26 research outputs found
Climatology of Plasmaspheric Total Electron Content Obtained From Jason 1 Satellite
We used more than 40 million total electron content (TEC) measurements obtained from the GPS TurboRogue Space Receiver receiver on board the Jason 1 satellite in order to investigate the global morphology of the plasmaspheric TEC (pTEC) including the variations with local time, latitude, longitude, season, solar cycle, and geomagnetic activity. The pTEC corresponds to the total electron content between Jason 1 (1336âkm) and GPS (20,200âkm) satellite altitudes. The pTEC data were collected during the 7âyear period from January 2002 to December 2008. It was found that pTEC increases by about 10â30% from low to high solar flux conditions with the largest variations occurring at low latitudes for equinox. During low solar flux condition, pTEC is largely independent of geomagnetic activity. However, it slightly decreases with increasing geomagnetic activity at low latitudes during high solar flux. The seasonal variations such as the annual and semiannual anomalies in the ionosphere also exist in the low-latitude plasmasphere. In particular, the American sector (around 300°E) shows strong annual asymmetry in the plasmaspheric density, being larger in December than in June solstice
VHF meteor radar at King Sejong Station, Antarctica
Since 2002, we have been observing the mesosphere and lower thermosphere (MLT) region over King Sejong Station (KSS; 62.22°S, 58.78°W), Antarctica, using various instruments such as the Spectral Airglow Temperature Imager (SATI), All Sky Camera (ASC) and VHF meteor radar. The meteor radar, installed in March 2007, continuously measures neutral winds in the altitude region 70â110 km and neutral temperature near the mesopause 24 hâd-1, regardless of weather conditions. In this study, we present results of an analysis of the neutral wind data for gravity wave activity over the tip of the Antarctic Peninsula, where such activity is known to be very high. Also presented is temperature estimation from measurement of the decay times of meteor trails, which is compared with other temperature measurements from SATI and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere Ionosphere Mesosphere Energy and Dynamics (TIMED) satellite
Observations of the Polar Ionosphere by the Vertical Incidence Pulsed Ionospheric Radar at Jang Bogo Station, Antarctica
Korea Polar Research Institute (KOPRI) installed an ionospheric sounding radar system called Vertical Incidence Pulsed
Ionospheric Radar (VIPIR) at Jang Bogo Station (JBS) in 2015 in order to routinely monitor the state of the ionosphere in the
auroral oval and polar cap regions. Since 2017, after two-year test operation, it has been continuously operated to produce
various ionospheric parameters. In this article, we will introduce the characteristics of the JBS-VIPIR observations and
possible applications of the data for the study on the polar ionosphere. The JBS-VIPIR utilizes a log periodic transmit antenna
that transmits 0.5â25 MHz radio waves, and a receiving array of 8 dipole antennas. It is operated in the Dynasonde B-mode
pulse scheme and utilizes the 3-D inversion program, called NeXtYZ, for the data acquisition and processing, instead of the
conventional 1-D inversion procedure as used in the most of digisonde observations. The JBS-VIPIR outputs include the
height profiles of the electron density, ionospheric tilts, and ion drifts with a 2-minute temporal resolution in the bottomside
ionosphere. With these observations, possible research applications will be briefly described in combination with other
observations for the aurora, the neutral atmosphere and the magnetosphere simultaneously conducted at JBS
HLâTWiM Empirical Model of HighâLatitude Upper Thermospheric Winds
We present an empirical model of thermospheric winds (Highâlatitude Thermospheric Wind Model [HLâTWiM]) that specifies F region highâlatitude horizontal neutral winds as a function of day of year, latitude, longitude, local time, and geomagnetic activity. HLâTWiM represents the largeâscale neutral wind circulation, in geomagnetic coordinates, for the given input conditions. The model synthesizes the most extensive collection to date of historical highâlatitude wind measurements; it is based on statistical analyses of several decades of F region thermospheric wind measurements from 21 groundâbased stations (FabryâPerot Interferometers and Scanning Doppler Imaging FabryâPerot Interferometers) located at various northern and southern high latitudes and two spaceâbased instruments (UARS WINDII and GOCE). The geomagnetic latitude and local time dependences in HLâTWiM are represented using vector spherical harmonics, day of year and longitude variations are represented using simple harmonic functions, and the geomagnetic activity dependence is represented using quadratic B splines. In this paper, we describe the HLâTWiM formulation and fitting procedures, and we verify the model against the neutral wind databases used in its formulation. HLâTWiM provides a necessary benchmark for validating new wind observations and tuning our physical understanding of complex wind behaviors. Results show stronger Universal Time variation in winds at southern than northern high latitudes. Modelâdata intraâannual comparisons in this study show semiannual oscillationâlike behavior of GOCE winds, rarely observed before in wind data.Key PointsWe developed a comprehensive empirical model of highâlatitude F region thermospheric winds (HLâTWiM)Universal Time variations in highâlatitude winds are stronger in the Southern than Northern HemisphereHLâTWiM provides a necessary benchmark for validating new highâlatitude wind observations and tuning first principal modelsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153588/1/jgra55363_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153588/2/jgra55363-sup-0001-Figure_SI-S01.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153588/3/jgra55363.pd
Ground-based Observations of the Polar Region Space Environment
Jang Bogo Station (JBS), the second Korean Antarctic research station, was established in Terra Nova Bay, Antarctica (74.62°S
164.22°E) in February 2014 in order to expand the Korea Polar Research Institute (KOPRI) research capabilities. One of the
main research areas at JBS is space environmental research. The goal of the research is to better understand the general
characteristics of the polar region ionosphere and thermosphere and their responses to solar wind and the magnetosphere.
