We study the spatial structure of a polarization jet/Sub‐Auroral Ion Drift (PJ/SAID) based on data from the NorSat‐1 and Swarm satellites during a geomagnetic storm. Observations of plasma parameters ...inside the PJ/SAID are obtained with NorSat‐1 using a system of Langmuir probes with a nominal sampling rate of up to 1 kHz, which allowed measurements with such a high temporal resolution for the first time. A comparative analysis of plasma parameters and electron density spectra inside PJ according to the data from both satellites is presented. Our results show that fluctuations of plasma parameters inside the PJ increase at all scales with increasing geomagnetic activity. Small‐scale irregularities in the PJ are measured in situ down to hundreds of meters. The role of large‐scale effects in the PJ increases in comparison with the small‐scale ones during high geomagnetic activity. The PJ consists of structures ∼0.2° latitude in size within which small‐scale irregularities are present.
Plain Language Summary
Polarization jet (PJ), also known as Sub‐Auroral Ion Drift (SAID), events are fast westward plasma drifts with a narrow latitudinal extent, occurring at subauroral latitudes in the Earth's ionosphere. The decrease in the density of the ionospheric plasma inside PJ/SAID significantly affects the conditions for the propagation of shortwave radio waves, which indicates the practical importance of studying this phenomenon. Despite the importance of using a variety of ground‐based observation facilities for studying and analyzing PJ/SAID properties, as well as developing analytical models and numerical modeling, in situ observations are the most valuable. Such in situ observations can be obtained only with satellites flying through a developing PJ/SAID. Large‐scale features of PJ/SAID are currently well understood, but small‐scale processes within PJ/SAID are practically not studied, and many open questions remain. In this work, we study the small‐scale structures in PJ/SAID during a geomagnetic storm of 20 April 2018, using multi‐instrumental approach involving low‐Earth orbit.
Key Points
Fluctuations of plasma parameters inside the polarization jet (PJ) increase at all scales during higher geomagnetic activity
Small‐scale irregularities inside the PJ are measured in situ down to hundreds of meters
The role of large‐scale effects in the PJ increases in comparison with small‐scale ones with geomagnetic activity
This work presents the first results of measurements of artificial plasma disturbance characteristics using the low‐orbit NorSat‐1 satellite, which are excited when the ionospheric F2 layer is ...modified by powerful high‐frequency (HF) waves emitted by the SURA heating facility. NorSat‐1 carries the multineedle Langmuir probe instrument, which is capable of sampling the electron density at a nominal rate up to 1 kHz. The uniqueness of this experiment lies in the fact that the satellite passes very close to the center of the HF‐perturbed magnetic flux tube and in situ observations are first carried out in winter when the absorption is still small in the morning as the Sun is low above the horizon. There are HF‐induced plasma temperature and density variations at satellite altitudes of about 580 km. Plasma irregularities are detected by in situ measurements down to 200 m at the southern border of the SURA heating region.
Plain Language Summary
The current stage in the development of active experiments includes the use of satellites for sensing plasma disturbances in situ. However, these data can only be obtained if the satellite crosses an HF‐perturbed magnetic flux tube, which rests on a region with highly developed turbulence generated near pump wave reflected altitude; in other words, “the satellite has to be in the right place at the right time.” This study presents results related to features of artificial plasma density irregularities at a height of 580 km obtained during the SURA‐NorSat‐1 active experiment when NorSat‐1 passed very close to the center of the HF‐perturbed magnetic flux tube. For the first time, in situ measurements were carried out by the satellite with such a high resolution of Langmuir probes in comparison with previous experiments with DEMETER and DMSP. It is shown that there are HF‐induced plasma temperature and density variations at satellite altitudes and an increase in temperature is more substantial than changes in plasma density. Plasma irregularities are detected by in situ measurements down to 200 m at the southern border of the SURA heating region. The spatial distribution of artificial plasma disturbances is strongly influenced by the “magnetic zenith” effect.
