scholarly journals Large‐Scale Ducting of Pc1 Pulsations Observed by Swarm Satellites and Multiple Ground Networks

2018 ◽  
Vol 45 (23) ◽  
Author(s):  
Hyangpyo Kim ◽  
Junga Hwang ◽  
Jaeheung Park ◽  
Yukinaga Miyashita ◽  
Kazuo Shiokawa ◽  
...  
Keyword(s):  
Large Scale ◽  
Swarm Satellites ◽  
Pc1 Pulsations

scholarly journals Ionosonde Observations of Spread F and Spread Es at Low and Middle Latitudes during the Recovery Phase of the 7–9 September 2017 Geomagnetic Storm

2021 ◽  
Vol 13 (5) ◽  
pp. 1010
Author(s):  
Lehui Wei ◽  
Chunhua Jiang ◽  
Yaogai Hu ◽  
Ercha Aa ◽  
Wengeng Huang ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Large Scale ◽  
Satellite System ◽  
Recovery Phase ◽  
Ionospheric Irregularities ◽  
Middle Latitudes ◽  
Multiple Observations ◽  
Swarm Satellites ◽  
Spread F ◽  
Global Navigation Satellite

This study presents observations of nighttime spread F/ionospheric irregularities and spread Es at low and middle latitudes in the South East Asia longitude of China sectors during the recovery phase of the 7–9 September 2017 geomagnetic storm. In this study, multiple observations, including a chain of three ionosondes located about the longitude of 100°E, Swarm satellites, and Global Navigation Satellite System (GNSS) ROTI maps, were used to study the development process and evolution characteristics of the nighttime spread F/ionospheric irregularities at low and middle latitudes. Interestingly, spread F and intense spread Es were simultaneously observed by three ionosondes during the recovery phase. Moreover, associated ionospheric irregularities could be observed by Swarm satellites and ground-based GNSS ionospheric TEC. Nighttime spread F and spread Es at low and middle latitudes might be due to multiple off-vertical reflection echoes from the large-scale tilts in the bottom ionosphere. In addition, we found that the periods of the disturbance ionosphere are ~1 h at ZHY station, ~1.5 h at LSH station and ~1 h at PUR station, respectively. It suggested that the large-scale tilts in the bottom ionosphere might be produced by LSTIDs (Large scale Traveling Ionospheric Disturbances), which might be induced by the high-latitude energy inputs during the recovery phase of this storm. Furthermore, the associated ionospheric irregularities observed by satellites and ground-based GNSS receivers might be caused by the local electric field induced by LSTIDs.

Preliminary monthly gravity field models from kinematic orbits of SWARM Satellites

2021 ◽  
Author(s):  
Xingfu Zhang ◽  
Qiujie Chen ◽  
Yunzhong Shen
Keyword(s):  
Gravity Field ◽  
Large Scale ◽  
Earth System ◽  
The Earth ◽  
Swarm Satellites ◽  
Variable Gravity ◽  
Data Gap ◽  
One Year ◽  
Gravity Recovery ◽  
Gravity Field Models

<p>      Although the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE FO) satellite missions play an important role in monitoring global mass changes within the Earth system, there is a data gap of about one year spanning July 2017 to May 2018, which leads to discontinuous gravity observations for monitoring global mass changes. As an alternative mission, the SWARM satellites can provide gravity observations to close this data gap. In this paper, we are dedicated to developing alternative monthly time-variable gravity field solutions from SWARM data. Using kinematic orbits of SWARM from ITSG for the period January 2015 to September 2020, we have generated a preliminary time series of monthly gravity field models named Tongji-Swarm2019 up to degree and order 60. The comparisons between Tongji-Swarm2019 and GRACE/GRACE-FO monthly solutions show that Tongji-Swarm2019 solutions agree with GRACE/GRACE-FO models in terms of large-scale mass change signals over amazon, Greenland and other regions. We can conclude that Tongji-Swarm2019 monthly gravity field models are able to close the gap between GRACE and GRACE FO.</p>

scholarly journals SLR, GRACE and Swarm Gravity Field Determination and Combination

