Bibliography
|
Notice:
|
Found 114 entries in the Bibliography.
Showing entries from 51 through 100
| 2016 |
|
With the development of modern technology, especially the development of information technology at high speed, the ultraviolet early warning system plays an increasingly important Wang, Wen-cong; Jin, Dong-dong; Shao, Fei; Hu, Hui-jun; Shi, Yu-feng; Song, Juan; Zhang, Yu-tu; Yong, Liu; Published by: Published on: YEAR: 2016 DOI: 10.1117/12.2236440 |
|
Conde, Mark; Bristow, William; Hampton, Donald; Kosch, Michael; Ishii, Mamoru; Paxton, Larry; Davies, Theo; Published by: Published on: |
| 2015 |
|
The characteristics of the F2 layer parameters NmF2 and hmF2 over Dibrugarh (27.5\textdegree N, 95\textdegree E, 17\textdegree N geomagnetic, 43\textdegree dip) measured by a Canadian Advanced Digital Ionosonde (CADI) for the period of August 2010 to July 2014 are reported for the first time from this low mid-latitude station lying within the daytime peak of the longitudinal wave number 4 structure of equatorial anomaly (EIA) around the northern edge of anomaly crest. Equinoctial asymmetry is clearly observed at all solar activity levels whereas the midday winter anomaly is observed only during high solar activity years and disappears during the temporary dip in solar activity in 2013 but forenoon winter anomaly can be observed even at moderate solar activity. The NmF2/hmF2 variations over Dibrugarh are compared with that of Okinawa (26.5\textdegree N, 127\textdegree E, 17\textdegree N geomagnetic), and the eastward propagation speed of the wave number 4 longitudinal structure from 95\textdegree E to 127\textdegree E is estimated. The speed is found to be close to the theoretical speed of the wave number 4 (WN4) structure. The correlation of daily NmF2 over Dibrugarh and Okinawa with solar activity exhibits diurnal and seasonal variations. The highest correlation in daytime is observed during the forenoon hours in equinox. The correlation of daily NmF2 (linear or non-linear) with solar activity exhibits diurnal variation. A tendency for amplification with solar activity is observed in the forenoon and late evening period of March equinox and the postsunset period of December solstice. NmF2 saturation effect is observed only in the midday period of equinox. Non-linear variation of neutral composition at higher altitudes and variation of recombination rates with solar activity via temperature dependence may be related to the non-linear trend. The noon time maximum NmF2 over Dibrugarh exhibits better correlation with equatorial electrojet (EEJ) than with solar activity and, therefore, new low-latitude NmF2 index is proposed taking both solar activity and EEJ strength into account. Kalita, Bitap; Bhuyan, Pradip; Yoshikawa, Akimasa; Published by: Earth, Planets and Space Published on: Jan-12-2015 YEAR: 2015 DOI: 10.1186/s40623-015-0355-3 |
|
Climatology of equatorial plasma bubble observed by MyRTKnet over the years 2008--2013 Malaysia Real-Time Kinematics GNSS Network (MyRTKnet) which consists of 78 GPS receivers was used to investigate the occurrence of equatorial plasma bubble (EPB) along 96\textdegreeE-120\textdegreeE longitude. In this study, we present the monthly occurrence rate of EPB along the geographical longitudes of 96\textdegreeE-120\textdegreeE for a half of solar cycle period (2008-2013). A 2D map of rate of TEC change index (ROTI) projected at 300 km altitude was derived from the signal paths between GPS satellites and the receivers. A ROTI keogram for one day period was obtained from the east-west cross section of the 2D ROTI maps at 4\textdegreeN for every 5 min. The occurrence day of EPB was determined from the keogram by the existence of ROTI larger than 0.1 TECU/min within the 96\textdegreeE-120\textdegreeE longitude. The results show that the occurrence of EPB along the 96\textdegreeE-120\textdegreeE has maximum during equinoctial months and is consistent with previous studies. The occurrence rate of EPB during equinoctial months shows similar characteristics in low and high solar activity due to the broad observational coverage of the MyRTKnet. In contrast, the occurrence rate of EPB during solstice months shows significant relation with solar activity. Solstice months recorded high occurrence rate of EPB in high solar activity that might be attributed to post-midnight irregularities. Buhari, S.; Abdullah, M.; Yokoyama, T.; Hasbi, A.; Otsuka, Y.; Nishioka, M.; Bahari, S.A.; Tsugawa, T.; Published by: Published on: 08/2015 YEAR: 2015 DOI: 10.1109/IconSpace.2015.7283752 |
|
Transpolar arc observation after solar wind entry into the high-latitude magnetosphere Recently, Cluster observations have revealed the presence of new regions of solar wind plasma entry at the high-latitude magnetospheric lobes tailward of the cusp region, mostly during periods of northward interplanetary magnetic field. In this study, observations from the Global Ultraviolet Imager (GUVI) experiment on board the TIMED spacecraft and Wideband Imaging Camera imager on board the IMAGE satellite are used to investigate a possible link between solar wind entry and the formation of transpolar arcs in the polar cap. We focus on a case when transpolar arc formation was observed twice right after the two solar wind entry events were detected by the Cluster spacecraft. In addition, GUVI and IMAGE observations show a simultaneous occurrence of auroral activity at low and high latitudes after the second entry event, possibly indicating a two-part structure of the continuous band of the transpolar arc. Mailyan, B.; Shi, Q.; Kullen, A.; Maggiolo, R.; Zhang, Y.; Fear, R.; Zong, Q.-G.; Fu, S; Gou, X.; Cao, X.; Yao, Z.; Sun, W.; Wei, Y.; Pu, Z; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2015 YEAR: 2015 DOI: 10.1002/2014JA020912 magnetosphere-ionosphere coupling; transpolar arcs; in situ measurements |