Key Points
Results of the first SURA‐NorSat‐1 joint experiment are presented
Increase in temperature is more substantial than changes in plasma density in high‐frequency heating region
In situ observations detect plasma irregularities down to 200 m at the southern edge of the heated SURA volume
It is well-known that the auroral region of the magnetosphere–ionosphere interaction is an open, nonlinear dissipative system far from the equilibrium state. It is in this region that auroras are ...regularly observed, demonstrating not only a wide variety of dynamic forms but also a wide range of temporal and spatial scales. Due to the memory effects and fractal properties of auroral plasma, as well as strong correlations between its individual parts, the dynamics of the high-latitude system are primarily determined by long-range electromagnetic forces. Therefore, it is expected that non-additive and non-extensive thermodynamic principles may characterize their macroscopic behavior. In the presented study, it is shown that pulsating auroras exhibit non-extensive properties and can be described by q-statistics. The correlation of the parameter q with traditional indicators of nonlinear dynamics, such as the flatness coefficient, standard deviation, and scaling index, has been investigated. Small-scale changes are superimposed on large-scale processes characterized by a low correlation dimension, and this leads to an increase in the correlation dimension during geomagnetic activity, which approximately coincides with increased values of q. It is concluded that the q-statistics (Tsallis distribution) can be used to analyze optical phenomena in the auroral region.
•Non-extensive (Tsallis) q-statistics is applied to pulsating auroras.•Auroral glow exhibit non-extensive properties and can be described by q-statistics.•Correlation of q-parameter with traditional indices of nonlinear dynamics is studied.•Parameter q increases with a short delay after the increase in the glow of auroras.•It is shown the behavior of parameter q and correlation dimension is similar.
Stratified Subauroral Ion Drift (SSAID) Sinevich, A. A.; Chernyshov, A. A.; Chugunin, D. V. ...
Journal of geophysical research. Space physics,
March 2023, Letnik:
128, Številka:
3
Journal Article
Recenzirano
Odprti dostop
In this paper, the internal structuring of Polarization Jet (PJ)/Subauroral Ion Drift (SAID) is studied. It is shown that PJ/SAID consists of several Polarization Jet Strata (PJS) of electron density ...and temperature. A new type of phenomena has been discovered called Stratified Subauroral Ion Drift (SSAID), which is a PJ/SAID containing small‐scale PJS. Internal small‐scale structure of SSAIDs is measured during various geomagnetic events using data from NorSat‐1, DMSP F‐17 and F‐18 satellites. High resolution measurements on the Norsat‐1 satellite make it possible to detect and study small‐scale structures inside the PJ/SAID, that is, SSAID. The data from DMSP satellites is used to determine explicitly the presence of PJ/SAID during the considered geomagnetic events. Results show that SSAID consist of 2–4 large PJS and from a few units to several tens of small PJS. Large PJS have a size of 0.2°–0.3° latitude and small PJS have a size of <0.1°. Several suggestions regarding possible physical mechanisms of production of SSAID and PJS are presented.
Plain Language Summary
In the subauroral zone, narrow fluxes of fast subauroral ion drifts are observed near the projection of the plasmapause at heights of the F‐layer of the ionosphere, which are most noticeable during geomagnetic activity against the background of large‐scale plasma convection, called polarization jet (PJ) or subauroral ion drifts (SAID). Despite the importance of using a variety of ground‐based observation facilities for studying and analyzing PJ/SAID properties, as well as developing analytical models and numerical modeling, in situ observations are most valuable. These observations can be obtained only during the satellite flyby through the subauroral zone during the PJ/SAID development. Small‐scale processes inside PJ/SAID were practically not studied and many open questions remain here due to lack of high‐resolution satellite measurements. In this work, using NorSat‐1 satellite high sampling rate data, we report that there are Stratified Subauroral Ion Drifts (SSAIDs) which consist of small‐scale Polarization Jet Strata (PJS) of electron density and temperature.
Key Points
We explore the internal structuring of subauroral polarization jets/ion drifts (SSAID ‐ Stratified Subauroral Ion Drift)
SSAIDs consist of 2–4 large Polarization Jet Strata (PJS) and from a few units to several tens of small PJS
Large PJS have a size of 0.2°‐0.3° latitude and small PJS have a size of <0.1°
Oxidative coupling (OC) through
-quinone intermediates has been established as an efficient and site-selective way to modify protein N-termini and the unnatural amino acid
-aminophenylalanine (
aF). ...Recently, we reported that the tyrosinase-mediated oxidation of phenol-tagged cargo molecules is a particularly convenient method of generating
-quinones in situ. The coupling partners can be easily prepared and stored, the reaction takes place under mild conditions (phosphate buffer, pH 6.5, 4 to 23 °C), and dissolved oxygen is the only oxidant required. Here, we show an important extension of this chemistry for the activation of tyrosine residues that project into solution from the N or C-termini of peptide and protein substrates. Generating the
-quinone electrophiles from tyrosine allows greater flexibility in choosing the nucleophilic coupling partner and expands the scope of the reaction to include C-terminal positions. We also introduce a new bacterial tyrosinase enzyme that shows improved activation for some tyrosine substrates. The efficacy of several secondary amines and aniline derivatives was evaluated in the coupling reactions, providing important information for coupling partner design. This strategy was used to modify the C-termini of an antibody scFv construct and of Protein L, a human IgG kappa light chain binding protein. The use of the modified proteins as immunolabeling agents was also demonstrated.
