Proton Flux Research Articles

Measurements of proton beam flux and energy of APEP using foil activation technique

The activation method of metallic foils is an important technique to measure the flux and energy of proton beams. In this paper, the method was used to measure the CSNS APEP proton flux at seven nominal proton energies ranging from 10 MeV to 70 MeV for beam spot sizes of the 20 mm × 20 mm and 50 mm × 50 mm. The reactions of natTi(p, x)48V, natNi(p, x)57Ni, natCu(p, x)58Co, and 27Al(p, x)24Na were employed to measure the proton beam flux with a range of 107-109 p/cm2/s. Furthermore, we also proposed a method using the activity ratio with a stacked-foil target to determine the energy spread of a Gaussian-like distribution for different nominal proton energies. The optimal combinations of Al, Cu, Ti, Ni, Mo, Fe, Nb, and In foils were adopted for the proton energies. The measured energy spreads for degraded beams of 30 MeV–70 MeV were found to be smaller than 10.00%.

In Situ Spectroscopic Detection of Large-Scale Reorientations of Transmembrane Helices During Influenza A M2 Channel Opening.

Viroporins are small ion channels in membranes of enveloped viruses that play key roles during viral life cycles. To use viroporins as drug targets against viral infection requires in-depth mechanistic understanding and, with that, methods that enable investigations under in situ conditions. Here, we apply surface-enhanced infrared absorption (SEIRA) spectroscopy to Influenza A M2 reconstituted within a solid-supported membrane, to shed light on the mechanics of its viroporin function. M2 is a paradigm of pH-activated proton channels and controls the proton flux into the viral interior during viral infection. We use SEIRA to track the large-scale reorientation of M2's transmembrane α-helices in situ during pH-activated channel opening. We quantify this event as a helical tilt from 26° to 40° by correlating the experimental results with solid-state nuclear magnetic resonance-informed computational spectroscopy. This mechanical motion is impeded upon addition of the inhibitor rimantadine, giving a direct spectroscopic marker to test antiviral activity. The presented approach provides a spectroscopic tool to quantify large-scale structural changes and to track the function and inhibition of the growing number of viroporins from pathogenic viruses in future studies.

In situ‐spektroskopische Detektion der weitreichenden Reorientierung von Transmembranhelices während der Öffnung des Influenza A M2‐Kanals**

AbstractViroporine sind kleine Ionenkanäle in Membranen umhüllter Viren, die Schlüsselrollen in viralen Lebenszyklen spielen. Um Viroporine als Wirkstoffziele zur Bekämpfung von Virusinfektionen nutzen zu können, bedarf es eines umfassenden Verständnisses ihrer Funktionsweise. Hierfür sind wiederum Methoden notwendig, die ihre Untersuchung unter in situ‐Bedingungen ermöglichen. In dieser Arbeit nutzen wir die oberflächenverstärkte Infrarotabsorptionsspektroskopie (SEIRA, engl. surface‐enhanced infrared absorption), um den Mechanismus der Viroporinfunktion von Influenza A M2 in einer trägergestützten Membran zu untersuchen. M2 ist ein Paradebeispiel pH‐aktivierter Protonenkanäle, das den Protonenfluss in das Virusinnere während einer Virusinfektion kontrolliert. Mit Hilfe von SEIRA verfolgen wir die weitreichende Reorientierung der transmembranen α‐Helices von M2 in situ während der pH‐aktivierten Kanalöffnung. Wir quantifizieren dieses Ereignis als eine helikale Neigung von 26° zu 40° durch eine Korrelation der experimentellen Ergebnisse mit rechnergestützter Spektroskopie basierend auf Strukturen aus Festkörper‐Kernspinresonanzspektroskopie. Die mechanische Bewegung wird durch die Zugabe des Inhibitors Rimantadin verhindert, was somit einen direkten spektroskopischen Marker zum Testen der antiviralen Aktivität darstellt. Der hier vorgestellte Ansatz bietet somit ein spektroskopisches Werkzeug zur Quantifizierung großskaliger Strukturänderungen und zum Beobachten der Funktion und Inhibition einer wachsenden Zahl von Viroporinen aus pathogenen Viren.

