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  • Ring of Stations Method in Cosmic Rays Variations Research
    Sol. Phys. (IF 2.405) Pub Date : 2020-05-29
    M. A. Abunina, A. V. Belov, E. A. Eroshenko, A. A. Abunin, V. G. Yanke, A. A. Melkumyan, N. S. Shlyk, I. I. Pryamushkina

    For over 60 years, neutron monitors have been the main standard and high precision detectors for measuring cosmic rays with energy from 400 MeV to hundreds GeV. In order to obtain sufficiently complete information about the distribution of cosmic rays outside the magnetosphere, it is necessary to have a network of detectors spaced evenly enough around the globe. The ring of stations method is one of

  • Modeling the Time Delay Problem of Galactic Cosmic Ray Flux in Solar Cycles 21 and 23
    Sol. Phys. (IF 2.405) Pub Date : 2020-05-25
    M. Siluszyk, K. Iskra

    We present a 2-dimensional time-dependent simulation based on Parker’s transport equation (PTE) describing the propagation of energetic astroparticles – cosmic rays (CR) in the heliosphere. PTE is a second order partial differential equation containing four major processes: diffusion, convection, drift, and adiabatic cooling responsible for modulation of the CR flux in the heliosphere. We implement

  • The Hidden Cycle of the Solar Tesseral-Quadrupole Magnetic Field
    Sol. Phys. (IF 2.405) Pub Date : 2020-05-22
    V. P. Mikhaylutsa

    Based on the Stanford harmonic coefficients of the solar magnetic fields and on the results of Shannon entropy transfer technique applied to magnetic mode intensities (Mikhaylutsa in J. Astrophys. Astron.40, 22, 2019), we have found that most of the medium and small-scale solar magnetic modes (order \(l > 3\); degree \(m > 0\)) must be interdependent. The features and physical sense of these dependencies

  • Long-Term Evolution of the Solar Corona Using PROBA2 Data
    Sol. Phys. (IF 2.405) Pub Date : 2020-05-20
    Marilena Mierla, Jan Janssens, Elke D’Huys, Laurence Wauters, Matthew J. West, Daniel B. Seaton, David Berghmans, Elena Podladchikova

    We use The Sun Watcher with Active Pixel System detector and Image Processing (SWAP) imager onboard the Project for Onboard Autonomy 2 (PROBA2) mission to study the evolution of large-scale EUV structures in the solar corona observed throughout Solar Cycle 24 (from 2010 to 2019). We discuss the evolution of the on-disk coronal features and at different heights above the solar surface based on EUV intensity

  • Magnetic Flux Emergence in a Coronal Hole
    Sol. Phys. (IF 2.405) Pub Date : 2020-05-19
    Judith Palacios, Dominik Utz, Stefan Hofmeister, Kilian Krikova, Peter Gömöry, Christoph Kuckein, Carsten Denker, Meetu Verma, Sergio Javier González Manrique, Jose Iván Campos Rozo, Július Koza, Manuela Temmer, Astrid Veronig, Andrea Diercke, Ioannis Kontogiannis, Consuelo Cid

    A joint campaign of various space-borne and ground-based observatories, comprising the Japanese Hinode mission (Hinode Observing Plan 338, 20 – 30 September 2017), the GREGOR solar telescope, and the Vacuum Tower Telescope (VTT), investigated numerous targets such as pores, sunspots, and coronal holes. In this study, we focus on the coronal hole region target. On 24 September 2017, a very extended

  • Forecasting Solar Cycle 25 Using Deep Neural Networks
    Sol. Phys. (IF 2.405) Pub Date : 2020-05-19
    B. Benson, W. D. Pan, A. Prasad, G. A. Gary, Q. Hu

    With recent advances in the field of machine learning, the use of deep neural networks for time series forecasting has become more prevalent. The quasi-periodic nature of the solar cycle makes it a good candidate for applying time series forecasting methods. We employ a combination of WaveNet and Long Short-Term Memory neural networks to forecast the sunspot number using the years 1749 to 2019 and

  • Simulating White-Light Images of Coronal Structures for Parker Solar Probe/WISPR: Study of the Total Brightness Profiles
    Sol. Phys. (IF 2.405) Pub Date : 2020-04-29
    Giuseppe Nisticò, Volker Bothmer, Angelos Vourlidas, Paulett C. Liewer, Arnaud F. Thernisien, Guillermo Stenborg, Russell A. Howard

    The Wide-field Imager for Parker Solar Probe (WISPR) captures unprecedented white-light images of the solar corona and inner heliosphere. Thanks to the uniqueness of the Parker Solar Probe’s (PSP) orbit, WISPR is able to image “locally” coronal structures at high spatial and time resolutions. The observed plane of sky, however, rapidly changes because of the PSP’s high orbital speed. Therefore, the

