The electron rolling‐pin distribution, showing electron pitch angles primarily at 0°, 90°, and 180°, has been widely studied in the Earth's magnetosphere, but has never been reported in other ...planetary environments. Here, by utilizing the Jupiter Near‐polar Orbiter (Juno) measurements, we report for the first time the electron rolling‐pin distribution in Jupiter's magnetosphere. We reveal the energy range of such distribution and find it appears only above 19.5 keV, falling well into the suprathermal energy range. Moreover, we quantitively reproduce the formation processes of such distribution by using an analytical model. Gratifyingly, the distribution derived from the analytical model agrees well with the Juno observations, indicating such distribution is formed by the combination of global‐scale Fermi acceleration and local‐scale betatron acceleration. These results, demonstrating that the electron rolling‐pin distribution exists beyond the Earth, can improve our knowledge of electron dynamics in planetary magnetosphere.
Plain Language Summary
Examining the electron pitch angle distribution can help us better understand the electron dynamics in planetary magnetosphere. Up to now, it still remains unknown whether the rolling‐pin distribution, which shows pitch angles primarily at 0°, 90°, and 180°, exists beyond the Earth. Here using the Juno measurements, for the first time, we report such distribution in the Jupiter's magnetosphere. We find the rolling‐pin distribution appears only in the suprathermal electrons, and further explain its formation processes by using an analytical model. Our study is useful to understand electron dynamics in planetary magnetosphere.
Key Points
We for the first time provide the evidence of electron rolling‐pin distribution in Jupiter's magnetosphere
The rolling‐pin distribution appears only above 19.5 keV, falling well into the suprathermal energy range
The rolling‐pin distribution is formed by the combination of global‐scale Fermi acceleration and local‐scale betatron acceleration
As the world seeks to become more sustainable, intelligent solutions are needed to increase the penetration of renewable energy. In this paper, the model-free deep reinforcement learning algorithm ...Rainbow Deep Q-Networks is used to control a battery in a microgrid to perform energy arbitrage and more efficiently utilise solar and wind energy sources. The grid operates with its own demand and renewable generation, as well as dynamic energy pricing from a real wholesale energy market. Four scenarios are tested including using demand and price forecasting produced with local weather data. The algorithm and its subcomponents are evaluated against an actor-critic method and a linear programming model with Rainbow able to outperform all other methods. This research shows the importance of using the distributional approach for reinforcement learning for complex environments, as well as how it can visualise and contextualise the agents’ behaviour for real-world applications.
•Novel use of Rainbow Deep Q-Networks for demand response.•Proposed algorithm outperforms continuous actor-critic method and linear model.•Visualise benefit of using distributional approach for complex problems.•Nonlinear efficiency profiles considered in hybrid AC/DC microgrid.
Abstract
Magnetic flux ropes or magnetic islands are important structures responsible for electron acceleration and energy conversion during turbulent reconnection. However, the evolution of flux ...ropes and the corresponding electron acceleration process still remain open questions. In this paper, we present a comparative study of flux ropes observed by the Magnetospheric Multiscale mission in the outflow region during an example of turbulent reconnection in Earth's magnetotail. Interestingly, we find the farther the flux rope is away from the X-line, the bigger the size of the flux rope and the slower it moves. We estimate the power density converted at the observed flux ropes via the three fundamental electron acceleration mechanisms: Fermi, betatron, and parallel electric field. The dominant acceleration mechanism at all three flux ropes is the betatron mechanism. The flux rope that is closest to the X-line, having the smallest size and the fastest moving velocity, is the most efficient in accelerating electrons. Significant energy also returns from particles to fields around the flux ropes, which may facilitate the turbulence in the reconnection outflow region.
In this paper, we presented two observational cases and simulations to indicate the relationship between the formation of butterfly‐like electron pitch angle distributions and the emission of ...low‐harmonic (LH) fast magnetosonic (MS) waves inside the high‐density plasmasphere. In the wave emission region, the pitch angle of relativistic (>1 MeV) electrons becomes obvious butterfly‐like distributions for both events (near‐equatorially mirroring electrons are transported to lower pitch angles). Unlike relativistic (>1 MeV) electrons, energetic electrons (<1 MeV) change slightly, except that relatively low‐energy electrons (<~150 keV) show butterfly‐like distributions in the 21 August 2013 event. In theory, the LH MS waves can affect different‐energy electrons through the bounce resonance, Landau resonance, and transit time scattering. By performing the Fokker‐Planck diffusion simulations, we demonstrate that the bounce resonance with the LH MS waves mainly leads to the butterfly pitch angle distribution of MeV electrons, whereas the Landau resonance and transit time scattering mainly affect energetic electrons in the high‐density region.
Key Points
Low‐harmonic (LH) magnetosonic (MS) waves and butterfly distributions are observed inside the plasmasphere
LH MS waves lead to the butterfly pitch angle distribution of MeV electrons via bounce resonance
Landau resonance and transit time scattering are mainly effective for scattering the electrons below 1 MeV
With high‐resolution data of the recently launched Magnetospheric Multiscale mission, we report a magnetic reconnection event at the dayside magnetopause. This reconnection event, having a density ...asymmetry Nhigh/Nlow ≈ 2 on the two sides of the reconnecting current sheet and a guide field Bg ≈ 0.4B0 in the “out‐of‐plane” direction, exhibit all the two‐fluid features: Alfvenic plasma jets in the outflow region, bipolar Hall electric fields toward the current sheet center, quadrupolar Hall magnetic fields in the “out‐of‐plane” direction, and the corresponding Hall currents. Obviously, the density asymmetry Nhigh/Nlow ≈ 2 and the guide field Bg ≈ 0.4B0 are not sufficient to dismiss the quadrupolar pattern of Hall reconnection. This is different from previous simulations, where the bipolar pattern of Hall reconnection was suggested.
Key Points
Asymmetric guide‐field reconnection is observed at the magnetopause
This reconnection is characterized by Hall pattern and Alfvenic plasma jet
Symmetric Hall magnetic and electric fields were found in this event
The rolling‐pin distribution of suprathermal electrons (40–200 keV), showing electron pitch angles primarily at 0°, 90°, and 180°, has recently been reported behind dipolarization fronts (DFs) both ...in observations and simulations. The formation of such type of distribution, however, has been unclear so far. In this study, we present an observation of such type of distribution by Cluster in the magnetotail behind a DF. We interpret the formation of such distribution using the global‐scale Fermi acceleration together with local‐scale betatron acceleration. We quantitatively reproduce these two processes and therefore the rolling‐pin distribution of suprathermal electrons using an analytical model. We further reveal that only at energies higher than 26 keV can such distribution be formed. This study, quantitatively explaining the formation of rolling‐pin distribution, can improve the understanding of electron dynamics behind DFs.
Key Points
The rolling pin distribution of suprathermal electrons is studied
It is a consequence of global‐Fermi and local‐betatron acceleration
It can only be formed at energies higher than 26 keV
This paper presents a dynamic plasmapause location model established based on 5 years of Time History of Events and Macroscale Interactions during Substorms (THEMIS) measurements from 2009 to 2013. ...In total, 5878 plasmapause crossing events are identified, sufficiently covering all 24 magnetic local time (MLT) sectors. Based on this plasmapause crossing database, we investigate the correlations between plasmapause locations with solar wind parameters and geomagnetic indices. Input parameters for the best fits are obtained for different MLT sectors, and finally, we choose five input parameters to build a plasmapause location model, including 5 min‐averaged SYM‐H, AL, and AU indices as well as hourly‐averaged AE and Kp indices. two out‐of‐sample comparisons on the evolution of the plasmapause is shown during two magnetic storms, demonstrating good agreement between model results and observations. Two major advantages are achieved by this model. First, this model provides plasmapause locations at 24 MLT sectors, still providing good consistency with observations. Second, this model is able to reproduce dynamic variations of the plasmapause on timescales as short as 5 min.