Temporal Structures in Positron Spectra and Charge-Sign Effects in Galactic Cosmic Rays.

We present the precision measurements of 11years of daily cosmic positron fluxes in the rigidity range from 1.00 to 41.9GV based on 3.4×10^{6} positrons collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The positron fluxes show distinctly different time variations from the electron fluxes at short and long timescales. A hysteresis between the electron fluxes and the positron fluxes is observed with a significance greater than 5σ at rigidities below 8.5GV. On the contrary, the positron fluxes and the proton fluxes show similar time variation. Remarkably, we found that positron fluxes are modulated more than proton fluxes with a significance greater than 5σ for rigidities below 7GV. These continuous daily positron fluxes, together with AMS daily electron, proton, and helium fluxes over an 11-year solar cycle, provide unique input to the understanding of both the charge-sign and mass dependencies of cosmic rays in the heliosphere.

Application of LiMgPO4 crystal for proton beam quality control in radiotherapy.

The radioluminescence (RL) emitted by LiMgPO4 detector under proton beam irradiation was investigated in real time at the radiotherapy facility in the Institute of Nuclear Physics Polish Academy of Sciences in Krakow. The facility uses protons accelerated by the AIC-144 isochronous cyclotron up to the energy of 60MeV. The measurements of RL were carried out using a remote optical fiber device with a luminophore detector and photomultiplier located at opposite ends of the optical fiber. A thin slice of LiMgPO4 doped with Tm (1.2mol%) crystal was exposed to the proton beam. The tested detector allowed for the measurement of proton beam current, flux fluence and determination of proton beam time structure parameters. The investigation of LiMgPO4 crystal showed its high sensitivity, fast reaction time to irradiation and possibility of application as the detector for control of proton beam parameters.

Turbulence Properties of Interplanetary Coronal Mass Ejections in the Inner Heliosphere: Dependence on Proton Beta and Flux Rope Structure

Interplanetary coronal mass ejections (ICMEs) have low proton beta across a broad range of heliocentric distances and a magnetic flux rope structure at large scales, making them a unique environment for studying solar wind fluctuations. Power spectra of magnetic field fluctuations in 28 ICMEs observed between 0.25 and 0.95 au by Solar Orbiter and Parker Solar Probe have been examined. At large scales, the spectra were dominated by power contained in the flux ropes. Subtraction of the background flux rope fields increased the mean spectral index from −5/3 to −3/2 at kd i ≤ 10−3. Rope subtraction also revealed shorter correlation lengths in the magnetic field. The spectral index was typically near −5/3 in the inertial range at all radial distances regardless of rope subtraction and steepened to values consistently below −3 with transition to kinetic scales. The high-frequency break point terminating the inertial range evolved approximately linearly with radial distance and was closer in scale to the proton inertial length than the proton gyroscale, as expected for plasma at low proton beta. Magnetic compressibility at inertial scales did not show any significant correlation with radial distance, in contrast to the solar wind generally. In ICMEs, the distinctive spectral properties at injection scales appear mostly determined by the global flux rope structure while transition-kinetic properties are more influenced by the low proton beta; the intervening inertial range appears independent of both ICME features, indicative of a system-independent scaling of the turbulence.

Solar–Stellar Connection: X-Ray Flares to Energetic (E > 10 MeV) Particle Events

Energetic particle environments are an important factor for the viability of life on exoplanets surrounding flare stars. In the heliosphere, large gradual solar energetic (E > 10 MeV) particle (SEP) events are produced by shocks from fast coronal mass ejections (CMEs). Extensive observations of solar X-ray flares, CMEs, and SEP events can provide guidance for flare star models of stellar energetic particle (StEP) events, for which stellar flares, but only rarely the associated CMEs, are observed. Comparing an extensive list of peak fluxes, timescales, and peak temperatures of 585 ≥ M3.0 solar X-ray flares with the occurrence of associated SEP events of peak flux Ip > 1.4 proton flux units, enhanced with proxy decametric–hectometric type II radio bursts, we determine guidelines for StEP event outcomes, given only stellar X-ray flare inputs. Longer timescales and lower peak temperatures of X-ray flares with a given peak X-ray flux Fp are more favorable for occurrence of associated SEP/StEP events, which, however, are only a minority of all solar flare outcomes. Most solar flares do not result in SEP events, invalidating scaling laws between stellar flares, CMEs, and StEP events. We discuss recent observations and models of the flare–CME relationship and suggest that StEP intensities Ip may often be overestimated.