|
We report, for the first time, an auroral undulation event on 1 May 2013 observed by an all-sky imager (ASI) at Athabasca (L = 4.6), Canada, for which in situ field and particle measurements in the conjugate magnetosphere were available from a Van Allen Probes spacecraft. The ASI observed a train of auroral undulation structures emerging spontaneously in the pre-midnight subauroral ionosphere, during the growth phase of a substorm. The undulations had an azimuthal wavelength of ~180 km and propagated westward at a speed of 3\textendash4 km s-1. The successive passage over an observing point yielded quasi-periodic oscillations in diffuse auroral emissions with a period of ~40 s. The azimuthal wave number m of the auroral luminosity oscillations was found to be m ~ -103. During the event the spacecraft \textendash being on tailward stretched field lines ~0.5 RE outside the plasmapause that mapped into the ionosphere conjugate to the auroral undulations \textendash encountered intense poloidal ULF oscillations in the magnetic and electric fields. We identify the field oscillations to be the second harmonic mode along the magnetic field line through comparisons of the observed wave properties with theoretical predictions. The field oscillations were accompanied by oscillations in proton and electron fluxes. Most interestingly, both field and particle oscillations at the spacecraft had one-to-one association with the auroral luminosity oscillations around its footprint. Our findings strongly suggest that this auroral undulation event is closely linked to the generation of second harmonic poloidal waves Motoba, T.; Takahashi, K.; Ukhorskiy, A.; Gkioulidou, M.; Mitchell, D.; Lanzerotti, L.; Korotova, G.; Donovan, E.; Wygant, J.; Kletzing, C.; Kurth, W.; Blake, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 02/2015 YEAR: 2015 DOI: 10.1002/2014JA020863 |
|
Far ultraviolet nighttime ionospheric photometer Far Ultraviolet Nighttime Ionopsheric Photometer (FNIP) is a newly-designed instrument for low earth orbit missions, observing the earth night airglow nadir at OI 135.6\ nm emission produced by ionospheric O++e recombination and receiving the horizontal information on nighttime ionosphere with a spatial resolution of about 1.6o\texttimes3.8o. This simple, highly robust instrument excludes OI 130.4 nm emission and Herzberg oxygen bands with lower power and approximately achieves a sensitivity of about 400\ counts/s/Rayleigh at 135.6\ nm with stray light less than\ 2\ \%. Some tests of the instrument have been conducted and the results will be discussed in the end. Fu, Liping; Peng, Ruyi; Shi, Entao; Peng, Jilong; Wang, Tianfang; Jiang, Fang; Jia, Nan; Li, Xiaoyin; Wang, YongMei; Published by: Astrophysics and Space Science Published on: 01/2015 YEAR: 2015 DOI: 10.1007/s10509-014-2139-9 F2 electron density distribution; FUV optical sensing remote; High sensitivity; Ionosphere; Payload |
|
Isolated proton auroras and Pc1/EMIC waves at subauroral latitudes GUVI offered a variety of auroral images from each spacecraft polar pass, using a mirror scanning transverse to the spacecraft ground track. The N2 long Lyman− Birge− Hopfield (LBHS Sakaguchi, Kaori; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Connors, Martin; Published by: Auroral dynamics and space weather Published on: |
|
Isolated proton auroras and Pc1/EMIC waves at subauroral latitudes GUVI offered a variety of auroral images from each spacecraft polar pass, using a mirror scanning transverse to the spacecraft ground track. The N2 long Lyman− Birge− Hopfield (LBHS Sakaguchi, Kaori; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Connors, Martin; Published by: Auroral dynamics and space weather Published on: |
|
NmF2 and hmF2 measurements at 95 E and 127 E around the EIA northern crest during 2010—2014 Non-linear variation of neutral composition at higher altitudes and variation of recombination rates with solar activity via temperature dependence may be related to the non-linear trend. The noon time maximum NmF2 over Dibrugarh exhibits better correlation with equatorial electrojet (EEJ) than with solar activity and, therefore, new low-latitude NmF2 index is proposed taking both solar activity and EEJ strength into account. Kalita, Bitap; Bhuyan, Pradip; Yoshikawa, Akimasa; Published by: Earth, Planets and Space Published on: YEAR: 2015 DOI: 10.1186/s40623-015-0355-3 |
|
Community-wide model validation study for systematic assessment of ionosphere models Shim, Ja; Kuznetsova, Maria; Rastaetter, Lutz; Bilitza, Dieter; Bingham, Suzy; Bust, Gary; Calfas, Roy; Codrescu, Mihail; Coster, Anthea; Crowley, Geoff; , others; Published by: Published on: |
| 2014 |
|