  • Relationships between Interplanetary Coronal Mass Ejection Characteristics and Geoeffectiveness in the Declining Phase of Solar Cycles 23 and 24
    Sol. Phys. (IF 2.405) Pub Date : 2020-04-24
    M. Bendict Lawrance, Y.-J. Moon, A. Shanmugaraju

    In this paper, we have examined the relationships between the characteristics of interplanetary coronal mass ejections (ICMEs) and geoeffectiveness in the declining phase of Solar Cycles 23 and 24. We discuss the results in comparison with those of the rising phase. Major results of this study are as follows: The ICMEs in the declining phase of Cycle 23 have generated higher storm strength than those

  • ICME Evolution in the Inner Heliosphere
    Sol. Phys. (IF 2.405) Pub Date : 2020-04-23
    J. G. Luhmann, N. Gopalswamy, L. K. Jian, N. Lugaz

    ICMEs (interplanetary coronal mass ejections), the heliospheric counterparts of what is observed with coronagraphs at the Sun as CMEs, have been the subject of intense interest since their close association with geomagnetic storms was established in the 1980s. These major interplanetary plasma and magnetic field transients, often preceded and accompanied by solar energetic particles (SEPs), interact

  • Formation of Two Homologous Transequatorial Loops
    Sol. Phys. (IF 2.405) Pub Date : 2020-04-22
    Jie Chen, Alexei A. Pevtsov, Jiangtao Su, Robertus Erdélyi, Yuanyong Deng, Shangbin Yang, Yongliang Song

    The formation mechanism of two homologous transequatorial loops (TLs) of July 7–8, 1999 (SOL1999-07-07) is studied. The TLs connected active region AR 8614 from the northern hemisphere to AR 8626 in the southern hemisphere. The first TL appeared as a distinct structure at 12:49 UT on July 7, the second TL appeared at 06:21 UT, on July 8. Important results are obtained in this analysis: (i) The configuration

  • Comparative Study of a Sunspot at Two Different Instances of Time
    Sol. Phys. (IF 2.405) Pub Date : 2020-04-22
    Hashem Hamedivafa

    We investigate the evolutionary effects on the brightness of a sunspot as well as on the properties of its fine-structures using two sets of time series of G-band images of a single sunspot in NOAA 10944 recorded at two symmetric locations on the solar disc by Hinode/SOT (Solar Optical Telescope). The second time series (phase W) was recorded 2.5 d after recording the first time series (phase E). Both

  • Physical Characteristics of Umbral Dots Derived from a High-Resolution Observations
    Sol. Phys. (IF 2.405) Pub Date : 2020-04-21
    Ali Kilcik, Volkan Sarp, Vasyl Yurchyshyn, Jean-Pierre Rozelot, Atila Ozguc

    The aim of this study is to revisit the physical parameters of umbral dots (UDs) with the latest high-resolution observations and contribute to the scientific understanding of their formation and evolution. In this study, we applied a particle tracking algorithm for detecting UDs in NOAA AR 12384 observed on June 14, 2015 by the Goode Solar Telescope (GST). We analyzed average position distributions

  • HATS: A Ground-Based Telescope to Explore the THz Domain
    Sol. Phys. (IF 2.405) Pub Date : 2020-04-20
    C. Guillermo Giménez de Castro, Jean-Pierre Raulin, Adriana Valio, Guilherme Alaia, Vinicius Alvarenga, Emilio Carlos Bortolucci, Silvia Helena Fernandes, Carlos Francile, Tiago Giorgetti, Amauri Shossei Kudaka, Fernando Marcelo López, Rogério Marcon, Adolfo Marun, Márcio Zaquela

    The almost unexplored frequency window from submillimeter to mid-infrared (mid-IR) may bring new clues about the particle acceleration and transport processes and the atmospheric thermal response during solar flares. Because of its technical complexity and the special atmospheric environment needed, observations at these frequencies are very sparse. The High Altitude THz Solar Photometer (HATS) is

  • A Survey of Computational Tools in Solar Physics
    Sol. Phys. (IF 2.405) Pub Date : 2020-04-20
    Monica G. Bobra, Stuart J. Mumford, Russell J. Hewett, Steven D. Christe, Kevin Reardon, Sabrina Savage, Jack Ireland, Tiago M. D. Pereira, Bin Chen, David Pérez-Suárez

    The SunPy Project developed a 13-question survey to understand the software and hardware usage of the solar-physics community. Of the solar-physics community, 364 members across 35 countries responded to our survey. We found that \(99\pm 0.5\)% of respondents use software in their research and 66% use the Python scientific-software stack. Students are twice as likely as faculty, staff scientists, and