Ion Acceleration by Foreshock Bubbles: Magnetospheric Multiscale Observations

AbstractForeshock bubbles (FBs) occur when interplanetary magnetic field discontinuities encounter the Earth's foreshock. These transient (∼1 to 5 min) features exhibit depressed densities and magnetic field strengths, enhanced temperatures, and deflected plasma flows trailed by a region of enhanced plasma density and magnetic field strength. Ions can be accelerated inside the FBs through the Fermi acceleration process. Hybrid simulations and test particle calculations predict that the maximum energies of ions accelerated by FBs reach 5.6 times the solar wind ram energy (Esw). We identify 23 FBs from September 2015 to January 2020 Magnetospheric Multiscale spacecraft observations. Most FBs (17 of 23) occurred upstream of the dusk‐side bow shock and above the ecliptic. The FBs occurred for Alfvn Mach numbers ranging from 5 to 15, with 11 FBs having an Alfvn Mach number near 10. To investigate ion energization inside the cores of the FBs we compare the proton spectra observed by the Hot Plasma Composition Analyzer and Energetic Ion Spectrometer before (upstream), during (core), and after (downstream) the FBs. The proton intensities at energies from Esw (the solar wind ram energy, ) up to about 5.6Esw are greater inside than outside 19 of 23 FBs, confirming that FBs can accelerate particles to these energies. The proton flux intensities at energies between Esw and 5.6Esw in the core of the FBs are consistent with results from global hybrid simulations for ion energization from FBs through second‐order Fermi acceleration.

Multipoint Detection of GRB221009A’s Propagation through the Heliosphere

We present the results of processing the effects of the powerful gamma-ray burst GRB221009A captured by the charged particle detectors (electrostatic analyzers and solid-state detectors) on board spacecraft at different points in the heliosphere on 2022 October 9. To follow the GRB221009A propagation through the heliosphere, we used the electron and proton flux measurements from solar missions Solar Orbiter and STEREO-A; Earth’s magnetosphere and solar wind missions THEMIS and Wind; meteorological satellites POES15, POES19, and MetOp3; and MAVEN—a NASA mission orbiting Mars. GRB221009A had a structure of four bursts: the less intense Pulse 1—the triggering impulse—was detected by gamma-ray observatories at T 0 = 13:16:59 UT (near the Earth); the most intense Pulses 2 and 3 were detected on board all the spacecraft from the list; and Pulse 4 was detected in more than 500 s after Pulse 1. Due to their different scientific objectives, the spacecraft, whose data were used in this study, were separated by more than 1 au (Solar Orbiter and MAVEN). This enabled the tracking of GRB221009A as it was propagating across the heliosphere. STEREO-A was the first to register Pulse 2 and 3 of the GRB, almost 100 s before their detection by spacecraft in the vicinity of Earth. MAVEN detected GRB221009A Pulses 2, 3, and 4 at the orbit of Mars about 237 s after their detection near Earth. By processing the observed time delays, we show that the source location of the GRB221009A was at R.A. 288.°5, decl. 18.°5 ± 2° (J2000).

Role of alpha particles in penetration of solar wind diamagnetic structures into the magnetosphere

