Auroral brightening is one of the most common phenomena that occur during substorm onset and is usually recognized as a projection of the substorm‐associated magnetospheric plasma dynamics to the ...ionosphere. However, electromagnetic fields and plasma features associated with the substorm brightening arc have not been well understood. In this study, we present a comprehensive observation of the source plasma and field variations of a substorm brightening aurora in the inner magnetosphere. We performed a unique conjugate observation of a substorm brightening auroral arc observed by a ground‐based camera and by the Arase satellite in the magnetospheric source region at L ∼ 6. The event was observed at Tromsø (69.6°N, 19.2°E), Norway, on 12 October 2017. The brightening arc indicates east‐west structures with longitudinal scales of ∼0.5°–2.0°. Field‐aligned bi‐directional electrons with an energy range between 66 and 1,800 eV were detected by the satellite, simultaneously with the appearance of the brightening arc in the camera. These electrons were probably supplied from the auroral brightening region in the ionosphere, indicating that the satellite was on the same field line of the brightening aurora. The magnetic and electric field data show characteristic fluctuations and earthward Poynting flux around the time that the satellite crossed the aurora. Anti‐phase oscillations between the thermal pressure and the magnetic pressure are also reported. Based on these observations, we suggest the possibility that a ballooning instability occurred in the source region of the substorm brightening arc in the inner magnetosphere at L ∼ 6.
Plain Language Summary
A frequently occurring source of variations in the magnetosphere is the substorm, a process that causes energy dissipation into the atmosphere. Substorm is presented as the development of aurorae at high latitudes in the ionosphere. The study of substorm processes helps in understanding the near‐Earth space environment and the space weather. Along Earth's magnetic field lines, the aurora at a latitude of ∼65°N can be traced to ∼4–7 Earth radii away from the Earth at the equatorial plane in space. Using a ground‐based auroral camera, we can construct the correspondence between auroral motion and field and plasma variation at the satellite. This study reports such a unique event of substorm brightening arc observed at Tromsø, Norway, on 12 October 2017. Satellite observed bi‐directional electrons prove the connection between aurora break‐up at ∼100 km altitude and its source region in the magnetosphere at ∼30,000 km away from Earth. Based on the magnetic wave spectrograms, auroral bead‐like structures and other observational results, we suggest the possibility that a ballooning plasma instability occurred in the source region of the substorm brightening arc in the inner magnetosphere.
Key Points
Observation of plasma and field features in the source region of a sudden brightening auroral arc during a minor substorm onset at L ∼ 6
Energization of particles, field‐aligned electrons, and electromagnetic field fluctuations were observed during the arc crossing by Arase
Several observational facts indicate the possibility of ballooning instability occurring at this substorm onset
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•UB3LYP-D3 + COSMO calculations yielded meta-stable structures of S2 state of CaMn4O5 cluster in PSII.•Relative stability was investigated by hybrid-DFT and DLPNO-CC ...methods.•Broken-Symmetry (BS) solutions for all pattern of spin configurations were constructed and evaluated sets of effective exchange integrals J as magnetic coupling parameters.
Full geometry optimization of all S2 intermediates in OEC (oxygen-evolving complex) of PSII (photosystem II) were carried out by using UB3LYP-D3/Def2-TZVP with COSMO solvation effects. Our detail calculations yielded meta-stable structures of six (=3 × 2 (HS (high-spin), IS (intermediate-spin)) intermediates for W1 = W2 = H2O and eight (=4 × 2 (HS, IS)) intermediates for W1 = OH− or W2 = OH−, and were named to H2O and OH models, respectively. In the next step, relative stability among these intermediate structures were investigated by hybrid-DFT and DLPNO-CC methods. UB3LYP methods show that right (R)-opened structures (open-cubane) are more stable than left (L)-opened structures (closed-cubane) by about 3.5 kcal/mol, though decreasing of DFT-weights suppresses such energy gaps. DLPNO-CCSD(T0) methods promote stabilization of (L)-structures and finally reproduce near degeneration or more stable (L)-structure. All pattern of spin configurations in four Mn(III) and Mn(IV) ions were assumed and BS (broken-symmetry) solutions were successfully obtained to find the most stable spin structures. This complete sets of all spin conformations enabled us evaluate sets of effective exchange integrals J as magnetic coupling parameters. The calculated J values for the spin Hamiltonian elucidated one g2 (S = 1/2) and two g4 (S = 5/2) molecular structures in the S2 state in accord with the recent EXAFS results.