High-density GPS receivers located in Southeast Asia (SEA) were utilized to study the two-dimensional structure of ionospheric plasma irregularities in the equatorial region. The longitudinal and latitudinal variations of tens of kilometer-scale irregularities associated with equatorial plasma bubbles (EPBs) were investigated using two-dimensional maps of the rate of total electron content change index (ROTI) from 127 GPS receivers with an average spacing of about 50\textendash100 km. The longitudinal variations of the two-dimensional maps of GPS ROTI measurement on 5 April 2011 revealed that 16 striations of EPBs were generated continuously around the passage of the solar terminator. The separation distance between the subsequent onset locations varied from 100 to 550 km with 10 min intervals. The lifetimes of the EPBs observed by GPS ROTI measurement were between 50 min and over 7 h. The EPBs propagated 440\textendash3000 km toward the east with velocities of 83\textendash162 m s-1. The longitudinal variations of EPBs by GPS ROTI keogram coincided with the depletions of 630 nm emission observed using the airglow imager. Six EPBs were observed by GPS ROTI along the meridian of Equatorial Atmosphere Radar (EAR), while only three EPBs were detected by the EAR. The high-density GPS receivers in SEA have an advantage of providing time continuous descriptions of latitudinal/longitudinal variations of EPBs with both high spatial resolution and broad geographical coverage. The spatial periodicity of the EPBs could be associated with a wavelength of the quasiperiodic structures on the bottomside of the F region which initiate the Rayleigh-Taylor instability. Buhari, S.; Abdullah, M.; Hasbi, A.; Otsuka, Y.; Yokoyama, T.; Nishioka, M.; Tsugawa, T.; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2014 YEAR: 2014 DOI: 10.1002/jgra.v119.1210.1002/2014JA020433 |
|
Multiple instrumental observations including GPS total electron content (TEC), foF2 and hmF2 from ionosondes, vertical ion drift measurements from Communication/Navigation Outage Forecasting System, magnetometer data, and far ultraviolet airglow measured by Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Global Ultraviolet Imager (TIMED/GUVI) are used to investigate the profound ionospheric disturbances at midlatitude and low latitude during the 14\textendash17 July 2012 geomagnetic storm event, which was featured by prolonged southward interplanetary geomagnetic field component for about 30 h below -10 nT. In the East Asian/Australian sector, latitudinal profile of TEC variations in the main phase were characterized by three bands of increments and separated by weak depressions in the equatorial ionospheric anomaly (EIA) crest regions, which were caused by the combined effects of disturbance dynamo electric fields (DDEF) and equatorward neutral winds. In the recovery phase, strong inhibition of EIA occurred and the summer crest of EIA disappeared on 16 July due to the combined effects of intrusion of neutral composition disturbance zone as shown by the TIMED/GUVI O/N2 measurements and long-lasting daytime westward DDEF inferred from the equatorial electrojet observations. The transit time of DDEF over the dip equator from westward to eastward is around 2200 LT. In the American longitude, the salient ionospheric disturbances in the summer hemisphere were characterized by daytime periodical intrusion of negative phase for three consecutive days in the recovery phase, preceded by storm-enhanced density plume in the initial phase. In addition, multiple short-lived prompt penetration electric fields appeared during stable southward interplanetary magnetic field (IMF) Bz in the recovery phase and were responsible for enhanced the EIA and equatorial ionospheric uplift around sunset. Liu, Jing; Liu, Libo; Nakamura, Takuji; Zhao, Biqiang; Ning, Baiqi; Yoshikawa, A.; Published by: Journal of Geophysical Research: Space Physics Published on: 09/2014 YEAR: 2014 DOI: 10.1002/jgra.v119.910.1002/2014JA020273 GUVI; Ionospheric storm; prompt penetration electric fields; TIMED |
|
A new solid-state sodium lidar installed at Ramfjordmoen, Troms\o (69.6\textdegreeN, 19.2\textdegreeE), started observations of neutral temperature together with sodium density in the mesosphere-lower thermosphere (MLT) region on 1 October 2010. The new lidar provided temperature data with a time resolution of 10 min and with good quality between \~80 and \~105 km from October 2010 to March 2011. This paper aims at introducing the new lidar with its observational results obtained over the first 6 months of observations. We succeeded in obtaining neutral temperature and sodium density data of \~255.5 h in total. In order to evaluate our observations, we compared (1) the sodium density with that published in the literature, (2) average temperature and column sodium density data with those obtained with Arctic Lidar Observatory for Middle Atmosphere Research Weber sodium lidar, and (3) the neutral temperature data with those obtained by Sounding of the Atmosphere with Broadband Emission Radiometry/Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite. For the night of 5 October 2010, we succeeded in conducting simultaneous observations of the new lidar and the European Incoherent Scatter UHF radar with the tristatic Common Program 1 (CP-1) mode. Comparisons of neutral and ion temperatures showed a good agreement at 104 km between 0050 and 0230 UT on 6 October 2010 when the electric field strength was smaller, while significant deviations (up to \~25 K) are found at 107 km. We evaluated contributions of Joule heating and electron-ion heat exchange, but derived values seem to be underestimated. Nozawa, S.; Kawahara, T.; Saito, N.; Hall, C.; Tsuda, T.; Kawabata, T.; Wada, S.; Brekke, A.; Takahashi, T.; Fujiwara, H.; Ogawa, Y.; Fujii, R.; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2014 YEAR: 2014 DOI: 10.1002/2013JA019520 |
|
