west sector of the sky above Shenzhen. During the present period of study, a total number of 512 total electron content (TEC) depletions and 460 lock loss events were observed. In addition, both of these events are likely to increase during periods of high solar activity, especially because the strong scintillations are often simultaneously accompanied by TEC depletions and lock losses by GPS receivers.

Huang, Linfeng; Wang, Jinsong; Jiang, Yong; Chen, Zhou; Zhao, Kai;

Published by: Advances in Space Research Published on: 12/2014

YEAR: 2014 DOI: 10.1016/j.asr.2014.08.023

GPS; Ionospheric scintillation; Scintillation event

Meteor radar wind over Chung-Li (24.9 N, 121 E), Taiwan, for the period 10--25 November 2012 which includes Leonid meteor shower: Comparison with empirical model and satellite measurements

The neutral winds in the mesosphere and lower thermosphere (MLT) region are measured by a newly installed meteor trail detection system (or meteor radar) at Chung-Li, Taiwan, for the period 10\textendash25 November 2012, which includes the Leonid meteor shower period. In this study, we use the 3 m field-aligned plasma irregularities in the sporadic E (E_s) region in combination with the International Geomagnetic Reference Field model to calibrate the system phase biases such that the true positions of the meteor trails can be correctly determined with interferometry technique. The horizontal wind velocities estimated from the radial velocities of the meteor trails and their locations by using a least squares method show that the diurnal tide dominates the variation of the MLT neutral wind with time over Chung-Li, which is in good agreement with the horizontal wind model (HWM07) prediction. However, harmonic analysis reveals that the amplitudes of the mean wind, diurnal, and semidiurnal tides of the radar-measured winds in height range 82\textendash100 km are systematically larger than those of the model-predicted winds by up to a factor of 3. A comparison shows that the overall pattern of the height-local time distribution of the composite radar-measured meteor wind is, in general, consistent with that of the TIMED Doppler Interferometer-observed wind, which is dominated by a diurnal oscillation with downward phase progression at a rate of about 1.3 km/h. The occurrences of the E_s layers retrieved from fluctuations of the amplitude and excess phase of the GPS signal received by the FORMOSAT-3/COSMIC satellites during the GPS radio occultation (RO) process are compared with the shear zones of the radar-measured meteor wind and HWM07 wind. The result shows that almost all of the RO-retrieved E_s layers occur within the wind shear zones that favor the E_s layer formation based on the wind shear theory, suggesting that the primary physical process responsible for the E_s layer events retrieved from the scintillations of the GPS RO signal is very likely the plasma convergence effect of the neutral wind shear.

Su, C.; Chen, H.; Chu, Y.; Chung, M.; Kuong, R.; Lin, T.; Tzeng, K.; Wang, C; Wu, K.; Yang, K.;

Published by: Radio Science Published on: 08/2014

YEAR: 2014 DOI: 10.1002/2013RS005273

HWM07; radar meteor wind; tide

The responses of ionospheric topside diffusive fluxes to two geomagnetic storms in October 2002

O⁺ field-aligned ambipolar diffusive velocities V_d and fluxes Ф_d in the topside ionosphere have been calculated from the observed profiles of electron density, ion, and electron temperatures during a 30 day incoherent scatter radar experiment conducted at Millstone Hill (288.5\textdegreeE, 42.6\textdegreeN) from 4 October to 4 November 2002. Two geomagnetic storms took place during this period. During the negative phases (depleted electron densities) of these two storms, the magnitudes of the daytime upward V_d and Ф_d were less than their averaged quiet time values. Whereas at nighttime, the downward V_d and Ф_d were sometimes larger than the averaged quiet time values. The variations in diffusive velocity and flux during the storm main and recovery phases were caused by changes in the ionospheric scale height or the shapes of ionospheric density profiles. The negative storm effect further reduced daytime diffusive flux. During these two storms, positive ionosphere phases (enhanced electron densities) were also observed. The diffusive velocity was much smaller during the period of positive storm effect, which led to a smaller diffusive flux than the quiet time one, although electron density was higher. It appears that storm time variations in diffusive velocity were more the results of storm time changes in the plasma vertical profile, rather than the cause of these plasma density changes.