We present the results of studies showing the presence of simultaneous jumps in the density of protons (N2/N1)p and alpha particles (N2/N1)α at the boundaries of diamagnetic structures (DS) of various types both in the quasi-stationary slow solar wind (SW) and in sporadic SW. For DS of quasi-stationary slow SW, associated with streamer belt or chains, in the statistics considered in the paper there is a single linear dependence of (N2/N1)α on (N2/N1)p. This means that these jumps have the same physical nature and are related to diamagnetism at the boundaries of DS of quasi-stationary SW streams of various types.
 At the front of interplanetary shock waves (ISW), the (N2/N1)α jump is approximately twice as large as the (N2/N1)p jump. This reflects the features of the collective collisionless plasma heating at ISW fronts and requires further studies. A maximum excess (almost 3 times) of the increase in the alpha-particle density (N2/N1)α over the increase in the proton density (N2/N1)p is observed in eruptive prominences.
 The magnetospheric response in such phenomena as auroras, proton and alpha particle fluxes, geomagnetic field, and geomagnetic pulsations is similar under the influence of DS of various types and ISW. The detected features of the magnetospheric response to the contact with DS of different types and ISW can be interpreted as impulsive passage of the DS matter (plasmoid) into the magnetosphere.
 The results of studies of the (N2/N1)α jumps can be used as an additional important argument in identifying cases of impulsive penetration of DS into the magnetosphere and in examining the physical nature of these penetrations.

Роль альфа-частиц в проникновении диамагнитных структур солнечного ветра внутрь магнитосферы

We present the results of studies showing the presence of simultaneous jumps in the density of protons (N2/N1)p and alpha particles (N2/N1)α at the boundaries of diamagnetic structures (DS) of various types both in the quasi-stationary slow solar wind (SW) and in sporadic SW. For DS of quasi-stationary slow SW, associated with streamer belt or chains, in the statistics considered in the paper there is a single linear dependence of (N2/N1)α on (N2/N1)p. This means that these jumps have the same physical nature and are related to diamagnetism at the boundaries of DS of quasi-stationary SW streams of various types.
 At the front of interplanetary shock waves (ISW), the (N2/N1)α jump is approximately twice as large as the (N2/N1)p jump. This reflects the features of the collective collisionless plasma heating at ISW fronts and requires further studies. A maximum excess (almost 3 times) of the increase in the alpha-particle density (N2/N1)α over the increase in the proton density (N2/N1)p is observed in eruptive prominences.
 The magnetospheric response in such phenomena as auroras, proton and alpha particle fluxes, geomagnetic field, and geomagnetic pulsations is similar under the influence of DS of various types and ISW. The detected features of the magnetospheric response to the contact with DS of different types and ISW can be interpreted as impulsive passage of the DS matter (plasmoid) into the magnetosphere.
 The results of studies of the (N2/N1)α jumps can be used as an additional important argument in identifying cases of impulsive penetration of DS into the magnetosphere and in examining the physical nature of these penetrations.

Production rates of cosmogenic nuclides in extraterrestrial material using GEANT4 software

AbstractWe present a model for the calculation of the production rates of cosmogenic nuclides in extraterrestrial material. The model is based on the Monte Carlo simulation software Geant4. Using this software an application simulating the irradiation of the spherical body with predefined chemical composition by galactic cosmic-ray protons was developed. The fluxes of secondary neutrons and protons generated within the body of the sample are calculated. These are further used for the calculation of the production rates for cosmogenic nuclides. The plausibility of the presented model was tested in case of the well-studied meteoritic sample Knyahinya for which the production rates of cosmogenic nuclides were previously measured and also calculated using MCNP simulation software. The production rates for 3He, 10Be, 21Ne, 22Ne, 26Al, 36Cl, 38Ar, 39Ar, 41Ca and 53Mn have been calculated in Knyahinya meteorite and for 10Be, 26Al and 36Cl in Apollo 17 sample 73,002.

Magnetic Reconnection in the Martian Magnetotail: Occurrence Rate and Impact on Ion Loss

AbstractThe current sheet is crucial in releasing magnetic free energy in cosmic plasmas via fast magnetic reconnection or wave excitation. This research investigates the characteristics of the Martian tail current sheet by analyzing data acquired from the Mars Atmosphere and Volatile EvolutioN spacecraft over 7 years. For the first time, we find that approximately 15% of the current sheet events display reconnection signatures, including Hall magnetic fields and fast proton flows. These reconnecting current sheets are detected more frequently on Mars than on Earth. The Martian tail current sheet is first demonstrated to be on the proton scale, which can explain the high reconnection occurrence rate. The research also reveals that the current sheets are thinner in regions closer to Mars and in the –E hemisphere. On average, reconnecting current sheets carry high fluxes of protons rather than oxygen ions.

Propionic and valproic acids have an impact on bacteria viability, proton flux and ATPase activity.

