Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Alfvénicity of fluctuations associated with the Kelvin–Helmholtz instability (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 2995-3003 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The velocity shear which exists between three layers in an ideal plasma is studied. This configuration is modeled as a jet (or, strictly speaking, a wake) embedded in a uniform medium using a magnetohydrodynamics (MHD) code developed for astrophysical jet simulations. Weak and strong magnetic fields are considered both inside and outside the jet with a shear Mach number of 6. The shear can be Kelvin–Helmholtz (KH) unstable and evolve into a new less sheared pattern. There exists extensive literature on the KH instability which is extended by quantitatively describing the MHD properties of the fluctuations associated with the instability. To do so, a time series analysis of the fluctuations at various points inside and adjacent to the jet is performed. Specifically, points either in the center of the jet or just outside the transition layer—the initial location of the shear layer are considered. In the nonlinear stage, the perturbation is found to be a sum of the fast magnetosonic mode, slow magnetosonic mode, and the Alfvén component. To quantitatively evaluate the fluctuations, the normalized cross-helicity and Elsässer ratios are calculated, which in turn measure the degree of Alfvénicity. Fully nonlinear fluctuations are found to be more Alfvénic than magnetosonic in the low β case (β(approximate)0.833) as compared with high β case (β(approximate)13.3). This is in contrast to linear modes generated by the KH instability, which are magnetosonic modes. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874151
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Probing the local interstellar medium (1985)
    [s.l.] : Nature Publishing Group
    Nature 317 (1985), S. 702-703 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] As the solar wind flows into the LISM, it undergoes a transition to subsonic flow and then expands until it is dispersed within the LISM. Using Voyager data, Kurth et al.1 reported on 2-3-kHz radio emission at 18 AU, which they suggest is radiation at the second harmonic of the plasma frequency at ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/317702a0
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Coronal Heating by Magnetic Explosions (1999)
    Springer
    Space science reviews 87 (1999), S. 283-286 
    Details
    ISSN: 1572-9672
    Keywords: coronal heating ; magnetic field ; magnetic shear ; magnetic explosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract From magnetic fields and coronal heating observed in flares, active regions, quiet regions, and coronal holes, we propose that exploding sheared core magnetic fields are the drivers of most of the dynamics and heating of the solar atmosphere, ranging from the largest and most powerful coronal mass ejections and flares, to the vigorous microflaring and coronal heating in active regions, to a multitude of fine-scale explosive events in the magnetic network, driving microflares, spicules, global coronal heating, and, consequently, the solar wind.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005129424649
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    The Solar Wind - Inner Heliosphere (1998)
    Springer
    Space science reviews 83 (1998), S. 75-86 
    Details
    ISSN: 1572-9672
    Keywords: Solar wind ; Heliosphere ; Ulysses ; SOHO ; MHD waves ; Turbulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The solar wind in the inner heliosphere, inside ~ 5 AU, has been almost fully characterized by the addition of the high heliographic latitude Ulysses mission to the many low latitude inner heliosphere missions that preceded it. The two major omissions are the high latitude solar wind at solar maximum, which will be measured during the second Ulysses polar passages, and the solar wind near the Sun, which could be analyzed by a Solar Probe mission. Here, existing knowledge of the global solar wind in the inner heliosphere is summarized in the context of the new results from Ulysses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005069328058
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Magnetohydrodynamic simulation of a streamer beside a realistic coronal hole (1994)
    Springer
    Space science reviews 70 (1994), S. 295-298 
    Details
    ISSN: 1572-9672
    Keywords: Streamers ; Coronal Holes ; MHD Simulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Existing models of coronal streamers establish their credibility and act as the initial state for transients. The models have produced satisfactory streamer simulations, but unsatisfactory coronal hole simulations. This is a consequence of the character of the models and the boundary conditions. The models all have higher densities in the magnetically open regions than occur in coronal holes (Noci,et al., 1993).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00777883
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Ulysses-UVCS Coordinated Observations (1999)
    Springer
    Space science reviews 87 (1999), S. 319-322 
    Details
    ISSN: 1572-9672
    Keywords: SOHO ; Ulysses ; streamers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present results from SOHO/UVCS measurements of the density and flow speed of plasma at the Sun and again of the same plasma by Ulysses/SWOOPS in the solar wind. UVCS made measurements at 3.5 and 4.5 solar radii and Ulysses was at 5.1 AU. Data were taken for nearly 2 weeks in May–June 1997 at 9–10 degrees north of the equator in the streamer belt on the east limb. Density and flow speed were compared to see if near Sun characteristics are preserved in the interplanetary medium. By chance, Ulysses was at the very northern edge of the streamer belt. Nevertheless, no evidence was found of fast wind or mixing of slow wind with fast wind coming from the northern polar coronal hole. The morphology of the streamer belt was similar at the beginning and end of the observing period, but was markedly different during the middle of the period. A corresponding change in density (but not flow speed) was noted at Ulysses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005197812354