Chen, Guang-Ming; Xu, JiYao; Wang, Wenbin; Lei, Jiuhou; Zhang, Shun-Rong;

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

YEAR: 2014 DOI: 10.1002/2014JA020013

diffusion; geomagnetic storm; scale height; topside ionosphere

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: 01/2014

YEAR: 2014 DOI: 10.1364/AO.53.000565

Spherical cap harmonic analysis of the Arctic ionospheric TEC for one solar cycle

Precise knowledge of the Arctic ionosphere total electron content (TEC) and its variations has scientific relevance due to the unique characteristics of the polar ionosphere. Understanding the Arctic TEC is also important for precise positioning and navigation in the Arctic. This study utilized the spherical cap harmonic analysis (SCHA) method to map the Arctic TEC for the most recent solar cycle from 2000 to 2013 and analyzed the distributions and variations of the Arctic TEC at different temporal and spatial scales. Even with different ionosphere conditions during the solar cycle, the results showed that the existing International Global Navigation Satellite Systems Service stations are sufficient for mapping the Arctic TEC. The SCHA method provides adequate accuracy and resolution to analyze the spatiotemporal distributions and variations of the Arctic TEC under different ionosphere conditions and to track ionization patches in this polar region (e.g., the ionization event of 26 September 2011). The results derived from the SCHA model were compared to direct observations using the Super Dual Auroral Radar Network radar. The SCHA method is able to predict the TEC in the long and short terms. This paper presented a long-term prediction with a relative uncertainty of 75\% for a latency of one solar cycle and a short-term prediction with errors of \textpm2.2 total electron content units (TECUs, 1 TECU = 10¹⁶ el m^-2), \textpm3.8 TECU, and \textpm4.8 TECU for a latency of 1, 2, and 3 days, respectively. The SCHA is an effective method for mapping, predicting, and analyzing the Arctic TEC.

Liu, Jingbin; Chen, Ruizhi; An, Jiachun; Wang, Zemin; Hyyppa, Juha;

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

YEAR: 2014 DOI: 10.1002/2013JA019501

Arctic navigation; ionosphere mapping and prediction; polar ionosphere; regional ionosphere model; spherical cap harmonic analysis

Auroral hemispheric power during geomagnetic storms driven by different interplanetary disturbances

Although it has been a long time since the beginning of research on the auroral hemispheric power (HP), less has been done on the differences of HP among storms driven by different

Chen, Xi; FU, Sui-Yan; Zheng, Ling; YANG, Li-Ping; CUI, Yan-Bo;

Published by: Chinese Journal of Geophysics Published on:

YEAR: 2014 DOI: 10.6038/cjg20141130

Auroral all-sky camera calibration

A two-step procedure to calibrate the spectral sensitivity to visible light of auroral all-sky cameras is outlined. Center pixel response is obtained by the use of a Lambertian surface and a

Sigernes, Fred; Holmen, SE; Biles, D; Bj\orklund, H; Chen, X; Dyrland, M; Lorentzen, DA; Baddeley, L; Trondsen, T; Brändström, U; , others;

Published by: Geoscientific Instrumentation, Methods and Data Systems Published on:

YEAR: 2014 DOI: 10.5194/gi-3-241-2014

2013

Ionospheric symmetry caused by geomagnetic declination over North America

We describe variations in total electron content (TEC) in the North American sector exhibiting pronounced longitudinal progression and symmetry with respect to zero magnetic declination. Patterns were uncovered by applying an empirical orthogonal function (EOF) decomposition procedure to a 12 year ground-based American longitude sector GPS TEC data set. The first EOF mode describes overall average TEC, while the strong influence of geomagnetic declination on the midlatitude ionosphere is found in the second EOF mode (or the second most significant component). We find a high degree of correlation between spatial variations in the second EOF mode and vertical drifts driven by thermospheric zonal winds, along with well-organized temporal variation. Results strongly suggest a causative mechanism involving varying declination with longitude along with varying zonal wind climatology with local time, season, and solar cycle. This study highlights the efficiency and key role played by the geomagnetic field effect in influencing mesoscale ionospheric structures over a broad midlatitude range.

