Asteroseismology: The Impact of Solar Space Observations

1993 ◽  
Vol 137 ◽  
pp. 43-50
Author(s):  
H.S. Hudson
Keyword(s):  
Solar Flares ◽  
Coronal Holes ◽  
Magnetic Activity ◽  
Solar Interior ◽  
Small Bodies ◽  
Solar Observations ◽  
Global Properties ◽  
Stellar Convection ◽  
Technical Report ◽  
The Impact

AbstractObservations from space relevant to solar global properties (oscillations, magnetic activity, etc.) are helpful both scientifically and technically in preparing for stellar observations. This paper summarizes the results from the main previous experiments (ACRIM, SOUP, and IPHIR), and also give an initial technical report from the SXT instrument on board Yohkoh, launched in August 1991. The solar observations to date demonstrate the existence of several mechanisms for low–level variability: spots, faculae, the photospheric network, granulation, and p–mode oscillations. The observations of oscillations have been particularly helpful in setting limits on solar interior rotation. In addition to the solar processes, stars of other types may have different mechanisms of variability. These may include the analogues of coronal holes or solar flares, modes of oscillation not detected in the Sun, collisions with small bodies, duplicity, and probably mechanisms not invented yet but related in interesting ways to stellar convection and magnetism.

scholarly journals Impact of magnetic activity on inferred stellar properties of main-sequence Sun-like stars

2021 ◽  
Vol 502 (4) ◽  
pp. 5808-5820
Author(s):  
Alexandra E L Thomas ◽  
William J Chaplin ◽  
Sarbani Basu ◽  
Ben Rendle ◽  
Guy Davies ◽  
...  
Keyword(s):  
Magnetic Activity ◽  
Frequency Separation ◽  
Near Surface ◽  
Global Properties ◽  
Modelling Analysis ◽  
Inclination Angles ◽  
Stellar Properties ◽  
Oscillation Frequencies ◽  
Frequency Ratios ◽  
The Impact

ABSTRACT The oscillation frequencies observed in Sun-like stars are susceptible to being shifted by magnetic activity effects. The measured shifts depend on a complex relationship involving the mode type, the field strength, and spatial distribution of activity, as well as the inclination angle of the star. Evidence of these shifts is also present in frequency separation ratios that are often used when inferring global properties of stars in order to avoid surface effects. However, one assumption when using frequency ratios for this purpose is that there are no near-surface perturbations that are non-spherically symmetric. In this work, we studied the impact on inferred stellar properties when using frequency ratios that are influenced by non-homogeneous activity distributions. We generate several sets of artificial oscillation frequencies with various amounts of shift and determine stellar properties using two separate pipelines. We find that for asteroseismic observations of Sun-like targets we can expect magnetic activity to affect mode frequencies that will bias the results from stellar modelling analysis. Although for most stellar properties this offset should be small, typically less than 0.5 per cent in mass, estimates of age and central hydrogen content can have an error of up to 5 per cent and 3 per cent, respectively. We expect a larger frequency shift and therefore larger bias for more active stars. We also warn that for stars with very high or low inclination angles, the response of modes to activity is more easily observable in the separation ratios and hence will incur a larger bias.

scholarly journals Some kinematics of halo coronal mass ejections

2020 ◽  
Vol 29 (1) ◽  
pp. 81-88
Author(s):  
Virendra Kumar Verma ◽  
Nishant Mittal ◽  
Ramesh Chandra
Keyword(s):  
Coronal Mass Ejections ◽  
Solar Flares ◽  
Coronal Holes ◽  
Geomagnetic Disturbances ◽  
Class A ◽  
Heliospheric Physics ◽  
Class B ◽  
The Mean ◽  
Class C

AbstractWe present an investigation of halo coronal mass ejections (HCMEs) kinematics and other facts about the HCMEs. The study of HCMEs is very important because HCMEs are regarded as the main causes of heliospheric and geomagnetic disturbances. In this study, we have investigated 313 HCMEs observed during 1996-2012 by LASCO, coronal holes, and solar flares. We find that HCMEs are of two types: accelerated HCMEs and decelerated HCMEs. The mean space speed of HCMEs is 1283 km/s while the mean speed of decelerated HCMEs and accelerated HCMEs is 1349 km/s and 1174 km/s, respectively. The investigation shows that 1 (0.3%) HCME was associated with class A SXR, 14 (4.7%) HCMEs were associated with class B SXR-flares, 87 (29.4%) HCMEs were associated with class C SXR-flares, 125 (42.2%) HCMEs were associated with class M SXR-flares and 69 (23.3%) HCMEs were associated with class X SXR-flares. The speed of HCMEs increases with the importance of solar SXR-flares. The various results obtained in the present analysis are discussed in the light of the existing scenario of heliospheric physics.

