Bibliography

Notice:

Clicking on the title will open a new window with all details of the bibliographic entry.
Clicking on the DOI link will open a new window with the original bibliographic entry from the publisher.
Clicking on a single author will show all publications by the selected author.
Clicking on a single keyword, will show all publications by the selected keyword.

Found 18 entries in the Bibliography.

Showing entries from 1 through 18

2022

Disappearance of the Polar Cap Ionosphere During Geomagnetic Storm on 11 May 2019

Multi-instrument data from Jang Bogo Station (JBS) in Antarctica were utilized to study ionospheric responses to the 11 May 2019 moderate geomagnetic storm. These include Vertical Incident Pulsed Ionospheric Radar (VIPIR)/Dynasonde, Fabry-Perot Interferometer (FPI), GPS vertical total electron content (vTEC), and magnetometer. The VIPIR/Dynasonde observed long-lasting (\textgreater11 hr) severe depletion of the electron density in the F-region ionosphere over JBS. During the depletion interval, GPS TEC also correspondingly decreased, FPI neutral temperature was significantly enhanced, and the polar magnetic field variations showed positive and negative excursions in the Y (east) and Z (vertical) components, respectively. GK-2 A satellite, located ∼2.5 hr west of JBS, observed negative magnetic field perturbations in the azimuthal BD component at geosynchronous orbit during the depletion of ionospheric plasma. Such a BD perturbation at geosynchronous orbit is due to the field-aligned currents flowing out of the ionosphere. From these observations we suggest that transpolar ionospheric currents connected to the field-aligned currents flowing on a substorm wedge-shaped circuit act as a source of polar atmospheric heating during the moderate geomagnetic storm interval and that elevated heavy molecular gases (O2 and N2) by atmospheric heating contribute to the electron density depletion via increased recombination rate.

Kwon, H.-J.; Kim, K.-H.; Jee, G.; Seon, J.; Lee, C.; Ham, Y.-B.; Hong, J.; Kim, E.; Bullett, T.; Auster, H.-U.; Magnes, W.; Kraft, S.;

Published by: Space Weather Published on:

YEAR: 2022 DOI: 10.1029/2022SW003054

2020

The Far Ultraviolet Signatures of Conjugate Photoelectrons Seen by the Special Sensor Ultraviolet Spectrographic Imager

This study investigates the origin of anomalous far ultraviolet emissions observed at night at the subauroral region by the Special Sensor Ultraviolet Spectrographic Imager on board the Defense Meteorological Satellite System-F16 satellite. The global distribution of the anomalous emission is derived using the measurements of the oxygen atom 130.4-nm emission in 2017. Our results show the extension of the anomalous emission from high latitudes to middle latitudes in the Northern American-Atlantic sector during the December solstice and in the Southern Australia-New Zealand sector during the June solstice. These observations indicate that the anomalous emission occurs in the winter hemisphere and is pronounced at locations close to the magnetic poles. The good agreement between the morphology of the anomalous emission and the predicted distribution of conjugate photoelectrons leads to the conclusion that the anomalous emissions are the signatures of conjugate photoelectrons.

Kil, Hyosub; Schaefer, Robert; Paxton, Larry; Jee, Geonhwa;

Published by: Geophysical Research Letters Published on: 01/2020

YEAR: 2020 DOI: 10.1029/2019GL086383

conjugate photoelectron; far ultraviolet emission; thermosphere; remote sensing data

The far ultraviolet signatures of conjugate photoelectrons seen by the Special Sensor Ultraviolet Spectrographic Imager

Kil, Hyosub; Schaefer, Robert; Paxton, Larry; Jee, Geonhwa;

Published by: Geophysical Research Letters Published on:

YEAR: 2020 DOI:

2019

Plasma Blobs Associated With Medium-Scale Traveling Ionospheric Disturbances

Plasma blobs represent plasma density enhancements with respect to ambient plasma. The formation of blobs in low and middle latitudes is understood in association with either equatorial plasma bubbles or medium-scale traveling ionospheric disturbances (MSTIDs). This study reports four blob events identified from the Swarm satellite observations in 2014. Those blobs show the conjugate property and the alignment in the northwest-southeast direction in the Northern Hemisphere and southwest-northeast direction in the Southern Hemisphere. These are the typical characteristics of nighttime MSTIDs. The observation of MSTIDs in the total electron content maps and the absence of bubbles in the equatorial region at the times of the blob detection further support the association of those blobs with MSTIDs.

