The Experts below are selected from a list of 156 Experts worldwide ranked by ideXlab platform
H. C. Yeh - One of the best experts on this subject based on the ideXlab platform.
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Ion temperature variation observed by ROCSAT-1 satellite in the afternoon sector and its comparison with IRI-2001 model
Advances in Space Research, 2006Co-Authors: Chi-kuang Chao, H. C. YehAbstract:Abstract The ion temperature has been measured with the ionospheric plasma and electrodynamics instrument (IPEI) onboard the first satellite of Republic of China, ROCSAT-1, orbiting at 600 km altitude with a 35° inclination. Global ion temperature distributions in the afternoon sector for different seasons are investigated during the solar maximum year of 2000. The temperature troughs at the dip equator are found to incline and become shallower until the evening temperature enhancement has reached to its peak. The temperature troughs follow with the electron temperature variation through the heat exchange between electrons and ions. The temperature crests in the winter hemisphere are also noticed in the afternoon sector but have a smaller magnitude than those in the morning sector. The magnitudes of the temperature crests are reduced first and then enhanced later as local time increases. The locations of the temperature maxima within the temperature crests shift from longitudes of positive Magnetic Declination to longitudes of negative Magnetic Declination during the June solstice and from longitudes of negative Magnetic Declination to longitudes of positive Magnetic Declination during the December solstice. Both magnitudes and movements of the temperature crests can be understood with the field-aligned ion flow pattern observed by ROCSAT and are attributed to the change of the neutral wind pattern in zonal direction from westward to eastward. These features from the ROCSAT observations are not available in the IRI-2001 model yet.
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Ion temperature crests and troughs in the morning sector of the low‐latitude and midlatitude topside ionosphere
Journal of Geophysical Research, 2004Co-Authors: Chi-kuang Chao, H. C. YehAbstract:[1] The low-latitude and midlatitude topside ionospheric ion temperature at 600 km altitude has been measured with the Ionospheric Plasma and Electrodynamics Instrument (IPEI) instrument on board ROCSAT-1 satellite in the solar maximum year of 2000. Global hemispheric asymmetrical distribution of this topside ion temperature in the morning hour is presented here for the first time and is explained with the associated observation of the field-aligned ion flow and ion concentration. Crests of ion temperature are found along the dip latitudes between 10° and 25° in the winter hemisphere during the solstice seasons. The maximum in the temperature crests is located in a longitudinal region of positive Magnetic Declination in the southern hemisphere during the June solstice and in the longitudinal region of negative Magnetic Declination in the northern hemisphere during the December solstice. Ion compression from a downward field-aligned ion flow driven by morning neutral wind is concluded to cause the ion heating in the winter hemisphere as modeled by Bailey et al. [1975]. On the other hand, in the 0700–0800 LT sector, there are low-temperature regions at higher latitudes in a longitude region of negative Magnetic Declination in the southern hemisphere during the June solstice and in the longitudinal region of positive Magnetic Declination in the northern hemisphere during the December solstice. A low photoionization rate together with an ion expansion cooling process from the upward field-aligned plasma flow has resulted in such low temperature in these regions. As for temperature troughs observed near the dip equator in the morning hour, it is attributed to the convective heat loss in the summer hemisphere initially in the early morning hour and then to the rapid increase of plasma concentration at the dip equator in the late morning hour for all seasons.
Chi-kuang Chao - One of the best experts on this subject based on the ideXlab platform.
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Cause of different local time distribution in the postsunset equatorial ionospheric irregularity occurrences between June and December solstices
Journal of Geophysical Research: Space Physics, 2009Co-Authors: Chi-kuang Chao, C. H. LiuAbstract:[1] Global averaged postsunset equatorial ionospheric density irregularity occurrences observed by ROCSAT during the moderate to high solar activity years of 1999 to 2004 indicate a different local time distribution between June and December solstices. The irregularity occurrences during the December solstice show a faster increase rate to peak at 2100–2200 local time, while the irregularity occurrences during the June solstice have a slower increase rate and peak one hour later in local time than that in the December solstice. The cause of such different local time distributions is attributed to a large contrast in the time of zonal drift reversal and the magnitude of postsunset vertical drift observed by ROCSAT at longitudes of large Magnetic Declination in the two solstices. That is, a delay in the zonal drift reversal in association with a smaller postsunset vertical drift observed at longitudes of positive Magnetic Declination has greatly inhibited the irregularity occurrences during the June solstice in contrast to an earlier zonal drift reversal together with a large vertical drift occurring at longitudes of negative Magnetic Declination to accelerate the irregularity occurrences during the December solstice. We think that the different geoMagnetic field strengths that existed between the longitudes of positive and negative Magnetic Declinations have played a crucial role in determining the different local time distributions of irregularity occurrences for the two solstices.
