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 0.5–25 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.
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Assessment of Polar Ionospheric Observations by VIPIR/Dynasonde at Jang Bogo Station, Antarctica: Part 1—Ionospheric Densities
Vertical incidence pulsed ionospheric radar (VIPIR) has been operated to observe the polar ionosphere with Dynasonde analysis software at Jang Bogo Station (JBS), Antarctica, since 2017. The JBS-VIPIR-Dynasonde (JVD) provides ionospheric parameters such as the height profile of electron density with NmF2 and hmF2, the ion drift, and the ionospheric tilt in the bottomside ionosphere. The JBS (74.6°S, 164.2°E) is located in the polar cap, cusp, or auroral region depending on the geomagnetic activity and local time. In the present study, an initial assessment of JVD ionospheric densities is attempted by the comparison with GPS TEC measurements which are simultaneously obtained from the GPS receiver at JBS during the solar minimum period from 2017 to 2019. It is found that the JVD NmF2 and bottomside TEC (bTEC) show a generally good correlation with GPS TEC for geomagnetically quiet conditions. However, the bTEC seems to be less correlated with the GPS TEC with slightly larger spreads especially during the daytime and in summer, which seems to be associated with the characteristics of the polar ionosphere such as energetic particle precipitations and large density irregularities. It is also found that the Dynasonde analysis seems to show some limitations to handle these characteristics of the polar ionosphere and needs to be improved to produce more accurate ionospheric density profiles especially during disturbed conditions.
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- Award ID(s):
- 1643119
- NSF-PAR ID:
- 10332411
- Date Published:
- Journal Name:
- Remote Sensing
- Volume:
- 14
- Issue:
- 12
- ISSN:
- 2072-4292
- Page Range / eLocation ID:
- 2785
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract The ionospheric density displays hemispheric asymmetries in the polar region due to various hemispheric differences, for example, in the offset between geographic and geomagnetic poles and in the geomagnetic field strength. Using ground‐based ionospheric measurements from Vertical Incidence Pulsed Ionospheric Radar with Dynasonde analysis at Jang Bogo Station (JBS), Antarctica and from EISCAT Svalbard Radar (ESR) where both sites are located mostly in the polar cap, we investigate the hemispheric differences in the ionospheric density between the northern and southern hemispheres for geomagnetically quiet and solar minimum condition. The results are also compared with Thermosphere Ionosphere Electrodynamic Global Circulation Model (TIEGCM) simulations. The observations show larger density and stronger diurnal and seasonal variations at JBS in the southern hemisphere than at Svalbard in the northern hemisphere. The diurnal variations of the density peak height are also observed to be much larger at JBS. In both hemispheres, the ionospheric density is significantly reduced in winter due to the limited solar production at high geographic latitudes, but TIEGCM considerably overestimates winter density, which is even larger than summer density, especially in the northern hemisphere. Also existed are the differences in the equinoctial asymmetry between the observations and the simulations: the daytime F‐region density is observed to be larger in fall than in spring in both hemispheres, but TIEGCM shows the opposite. In general, most of the observed asymmetrical density are much weaker in the model simulation, which may result from lack of proper magnetospheric forcings and neutral dynamics in the model.
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Abstract We describe observations of a trend between the level of km‐scale irregularity activity and the amplitudes of medium‐scale traveling ionospheric disturbances (MSTIDs) at mid‐latitudes using data from December 2019 through June 2021. These include measurements of both heigh‐specific and vertically integrated quantities. Region‐specific, bottom‐side measurements were made with the dynasonde system near Wallops Island (WI) and included phase structure function parameters related to km‐scale irregularities as well as height‐specific tilts/density gradients, which are especially sensitive to MSTIDs. A complementary data set was derived from the nearby Deployable Low‐band Ionosphere and Transient Experiment (DLITE) array in southern Maryland. The DLITE array was used to measure the vertically integrated irregularity index,
C k L , via scintillometry of bright cosmic radio sources at 35 MHz. Transverse gradients in the line‐of‐sight total electron content (TEC) were also measured with DLITE using apparent shifts in the sources' sky positions. Relatively simple layer‐based models for the vertical distribution of km‐scale irregularities applied to dynasonde‐measured properties yielded results that correlated well with DLITE measurements ofC k L . Similarly, spectral analysis showed that fluctuation amplitudes of vertically integrated bottom‐side density gradients derived from dynasonde data were well correlated with DLITE TEC gradient measurements. A significant trend was found betweenC k L and TEC gradient MSTID amplitudes among DLITE‐based data as well as among the extrapolated dynasonde measurements. Additionally, within the bottom‐side F‐region, irregularity levels were found to be well correlated with fluctuation amplitudes for the tilt as measured with the WI dynasonde. -
The second Korean Antarctic station, Jang Bogo Station (JBS), Terra Nova Bay (74°37.4′S, 164°13.7′E), is operational since March 2014. A Fabry–Perot Interferometer (FPI) and Vertical Incidence Pulsed Ionospheric Radar (VIPIR) were installed in 2014 and 2015 respectively, for simultaneous observations of neutral atmosphere and ionosphere in the polar region. Neutral winds observed by FPI show typical diurnal and semi-diurnal variations at around 250 km and 87 km respectively. VIPIR observations for the ionosphere also show typical electron density distributions in the polar region. Unlike conventional ionospheric sounder, it can measure ionospheric tilts to provide horizontal gradients of electron density over JBS in addition to general ionospheric parameters from sounding observation. In this article, we briefly report the preliminary results of the observations for the neutral atmosphere and ionosphere in the polar cap region.more » « less
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Abstract Data from a network of high‐frequency (HF) beacons deployed in Peru are used to estimate the regional ionospheric electron density in a volume. Pseudorange, accumulated carrier phase, and signal power measurements for each of the 36 ray paths provided by the network at a 1 min cadence are incorporated in the estimates. Additional data from the Jicamarca incoherent scatter radar, the Jicamarca sounder, and GPS receivers can also be incorporated. The electron density model is estimated as the solution to a global optimization problem that uses ray tracing in the forward model. The electron density is parametrized in terms of B‐splines in the horizontal direction and generalized Chapman functions or related functions in the vertical. Variational sensitivity analysis has been added to the method to allow for the utilization of the signal power observable which gives additional information about the morphology of the bottomside F region as well as absorption including absorption in the D and E regions. The goal of the effort is to provide contextual information for improving numerical forecasts of plasma interchange instabilities in the postsunset F region ionosphere associated with equatorial spread F (ESF). Data from two ESF campaigns are presented. In one experiment, the HF data revealed the presence of a large‐scale bottomside deformation that seems to have led to instability under otherwise inauspicious conditions. In another experiment, gradual variations in HF signal power were found to be related to the varying shape of the bottomside F layer.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/rs14122785