Key Points
A dynamic plasmapause model established based on THEMIS measurement is presented
This model calculates plasmapause locations at 24 MLT sector independently
This model can reproduce dynamic variations of plasmapause in the timescale as short as 5 min
The Earth's magnetopause is an ion‐scale boundary that separates the magnetosphere from the shocked solar wind. At such boundary, energy‐conversion processes frequently occur. Previous studies ...suggested that such energy conversions are related to the magnetic reconnection process. Here, we report a new mechanism that the coaction between the twisted magnetic structure and lower‐hybrid waves can also drive energy conversion (J⋅ E, J is current density and E is electric field) at the magnetopause boundary layer, by using high‐resolution measurements of the four Magnetospheric Multiscale spacecraft. We find that such energy conversion is efficient (with magnitude up to 20 nW/m3) and is attributed to an intense current filament (j ≈ 3,800 nA/m2) and a fluctuating electric field driven by lower‐hybrid waves. With the help of the First‐Order Taylor Expansion method, we find that the intense current filament is driven by a twisted magnetic structure at electron scale. Our study improves the understanding of energy‐conversion processes at the Earth's magnetopause.
Plain Language Summary
Solar wind‐magnetosphere coupling is a key process during the solar‐terrestrial energy chain and the space weather forecast. A significant amount of the solar wind energy is converted at the Earth's magnetopause, and thus, uncovering the mechanism of energy‐conversion processes is of key importance in understanding such a coupling process between solar wind and magnetosphere. Here, we report a new mechanism that the coaction between the twisted magnetic structure and fluctuating electric field can also drive energy conversion. It's found that the energy conversion is efficient and is attributed to an intense current filament driven by the twisted magnetic structure and a fluctuating electric field provided by lower‐hybrid waves.
Key Points
An intense current filament (up to 3,800 nA/m2) accompanied by energy conversion (up to 20 nW/m3) are observed at the magnetopause boundary layer
The intense current filament is driven by an electron‐scale twisted magnetic structure
The energy conversion at the current filament is driven by the coaction between the twisted magnetic structure and the lower‐hybrid waves
Searches for a light sterile neutrino have been performed independently by the MINOS and the Daya Bay experiments using the muon (anti)neutrino and electron antineutrino disappearance channels, ...respectively. In this Letter, results from both experiments are combined with those from the Bugey-3 reactor neutrino experiment to constrain oscillations into light sterile neutrinos. The three experiments are sensitive to complementary regions of parameter space, enabling the combined analysis to probe regions allowed by the Liquid Scintillator Neutrino Detector (LSND) and MiniBooNE experiments in a minimally extended four-neutrino flavor framework. Stringent limits on sin^{2}2θ_{μe} are set over 6 orders of magnitude in the sterile mass-squared splitting Δm_{41}^{2}. The sterile-neutrino mixing phase space allowed by the LSND and MiniBooNE experiments is excluded for Δm_{41}^{2}<0.8 eV^{2} at 95% CL_{s}.
Abstract Aims To investigate the incidence of and factors associated with anastomotic leakage (AL) following gastrectomy for gastric cancer. Methods We retrospectively analyzed 3632 patients who ...underwent a laparoscopic gastrectomy or open gastrectomy for gastric cancer. A logistic regression model was used to identify the determinant variables, and a nomogram for AL was developed. Results A total of 3632 patients were included in the study, 50 of whom (1.4%) developed AL. Postoperative deaths occurred in 6(0.2%) patients with AL failure to rescue. Esophagojejunal AL (27/50) and Billroth I AL (20/50) were the most common types of AL. Gastrografin swallow was the main diagnostic method. The diagnosis was made a median of 9 days postoperatively. The median healing time for AL was 34.5 days. Of the 50 AL patients, 56% of patients could be managed nonsurgically, whereas 28% of patients required percutaneous radiologic drainage, 6% of patients were treated by endoscopy, and 10% of patients required a second surgery. A multivariate analysis showed the following adverse risk factors for AL: age≥65 years, hemoglobin ≤8.0g/dL and malnourishment. A multivariable model for AL showed a strong optimism-adjusted discrimination (concordance index, 0.675). The 5-year overall survival rates for patients without or with AL were 59.4% and 67.4%, respectively (p=0.354). Conclusions AL was infrequent but was more prevalent in patients with age ≥65 years, hemoglobin ≤8.0g/dL and malnourishment. We created a novel nomogram that can provide individualized prediction of AL in patients after a gastrectomy for gastric cancer, which may help clinicians in making treatment decisions.
PDF