2019 ◽  
Vol 11 (8) ◽  
pp. 956 ◽  
Author(s):  
Ulrich Meyer ◽  
Krzysztof Sosnica ◽  
Daniel Arnold ◽  
Christoph Dahle ◽  
Daniela Thaller ◽  
...  
Keyword(s):  
Mass Transport ◽  
Gravity Field ◽  
Large Scale ◽  
Mass Gain ◽  
Normal Equation ◽  
Polar Regions ◽  
Swarm Satellites ◽  
Gravity Fields ◽  
Long Time ◽  
Gravity Field Determination

Satellite gravimetry allows for determining large scale mass transport in the system Earth and to quantify ice mass change in polar regions. We provide, evaluate and compare a long time-series of monthly gravity field solutions derived either by satellite laser ranging (SLR) to geodetic satellites, by GPS and K-band observations of the GRACE mission, or by GPS observations of the three Swarm satellites. While GRACE provides gravity signal at the highest spatial resolution, SLR sheds light on mass transport in polar regions at larger scales also in the pre- and post-GRACE era. To bridge the gap between GRACE and GRACE Follow-On, we also derive monthly gravity fields using Swarm data and perform a combination with SLR. To correctly take all correlations into account, this combination is performed on the normal equation level. Validating the Swarm/SLR combination against GRACE during the overlapping period January 2015 to June 2016, the best fit is achieved when down-weighting Swarm compared to the weights determined by variance component estimation. While between 2014 and 2017 SLR alone slightly overestimates mass loss in Greenland compared to GRACE, the combined gravity fields match significantly better in the overlapping time period and the RMS of the differences is reduced by almost 100 Gt. After 2017, both SLR and Swarm indicate moderate mass gain in Greenland.

Large-scale irregularities of the winter polar topside ionosphere according to data from Swarm satellites

2017 ◽  
Vol 55 (6) ◽  
pp. 436-445 ◽  
Author(s):  
R. Yu. Lukianova ◽  
Sh. R. Bogoutdinov
Keyword(s):  
Large Scale ◽  
Topside Ionosphere ◽  
Swarm Satellites

scholarly journals Plasma patches inside the polar cap and auroral oval: the impact on the spaceborne GPS receiver

2019 ◽  
Vol 9 ◽  
pp. A25 ◽  
Author(s):  
Chao Xiong ◽  
Fan Yin ◽  
Xiaomin Luo ◽  
Yaqi Jin ◽  
Xin Wan
Keyword(s):  
Large Scale ◽  
Magnetic Measurements ◽  
Auroral Oval ◽  
Lower Latitude ◽  
Small Scale ◽  
Gps Receiver ◽  
Polar Cap ◽  
Cusp Region ◽  
Swarm Satellites ◽  
The Impact

In this study, we focus on plasma patches with very dense plasma in the southern hemisphere during the main phase of 2015 St. Patrick’s Day storm. With in situ electron densities exceeding 1.5 × 1012 m−3 at 450–500 km altitude, the patches cause strong signal outages of the global positioning system (GPS) receivers on board Swarm satellites. By using the field-aligned currents derived from the Swarm magnetic measurements, we determined whether the satellites fly inside the auroral oval or not. Different influences on the spaceborne GPS receiver are seen when these patches are located at different latitude regions, e.g., inside the polar cap or auroral oval. The simultaneously measurements of 2 Hz electron density as well as 50 Hz magnetic signatures from Swarm show that when large-scale polar cap patches transported from dayside lower latitude entering the cusp region, irregularities with much finer scale-size are generated; associated with various instabilities inside the cusp region, the small-scale irregularities cause much more severe influence on the GPS signals. This is the first direct evidence to show that when plasma patches are located inside the cusp region, the spaceborne receiver experiences stronger outage of GPS signals.

scholarly journals Statistical Approach to Observe the Atmospheric Density Variations Using Swarm Satellite Data

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 897
Author(s):  
Md Wahiduzzaman ◽  
Alea Yeasmin ◽  
Jing-Jia Luo ◽  
Md. Arfan Ali ◽  
Muhammad Bilal ◽  
...  
Keyword(s):  
Correlation Coefficient ◽  
Large Scale ◽  
Density Measurement ◽  
Atmospheric Density ◽  
Physical Mechanisms ◽  
Swarm Satellites ◽  
Atmospheric Density Models ◽  
Swarm Satellite ◽  
Level 2 ◽  
Medium Correlation