Zhang, Shun-Rong; Chen, Ziwei; Coster, Anthea; Erickson, Philip; Foster, John;

Published by: Geophysical Research Letters Published on: 10/2014

YEAR: 2013 DOI: 10.1002/grl.v40.2010.1002/2013GL057933

geomagnetic field; midlatitude ionosphere; thermospheric winds; total electron content

Thermospheric tidal effects on the ionospheric midlatitude summer nighttime anomaly using SAMI3 and TIEGCM

This paper is the first study to employ a three-dimensional physics-based ionosphere model, SAMI3, coupled with the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) and Global Scale Wave Model to simulate the mesospheric and lower thermospheric tidal effects on the development of midlatitude summer nighttime anomaly (MSNA). Using this coupled model, the diurnal variation of MSNA electron densities at 300 km altitude is simulated on both June solstice (day of year (DOY) 167) and December solstice (DOY 350) in 2007. Results show successful reproduction of the southern hemisphere MSNA structure including the eastward drift feature of the southern MSNA, which is not reproduced by the default SAMI3 runs using the neutral winds provided by the empirical Horizontal Wind Model 93 neutral wind model. A linear least squares algorithm for extracting tidal components is utilized to examine the major tidal component affecting the variation of southern MSNA. Results show that the standing diurnal oscillation component dominates the vertical neutral wind manifesting as a diurnal eastward wave-1 drift of the southern MSNA in the local time frame. We also find that the stationary planetary wave-1 component of vertical neutral wind can cause diurnal variation of the summer nighttime electron density enhancement around the midlatitude ionosphere.

Chen, C.; Lin, C.; Chang, L.; Huba, J.; Lin, J.; Saito, A.; Liu, J;

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

YEAR: 2013 DOI: 10.1002/jgra.50340

MSNA; SAMI3; tidal effect; TIEGCM

Solar cycle dependence of the seasonal variation of auroral hemispheric power

Although much has been done on the hemispheric asymmetry (or seasonal variations) of auroral hemispheric power (HP), the dependence of HP hemispheric asymmetry on solar cycle has not yet been studied. We have analyzed data during 1979\textendash2010 and investigated the dependence of HP hemispheric asymmetry/seasonal variation for the whole solar cycle. Here we show that (1) the hemispheric asymmetry of HP is positively correlated to the value of solar F10.7 with some time delay; (2) it is closely related to the coupling function between the solar wind and magnetosphere; and (3) the winter hemisphere receives more auroral power than the summer hemisphere for K _p\~0 to 6. The statistic results can be partly understood in the framework of the ionospheric conductivity feedback model. The similarity and differences between our results and previous results are discussed in the paper.

Zheng, Ling; Fu, SuiYan; Zong, QuiGang; Parks, George; Wang, Chi; Chen, Xi;

Published by: Chinese Science Bulletin Published on: 02/2013

YEAR: 2013 DOI: 10.1007/s11434-012-5378-6

auroral power; coupling function; hemispheric asymmetry; precipitation; solar cycle

2012

Longitudinal distribution of O2 nightglow brightness observed by TIEMD/SABER satellite

Gao, Hong; Nee, JanBai; Chen, GuangMing;

Published by: Science China Technological Sciences Published on: Jan-05-2012

YEAR: 2012 DOI: 10.1007/s11431-012-4802-0

Equinoctial asymmetry in solar activity variations of NmF2 and TEC

Chen, Y.; Liu, L.; Wan, W.; Ren, Z.;

Published by: Annales Geophysicae Published on: Jan-01-2012

YEAR: 2012 DOI: 10.5194/angeo-30-613-2012

Bright polar mesospheric clouds formed by main engine exhaust from the space shuttle's final launch

Stevens, Michael; Lossow, Stefan; Fiedler, Jens; Baumgarten, Gerd; übken, Franz-Josef; Hallgren, Kristofer; Hartogh, Paul; Randall, Cora; Lumpe, Jerry; Bailey, Scott; Niciejewski, R.; Meier, R.; Plane, John; Kochenash, Andrew; Murtagh, Donal; Englert, Christoph;

Published by: Journal of Geophysical Research: Atmospheres Published on: Apr-10-2013

