Subjects -> ASTRONOMY (Total: 94 journals)
Showing 1 - 46 of 46 Journals sorted alphabetically
Advances in Astronomy     Open Access   (Followers: 49)
Annual Review of Astronomy and Astrophysics     Full-text available via subscription   (Followers: 50)
Annual Review of Earth and Planetary Sciences     Full-text available via subscription   (Followers: 67)
Artificial Satellites     Open Access   (Followers: 21)
Astrobiology     Hybrid Journal   (Followers: 11)
Astronomical & Astrophysical Transactions: The Journal of the Eurasian Astronomical Society     Hybrid Journal   (Followers: 7)
Astronomical Review     Open Access   (Followers: 5)
Astronomische Nachrichten     Hybrid Journal   (Followers: 4)
Astronomy & Geophysics     Hybrid Journal   (Followers: 49)
Astronomy and Astrophysics     Full-text available via subscription   (Followers: 67)
Astronomy and Computing     Hybrid Journal   (Followers: 6)
Astronomy Letters     Hybrid Journal   (Followers: 22)
Astronomy Reports     Hybrid Journal   (Followers: 22)
Astronomy Studies Development     Open Access   (Followers: 15)
Astroparticle Physics     Hybrid Journal   (Followers: 10)
Astrophysical Bulletin     Hybrid Journal   (Followers: 4)
Astrophysics     Hybrid Journal   (Followers: 35)
Astrophysics and Space Science     Hybrid Journal   (Followers: 49)
Astrophysics and Space Sciences Transactions (ASTRA)     Open Access   (Followers: 60)
Astropolitics: The International Journal of Space Politics & Policy     Hybrid Journal   (Followers: 13)
Celestial Mechanics and Dynamical Astronomy     Hybrid Journal   (Followers: 15)
Chinese Astronomy and Astrophysics     Full-text available via subscription   (Followers: 25)
Colloid Journal     Hybrid Journal   (Followers: 2)
Comptes Rendus : Physique     Open Access   (Followers: 2)
Computational Astrophysics and Cosmology     Open Access   (Followers: 6)
Earth and Planetary Science Letters     Hybrid Journal   (Followers: 143)
Earth, Moon, and Planets     Hybrid Journal   (Followers: 47)
Earth, Planets and Space     Open Access   (Followers: 77)
EAS Publications Series     Full-text available via subscription   (Followers: 8)
EPL Europhysics Letters     Partially Free   (Followers: 8)
Experimental Astronomy     Hybrid Journal   (Followers: 38)
Expert Opinion on Astronomy and Astrophysics     Open Access   (Followers: 8)
Extreme Life, Biospeology & Astrobiology - International Journal of the Bioflux Society     Full-text available via subscription   (Followers: 4)
Few-Body Systems     Hybrid Journal   (Followers: 1)
Foundations of Physics     Hybrid Journal   (Followers: 40)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 15)
Galaxies     Open Access   (Followers: 6)
Globe, The     Full-text available via subscription   (Followers: 3)
Gravitation and Cosmology     Hybrid Journal   (Followers: 6)
Icarus     Hybrid Journal   (Followers: 71)
International Journal of Advanced Astronomy     Open Access   (Followers: 21)
International Journal of Astrobiology     Hybrid Journal   (Followers: 4)
International Journal of Astronomy     Open Access   (Followers: 22)
International Journal of Astronomy and Astrophysics     Open Access   (Followers: 36)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 15)
International Letters of Chemistry, Physics and Astronomy     Open Access   (Followers: 8)
ISRN Astronomy and Astrophysics     Open Access   (Followers: 14)
Journal for the History of Astronomy     Full-text available via subscription   (Followers: 20)
Journal of Astrobiology & Outreach     Open Access   (Followers: 5)
Journal of Astronomical Instrumentation     Open Access   (Followers: 3)
Journal of Astrophysics     Open Access   (Followers: 33)
Journal of Astrophysics and Astronomy     Open Access   (Followers: 58)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 133)
Journal of Geophysical Research : Planets     Full-text available via subscription   (Followers: 116)
Journal of Geophysical Research : Space Physics     Full-text available via subscription   (Followers: 136)
Journal of High Energy Astrophysics     Full-text available via subscription   (Followers: 25)
Kinematics and Physics of Celestial Bodies     Hybrid Journal   (Followers: 11)
KronoScope     Hybrid Journal   (Followers: 1)
Macalester Journal of Physics and Astronomy     Open Access   (Followers: 5)
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 13)
Monthly Notices of the Royal Astronomical Society : Letters     Hybrid Journal   (Followers: 2)
Nature Astronomy     Hybrid Journal   (Followers: 14)
New Astronomy     Hybrid Journal   (Followers: 26)
New Astronomy Reviews     Full-text available via subscription   (Followers: 19)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
NRIAG Journal of Astronomy and Geophysics     Open Access   (Followers: 4)
Physics of the Dark Universe     Open Access   (Followers: 4)
Planetary and Space Science     Hybrid Journal   (Followers: 106)
Planetary Science     Open Access   (Followers: 52)
Proceedings of the International Astronomical Union     Full-text available via subscription   (Followers: 2)
Publications of the Astronomical Society of Australia     Hybrid Journal   (Followers: 3)
Publications of the Astronomical Society of Japan     Hybrid Journal   (Followers: 4)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 20)
Research in Astronomy and Astrophysics     Full-text available via subscription   (Followers: 38)
Revista Mexicana de Astronomía y Astrofísica     Open Access   (Followers: 3)
Science China : Physics, Mechanics & Astronomy     Full-text available via subscription   (Followers: 4)
Science China Physics, Mechanics & Astronomy     Hybrid Journal   (Followers: 4)
Solar Physics     Hybrid Journal   (Followers: 29)
Solar System Research     Hybrid Journal   (Followers: 15)
Space Science International     Open Access   (Followers: 118)
Space Science Reviews     Hybrid Journal   (Followers: 92)
Space Weather     Full-text available via subscription   (Followers: 27)
Transport and Aerospace Engineering     Open Access   (Followers: 13)
Universe     Open Access   (Followers: 6)
Similar Journals
Journal Cover
Frontiers in Astronomy and Space Sciences
Number of Followers: 15  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2296-987X
Published by Frontiers Media Homepage  [96 journals]
  • Diagnosing Turbulent Magnetic Field in Supernova Remnants

