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Universe ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 39
Author(s):  
Rositsa Miteva ◽  
Susan W. Samwel

A comprehensive statistical analysis on the properties and accompanied phenomena of all M-class solar flares (as measured in soft X-rays) in the last two solar cycles (1996–2019) is presented here with a focus on their space weather potential. The information about the parent active region and the underlying sunspot (Hale) type is collected for each case, where possible, in order to identify photospheric precondition as precursors for the solar flare eruption or confinement. Associations with coronal mass ejections, solar energetic particles, and interplanetary radio emissions are also evaluated and discussed as possible proxies for flare eruption and subsequent space weather relevance. The results show that the majority (∼80%) of the analyzed M-class flares are of β, β-γ, and β-γ-δ magnetic field configuration. The M-class population of flares is accompanied by CMEs in 41% of the cases and about half of the flare sample has been associated with radio emission from electron beams. A much lower association (≲10%) is obtained with shock wave radio signatures and energetic particles. Furthermore, a parametric scheme is proposed in terms of occurrence rates between M-class flares and a variety of accompanied solar phenomena as a function of flare sub-classes or magnetic type. This study confirms the well-known reduced but inevitable space weather importance of M-class flares.


Author(s):  
Lisa Buschmann ◽  
Ashild Fredriksen

Abstract The information about the electron population of a helicon source plasma that expands along a magnetic nozzle is important for understanding the plasma acceleration across the potential drop that forms in the nozzle. The electrons need an energy higher than the potential drop to escape from the source. At these energies the signal of a Langmuir probe is less accurate. An inverted RFEA measures the high-energy tail of the electrons. To reach the probe, they must have energies above the plasma potential VP, which can vary over the region of the measurement. By constructing a full distribution by applying the electron temperature Te obtained from the electron IV-curve and the VP obtained from the ion collecting RFEA or an emissive probe, a density measure of the hot electron distribution independent of VP can be obtained. The variation of the high-energy tail of the EEDF in both radial and axial directions, in the two different cases of 1) a purely expanding magnetic field nozzle, and 2) a more constricted one by applying current in a third, downstream coil was investigated. The electron densities and temperatures from the source are then compared to two analytic models of the downstream development of the electron density. The first model considers the development for a pure Boltzmann distribution while the second model takes an additional magnetic field expansion into account. A good match between the measured densities and the second model was found for both configurations. The RFEA probe also allows for directional measurement of the electron current to the probe. This property is used to compare the densities from the downstream and upstream directions, showing a much lower contribution of downstream electrons into the source for a purely expanding magnetic field in comparison to the confined magnetic field configuration.


2022 ◽  
Vol 21 (12) ◽  
pp. 318
Author(s):  
Syed Ibrahim ◽  
Wahab Uddin ◽  
Bhuwan Joshi ◽  
Ramesh Chandra ◽  
Arun Kumar Awasthi

Abstract In this article, we compare the properties of two coronal mass ejections (CMEs) that show similar source region characteristics but different evolutionary behaviors in the later phases. We discuss the two events in terms of their near-Sun characteristics, interplanetary evolution and geoeffectiveness. We carefully analyzed the initiation and propagation parameters of these events to establish the precise CME-interplanetary CME (ICME) connection and their near-Earth consequences. The first event is associated with poor geomagnetic storm disturbance index (Dst ≈-20 nT) while the second event is associated with an intense geomagnetic storm of DST ≈-119 nT. The configuration of the sunspots in the active regions and their evolution are observed by Helioseismic and Magnetic Imager (HMI). For source region imaging, we rely on data obtained from Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory (SDO) and Hα filtergrams from the Solar Tower Telescope at Aryabhatta Research Institute of Observational Sciences (ARIES). For both the CMEs, flux rope eruptions from the source region triggered flares of similar intensities (≈M1). At the solar source region of the eruptions,we observed a circular ribbon flare (CRF) for both cases, suggesting fan-spine magnetic configuration in the active region corona. The multi-channel SDO observations confirm that the eruptive flares and subsequent CMEs were intimately related to the filament eruption. Within the Large Angle and Spectrometric Coronograph (LASCO) field of view (FOV) thetwo CMEs propagated with linear speeds of 671 and 631 km s−1, respectively. These CMEs were tracked up to the Earth by Solar Terrestrial Relations Observatory (STEREO) instruments. We find that the source region evolution of CMEs, guided by the large-scale coronal magnetic field configuration, along with near-Sun propagation characteristics, such as CME-CME interactions, played important roles in deciding the evolution of CMEs in the interplanetary medium and subsequently their geoeffectiveness.


2021 ◽  
Author(s):  
Mauro Corti ◽  
Marco Montini ◽  
Giorgio Gioja

Abstract In the Oil & Gas sector, the production optimization is one of the most challenging problem, since it involves many operational variables linked by complex relationships. Moreover, during the asset life cycle those parameters could change. Conflicts and interactions between variables, constraints, and operational limitations could be solved holistically by an optimization tool based on an Evolutionary Algorithm. The algorithm searches for the optimum field configuration from the operational point of view, leading to the production maximization. Eni Production Department developed a tool based on this algorithm for management and optimization of surface asset hardly focused on field viewpoint. e-Rabbit (Risked Algorithm for Biogenetical Balance Integration Tool) provides integration for reservoir, well, network and process models. The present work has been developed to overcome a recurrent problem in the Oil & Gas business: the lack of data. There are many cases in which this situation occurs, for example in old fields where measurement tools and digitalization are not so widespread or in assets characterized by many wells and complex gathering systems, in which the detail on well performances could not be available. e-Rabbit, to perform its optimization, requires that information so, under those conditions, somehow, it is necessary to find another way to be able to optimize and manage the surface asset. A novel technique to optimize the whole production system has been introduced, whose objective function rely on backpressure minimization. To verify its effectiveness two case studies have been analyzed comparing the proposed optimal configuration with the output of the classical e-Rabbit - optimization.