Kil, Hyosub; Paxton, Larry; Jee, Geonhwa; Nikoukar, Romina;

Published by: Geophysical Research Letters Published on: 03/2019

YEAR: 2019 DOI: 10.1029/2019GL082026

Plasma blobs associated with medium-scale traveling ionospheric disturbances

Kil, Hyosub; Paxton, Larry; Jee, Geonhwa; Nikoukar, Romina;

Published by: Geophysical Research Letters Published on:

YEAR: 2019 DOI:

Daytime evolution of equatorial plasma bubbles observed by the first Republic of China satellite

Kil, Hyosub; Paxton, Larry; Lee, Woo; Jee, Geonhwa;

Published by: Geophysical Research Letters Published on:

YEAR: 2019 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

On the latitudinal changes in ionospheric electrodynamics and composition based on observations over the 76--77 E meridian from both hemispheres during a geomagnetic storm

The relative contributions of the composition disturbances and the disturbance electric fields in the redistribution of ionospheric plasma is investigated in detail by taking the case of a long-duration positive ionospheric storm that occurred during 18\textendash21 February 2014. GPS total electron content (TEC) data from the Indian Antarctic station, Bharti (69.4\textdegreeS, 76.2\textdegreeE geographic), the northern midlatitude station Hanle (32.8\textdegreeN, 78.9\textdegreeE geographic), northern low-latitude station lying in the vicinity of the anomaly crest, Ahmedabad (23.04\textdegreeN, 72.54\textdegreeE geographic, dip latitude 17\textdegreeN), and the geomagnetic equatorial station, Trivandrum (8.5\textdegreeN, 77\textdegreeE geographic, dip latitude 0.01\textdegreeS) are used in the study. These are the first simultaneous observations of TEC from Bharti and Hanle during a geomagnetic storm. The impact of the intense geomagnetic storm (Dst\~-130\ nT) on the southern hemisphere high-latitude station was a drastic reduction in the TEC (negative ionospheric storm) starting from around 0330 Indian standard time (IST) on 19 February which continued till 21 February, the maximum reduction in TEC at Bharti being \~35 TEC units on 19 February. In the northern hemisphere midlatitude and equatorial stations, a positive ionospheric storm started on 19 February at around 0900 IST and lasted for 3\ days. The maximum enhancement in TEC at Hanle was about \~25 TECU on 19 February while over Trivandrum it was \~10 TECU. This long-duration positive ionospheric storm provided an opportunity to assess the relative contributions of disturbance electric fields and composition changes latitudinally. The results indicate that the negative ionospheric storm over Bharti and the positive ionospheric storm over Hanle are the effect of the changes in the global wind system and the storm-induced composition changes. At the equatorial latitudes, the positive ionospheric storm was due to the interplay of prompt penetration electric field and disturbance dynamo electric field.

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

Published by: Journal of Geophysical Research: Space Physics Published on: 02/2016

YEAR: 2016 DOI: 10.1002/2015JA021841

Geomagnetic storms; High latitude low latitude coupling; Ionosphere; positive ionospheric storm

Equatorial broad plasma depletions associated with the evening prereversal enhancement and plasma bubbles during the 17 March 2015 storm

Kil, Hyosub; Lee, Woo; Paxton, Larry; Hairston, Marc; Jee, Geonhwa;

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

YEAR: 2016 DOI:

2015

Dynamics of the Dayside Aurora as Viewed from the South Pole

McEwen, Donald; Sivjee, Gulamabas; Zhang, Yongliang;

Published by: Published on:

YEAR: 2015 DOI:

2014

A study on ionospheric scintillation near the EIA crest in relation to equatorial electrodynamics