The relationship between solar wind entry processes and transpolar arc formation Mailyan, Bagrat; Shi, Quanqi; Maggiolo, Romain; Zong, Qiugang; Cao, Xin; Zhang, Yongliang; Yao, Zhonghua; Fu, SuiYan; Wei, Yong; Pu, Zuyin; Published by: Published on: |
|
Ionospheric response to geomagnetic storm on July 14-17, 2012 in East Asia Romanova, Elena; Zherebtsov, Gelii; Wang, Guojun; Zolotukhina, Nina; Polekh, Nelya; Wang, Xiao; Shi, Jiankui; Published by: 40th COSPAR Scientific Assembly Published on: |
|
Polar cap arcs correlated with solar wind entry at the high latitude magnetosphere Polar cap arcs are sun-aligned aurora structures occurring during northward turnings of the Interplanetary Magnetic Field (IMF) Bz component. At the same time, a new region of solar wind entry at the high latitude magnetosphere, tailward of the cusp region, was found recently at the periods of northward IMF Bz. We propose a study to see the relationship of these entry events with the transpolar arc formation. Data of Global Ultraviolet Imager (GUVI) onboard TIMED mission is examined to see the transpolar aurora arcs during the given time periods of the solar wind entry. Initial results show that in approximately 20\% of cases transpolar arcs occur related to the solar wind entry processes. Mailyan, B.; Shi, Q.; Gou, X.; Published by: Published on: YEAR: 2014 DOI: 10.1109/URSIGASS.2014.6929926 aurora interplanetary; GUVI; magnetic fields; magnetosphere; solar wind; TIMED |
|
Liu, Jing; Liu, Libo; Nakamura, Takuji; Zhao, Biqiang; Ning, Baiqi; Yoshikawa, A; Published by: Journal of Geophysical Research: Space Physics Published on: |
|
On transpolar arc formation correlated with solar wind entry at high latitude magnetosphere Mailyan, Bagrat; Shi, Quanqi; Maggiolo, Romain; Zong, Qiugang; Fu, SuiYan; Zhang, Yongliang; Yao, Zhonghua; Sun, W; Published by: Published on: |
| 2013 |
|
The effect of the 135.6 nm emission originated from the ionosphere on the TIMED/GUVI O/N 2 ratio The column number density ratio of atomic oxygen to molecular nitrogen (O/N2\ ratio) provided by the Global Ultraviolet Imager (GUVI) onboard the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite has been used as a diagnostic of the thermospheric neutral composition. However, a recent study claimed that the GUVI O/N2\ ratio is not a pure thermospheric parameter in low latitudes during periods of low geomagnetic activity. This study quantifies the O/N2\ ratio contamination by the ionosphere using the GUVI observations and model ionosphere acquired from 31 August to 2 September 2002. During this period, the local time of the GUVI observation was near 1500 and the average\ Kp\ index was 2\textdegree. The 135.6 nm emission originated from the ionosphere is estimated using the electron density profiles provided by the Utah State University-Global Assimilation of Ionospheric Measurements model. Our results show that the 135.6 nm emission originated from the equatorial ionization anomaly (EIA) contributes 5 ~ 10\% to the total 135.6 nm intensity and O/N2\ ratio. The EIA feature and longitudinal wave patterns in the GUVI 135.6 nm intensity maps are identified above an altitude of 300 km and show a good agreement with those in the\ F\ region plasma density. However, the EIA feature and longitudinal wave patterns do not appear in the GUVI 135.6 nm intensity maps below an altitude of 300 km and in the GUVI N2\ Lyman-Birge-Hopfield band intensity maps in any altitude. These observations indicate that the longitudinal wave patterns in the GUVI O/N2\ ratio represent the ionospheric phenomenon. Kil, H.; Lee, W.; Shim, J.; Paxton, L.J.; Zhang, Y.; Published by: Journal of Geophysical Research: Space Physics Published on: Jan-02-2013 YEAR: 2013 DOI: 10.1029/2012JA018112 |
|
[1]\ We examine the consequence of enhanced atomic oxygen (OI) 135.6 nm emissions due to the recombination of O+ with electrons on the column number density ratio of atomic oxygen to molecular nitrogen (O/N2 ratio) provided by Global Ultraviolet Imager (GUVI) on board the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics satellite. GUVI O/N2 ratio is derived from the measurements of OI 135.6 nm and N2 Lyman-Birge-Hopfield airglow emissions. The OI 135.6 nm emission arises from two sources: photoelectron impact excitation of neutral atomic oxygen and the radiative recombination of O+ with electrons. We estimate the O/N2 ratio disturbance associated with the O+ density enhancement during geomagnetic storms through the case study of the storms on 20 November 2003 and 8 November 2004. The OI 135.6 nm emission enhancement originating from the ionosphere is derived using the Utah State University Global Assimilation of Ionospheric Measurements model ionosphere. Our results show that the O/N2 ratio increase from the equator to middle latitudes during the storm periods is primarily associated with thermospheric neutral composition disturbances. However, the contribution of the OI 135.6 nm emission originating from the ionosphere to the storm time O/N2 ratio increase is substantial in the northern low-middle latitude regions where severe plasma density enhancements occur during the main phase of the storms. Therefore, the ionospheric contribution should be considered for an accurate assessment of the storm time O/N2 ratio increase at low-middle latitudes during these large storm events. Lee, Woo; Kil, Hyosub; Paxton, Larry; Zhang, Yongliang; Shim, Ja; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2013 YEAR: 2013 DOI: 10.1002/2013JA019132 |
|