Over time, the initial algorithms to derive atmospheric density from accelerometers have been significantly enhanced. In this study, we discussed one of the accurate accelerometers—the Earth’s Magnetic Field and Environment Explorers, more commonly known as the Swarm satellites. Swarm satellite–C level 2 (measurements from the Swam accelerometers) density, solar index (F10.7), and geomagnetic index (Kp) data have been used for a year (mid 2014–2015), and the different types of temporal (the diurnal, multi–day, solar–rotational, semi–annual, and annual) atmospheric density variations have been investigated using the statistical approaches of correlation coefficient and wavelet transform. The result shows the density varies due to the recurrent geomagnetic force at multi–day, solar irradiance during the day, appearance and disappearance of the Sun’s active region, Sun–Earth distance, large scale circulation, and the formation of an aurora. Additionally, a correlation coefficient was used to observe whether F10.7 or Kp contributes strongly or weakly to annual density, and the result found a strong (medium) correlation with F10.7 (Kp). Accurate density measurement can help to reduce the model’s bias correction, and monitoring the physical mechanisms for the density variations can lead to improvements in the atmospheric density models.

Longitudinal Gradients in Field-Aligned Currents as Observed by Swarm

2020 ◽  
Author(s):  
Octav Marghitu ◽  
Adrian Blăgău ◽  
Joachim Vogt
Keyword(s):  
Large Scale ◽  
Present Report ◽  
Longitudinal Direction ◽  
Auroral Oval ◽  
Activity Level ◽  
Magnetic Field Data ◽  
Swarm Satellites ◽  
Longitudinal Gradients ◽  
Operational Phase ◽  
Auroral Arcs

<p>Field-aligned currents (FACs) are closely related to aurora and a key component of the magnetosphere-ionosphere-thermosphere system. Large scale FAC structures, like Region 1 / Region 2, threading the whole auroral oval, as well as smaller scale FACs, associated with auroral arcs, are often assumed to consists of upward / downward current sheet pairs, uniform in longitudinal direction. While such a uniformity is consistent with the prevalent 1D symmetry of the auroral arcs and oval, longitudinal gradients may develop at times, for example when the 1D symmetry prepares to break, during the growth phase of auroral substorms. The Swarm mission provides optimum conditions to explore systematically longitudinal gradients in FACs, namely a proper spacecraft configuration, with the Swarm A / Swarm C pair lining up periodically with Swarm B at auroral latitudes, and high quality magnetic field data. The present report concentrates on a set of auroral events observed by the Swarm satellites, in this suitable configuration, during the first six months of the mission operational phase. At that time, the distance between Swarm A / Swarm C and Swarm B was in the range of a few 100 km, comparable to the length scale of electrojet currents associated with auroral arcs. Not surprising, longitudinal gradients in FACs are occasionally significant, a feature which is discussed with respect to the location, activity level, and substorm phase of the event.</p>

Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

1999 ◽  
Vol 173 ◽  
pp. 243-248
Author(s):  
D. Kubáček ◽  
A. Galád ◽  
A. Pravda
Keyword(s):  
Image Processing ◽  
Large Scale ◽  
Harvard College ◽  
Oak Ridge ◽  
Large Scale Structures ◽  
Short Period Comet ◽  
Short Period ◽  
Scale Structures ◽  
Harvard College Observatory ◽  
Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

Large-scale Motion of Solar Filaments

2000 ◽  
Vol 179 ◽  
pp. 205-208
Author(s):  
Pavel Ambrož ◽  
Alfred Schroll
Keyword(s):  
Magnetic Flux ◽  
Proper Motion ◽  
Time Scale ◽  
Large Scale ◽  
Accuracy Of Measurements ◽  
Solar Filaments ◽  
General Movement ◽  
Scale Motion ◽  
Velocity Scatter

AbstractPrecise measurements of heliographic position of solar filaments were used for determination of the proper motion of solar filaments on the time-scale of days. The filaments have a tendency to make a shaking or waving of the external structure and to make a general movement of whole filament body, coinciding with the transport of the magnetic flux in the photosphere. The velocity scatter of individual measured points is about one order higher than the accuracy of measurements.

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