Joule heating is the primary source of the high latitude thermospheric energy dissipation during geomagnetic storm period. The nitric oxide (NO) emission at 5.3 μm accounts for the majority of Joule ...heating energy due to its radiative nature. It is the dominating cooling agent above 100 km that effectively regulates the thermospheric temperature. We studied the relationship between the response time of NO cooling emission and Joule heating rate during geomagnetic storm periods by using the NO emission observations by Sounding of Atmosphere using Broadband Emission Radiometry (SABER) onboard NASA’s Thermosphere‐Ionosphere‐Mesosphere Energetics and Dynamics (TIMED) satellite and the Joule heating rate measured by the European incoherent scatter (EISCAT) radar over Tromsø (geographic:69.59°N, 19.22°E), Norway, and the thermosphere‐ionosphere‐electrodynamics general circulation model (TIEGCM) simulation. We selected seven geomagnetic storms during which there were continuous measurements of the Pederson conductivity and electric fields when the TIMED/SABER satellite was in the northview mode. The TIEGCM gives a fair description of NO cooling. However, it was found that the Joule heating rates obtained with the TIEGCM often do not show good agreement with those from EISCAT observations. The Joule heating rate peaks with 3–7 hr of storm' onset. The NO cooling flux takes longer time to respond to the energy input during storm period. The fastest response of the NO cooling emission to the Joule heating rate is found during the strongest storm. The weakest storm does not have the longest response time. No correlation between the response time of NO cooling flux with respect to the Joule heating rate and storm’s intensity was observed.
Key Points
The magnitude of thermospheric cooling emission strongly depends on the storm’s intensity
Time lag of nitric oxide (NO) cooling emission with respect to Joule heating rate has little dependence on the storm’s intensity
Strong discrepancy is observed between the modeled and measured Joule heating rates
Epidermal keratinocytes need zinc Ogawa, Y.
British journal of dermatology (1951),
April 2019, 2019-Apr, 2019-04-00, 20190401, Letnik:
180, Številka:
4
Journal Article
Recenzirano
Linked Article: Bin et al. Br J Dermatol 2019; 180:869–880.
The Nitric Oxide (NO) emission at 5.3 μm wavelength is a well‐known coolant above 100 km. It effectively regulates thermospheric temperature during space weather events. We studied NO cooling ...emission over Tromsø (geographic:69.59°N, 19.22°E; cgm:66.58°,102.94°), Norway by using the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM) simulation driven by both Heelis and Weimer models as sources of geomagnetic forcing during October–November 2003 storm. The Weimer driven TIEGCM significantly overestimates thermospheric Nitric Oxide and Atomic Oxygen densities and underestimates temperature as compared to the Heelis driven simulation. The density ratio between the Weimer and Heelis driven estimations decreases with increasing altitude for both NO and atomic oxygen densities. The Heelis driven Joule heating rate agrees very well with the European incoherent scatter (EISCAT) radar measurements. It peaks during the main phase of the storm with magnitude about 4–5 times higher than that driven by Weimer model which peaks during the recovery phase. The difference in Joule heating rates between the Heelis and Weimer driven models increases with storm intensity, reaching a peak discrepancy of about an order of magnitude during the October‐November 2003 storm. An early and stronger NO cooling enhancement is predicted by Heelis driven TIEGCM simulation. It overestimates NO cooling emission by about 2–3 times as compared to SABER observations and about 4–5 times the Weimer driven calculation. This strong difference between the two models can be attributed to the model calculations of high latitude electric field and convection patterns.
Key Points
The Nitric Oxide cooling emission is studied over Tromsø, Norway, by using the TIEGCM simulations driven by both Weimer and Heelis models
Strong difference in Nitric Oxide emission is estimated between the Heelis and Weimer models driven TIEGCM simulations
The strong dissimilarity can be attributed to the model calculation of Joule heating rate
We have statistically analyzed data from the European Incoherent Scatter (EISCAT) UHF/VHF radars in Tromsø (69.60°N, 19.20°E), Norway, to reveal how the occurrence of pulsating auroras (PsAs) ...modifies the electron density profile in the ionosphere. By checking five winter seasons' (2007–2012) observations of all‐sky aurora cameras of the National Institute of Polar Research in Tromsø, we have extracted 21 cases of PsA. During these PsA events, either the UHF or VHF radar of EISCAT was operative and the electron density profiles were obtained along the field‐aligned or vertical direction near the zenith. From these electron density measurements, we calculated hmE (E region peak height) and NmE (E region peak density), which are proxies for the energy and flux of the precipitating PsA electrons, respectively. Then, we examined how these two parameters changed during the evolution of 21 PsA events in a statistical fashion. The results can be summarized as follows: (1) hmE is lower (the energy of precipitation electrons is higher) during the periods of PsA than that in the surrounding interval; (2) when NmE is higher (flux of PsA electrons is larger), hmE tends to be lower (precipitation is harder); (3) hmE is lower and NmE is larger in the later magnetic local time; and (4) when the AE index during the preceding substorm is larger, hmE is lower and NmE is larger. These tendencies are discussed in terms of the characteristics of particles and plasma waves in the source of PsA in the magnetosphere. In addition to the statistics of the EISCAT data, we carried out several detailed case studies, in which the altitude profiles of the electron density were derived by separating the On and Off phases of PsA. This allows us to estimate the true altitude profiles of the PsA ionization, which can be used for estimating the characteristic energy of the PsA electrons and better understanding the wave‐particle interaction process in the magnetosphere.