    • Authors: Jiro Shimoda
      Abstract: We review recent investigations of the statistical nature of turbulent magnetic fields in supernova remnants. After a brief presentation of the role of the magnetic field in the cosmic-ray acceleration and synchrotron emissions from the accelerated electrons, we introduce previous investigations about the turbulent magnetic field in the supernova remnants. Then we describe the new method to analyze the statistical nature of the fields and introduce observational results reported on. Finally, we also discuss about the origin of the turbulent magnetic field and future prospects of observational studies of cosmic-ray acceleration in the supernova remnants.
      PubDate: 2022-05-23T00:00:00Z
       
  • Subarcsecond Imaging of a Solar Active Region Filament With ALMA and IRIS

    • Authors: J. M. da Silva Santos, S. M. White, K. Reardon, G. Cauzzi, S. Gunár, P. Heinzel, J. Leenaarts
      Abstract: Quiescent filaments appear as absorption features on the solar disk when observed in chromospheric lines and at continuum wavelengths in the millimeter (mm) range. Active region (AR) filaments are their small-scale, low-altitude analogues, but they could not be resolved in previous mm observations. This spectral diagnostic can provide insight into the details of the formation and physical properties of their fine threads, which are still not fully understood. Here, we shed light on the thermal structure of an AR filament using high-resolution brightness temperature (Tb) maps taken with ALMA Band 6 complemented by simultaneous IRIS near-UV spectra, Hinode/SOT photospheric magnetograms, and SDO/AIA extreme-UV images. Some of the dark threads visible in the AIA 304 Å passband and in the core of Mg ii resonance lines have dark (Tb 
      PubDate: 2022-05-23T00:00:00Z
       
