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3 edition of Acoustic and magnetic heating of chromospheres/coronae found in the catalog.

Acoustic and magnetic heating of chromospheres/coronae

Dermott J. Mullan

Acoustic and magnetic heating of chromospheres/coronae

are there distinct signatures? : final technical report for grant NAG 5 3046

by Dermott J. Mullan

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  • 28 Currently reading

Published by National Aeronautics and Space Administration, National Technical Information Service, distributor in [Washington, DC, Springfield, Va .
Written in English

    Subjects:
  • Atmosphearic heating.,
  • Chromosphere.,
  • Magnetic fields.,
  • Acoustic propagation.,
  • Acoustic properties.,
  • Signatures.,
  • Coronas.,
  • Mathematical models.,
  • Hydrodynamic equations.

  • Edition Notes

    Other titlesAre there distinct signatures?
    Statement[principal investigator], D.J. Mullan.
    Series[NASA contractor report] -- 205855., NASA contractor report -- NASA CR-205855.
    ContributionsUnited States. National Aeronautics and Space Administration.
    The Physical Object
    FormatMicroform
    Pagination1 v.
    ID Numbers
    Open LibraryOL15491539M

    The heating of solar and stellar chromospheres and coronae are one of the key fun-damental and yet unresolved questions of modern space and plasma ://   Heating ofChromosphere, and Coronae 3 where T is the temperature and p the density. As the entropy in the gas element (moving in a wind with velocity v) is conserved, one has in the laboratory (Euler) frame aats as dS I asI dS I dS I dS I +vaz = dt R + dt J + dt e+ dt v + dt M (2) Heretistime and z isthe height inaplane-parallel atmosphere. The ~ulm/papers/

      Formation of Chromospheres and Coronae of Accretion Disks by Viscous Dissipation.- 3: Wave Heating Mechanisms.- Acoustic Heating.- On the Intrinsic Difficulty of Producing Stellar Coronae With Acoustic Waves.- The Effect of Waves on Optically Thin Transition Region Lines.- Heating of the Solar Atmosphere by Spicules.- Nonlinear Pulse Cool Stars, Stellar Systems, and the Sun por Jeffrey L. Linsky, , disponible en Book Depository con envío ://

      unobservable. Other arguments against acoustic heating of stellar coronae rely on the extremely complex coronal topology inferred from solar obser-vations, which can directly be linked to magnetic structures and can barely be reproduced by pure nonmagnetic heating. On the other hand, evidence is now available that acoustic heating might   chromospheres, transition regions and coronae are common tostars throughoutthe HR diagram. What is more significant is that these observations have demonstrated that magnetic fields playafundamental role in the heating of outer stellar atmospheres and that the observed emission levels are in strong qualitative and quantitative disagreement with the


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Acoustic and magnetic heating of chromospheres/coronae by Dermott J. Mullan Download PDF EPUB FB2

HEATING OF CHROMOSPHERES AND CORONAE P. ULMSCHNEIDER Institut [iir Theoretische Astrophysik, Universitiit Heidelberg, Ticrqaricnstr. 15, D Heidelberq, Germany e-mail:[email protected] \Abstract. Almost all nondegenerate stars have chromospheres and coronae.

These hot outer layers are produced by mechanical ~ulm/papers/   Chromospheres and coronae owe their existence to mechanical heating. In the present work the mechanisms which are thought to provide steady mechanical heating are reviewed.

These mechanisms can be classified as hydrodynamical - and magnetic heating mechanisms and each of these can be subdivided further on basis of the fluctuation :// The heating mechanisms of chromospheres and coronae, classified as hydrodynamic and magnetic mechanisms, are reviewed here.

Both types of mechanisms can be further subdivided on basis of the fluctuation frequency into acoustic and pulsational waves for hydrodynamic and into AC- and DC-mechanisms for magnetic :// Almost all nondegenerate statrs have chromospheres and coronae.

These hot outer layers are produced by mechanical heating. The heating mechanisms of chromospheres and coronae, classified as hydrodynamic and magnetic mechanism, are reviewed here.

Both types of mechanisms can be further subdivided on basis of the fluctuation frequency into acoustic and pulsational waves for hydrodynamic Get this from a library. Acoustic and magnetic heating of chromospheres/coronae: are there distinct signatures?: final technical report for grant NAG 5 [Dermott J Mullan; United States.

National Aeronautics and Space Administration.] Chromospheres and coronae are layers which are dominated by mechanical heating and usually by magnetic fields. The heating of chromospheres can be explained by an ordered sequence of different /_The_Physics_of_Chromospheres_and_Coronae.