The equatorial ionization anomaly (EIA) development is studied using the total electron content (TEC) observed by the Global Positioning System (GPS) satellites, the F2-layer critical frequency (foF2) as measured by digisondes operated in the Brazilian sector, and by model simulation using the SUPIM (Sheffield University Plasmasphere Ionosphere Model). We have used two indices based on foF2 and TEC to represent the strength of the EIA Southern Anomaly Crest (SAC), which are denoted, respectively, by SAC(foF2) and SAC(TEC). Significant differences in the local time variations of the EIA intensity, as represented by these two indices, are investigated. The observed SAC indices are compared with their values modeled by the SUPIM and also by the International Reference Ionosphere (IRI)\textemdash2012. The SUPIM simulations that use the standard E\texttimesB plasma drift and neutral air wind models are found to provide acceptable representations of the observed foF2 and TEC, and hence the indices SAC(foF2) and SAC(TEC) during daytime, whereas the IRI-2012 model is not, except during the post-midnight/sunrise hours. It is found that the differences in the local time variations between the SAC(foF2) and SAC(TEC) can be reduced by limiting the TEC integrations in height up to an altitude of 630\ km in the SUPIM calculations. It is also found that when the EIA intensity is calculated for an intermediate dip latitude (12\textdegreeS) the difference between the local time variation patterns of the two corresponding indices in the experimental data and in the SUPIM results is reduced. For the IRI-2012 values, the subequatorial station modification does not appear to have any effect. Nogueira, P.A.B.; Abdu, M.A.; Souza, J.R.; Batista, I.S.; Bailey, G.J.; Santos, A.M.; Takahashi, H.; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: 11/2013 YEAR: 2013 DOI: 10.1016/j.jastp.2013.08.013 |
|
The paper studies the physical mechanisms of the ionospheric storms at equatorial and higher latitudes, which are generally opposite both during the main phase (MP) and recovery phase (RP) of geomagnetic storms. The mechanisms are based on the natural tendency of physical systems to occupy minimum energy state which is most stable. The paper first illustrates the recent developments in the understanding of the mechanisms during daytime MPs when generally negative ionospheric storms (in Nmax and TEC) develop at equatorial latitudes and positive storms occur at higher latitudes, including why the storms are severe only in some cases. The paper then investigates the relative importance of the physical mechanisms of the positive ionospheric storms observed at equatorial latitudes (within \textpm15\textdegree) during daytime RPs when negative storms occur at higher latitudes using CHAMP Ne and GPS-TEC data and Sheffield University Plasmasphere Ionosphere Model. The results indicate that the mechanical effect of the storm-time equatorward neutral winds that causes plasma convergence at equatorial F region could be a major source for the positive storms, with the downwelling effect of the winds and zero or westward electric field, if present, acting as minor sources. Balan, N.; Otsuka, Y.; Nishioka, M.; Liu, J; Bailey, G.; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2013 YEAR: 2013 DOI: 10.1002/jgra.50275 |
|
The effect of the 135.6 nm emission originated from the ionosphere on the TIMED/GUVI O/N2 ratio Kil, H; Lee, WK; Shim, J; Paxton, LJ; Zhang, Y; Published by: Journal of Geophysical Research: Space Physics Published on: |
|
Lee, Woo; Kil, Hyosub; Paxton, Larry; Zhang, Yongliang; Shim, Ja; Published by: Journal of Geophysical Research: Space Physics Published on: |
| 2012 |
|
Day-to-day variability of equatorial anomaly in GPS-TEC during low solar activity period Aggarwal, Malini; Joshi, H.P.; Iyer, K.N.; Kwak, Y.-S.; Lee, J.J.; Chandra, H.; Cho, K.S.; Published by: Advances in Space Research Published on: Jan-06-2012 YEAR: 2012 DOI: 10.1016/j.asr.2012.03.005 |
|
GPS-TEC variations during low solar activity period (2007--2009) at Indian low latitude stations The paper is based on the ionospheric variations in terms of vertical total electron content (VTEC) for the low solar activity period from May 2007 to April 2009 based on the analysis of dual frequency signals from the Global Positioning System (GPS) satellites recorded at ground stations Varanasi (Geographic latitude 25\textdegree16 \ N, Longitude 82\textdegree59 \ E), situated near the equatorial ionization anomaly crest and other two International GNSS Service (IGS) stations Hyderabad (Geographic latitude 17\textdegree20 \ N, longitude 78\textdegree30 \ E) and Bangalore (Geographic latitude 12\textdegree58 \ N, longitude 77\textdegree33 \ E) in India. We describe the diurnal and seasonal variations of total electron content (TEC), and the effects of a space weather related event i.e. a geomagnetic storm on TEC. The mean diurnal variation during different seasons is brought out. It is found that TEC at all the three stations is maximum during equinoctial months (March, April, September and October), and minimum during the winter months (November, December, January and February), while obtaining intermediate values during summer months (May, June, July and August). TEC shows a semi-annual variation. TEC variation during geomagnetic quiet as well as disturbed days of each month and hence for each season from May 2007 to April 2008 at Varanasi is examined and is found to be more during disturbed period compared to that in the quiet period. Monthly, seasonal and annual variability of GPS-TEC has been compared with those derived from International Reference Ionosphere (IRI)-2007 with three different options of topside electron density, NeQuick, IRI01-corr and IRI 2001. A good agreement is found between the GPS-TEC and IRI model TEC at all the three stations. Kumar, Sanjay; Priyadarshi, S.; Krishna, Gopi; Singh, A.; Published by: Astrophysics and Space Science Published on: 05/2012 YEAR: 2012 DOI: 10.1007/s10509-011-0973-6 geomagnetic storm; GPS; Ionospheric total electron contents; IRI model |
