ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

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
    facet.materialart.
    Unknown
    The effect of the heliospheric current sheet on cosmic ray intensities at solar maximum - Two alternative hypotheses (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The capabilities of two alternative models for accounting for the reversal of the solar magnetic field polarity at the point of solar maximum and for the associated modulation of cosmic ray intensities at 1 AU are assessed. One model posits a continuous increase in the inclination of the heliospheric current sheet to a point of verticality at maximum, when it overturns and the reversal occurs. The alternative view is that the sun sheds the magnetic field of the previous cycle and generates a new field of opposite polarity. Some data do exist for a tilted current sheet which increases its tilt with proximity to the solar maximum. However, coronal data also support the presence of isolated regions of anomalous polarity which spread over the surface of the sun as maximum approaches, a condition commensurate with flux shedding. Both models predict heliospheric current sheet configurations which would produce some cosmic ray modulations observed over the course of the solar cycle.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 91; 2889-289
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 2
    facet.materialart.
    Unknown
    Latitudinal extent of the heliospheric current sheet and modulation of galactic cosmic rays (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Possible correlations were investigated between the modulation of galactic cosmic rays and changes in the maximum heliographic latitude of the heliospheric current sheet during solar maximum. Solar photospheric magnetic field data from 1976-82 were extrapolated by means of potential theory to obtain the maximum latitudinal extent of the current sheet in the northern and southern hemispheres. The latitudinal differences were compared with terrestrial neutron flux data and Pioneer 10 data on cosmic rays with energies below 200 MeV at heliocentric distances of 10-30 AU. Account was taken for the time delay for the solar wind to propagate out to the spacecraft location. The current sheet maxima were nearly symmetrical about the solar equator except during sunspot maxima, when the solar poles were reversing. Significant changes in the latitudinal symmetry were highly correlated with the neutron data and cosmic fluctuations at Pioneer 10. The sensitivity of cosmic rays to the polarity reversals is in accordance with predictions of the gradient drift model.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 91; 2933-294
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 3
    facet.materialart.
    Unknown
    The effect of corotating interaction regions on the propagation of relativistic cosmic rays in the heliosphere (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: This paper questions the validity of modulation theories that ignore the presence of large regions of enhanced magnetic field in the heliosphere. The scatter-free and diffusive motion of relativistic cosmic rays is simulated in models of the heliospheric magnetic field, which include compressed field structures representing the corotating interaction regions that are believed to be present in the interplanetary medium throughout most of the solar cycle. It is found that the strong field gradients associated with these regions greatly perturb the drift pattern anticipated for simple Parkerian fields, and thus the expected streaming of cosmic rays from over the poles or along the current sheet, during consecutive solar cycles, no longer holds.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 87; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 4
    facet.materialart.
    Unknown
    Changes in cosmic ray propagation induced by corotating interaction regions (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: By simulating the trajectories for scatter free and diffusive propagation of relativistic cosmic rays in a model of the heliospheric magnetic fields containing a representation of corotating interaction regions (CIR's), it is found that, due to the large gradients associated with these compression regions, the motion is strongly affected and differs substantially from the predictions of current modulation theory. For positive (outward) northern hemisphere polarity, particles do not stream purely from high latitudes but can come from almost any latitude in the outer heliosphere; for negative polarity, many particles come along the current sheet (as predicted) but a second, equally important, population exists comprising particles that do not start on the current sheet but are brought to low latitudes by their interaction with CIR's. Thus, it is concluded that CIR's (and other large scale structures) cannot be ignored in analyses of cosmic ray modulation.
    Keywords: SPACE RADIATION
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
    Unknown
    Effects of drift on the transport of cosmic rays. IV - Modulation by a wavy interplanetary current sheet (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The effect of a wavy interplanetary current sheet on the solar modulation of galactic cosmic rays is studied. A simple model of the heliospheric magnetic field is employed in which there is an Archimedean spiral magnetic field directed in one direction above the current sheet and another direction below. The current sheet itself is taken to be the extension by the solar wind of a surface that, at the sun, is a plane inclined at an angle alpha to the solar equator. Two magnetic sectors will therefore be seen by an observer within an angle alpha of the heliographic equator. A simple approximate model is used to investigate modulation. As the tilt angle alpha is increased from zero, it is found that the cosmic-ray intensity decreases. For reasonable variation of alpha from approximately 10 deg to approximately 30 deg, the change in intensity can be compared to that observed as one goes from solar minimum to solar maximum. It is concluded that changes in the waviness of the interplanetary current sheet can have an important, and perhaps dominant, effect in producing solar modulation of galactic cosmic rays.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 243
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 6
    facet.materialart.
    Unknown
    the role of shock waves in modulation of galactic cosmic rays (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The understanding of modulation of the galactic cosmic rays has considerably progressed by the exploration by space probes of major heliospheric structures, such as the Corotating Interaction Regions, the neutral sheet, and the compression regions of intense heliospheric magnetic fields. Also relevant in this context were the detections in the outer heliosphere of long lasting Forbush type decreases of cosmic ray intensity. The results of recent theoretical studies on the changes in intensity and energy, at different location from the Sun, induced by the passage of shocks across the heliosphere are presented. In this version of the research, the simplest cases of modulation of uGV and 2GV particles by single or several shocks during periods of positive and negative solar field polarity are reviewed. The results of the theoretical aspects of the search is reported. The comparison of the theoretical predictions with space probe data allows conclusions to be drawn on the role of shocks on the modulation on both the 11 and 22 year galactic cosmic ray cycles in the outer heliosphere and on the plausibility of the models and parameters used.
    Keywords: SPACE RADIATION
    Type: SH-4.1-7 , 19th Intern. Cosmic Ray Conf - Vol. 4; p 384-387; NASA-CP-2376-VOL-4
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 7
    facet.materialart.
    Unknown
    Solar-flare-induced Forbush decreases - Dependence on shock wave geometry (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: It is argued that the principal mechanism for the association of Forbush decreases with the passage of a solar flare shock wave is prolonged containment of cosmic ray particles behind the flare compression region, which acts as a semipermeable obstacle to particle motion along the field lines, leading to additional adiabatic cooling of the particles. Liouville's theorem is used to calculate the instantaneous distribution function at 1 AU for each particle arriving at the earth. By averaging over a large number of individual estimates, a representative estimate of the omnidirectional phase space density and the corresponding particle intensity is obtained. The energy change of individual particles at the shocks is found to be small in comparison to the energy lost by adiabatic cooling of the cosmic rays between the shock wave and the sun. The effects of particle rigidity, diffusion coefficient, and flare longitude on the magnitude of the Forbush decrease are quantitatively investigated.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 2991-299
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 8
    facet.materialart.
    Unknown
    A theoretical interpretation of Forbush decreases (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An analysis is presented of the intensity variations of relativistic cosmic rays, at 1 AU, which are associated with the passage of a flare shock wave. The magnitude and time profile obtained is similar to that observed in flare-induced Forbush decreases, and the principal cause of the energy reduction is an increase in adiabatic cooling of the arriving particles due to prolonged containment behind the compressed field of the flare shock wave. The large decreases calculated for the smaller diffusion coefficients are inconsistent with observation, implying larger mean free paths than those traditionally assumed at these rigidities. The method presented may be used to study intensity variations associated with other large-scale structures of the interplanetary field, such as corotating interaction regions.
    Keywords: SPACE RADIATION
    Type: International Cosmic Ray Conference; Jul 13, 1981 - Jul 25, 1981; Paris; France
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...