Wavy Current Sheet Research Articles

A new calculation of the cosmic-ray antiproton spectrum in the Galaxy and heliospheric modulation effects on this spectrum using a drift plus wavy current sheet model

The expected interstellar antiproton spectrum arising from cosmic-ray interactions in the Galaxy is recalculated, and the modulation of both antiprotons and protons is calculated using a two-dimensional modulation model incorporating gradient and curvature drifts and a wavy current sheet as well as the usual diffusion, convection, and energy-loss effects. Significant differences in the antiproton/proton ratio for different solar magnetic field polarities are predicted as well as a 'low-energy' component for antiprotons below about 1 GeV.

Interplanetary cosmic ray latitudinal gradient in 1984 to 1987 using IMP 8 and Voyager data

We have used the cosmic ray particle measurements for E > 70 MeV from the Voyager 1 and 2 and IMP 8 detectors together with observations of the tilt of the heliospheric current sheet to determine the latitudinal gradient in 1984–1987 by a new method. We find that the cosmic ray intensity decreases with heliographic latitude and the changing latitudinal gradient observed during this time period can be directly attributed to the changes in the tilt of current sheet. For a radial gradient of 2.0%/AU between IMP 8 and Voyager 2 near the heliographic equator, the latitude gradient varies from ∼ −1.5%/deg to ∼ −0.9%/deg as the current sheet tilt decreases, and the latitudinal gradient that would be measured for a tilt of 0° is −1.5%/deg or −3.3%/AU. This is larger in magnitude than the radial gradient of 2.0%/AU existing at this time. The different methods used to determine the latitudinal gradient are discussed. The measured latitudinal gradients are then compared with the predictions of the drift models for cosmic ray propagation and the effects of the latitudinal variation of the solar wind upon cosmic rays. The measured gradients are generally much larger than predicted, especially in the case of the drift models. In all cases there is an important distinction between the measured average 26‐day gradient and the instantaneous or daily average gradient. The 26‐day variations of intensity seen at Voyager 1 during the period 1984–1987 are much smaller and more irregular than the predicted variations due to the wavy current sheet. It appears that neither the effects of drifts nor of the solar wind speed variations as a function of distance from the current sheet can fully explain the features of the latitudinal gradient reported here.

The three-dimensional geometry of the heliospheric current sheet

The three-dimensional geometry of the heliospheric current sheet seen from fixed points in interplanetary space is constructed for idealized (sinusoidal) magnetic neutral lines (equators) and for an observed magnetic equator on the basis of the “kinematic method” developed by Hakamada and Akasofu (1982). The cross-sections of the wavy current sheet at distances 1, 2 and 5 a.u. are also constructed for the idealized magnetic neutral lines.

Cosmic rays near the heliospheric current sheet

We present a discussion of full, three‐dimensional model simulations of the solar modulation of galactic cosmic rays, including drift. Our particular emphasis is on the variation of the cosmic‐ray intensity near the heliospheric current sheet. We show that the model quite naturally produces a negative gradient away from a wavy current sheet as seen by an observer on the Earth. We conclude that recent observations of Newkirk and Lockwood are not in conflict with these model results, and hence are consistent with modulation models in which drift plays an important role.