Acoustic and magnetic heating of chromospheres/coronae

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

Publisher: National Aeronautics and Space Administration, Publisher: National Technical Information Service, distributor in [Washington, DC, Springfield, Va

Written in English
Published: Downloads: 638
Share This

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 LibraryOL17827025M
OCLC/WorldCa39011918

Theory predicts abundant production of high-frequency (10–50 mHz) acoustic waves in subsurface layers of the Sun1, and such waves are believed by many to constitute the dominant heating   A corona (Latin, 'crown') is an aura of plasma that surrounds the Sun and other celestial bodies. The Sun's corona extends millions of kilometres into space and is most easily seen during a total solar eclipse, but it is also observable with a word "corona" is a Latin word meaning "crown", from the Ancient Greek κορώνη (korōnē, “garland, wreath”).   "Heating of Solar and Stellar Chromospheres and Coronae by MHD Waves" Musielak, Z. E. Memorie della Societa Astvonomica Italiana, Vol (). "Heating of Solar and Stellar Chromospheres and Coronae by MHD Waves" Musielak, Z. E. Highlights in Astronomy, Ed. J. Bergeron, Volume 9 ()   Clearly the acoustic heating theory which ignores magnetic fields can only be valid for very slowly rotating stars, possibly for late-type supergiants where indeed a gravity dependence of the chromospheric emission has been found /32/ or for very late fully convective dwarf stars if these stars cannot produce or retain magnetic ://

The acoustic energy flux is taken as v 2 ρC s, where v is the velocity, ρ is the density and C s is the sound speed. At the bottom boundary, the energy flux from run one (solid black line) peaks Formation of Chromospheres and Coronae of Accretion Disks by Viscous Dissipation. Pages Wehrse, Rainer (et al.) Preview Buy Chap95 € Acoustic Heating. Pages Ulmschneider, Peter. Heating in Stochastic Magnetic  › Astronomy › Astrophysics and Astroparticles.   Recent work has concentrated on the interaction of magnetic fields, plasma and radiation in the outer , "Time-dependent effects of acoustic wave heating and molecular cooling in the outer atmosphere of Arcturus", Astron. Astrophys. , C.J.: , "Heating of stellar chromospheres and coronae: evidence for non-magnetic heat Heating of stellar chromospheres and coronae: Evidence for non-magnetic heating.- Relations between chromospheric and coronal structure, flux-flux correlations and convective zone properties.- Statistical properties of small high-velocity events in the solar transition region.-

direct magnetic heating in which the reconnection of magnetic field lines leads to a conversion of magnetic to thermal energ y, thereby removing the field lines. In the first case, acoustic waves are generated by mate-rial (convective) motions as purely mechanical phenomenon (Musielak et al. ). The change of the atmospheric proper-?doi=&rep=rep1&type=pdf.   nature of the heating mechanism remains elusive, however, although magnetic fields are thought to play a central role. Somewhat more than two years ago, the study of cool-star chromospheres and coronae gained a measure of respectability with the advent of the Inter-national Ultraviolet Explorer. For the first time, large numbers of cool   Get this from a library! Solar Phenomena in Stars and Stellar Systems: Proceedings of the NATO Advanced Study Institute held at Bonas, France, August September 5, [R -M Bonnet; Andrea K Dupree] -- This book represents the proceedings of a NATO Advanced Study Institute which was held at Bonas from August 25 till Sep tember 5, and was devoted to the study of "Solar

Acoustic and magnetic heating of chromospheres/coronae 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 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 Paper Title Page Authors: Acoustic heating of stellar chromospheres and coronae: 3: Ulmschneider, P.

Magnetic heating of stellar chromospheres and ?book_id= 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 thechromospheres, transition regions and coronae of rapidly rotat-ing stars magnetic heating mechanisms must be present.

Recent results from Doppler imaging further indicate that conglomer-ates of flux tubes may also be responsible for stellar magnetic spots, an important contribution to inhomogeneous magnetic surface structure (e.g., Solanki )?doi=&rep=rep1&type=pdf.Abstract. Acoustic and magnetoacoustic waves are among the possible candidate mechanisms that heat the upper layers of the solar atmosphere.

A weak chromospheric plage near the large solar pore NOAA was observed on Octo in the Fe i nm and Ca ii nm lines of the Interferometric Bidimemsional Spectrometer attached to the Dunn Solar ://