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Found 31 entries in the Bibliography.

Showing entries from 1 through 31

2022

Far-ultraviolet airglow remote sensing measurements on Feng Yun 3-D meteorological satellite

\textlessp\textgreater\textlessstrong class="journal-contentHeaderColor"\textgreaterAbstract.\textless/strong\textgreater The Ionospheric Photometer (IPM) is carried on the Feng Yun 3-D (FY3D) meteorological satellite, which allows for the measurement of far-ultraviolet (FUV) airglow radiation in the thermosphere. IPM is a compact and high-sensitivity nadir-viewing FUV remote sensing instrument. It monitors 135.6 nm emission in the nightside thermosphere and 135.6 nm and N\textlessspan class="inline-formula"\textgreater$_\textrm2$\textless/span\textgreater Lyman–Birge–Hopfield (LBH) emissions in the dayside thermosphere that can be used to invert the peak electron density of the F\textlessspan class="inline-formula"\textgreater$_\textrm2$\textless/span\textgreater layer (NmF\textlessspan class="inline-formula"\textgreater$_\textrm2$)\textless/span\textgreater at night and the \textlessspan class="inline-formula"\textgreater\textlessmath xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"\textgreater\textlessmrow class="chem"\textgreater\textlessmi mathvariant="normal"\textgreaterO\textless/mi\textgreater\textlessmo\textgreater/\textless/mo\textgreater\textlessmi mathvariant="normal"\textgreaterN\textless/mi\textgreater\textless/mrow\textgreater\textless/math\textgreater\textlessspan\textgreater\textlesssvg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="73a3f14187048fa14eee70dd1027ad23"\textgreater\textlesssvg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-15-1577-2022-ie00001.svg" width="25pt" height="14pt" src="amt-15-1577-2022-ie00001.png"/\textgreater\textless/svg:svg\textgreater\textless/span\textgreater\textless/span\textgreater\textlessspan class="inline-formula"\textgreater$_\textrm2$\textless/span\textgreater ratio in the daytime, respectively. Preliminary observations show that the IPM could monitor the global structure of the equatorial ionization anomaly (EIA) structure around 02:00 LT using atomic oxygen (OI) 135.6 nm nightglow. It could also identify the reduction of \textlessspan class="inline-formula"\textgreater\textlessmath xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"\textgreater\textlessmrow class="chem"\textgreater\textlessmi mathvariant="normal"\textgreaterO\textless/mi\textgreater\textlessmo\textgreater/\textless/mo\textgreater\textlessmi mathvariant="normal"\textgreaterN\textless/mi\textgreater\textless/mrow\textgreater\textless/math\textgreater\textlessspan\textgreater\textlesssvg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="7662cd64e23809d534f2b5721e55261b"\textgreater\textlesssvg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-15-1577-2022-ie00002.svg" width="25pt" height="14pt" src="amt-15-1577-2022-ie00002.png"/\textgreater\textless/svg:svg\textgreater\textless/span\textgreater\textless/span\textgreater\textlessspan class="inline-formula"\textgreater$_\textrm2$\textless/span\textgreater in the high-latitude region during the geomagnetic storm of 26 August 2018. The IPM-derived NmF\textlessspan class="inline-formula"\textgreater$_\textrm2$\textless/span\textgreater agrees well with that observed by four ionosonde stations along 120\textlessspan class="inline-formula"\textgreater$^\textrm∘$\textless/span\textgreater E with a standard deviation of 26.67 \%. Initial results demonstrate that the performance of IPM meets the design requirements and therefore can be used to study the thermosphere and ionosphere in the future.\textless/p\textgreater

Wang, Yungang; Fu, Liping; Jiang, Fang; Hu, Xiuqing; Liu, Chengbao; Zhang, Xiaoxin; Li, JiaWei; Ren, Zhipeng; He, Fei; Sun, Lingfeng; Sun, Ling; Yang, Zhongdong; Zhang, Peng; Wang, Jingsong; Mao, Tian;

Published by: Atmospheric Measurement Techniques Published on: mar

YEAR: 2022 DOI: 10.5194/amt-15-1577-2022

Far-ultraviolet airglow remote sensing measurements on Feng Yun 3-D meteorological satellite

Published by: Atmospheric Measurement Techniques Published on: mar

YEAR: 2022 DOI: 10.5194/amt-15-1577-2022

Responses of Mesosphere and Lower Thermosphere Temperature to the Geomagnetic Storm on 7–8 September 2017

The variations of neutral temperature in the mesosphere and lower thermosphere (MLT) region, during the 7–8 September 2017 intense geomagnetic storm, are studied using observations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. They are also studied using simulations by the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIMEGCM). The neutral temperature data cover the altitudes from 80 km to 110 km between 83° N and 52° S latitude, obtained from both SABER observations and model simulations. The SABER observations reveal that temperature increases (the maximum increase is larger than 35 K at \textasciitilde108 km) and decreases (the maximum decrease is larger than 20 K at \textasciitilde105 km) during the geomagnetic storm. The storm effects penetrate down to \textasciitilde80 km. In observations, temperature variations corresponding to the storm show hemispheric asymmetry. That is, the variations of temperature are more prominent in the northern hemisphere than in the southern hemisphere. Conversely, the TIMEGCM outputs agree with the observations in general but overestimate the temperature increases and underestimate the temperature decreases at high and middle latitudes. Meanwhile, the simulations show stronger temperature decreases and weaker temperature increases than observations at low latitudes. After analyzing the temperature variations, we suggest that vertical winds may play an important role in inducing these significant variations of temperature in the MLT region.

Sun, Meng; Li, Zheng; Li, Jingyuan; Lu, Jianyong; Gu, Chunli; Zhu, Mengbin; Tian, Yufeng;

Published by: Universe Published on: feb

YEAR: 2022 DOI: 10.3390/universe8020096

geomagnetic storm; temperature; the mesosphere and lower thermosphere (MLT); TIMEGCM

Significant Variations of Thermospheric Nitric Oxide Cooling during the Minor Geomagnetic Storm on 6 May 2015

Using observations by the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument on board the TIMED (Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics) satellite and simulations by the TIEGCM (Thermosphere-Ionosphere-Electrodynamics General Circulation Model), we investigate the daytime variations of thermospheric nitric oxide (NO) cooling during the geomagnetic storm on 6 May 2015. The geomagnetic storm was minor, as the minimum Dst was −28 nT, the maximum Kp was 5+ and the maximum AE was 1259 nT. However, significant enhancements of peak NO cooling rate and prominent decreases in the peak NO cooling altitude were observed from high latitudes to low latitudes in both hemispheres on the dayside by the SABER instrument. The model simulations underestimate the response of peak NO cooling and have no significant variation of the altitude of peak NO cooling rate on the dayside during this minor geomagnetic storm. By investigating the temporal and latitudinal variations of vertical NO cooling profiles inferred from SABER data, we suggest that the horizontal equatorward winds caused by the minor geomagnetic storm were unexpectedly strong and thus play an important role in inducing these significant daytime NO cooling variations.

Li, Zheng; Sun, Meng; Li, Jingyuan; Zhang, Kedeng; Zhang, Hua; Xu, Xiaojun; Zhao, Xinhua;

Published by: Universe Published on: apr

YEAR: 2022 DOI: 10.3390/universe8040236

geomagnetic storm; thermosphere; nitric oxide cooling

The origin of midlatitude plasma depletions detected during the 12 February 2000 and 29 October 2003 geomagnetic storms

Kil, Hyosub; Chang, Hyeyeon; Lee, Woo; Paxton, Larry; Sun, Andrew; Lee, Jiyun;

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

YEAR: 2022 DOI:

Ionospheric Disturbances in Low- and Midlatitudes During the Geomagnetic Storm on 26 August 2018

Plasma density depletions at midlatitudes during geomagnetic storms are often understood in terms of equatorial plasma bubbles (EPBs) due to their morphological similarity. However, our study reports the observations that reveal the generation of plasma depletions at midlatitudes by local sources. During the geomagnetic storm on 26 August 2018, the Defense Meteorological Satellite Program and Swarm satellites detected plasma depletions at midlatitudes in the Asian sector in the absence of EPBs in the equatorial region. This observation and the total electron content (TEC) maps over Japan demonstrate that traveling ionospheric disturbances (TIDs) are the sources of midlatitude plasma depletions in the Asian sector. Near the west coast of the United States, the development of a narrow TEC depletion band was identified from TEC maps. The TEC depletion band, which is elongated in the northwest–southeast direction, moves toward the west with a velocity of approximately 240 m/s. The TEC at the TEC depletion band is about 5 TEC units (1016 m−2) smaller than the ambient TEC. As this band is confined to the midlatitudes, this phenomenon is not associated with an EPB. The characteristics of the TEC depletion band are consistent with those of medium-scale TIDs. Observations in the Asian sector and the TEC depletion band over the United States demonstrate that plasma depletions can develop at midlatitudes by local sources. Therefore, the morphological similarity between midlatitude irregularities and EPBs or their coincident occurrence does not provide corroborating evidence of their connection.

Chang, Hyeyeon; Kil, Hyosub; Sun, Andrew; Zhang, Shun-Rong; Lee, Jiyun;

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

YEAR: 2022 DOI: 10.1029/2021JA029879

Retrospect and prospect of ionospheric weather observed by FORMOSAT-3/COSMIC and FORMOSAT-7/COSMIC-2

FORMOSAT-3/COSMIC (F3/C) constellation of six micro-satellites was launched into the circular low-earth orbit at 800 km altitude with a 72-degree inclination angle on 15 April 2006

Liu, Tiger; Lin, Charles; Lin, Chi-Yen; Lee, I-Te; Sun, Yang-Yi; Chen, Shih-Ping; Chang, Fu-Yuan; Rajesh, Panthalingal; Hsu, Chih-Ting; Matsuo, Tomoko; , others;

Published by: Terrestrial, Atmospheric and Oceanic Sciences Published on:

YEAR: 2022 DOI: 10.1007/s44195-022-00019-x

2021

Wide-field aurora imager onboard Fengyun satellite: Data products and validation

New observations of auroras based on the wide-field aurora imager (WAI) onboard Fengyun-3D (FY-3D) satellite are exhibited in this paper. Validity of the WAI data is analyzed by comparing auroral boundaries derived from WAI observations with results obtained from data collected by the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) aboard the Defense Meteorological Satellite Program (DMSP F18). Dynamic variations of the aurora with the solar wind, interplanetary magnetic field (IMF) parameters, and the SYM-H index are also investigated. The comparison of auroral boundaries indicates that the WAI data are morphologically valid and suitable to the study of auroral dynamics. Effective responses to solar wind parameters indicate that the WAI data can be useful to monitor and predict the Earth s space weather. Since the configuration of aurora is a good indicator of the solar wind-magnetosphere-ionosphere (SW-M-I) coupling system, and can reflect the disturbance of the space environment, the WAI will provide important data to help us to study the physical processes in space.

Ding, GuangXing; Li, JiaWei; Zhang, Xiaoxin; He, Fei; He, LingPing; Song, KeFei; Sun, Liang; Dai, Shuang; Liu, ShiJie; Chen, Bo; Yu, Chao; Hu, Xiuqing; Gu, SongYan; Yang, Zhongdong; Zhang, Peng;

Published by: Earth and Planetary Physics Published on:

YEAR: 2021 DOI: 10.26464/epp2021003

auroral dynamics; FY-3D; SSUSI; SW-M-I; WAI

Impact of Storm-Enhanced Density (SED) on Ion Upflow Fluxes During Geomagnetic Storm

The impact of the dynamic evolution of the Storm-Enhanced Density (SED) on the upward ion fluxes during the March 06, 2016 geomagnetic storm is studied using comprehensive multi-scale datasets. This storm was powered by a Corotating Interaction Region (CIR), and the minimum Sym-H reached ∼−110 nT. During the ionospheric positive storm phase, the SED formed and the associated plume and polar cap patches occasionally drifted anti-sunward across the polar cap. When these high-density structures encountered positive vertical flows, large ion upward fluxes were produced, with the largest upward flux reaching 3 × 1014 m−2s−1. These upflows were either the type-1 ion upflow associated with fast flow channels, such as the subauroral polarization stream (SAPS) channel, or the type-2 ion upflow due to soft particle precipitations in the cusp region. The total SED-associated upflow flux in the dayside cusp can be comparable to the total upflow flux in the nightside auroral zone despite the much smaller cusp area compared with the auroral zone. During the ionospheric negative storm phase, the ionospheric densities within the SED and plume decreased significantly and thus led to largely reduced upward fluxes. This event analysis demonstrates the critical role of the ionospheric high-density structures in creating large ion upward fluxes. It also suggests that the dynamic processes in the coupled ionosphere-thermosphere system and the resulting state of the ionospheric storm are crucial for understanding the temporal and spatial variations of ion upflow fluxes and thus should be incorporated into coupled geospace models for improving our holistic understanding of the role of ionospheric plasma in the geospace system.