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Ion temperature variation observed by ROCSAT-1 satellite in the afternoon sector and its comparison with IRI-2001 model
Advances in Space Research, 2006Co-Authors: Chi-kuang Chao, H. C. YehAbstract:Abstract The ion temperature has been measured with the ionospheric plasma and electrodynamics instrument (IPEI) onboard the first satellite of Republic of China, ROCSAT-1, orbiting at 600 km altitude with a 35° inclination. Global ion temperature distributions in the afternoon sector for different seasons are investigated during the solar maximum year of 2000. The temperature troughs at the dip equator are found to incline and become shallower until the evening temperature enhancement has reached to its peak. The temperature troughs follow with the electron temperature variation through the heat exchange between electrons and ions. The temperature crests in the winter hemisphere are also noticed in the afternoon sector but have a smaller magnitude than those in the morning sector. The magnitudes of the temperature crests are reduced first and then enhanced later as local time increases. The locations of the temperature maxima within the temperature crests shift from longitudes of positive Magnetic Declination to longitudes of negative Magnetic Declination during the June solstice and from longitudes of negative Magnetic Declination to longitudes of positive Magnetic Declination during the December solstice. Both magnitudes and movements of the temperature crests can be understood with the field-aligned ion flow pattern observed by ROCSAT and are attributed to the change of the neutral wind pattern in zonal direction from westward to eastward. These features from the ROCSAT observations are not available in the IRI-2001 model yet.
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Ion temperature crests and troughs in the morning sector of the low‐latitude and midlatitude topside ionosphere
Journal of Geophysical Research, 2004Co-Authors: Chi-kuang Chao, H. C. YehAbstract:[1] The low-latitude and midlatitude topside ionospheric ion temperature at 600 km altitude has been measured with the Ionospheric Plasma and Electrodynamics Instrument (IPEI) instrument on board ROCSAT-1 satellite in the solar maximum year of 2000. Global hemispheric asymmetrical distribution of this topside ion temperature in the morning hour is presented here for the first time and is explained with the associated observation of the field-aligned ion flow and ion concentration. Crests of ion temperature are found along the dip latitudes between 10° and 25° in the winter hemisphere during the solstice seasons. The maximum in the temperature crests is located in a longitudinal region of positive Magnetic Declination in the southern hemisphere during the June solstice and in the longitudinal region of negative Magnetic Declination in the northern hemisphere during the December solstice. Ion compression from a downward field-aligned ion flow driven by morning neutral wind is concluded to cause the ion heating in the winter hemisphere as modeled by Bailey et al. [1975]. On the other hand, in the 0700–0800 LT sector, there are low-temperature regions at higher latitudes in a longitude region of negative Magnetic Declination in the southern hemisphere during the June solstice and in the longitudinal region of positive Magnetic Declination in the northern hemisphere during the December solstice. A low photoionization rate together with an ion expansion cooling process from the upward field-aligned plasma flow has resulted in such low temperature in these regions. As for temperature troughs observed near the dip equator in the morning hour, it is attributed to the convective heat loss in the summer hemisphere initially in the early morning hour and then to the rapid increase of plasma concentration at the dip equator in the late morning hour for all seasons.
Yukio Horiguchi - One of the best experts on this subject based on the ideXlab platform.