Short-chain fatty acids like propionic (PPA) and valproic acids (VP) can alter gut microbiota, which is suggested to play a role in development of autism spectrum disorders (ASD). In this study we investigated the role of various concentrations of PPA and VP in gut enteric gram-negative Escherichia coli K12 and gram-positive Enterococcus hirae ATCC 9790 bacteria growth properties, ATPase activity and proton flux. The specific growth rate (µ) was 0.24h-1 and 0.82h-1 in E. coli and E. hirae, respectively. Different concentrations of PPA reduced the value of µ similarly in both strains. PPA affects membrane permeability only in E. hirae. PPA decreased DCCD-sensitive ATPase activity in the presence of K+ ions by 20% in E. coli and 40% in E. hirae suggesting the importance of the FOF1-K+ transport system in the regulation of PPA-disrupted homeostasis. Moreover, the H+ flux during PPA consumption could be the protective mechanism for enteric bacteria. VP has a selective effect on the µ depending on bacteria. The overwhelming effect of VP was detected on the K+-promoted ATPase activity in E. hirae. Taken together it can be suggested that PPA and VP have a disruptive effect on E. coli and E. hirae growth, viability, bioenergetic and biochemical properties, which are connected with the alteration of FOF1-ATPase activity and H+ flux rate or direction.

Europa's Perturbed Fields and Induced Dipole Affect Energetic Proton Depletions During Distant Alfvén Wing Flybys

AbstractWe investigate the causes of energetic proton (80–540 keV) depletions measured during the two most distant flybys of Europa by Galileo, E17 and E25A, which encountered the Alfvén wings. First, by simulating the proton flux with a Monte Carlo particle tracing code we investigate the effect of: electromagnetic field perturbations, the induced dipole, atmospheric charge exchange and plumes. Inhomogeneous fields associated with the Alfvén wings and the ionosphere strongly affect the depletions. For homogeneous fields the depletion along the trajectory is focused on a narrow pitch angle range and has no structure, whereas the depletion for perturbed (inhomogeneous) fields represents a wider and complex structure. Furthermore, also the induced dipole alters the depletion structure. The effect of plumes (density 2.5 × 1015 m−3) and charge exchange on the proton depletion is minor. Second, we compare the simulations to the proton measurements. The simulations with inhomogeneous fields describe the data qualitatively better than the homogeneous case, suggesting that indeed field perturbations are responsible for the measured losses. We attribute discrepancies between the simulations and the proton measurements to discrepancies between the simulated and real fields. We argue that simulating the fields along the trajectory is a good first step, but that ideally the energetic ion flux is reconstructed well to gain confidence in the interpretation of the simulated magnetic field. In conclusion, energetic ion observations along distant flybys through the Alfvén wings are suitable for isolating the characteristics of the global configuration of the magnetospheric interaction region of Europa (or other moons).

A Computational Model to Optimize the Electrochemical Reduction of CO2 to Formic Acid Using an Enzymatic Catalyst