Ground-based observations at JBS for upper atmospheric wind and temperature measurements using the Fabry-Perot
Interferometer (FPI) began in March 2014. Ionospheric radar (VIPIR) measurements have been collected since 2015 to monitor
the state of the polar ionosphere for electron density height profiles, horizontal density gradients, and ion drifts. To investigate
the magnetosphere and geomagnetic field variations, a search-coil magnetometer and vector magnetometer were installed in
2017 and 2018, respectively. Since JBS is positioned in an ideal location for auroral observations, we installed an auroral all-sky
imager with a color sensor in January 2018 to study substorms as well as auroras. In addition to these observations, we are also
operating a proton auroral imager, airglow imager, global positioning system total electron content (GPS TEC)/scintillation
monitor, and neutron monitor in collaboration with other institutes. In this article, we briefly introduce the observational
activities performed at JBS and the preliminary results of these observations
Recommended from our members
Review of Environmental Monitoring by Means of Radio Waves in the Polar Regions: From Atmosphere to Geospace
The Antarctic and Arctic regions are Earth's open windows to outer space. They provide unique opportunities for investigating the troposphereâthermosphereâionosphereâplasmasphere system at high latitudes, which is not as well understood as the mid- and low-latitude regions mainly due to the paucity of experimental observations. In addition, different neutral and ionised atmospheric layers at high latitudes are much more variable compared to lower latitudes, and their variability is due to mechanisms not yet fully understood. Fortunately, in this new millennium the observing infrastructure in Antarctica and the Arctic has been growing, thus providing scientists with new opportunities to advance our knowledge on the polar atmosphere and geospace. This review shows that it is of paramount importance to perform integrated, multi-disciplinary research, making use of long-term multi-instrument observations combined with ad hoc measurement campaigns to improve our capability of investigating atmospheric dynamics in the polar regions from the troposphere up to the plasmasphere, as well as the coupling between atmospheric layers. Starting from the state of the art of understanding the polar atmosphere, our survey outlines the roadmap for enhancing scientific investigation of its physical mechanisms and dynamics through the full exploitation of the available infrastructures for radio-based environmental monitoring
First observations of the McMurdo-South Pole oblique ionospheric HF channel
We present the first observations from a new low-cost oblique ionosonde located in Antarctica. The transmitter is located at McMurdo Station, Ross Island, and the receiver at AmundsenâScott Station, South Pole. The system was demonstrated successfully in March 2019, with the experiment yielding over 30â000 ionospheric echoes over a 2-week period. These data indicate the presence of a stable E layer and a sporadic and variable F layer with dramatic spread F of sometimes more than 500âkm (in units of virtual height). The most important ionospheric parameter, NmF2, validates well against the Jang Bogo Vertical Incidence Pulsed Ionospheric (VIPIR) ionosonde (observing more than 1000âkm away). GPS-derived TEC data from the Multi-Instrument Data Analysis Software (MIDAS) algorithm can be considered necessary but insufficient to predict 7.2âMHz propagation between McMurdo and the South Pole, yielding a true positive in 40â% of cases and a true negative in 73â% of cases. The success of this pilot experiment at a total grant cost of USDâ116â000 and an equipment cost of âŒâUSDâ15â000 indicates that a large multi-static network could be built to provide unprecedented observational coverage of the Antarctic ionosphere
Global Positioning System Total Electron Content Variation over King Sejong Station in Antarctic under the Solar Minimum Condition Between 2005 and 2009
The total electron content (TEC) using global positioning system (GPS) is analyzed to see the characteristics of ionosphere\ud
over King Sejong station (KSJ, geographic latitude 62°13âČ S, longitude 58° 47âČ W, corrected geomagnetic latitude 48°\ud
S) in Antarctic. The GPS operational ratio during the observational period between 2005 and 2009 is 90.1%. The annual\ud