Zou, Shasha; Ren, Jiaen; Wang, Zihan; Sun, Hu; Chen, Yang;

Published by: Frontiers in Astronomy and Space Sciences Published on:

YEAR: 2021 DOI:

Interaction Between an EMSTID and an EPB in the EIA Crest Region Over China

Few observations investigated the interaction between an electrical medium-scale traveling ionospheric disturbance (EMSTID) and an equatorial plasma bubble (EPB). This paper presents another interaction between a southwestward propagating EMSTID and an eastward drifting EPB in the equatorial ionization anomaly (EIA) crest region of China. When the EMSTID and the EPB touched each other, several depletions of the EMSTID (EPB) showed the eastward (westward) velocity disturbances of the EPB (EMSTID) depletions. Besides, phase elongations of the EPB depletions contrarotated as the EMSTID propagated southwestward. However, of important finding is that the interaction of the EMSTID and the EPB could have polarized one depletion of the postmidnight EPB that should have become a fossilized bubble. Inside that polarized EPB depletion were meter-scale irregularities that caused activated radar echoes and enhanced ranged spread F (RSF). The interaction occurred in descending ionosphere and the lower density regions got filled up with an enhanced density plasma. We propose that the EMSTID and the EPB could have electrically coupled with each other, causing an enhanced polarization electric field (PEF) that polarized that EPB depletion; the E × B gradient drift instability (Kelley, 1989) could have caused the meter-scale irregularities when that enhanced PEF was imposed on that reactivated EPB depletion surrounded by that enhanced density plasma. This study provides observational evidence that how an electrical couple of EMSTID and EPB events can activate a postmidnight EPB depletion that should become a fossilized structure.

Sun, Longchang; Xu, JiYao; Zhu, Yajun; Xiong, Chao; Yuan, Wei; Wu, Kun; Hao, Yongqiang; Chen, Gang; Yan, Chunxiao; Wang, Zhihua; Zhao, Xiukuan; Luo, Xiaomin;

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

YEAR: 2021 DOI: 10.1029/2020JA029005

airglow; EIA crest region; Interaction between MSTID and EPB; Nighttime plasma density enhancement; Polarization of postmidnight EPB; VHF radar echoes and range spread F

2020

The seasonal and longitudinal variations of nighttime OI 135.6-nm emission at equatorial ionization anomaly crests observed by the DMSP/SSUSI

the South American longitudinal sector, which was also observed by GUVI data (Kil et al., 2004); This result was also observed by GUVI in Kil et al. (2004), ROCSAT-1 in Y. Chen et al.

Guo, Bing; Xu, JiYao; Sun, Longchang; Lin, Yingjun; Yuan, Wei;

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

YEAR: 2020 DOI: 10.1029/2019JA027764

The day-glow data application of FY-3D IPM in monitoring O/N2

The Ionosphere Photometer (IPM) is a far ultraviolet nadir-viewing photometer that flew aboard the second-generation, polar-orbiting Chinese meteorological satellite FY-3D, which was

Jiang, Fang; Mao, Tian; Zhang, Xiaoxin; Wang, Yungang; Fu, Liping; Hu, Xiuqing; Wang, DaXin; Jia, Nan; Wang, Tianfang; Sun, YueQiang;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on:

YEAR: 2020 DOI: 10.1016/j.jastp.2020.105309

Observation of thermosphere and ionosphere using the ionosphere PhotoMeter (IPM) on the Chinese meteorological satellite FY-3D

The Ionosphere PhotoMeter (IPM) is a far ultraviolet nadir-viewing photometer that flew aboard the second-generation, polar-orbiting Chinese meteorological satellite Feng-Yun 3D (FY-3D), which was launched on November 25th, 2017.

Jiang, Fang; Mao, Tian; Zhang, Xiaoxin; Wang, Yun-Gang; Hu, Xiuqing; Wang, DaXin; Jia, Nan; Wang, Tianfang; Sun, YueQiang; Fu, Li-Ping;

Published by: Advances in Space Research Published on:

YEAR: 2020 DOI: 10.1016/j.asr.2020.07.027

2019

Wide-field auroral imager onboard the Fengyun satellite

The newly launched Fengyun-3D (FY-3D) satellite carried a wide-field auroral imager (WAI) that was developed by Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences (CIOMP), which will provide a large field of view (FOV), high spatial resolution, and broadband ultraviolet images of the aurora and the ionosphere by imaging the N₂ LBH bands of emissions. The WAI consists of two identical cameras, each with an FOV of 68\textdegree in the along-track direction and 10\textdegree in the cross-track direction. The two cameras are tilted relative to each other to cover a fan-shaped field of size 130\textdegree \texttimes 10\textdegree. Each camera consists of an unobstructed four-mirror anastigmatic optical system, a BaF₂ filter, and a photon-counting imaging detector. The spatial resolution of WAI is ~10 km at the nadir point at a reference height of 110 km above the Earth\textquoterights surface. The sensitivity is \>0.01 counts s^-1 Rayleigh^-1 pixel^-1 (140\textendash180 nm) for both cameras, which is sufficient for mapping the boundaries and the fine structures of the auroral oval during storms/substorms. Based on the tests and calibrations that were conducted prior to launch, the data processing algorithm includes photon signal decoding, geometric distortion correction, photometric correction, flat-field correction, line-of-sight projection and correction, and normalization between the two cameras. Preliminarily processed images are compared with DMSP SSUSI images. The agreement between the images that were captured by two instruments demonstrates that the WAI and the data processing algorithm operate normally and can provide high-quality scientific data for future studies on auroral dynamics.

Zhang, Xiao-Xin; Chen, Bo; He, Fei; Song, Ke-Fei; He, Ling-Ping; Liu, Shi-Jie; Guo, Quan-Feng; Li, Jia-Wei; Wang, Xiao-Dong; Zhang, Hong-Ji; Wang, Hai-Feng; Han, Zhen-Wei; Sun, Liang; Zhang, Pei-Jie; Dai, Shuang; Ding, Guang-Xing; Chen, Li-Heng; Wang, Zhong-Su; Shi, Guang-Wei; Zhang, Xin; Yu, Chao; Yang, Zhong-Dong; Zhang, Peng; Wang, Jin-Song;

Published by: Light: Science \& Applications Published on: 05/2019

YEAR: 2019 DOI: 10.1038/s41377-019-0157-7

2018

Signatures of the Solar Transient Disturbances Over the Low Latitude Ionosphere During 6 to 8 September 2017

Low latitude ionospheric behavior during solar transient disturbances of solar flares and storm time penetrating electric fields comprises an important part of the Earth\textquoterights space weather. The flares enhance the electron density of the sunlit ionosphere by supplying excess solar radiation. However, the degree of these density changes is subjective if a geomagnetic storm persists simultaneously. The present case study addresses the ionospheric variations over the Indian longitudes under the combined effects of the solar flares and a geomagnetic storm during 6 to 8 September 2017 and probably the first of its kind in delineating the effects of these two over the low latitude ionosphere. The X9.3 class flare of 6 September, which occurred during non-storm conditions, produced an intense E region ionization (~500\% over the ambient). However, the total electron content response to this flare was comparatively weak. The flares on 7 and 8 September occurred during the 7\textendash8 September geomagnetic storm. Though the 8 September flare occurred with higher intensity (M8.1) and early in local time compared to the flare of 7 September (M7.3), the equatorial electrojet current enhancement was lesser on 8 September (~75\% over the ambient) than that of 7 September (~110\% over the ambient). This aspect is discussed in view of the storm time convection effects over the low latitudes during 7\textendash8 September storm. The total electron content did not respond to the flares of 7 and 8 September. This behavior is attributed to the varying center-to-limb distance of the solar active region 12673 during this period.

Bagiya, Mala; Thampi, Smitha; Hui, Debrup; Sunil, A.; Chakrabarty, D.; Choudhary, R.;

Published by: Journal of Geophysical Research: Space Physics Published on: 08/2018

YEAR: 2018 DOI: 10.1029/2018JA025496

Storm Time Variation of Radiative Cooling by Nitric Oxide as Observed by TIMED-SABER and GUVI

The variation of O/N₂ (reference to N₂ column density 10¹⁷\ cm^-2) and nitric oxide radiative emission flux exiting the thermosphere have been studied over the Northern Hemisphere during the superstorm event of 7\textendash12 November 2004. The data have been obtained from Global Ultraviolet Imager (GUVI) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on board the National Aeronautics and Space Administration (NASA)\textquoterights Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite. The NO radiative flux is observed to show an anti-correlation with O/N₂ on a global scale. Both NO radiative flux and O/N₂ ratio show equatorward motion with maximum penetration in western longitude sectors. A local variation of O, O₂, and N₂ densities have been calculated using NRLMSISE-00 model over a midlatitude location (55\textdegreeN,180\textdegreeE). On a local scale, model calculated O/O₂ and O/N₂ ratios are found to follow the observations made by GUVI. The collisional excitation of NO with atomic oxygen is the most dominant process for the total cooling rate. The SABER-retrieved NO cooling rate (CR) at a local site suggests an enhancement during the storm period with the peak emission rate closely correlated to the progression of the storm. The peak emission altitude of NO CR moves upward during the main phase of the storm. The NO abundance has been calculated by using cooling rate and Nitric Oxide Empirical Model (NOEM) model. Both these suggest a vary large (3\textendash15 times) increase in NO density during the storm, which is required to account the changes in NO radiative flux. A similar kind of enhancement in NO abundance is also noticed in Student Nitric Oxide Explorer observations during intense geomagnetic storms.