This work documents the development and subsequent analysis of a transient electrochemical model to predict the electrochemical conversion of CO2 to formic acid (FA) using an enzymatic catalyst. FA has been of recent interest for its applications in hydrogen storage and formic acid-based fuel cells [1]. This process uses an electrochemical charge mediator, commonly methyl viologen (MV) or ethyl viologen (EV) [2], which is initially reduced to a more negative species (i.e. from EV2+ to EV+), then re-oxidized upon reacting with the enzymatic catalyst to produce FA (as HCOO-) from CO2 and protons from the anode.Using an enzymatic catalyst can enable greater selectivity to a particular carbon product compared to traditional metal-based catalysts, which can produce an array of different products [3]. The model was developed in conjunction with experimental investigation to serve as a benchmark for the optimal product conversion of CO2 assuming a stable solution pH and catalyst stability. The model employs transport-based equations for each ionic species of the charge carrier, which will vary based on the initial concentration selected and the applied voltage. Kinetic parameters to determine reaction values are fit to align with existing experimental data.The model uses Butler-Volmer kinetics to estimate the total current in the system as a function of the applied voltage and as a function of estimated experimental parameters. A bulk solution is considered for the electrolytes, but species concentrations are varied across a small diffusion layer (~50 um) between the electrolyte and electrode [4]. For predicting the conversion of CO2 into FA using the enzymatic catalyst and charge carrier species, Michaelis-Menten kinetics are used with appropriate catalyst parameters derived using sampling reactions with a known potassium formate solution and UV-vis spectroscopy.Among the products formed, molecular O2 is factored into the model as it will adversely limit the maximum current in the cell at higher applied voltage, and subsequently will limit the rate of production and efficiency. An O2 scavenger, such as sodium thiosulfate, can limit the contribution of molecular oxygen in the solution, but will not eliminate it. The model assumes that pH remains constant due to the presence of electrolyte buffer in the solution, although the influx of protons will cause a drop in the pH if not immediately converted to FA, and this more acidic solution has been shown to be a significant limitation due to the performance and stability of the catalyst.The results can be analyzed as a function of multiple parameters and operating conditions, although among the most interesting to study are those for the applied voltage and initial charge carrier concentration. There, it can be shown on contour plots that optimal regions for efficiency exist around -0.8 to -1.1 V (vs. Ag/AgCl), and charge carrier concentrations of 0.1 – 10 mM. The trends obtained are in alignment with what has previously been hypothesized [2] but can now also be analyzed in conjunction with other experimental parameters, including the design (sizing) of the electrochemical cell.The primary benefits of the model are in (1) predicting optimal performance when experimental imperfections are removed, (2) rapidly predicting a range of product selectivity and efficiency due to limited resources used to run experiments, primarily for the catalyst, and (3) providing a templating a template with which to iterate upon and consider other value added products, by altering parameters to account for a different catalyst, electrolyte, or charge mediator. The model is presently being developed to include provisions for operating in a flow cell reactor, where considerations to flow rate must be considered and time delay between reduction and production cells. To best match with existing experimental data, additional effects such as pH deterioration and variations in the kinetics with voltage (which can be investigated by cyclic voltammetry experiments) will need to be considered. REFERENCES: Singh AK, Singh S, Kumar A. Hydrogen energy future with formic acid: a renewable chemical hydrogen storage system. Catalysis Science & Technology. 2016;6(1):12-40.Moreno D, Thompson J, Omosebi A, Landon J, Liu K. Electrochemical analysis of charge mediator product composition through transient model and experimental validation. Journal of Applied Electrochemistry. 2022 Nov;52(11):1573-84.Ikeyama S, Amao Y. An Artificial Co‐enzyme Based on the Viologen Skeleton for Highly Efficient CO2 Reduction to Formic Acid with Formate Dehydrogenase. ChemCatChem. 2017 Mar 8;9(5):833-8.Morrison AR, van Beusekom V, Ramdin M, van den Broeke LJ, Vlugt TJ, de Jong W. Modeling the electrochemical conversion of carbon dioxide to formic acid or formate at elevated pressures. Journal of The Electrochemical Society. 2019 Feb 12;166(4):E77. Figure 1

Modeling Chemical Microenvironments in Porous Copper Electrodes for CO2 Reduction at Elevated Current Densities

Electrochemical CO2 reduction (CO2R) presents a promising pathway toward the reuse of CO2 emitted during the production of industrial commodities (e.g., cement, steel, and plastics) to form value-added commodities and fuels at ambient temperatures and pressures with renewably generated electrons. Copper (Cu) catalysts demonstrate the ability to convert CO2 to multicarbon (C2+) products. Additionally, 3-D structured porous Cu electrodes can facilitate the operation of CO2R to C2+ at significantly elevated current densities by enhancing the delivery of CO2 to catalytic active sites on Cu, offering the potential to translate lab-scale understanding to industrial operation. Nonetheless, there still exist selectivity limitations in porous electrode systems due to poor control of the chemical microenvironment, (i.e., the local pH, CO2 activity, and CO intermediate management), in these complex electrodes. Therefore, resolving microenvironment in porous Cu electrodes will be critical to advancing these systems towards industrialization.In this talk, we explore the use of continuum modeling to resolve and understand the effects of mass transfer and chemical environment in electrochemical CO2 reduction in porous Cu electrodes. We explore two scenarios of porous Cu electrodes performing electrochemical CO2 reduction. The first is the operation of a device employing a bipolar membrane (BPM) in reverse bias, wherein modeling reveals that the proton flux generated by the BPM substantially lowers the pH of the porous electrode and promotes selective CH4 and HCOOH generation. The second is the use of a micro-structured porous electrode that employs an anion-exchange membrane and more selectively generates C2+ products. 2-D modeling reveals heterogeneities in the porous electrode enable hotspots of increased pH that locally enhance C2+ selectivity. Ultimately, this talk underscores the powerful ability of continuum modeling to resolve microenvironments at spatial resolutions beyond what is achievable experimentally, as well as to link changes in microenvironment to changes in local selectivity. These simulations will rationalize and guide the engineering of microenvironment in next-generation porous electrodes for CO2 reduction to C2+ products at industrial scales.