  • A Geoeffective CME Caused by the Eruption of a Quiescent Prominence on 29 September 2013
    Sol. Phys. (IF 2.405) Pub Date : 2020-04-17
    V. V. Grechnev, I. V. Kuzmenko

    The eruption of a large prominence that occurred away of active regions in the SOL2013-09-29 event produced a fast coronal mass ejection (CME) and a shock wave. The event caused considerable geospace disturbances, including a proton enhancement that have been addressed in previous studies. Continuing with the analysis of this event, we focus on the development of the CME and shock wave, assess an expected

  • Large-Scale Solar Magnetic Fields Observed with the Infrared Spectro-Polarimeter IRmag at the National Astronomical Observatory of Japan: Comparison of Measurements Made in Different Spectral Lines and Observatories
    Sol. Phys. (IF 2.405) Pub Date : 2020-04-15
    M. L. Demidov, Y. Hanaoka, T. Sakurai, X. F. Wang

    This study presents the results of a quantitative analysis of IRmag (infrared Stokes spectro-polarimeter, National Astronomical Observatory of Japan, (NAOJ)/Mitaka) observations in three spectral lines Fe i 1564.8 nm, Si i 1082.72 nm, He i 1083.0 nm, and comparison between IRmag magnetograms and ones from the Solar Dynamic Observatory/Helioseismic and Magnetic Imager (SDO/HMI), Global Oscillation Network

  • Temporal and Spatial Scales in Coronal Rain Revealed by UV Imaging and Spectroscopic Observations
    Sol. Phys. (IF 2.405) Pub Date : 2020-04-07
    Ryohtaroh T. Ishikawa, Yukio Katsukawa, Patrick Antolin, Shin Toriumi

    Coronal rain corresponds to cool and dense clumps in the corona accreting towards the solar surface; it is often observed above solar active regions. These clumps are generally thought to be produced by a thermal instability in the corona and their lifetime is limited by the time they take to reach the chromosphere. Although the rain usually fragments into smaller clumps while falling down, their specific

  • Studying Magnetic Field Variations Accompanying the 2011 June 7 Eruptive Event, by Using Nonlinear Force-Free Field Modeling
    Sol. Phys. (IF 2.405) Pub Date : 2020-04-06
    Y. I. Egorov, V. G. Fainshtein, I. I. Myshyakov, S. A. Anfinogentov, G. V. Rudenko

    We study the features of the magnetic field variations within the 2011 June 7 eruptive event that includes a large filament eruption, a flare, and a CME formation. The magnetic field characteristics were obtained by using vector measurements of the magnetic field with the SDO/HMI and 3D magnetic field calculations based on nonlinear force-free field (NLFFF) modeling. Strong and relatively fast variations

  • Spectropolarimetric Imaging of Metric Type III Solar Radio Bursts
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-31
    M. M. Rahman, Iver H. Cairns, Patrick I. McCauley

    We present low-frequency (80 – 240 MHz) radio observations of circular polarization in 16 isolated type III solar radio bursts using the Murchison Widefield Array (MWA) between August 2014 and November 2015. For most of the bursts, near burst onset, we find on average \(9\%\) circular polarization at 80 MHz and \(22\%\) at 240 MHz whereas these percentages are \(5\%\) and \(20\%\) near burst maximum

  • Comparing Radiative Transfer Codes and Opacity Samplings for Solar Irradiance Reconstructions
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-30
    Serena Criscuoli, Matthias Rempel, Margit Haberreiter, Tiago M. D. Pereira, Han Uitenbroek, Damian Fabbian

    Some techniques developed to reproduce solar irradiance variations make use of synthetic radiative fluxes of quiet and magnetic features. The synthesis of radiative fluxes of astronomical objects is likely to be affected by uncertainties resulting from approximations and specific input employed for the synthesis. In this work we compare spectra obtained with three radiative transfer codes with the

  • Comparison of Latitude Distribution and Evolution of Even and Odd Sunspot Cycles
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-30
    Jouni Takalo

    We study the latitudinal distribution and evolution of sunspot areas of Solar Cycles 12 – 23 (SC12–23) and sunspot groups of Solar Cycles 8 – 23 (SC8–23) for even and odd cycles. The Rician distribution is the best-fit function for both even and odd sunspots group latitudinal occurrence. The mean and variance for even northern/southern butterfly wing sunspots are 14.94/14.76 and 58.62/56.08, respectively

  • The Creation of Twist by Reconnection of Flux Tubes
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-25
    E. R. Priest, D. W. Longcope