  • Weathering of Chlorite Illite Deposits in the Hyperarid Qaidam Basin:
           Implications to Post-Depositional Alteration on Martian Clay Minerals

    • Authors: Yu Sun, Yiliang Li, Chaoqun Zhang, Xiaorong Qin, Jianxun Shen, Hongping He, Yongxin Pan
      Abstract: Chlorite is the second-most common class of clay minerals on the Martian surface and has been found to coexist with illite in some regions. Although previous studies have paid much attention to the formation of this assemblage, the post-depositional evolution cannot be neglected because the aqueous activities may alter the mineral assemblage and distribution. Here, we report on the post-depositional weathering of lacustrine-fluvial deposits collected from yardangs and dune-covering lake beds in the western Qaidam Basin, one of the largest and highest terrestrial Mars analogs. Mineralogical analysis shows that Fe-clinochlore and illite are the main clay components deposited as detrital particles. Electron microscopic observations of small rusty concretions from yardang deposits revealed that iron was released from clinochlore and formed ferrihydrite in fractures. We suggest that the activities of ephemeral waters after the deposition provide the major source of water that influences the migration of Fe in a long-lasting hyperarid climate. A similar iron-releasing mechanism could have occurred in Nili Fossae on Mars because multiple aqueous activities have shaped the terrains where chlorite illite deposits were identified by orbital near-infrared reflectance spectroscopy. Thus, reconstruction of the aqueous history of ancient Mars from surface minerals requires consideration of post-depositional processes, since groundwater/meteoric water may continuously interact with clay mineral-bearing deposits on Mars after their formation.
      PubDate: 2022-05-23T00:00:00Z
       
  • Classification of Cassini’s Orbit Regions as Magnetosphere,
           Magnetosheath, and Solar Wind via Machine Learning

    • Authors: Kiley L. Yeakel, Jon D. Vandegriff, Tadhg M. Garton, Caitriona M. Jackman, George Clark, Sarah K. Vines, Andrew W. Smith, Peter Kollmann
      Abstract: Several machine learning algorithms and feature subsets from a variety of particle and magnetic field instruments on-board the Cassini spacecraft were explored for their utility in classifying orbit segments as magnetosphere, magnetosheath or solar wind. Using a list of manually detected magnetopause and bow shock crossings from mission scientists, random forest (RF), support vector machine (SVM), logistic regression (LR) and recurrent neural network long short-term memory (RNN LSTM) classification algorithms were trained and tested. A detailed error analysis revealed a RNN LSTM model provided the best overall performance with a 93.1% accuracy on the unseen test set and MCC score of 0.88 when utilizing 60 min of magnetometer data ( B , Bθ, Bϕ and BR) to predict the region at the final time step. RF models using a combination of magnetometer and particle data, spanning H+, He+, He++ and electrons at a single time step, provided a nearly equivalent performance with a test set accuracy of 91.4% and MCC score of 0.84. Derived boundary crossings from each model’s region predictions revealed that the RNN model was able to successfully detect 82.1% of labeled magnetopause crossings and 91.2% of labeled bow shock crossings, while the RF model using magnetometer and particle data detected 82.4 and 74.3%, respectively.
      PubDate: 2022-05-20T00:00:00Z
       
  • Imaging Low-Energy Ion Outflow in the Auroral Zone

    • Authors: Douglas Rowland, Michael Collier, John Keller, Robert Pfaff, Jeffrey Klenzing, Jason McLain, James Clemmons, James Hecht
      Abstract: The VISualizing Ion Outflow via Neutral atom imaging during a Substorm (VISIONS) sounding rocket mission investigated the factors leading to ion outflow following a geomagnetic substorm. In situ and remote sensing instrumentation provided complementary measurements that have been combined to yield an in-depth look at the phenomena associated with ion outflow. In particular, the inclusion of instrumentation that provided high spatial and temporal resolution “images” of low-energy neutral atom (ENA) emissions from the nightside auroral zone following a substorm has led to new insights. The observed ENAs were spatially structured, and strongly associated with regions of intense 630.0 nm auroral emissions. The ENAs in the auroral zone were predominantly up-going, consistent with thick-target scattering in the region where the ENA mean free path is close to or less than the atmospheric scale height.
      PubDate: 2022-05-19T00:00:00Z
       