Auroral kilometric radiation is used as a tool for the remote diagnostics of processes in the Earth’s magnetosphere. Using satellite data and the spectrum of fluctuations of auroral kilometric ...radiation at various frequencies, the fractal properties of the auroral region of the magnetosphere depending on the altitude of a source and the frequency of generated radiation are studied. The fractal characteristics (Hurst exponent and fractal dimension) of the medium in the region of generation of auroral kilometric radiation and their dynamics depending on the altitude and frequency are determined from the scaling law. It is shown that the scaling and Hurst exponent increase with the altitude (or with a decrease in the signal frequency), whereas the fractal dimension decreases with an increase in the altitude. The scaling and fractal parameters obtained in this work indicate that the processes under consideration exhibit long-range dependence.
Site-selective protein-protein coupling has long been a goal of chemical biology research. In recent years, that goal has been realized to varying degrees through a number of techniques, including ...the use of tyrosinase-based coupling strategies. Early publications utilizing tyrosinase from
(abTYR) showed the potential to convert tyrosine residues into
-quinone functional groups, but this enzyme is challenging to produce recombinantly and suffers from some limitations in substrate scope. Initial screens of several tyrosinase candidates revealed that the tyrosinase from
(megaTYR) is an enzyme that possesses a broad substrate tolerance. We use the expanded substrate preference as a starting point for protein design experiments and show that single point mutants of megaTYR are capable of activating tyrosine residues in various sequence contexts. We leverage this new tool to enable the construction of protein trimers via a charge-directed sequential activation of tyrosine residues (CDSAT).
According to measurements of the electric component of the electromagnetic field in the frequency range from 2 kHz to 10 MHz by the Japanese ERG satellite, generation regions of kilometric continuum ...radiation and new hectometric continuum radiation have been determined. It is demonstrated that the kilometric continuum is mainly observed on the dayside of the magnetosphere, its source is located near the geomagnetic equatorial plane, and the size of the source does not exceed ±(0.1–0.3)
R
E
across this plane, where
R
E
is the Earth radius. Hectometric radiation mainly observed in the nightside magnetosphere has two sources. One of them is located near the plasmasphere and its distance from the geomagnetic equator can reach 3
R
E
. The second source is observed near the Earth at distances from 1.1
R
E
to 2
R
E
.
Tsallis nonextensive statistical mechanics (or
q
-statistics) has been used for the first time to study pulsating auroras, which are regularly observed in the auroral ionosphere during geomagnetic ...disturbances. For systems in which long-range interactions, such as ionized gas or plasma, take place and whose dynamics are determined primarily by long-range electromagnetic forces, it can be expected that nonadditive and nonextensive thermostatistic principles can characterize their macroscopic behavior. In this paper, we argued that pulsating auroras exhibit nonextensive properties and can be described, among other things, by
q
-statistics. We have also demonstrated that the non-extensive parameter
q
correlates well with the flatness index and with the scaling index, which indicates the applicability of this approach for auroral glow. Thus,
q
-statistics can be used to analyze phenomena in the high-latitude region of the Earth.
The principal possibility to measure the plasma density and its fluctuations in the ionosphere on ultra-small space vehicles using radiophysical methods is shown. These methods allow us to determine ...the characteristics of the medium by the properties of the received radiation. It is assumed that each small spacecraft has a satellite navigation receiver as well as a device for emitting and detecting a signal at two multiple frequencies in the radio band. In this approach, information on plasma density is contained in the received phase difference. Radio receivers and radio transmitters on satellites constantly exchange radio signals and then it is possible to determine the plasma density and its fluctuations from the phase shift. Numerical estimates are also made to determine the maximum distance between satellites where one can reliably receive a radio signal.
•Use of radio signal exchange on ultra-small spacecrafts gives ionospheric information.•It is possible to measure plasma density and its fluctuations along satellite-satellite line.•If a phase shift is too large it is possible to estimate plasma density fluctuations.•Maximum distance between satellites to reliably receive a radio signal is estimated.
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