|
The Source of Tidal Signatures in the TIMED/GUVI O/N2 Ratio Kil, H; Lee, W; Shim, J; Paxton, LJ; Zhang, Y; Published by: Published on: |
| 2011 |
|
Bagiya, Mala; Iyer, K.; Joshi, H.; Thampi, Smitha; Tsugawa, Takuya; Ravindran, Sudha; Sridharan, R.; Pathan, B.; Published by: Journal of Geophysical Research Published on: Jan-01-2011 YEAR: 2011 DOI: 10.1029/2010JA015845 |
| 2010 |
|
study of ionospheric response to magnetic superstorms in the East Asian sector Pirog, O.M.; Polekh, N.M.; Romanova, E.B.; Zherebtsov, G.A.; Shi, Jiankui; Wang, Xiao; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: Jan-02-2010 YEAR: 2010 DOI: 10.1016/j.jastp.2009.11.004 |
|
Nishimura, Y.; Kikuchi, T.; Shinbori, A.; Wygant, J.; Tsuji, Y.; Hori, T.; Ono, T.; Fujita, S.; Tanaka, T.; Published by: Journal of Geophysical Research Published on: Jan-01-2010 YEAR: 2010 DOI: 10.1029/2010JA015491 |
|
Nishimura, Y.; Kikuchi, T.; Shinbori, A.; Wygant, J.; Tsuji, Y.; Hori, T.; Ono, T.; Fujita, S.; Tanaka, T.; Published by: Journal of Geophysical Research Published on: Jan-01-2010 YEAR: 2010 DOI: 10.1029/2010JA015491 |
|
Program of transient UV event research at Tatiana-2 satellite Garipov, G.; Khrenov, B.; Klimov, P.; Morozenko, V.; Panasyuk, M.; Petrova, S.; Tulupov, V.; Shahparonov, V.; Svertilov, S.; Vedenkin, N.; Yashin, I.; Jeon, J.; Jeong, S.; Jung, A.; Kim, J.; Lee, J.; Lee, H; Na, G.; Nam, J.; Nam, S.; Park, I.; Suh, J.; Jin, J; Kim, M.; Kim, Y.; Yoo, B.; Park, Y.-S.; Yu, H.; Lee, C.-H.; Park, J.; Salazar, H.; Martinez, O.; Ponce, E.; Cotsomi, J.; Published by: Journal of Geophysical Research Published on: Jan-01-2010 YEAR: 2010 DOI: 10.1029/2009JA014765 |
| 2009 |
|
This paper presents an investigation of geomagnetic storm effects in the equatorial and middle-low latitude F-region in the West Pacific sector during the intense geomagnetic storm on 13\textendash17 April, 2006. The event, preceded by a minor storm, started at 2130 UT on April 13 while interplanetary magnetic field (IMF)\ Bzcomponent was ready to turn southward. From 14\textendash17 the ionosphere was characterized by a large scale enhancement in critical frequency, foF2 (4\~6\ MHz) and total electron content (TEC) (\~30TECU, 1TECU=1\texttimes1016el/m2) followed by a long-duration negative phase observed through the simultaneous ionospheric sounding measurements from 14 stations and GPS network along the meridian 120\textdegreeE. A periodic wave structure, known as traveling ionospheric disturbances (TIDs) was observed in the morning sector during the initial phase of the storm which should be associated with the impulsive magnetospheric energy injection to the auroral. In the afternoon and nighttime, the positive phase should be caused by the combination of equatorward winds and disturbed electric fields verified through the equatorial F-layer peak height variation and modeled upward drift of Fejer and Scherliess [1997. Empirical models of storm time equatorial electric fields. Journal of Geophysical Research 102, 24,047\textendash24,056]. It is shown that the large positive storm effect was more pronounced in the Southern Hemisphere during the morning-noon sector on April 15 and negative phase reached to lower magnetic latitudes in the Northern Hemisphere which may be related to the asymmetry of the thermospheric condition during the storm. Zhao, Biqiang; Wan, Weixing; Liu, Libo; Igarashi, K.; Yumoto, K.; Ning, Baiqi; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: Jan-01-2009 YEAR: 2009 DOI: 10.1016/j.jastp.2008.09.029 |
|
Overview and summary of the Spread F Experiment (SpreadFEx) We provide here an overview of, and a summary of results arising from, an extensive experimental campaign (the Spread F Experiment, or SpreadFEx) performed from September to November 2005, with primary measurements in Brazil. The motivation was to define the potential role of neutral atmosphere dynamics, specifically gravity wave motions propagating upward from the lower atmosphere, in seeding Rayleigh-Taylor instability (RTI) and plasma bubbles extending to higher altitudes. Campaign measurements focused on the Brazilian sector and included ground-based optical, radar, digisonde, and GPS measurements at a number of fixed and temporary sites. Related data on convection and plasma bubble structures were also collected by GOES 12, and the GUVI instrument aboard the TIMED satellite.\ Fritts, D.; Abdu, M.; Batista, B.; Batista, I.; Batista, P.; Buriti, R.; Clemesha, B.; Dautermann, T.; de Paula, E.; Fechine, B.; Fejer, B.; Gobbi, D.; Haase, J.; Kamalabadi, F.; Kherani, E.; Laughman, B.; Lima, P.; Liu, H.-L.; Medeiros, A.; Pautet, P.-D.; Riggin, D.; Rodrigues, F.; Sabbas, F.; Sobral, J.; Stamus, P.; Takahashi, H.; Taylor, M.; Vadas, S.; Vargas, F.; Wrasse, C.; Published by: Annales Geophysicae Published on: Jan-01-2009 YEAR: 2009 DOI: 10.5194/angeo-27-2141-2009 |
|
Takahashi, H.; Taylor, M.; Pautet, P.-D.; Medeiros, A.; Gobbi, D.; Wrasse, C.; Fechine, J.; Abdu, M.; Batista, I.; Paula, E.; Sobral, J.; Arruda, D.; Vadas, S.; Sabbas, F.; Fritts, D.; Published by: Annales Geophysicae Published on: Jan-01-2009 YEAR: 2009 DOI: 10.5194/angeo-27-1477-2009 |