Acoustic wave dissipation is a viable mechanism for the heating of chromospheres and coronae. In absence of magnetic fields in the center of supergranulation cells on the sun and on very slowly rotating stars the acoustic heating mechanism appears to dominate.

In the solar chromospheric network and on moderately or rapidly rotating stars acoustic heating is a weak background :// Chromospheres and coronae are layers which are dominated by mechanical heating and usually by magnetic fields. The heating of chromospheres can be explained by an ordered sequence of different processes which systematically vary as function of height in the star and with the speed of its rotation.

It seems now pretty certain that acoustic waves U/abstract. The heating of chromospheres can be explained by an ordered sequence of different processes which systematically vary as function of height in the star and with the speed of its rotation.

It seems now pretty certain that acoustic waves heat the low and middle chromosphere, and MHD waves the magnetic regions up to the high :// Heating of stellar chromospheres and coronae: Evidence for non-magnetic heating. Authors; Authors and affiliations The associated heating mechanism may be dissipation of acoustic waves.

The temperatures of the basal part of the atmosphere are limited to a few tens of thousands of degrees or less in G- and K-type stars. Schrijver C.J Recent evidence is summarized that suggests that neither of two traditional views of chromospheric heating (that the flux of energy required to heat the solar chromosphere) is only a small fraction of the total radiative energy emerging from the solar interior and that chromospheres are heated by acoustic waves generated in the convection zone (which lies close to the surface of the star) is 14 73M/abstract.

1. Chromospheres, coronae and the heating problem One of the basic problems in astrophysics is to identify the heating mechanisms of chromospheres and coronae.

In the reviews by Narain & Ulmschneider (, ), Ulmschneider (), Ulmschneider & Musielak () it is shown that there are a large number of di erent heating mechanisms that ~ulm/ The acoustic heating mechanism seems to be dominant in all nonmagnetic nonpulsating late-type stars.

Heating of stellar chromospheres and coronae: Evidence for non-magnetic heating Abstract. Chromospheres consist of magnetic and non-magnetic areas, which are heated by different mechanisms. For the non-magnetic areas a satisfactory acoustic wave heating picture emerges, where the wave generation calculations, the solar wave observations, the solar acoustic heating calculations and the solar chromospheric cooling observations are all roughly :// Abstract.

In a qualitative sense, the heating of chromospheres and coronae has long been ascribed to either acoustic or magnetic heating.

However, quantitative discussions of the energy balance with detailed comparison to the fluxes of chromospheric emission lines have begun to appear only :// Stars in the spectral range from late A to mid F have convection zones which are thought to be too shallow to allow for efficient dynamo operation.

As a result, such stars almost certainly do not rely on magnetic processes to heat their chromospheres and coronae. And yet there is evidence that chromospheres and coronae are present in these stars. This suggests the presence of non-magnetic 29M/abstract.

The corrected acoustic wave energy fluxes have already been used by Buchholz, Ulmschneider, & Cuntz () to predict theoretically the "basal heating" in late-type dwarfs and giants (see Fifth Goal).

We have also completed our analytical and numerical investigations of the generation of magnetic flux tube waves in stellar convection ://   1. Chromospheres, coronae and the heating problem 2. Acoustic wave energy flux calculations 3. Theoretical chromosphere models based on acoustic heating 4.

Comparison with chromospheric observations 5. Magnetohydrodynamic wave energy generation 6. Magnetic chromospheres 7. Problems with wave observations on the Sun 8.

Problems with the acoustic ~ulm/ In a qualitative sense, the heating of chromospheres and coronae has long been ascribed to either acoustic or magnetic heating.

However, quantitative discussions of the energy balance with   chromospheres and coronae, the sources of stellar radio, UV and X-ray emission, andstellarwindsremains inadismal state. The principal reason for this is that the fundamental physical process - the mechanical heating mechanism, whichisthecauseof theseimportant stellarlayers - isstilllargely unknown, an andB.

Edlendiscovered ~ulm/papers/. Specific issues addressed include theories regarding the acoustic and magnetic heating of stellar chromospheres and coronae, stellar granulation, wave heating in magnetic flux tubes, observations of the solar Ca-II lines, longitudinal-transverse magnetic tube waves in the solar atmosphere, radio emission from rapidly rotating cool giant stars Chromospheres, coronae, and winds similar to those observed on the Sun have been detected in a variety of cool stars.

In many cases, especially for main-sequence stars, there is good evidence that Abstract. Recent evidence is summarized that suggests that neither of two traditional views of chromospheric heating (that the flux of energy required to heat the solar chromosphere) is only a small fraction of the total radiative energy emerging from the solar interior and that chromospheres are heated by acoustic waves generated in the convection zone (which lies close to the surface of the