Bharti, Gaurav; Sunil~Krishna, M.; Bag, T.; Jain, Puneet;

Published by: Journal of Geophysical Research: Space Physics Published on: 01/2018

YEAR: 2018 DOI: 10.1002/2017JA024576

Initial Observations with the Ionospheric Photometer on the Chinese Feng Yun 3D Satellite

Mao, Tian; Fu, Liping; Wang, Yungang; Jiang, Fang; Hu, Xiuqing; Zhang, Xiaoxin; Sun, Lingfeng;

Published by: Published on:

YEAR: 2018 DOI:

The statistic characteristics of HF Oblique Sounding Channel at mid and low latitude during ionospheric disturbance time

In this study, historical data MOFF from two HF propagation paths: Qingdao-Lanzhou and Guangzhou-Haikou at mid and low latitude, the midpoint referenced data are from two

Wang, Fei-Fei; Liu, Yu-Mei; Sun, Shu-Ji;

Published by: Published on:

YEAR: 2018 DOI: 10.1109/ISAPE.2018.8634091

2017

Dawn-Dusk Asymmetries in Mercury’s Magnetosphere

This chapter offers a review of dawn‐dusk asymmetries in Mercury’s magnetosphere. Five years’ of data collected by the MESSENGER spacecraft have revealed many intriguing

Sundberg, Torbjörn;

Published by: Dawn-Dusk Asymmetries in Planetary Plasma Environments Published on:

YEAR: 2017 DOI:

2016

Direct observational evidence for disturbance dynamo on the daytime low-latitude ionosphere: A case study based on the 28 June 2013 space weather event

A case of the westward disturbance dynamo (DD) electric field, influencing the daytime equatorial and low-latitude ionosphere, during a geomagnetic storm that occurred on 28\textendash29 June 2013 is presented. The GPS total electron content (TEC) observations from a network of stations in the Indian equatorial, low and middle latitude regions along with the radio beacon TEC, ionosonde, and magnetic field observations are used to study the storm time behavior of the ionosphere. Negative ionospheric storm effects were seen over the low and middle latitudes during the storm time due to the presence of a westward DD electric field. Observations show that the suppression of the equatorial ionization anomaly (EIA) from the morning hours itself on 29 June 2013 took place due to the prevailing westward DD electric field, providing evidence for the model calculations by Balan et al. (2013). Simulations using the GITM model also agree well with our results. The present study gains importance as the direct observational evidences for disturbance dynamo effects on the daytime low-latitude ionosphere and the EIA are sparse, as it has been difficult to delineate it from the compositional disturbances.

Thampi, Smitha; Shreedevi, P.; Choudhary, R.; Pant, Tarun; Chakrabarty, D.; Sunda, S.; Mukherjee, S.; Bhardwaj, Anil;

Published by: Journal of Geophysical Research: Space Physics Published on: 09/2016

YEAR: 2016 DOI: 10.1002/2016JA023037

Coherent seasonal, annual, and quasi-biennial variations in ionospheric tidal/SPW amplitudes

In this study, we examine the coherent spatial and temporal modes dominating the variation of selected ionospheric tidal and stationary planetary wave (SPW) signatures from 2007 to 2013 FORMOSAT-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) total electron content observations using multidimensional ensemble empirical mode decomposition (MEEMD) from the Hilbert-Huang Transform. We examine the DW1, SW2, DE3, and SPW4 components, which are driven by a variety of in situ and vertical coupling sources. The intrinsic mode functions (IMFs) resolved by MEEMD analysis allows for the isolation of the dominant modes of variability for prominent ionospheric tidal/SPW signatures in a manner not previously used, allowing the effects of specific drivers to be examined individually. The time scales of the individual IMFs isolated for all tidal/SPW signatures correspond to a semiannual variation at equatorial ionization anomaly (EIA) latitudes maximizing at the equinoxes, as well as annual oscillations at the EIA crests and troughs. All tidal/SPW signatures show one IMF isolating an ionospheric quasi-biennial oscillation (QBO) in the equatorial latitudes maximizing around January of odd-numbered years. This total electron content QBO variation is in phase with a similar QBO variation isolated in both the Global Ultraviolet Imager (GUVI) zonal mean column O/N₂ density ratio (ΣO/N₂) and the F_10.7 solar radio flux index around solar maximum, while showing temporal variation more similar to that of GUVI ΣO/N₂ during the time around the 2008/2009 extended solar minimum. These results point to both quasi-biennial variations in solar irradiance and thermosphere/ionosphere composition as a generation mechanism for the ionospheric QBO.