YEAR: 2012 DOI: 10.1029/2012JD017638

Ionospheric plasma caves under the equatorial ionization anomaly

This paper reports the existence of plasma caves, minima in the electron density located at 5\textendash10\textdegree to the magnetic equator, in the bottomside ionosphere based on electron densities simulations from the International Reference Ionosphere (IRI-2007) and clear evidences given by plasma density and drift measurements of the Dynamic Explorer 2 (DE 2) satellite during 1981\textendash1983. The IRI simulations suggest plasma caves as daytime features (08:00\textendash19:00 LT; length of 18,158 km in the longitudinal direction), that range from theE region up to about 300 km altitude with 10\textdegree (or 1100 km) width in the latitudinal direction. In situ measurements of the ion and electron densities probed by the DE 2 confirm the existence of the plasma caves at low altitudes of the EIA ionosphere. The unexpected downward and upward (or weakly and strongly upward) ion drifts at the magnetic equator and the two off equators seem to play an important role responsible for the plasma cave formation.

Lee, I.; Liu, J; Lin, C.; Oyama, K.-I.; Chen, C; Chen, C.;

Published by: Journal of Geophysical Research Published on: 11/2012

YEAR: 2012 DOI: 10.1029/2012JA017868

Dynamic Explorer 2; Equatorial ionization anomaly; plasma cave

Ionospheric plasma caves under the equatorial ionization anomaly

Lee, I.; Liu, J; Lin, C.; Oyama, K.-I.; Chen, C; Chen, C.;

Published by: Journal of Geophysical Research Published on: 11/2012

YEAR: 2012 DOI: 10.1029/2012JA017868

Dynamic Explorer 2; Equatorial ionization anomaly; plasma cave

Assimilation of FORMOSAT-3/COSMIC electron density profiles into a coupled thermosphere/ionosphere model using ensemble Kalman filtering

This paper presents our effort to assimilate FORMOSAT-3/COSMIC (F3/C) GPS Occultation Experiment (GOX) observations into the National Center for Atmospheric Research (NCAR) Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM) by means of ensemble Kalman filtering (EnKF). The F3/C electron density profiles (EDPs) uniformly distributed around the globe which provide an excellent opportunity to monitor the ionospheric electron density structure. The NCAR TIE-GCM simulates the Earth\textquoterights thermosphere and ionosphere by using self-consistent solutions for the coupled nonlinear equations of hydrodynamics, neutral and ion chemistry, and electrodynamics. The F3/C EDP are combined with the TIE-GCM simulations by EnKF algorithms implemented in the NCAR Data Assimilation Research Testbed (DART) open-source community facility to compute the expected value of electron density, which is \textquoteleftthe best\textquoteright estimate of the current ionospheric state. Assimilation analyses obtained with real F3/C electron density profiles are compared with independent ground-based observations as well as the F3/C profiles themselves. The comparison shows the improvement of the primary ionospheric parameters, such as NmF2 and hmF2. Nevertheless, some unrealistic signatures appearing in the results and high rejection rates of observations due to the applied outlier threshold and quality control are found in the assimilation experiments. This paper further discusses the limitations of the model and the impact of ensemble member creation approaches on the assimilation results, and proposes possible methods to avoid these problems for future work.

Lee, I.; Matsuo, T.; Richmond, A.; Liu, J; Wang, W.; Lin, C.; Anderson, J.; Chen, M.;

Published by: Journal of Geophysical Research Published on: 10/2012

YEAR: 2012 DOI: 10.1029/2012JA017700

data assimilation; ensemble Kalman filter; FORMOSAT-3/COSMIC; Ionosphere

Long-term variations of the nighttime electron density enhancement during the ionospheric midlatitude summer

This study, for the first time, presented the long-term variations of Midlatitude Summer Nighttime Anomaly (MSNA) in the two hemispheres by using 66 ground-based ionosonde observations from 1957 to 2010. MSNA is characterized by the feature of higher nighttime electron density than daytime density in the midlatitude region during local summer months. Observations from 66 ionosonde stations were used to calculate the MSNA index which is defined by the difference between nighttime and noontime NmF2 values. The MSNA occurrence is determined by positive value of the MSNA index. The global distribution map of the MSNA index shows that there are three regions of intense MSNA. Three ionosonde stations in each of active MSNA regions were chosen to study the long-term variation of MSNA covering longer than one solar cycle. One station in the southern hemisphere is AIJ6N (Argentine IS; 65.2\textdegreeS, 64.3\textdegreeW geographic) and two stations in the northern hemisphere are LN047 (Lannion; 48.8\textdegreeN, -3.4\textdegreeE geographic) and MG560 (Magadan; 60.0\textdegreeN, 151.0\textdegreeE geographic). Results show that there is a clear solar activity negative dependence of the MSNA index, high MSNA in the low solar activity condition and low MSNA in the high solar activity condition. The seasonal and solar activity variations of the MSNA index are explained by the combined effects of the vertical plasma drift induced by the neutral wind and photoionization during the nighttime.