    A fundamental process in a plasma is the magnetic reconnection of one pair of flux tubes (such as solar coronal loops) to produce a new pair. During this process magnetic helicity is conserved, but mutual helicity can be transformed to self-helicity, so that the new tubes acquire twist. However, until recently, when Wright (Astrophys. J.878, 102, 2019) supplied a solution, the partition of self-helicity

  • Solar-Cycle Variation of the Subsurface Flows of Active- and Quiet-Region Subsets
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-24
    R. Komm, R. Howe, F. Hill

    We study the solar-cycle variation of subsurface flows for both active and quiet solar regions. We derive flows from the surface to a depth of 16 Mm using ring-diagram analysis applied to Dopplergrams obtained with the Michelson Doppler Imager (MDI) Dynamics Program, the Global Oscillation Network Group (GONG), and the Helioseismic and Magnetic Imager (HMI) instrument. We derive the temporal variation

  • Large Amplitude Fluctuations in the Alfvénic Solar Wind
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-24
    R. D’Amicis, L. Matteini, R. Bruno, M. Velli

    Large amplitude fluctuations, often with characteristics reminiscent of large amplitude Alfvén waves propagating away from the Sun, are ubiquitous in the solar wind. Such features are most frequently found within fast solar wind streams and most often at solar minimum. The fluctuations found in slow solar wind streams usually have a smaller relative amplitude, are less Alfvénic in character and present

  • New Metric for Minimum Variance Analysis Validation in the Study of Interplanetary Magnetic Clouds
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-23
    Rosemeire Aparecida Rosa Oliveira, Marcos William da Silva Oliveira, Arian Ojeda-González, Victor De La Luz

    The aim of this article is to study the minimum variance analysis (MVA) degeneration problem based on the variance space geometry. We propose a mathematical metric to evaluate the separation of the eigenvalues. In the MVA method, a variance space is obtained geometrically using an ellipsoid where the axes are equal to the square root of the eigenvalues of the covariance matrix. The metric is defined

  • A Computationally Efficient, Time-Dependent Model of the Solar Wind for Use as a Surrogate to Three-Dimensional Numerical Magnetohydrodynamic Simulations
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-19
    Mathew Owens, Matthew Lang, Luke Barnard, Pete Riley, Michal Ben-Nun, Chris J. Scott, Mike Lockwood, Martin A. Reiss, Charles N. Arge, Siegfried Gonzi

    Near-Earth solar-wind conditions, including disturbances generated by coronal mass ejections (CMEs), are routinely forecast using three-dimensional, numerical magnetohydrodynamic (MHD) models of the heliosphere. The resulting forecast errors are largely the result of uncertainty in the near-Sun boundary conditions, rather than heliospheric model physics or numerics. Thus ensembles of heliospheric model

  • EUV Wave Detection and Characterization Using Deep Learning
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-19
    Long Xu, Sixuan Liu, Yihua Yan, Weiqiang Zhang

    Coronal Mass Ejections (CMEs) are the most violent solar bursts. They cause severe disturbances in the solar–terrestrial space and affect human activities in many aspects, especially causing damage to high-tech infrastructure. It usually takes few hours for a CME to arrive at the Earth after eruption. Therefore, many efforts have been devoted to CME arrival time prediction, so that we have enough time

  • Investigation into CME Shock Speed Resulting from Type II Solar Radio Bursts
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-18
    F. A. M. Pauzi, Z. Z. Abidin, S. J. Guo, G. N. Gao, L. Dong, C. Monstein

    An investigation into Type II solar radio bursts was carried out to understand the frequency gap between fundamental and harmonic emissions of the radio burst. This investigation focused on Type II solar radio bursts with flares and coronal mass ejections by relating the separation between fundamental and harmonic emissions. We used the Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy

  • Data-Driven Classification of Coronal Hole and Streamer Belt Solar Wind
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-17
    Téo Bloch, Clare Watt, Mathew Owens, Leland McInnes, Allan R. Macneil

    We present two new solar wind origin classification schemes developed independently using unsupervised machine learning. The first scheme aims to classify solar wind into three types: coronal-hole wind, streamer-belt wind, and ‘unclassified’ which does not fit into either of the previous two categories. The second scheme independently derives three clusters from the data; the coronal-hole and streamer-belt

  • Comparison of Toroidal Interplanetary Flux-rope Model Fitting with Different Boundary Pitch-angle Treatments
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-16
    N. Nishimura, K. Marubashi, M. Tokumaru

    We developed a new fitting method of a toroidal model for the analysis of interplanetary flux ropes (IFRs). The pitch angle of the magnetic field at the IFR boundary [\(\alpha_{\mathrm{p}}\)] is fixed to \(90^{\circ}\) in the toroidal model of Romashets and Vandas (Geophys. Res. Lett.30, 2065, 2003) (conventional method). To relax this condition for our method, the pitch angle was made one of the free

  • Sunspot Positions and Areas from Observations by Thomas Harriot
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-10
    Mikhail Vokhmyanin, Rainer Arlt, Nadezhda Zolotova

    The reconstruction of sunspot parameters in the early era of telescopic observations extends our knowledge on visual sunspot activity up to 400 years into the past. 200 digital solar images from 18 December 1610 to 28 January 1613 by the English astronomer Thomas Harriot were analyzed to yield sunspot counts, areas and positions. Harriot generally observed in the early morning when the Sun was near

  • Long-term (1749–2015) Variations of Solar UV Spectral Indices
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-09
    Francesco Berrilli, Serena Criscuoli, Valentina Penza, Mija Lovric

    Abstract Solar radiation variability spans a wide range in time, ranging from seconds to decadal and longer. The nearly 40 years of measurements of solar irradiance from space established that the total solar irradiance varies by \(\approx 0.1\%\) in phase with the Sun’s magnetic cycle. Specific intervals of the solar spectrum, e.g., ultraviolet (UV), vary by orders of magnitude more. These variations

  • Signatures of Coronal Loop Opening via Interchange Reconnection in the Slow Solar Wind at 1 AU
    Sol. Phys. (IF 2.405) Pub Date : 2020-03-02
    Mathew Owens, Mike Lockwood, Allan Macneil, David Stansby

    Abstract The opening of closed magnetic loops via reconnection with open solar flux, so called “interchange reconnection”, is invoked in a number of models of slow solar wind release. In the heliosphere, this is expected to result in local switchbacks or inversions in heliospheric magnetic flux (HMF). When observed at 1 AU, inverted HMF has previously been shown to exhibit high ion charge states, suggestive

  • Locating Hot Plasma in Small Flares using Spectroscopic Overlappogram Data from the Hinode EUV Imaging Spectrometer
    Sol. Phys. (IF 2.405) Pub Date : 2020-02-27
    Louise Harra, Sarah Matthews, David Long, Takahiro Hasegawa, Kyoung-Sun Lee, Katharine K. Reeves, Toshifumi Shimizu, Hirohisa Hara, Magnus Woods

    Abstract One of the key processes associated with the “standard” flare model is chromospheric evaporation, a process during which plasma heated to high temperatures by energy deposition at the flare footpoints is driven upwards into the corona. Despite several decades of study, a number of open questions remain, including the relationship between plasma produced during this process and observations

  • Timing Terminators: Forecasting Sunspot Cycle 25 Onset
    Sol. Phys. (IF 2.405) Pub Date : 2020-02-27
    Robert J. Leamon, Scott W. McIntosh, Sandra C. Chapman, Nicholas W. Watkins

    Abstract Recent research has demonstrated the existence of a new type of solar event, the “terminator.” Unlike the Sun’s signature events, flares and coronal mass ejections, the terminator most likely originates in the solar interior, at or near the tachocline. The terminator signals the end of a magnetic activity cycle at the Sun’s equator and the start of a sunspot cycle at mid-latitudes. Observations

  • The Properties of Source Locations and Solar Cycle Distribution of GLEs During 1942–2017
    Sol. Phys. (IF 2.405) Pub Date : 2020-02-27
    Gui-Ming Le, Gui-Ang Liu

    Abstract During 1942–2017, 72 ground level events (GLEs) have been registered. Source location and solar cycle distribution of GLEs during 1942–2017 have been investigated. The GLEs that occurred during 1942–2017 are mainly distributed in the longitudinal area ranged from E30 to W150. The northern hemisphere has many more GLEs than the southern hemisphere during Solar Cycles 19 and 20, while the northern

  • Solar Oscillations and the Orbital Invariant Inequalities of the Solar System
    Sol. Phys. (IF 2.405) Pub Date : 2020-02-26
    Nicola Scafetta

    Abstract Gravitational planetary lensing of slow-moving matter streaming towards the Sun was suggested to explain puzzling solar-flare occurrences and other unexplained solar-emission phenomena (Bertolucci et al. in Phys. Dark Universe17, 13, 2017). If it is actually so, the effect of gravitational lensing of this stream by heavy planets (Jupiter, Saturn, Uranus and Neptune) could be manifested in