2021 ◽  
Vol 923 (1) ◽  
pp. 72
Author(s):  
Sudheer K. Mishra ◽  
Balveer Singh ◽  
A. K. Srivastava ◽  
Pradeep Kayshap ◽  
B. N. Dwivedi

Abstract We use multiwavelength imaging observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory to study the evolution of the Kelvin–Helmholtz (K–H) instability in a fan-spine magnetic field configuration. This magnetic topology exists near an active region AR12297 and is rooted in a nearby sunspot. In this magnetic configuration, two layers of cool plasma flow in parallel and interact with each other inside an elongated spine. The slower plasma flow (5 km s−1) is the reflected stream along the spine’s field lines from the top, which interacts with the impulsive plasma upflows (114–144 km s−1) from below. This process generates a shear motion and subsequent evolution of the K–H instability. The amplitude and characteristic wavelength of the K–H unstable vortices increase, satisfying the criterion of the fastest-growing mode of this instability. We also describe how the velocity difference between two layers and the velocity of K–H unstable vortices are greater than the Alfvén speed in the second denser layer, which also satisfies the criterion of the growth of the K–H instability. In the presence of the magnetic field and sheared counterstreaming plasma as observed in the fan-spine topology, we estimate the parametric constant Λ ≥ 1, which confirms the dominance of velocity shear and the evolution of the linear phase of the K–H instability. This observation indicates that in the presence of complex magnetic field structuring and flows, the fan-spine configuration may evolve into rapid heating, while the connectivity changes due to the fragmentation via the K–H instability.


2021 ◽  
Vol 6 (4) ◽  
pp. 47
Author(s):  
Marco Miliucci ◽  
Massimiliano Bazzi ◽  
Damir Bosnar ◽  
Mario Bragadireanu ◽  
Marco Carminati ◽  
...  

A large-area silicon drift detectors (SDDs) system has been developed by the SIDDHARTA-2 collaboration for high precision light kaonic atom X-ray spectroscopy at the DAΦNE collider of Istituto Nazionale di Fisica Nucleare—Laboratori Nazionali di Frascati. The SDDs’ geometry and electric field configuration, combined with their read-out electronics, make these devices suitable for performing high precision light kaonic atom spectroscopy measurements in the background of the DAΦNE collider. This work presents the spectroscopic response of the SDDs system during the first exotic atoms run of SIDDHARTA-2 with kaonic helium, a preliminary to the kaonic deuterium data taking campaign. The SIDDHARTA-2 spectroscopic system has good energy resolution and a 2 μs timing window which rejects the asynchronous events, scaling the background by a factor of 10−5. The results obtained for the first exotic atoms run of SIDDHARTA-2 prove this system to be ready to perform the challenging kaonic deuterium measurement.


2021 ◽  
Vol 127 (22) ◽  
Author(s):  
Felix Warmer ◽  
K. Tanaka ◽  
P. Xanthopoulos ◽  
M. Nunami ◽  
M. Nakata ◽  
...  

2021 ◽  
Vol 2081 (1) ◽  
pp. 012007
Author(s):  
A N Petrov

Abstract The field-theoretical methods are used to construct conserved currents and related superpotentials for perturbations on arbitrary backgrounds in the Lovelock gravity. The perturbations are considered as a dynamic field configuration propagating in a given spacetime. The field-theoretical formalism is exact (without approximations) and equivalent to the original metric theory. As Lagrangian based formalism, it allows us to apply the Noether theorem. As a result, we construct conserved currents and superpotentials, where we use arbitrary displacement vectors, not only the Killing ones or other special vectors. The developed formalism is checked in calculating mass of the Schwarzschild-anti-de Sitter (AdS) black hole. The new formalism is adopted to the case of a so-called pure Lovelock gravity, where in the Lagrangian only a one polynomial in Riemannian tensor presents. We construct conserved charges and currents for static and dynamic black holes of the Vaidya type with AdS, dS and flat asymptotics. New properties of the solutions under consideration have been found. The more results are discussed. The first section in your paper


2021 ◽  
Vol 2064 (1) ◽  
pp. 012061
Author(s):  
A V Kaziev ◽  
D G Ageychenkov ◽  
A V Tumarkin ◽  
D V Kolodko ◽  
N S Sergeev ◽  
...  

Abstract The response of the ion current in the substrate region to the magnetic system configuration of a circular magnetron was studied during direct current sputtering of aluminum target. The unbalancing degree induced by changing of magnets’ positions was modelled with finite element methods. The ion saturation current in the substrate region showed more than twofold variation with unbalancing degree in the range 0.6–1.2. The dependence was non-monotonic, and the system was optimized to maximize the substrate ion current. The Langmuir probe diagnostics showed plasma density ~ 1016 m−3 in the optimized magnetic configuration.


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