Chen, C.; Saito, A.; Lin, C.; Liu, J;

Published by: Journal of Geophysical Research Published on: 07/2012

YEAR: 2012 DOI: 10.1029/2011JA017138

ionization-uplift effect; midlatitude summer nighttime anomaly; MSNA index

Observations of global ionospheric responses to the 2009 stratospheric sudden warming event by FORMOSAT-3/COSMIC

The global ionospheric response to a stratospheric sudden warming (SSW) is studied using three-dimensional electron density maps derived from radio occultation observations of FORMOSAT-3/COSMIC during the 2009 SSW periods. Results show that the ionospheric electron density at EIA crests exhibit a morning/early afternoon increase followed by an afternoon decrease and an evening increase, indicative of a semidiurnal component during the SSW period, which is consistent with recent studies. The latitude-altitude electron density slice maps show that the SSW related modifications of the equatorial plasma fountain interact with the existing summer-to-winter neutral winds and resulting in a north\textendashsouth asymmetry. The global ionospheric response shows a clear longitudinal dependence in the equatorial plasma fountain enhancement during morning/early afternoon, inferred from the duration of the equatorial ionization anomaly (EIA) enhancement. Following the enhancement, prominent global EIA reductions resulting from the equatorial plasma fountain weakening in the afternoon sector are seen. The ionospheric response to the 2009 SSW event is also compared with the usual seasonal variation during January\textendashFebruary 2007. Instead of showing the electron density increase in the northern hemisphere and decrease in the southern hemisphere as the usual seasonal variation does, the SSW period ionosphere shows prominent global electron density reductions in the afternoon period during the 2009 SSW event.

Lin, C.; Lin, J.; Chang, L.; Liu, J; Chen, C.; Chen, W.; Huang, H.; Liu, C.;

Published by: Journal of Geophysical Research Published on: 06/2012

YEAR: 2012 DOI: 10.1029/2011JA017230

FORMOSAT-3/COSMIC; ionospheric responses to stratospheric sudden warming

Observations of global ionospheric responses to the 2009 stratospheric sudden warming event by FORMOSAT-3/COSMIC

Lin, C.; Lin, J.; Chang, L.; Liu, J; Chen, C.; Chen, W.; Huang, H.; Liu, C.;

Published by: Journal of Geophysical Research Published on: 06/2012

YEAR: 2012 DOI: 10.1029/2011JA017230

FORMOSAT-3/COSMIC; ionospheric responses to stratospheric sudden warming

2011

Global distributions of OH and O2 (1.27 μm) nightglow emissions observed by TIMED satellite

Gao, Hong; Xu, JiYao; Chen, GuangMing; Yuan, Wei; Beletsky, A.;

Published by: Science China Technological Sciences Published on: Jan-02-2011

YEAR: 2011 DOI: 10.1007/s11431-010-4236-5

The O I 135.6 nm airglow observations of the midlatitude summer nighttime anomaly by TIMED/GUVI

Hsu, M.; Lin, C.; Hsu, R.; Liu, J; Paxton, L.; Su, H.; Tsai, H.; Rajesh, P.; Chen, C.;

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

YEAR: 2011 DOI: 10.1029/2010JA016150

The production of Titan\textquoterights ultraviolet nitrogen airglow

Stevens, Michael; Gustin, Jacques; Ajello, Joseph; Evans, Scott; Meier, R.; Kochenash, Andrew; Stephan, Andrew; Stewart, Ian; Esposito, Larry; McClintock, William; Holsclaw, Greg; Bradley, Todd; Lewis, B.; Heays, A.;

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

YEAR: 2011 DOI: 10.1029/2010JA016284

The OI 135.6 nm airglow observations of the midlatitude summer nighttime anomaly by TIMED/GUVI