  • Comprehensive Characterization of Solar Eruptions with Remote and In-Situ Observations, and Modeling: The Major Solar Events on 4 November 2015
    Sol. Phys. (IF 2.405) Pub Date : 2020-02-20
    Iver H. Cairns, Kamen A. Kozarev, Nariaki V. Nitta, Neus Agueda, Markus Battarbee, Eoin P. Carley, Nina Dresing, Raúl Gómez-Herrero, Karl-Ludwig Klein, David Lario, Jens Pomoell, Carolina Salas-Matamoros, Astrid M. Veronig, Bo Li, Patrick McCauley

    Abstract Solar energetic particles (SEPs) are an important product of solar activity. They are connected to solar active regions and flares, coronal mass ejections (CMEs), EUV waves, shocks, Type II and III radio emissions, and X-ray bursts. These phenomena are major probes of the partition of energy in solar eruptions, as well as for the organization, dynamics, and relaxation of coronal and interplanetary

  • Measurement and Correction of Instrumental Profiles for the Spectral Data of the New Vacuum Solar Telescope
    Sol. Phys. (IF 2.405) Pub Date : 2020-02-18
    Yunfang Cai, Zhi Xu, Kaifan Ji

    Abstract The ideal optical system can realize point-to-point imaging, but for an actual observation it is difficult to achieve this ideal phenomenon due to the instrumental effects of imaging system, which is usually described as the instrument profile in the imaging process of a grating spectrometer. The existence of the spectrometer instrument profiles introduces systematic errors in the observed

  • Fizeau Mask Interferometry of Solar Features Using the Multi-application Solar Telescope at the Udaipur Solar Observatory
    Sol. Phys. (IF 2.405) Pub Date : 2020-02-17
    A. Raja Bayanna, P. Venkatakrishnan, Sridharan Rengaswamy, Shibu K. Mathew

    Abstract Efforts are made to demonstrate high-resolution observations of the solar atmosphere using spatial interferometry. Covering the telescope pupil with a Fizeau mask consisting of two small circular apertures separated by a vector distance known as the baseline is the first step towards interferometric imaging. A mask with two circular holes of diameter 7 cm each and separated by a distance of

  • CME Productive and Non-productive Recurring Jets Near an Active Region AR11176
    Sol. Phys. (IF 2.405) Pub Date : 2020-02-12
    Ritika Solanki, Abhishek K. Srivastava, Bhola N. Dwivedi

    Abstract We study the recurring jets near AR11176 during the period 2011 March 31 17:00 UT to April 1 05:00 UT using observations from the Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory (SDO). Mini-filaments (mini-filament1 & 2) are found at the base of these recurring jets where mini-filament1 shows the partial signature of eruption in case of Jet1–3. However, the mini-filament2

  • Source of Energetic Protons in the 2014 September 1 Sustained Gamma-ray Emission Event.
    Sol. Phys. Pub Date : 2020-02-04
    N Gopalswamy,P Mäkelä,S Yashiro,S Akiyama,H Xie,N Thakur

    We report on the source of > 300 MeV protons during the SOL2014-09-01 sustained gamma-ray emission (SGRE) event based on multi-wavelength data from a wide array of space- and ground-based instruments. Based on the eruption geometry we provide concrete explanation for the spatially and temporally extended γ -ray emission from the eruption. We show that the associated flux rope is of low inclination

  • Definition of the Spatial Propagator and Implications for Magnetic Field Properties.
    Sol. Phys. Pub Date : 2019-07-02
    Justin K Edmondson,Pascal Démoulin

    We present a theoretical framework to analyze the 3D coronal vector magnetic-field structure. We assume that the vector magnetic field exists and is a priori smooth. We introduce a generalized connectivity phase space associated with the vector magnetic field in which the basic elements are the field line and its linearized variation: the Spatial Propagator. We provide a direct formulation of these

  • Time-dependent Data-driven Modeling of Active Region Evolution Using Energy-optimized Photospheric Electric Fields.
    Sol. Phys. Pub Date : 2019-05-07
    Jens Pomoell,Erkka Lumme,Emilia Kilpua

    In this work, we present results of a time-dependent data-driven numerical simulation developed to study the dynamics of coronal active region magnetic fields. The evolving boundary condition driving the model, the photospheric electric field, is inverted using a time sequence of vector magnetograms as input. We invert three distinct electric field datasets for a single active region. All three electric

  • Solar Terrestrial Relations Observatory (STEREO) Observations of Stream Interaction Regions in 2007 - 2016: Relationship with Heliospheric Current Sheets, Solar Cycle Variations, and Dual Observations.
    Sol. Phys. Pub Date : 2019-03-06
    L K Jian,J G Luhmann,C T Russell,A B Galvin

