Investigating waves and instabilities in the auroral E region via multi-points in-situ from the SPIDER sounding rockets

2020 ◽  
Author(s):  
Gabriel Giono ◽  
Nickolay Ivchenko ◽  
Tima Sergienko
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Spatial Scales ◽  
Fluxgate Magnetometer ◽  
Langmuir Probes ◽  
Camera System ◽  
Plasma Properties ◽  
Global Comparison ◽  
Free Falling

<p>On February 2<sup>nd</sup> 2016 the SPIDER sounding rocket released ten Free Falling Units (FFUs) inside an active westward-travelling auroral electrojet (between 100 to 120 km altitude). Each FFUs carried four electric field probes and four Langmuir probes, respectively on 2 and 1-meter wire booms, as well as a 3-axis fluxgate magnetometer, a gyroscope, an accelerometer and a GPS recorder. The main scientific objective of the project was to study waves and instabilities on various spatial scales, in particular the Farley-Buneman instability, as well as providing an in-situ picture of plasma properties inside the aurora.</p><p>Six FFUs were successfully recovered after landing and, despite some mechanical issues on some units, the recorded data showed promising results. Some of these results will be discussed in this presentation, namely (i) the electron density and temperature profiles from two FFUs compared to the incoherent scatter radar measurements from the EISCAT facility, (ii) the hints of different turbulence regimes along the flight seen in the electron density, (iii) the search for Farley-Buneman instability in the electric field data via wavelet analysis, (iv) the observation of electric field waves propagating between two FFUs and the comparison with ground-based observation of the aurora from the ALIS multi-camera system, and finally (v) a global comparison between perturbations seen in the electric field, magnetic field and plasma density and temperature on two FFUs.</p><p>These results demonstrated the potential of multi-point in-situ measurements for understanding multi-scale processes in auroras, and preliminary results from the reflight of the rocket to be happening in February 2020 will also be briefly presented.</p>

Analysis of Swarm Electric Field Data in View of Tsunami Events and related Earthquakes

2020 ◽  
Author(s):  
Wojciech Jarmolowski ◽  
Pawel Wielgosz ◽  
Anna Krypiak-Gregorczyk ◽  
Beata Milanowska
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Electron Content ◽  
Langmuir Probes ◽  
Time And Space ◽  
Total Electron ◽  
Swarm Satellites ◽  
High Orbit ◽  
Orbital Height

<p>Three Swarm satellites are equipped with Langmuir Probes (LP) measuring in-situ electron density of Earth electric field and POD GNSS receivers determining topside total electron content (TEC) in the upper ionosphere. It is proved that different events on the Earth and in its atmopshere have their own impact on Earth electric field, and the earthquakes are in this group. Many strong earthquakes induce tsunamis, which are also suspected as contributing to the gravity waves having an impact on the ionospheric TEC. These reasons encourage to the study on the sensitivity of Swarm LP and POD GNSS data to the abovementioned phenomena. Referring to the sensitivity of TEC data derived from GNSS stations to Earthquakes, sensitivity of GNSS and LP data at around 500 km high orbit is analyzed here. A similar orbital height can be found in case of many LEO missions equipped at least with GNSS POD receivers, which makes Swarm especially interesting data acquisition platforms.</p><p>The investigation of Swarm data in view of Tsunamis and earthquakes is difficult due to several factors. There are only three satellites, the two of which fly almost together, which gives in fact only two points of the survey. The orbital repetition period is long, which seriously limits the number of comparable observations in terms of the location and time of the day. Finally, the number of large earthquakes and tsunami events in time of Swarm science mission is low, and many Earthquakes do not coincide sufficiently with Swarm passes in time and space. All these factors, however, doesn’t exclude an opportunity of analyzing of Swarm data passes above the earthquakes of magnitude nearby 8, linked with the tsunamis reaching several decimeters.</p><p>Swarm LP data is detrended and analyzed before the earthquakes and also during the earthquakes and resulting tsunami events. The GNSS POD topside TEC from Swarm is analyzed together as a background for LP data. In-situ electron density disturbances occurring during a pass close to the earthquake is compared to selected STEC measurements between LEO and GNSS satellites. Additionally absolute STEC values from selected nearby ground stations are analyzed in order to  find existing correlations for detected disturbances in the electric and magnetic fields. All the observations are sparse in time and space, and therefore, leave some unanswered questions and uncertainties. However, several interesting perturbations over earthquake/tsunami events are observable in both Swarm LP data and GNSS TEC data.</p>

scholarly journals Ionospheric irregularities and scintillations: a direct comparison of in situ density observations with ground-based L-band receivers