The transport of impurities supplied by a multi‐species impurity powder dropper (IPD) in the large helical device (LHD) is investigated using a three‐dimensional peripheral plasma fluid code ...(EMC3‐EIRENE) coupled with a dust transport simulation code (DUSTT). The trajectories of impurity powder particles (Boron, Carbon, Iron, and Tungsten) dropped from the IPD and the impurity transport in the peripheral plasma are studied in a full‐torus geometry. The simulation reveals an appropriate size of the impurity powder particles and an optimum operational range of the dust drop rates for investigating the impurity transport without inducing radiation collapse. The simulation also predicts a favourable plasma discharge condition for wall conditioning (boronization) using the IPD in order to deposit boron to high plasma flux and neutral particle density areas in the divertor region in the inboard side of the torus.
QM(UB3LYP)/MM(AMBER) calculations were performed for the locations of the transition structure (TS) of the oxygen-oxygen (O-O) bond formation in the S
4
state of the oxygen-evolving complex (OEC) of ...photosystem II (PSII). The natural orbital (NO) analysis of the broken-symmetry (BS) solutions was also performed to elucidate the nature of the chemical bonds at TS on the basis of several chemical indices defined by the occupation numbers of NO. The computational results revealed a concerted bond switching (CBS) mechanism for the oxygen-oxygen bond formation coupled with the one-electron transfer (OET) for water oxidation in OEC of PSII. The orbital interaction between the σ-HOMO of the Mn(IV)
4
-O
(5)
bond and the π*-LUMO of the Mn(V)
1
=O
(6)
bond plays an important role for the concerted O-O bond formation for water oxidation in the CaMn
4
O
6
cluster of OEC of PSII. One electron transfer (OET) from the π-HOMO of the Mn(V)
1
=O
(6)
bond to the σ*-LUMO of the Mn(IV)
4
-O
(5)
bond occurs for the formation of electron transfer diradical, where the generated anion radical Mn(IV)
4
-O
(5)
-
* part is relaxed to the *Mn(III)
4
... O
(5)
-
structure and the cation radical O
(6)
=Mn(V)
1
+
* part is relaxed to the
+
O
(6)
-Mn(IV)
1
* structure because of the charge-spin separation for the electron-and hole-doped Mn-oxo bonds. Therefore, the local spins are responsible for the one-electron reductions of Mn(IV)
4
->Mn(III)
4
and Mn(V)
1
->Mn(IV)
1
. On the other hand, the O
(5)
-
and O
(6)
+
sites generated undergo the O-O bond formation in the CaMn
4
O
6
cluster. The Ca(II) ion in the cubane- skeleton of the CaMn
4
O
6
cluster assists the above orbital interactions by the lowering of the orbital energy levels of π*-LUMO of Mn(V)
1
=O
(6)
and σ*-LUMO of Mn(IV)
4
-O
(5)
, indicating an important role of its Lewis acidity. Present CBS mechanism for the O-O bond formation coupled with one electron reductions of the high-valent Mn ions is different from the conventional radical coupling (RC) and acid-base (AB) mechanisms for water oxidation in artificial and native photosynthesis systems. The proton-coupled electron transfer (PC-OET) mechanism for the O-O bond formation is also touched in relation to the CBS-OET mechanism.
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•Domain-based local pair natural orbital (DLPNO) coupled cluster methods (CCSD(T)).•14 different S2 intermediates of OEC in photosystem II.•1 low-spin right-opened & 2 high-spin ...left-opened structures are nearly degenerated.•Supporting previous one LS-two HS model from recent EXAFS and EPR results.
Domain-based local pair natural orbital (DLPNO) coupled cluster single and double (CCSD) with triple perturbation (T) correction methods were applied for fourteen different S2 structures of the CaMn4O5 cluster in oxygen evolving complex (OEC) of photosystem II (PSII). The DLPNO-CCSD(T0) calculations elucidated that the right (R)-opened S2aYZ structure (a = O2− at the O(5) site, Y = W2 and Z = W1) with the low spin (LS) (S = 1/2, g = 2) state and two left (L)-opened S2aYZ structures with the high spin (HS) (S = 5/2, g = 4; g > 4) state were nearly degenerated in energy, supporting previous one LS-two HS model for the S2 state in compatible with recent EXAFS and EPR results.