variation of the daily mean TEC decreases from January 2005 to February 2009, but increase from the June 2009. In summer\ud
(December-February), the seasonal mean TEC values have the maximum of 26.2 ± 2.4 TEC unit (TECU) in 2005 and\ud
the minimum of 16.5 ± 2.8 TECU in 2009, and the annual differences decrease from 3.0 TECU (2005-2006) to 1.4 TECU\ud
(2008-2009). However, on November 2010, it significantly increases to 22.3 ± 2.8 TECU which is up to 5.8 TECU compared\ud
with 2009 in summer. In winter (June-August), the seasonal mean TEC slightly decreases from 13.7 ± 4.5 TECU in 2005\ud
to 8.9 ± 0.6 TECU in 2008, and the annual difference is constantly about 1.6 TECU, and increases to 10.3 ± 1.8 TECU in\ud
2009. The annual variations of diurnal amplitude show the seasonal features that are scattered in summer and the enhancements\ud
near equinoxes are apparent in the whole years. In contrast, the semidiurnal amplitudes show the disturbed\ud
annual peaks in winter and its enhancements near equinoxes are unapparent. The diurnal phases are not constant in\ud
winter and show near 12 local time (LT). The semidiurnal phases have a seasonal pattern between 00 LT and 06 LT. Consequently,\ud
the KSJ GPS TEC variations show the significant semidiurnal variation in summer from December to February\ud
under the solar minimum between 2005 and 2009. The feature is considered as the Weddell Sea anomaly of larger nighttime\ud
electron density than a daytime electron density that has been observed around the Antarctica peninsula
Ground-based Observations for the Upper Atmosphere at King Sejong Station, Antarctica
Since the operation of the King Sejong Station (KSS) started in Antarctic Peninsula in 1989, there have been continuous
efforts to perform the observation for the upper atmosphere. The observations during the initial period of the station
include Fabry-Perot Interferometer (FPI) and Michelson Interferometer for the mesosphere and thermosphere, which are
no longer in operation. In 2002, in collaboration with York University, Canada, the Spectral Airglow Temperature Imager
(SATI) was installed to observe the temperature in the mesosphere and lower thermosphere (MLT) region and it has still
been producing the mesopause temperature data until present. The observation was extended by installing the meteor
radar in 2007 to observe the neutral winds and temperature in the MLT region during the day and night in collaboration
with Chungnam National University. We also installed the all sky camera in 2008 to observe the wave structures in the MLT
region. All these observations are utilized to study on the physical characteristics of the MLT region and also on the wave
phenomena such as the tide and gravity wave in the upper atmosphere over KSS that is well known for the strong gravity
wave activity. In this article, brief introductions for the currently operating instruments at KSS will be presented with their
applications for the study of the upper atmosphere
Ionospheric Behaviors Over Korea Peninsula During the Super Geomagnetic Storm Using GPS Measurements
The super-geomagnetic storms called 2003 Halloween event globally occurred during
the period of 29 through 31 which are the following days when the solar flares of X18
class exploded on 28 October 2003. The S4 index from GPS signal strength and the
peak electron density (NmF2) from GPS tomography method are analyzed according
to the date. The occurrences of the cycle slip and scintillation in the GPS signals are 1,094 and 1,387 on 28 and 29 October, respectively and these values are higher than
604 and 897 on 30 and 31 October. These mean the ionospheric disturbances are
not always generated by the period of geomagnetic storm. Therefore, GPS S4 index
is useful to monitor the ionospheric disturbances. Behaviors of ionospheric electron
density estimated from GPS tomography method are analyzed with the date. At UT
= 18 hr, the maximum NmF2 is shown on 28 October. It agrees with NmF2 variation
measured from Anyang ionosonde, and the GPS signal are better condition on 30 and
31 October than 28 October. In conclusion, GPS signal condition is relation with
geomagnetic activities, and depend upon the variation of the electron density. We
will study the long-term data to examine the relationship between the GPS signal
quality and the electron density as the further works