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Sharon Aol ◽  
Stephan Buchert ◽  
Edward Jurua
Keyword(s):  
Electron Density ◽  
Satellite Communication ◽  
Density Fluctuations ◽  
Ionospheric Irregularities ◽  
Langmuir Probes ◽  
Amplitude Scintillation ◽  
Swarm Satellites ◽  
L Band ◽  
Electron Density Fluctuations

Abstract Ionospheric irregularities can affect satellite communication and navigation by causing scintillations of radio signals. The scintillations are routinely measured using ground-based networks of receivers. This study presents observations of ionospheric irregularities by Langmuir probes on the Swarm satellites. They are compared with amplitude scintillation events recorded by the Global Positioning System-Scintillation Network and Decision Aid (GPS-SCINDA) receiver installed in Mbarara (Lat: $$0.6^{\circ }\hbox {S}$$ 0 . 6 ∘ S , Lon: $$30.8^{\circ }\hbox {E}$$ 30 . 8 ∘ E , Mag. lat: $$10.2^{\circ }\hbox {S}$$ 10 . 2 ∘ S ). The study covers the years from 2014 to 2018 when both data sets were available. It was found that the ground-based amplitude scintillations were enhanced when Swarm registered ionospheric irregularities for a large number of passes. The number of matching observations was greater for Swarm A and C which orbited at lower altitudes compared to Swarm B. However, some counterexamples, i.e., cases when in situ electron density fluctuations were not associated with any observed L-band amplitude scintillation and vice versa, were also found. Therefore, mismatches between observed irregularity structures and scintillations can occur just over a few minutes and within distances of a few tens of kilometers. The amplitude scintillation strength, characterized by the S4 index was estimated from the electron density data using the well-known phase screen model for weak scattering. The derived amplitude scintillation was on average lower for Swarm B than for A and C and less in accordance with the observed range. Irregularities at an altitude of about 450 km contribute strongly to scintillations in the L-band, while irregularities at about 510-km altitude contribute significantly less. We infer that in situ density fluctuations observed on passes over or near Mbarara may be used to indicate the risk that ionospheric radio wave scintillations occur at that site.

Identifying evolving/non-evolving plasma bubbles from SWARM observations

2021 ◽  
Author(s):  
Chinmaya Nayak ◽  
Stephan Buchert ◽  
Bharati Kakad
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Cross Correlation ◽  
Neutral Atmosphere ◽  
Magnetic Fluctuations ◽  
Equatorial Station ◽  
Plasma Bubbles ◽  
Field Fluctuations ◽  
The Cross

<p>Equatorial plasma bubbles (EPBs) are generally caused due to the Rayleigh–Taylor instability. During the initial phase of the growth of the instability, the bubbles are associated with perturbation electric and magnetic fields. We call this the evolving (active) phase of the EPB. Over time, these electric field fluctuations decay in amplitude and the bubble, embedded in the neutral atmosphere, drifts eastward without much temporal evolution. We call this the non-evolving phase. Both phases can be distinguished in ground based VHF spaced receiver scintillation observations. In the evolving phase, the cross correlation between the signals from the two receivers is significantly less than one because of rapidly evolving perturbation electric fields. However, after some time (~2 hours) as the perturbation electric field decays, the cross correlation reaches almost 1 implying very slow temporal changes. This technique is applied to identify fresh generation of post-midnight plasma bubbles during magnetically disturbed conditions. From in situ satellite observations, the EPBs are generally identified as sudden depletion from background electron density, associated with magnetic fluctuations. In fact, the plasma bubble index produced from data of the ESA Swarm mission utilizes this same criteria of concurrent density depletions and magnetic fluctuations to identify the plasma bubbles. However, it is not so straightforward to distinguish evolving and non-evolving phases of the plasma bubbles in the SWARM plasma and magnetic observations. We look into near simultaneous in situ observations of SWARM and ground based VHF spaced receiver scintillation to identify a standard criteria for distinguishing evolving/non-evolving bubbles in SWARM observations. The results suggest that the presence/absence of magnetic fluctuations associated with the depletion in electron density can be used as a criteria for evolving/non-evolving bubbles. Ideally, the electric and magnetic field fluctuations should be present simultaneously and as a result should decay simultaneously. We have looked into one year (2014) of SWARM observations of EPBs and VHF spaced receiver scintillation data from Indian equatorial station Tirunelveli. A few case studies during both magnetically quiet and disturbed conditions are discussed.</p>