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Estimation of Magnetic Declination angle using reduced QUEST for an unmanned aerial vehicle
2010 IEEE International Conference on Industrial Technology, 2010Co-Authors: Hiroaki Nakanishi, Sayaka Kanata, Tetsuo Sawaragi, Yukio HoriguchiAbstract:Measurement of the heading angle which is free from Magnetic Declination using several GPS antennas is widely applied, but it is not suitable for small unmanned aerial vehicles because of their limit of the payload and body length. In this paper, we propose a method to estimate the Magnetic Declination angle using an inertial measurement unit(IMU) and only one GPS antenna. The method consists of 1) estimation of the acceleration of the motion from GPS measurements and 2) estimation of the Magnetic Declination angle using the estimated accelerations and IMU measurements. We show that the estimation of the MagneticDeclination angle results in reduced QUESTflO], that is an eigenvalue problem of 2 × 2 real matrix. Flight experimental results using an unmanned helicopter demonstrate the effectiveness of the proposed methods.
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Methods to Estimate Magnetic Declination for an Unmanned Aerial Vehicle
Journal of Robotics and Mechatronics, 2008Co-Authors: Hiroaki Nakanishi, Sayaka Kanata, Tetsuo Sawaragi, Yukio HoriguchiAbstract:Measurement of the heading free from Magnetic Declination using several GPS antennas is widely used, but it is not suitable for small unmanned aerial vehicles because of limited payload and body length. In this paper, we propose two methods to estimate Magnetic Declination. One is for UAV for 3D terrain mapping with a laser scanner. Measurements which are collected from different directions are matched to estimate magnet Declination. The other uses an IMU and one GPS antenna. It consists of 1) estimation of acceleration of motion from GPS measurements and 2) estimation of Magnetic Declination using the estimated acceleration and IMU measurement. We show that the estimation of Magnetic Declination results in reduced QUEST, an eigenvalue problem of a 2 × 2 real matrix using a quaternion which expresses rotation. Experimental results of flight control of an unmanned helicopter demonstrate the effectiveness of proposed methods.
Hiroaki Nakanishi - One of the best experts on this subject based on the ideXlab platform.
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Estimation of Magnetic Declination angle using reduced QUEST for an unmanned aerial vehicle
2010 IEEE International Conference on Industrial Technology, 2010Co-Authors: Hiroaki Nakanishi, Sayaka Kanata, Tetsuo Sawaragi, Yukio HoriguchiAbstract:Measurement of the heading angle which is free from Magnetic Declination using several GPS antennas is widely applied, but it is not suitable for small unmanned aerial vehicles because of their limit of the payload and body length. In this paper, we propose a method to estimate the Magnetic Declination angle using an inertial measurement unit(IMU) and only one GPS antenna. The method consists of 1) estimation of the acceleration of the motion from GPS measurements and 2) estimation of the Magnetic Declination angle using the estimated accelerations and IMU measurements. We show that the estimation of the MagneticDeclination angle results in reduced QUESTflO], that is an eigenvalue problem of 2 × 2 real matrix. Flight experimental results using an unmanned helicopter demonstrate the effectiveness of the proposed methods.
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Methods to Estimate Magnetic Declination for an Unmanned Aerial Vehicle
Journal of Robotics and Mechatronics, 2008Co-Authors: Hiroaki Nakanishi, Sayaka Kanata, Tetsuo Sawaragi, Yukio HoriguchiAbstract:Measurement of the heading free from Magnetic Declination using several GPS antennas is widely used, but it is not suitable for small unmanned aerial vehicles because of limited payload and body length. In this paper, we propose two methods to estimate Magnetic Declination. One is for UAV for 3D terrain mapping with a laser scanner. Measurements which are collected from different directions are matched to estimate magnet Declination. The other uses an IMU and one GPS antenna. It consists of 1) estimation of acceleration of motion from GPS measurements and 2) estimation of Magnetic Declination using the estimated acceleration and IMU measurement. We show that the estimation of Magnetic Declination results in reduced QUEST, an eigenvalue problem of a 2 × 2 real matrix using a quaternion which expresses rotation. Experimental results of flight control of an unmanned helicopter demonstrate the effectiveness of proposed methods.
James L. Gould - One of the best experts on this subject based on the ideXlab platform.
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Animal Navigation: A Novel Map Strategy
Current biology : CB, 2017Co-Authors: James L. GouldAbstract:Elegant new experiments show that migrant birds at high European latitudes can use Magnetic Declination to infer longitude.
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Animal Navigation: A Novel Map Strategy
Current Biology, 2017Co-Authors: James L. GouldAbstract:Summary Elegant new experiments show that migrant birds at high European latitudes can use Magnetic Declination to infer longitude.