Hsu, ML; Lin, CH; Hsu, RR; Liu, JY; Paxton, LJ; Su, HT; Tsai, HF; Rajesh, PK; Chen, CH;

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

YEAR: 2011 DOI:

Radio tomography imaging based on navigation systems

Methods of radio tomography (RT) based on the low- and high-orbital navigational systems and radio occultation data are considered. Examples of RT imaging of the ionosphere in

Kunitsyn, VE; Tereshchenko, VE; Andreeva, ES; Nesterov, IA; Nazarenko, MO;

Published by: . Published on:

YEAR: 2011 DOI: 10.1109/URSIGASS.2011.6051019

Global distributions of OH and O2 (1.27 $\mu$m) nightglow emissions observed by TIMED satellite

In order to investigate the global distributions of temporal variations of OH and O 2 nightglow emissions, we statistically analyzed their variations with altitude, local time, and season

Gao, Hong; Xu, JiYao; Chen, GuangMing; Yuan, Wei; Beletsky, AB;

Published by: Science China Technological Sciences Published on:

YEAR: 2011 DOI: https://doi.org/10.1007/s11431-010-4236-5

Radio tomography imaging based on navigation systems

Methods of radio tomography (RT) based on the low- and high-orbital navigational systems and radio occultation data are considered. Examples of RT imaging of the ionosphere in

Kunitsyn, VE; Tereshchenko, VE; Andreeva, ES; Nesterov, IA; Nazarenko, MO;

Published by: Published on:

YEAR: 2011 DOI: 10.1109/URSIGASS.2011.6051019

2010

Dayside ionospheric response to recurrent geomagnetic activity during the extreme solar minimum of 2008

Ram, Tulasi; Lei, J.; Su, S.-Y.; Liu, C.; Lin, C.; Chen, W.;

Published by: Geophysical Research Letters Published on: Jan-01-2010

YEAR: 2010 DOI: 10.1029/2009GL041038

Integrating the Sun-Earth System for the Operational Environment (ISES-OE)

Lean, J.; Huba, J.; McDonald, S.; Slinker, S.; Drob, D.; Emmert, J.; Meier, R.; Picone, J.; Joyce, G.; Krall, J.; Stephan, A.; Roach, K.; Knight, H.; Plunkett, S.; Wu, C.-C.; Wood, B.; Wang, Y.-M.; Howard, R.; Chen, J.; Bernhardt, P.; Fedder, J.;

Published by: Published on:

YEAR: 2010 DOI:

2009

The Ionospheric Mid-Latitude Summer Nighttime Anomaly

This paper presents monthly variations of the mid-latitude summer nighttime anomaly (MSNA) of the ionosphere for the first time by using global observations of the FORMOSAT-3/COSMIC (F3/C), NASA TIMED-GUVI, ground-based radars and GPS receiver network. The MSNA is characterized by greater nighttime (19:00 LT - 24:00 LT, or period of larger solar zenith angles) ionospheric electron density than that during daytime (08:00 - 18:00 LT, or period of smaller solar zenith angles) at middle latitudes during solstices. The anomaly shown in the southern hemisphere during December solstice was previously known as the Weddell Sea Anomaly (WSA) occurring around the Antarctica and the nearby Pacific Ocean, while a WSA-like electron density structure also occurs in the northern hemisphere around June solstice. This study demonstrates that the anomalies occurred in both the northern and southern hemispheres share similar character of greater nighttime density. Moreover, the latitude-altitude cross-section plots of the electron density structure show very similar time-varying electron density evolutions of the MSNA. In both hemispheres, the anomalies with similar electron density characteristics and variations caused by the similar mechanism prompts us to name this phenomenon the mid-latitude summer nighttime anomaly.

Lin, C; Chen, C; Hsu, M; Liu, CH; Liu, JG; Burns, AG; Wang, W;

Published by: Published on:

YEAR: 2009 DOI:

Global Ionospheric Structure Imaged by FORMOSAT-3/COSMIC: Early Results.

A new era of study ing the ion o spheric space weather ef fects has come af ter launch of the in no va tive sat el lite con stel la tion, named as Formosa Sat el lite 3 or Con stel la tion Ob

Lin, Chien-Hung; Liu, Jann-Yenq; Hsiao, Chun-Chieh; Liu, Chao-Han; Cheng, Chio-Zong; Chang, Po-Ya; Tsai, Ho-Fang; Fang, Tzu-Wei; Chen, Chia-Hung; Hsu, Mei-Lan;

Published by: Terrestrial, Atmospheric \& Oceanic Sciences Published on:

YEAR: 2009 DOI:

Global Ionospheric Structure Imaged by FORMOSAT-3/COSMIC: Early Results.