Catalytic activity of rhodium(I) complexes containing (ω-trimethylsilylalkyl)diphenylphosphines

1980 ◽  
Vol 45 (8) ◽  
pp. 2219-2223 ◽  
Author(s):  
Marie Jakoubková ◽  
Martin Čapka
Keyword(s):  
Catalytic Activity ◽  
Nmr Spectroscopy ◽  
Ir Spectroscopy ◽  
Electron Density ◽  
Phosphorus Atom ◽  
Proton Acceptor ◽  
Trimethylsilyl Group ◽  
Kinetics Of

Kinetics of homogenous hydrogenation of 1-heptene catalysed by rhodium(I) complexes prepared in situ from μ,μ'-dichloro-bis(cyclooctenerhodium) and phosphines of the type RP(C6H5)2 (R = -CH3, -(CH2)nSi(CH3)3; n = 1-4) have been studied. The substitution of the ligands by the trimethylsilyl group was found to increase significantly the catalytic activity of the complexes. The results are discussed in relation to the electron density on the phosphorus atom determined by 31P NMR spectroscopy and to its proton acceptor ability determined by IR spectroscopy.

scholarly journals Mapping High Spatiotemporal-Resolution Soil Moisture by Upscaling Sparse Ground-Based Observations Using a Bayesian Linear Regression Method for Comparison with Microwave Remotely Sensed Soil Moisture Products

2021 ◽  
Vol 13 (2) ◽  
pp. 228
Author(s):  
Jian Kang ◽  
Rui Jin ◽  
Xin Li ◽  
Yang Zhang
Keyword(s):  
Soil Moisture ◽  
Large Scale ◽  
Spatial Scales ◽  
Microwave Remote Sensing ◽  
In Situ Measurements ◽  
Spatial Density ◽  
Linear Regression Method ◽  
Spatiotemporal Resolution ◽  
Pixel Scale

In recent decades, microwave remote sensing (RS) has been used to measure soil moisture (SM). Long-term and large-scale RS SM datasets derived from various microwave sensors have been used in environmental fields. Understanding the accuracies of RS SM products is essential for their proper applications. However, due to the mismatched spatial scale between the ground-based and RS observations, the truth at the pixel scale may not be accurately represented by ground-based observations, especially when the spatial density of in situ measurements is low. Because ground-based observations are often sparsely distributed, temporal upscaling was adopted to transform a few in situ measurements into SM values at a pixel scale of 1 km by introducing the temperature vegetation dryness index (TVDI) related to SM. The upscaled SM showed high consistency with in situ SM observations and could accurately capture rainfall events. The upscaled SM was considered as the reference data to evaluate RS SM products at different spatial scales. In regard to the validation results, in addition to the correlation coefficient (R) of the Soil Moisture Active Passive (SMAP) SM being slightly lower than that of the Climate Change Initiative (CCI) SM, SMAP had the best performance in terms of the root-mean-square error (RMSE), unbiased RMSE and bias, followed by the CCI. The Soil Moisture and Ocean Salinity (SMOS) products were in worse agreement with the upscaled SM and were inferior to the R value of the X-band SM of the Advanced Microwave Scanning Radiometer 2 (AMSR2). In conclusion, in the study area, the SMAP and CCI SM are more reliable, although both products were underestimated by 0.060 cm3 cm−3 and 0.077 cm3 cm−3, respectively. If the biases are corrected, then the improved SMAP with an RMSE of 0.043 cm3 cm−3 and the CCI with an RMSE of 0.039 cm3 cm−3 will hopefully reach the application requirement for an accuracy with an RMSE less than 0.040 cm3 cm−3.