Summary
Porphyromonas gingivalis can synthesize both A‐LPS and O‐LPS lipopolysaccharides, which contain anionic O‐polysaccharides and conventional O‐polysaccharides, respectively. A‐LPS can anchor ...virulence proteins to the cell surface, so elucidating the mechanism of A‐LPS synthesis is important for understanding the pathogenicity of this bacterium. To identify the genes involved in LPS synthesis, we focused on uncharacterized genes encoding the glycosyltransferases, PGN_0361, PGN_1239, PGN_1240 and PGN_1668, which were tentatively named gtfC, gtfD, gtfE and gtfF, respectively, and characterized their mutants. We found that disruption of gtfC and gtfF resulted in A‐LPS deficiency. In addition, a gtfD mutant had abnormal A‐LPS synthesis, and a gtfE mutant exhibited a rough‐type LPS that possesses a short oligosaccharide with lipid A‐core. We then constructed a gtfC and gtfD double mutant, because their amino acid sequences were very similar, and this mutant similarly possessed a rough‐type LPS. Cross‐complementation analysis revealed that the GtfD protein is a functional homologue of the Escherichia coli WbbL protein, which is a rhamnosyltransferase. These results suggested that the GtfE protein is essential for the synthesis of both O‐LPS and A‐LPS, and that GtfC and GtfD proteins may work together to synthesize the two kinds of LPS. In addition, the GtfF protein was essential for A‐LPS synthesis, although this may be achieved in a strain‐specific manner.
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•Domain-based local pair natural orbital (DLPNO) coupled cluster single and double (CCSD) with triple perturbation (T) correction methods were applied for six different S1 structures ...of oxygen evolving complex (OEC) of photosystem II (PSII), showing that right-opened three S1 structures were nearly degenerated in energy.•The DLPNO- CCSD(T) calculations support proposals of the multi-intermediate models for the S1 state in accord with the EPR, other experimental and DFT computational results.
Domain-based local pair natural orbital (DLPNO) coupled cluster single and double (CCSD) with triple perturbation (T) correction methods were applied for six different S1 structures of oxygen evolving complex (OEC) of photosystem II (PSII), showing that right-opened three S1 structures were nearly degenerated in energy. The DLPNO- CCSD(T0) calculations support proposals of the multi-intermediate models for the S1 state in accord with the EPR, other experimental and DFT computational results.
Abstract
Pulsating aurorae (PsA) are caused by the intermittent precipitations of magnetospheric electrons (energies of a few keV to a few tens of keV) through wave-particle interactions, thereby ...depositing most of their energy at altitudes ~ 100 km. However, the maximum energy of precipitated electrons and its impacts on the atmosphere are unknown. Herein, we report unique observations by the European Incoherent Scatter (EISCAT) radar showing electron precipitations ranging from a few hundred keV to a few MeV during a PsA associated with a weak geomagnetic storm. Simultaneously, the Arase spacecraft has observed intense whistler-mode chorus waves at the conjugate location along magnetic field lines. A computer simulation based on the EISCAT observations shows immediate catalytic ozone depletion at the mesospheric altitudes. Since PsA occurs frequently, often in daily basis, and extends its impact over large MLT areas, we anticipate that the PsA possesses a significant forcing to the mesospheric ozone chemistry in high latitudes through high energy electron precipitations. Therefore, the generation of PsA results in the depletion of mesospheric ozone through high-energy electron precipitations caused by whistler-mode chorus waves, which are similar to the well-known effect due to solar energetic protons triggered by solar flares.
Magneto-structural correlations in oxygen-evolving complex (OEC) of photosystem II (PSII) have been elucidated on the basis of theoretical and computational results in combination with available ...electron paramagnetic resonance (EPR) experimental results, and extended x-ray absorption fine structure (EXAFS) and x-ray diffraction (XRD) results. To this end, the computational methods based on broken-symmetry (BS) UB3LYP solutions have been developed to elucidate magnetic interactions in the active manganese catalyst for water oxidation by sunlight. The effective exchange interactions J for the CaMn(III)Mn(IV)
3
O
5
(H
2
O)
3
Y(Y = H
2
O or OH
−
) cluster (1) model of OEC of PSII have been calculated by the generalised approximate spin projection (GAP) method that eliminates the spin contamination errors of the BS UB3LYP solution. Full geometry optimisations followed by the zero-point energy (ZPE) correction have been performed for all the spin configurations of 1 to improve the J values that are compared with accumulated EPR in the S
2
state of Kok cycle and magnetic susceptibility results of Christou model complex Ca
2
Mn(IV)
3
O
4
(2). Using the calculated J values, exact diagonalisation of the spin Hamiltonian matrix has been carried out to obtain excitation energies and spin densities of the ground and lower excited states of 1. The calculated excitation energies are consistent with the available experimental results. The calculated spin densities (projection factors) are also compatible with those of the EPR results. The calculated spin densities have been used to calculate the isotropic hyperfine (A
iso
) constants of
55
Mn ions revealed by the EPR experiments. Implications of the computational results are discussed in relation to the structural symmetry breaking (SSB) in the S
1
, S
2
and S
3
states, spin crossover phenomenon induced by the near-infrared excitation and the right- and left-handed scenarios for the O-O bond formation for water oxidation.
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