|
Pautet, P.-D.; Taylor, M.; Chapagain, N.; Takahashi, H.; Medeiros, A.; Sabbas, F.; Fritts, D.; Published by: Annales Geophysicae Published on: Jan-01-2009 YEAR: 2009 DOI: 10.5194/angeo-27-2371-2009 |
|
The dual frequency signals from the GPS satellites recorded at Rajkot (22.29 N, 70.74 E, Geographic, 14.03 N Geomagnetic) near the Equatorial ionization anomaly crest in India have been analyzed to study the ionospheric variations in terms of Total Electron Content (TEC) for the low solar activity period from April 2005 to December 2007. In this study, we describe the diurnal and seasonal variations of TEC, solar activity dependence of TEC and effects of a space weather related event, a geomagnetic storm on TEC. The diurnal variation of TEC shows pre-dawn minimum for a short period of time, followed by a steep early morning increase and then reaches maximum value between 14:00 LT and 16:00 LT. The mean diurnal variations during different seasons are brought out. It is found that TEC at Rajkot is at its maximum during Equinoctial months (March, April, September, October), and minimum during the Winter months (November, December, January, February), with intermediate values during Summer months (May, June, July, August), showing a semi annual variation. TEC values have been decreasing since 2005, onwards showing positive correlation with solar activity. TEC variations during the geomagnetic storm commencing 24 August 2005 with Dst=−216 nT are analysed. TEC shows a positive ionospheric storm effect on the first day of the storm and negative ionospheric storm effect on the next day. The equatorial Electrojet control on the development of the equatorial anomaly is also demonstrated. Bagiya, Mala; Joshi, H.; Iyer, K.; Aggarwal, M.; Ravindran, S.; Pathan, B.; Published by: Annales Geophysicae Published on: Jan-01-2009 YEAR: 2009 DOI: 10.5194/angeo-27-1047-2009 |
|
Ionospheric response to the geomagnetic storm on 13–17 April 2006 in the West Pacific region This paper presents an investigation of geomagnetic storm effects in the equatorial and middle-low latitude F-region in the West Pacific sector during the intense geomagnetic storm on 13–17 April, 2006. The event, preceded by a minor storm, started at 2130 UT on April 13 while interplanetary magnetic field (IMF) Bz component was ready to turn southward. From 14–17 the ionosphere was characterized by a large scale enhancement in critical frequency, foF2 (4∼6MHz) and total electron content (TEC) (∼30TECU, 1TECU=1×1016el/m2) followed by a long-duration negative phase observed through the simultaneous ionospheric sounding measurements from 14 stations and GPS network along the meridian 120°E. A periodic wave structure, known as traveling ionospheric disturbances (TIDs) was observed in the morning sector during the initial phase of the storm which should be associated with the impulsive magnetospheric energy injection to the auroral. In the afternoon and nighttime, the positive phase should be caused by the combination of equatorward winds and disturbed electric fields verified through the equatorial F-layer peak height variation and modeled upward drift of Fejer and Scherliess [1997. Empirical models of storm time equatorial electric fields. Journal of Geophysical Research 102, 24,047–24,056]. It is shown that the large positive storm effect was more pronounced in the Southern Hemisphere during the morning-noon sector on April 15 and negative phase reached to lower magnetic latitudes in the Northern Hemisphere which may be related to the asymmetry of the thermospheric condition during the storm. Zhao, Biqiang; Wan, Weixing; Liu, Libo; Igarashi, K.; Yumoto, K.; Ning, Baiqi; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: YEAR: 2009 DOI: https://doi.org/10.1016/j.jastp.2008.09.029 |
|
Medium-scale traveling ionospheric disturbances (MSTIDs) whose peak-to-peak amplitude was larger than 20 TECU (=1016el/m2) were observed at midlatitude during the geomagnetic storm on 10 November 2004. This amplitude was more than 10 times larger than that of the average MSTID. High-resolution data of the GPS Earth Observation Network (GEONET) clarified the characteristic of the total electron content (TEC) disturbances over Japan on 10 November 2004. The disturbances started around 1000 UT in the central part of Japan. The maximum of TEC temporal change was 7.2 TECU in 30 s. The disturbances had several wave fronts which extended from northwest to southeast and propagated from northeast to southwest. TEC data around Japan revealed that the disturbances were mainly observed from 18°N/S to 34°N/S of the geomagnetic latitude in the both hemispheres. Since those characteristics were similar to those of MSTIDs in spite of the unusual large amplitude, the MSTIDs are referred as “super-MSTIDs” in this paper. TEC variations of the super-MSTIDs were also observed at 460 km altitude by the GRACE satellite. The ion density fluctuations of the super-MSTIDs were observed in situ by the CHAMP and DMSP-F15 satellites, which flew at 360 km and 850 km, respectively. It is found that the plasma density variations of the super-MSTIDs occurred mainly above 360 km altitude. The characteristics that distinguish the event from plasma bubbles are its successive wave fronts, constant northwest-southeast direction along which the wave fronts stretched, and late local time of the occurrence. It is found that the uplift of the ionosphere around sunset excited the super-MSTIDs at midlatitudes. The uplift was attributed to the strong eastward electric field during the geomagnetic storm. Nishioka, M.; Saito, A.; Tsugawa, T.; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2009 DOI: https://doi.org/10.1029/2008JA013581 |