    We have conducted a survey of 575 slow-to-fast stream interaction regions (SIRs) using Solar Terrestrial Relations Observatory (STEREO) A and B data, analyzing their properties while extending a Level-3 data product through 2016. Among 518 pristine SIRs, 54% are associated with heliospheric current sheet (HCS) crossings, and 34% are without any HCS crossing. The other 12% of the SIRs often occur in

  • An on Orbit Determination of Point Spread Functions for the Interface Region Imaging Spectrograph.
    Sol. Phys. Pub Date : 2018-11-06
    Hans Courrier,Charles Kankelborg,Bart De Pontieu,Jean-Pierre Wülser

    Using the 2016 Mercury transit of the Sun, we characterize on orbit spatial point spread functions (PSFs) for the Near- (NUV) and Far- (FUV) Ultra-Violet spectrograph channels of NASA's Interface Region Imaging Spectrograph (IRIS). A semi-blind Richardson-Lucy deconvolution method is used to estimate PSFs for each channel. Corresponding estimates of Modulation Transfer Functions (MTFs) indicate resolution

  • Linear Polarization Features in the Quiet-Sun Photosphere: Structure and Dynamics.
    Sol. Phys. Pub Date : 2018-11-06
    S Kianfar,S Jafarzadeh,M T Mirtorabi,T L Riethmüller

    We present detailed characteristics of linear polarization features (LPFs) in the quiet-Sun photosphere from high-resolution observations obtained with Sunrise/IMaX. We explore differently treated data with various noise levels in linear polarization signals, from which structure and dynamics of the LPFs are studied. Physical properties of the detected LPFs are also obtained from the results of Stokes

  • Magnetic Clouds: Solar Cycle Dependence, Sources, and Geomagnetic Impacts.
    Sol. Phys. Pub Date : 2018-11-06
    Y Li,J G Luhmann,B J Lynch

    Magnetic clouds (MCs) are transient magnetic structures giving the strongest southward magnetic field (Bz south) in the solar wind. The sheath regions of MCs may also carry a southward magnetic field. The southward magnetic field is responsible for space-weather disturbances. We report a comprehensive analysis of MCs and Bz components in their sheath regions for 1995 to 2017. 85% of 303 MCs contain

  • Correlation of ICME Magnetic Fields at Radially Aligned Spacecraft.
    Sol. Phys. Pub Date : 2018-03-24
    S W Good,R J Forsyth,J P Eastwood,C Möstl

    The magnetic field structures of two interplanetary coronal mass ejections (ICMEs), each observed by a pair of spacecraft close to radial alignment, have been analysed. The ICMEs were observed in situ by MESSENGER and STEREO-B in November 2010 and November 2011, while the spacecraft were separated by more than 0.6 AU in heliocentric distance, less than 4° in heliographic longitude, and less than 7°

  • Statistical Properties of Ribbon Evolution and Reconnection Electric Fields in Eruptive and Confined Flares.
    Sol. Phys. Pub Date : 2018-03-02
    J Hinterreiter,A M Veronig,J K Thalmann,J Tschernitz,W Pötzi

    A statistical study of the chromospheric ribbon evolution in H[Formula: see text] two-ribbon flares was performed. The data set consists of 50 confined (62%) and eruptive (38%) flares that occurred from June 2000 to June 2015. The flares were selected homogeneously over the H[Formula: see text] and Geostationary Operational Environmental Satellite (GOES) classes, with an emphasis on including powerful

  • A New Inner Heliosphere Proton Parameter Dataset from the Helios Mission.
    Sol. Phys. Pub Date : 2018-01-01
    David Stansby,Chadi Salem,Lorenzo Matteini,Timothy Horbury

    In the near future, Parker Solar Probe and Solar Orbiter will provide the first comprehensive in-situ measurements of the solar wind in the inner heliosphere since the Helios mission in the 1970s. We describe a reprocessing of the original Helios ion distribution functions to provide reliable and reproducible data to characterise the proton core population of the solar wind in the inner heliosphere

  • GONG p-Mode Parameters Through Two Solar Cycles.
    Sol. Phys. Pub Date : 2018-01-01
    René Kiefer,Rudi Komm,Frank Hill,Anne-Marie Broomhall,Markus Roth

    We investigate the parameters of global solar p-mode oscillations, namely damping width Γ , amplitude A , mean squared velocity 〈 v 2 〉 , energy E , and energy supply rate d E / d t , derived from two solar cycles' worth (1996 - 2018) of Global Oscillation Network Group (GONG) time series for harmonic degrees l = 0 - 150 . We correct for the effect of fill factor, apparent solar radius, and spurious