Global ozone loss following extreme solar proton storms based on the July 2012 coronal mass ejection

Large solar coronal mass ejections pose a threat in the near-Earth space. As a cause of extreme periods of space weather, they can damage satellite-based communications and create geomagnetically induced currents in power and energy grids. Further, the solar wind energetic particles can reduce the protecting layer of atmospheric ozone and pose a threat to life on Earth. The large coronal mass ejection (CME) of July 2012, although directed away from the Earth, is often highlighted as a prime example of a potentially devastating super storm. Here we show, based on proton fluxes recorded by the instruments aboard the STEREO-A satellite, that the atmospheric response to the July 2012 event would have been comparable to those of the largest solar proton events of the satellite era. Significant impact on total ozone outside polar regions would require a much larger event, similar to those recorded in historical proxy data sets. Such an extreme event would cause long-term ozone reduction all the way to the equator and increase the size, duration, and depth of the Antarctic ozone hole. The impact would be comparable to predicted drastic and sudden ozone reduction from major volcanic eruptions, regional nuclear conflicts, or long-term stratospheric geoengineering.

Simultaneous Observation of Whistler‐Mode Chorus and Fast Magnetosonic Waves During the Magnetic Peak in the Inner Magnetosphere

AbstractSimultaneous observations of whistler‐mode chorus and magnetosonic (MS) waves are reported within a magnetic peak in the inner magnetosphere for the first time. During the magnetic peak, Van Allen Probe A observes flux enhancements of both ring current electrons and relativistic electrons, while medium‐energy proton fluxes are reduced but high‐energy proton fluxes are raised. Those flux variations of ring current particles are almost concentrated in the perpendicular direction of the background magnetic field, leading to enhancements of the electron temperature anisotropy and a positive gradient of proton velocity distributions. The calculated linear growth rates show that unstable electrons with temperature anisotropic instabilities and unstable protons with ring distribution during the magnetic peak structure can provide free energy for the excitation of whistler‐mode chorus and MS waves, respectively. Our findings suggest that injected particles encountering the magnetic peak structure may form more complex unstable electron and ion distributions driving multiple instabilities simultaneously.

Sensitivity investigation of 100-MeV proton irradiation to SiGe HBT single event effect

The single event effect (SEE) sensitivity of silicon–germanium heterojunction bipolar transistor (SiGe HBT) irradiated by 100-MeV proton is investigated. The simulation results indicate that the most sensitive position of the SiGe HBT device is the emitter center, where the protons pass through the larger collector-substrate (CS) junction. Furthermore, in this work the experimental studies are also carried out by using 100-MeV proton. In order to consider the influence of temperature on SEE, both simulation and experiment are conducted at a temperature of 93 K. At a cryogenic temperature, the carrier mobility increases, which leads to higher transient current peaks, but the duration of the current decreases significantly. Notably, at the same proton flux, there is only one single event transient (SET) that occurs at 93 K. Thus, the radiation hard ability of the device increases at cryogenic temperatures. The simulation results are found to be qualitatively consistent with the experimental results of 100-MeV protons. To further evaluate the tolerance of the device, the influence of proton on SiGe HBT after gamma-ray (60Coγ) irradiation is investigated. As a result, as the cumulative dose increases, the introduction of traps results in a significant reduction in both the peak value and duration of the transient currents.