|
There have been studied temporal variations of the (southern) equatorial boundary of hydrogen emission Hα with the intensity of over 200 Rayleighs within a large latitude range (670- Published by: Physics of Auroral Phenomena Published on: |
|
Igarashi, K; Nakamura, M; Paxton, LJ; Published by: 中国科学院地质与地球物理研究所 2008 学术论文汇编 Published on: |
|
Ionospheric response to the geomagnetic storm on 13—17 April 2006 in the West Pacific region Zhao, Biqiang; Wan, Weixing; Liu, Libo; Igarashi, K; Yumoto, K; Ning, Baiqi; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: |
| 2008 |
|
The Spread F Experiment, or SpreadFEx, was performed from September to November 2005 to define the potential role of neutral atmosphere dynamics, primarily gravity waves propagating upward from the lower atmosphere, in seeding equatorial spread F (ESF) and plasma bubbles extending to higher altitudes. A description of the SpreadFEx campaign motivations, goals, instrumentation, and structure, and an overview of the results presented in this special issue, are provided by Fritts et al. (2008a). The various analyses of neutral atmosphere and ionosphere dynamics and structure described in this special issue provide enticing evidence of gravity waves arising from deep convection in plasma bubble seeding at the bottomside F layer. Our purpose here is to employ these results to estimate gravity wave characteristics at the bottomside F layer, and to assess their possible contributions to optimal seeding conditions for ESF and plasma instability growth rates. We also assess expected tidal influences on the environment in which plasma bubble seeding occurs, given their apparent large wind and temperature amplitudes at these altitudes. We conclude 1) that gravity waves can achieve large amplitudes at the bottomside F layer, 2) that tidal winds likely control the orientations of the gravity waves that attain the highest altitudes and have the greatest effects, 3) that the favored gravity wave orientations enhance most or all of the parameters influencing plasma instability growth rates, and 4) that gravity wave and tidal structures acting together have an even greater potential impact on plasma instability growth rates and plasma bubble seeding. Fritts, D.; Vadas, S.; Riggin, D.; Abdu, M.; Batista, I.; Takahashi, H.; Medeiros, A.; Kamalabadi, F.; Liu, H.-L.; Fejer, B.; Taylor, M.; Published by: Annales Geophysicae Published on: 10/2008 YEAR: 2008 DOI: 10.5194/angeo-26-3235-2008 |
|
Sakaguchi, Kaori; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Otsuka, Yuichi; Ogawa, Tadahiko; Asamura, Kazushi; Connors, M; Published by: Journal of Geophysical Research: Space Physics Published on: |
|
Sakaguchi, Kaori; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Otsuka, Yuichi; Ogawa, Tadahiko; Asamura, Kazushi; Connors, M; Published by: Journal of Geophysical Research: Space Physics Published on: |
|
Ionosphere disturbances observed throughout Southeast Asia of the superstorm of 20--22 November 2003 Ionospheric disturbances in the Southeast Asian region during the super magnetic storm of 20–22 November 2003 were investigated through an ionosonde chain and a GPS network assisted by the space-borne instruments. At early stage of the storm in the postsunset sector, large enhancements in the critical frequency of F2 layer and total electron content were observed at northern crest region of the equatorial ionization anomaly (EIA), which might be produced by both the storm meridional wind superimposed with traveling atmospheric disturbances and prompt penetration electric field (PPE). During the main phase of the storm when interplanetary magnetic field started a 12-h southward turning, equatorial ionosphere was elevated to a very high level which should be most probably caused by a long-duration PPE event. Meanwhile, at mid-low latitudes, ionosphere witnessed an initial simultaneous decrease then followed by drastic increases, which is very different from the past observations in this region (Reddy and Nishida, 1992). Combined analysis of the data from the ionosonde and other space-based measurement shows that for the present case the penetration efficiency of the interplanetary electric field (IEF) to the equatorial ionosphere was larger at night than in the daytime, which agrees with the results of Fejer et al. (2007) showing the ratios of PPE and IEF changes were highly variable with the local time. During the recovery phase, EIA was severely inhibited owing to a wind convergence and possibly because of the westward disturbance dynamo electric field. Zhao, B; Wan, W; Tschu, K; Igarashi, K; Kikuchi, T; Nozaki, K; Watari, S; Li, G; Paxton, LJ; Liu, L; , others; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2008 DOI: 10.1029/2008JA013054 |
|
Zhao, B; Wan, W; Liu, L; Igarashi, K; Nakamura, M; Paxton, LJ; Su, S-Y; Li, G; Ren, Z; Published by: Journal of Geophysical Research: Space Physics Published on: |
|
Koustov, Alexandre; Nishitani, Nozomu; Ebihara, Y; Kikuchi, T; Hairston, M.R.; Andre, D.; Published by: Published on: |
| 2007 |
|
Kataoka, Ryuho; Nishitani, Nozomu; Ebihara, Yusuke; Hosokawa, Keisuke; Ogawa, Tadahiko; Kikuchi, Takashi; Miyoshi, Yoshizumi; Published by: Geophysical Research Letters Published on: Jan-01-2007 YEAR: 2007 DOI: 10.1029/2007GL031552 |