Chang, Loren; Sun, Yan-Yi; Yue, Jia; Wang, Jack; Chien, Shih-Han;

Published by: Journal of Geophysical Research: Space Physics Published on: 07/2016

YEAR: 2016 DOI: 10.1002/2015JA022249

Sparse Hierarchical Nonparametric Bayesian learning for light field representation and denoising

In this paper, we present a sparse hierarchical non-parametric Bayesian (SHNB) model, which is used to represent the data captured by the light field cameras. Specifically, a light field can be represented as a set of sub-aperture views. In order to capture the visual variations of these viewpoints, we propose the so-called \textquotedblleftdepth flow\textquotedblright features. Then based on the depth flow features, we model these views statistically with a sparse representation in a fully unsupervised manner. While local dictionaries are learned based on each sub-aperture view, all the views with different perspectives share one global dictionary. To show the effectiveness of the proposed model, we apply our model to denoise the light field data. In the experiments, we demonstrate that our method outperforms several state-of-the-art light field denoising approaches.

Sun, Xing; Meng, Nan; Xu, Zhimin; Lam, Edmund; So, Hayden;

Published by: Published on:

YEAR: 2016 DOI: 10.1109/IJCNN.2016.7727617

2015

A case study of ionospheric storm effects in the Chinese sector during the October 2013 geomagnetic storm

In this study, we investigate the ionospheric storm effects in the Chinese sector during 2 October 2013 geomagnetic storm. The TEC map over China sector (1\textdegree\ \texttimes\ 1\textdegree) and eight ionosondes data along the longitude of 110\textdegreeE are used to show significant positive ionospheric phases (enhancements in TEC and ionospheric peak electron density NmF2) in the high-middle latitude region and the negative effects at the low latitude and equatorial region during the storm. A wave structure with periods about 1\textendash2\ h and horizontal speed about 680\ m/s, propagating from the high latitudes to the low latitudes is observed in electron densities within the height region from 200 to 400\ km, which is caused by the combined effects of neutral wind and the large-scale traveling disturbances (LSTIDs). In the low latitude regions, compared with those in the quiet day, the ionospheric peak heights of the F2 layer (hmF2) in the storm day obviously increase accompanying a notably decrease in TEC and NmF2, which might be as a result of the eastward prompt penetration electric field (PPEF) evidenced by the two magnetometers and the subsequent westward disturbance dynamo electric fields (DDEF). The storm-time TEC enhancement mainly occurs in the topside ionosphere, as revealed from the topside TEC, bottomside TEC and GPS TEC.

Mao, Tian; Sun, Lingfeng; Hu, Lianhuan; Wang, Yungang; Wang, Zhijun;

Published by: Advances in Space Research Published on: 06/2015

YEAR: 2015 DOI: 10.1016/j.asr.2015.05.045

Ionospheric storm; Neutral wind; LSTIDs; PPEF; DDEF

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

2014

Effects of prolonged southward interplanetary magnetic field on low-latitude ionospheric electron density

The present work describes the low-latitude ionospheric variability during an unusually prolonged (~33 h) geomagnetically disturbed condition that prevailed during 15\textendash16 July 2012. The low-latitude electron density in summer hemisphere, investigated using ground- and satellite-based observations, responded to this by generating strong negative ionospheric storm on 16 July. The maximum electron density on 16 July over Indian low latitudes was reduced by more than 50\% compared to that on a geomagnetically quiet day (14 July 2012). In contrast to the extreme reduction in total electron content (TEC) in the Northern Hemisphere, TEC from a winter hemispheric station revealed substantial (~23 total electron content unit, 1 TECU = 10¹⁶ el m^-2) enhancements on the same day. This contrasting hemispherical response in TEC is suggested to be due to the combined effects of strong interhemispheric and solar-driven day-night winds. Further, very weak equatorial electrojet (EEJ) strength on 16 July indicated that the westward electric field perturbations in the low-latitude ionosphere were possibly due to the disturbance dynamo effect associated with meridional circulation from polar to equatorial latitudes. Interestingly, despite reduction in the integrated EEJ strength on 15 July, the low-latitude electron density showed substantial enhancement, highlighting the significant effect of the positive ionospheric storm on the low-latitude ionosphere. The roles of electrodynamical/neutral-dynamical and compositional disturbances are discussed in view of these observations to understand low-latitude ionospheric response when geomagnetic disturbance persists for longer duration.