  • Instrument Calibration of the Interface Region Imaging Spectrograph (IRIS) Mission.
    Sol. Phys. Pub Date : 2018-01-01
    J-P Wülser,S Jaeggli,B De Pontieu,T Tarbell,P Boerner,S Freeland,W Liu,R Timmons,S Brannon,C Kankelborg,C Madsen,S McKillop,J Prchlik,S Saar,N Schanche,P Testa,P Bryans,M Wiesmann

    The Interface Region Imaging Spectrograph (IRIS) is a NASA small explorer mission that provides high-resolution spectra and images of the Sun in the 133 - 141 nm and 278 - 283 nm wavelength bands. The IRIS data are archived in calibrated form and made available to the public within seven days of observing. The calibrations applied to the data include dark correction, scattered light and background

  • On the Performance of Multi-Instrument Solar Flare Observations During Solar Cycle 24.
    Sol. Phys. Pub Date : 2018-01-01
    Ryan O Milligan,Jack Ireland

    The current fleet of space-based solar observatories offers us a wealth of opportunities to study solar flares over a range of wavelengths. Significant advances in our understanding of flare physics often come from coordinated observations between multiple instruments. Consequently, considerable efforts have been, and continue to be, made to coordinate observations among instruments (e.g. through the

  • On-Orbit Performance of the Helioseismic and Magnetic Imager Instrument onboard the Solar Dynamics Observatory.
    Sol. Phys. Pub Date : 2018-01-01
    J T Hoeksema,C S Baldner,R I Bush,J Schou,P H Scherrer

    The Helioseismic and Magnetic Imager (HMI) instrument is a major component of NASA's Solar Dynamics Observatory (SDO) spacecraft. Since commencement of full regular science operations on 1 May 2010, HMI has operated with remarkable continuity, e.g. during the more than five years of the SDO prime mission that ended 30 September 2015, HMI collected 98.4% of all possible 45-second velocity maps; minimizing

  • Flux Rope Formation Due to Shearing and Zipper Reconnection.
    Sol. Phys. Pub Date : 2018-01-01
    J Threlfall,A W Hood,E R Priest

    Zipper reconnection has been proposed as a mechanism for creating most of the twist in the flux tubes that are present prior to eruptive flares and coronal mass ejections. We have conducted a first numerical experiment on this new regime of reconnection, where two initially untwisted parallel flux tubes are sheared and reconnected to form a large flux rope. We describe the properties of this experiment

  • Decoupling Solar Variability and Instrument Trends Using the Multiple Same-Irradiance-Level (MuSIL) Analysis Technique.
    Sol. Phys. Pub Date : 2018-01-01
    Thomas N Woods,Francis G Eparvier,Jerald Harder,Martin Snow

    The solar spectral irradiance (SSI) dataset is a key record for studying and understanding the energetics and radiation balance in Earth's environment. Understanding the long-term variations of the SSI over timescales of the 11-year solar activity cycle and longer is critical for many Sun-Earth research topics. Satellite measurements of the SSI have been made since the 1970s, most of them in the ultraviolet

  • Magnetic Helicity as a Predictor of the Solar Cycle.
    Sol. Phys. Pub Date : 2018-01-01
    G Hawkes,M A Berger

    It is well known that the polar magnetic field is at its maximum during solar minima, and that the behaviour during this time acts as a strong predictor of the strength of the following solar cycle. This relationship relies on the action of differential rotation (the Omega effect) on the poloidal field, which generates the toroidal flux observed in sunspots and active regions. We measure the helicity

  • Propagation of Leaky MHD Waves at Discontinuities with Tilted Magnetic Field.
    Sol. Phys. Pub Date : 2018-01-01
    E Vickers,I Ballai,R Erdélyi

    We investigate the characteristics of magneto-acoustic surface waves propagating at a single density interface, in the presence of an inclined magnetic field. For linear wave propagation, the dispersion relation is obtained and analytical solutions are derived for small inclination angle. The inclination of the field renders the frequency of the waves complex, where the imaginary part describes wave

  • On Flare-CME Characteristics from Sun to Earth Combining Remote-Sensing Image Data with In Situ Measurements Supported by Modeling.
    Sol. Phys. Pub Date : 2017-07-22
    Manuela Temmer,Julia K Thalmann,Karin Dissauer,Astrid M Veronig,Johannes Tschernitz,Jürgen Hinterreiter,Luciano Rodriguez

    We analyze the well-observed flare and coronal mass ejection (CME) from 1 October 2011 (SOL2011-10-01T09:18) covering the complete chain of effects - from Sun to Earth - to better understand the dynamic evolution of the CME and its embedded magnetic field. We study in detail the solar surface and atmosphere associated with the flare and CME using the Solar Dynamics Observatory (SDO) and ground-based

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