Equatorial electrojet (EEJ) data, which are considered as a proxy index of equatorial electric field, are analyzed in conjunction with equatorial ionosonde, total electron content (TEC) and scintillation data near the equatorial ionization anomaly (EIA) crest for the equinoctial months of high solar activity years (2011\textendash2012) to identify any precursor index of postsunset evolution of equatorial electron density irregularities and subsequent occurrence of scintillation near the northern EIA crest. Only geomagnetically quiet and normal electrojet days are considered. The diurnal profiles of EEJ on the scintillation days exhibit a secondary enhancement in the afternoon to presunset hours following diurnal peaks. A series of electrodynamical processes conducive for generation of irregularities emerge following secondary enhancement of EEJ. Latitudinal profile of TEC exhibits resurgence in EIA structure around the postsunset period. Diurnal TEC profile near the EIA crest resembles postsunset secondary enhancement on the days with afternoon enhancement in EEJ. Occurrence of equatorial spread F and postsunset scintillation near the EIA crest seems to follow the secondary enhancement events in EEJ. Both the magnitude and duration of enhanced EEJ are found to be important for postsunset intensification of EIA structure and subsequent occurrence of equatorial irregularities. A critical value combining the two may be considered an important precursor for postsunset occurrence of scintillation near the EIA crest. The results are validated using archived data for the years 1989\textendash1990 and explained in terms of modulation effects of enhanced equatorial fountain.

Chatterjee, S.; Chakraborty, S.; Veenadhari, B.; Banola, S.;

Published by: Journal of Geophysical Research: Space Physics Published on: 02/2014

YEAR: 2014 DOI: 10.1002/2013JA019466

scintillations in relation to equatorial electrodynamics

2012

A long-lived band of plasma density enhancement at mid-latitudes during the 2003 Halloween magnetic storm

Park, Jaeheung; Lühra, Hermann; Jakowski, Norbert; Gerzen, Tatjana; Kil, Hyosub; Jee, Geonhwa; Xiong, Chao; Min, Kyoung; Noja, Max;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: Jan-05-2012

YEAR: 2012 DOI: 10.1016/j.jastp.2012.03.009

The source of the steep plasma density gradient in middle latitudes during the 11--12 April 2001 storm

A steep plasma density gradient has been observed in the middle-latitude F region during large geomagnetic storms. This phenomenon can be understood as a special form of the middle-latitude ionization trough (hereafter trough), but its causal linkage has not yet been clarified. We investigate the association of the steep density gradient and the trough by comparing their morphologies and occurrence locations using the satellite and ground observation data during the 11\textendash12 April 2001 storm. Steep density gradients are detected in the dusk sector at the equatorward edges of the aurora by the Defense Meteorological Satellite Program (DMSP) F13 spacecraft. The locations of the steep density gradients coincide with the locations of the ionospheric footprints of the plasmapause identified by the Imager for Magnetopause-to-Aurora Global Exploration satellite. These observations demonstrate that the steep density gradient is created at the typical location of the trough. However, the steep density gradient is not produced by the formation of an intense trough during the storm. The temporal evolution of the total electron content maps shows that the steep density gradient observed at dusk by DMSP is associated with the plasma density enhancement in the dayside and its corotation into the dusk sector. The severe plasma density enhancement in middle latitudes, in combination with the trough and presumably the plasma depletion in high latitudes by the neutral composition change, produces the steep density gradient in the subauroral region during the storm.

Park, S.; Kim, K.-H.; Kil, H.; Jee, G.; Lee, D.-H.; Goldstein, J.;

Published by: Journal of Geophysical Research Published on: 05/2012

YEAR: 2012 DOI: 10.1029/2011JA017349

geomagnetic storm; plasma trough; steep density gradient

2010

Mid-latitude ionosphere observed by ground-based GPS during intense geomagnetic storms in October 2003 and November 2004

Chung, J; Jee, Geonhwa;

Published by: Published on:

YEAR: 2010 DOI:

Extreme Enhancements in GPS TEC on 8 and 10 November 2004

Chung, Jong-Kyun; Jee, Gun-Hwa; Kim, Eo-Jin; Kim, Yong-Ha; Cho, Jung-Ho;

Published by: Bulletin of the Korean Space Science Society Published on: