Mechanisms of Chromospheric and Coronal Heating

Mechanisms of Chromospheric and Coronal Heating
Author: Peter Ulmschneider
Publisher: Springer Science & Business Media
Total Pages: 663
Release: 2013-06-29
Genre: Science
ISBN: 364287455X

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One of the great problems of astrophysics is the unanswered question about the origin and mechanism of chromospheric and coronal heating. Just how these outer stellar envelopes are heated is of fundamental importance, since all stars have hot chromospheric and coronal shells where the temperature rises to millions of degrees, comparable to the temperatures in the stars' cores. Here for the first time is a comprehensive inventory of the proposed chromospheric and coronal heating theories. The proposed heating processes are critically compared, and the observational evidence for the various mechanisms is reviewed. This is essential reading for all those working in such fields as stellar activity, radio and XUV emission, rotation, and mass loss, for whom a detailed and consistent presentation of our knowledge of chromospheric and coronal heating mechanisms is urgently needed.

Mechanisms of Chromospheric and Coronal Heating

Mechanisms of Chromospheric and Coronal Heating
Author: Peter Ulmschneider
Publisher: Springer
Total Pages: 649
Release: 1991-02-25
Genre: Science
ISBN: 9783540534365

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One of the great problems of astrophysics is the unanswered question about the origin and mechanism of chromospheric and coronal heating. Just how these outer stellar envelopes are heated is of fundamental importance, since all stars have hot chromospheric and coronal shells where the temperature rises to millions of degrees, comparable to the temperatures in the stars' cores. Here for the first time is a comprehensive inventory of the proposed chromospheric and coronal heating theories. The proposed heating processes are critically compared, and the observational evidence for the various mechanisms is reviewed. This is essential reading for all those working in such fields as stellar activity, radio and XUV emission, rotation, and mass loss, for whom a detailed and consistent presentation of our knowledge of chromospheric and coronal heating mechanisms is urgently needed.

The Problem of Coronal Heating

The Problem of Coronal Heating
Author: Philip Judge
Publisher: Springer Nature
Total Pages: 275
Release:
Genre:
ISBN: 3031462734

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Solar Coronal Heating by Microflares and Nanoflares

Solar Coronal Heating by Microflares and Nanoflares
Author: Vinod Kumar Joshi
Publisher: LAP Lambert Academic Publishing
Total Pages: 188
Release: 2012-06
Genre:
ISBN: 9783659141539

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The sun is a main sequence G2V star, based on Hertzsprung-Russel(H-R)diagram classification. Earlier studies have shown that the temperature of the core is about 15 MK and as we move away from the core, temperature decreases from 15 MK to 5800 K at photosphere. There is anomalous variation of temperature after photosphere, it starts increasing for further layers and there is abrupt change in temperature from transition region to corona. After the corona, temperature decreases again slowly. The temperature of the corona is found millions of kelvin higher than that of the surface temperature. This major unresolved fact in astrophysics is known as "solar coronal heating" problem. Several mechanisms of solar coronal heating have been discussed but none of the mechanisms is able to account for the extreme coronal temperature. This book is aimed towards the theoretical studies of solar coronal heating mechanisms by microflares and nanoflares. Here we have addressed the solution of solar coronal heating problem, using the phenomena of solar flares. Solar flares are the most interesting phenomena of the sun, which occur suddenly by releasing enormous amount of energy in a very short time.

Rapid Magnetic Energy Release, Its Possible Role in Coronal Heating and Solar Wind Acceleration

Rapid Magnetic Energy Release, Its Possible Role in Coronal Heating and Solar Wind Acceleration
Author: George L. Withbroe
Publisher:
Total Pages: 51
Release: 1983
Genre:
ISBN:

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Studies of the EUV emission from coronal bright points, active regions and apicules suggest taht stochastic mechanisms may plan an important role in heating the solar atmosphere at chromospheric and coronal levels. In small magnetic bipolar regions (spatial extent 1') the observed EUV variations suggest that impulsive heating at chromospheric and coronal levels appears to be very important, possibly the dominant form of heating. The mechanism most likely involves rapid release of magnetic energy, possibly associated with the emergence of magnetic flux from lower levels into the chromosphere and corona. In larger scale ( 1') magnetic bipolar regions, there is evidence for both quasi-steady and impulsive heating, with quasi-steady heating dominating. This heating could be caused by either a mechanism such as steady-state current dissipation, or by a stochastic process whose integrated effect (resulting from the smoothing caused by finite radiative and conductive cooling times) yields a nearly constant radiative output. The widespread variability of the emission in spectral lines formed at transition region temperatures (100000

The Solar Corona

The Solar Corona
Author: Leon Golub
Publisher: Cambridge University Press
Total Pages: 362
Release: 1997-08-21
Genre: Science
ISBN: 9780521485357

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Observations from the ground and space have advanced our knowledge of the solar corona dramatically over the last three decades. This textbook is the first to present this new understanding at a level appropriate for advanced undergraduate and graduate students, and researchers seeking an entry-point into the research literature. This timely volume presents a lucid and synthesised review of the latest observations of the solar corona and how they have advanced and shaped our understanding of coronal physics. This book provides a much-needed introduction to coronal physics for advanced students and researchers.

Catastrophic Cooling in Solar Coronal Loops

Catastrophic Cooling in Solar Coronal Loops
Author:
Publisher: Cuvillier Verlag
Total Pages: 202
Release: 2005-08-29
Genre: Science
ISBN: 3736915691

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Satellitenbeobachtungen mit hoher räumlicher und zeitlicher Auflösung zeigen die dynamische Natur der Sonnenkorona und ermöglichen uns, physikalische Prozesse in der äußeren Atmosphäre der Sonne mit großer Genauigkeit zu untersuchen. Die vorliegende Arbeit beschäftigt sich mit dynamischen Prozessen in koronalen Bögen, d.h. magnetischen Strukturen, die einen wichtigen Bestandteil der Sonnenkorona bilden. Zeitabhängige numerische Modelle koronaler Bögen werden berechnet, um die folgenden Fragen zu beantworten: Verlangen dynamische Prozesse in koronalen Bögen, wie z.B. Strömungen und kurzzeitige Helligkeitsvariationen, notwendigerweise nach einem externen Antriebsmechanismus? Können unterschiedliche Beobachtungen von schnellen Abströmungen in koronalen Bögen mit einem einzigen Mechanismus erklärt werden? Welche Parameter bestimmen die Dynamik koronaler Bögen?

Magnetic Origins of Cool Plasma in the Sun's Corona

Magnetic Origins of Cool Plasma in the Sun's Corona
Author: Emily Irene Mason
Publisher:
Total Pages: 159
Release: 2020
Genre: Coronal rain
ISBN:

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Much of solar physics research focuses on two questions: how the corona's temperature becomes hundreds of times hotter than the surface, and how the slow solar wind forms. Among the most fascinating phenomena produced by coronal heating is coronal rain, in which plasma undergoes rapid cooling (from roughly 106 to 103 K), condenses, and falls to the surface. One proposed rain origin theory, thermal nonequilibrium (TNE), posits a height restriction in coronal heating. By studying condensations, physicists hope to better understand coronal heating.Solar wind is often subdivided into fast and slow wind. The former originates in coronal hole regions; slow wind's source, however, is still under debate. One leading theory postulates that it comes from coronal hole boundaries, where magnetic field lines frequently reconnect.This dissertation investigates the origins and dynamics of coronal rain via study of recently-discovered structures called raining null-point topologies, or RNPTs. RNPTs - the first identification and characterization of which comprise part of this work - are decaying active regions situated near coronal hole boundaries, between 50-150 Mm in height. They are host to long periods of continuous coronal rain formation, and provide insight into coronal heating, slow solar wind origins, and coronal dynamics. This dissertation poses the following science questions:1. What specific mechanisms power the coronal rain and dynamics in RNPTs?2. What do these structures and the rain they contain tell us about the fundamental mechanisms of coronal heating?3. What do these structures and the rain they contain tell us about the fundamental origins and mechanisms of the slow solar wind?First, we focus on identifying and analyzing RNPTs' observational characteristics. We process and analyze RNPT data using both the Solar Dynamics Observatory Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager. Potential field source-surface extrapolations that model the magnetic field in the corona aid in the interpretation of the structures' topology. Next, we conduct a heating regime parameter study of 1D hydrodynamic simulations using the HYDrodynamic and RADiation Code (HYDRAD). This models a single flux tube that approaches the null, producing large asymmetry and a drastic cross-sectional expansion near the loop apex.Results indicate that RNPTs experience two rain-forming mechanisms, thermal nonequilibrium and interchange reconnection. The interchange reconnection is posited to power much of the early bursts of coronal rain, which constitutes a new rain-formation mechanism and allows for plasma from closed loops to escape into the slow solar wind. Observations also show evidence of partial condensations, which condense but do not fully cool. The results of the modeling study imply that heating scale heights in RNPTs must be much lower than in symmetric loops in order to support the observed TNE cycles. They also show that the apex's large expansion introduces a reverse siphon flow and suppresses condensations. The simulations show significant decreases in density near the apex and warm condensations, in good agreement with the observations. This two- pronged approach produces a broad yet detailed study of RNPT dynamics.