Bagiya, Mala; Hazarika, Rumajyoti; Laskar, Fazlul; Sunda, Surendra; Gurubaran, S.; Chakrabarty, D.; Bhuyan, P.; Sridharan, R.; Veenadhari, B.; Pallamraju, D.;

Published by: Journal of Geophysical Research: Space Physics Published on: 07/2014

YEAR: 2014 DOI: 10.1002/2014JA020156

low-latitude ionosphere; neutral winds; prolonged southward IMF Bz; thermospheric neutral composition

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:

YEAR: 2014 DOI:

2013

Storm time spatial variations in TEC during moderate geomagnetic storms in extremely low solar activity conditions (2007--2009) over Indian region

The total electron content (TEC) measurements from a network of GPS receivers were analyzed to investigate the storm time spatial response of ionosphere over the Indian longitude sector. The GPS receivers from the GPS Aided Geo Augmented Navigation (GAGAN) network which are uniquely located around the \~77\textdegreeE longitude are used in the present study so as to get the complete latitudinal coverage from the magnetic equator to low mid-latitude region. We have selected the most intense storms but of moderate intensity (-100\ nT\ \<\ Dst\ \<\ -50\ nT) which occurred during the unusually extremely low solar activity conditions in 2007\textendash2009. Though the storms are of moderate intensity, their effects on equatorial to low mid-latitude ionosphere are found to be very severe as TEC deviations are more than 100\% during all the storms studied. Interesting results in terms of spatial distribution of positive/negative effects during the main/early recovery phase of storms are noticed. The maximum effect was observed at crest region during two storms whereas another two storms had maximum effect near the low mid-latitude region. The associated mechanisms like equatorial electrodynamics and neutral dynamics are segregated and explained using the TIMED/GUVI and EEJ data during these storms. The TEC maps are generated to investigate the storm time development/inhibition of equatorial ionization anomaly (EIA).

Sunda, Surendra; Vyas, B.M.; Khekale, P.V.;

Published by: Advances in Space Research Published on: 07/2013

YEAR: 2013 DOI: 10.1016/j.asr.2013.03.006

Electrodynamics; Equatorial and low-latitude; geomagnetic storm; Total electron content (TEC)

Ground-based GPS observation of SED-associated irregularities over CONUS

\ It has been known that steep total electron content (TEC) gradients observed at the boundary between the storm-enhanced plasma density (SED) and the low TEC region at subauroral and midlatitude regions are associated with ionospheric irregularities that impact communication and navigation systems. However, the relationship between the SED-associated irregularities and TEC gradients is still not well understood, partly because of the difficulties of resolving small-scale TEC gradients from sparsely distributed TEC observations. In this study, we examine the relationship between the SED-associated irregularities and TEC gradients during the intense geomagnetic storms of 31 March 2001 and 30 October 2003. To explore this relationship, TEC maps over the continental United States (CONUS) were constructed from ground-based GPS TEC observations, using Kalman filter update formulae with a recently developed nonstationary wavelet-based covariance model that enables resolution of TEC structures on both large and finer scales. Our results show that intense TEC gradients and ion drifts are thought to be required conditions for the formation of irregularities on the northeast side of the SED. Additionally, our methodology identified the narrow east-west stretch of TEC enhancement within the midlatitude low TEC region on 30 October 2003, and this TEC enhancement is most likely to be caused by auroral precipitation.

Sun, Yang-Yi; Matsuo, Tomoko; Araujo-Pradere, Eduardo; Liu, Jann-Yenq;

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

YEAR: 2013 DOI: 10.1029/2012JA018103

data assimilation; irregularity; nonstationary covariance; SED; TEC gradient

2010

Artificial plasma cave in the low-latitude ionosphere results from the radio occultation inversion of the FORMOSAT-3/COSMIC

Liu, J; Lin, C; Lin, C.; Tsai, H.; Solomon, S.; Sun, Y; Lee, I.; Schreiner, W.; Kuo, Y.;

Published by: Journal of Geophysical Research Published on: Jan-01-2010

YEAR: 2010 DOI: 10.1029/2009JA015079

Coordinated study of coherent radar backscatter and optical airglow depletions in the central Pacific

Miller, E.; Makela, J.; Groves, K.; Kelley, M.; Tsunoda, R.;

Published by: Journal of Geophysical Research Published on: Jan-01-2010