  • The Martian Crustal Magnetic Field

    • Authors: Anna Mittelholz, Catherine L. Johnson
      Abstract: Mars’ crustal magnetic field holds information on the planet’s interior evolution and exterior processes that have modified the crust. Crustal magnetization records an ancient dynamo field that indicates very different interior conditions in the past, possibly linked to the presence of a thicker early atmosphere. Current data sets have provided a wealth of information on the ancient magnetic field, and on the acquisition and modification of magnetization in the crust. However, many puzzles remain regarding the nature and origin of crustal magnetization, and the timing and characteristics of the past dynamo. Here we use recent advances in understanding martian magnetism to highlight open questions, and ways in which they can be addressed through laboratory analysis, modeling and new data sets. Many of the outstanding key issues require data sets that close the gap in spatial resolution between available global satellite and local surface magnetic field measurements. Future missions such as a helicopter, balloon or airplane can provide areal high resolution coverage of the magnetic field, vital to major advances in understanding planetary crustal magnetic fields.
      PubDate: 2022-05-19T00:00:00Z
       
  • Estimating Inner Magnetospheric Radial Diffusion Using a Hybrid-Vlasov
           Simulation

    • Authors: H. George, A. Osmane, E. K. J. Kilpua, S. Lejosne , L. Turc, M. Grandin, M. M. H. Kalliokoski, S. Hoilijoki, U. Ganse, M. Alho, M. Battarbee, M. Bussov, M. Dubart, A. Johlander, T. Manglayev, K. Papadakis, Y. Pfau-Kempf, J. Suni, V. Tarvus, H. Zhou, M. Palmroth
      Abstract: Radial diffusion coefficients quantify non-adiabatic transport of energetic particles by electromagnetic field fluctuations in planetary radiation belts. Theoretically, radial diffusion occurs for an ensemble of particles that experience irreversible violation of their third adiabatic invariant, which is equivalent to a change in their Roederer L* parameter. Thus, the Roederer L* coordinate is the fundamental quantity from which radial diffusion coefficients can be computed. In this study, we present a methodology to calculate the Lagrangian derivative of L* from global magnetospheric simulations, and test it with an application to Vlasiator, a hybrid-Vlasov model of near-Earth space. We use a Hamiltonian formalism for particles confined to closed drift shells with conserved first and second adiabatic invariants to compute changes in the guiding center drift paths due to electric and magnetic field fluctuations. We investigate the feasibility of this methodology by computing the time derivative of L* for an equatorial ultrarelativistic electron population travelling along four guiding center drift paths in the outer radiation belt during a 5 minute portion of a Vlasiator simulation. Radial diffusion in this simulation is primarily driven by ultralow frequency waves in the Pc3 range (10–45 s period range) that are generated in the foreshock and transmitted through the magnetopause to the outer radiation belt environment. Our results show that an alternative methodology to compute detailed radial diffusion transport is now available and could form the basis for comparison studies between numerical and observational measurements of radial transport in the Earth’s radiation belts.
      PubDate: 2022-05-18T00:00:00Z
       
  • Linear Theory of Electromagnetic Ion Beam Instabilities in the Earth’s
           Forshock: Peter Gary’s Contributions (1981–1991)

    • Authors: Dan Winske, Lynn B. Wilson
      Abstract: We discuss Peter Gary’s contributions to the understanding of the origin and properties of ultra-low frequency (ULF) waves in the Earth’s foreshock during the period when the International Sun Earth Explorer spacecraft (ISEE-1 and -2) provided unique data about the plasma and wave environment in this region. Peter’s work concerning the linear theory of electromagnetic ion beam instabilities is contained in five journal articles and then summarized in a review article, all of which are discussed here. Brief summaries of observations and theory prior to ISEE as well as to later work are also included.
      PubDate: 2022-05-16T00:00:00Z
       
  • The Planetary Nebula Luminosity Function in the Era of Precision Cosmology

    • Authors: Robin Ciardullo
      Abstract: One of the great surprises of the late 1980s was the discovery that the [O III] λ5007 planetary nebula luminosity function (PNLF) could be used as a precision extragalactic standard candle. Despite the lack of any robust theory for the phenomenon, the technique passed a myriad of internal and external tests, and became an extremely reliable tool for obtaining distances to large galaxies within ∼20 Mpc. But in more recent years, the use of the technique has declined, due in part to the changing landscape of cosmology. Here we review the history of the PNLF, the experiments that confirmed its utility, and the reasons why interest in the method faded at the turn of the millennium. We also describe how and why the PNLF is making a comeback, and present some of the method’s recent results. Finally, we discuss how the PNLF must be analyzed in the era of precision cosmology, and detail the issues that must be overcome in order to address the current tension between local measures of the Hubble constant and values derived from the microwave background. If these issues can be understood, then the PNLF can provide a useful cross-check on distance measurements out to ∼40 Mpc.
      PubDate: 2022-05-16T00:00:00Z
       
  • Editorial: Micro- to Macro-Scale Dynamics of Earth’s Flank
           Magnetopause

    • Authors: Kyoung-Joo Hwang, Hiroshi Hasegawa, Katariina Nykyri, Takuma Nakamura, Simon Wing
      PubDate: 2022-05-13T00:00:00Z
       
  • Formamide-Based Post-impact Thermal Prebiotic Synthesis in Simulated
           Craters: Intermediates, Products and Mechanism

    • Authors: Martin Ferus, Antonín Knížek, Lukáš Petera, Adam Pastorek, Jana Hrnčířová, Luboš Jankovič, Ondřej Ivanek, Jiří Šponer, Anna Křivková, Homa Saeidfirozeh, Svatopluk Civiš, Elias Chatzitheodoridis, Klaudia Mráziková, Lukáš Nejdl, Franz Saija, Judit E. Šponer, Giuseppe Cassone
      Abstract: Influx of matter from impacting meteoroids and hydrothermal crater weathering are important factors modifying the rock and mineral inventory of young planets undergoing heavy bombardment. These processes may have influenced not only the geochemical environment of, e.g., early Mars and other planets, but also the peculiar prebiotic chemistry on early Earth. Here, we present a synergistic experimental and computational investigation of the intermediates of chemical reactions of the formamide-based synthesis of canonical and non-canonical nucleobases by thermochemistry in hot hydrothermal crater environments. We put our findings into context with previously investigated plasma-initiated synthesis occuring directly during impact. Both processes result into the formation of all canonical nucleobases, hypoxanthine, purine, and into the onset of the simplest amino acid glycine. Furthermore, it turns out that radical species such as CN and H play a key role in the plasma-assisted impact chemistry. However, post-impact thermochemistry is essential for the origin of formamidine and 2-aminoacetonitrile, intermediate species detected in this study by means of FTIR spectroscopy.
      PubDate: 2022-05-13T00:00:00Z
       
  • From Coronal Holes to Pulsars and Back Again: Learning the Importance of
           Data

    • Authors: Y.-M. Wang
      Abstract: Although wanting to become an astronomer from an early age, I ended up in solar physics purely by chance, after first working in high-energy astrophysics. I’ve never regretted switching from the pulsar to the solar magnetosphere, because solar physics has a great advantage over other areas of astrophysics—in the enormous amount of high-quality data available, much of it underutilized. I’ve often wondered why theoreticians and modelers don’t spent more time looking at these data (perhaps they feel that it is cheating, like taking a peek at the answers to a difficult homework assignment'). Conversely, I wonder why observers and data analysts aren’t more skeptical of the theoretical models—especially the fashionable ones.
      PubDate: 2022-05-12T00:00:00Z
       
  • Multiple E-Region Radar Propagation Modes Measured by the VHF SIMONe
           Norway System During Active Ionospheric Conditions

    • Authors: Devin Huyghebaert, Matthias Clahsen, Jorge L. Chau, Toralf Renkwitz, Ralph Latteck, Magnar G. Johnsen, Juha Vierinen
      Abstract: Multiple propagation modes between different bistatic radar links were measured during the operations of a very high frequency (VHF) 32.55 MHz radar system in northern Norway. The Spread Spectrum Interferometric Multistatic meteor radar Observing Network (SIMONe) Norway system detected meteor trails, direct transmitter to receiver signal propagation, over-the-horizon signal propagation from the SIMONe Germany system, ground and/or sea scatter, and ionospheric scatter on 27 August 2021 between 16:30–20:00 UT. These simultaneous detections were during an active ionospheric period with multiple occurrences of energetic charged particle precipitation. The SIMONe systems used continuous-wave (CW) pseudo-random phase modulated transmit signals and interferometry to make it possible to isolate each of these propagation modes and examine their characteristics. Different multistatic links at three receiver locations were analyzed, providing multistatic measurements of the regions with spatial and temporal resolutions on the order of 1.5 km and 2 s. The analysis techniques are described, with characteristics of the radar signal presented for each propagation mode and multistatic link. This study serves to highlight the capabilities of the SIMONe Norway system to research multiple aspects of ionospheric phenomena, specifically in the lower thermosphere-mesosphere boundary region.
      PubDate: 2022-05-10T00:00:00Z
       
  • Domain-Agnostic Outlier Ranking Algorithms—A Configurable Pipeline for
           Facilitating Outlier Detection in Scientific Datasets

    • Authors: Hannah R. Kerner, Umaa Rebbapragada, Kiri L. Wagstaff, Steven Lu, Bryce Dubayah, Eric Huff, Jake Lee, Vinay Raman, Sakshum Kulshrestha
      Abstract: Automatic detection of outliers is universally needed when working with scientific datasets, e.g., for cleaning datasets or flagging novel samples to guide instrument acquisition or scientific analysis. We present Domain-agnostic Outlier Ranking Algorithms (DORA), a configurable pipeline that facilitates application and evaluation of outlier detection methods in a variety of domains. DORA allows users to configure experiments by specifying the location of their dataset(s), the input data type, feature extraction methods, and which algorithms should be applied. DORA supports image, raster, time series, or feature vector input data types and outlier detection methods that include Isolation Forest, DEMUD, PCA, RX detector, Local RX, negative sampling, and probabilistic autoencoder. Each algorithm assigns an outlier score to each data sample. DORA provides results interpretation modules to help users process the results, including sorting samples by outlier score, evaluating the fraction of known outliers in n selections, clustering groups of similar outliers together, and web visualization. We demonstrated how DORA facilitates application, evaluation, and interpretation of outlier detection methods by performing experiments for three real-world datasets from Earth science, planetary science, and astrophysics, as well as one benchmark dataset (MNIST/Fashion-MNIST). We found that no single algorithm performed best across all datasets, underscoring the need for a tool that enables comparison of multiple algorithms.
      PubDate: 2022-05-10T00:00:00Z
       