scholarly journals Impact of Membrane Computing and P Systems in ISI WoS. Celebrating the 65th Birthday of Gheorghe Păun

2015 ◽  
Vol 10 (5) ◽  
Author(s):  
Ioan DZITAC
Keyword(s):  
Computer Science ◽  
Membrane Computing ◽  
Research Area ◽  
P Systems ◽  
65Th Birthday ◽  
Membrane Systems ◽  
Journal Paper ◽  
Technical Report ◽  
The Impact

Membrane Computing is a branch of Computer Science initiated by<br />Gheorghe Păun in 1998, in a technical report of Turku Centre for Computer Science<br />published as a journal paper ("Computing with Membranes" in Journal of Computer<br />and System Sciences) in 2000. Membrane systems, as Gheorghe Păun called the<br />models he has introduced, are known nowadays as "P Systems" (with the letter P<br />coming from the initial of the name of this research area "father").<br />This note is an overview of the impact in ISI WoS of Gheorghe Păun’s works, focused<br />on Membrane Computing and P Systems field, on the occasion of his 65th birthday<br />anniversary.

The Impact of Marijuana Policies on Youth: Clinical, Research, and Legal Update

2017 ◽  
pp. 39-55
Author(s):  
Seth Ammerman ◽  
Sheryl Ryan ◽  
William P. Adelman
Keyword(s):  
Marijuana Use ◽  
The United States ◽  
Criminal Prosecution ◽  
Policy Statement ◽  
American Academy Of Pediatrics ◽  
Technical Report ◽  
The Impact ◽  
Recreational Use ◽  
Adolescent Marijuana Use ◽  
Adolescent Brain Development

This technical report updates the 2004 American Academy of Pediatrics technical report on the legalization of marijuana. Current epidemiology of marijuana use is presented, as are definitions and biology of marijuana compounds, side effects of marijuana use, and effects of use on adolescent brain development. Issues concerning medical marijuana specifically are also addressed. Concerning legalization of marijuana, 4 different approaches in the United States are discussed: legalization of marijuana solely for medical purposes, decriminalization of recreational use of marijuana, legalization of recreational use of marijuana, and criminal prosecution of recreational (and medical) use of marijuana. These approaches are compared, and the latest available data are presented to aid in forming public policy. The effects on youth of criminal penalties for marijuana use and possession are also addressed, as are the effects or potential effects of the other 3 policy approaches on adolescent marijuana use. Recommendations are included in the accompanying policy statement.

scholarly journals The Environment of the Young Earth in the Perspective of An Young Sun

2016 ◽  
Vol 12 (S328) ◽  
pp. 315-328
Author(s):  
Vladimir S. Airapetian
Keyword(s):  
Space Weather ◽  
Solar Flares ◽  
Geomagnetic Storms ◽  
Lower Atmosphere ◽  
Early Earth ◽  
Uv Emission ◽  
Weather Events ◽  
Active Stars ◽  
Magnetohydrodynamic Models ◽  
The Impact

AbstractOur Sun, a magnetically mild star, exhibits space weather in the form of magnetically driven solar explosive events (SEE) including solar flares, coronal mass ejections and energetic particle events. We use Kepler data and reconstruction of X-ray and UV emission from young solar-like stars to recover the frequency and energy fluxes from extreme events from active stars including the young Sun. Extreme SEEs from a magnetically active young Sun could significantly perturb the young Earth's magnetosphere, cause strong geomagnetic storms, initiate escape and introduce chemical changes in its lower atmosphere. I present our recent simulations results based on multi-dimensional multi-fluid hydrodynamic and magnetohydrodynamic models of interactions of extreme CME and SEP events with magnetospheres and lower atmospheres of early Earth and exoplanets around active stars. We also discuss the implications of the impact of these effects on evolving habitability conditions of the early Earth and prebiotic chemistry introduced by space weather events at the early phase of evolution of our Sun.

scholarly journals TOMOGRAPHY OF THE SOLAR INTERIOR

2006 ◽  
Vol 21 (22) ◽  
pp. 1701-1715 ◽  
Author(s):  
L. GIZON
Keyword(s):  
Gravity Waves ◽  
Acoustic Waves ◽  
Solar Surface ◽  
Three Dimensional ◽  
Magnetic Activity ◽  
Solar Interior ◽  
Turbulent Convection ◽  
Convective Structures ◽  
Surface Gravity Waves ◽  
Rich Spectrum