Key Points
Statistical characteristics of ionization during pulsating aurora are derived
Ionization associated with pulsating aurora occurs well below 100 km altitude
Pulsating aurora electrons tend to be harder in the later MLT
To realize a superelastic Mg-Sc lightweight alloy at room temperature, we investigated the stress–strain behavior of Mg-18.7 at.% Sc alloy sheets at room temperature with martensitic transformation ...starting temperature of approximately −90 °C. We found that the superelasticity of the alloy strongly depends on the grain size and a distinct room temperature superelasticity (~3% superelastic strain) was obtained in the alloy with a large grain size. The obtained maximum superelastic strain was smaller than that expected from the orientation dependence of the transformation strain. This result suggests that the stress-induced martensite phase was stabilized because of the introduction of slip defects.
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Enlarging the grain size in Mg–Sc alloys can greatly improve superelasticity. The impact of heat treatment conditions on abnormal grain growth (AGG) caused by phase transformation through cyclic heat ...treatment (CHT) was investigated in this study. In the CHT process between temperatures in a β single-phase region (Tβ) and α + β two-phase region (Tα+β), lowering the Tα+β resulted in a uniform huge grain size after AGG. In the heating process of the CHT from the Tα+β to the Tβ, the decrease in the heating rate was found to be ineffective in realizing huge grain size because the number of grains that can start AGG increases, which causes the collision of the abnormally growing grains with each other. We also revealed one of the key factors for the AGG to occur. Subgrains, which were formed through CHT, not only act as an additional driving force for grain growth but also shorten the required time for AGG nucleation.
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•Abnormal grain growth induced by phase transformation through cyclic heat treatment was investigated in Mg–Sc alloy.•Subgrains formed through cyclic heat treatment affected both nucleation and growth stages of abnormal grain growth.•Decreasing the holding temperature in an α + β two phase region led to larger and more uniform grain size.•Increase in heating rate was found to be effective in realizing larger grain size.•Grain size of over 2 cm was successfully realized after optimized cyclic heat treatment.
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.
On 24 November 2012, an interval of polar cap patches was identified by an all‐sky airglow imager located near the dayside cusp. During the interval, the successive appearance of poleward moving ...auroral forms (PMAFs) was detected, which are known to represent ionospheric manifestations of pulsed magnetic reconnections at the dayside magnetopause. All of the patches observed during the interval appeared from these transient auroral features (i.e., there was a one‐to‐one correspondence between PMAFs and newly created baby patches). This fact strongly suggests that patches can be directly and seamlessly created from a series of PMAFs. The optical intensities of the baby patches were 100–150 R, which is slightly lower than typical patch luminosity on the nightside and may imply that PMAF‐induced patches are generally low density. The generation of such patches could be explained by impact ionization due to soft particle precipitation into PMAFs traces. In spite of the faint signature of the baby patches, two coherent HF radars of the SuperDARN network observed backscatter echoes in the central polar cap, which represented signatures of plasma irregularities associated with the baby patches. These indicate that patches created from PMAFs have the potential to affect the satellite communications environment in the central polar cap region.
Key Points
Simultaneous observations of PMAF and polar cap patches near the cusp
Patches are directly and seamlessly produced from PMAF
PMAF‐generated patches are low density but accompanied by irregularities
•S-N curve and fracture toughness of a carbon steel were studied in hydrogen gas.•Degradation of fatigue life was dependent on the hydrogen gas pressure.•Peculiar flat fatigue fracture surface was ...formed in high-pressure hydrogen.•Microscopic fracture morphologies in those two tests were well consistent.•A unified mechanism was proposed to describe all the fracture behaviors.
To investigate the effect of hydrogen on fatigue life characteristics and crack growth behaviors through the entire fatigue life of a carbon steel, tension-compression fatigue tests and elasto-plastic fracture toughness tests were conducted in a hydrogen gas environment under the pressures of 0.7 and 115MPa. The fatigue tests revealed that the fatigue life and fracture morphology vary drastically with the hydrogen gas pressure. This study demonstrates that such differences can be explained by the combination of fatigue crack growth properties and fracture toughness properties in hydrogen gas at each pressure.
The observation of slow‐slip, seismic tremor, and low‐frequency earthquakes at subduction margins has provided new insight into the mechanisms by which stress accumulates between large subduction ...(megathrust) earthquakes. However, the relationship between the physical properties of the subduction interface and the nature of the controls on interplate seismic coupling is not fully understood. Using magnetotelluric data, we show in situ that an electrically resistive patch on the Hikurangi subduction interface corresponds with an area of increased coupling inferred from geodetic data. This resistive patch must reflect a decrease in the fluid or sediment content of the interface shear zone. Together, the magnetotelluric and geodetic data suggest that the frictional coupling of this part on the Hikurangi margin may be controlled by the interface fluid and sediment content: the resistive patch marking a fluid‐ and sediment‐starved area with an increased density of small, seismogenic‐asperities, and therefore a greater likelihood of subduction earthquake nucleation.
Key Points
Heterogeneous resistivity structure imaged on the plate interface on the Hikurangi subduction margin
Resistivity structure correlates with plate coupling inferred by geodetic data
The frictional coupling of the northern Hikurangi margin may be controlled by the interface fluid and sediment content
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