  • Exploitation of the IPHAS to Investigate Planetary Nebulae

    • Authors: Laurence Sabin, Jesús A. Toalá, Gerardo Ramos-Larios, Martín A.  Guerrero
      Abstract: Similar to other classes of astronomical objects, there is a large discrepancy between the total count of theoretically predicted planetary nebulae (PNe) and the number of those actually observed. This discrepancy introduces bias in our attempt to globally understand and characterize the PNe population. Major efforts have been made to find the missing PNe. In particular, the INT Photometric Hα Survey (IPHAS) has, since its debut, provided a whelm of new (candidate) PNe, some of which have been studied in depth using various methodologies such as deep imaging and low- and high-resolution spectroscopy. Here, we present the outcome of the analysis of a first group of these well-investigated IPHAS PNe with a focus on the extended ones. We show that, in general, the missing objects that were expected to be unveiled by the survey (low density, evolved, and distant) are indeed discovered, but the survey also allows the retrieval of “simply” overlooked PNe.
      PubDate: 2022-05-10T00:00:00Z
       
  • Deciphering Solar Magnetic Activity: The Solar Cycle Clock

    • Authors: Robert J. Leamon, Scott W. McIntosh, Alan M. Title
      Abstract: The Sun’s variability is controlled by the progression and interaction of the magnetized systems that form the 22-year magnetic activity cycle (the “Hale Cycle”) as they march from their origin at ∼55° latitude to the equator, over ∼19 years. We will discuss the end point of that progression, dubbed “terminator” events, and our means of diagnosing them. In this paper we expand on the Extended Solar Cycle framework to construct a new solar activity “clock” which maps all solar magnetic activity onto a single normalized epoch based on the terminations of Hale Magnetic Cycles. Defining phase 0*2π on this clock as the Terminators, then solar polar field reversals occur at ∼ 0.2*2π, and the geomagnetically quiet intervals centered around solar minimum start at ∼ 0.6*2π and end at the terminator, thus lasting 40% of the cycle length. At this onset of quiescence, dubbed a “pre-terminator,” the Sun shows a radical reduction in active region complexity and, like the terminator events, is associated with the time when the solar radio flux crosses F10.7 = 90 sfu. We use the terminator-based clock to illustrate a range of phenomena that further emphasize the strong interaction of the global-scale magnetic systems of the Hale Cycle: the vast majority, 96%, of all X-flares happen between the Terminator and pre-Terminator. In addition to the X-rays from violent flares, rapid changes in the number of energetic photons—EUV spectral emission from a hot corona and the F10.7 solar radio flux—impinging on the atmosphere are predictable from the Terminator-normalized unit cycle, which has implications for improving the fidelity of atmospheric modelling.
      PubDate: 2022-05-10T00:00:00Z
       
  • Jovian Planets and Lunar Nodal Cycles in the Earth’s Climate
           Variability

    • Authors: Harald Yndestad
      Abstract: This study utilizes time-series data devised to measure solar irradiation, sea surface temperatures, and temperatures in the lower atmosphere to gain a better understanding of how gravitational effects from the moon and Jovian planets (Jupiter, Saturn, Uranus, and Neptune) influence solar activity and climatic conditions on Earth. Then, standard statistical methods are used to determine the degree of correlation among these time series and construct a Jovian gravitational model. The study reveals a direct relationship between JSUN perihelion coincidences and TSI amplitude variations in cycles up to 4,450 years. The forced solar accumulation of heat in oceans introduces a new phase relation between solar forced cycles and new climate variation. Earth’s axis nutation cycles have coincidences with lunar nodal tide cycles and lunar forced sea surface temperature cycle periods up to 446 years. Earth’s temperature variation shows coincidence with constructive and destructive interference between lunar-forced and accumulated solar-forced temperature variations in oceans. Upcoming events have a computed modern temperature maximum in 2025 and a deep minimum in 2070. Interference between solar-forced temperature cycles of 333,2142, and 4,450 years and a lunar-forced temperature cycle of 445 years indicates that “The Little Ice Age” covers a total period of 820 years from 1330 to 2150 A.D. and an upcoming temporary cold climate period from 2070 to 2150.
      PubDate: 2022-05-10T00:00:00Z
       