A new era of study ing the ion o spheric space weather ef fects has come af ter launch of the in no va tive sat el lite con stel la tion, named as Formosa Sat el lite 3 or Con stel la tion Ob

Lin, Chien-Hung; Liu, Jann-Yenq; Hsiao, Chun-Chieh; Liu, Chao-Han; Cheng, Chio-Zong; Chang, Po-Ya; Tsai, Ho-Fang; Fang, Tzu-Wei; Chen, Chia-Hung; Hsu, Mei-Lan;

Published by: Terrestrial, Atmospheric \& Oceanic Sciences Published on:

YEAR: 2009 DOI:

2008

Satellite and ground-based observations of auroral energy deposition and the effects on thermospheric composition during large geomagnetic storms: 1. Great geomagnetic storm of 20 November 2003

Hecht, JH; Mulligan, T; Strickland, DJ; Kochenash, AJ; Murayama, Y; Tanaka, Y-M; Evans, DS; Conde, MG; Donovan, EF; Rich, FJ; , others;

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

YEAR: 2008 DOI:

Association of Broad Dayside Auroras With the Cusp Energetic Particles

Chen, J; Wong, C;

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YEAR: 2008 DOI:

2007

Motions of the equatorial ionization anomaly crests imaged by FORMOSAT-3/COSMIC

Lin, C.; Liu, J; Fang, T.; Chang, P; Tsai, H.; Chen, C.; Hsiao, C.;

Published by: Geophysical Research Letters Published on: Jan-01-2007

YEAR: 2007 DOI: 10.1029/2007GL030741

2006

Effect of 27-day Solar Rotation on Thermospheric Density and Composition

Crowley, G; Meier, B; Tapley, B; Bettadpur, S; Cheng, M; Ries, J; Abusali, P; Paxton, L; Christensen, A;

Published by: Published on:

YEAR: 2006 DOI:

2005

Storm-time enhancement of mid-latitude ultraviolet emissions due to energetic neutral atom precipitation

DeMajistre, R.; Brandt, P.; Immel, T.; Yee, J.-H.; Dalgarno, A.; Paxton, L.; Kharchenko, V.;

Published by: Geophysical Research Letters Published on: Jan-01-2005

YEAR: 2005 DOI: 10.1029/2005GL023059

Global patterns of Joule heating in the high-latitude ionosphere

A compiled empirical global Joule heating (CEJH) model is described in this study. This model can be used to study Joule heating patterns, Joule heating power, potential drop, and polar potential size in the high-latitude ionosphere and thermosphere, and their variations with solar wind conditions, geomagnetic activities, the solar EUV radiation, and the neutral wind. It is shown that the interplanetary magnetic field (IMF) orientation and its magnitude, the solar wind speed, AL index, geomagnetic K_p index, and solar radio flux F_10.7 index are important parameters that control Joule heating patterns, Joule heating power, potential drop, and polar potential size. Other parameters, such as the solar wind number density (N_sw) and Earth\textquoterights dipole tilt, do not significantly affect these quantities. It is also shown that the neutral wind can increase or reduce the Joule heating production, and its effectiveness mainly depends on the IMF orientation and its magnitude, the solar wind speed, AL index, K_p index, and F_10.7 index. Our results indicate that for less disturbed solar wind conditions, the increase or reduction of the neutral wind contribution to the Joule heating is not significant compared to the convection Joule heating, whereas under extreme solar wind conditions, the neutral wind can significantly contribute to the Joule heating. Application of the CEJH model to the 16 July 2000 storm implies that the model outputs are basically consistent with the results from the AMIE mapping procedure. The CEJH model can be used to examine large-scale energy deposition during disturbed solar wind conditions and to study the dependence of the hemispheric Joule heating on the level of geomagnetic activities and the intensity of solar EUV radiation. This investigation enables us to predict global Joule heating patterns for other models in the high-latitude ionosphere and thermosphere in the sense of space weather forecasting.