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Streamer Evaporation (1999)
    Springer
    Space science reviews 87 (1999), S. 323-326 
    Details
    ISSN: 1572-9672
    Keywords: corona ; streamers ; magnetohydrodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Streamer evaporation is the consequence of heating in ideal MHD models because plasma is weakly contained by the magnetic field. Heating causes inflation, opening of field lines, and release of solar wind. It was discovered in simulations and, due to the absence of loss mechanisms, the ultimate end point is the complete evaporation of the streamer. Of course streamers do not behave in this way because of losses by thermal conduction and radiation. Heating is also expected to depend on ambient conditions. We use a global MHD model with thermal conduction to examine the effect of changing the heating scale height. We also extend an analytic model of streamers developed by Pneuman (1968) to show that steady streamers are unable to contain plasma for temperatures near the cusp greater than ∼ 2 × 106 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005149929192
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Response of earth and venus ionospheres to corotating solar wind stream of 3 July 1979 (1985)
    Springer
    Earth, moon and planets 32 (1985), S. 275-290 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Corotating solar wind streams emanating from stable coronal structures provide an unique opportunity to compare the response of planetary ionospheres to the energy conveyed in the streams. For recurrent solar conditions the “signal” propagating outward along spiral paths in interplanetary space can at times exhibit rather similar content at quite different downstream locations in the ecliptic plane. Using solar wind measurements from plasma detectors on ISEE-3, Pioneer Venus Orbiter (PVO) and Helios-A, as well as in-situ ion composition measurements from Bennett Ion Mass Spectrometers on the Atmosphere Explorer-E and PVO spacecraft, corotating stream interactions are examined at Earth and Venus. During May–July 1979 a sequence of distinct, recurrent coronal regions developed at the Sun. Analysis of these regions and the associated solar wind characteristics indicates a corrresponding sequence of corotating streams, identifiable over wide distances. The time series of solar wind velocity variations observed at Earth, Venus, and the Helios-A positions during June–July attests to intervals of corotating stream propagation. The characteristics of the stream which passed Earth on July 3, are observed at Helios-A and at Venus (PVO) about 8 days later, consistent with the spiral path propagation delay times between the locations in the ecliptic plane. On July 3, Earth and Venus have a wide azimuthal separation of about 142
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00054217
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Numerical modeling of coronal mass ejections based on various pre-event model atmospheres (1995)
    Springer
    Solar physics 161 (1995), S. 365-381 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We examine how the initial state (pre-event corona) affects the numerical MHD simulation for a coronal mass ejection (CME). Earlier simulations based on a pre-event corona with a homogeneous density and temperature distribution at the lower boundary (i.e., solar surface) have been used to analyze the role of streamer properties in determining the characteristics of loop-like transients. The present paper extends these studies to show how a broader class of global coronal properties leads not only to different types of CMEs, but also modifies the adjacent quiet corona and/or coronal holes. We consider four pre-event coronal cases: (1) constant boundary conditions and a polytropic gas with γ = 1.05; (2) non-constant (latitude dependent) boundary conditions and a polytropic gas with γ = 1.05; (3) constant boundary conditions with a volumetric energy source and γ = 1.67; (4) non-constant (latitude dependent) boundary conditions with a volumetric energy source and γ = 1.67. In all models, the pre-event magnetic fields separate the corona into closed field regions (streamers) and open field regions. The CME's initiation is simulated by introducing at the base of the corona, within the streamer region, a standard pressure pulse and velocity change. Boundary values are determined using MHD characteristic theory. The simulations show how different CMEs, including loop-like transients, clouds and bright rays, might occur. There are significant new features in comparison to published results. We conclude that the pre-event corona is a crucial factor in dictating CMEs properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00732075
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Planetary waves on the Sun? (1971)
    Springer
    Solar physics 18 (1971), S. 172-175 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Some recent observations of the Sun suggest a class of wave-like motions moving both eastward and westward at a uniform velocity with respect to the mean solar angular velocity. It is suggested that these may be hydromagnetic planetary waves. An estimate of the mean toroidal magnetic field is made, based on a theoretical treatment of such waves already in the literature, and a slight correction to the mean rate of rotation of the Sun is inferred.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146042
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...