  • Planetary Nebulae as Sources of Chemical Enrichment of the Galaxy

    • Authors: Sun Kwok
      Abstract: During the late asymptotic giant branch (AGB) phase of stellar evolution, the element carbon is created through the triple-α nuclear reaction. This is followed by the synthesis of other heavy elements via neutron capture in the core and the dredge-up of these elements to the surface by convection. Simple molecules and solid-state minerals begin to form in the upper photosphere. These molecules and solids are ejected into the interstellar medium by a strong stellar wind. During the subsequent post-AGB evolution, complex organics with aromatic and aliphatic structures are synthesized in the circumstellar envelope. Planetary nebulae, formed by swept-up circumstellar material, are found to show strong spectral signatures of ions, atoms, molecules, and inorganic and organic solids. These ejected materials of planetary nebulae serve as primordial ingredients of formation of new stars and planetary systems. Stellar synthesized organic solids may survive their journeys through the interstellar medium and evidence for remnants of such organics can be found in our own Solar System. In this paper, we summarize the recent observations of circumstellar synthesis of molecules and solids and discuss the implications of these ejected circumstellar materials on the chemical enrichment of the Galaxy and planetary systems.
      PubDate: 2022-05-10T00:00:00Z
       
  • A New Three-Dimensional Empirical Reconstruction Model Using a Stochastic
           Optimization Method

    • Authors: Xun Zhu, Ian J. Cohen, Barry H. Mauk, Romina Nikoukar, Drew L. Turner, Roy B. Torbert
      Abstract: Motivated by MMS mission observations near magnetic reconnection sites, we have developed a new empirical reconstruction (ER) model of the three-dimensional (3D) magnetic field and the associated plasma currents. Our approach combines both the measurements from a constellation of satellites and a set of physics-based equations as physical constraints to build spatially smooth distributions. This ER model directly minimizes the loss function that characterizes the model-measurement differences and the model departures from linear or nonlinear physical constraints using an efficient stochastic optimization method by which the effects of random measurement errors can be effectively included. Depending on the availability of the measured parameters and the adopted physical constraints on the reconstructed fields, the ER model could be either slightly over-determined or under-determined, yielding nearly identical reconstructed fields when solved by the stochastic optimization method. As a result, the ER model remains valid and operational even if the input measurements are incomplete. Two sets of new indices associated respectively with the model-measurement differences and the model departures are introduced to objectively measure the accuracy and quality of the reconstructed fields. While applying the reconstruction model to observations of an electron diffusion region (EDR) observed by NASA’s Magnetospheric Multiscale (MMS) mission, we examine the relative contributions of the errors in the plasma current density arising from random measurement errors and linear approximations made in application of the curlometer technique. It was found that the errors in the plasma current density calculated directly from the measured magnetic fields using a linear approximation were mostly contributed from the nonlinear configuration of the 3D magnetic fields.
      PubDate: 2022-05-09T00:00:00Z
       
  • Ray Tracing of MHD Rossby Waves in the Solar Tachocline: Meridional
           Propagation and Implications for the Solar Magnetic Activity

    • Authors: André S. W. Teruya, Breno Raphaldini, Carlos F. M. Raupp
      Abstract: Rossby waves have been recently recognised for their role in the large-scale spatio-temporal organisation of the solar magnetic activity. Here, we study the propagation of magnetohydrodynamic Rossby waves in a thin layer, representing the solar tachocline. We consider the waves embedded in a meridionally varying background state characterised by a mean zonal flow, which mimics the differential rotation profile of the Sun, and a toroidal magnetic field. Two anti-symmetric toroidal magnetic fields are utilised: one having a global structure with the maximum at around 50o and the other characterised by a narrow band centered at around 20o. We show that for a global structure toroidal magnetic field, the MHD Rossby modes undergo significant meridional propagation, either equatorward or poleward. In addition, the latitude where the waves exhibit a stationary behaviour is sensitive to the strength of the background magnetic field. On the other hand, a narrow band toroidal magnetic field is shown to work as a waveguide for the fast branch of MHD Rossby waves.
      PubDate: 2022-05-05T00:00:00Z
       
 
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