scholarly journals An In-Situ Reaction Route to Molecular Level Dispersed Bisimide and ZnO Nanorod Hybrids with Efficient Photo-Induced Charge Transfer

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Chunzheng Lv ◽  
Lirong He ◽  
Jiahong Tang ◽  
Feng Yang ◽  
Chuhong Zhang
Keyword(s):  
Charge Transfer ◽  
Electric Field ◽  
Self Assembly ◽  
Molecular Level ◽  
Surface Photovoltage ◽  
Zno Nanorod ◽  
In Situ Reaction ◽  
Perylene Bisimide ◽  
Induced Charge

AbstractAs an important photoconductive hybrid material, perylene/ZnO has attracted tremendous attention for photovoltaic-related applications, but generally faces a great challenge to design molecular level dispersed perylenes/ZnO nanohybrids due to easy phase separation between perylenes and ZnO nanocrystals. In this work, we reported an in-situ reaction method to prepare molecular level dispersed H-aggregates of perylene bisimide/ZnO nanorod hybrids. Surface photovoltage and electric field-induced surface photovoltage spectrum show that the photovoltage intensities of nanorod hybrids increased dramatically for 100 times compared with that of pristine perylene bisimide. The enhancement of photovoltage intensities resulting from two aspects: (1) the photo-generated electrons transfer from perylene bisimide to ZnO nanorod due to the electric field formed on the interface of perylene bisimide/ZnO; (2) the H-aggregates of perylene bisimide in ZnO nanorod composites, which is beneficial for photo-generated charge separation and transportation. The introduction of ordered self-assembly thiol-functionalized perylene-3,4,9,10-tetracarboxylic diimide (T-PTCDI)/ ZnO nanorod composites induces a significant improvement in incident photo-to-electron conversion efficiency. This work provides a novel mentality to boost photo-induced charge transfer efficiency, which brings new inspiration for the preparation of the highly efficient solar cell.

scholarly journals Tuning Single-Molecule Conductance by Controlled Electric Field-Induced trans-to-cis Isomerisation

2021 ◽  
Vol 11 (8) ◽  
pp. 3317
Author(s):  
C.S. Quintans ◽  
Denis Andrienko ◽  
Katrin F. Domke ◽  
Daniel Aravena ◽  
Sangho Koo ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Single Molecule ◽  
Quantum Interference ◽  
Single Molecule Level ◽  
Wet Chemical Synthesis ◽  
Single Molecule Junctions ◽  
Tunnelling Microscopy ◽  
The Difference

External electric fields (EEFs) have proven to be very efficient in catalysing chemical reactions, even those inaccessible via wet-chemical synthesis. At the single-molecule level, oriented EEFs have been successfully used to promote in situ single-molecule reactions in the absence of chemical catalysts. Here, we elucidate the effect of an EEFs on the structure and conductance of a molecular junction. Employing scanning tunnelling microscopy break junction (STM-BJ) experiments, we form and electrically characterize single-molecule junctions of two tetramethyl carotene isomers. Two discrete conductance signatures show up more prominently at low and high applied voltages which are univocally ascribed to the trans and cis isomers of the carotenoid, respectively. The difference in conductance between both cis-/trans- isomers is in concordance with previous predictions considering π-quantum interference due to the presence of a single gauche defect in the trans isomer. Electronic structure calculations suggest that the electric field polarizes the molecule and mixes the excited states. The mixed states have a (spectroscopically) allowed transition and, therefore, can both promote the cis-isomerization of the molecule and participate in electron transport. Our work opens new routes for the in situ control of isomerisation reactions in single-molecule contacts.

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