Solar oscillations consist of a rich spectrum of internal acoustic waves and surface gravity waves, stochastically excited by turbulent convection. They have been monitored almost continuously over the last ten years with high-precision Doppler images of the solar surface. The purpose of helioseismology is to retrieve information about the structure and the dynamics of the solar interior from the frequencies, phases and amplitudes of solar waves. Methods of analysis are being developed to make three-dimensional images of subsurface motions and temperature inhomogeneities in order to study convective structures and regions of magnetic activity, like sunspots.

scholarly journals On the Association between Coronal Mass Ejections and Coronal Holes

1989 ◽  
Vol 104 (2) ◽  
pp. 239-242
Author(s):  
V.K. Verma ◽  
M.C. Pande
Keyword(s):  
Magnetic Field ◽  
Coronal Mass Ejection ◽  
Coronal Mass Ejections ◽  
Solar Flares ◽  
Coronal Holes ◽  
Mass Ejection ◽  
Open Magnetic Field

AbstractThe coronal mass ejection (CME) data and the data for coronal holes for the period 1979-1982 are compared locationwise. Out of 79 CMEs whose locations and spans are known, 48 (61%) CMEs are associated with coronal holes. We make a tentative suggestion that probably the mass ejected during solar flares and active prominences may move along the open magnetic field of the coronal holes and appear as CMEs.

scholarly journals Stellar activity and coronal heating: an overview of recent results

2015 ◽  
Vol 373 (2042) ◽  
pp. 20140259 ◽  
Author(s):  
Paola Testa ◽  
Steven H. Saar ◽  
Jeremy J. Drake
Keyword(s):  
Magnetic Activity ◽  
Coronal Heating ◽  
Complementary Information ◽  
Stellar Activity ◽  
X Ray ◽  
Solar Observations ◽  
Term Evolution ◽  
Wide Range ◽  
Stellar Magnetic Fields

Observations of the coronae of the Sun and of solar-like stars provide complementary information to advance our understanding of stellar magnetic activity, and of the processes leading to the heating of their outer atmospheres. While solar observations allow us to study the corona at high spatial and temporal resolution, the study of stellar coronae allows us to probe stellar activity over a wide range of ages and stellar parameters. Stellar studies therefore provide us with additional tools for understanding coronal heating processes, as well as the long-term evolution of solar X-ray activity. We discuss how recent studies of stellar magnetic fields and coronae contribute to our understanding of the phenomenon of activity and coronal heating in late-type stars.

Atmospheric escape from rocky M-dwarf planets orbiting within the habitable zone

2020 ◽  
Author(s):  
Chuanfei Dong
Keyword(s):  
Space Weather ◽  
Climate Science ◽  
Magnetic Activity ◽  
Habitable Zone ◽  
Atmospheric Escape ◽  
Dwarf Planets ◽  
James Webb Space Telescope ◽  
Wide Range ◽  
The Many ◽  
The Impact

&lt;p&gt;In the last two decades, the field of exoplanets has witnessed a tremendous creative surge. Research in exoplanets now encompasses a wide range of fields ranging from astrophysics to heliophysics and climate science. One of the primary objectives of studying exoplanets is to determine the criteria for habitability, and whether certain exoplanets meet these requirements. The classical definition of the Habitable Zone (HZ) is the region around a star where liquid water can exist on the planetary surface given sufficient atmospheric pressure. However, this definition largely ignores the impact of the stellar wind and stellar magnetic activity on the erosion of an exoplanet's atmosphere. Amongst the many factors that determine habitability, understanding the mechanisms of atmospheric loss is of paramount importance.&lt;/p&gt;&lt;p&gt;We will discuss the impact of exoplanetary space weather on the&amp;#160;long-term climate evolution and habitability, which offers fresh insights concerning the habitability of exoplanets, especially those orbiting M-dwarfs, such as Proxima b and the TRAPPIST-1 planets. We will focus on a wide range of atmospheric compositions, ranging from exo-Venus candidates to Earth twins, as many factors remain unresolved at this stage. Future missions such as the James Webb Space Telescope (JWST) will play a crucial role in constraining the atmospheres of those exoplanets.&amp;#160;For each of these cases, we will demonstrate the importance of the exoplanetary space weather on atmospheric ion loss and habitability.&lt;/p&gt;

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