Influence of solar wind structure on cosmic ray modulation during epochs of alternate solar magnetic polarity

Abstract. The interest in the role of the solar wind termination shock and heliosheath in cosmic ray modulation studies has increased significantly as the Voyager 1 and 2 spacecraft approach the estimated position of the solar wind termination shock. The effect of the solar wind termination shock on charge-sign dependent modulation, as is experienced by galactic cosmic ray Helium (He++) and anomalous Helium (He+), is the main topic of this work, and is complementary to the previous work on protons, anti-protons, electrons, and positrons. The modulation of galactic and anomalous Helium is studied with a numerical model including a more fundamental and comprehensive set of diffusion coefficients, a solar wind termination shock with diffusive shock acceleration, a heliosheath and particle drifts. The model allows a comparison of modulation with and without a solar wind termination shock and is applicable to a number of cosmic ray species during both magnetic polarity cycles of the Sun. The modulation of Helium, including an anomalous component, is also done to establish charge-sign dependence at low energies. We found that the heliosheath is important for cosmic ray modulation and that its effect on modulation is very similar for protons and Helium. The local Helium interstellar spectrum may not be known at energies

Download Full-text

The Long Term Cosmic Ray Variation Relevant to Solar Wind Structure in the Outer Heliosphere

Physics of the Outer Heliosphere - COSPAR Colloquia Series ◽

10.1016/b978-0-08-040780-7.50036-1 ◽

1990 ◽

pp. 199-203

Author(s):

M.V. Alania ◽

R.G. Aslamazashvili ◽

T.B. Bochorishvili ◽

L.I. Dorman ◽

R.T. Guschina ◽

...

Keyword(s):

Solar Wind ◽

Cosmic Ray ◽

Outer Heliosphere ◽

Wind Structure ◽

Solar Wind Structure

Download Full-text

Empirical inner boundary conditions and rotation rates for solar wind models

10.5194/egusphere-egu21-782 ◽

2021 ◽

Author(s):

Huw Morgan

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Boundary Conditions ◽

Coronal Magnetic Field ◽

Height Range ◽

Rotation Rates ◽

Wind Structure ◽

Solar Wind Structure ◽

Coronal Electron ◽

Made In

<p>To date, the inner boundary conditions for solar wind models are either directly or indirectly based on magnetic field extrapolation models of the photosphere. Furthermore, between the photosphere and Earth, there are no other direct empirical constraints on models. New breakthroughs in coronal rotation tomography, applied to coronagraph observations, allow maps of the coronal electron density to be made in the heliocentric height range 4-12 solar radii (Rs). We show that these maps (i) give a new empirical boundary condition for solar wind structure at a height where the coronal magnetic field has become radial, thus avoiding the need to model the complex inner coronal magnetic field, and (ii) give accurate rotation rates for the corona, of crucial importance to the accuracy of solar wind models and forecasts.</p>

Download Full-text

Solar cycle changes of large-scale solar wind structure

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309992912 ◽

2009 ◽

Vol 5 (S264) ◽

pp. 356-358 ◽

Cited By ~ 3

Author(s):

P. K. Manoharan

Keyword(s):

Solar Wind ◽

Solar Cycle ◽

Large Scale ◽

Interplanetary Space ◽

The Sun ◽

Wind Structure ◽

Level Of Activity ◽

Solar Wind Structure ◽

Current Minimum ◽

Inner Heliosphere

AbstractIn this paper, I present the results on large-scale evolution of density turbulence of solar wind in the inner heliosphere during 1985–2009. At a given distance from the Sun, the density turbulence is maximum around the maximum phase of the solar cycle and it reduces to ~70%, near the minimum phase. However, in the current minimum of solar activity, the level of turbulence has gradually decreased, starting from the year 2005, to the present level of ~30%. These results suggest that the source of solar wind changes globally, with the important implication that the supply of mass and energy from the Sun to the interplanetary space has significantly reduced in the present low level of activity.

Download Full-text

Galactic cosmic-ray modulation effect by solar-wind streams

Canadian Journal of Physics ◽

10.1139/p95-094 ◽

1995 ◽

Vol 73 (9-10) ◽

pp. 642-646 ◽

Cited By ~ 3

Author(s):

M. A. El-Borie

Keyword(s):

Solar Wind ◽

Wind Speed ◽

Cosmic Rays ◽

Solar Wind Speed ◽

Cosmic Ray ◽

Diurnal Variations ◽

Solar Cycles ◽

Mean Values ◽

Wind Speeds ◽

Cosmic Ray Modulation

Data, from the worldwide network of neutron monitors, recorded at Deep River, Hermanus, Rome, Tokyo, and Huancayo, over two solar cycles (Nos. 20 and 21) are analyzed to study the long-term variations of the solar diurnal variations as they relate to solar-wind speed. The median primary rigidities of response (Rm) for these detectors cover the range 16 GV ≤ Rm ≤ 33 GV. We discuss the solar diurnal variations (amplitude and phase) of cosmic rays as a function of solar activity. The behavior of solar diurnal phases is completely different for the two epochs of high-wind speed. Data of solar-wind speed from 1966–1986 are classified according to the state of the daily mean values. Variation in the amplitudes of the diurnal variations, as functions of the median primary rigidity of cosmic rays, for the two selected periods (1973–1975 and 1979–1981) of high and low solar-wind speeds were determined at the selected stations. The rigidity dependence of the averaged solar diurnal variations of cosmic rays related to the high solar-wind speed was studied. The most sensitive rigidity of modulation is around 20 and 30 GV during the 1973–1975 and 1979–1981 periods, respectively. Our results also show that there is a significant correlation in the solar diurnal amplitudes between the two divisions of high and low solar-wind speed days.

Download Full-text