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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 103, NO. A5, PAGES 9545–9551, 1998

Particle propagation channel detected at 4.7 AU inside a corotating interaction region

D. Maia

Observatoire Paris Meudon, DASOP, URA 1756 CNRS, Meudon, France

O. Malandraki

Demokritos University of Thrace, Department of Electrical Engineering, Xanthi, Greece

M. Pick

Observatoire Paris Meudon, DASOP, URA 1756 CNRS, Meudon, France

E. T. Sarris

Demokritos University of Thrace, Department of Electrical Engineering, Xanthi, Greece

G. Kasotakis

National Observatory of Athens, Athens, Greece

L. J. Lanzerotti

AT&T Bell Laboratories, Murray Hill, New Jersey

C. G. MacLennan

AT&T Bell Laboratories, Murray Hill, New Jersey

P. C. Trochoutsos

Demokritos University of Thrace, Department of Electrical Engineering, Xanthi, Greece

Abstract

This study presents an interplanetary particle (electrons and ions) event which was detected at 4.7 AU by the instruments on the Ulysses spacecraft inside a corotating interaction region between a fast and slow solar wind stream. A particle propagation channel is identified where the particles can propagate from the Sun nearly scatter free within a region bounded by tangential discontinuities. This channel is found to be rooted in the vicinity of a solar active region where the flare associated with the interplanetary event was produced. The ions (energy over 600 keV) detected inside this channel are shown to be of solar origin: dispersion occurs in the proton arrival time versus proton energy, there is a strong anisotropy in the proton pitch angle distribution, and a hard energy-spectrum for the protons. The electrons were already present when the spacecraft crossed the structure. The chemical composition is also indicative of a solar origin, with a decrease in the ⁴He/H (⁴He in the energy range 389–1278 keV and H in the range 480–1204 keV) abundance ratio by a factor of 2 inside the channel. Mapped back to the solar surface, the size of the propagation channel is estimated to be of the order of 30,000 km. The channel is found to be magnetically quiet, without a preferred direction for the minimum of variance.

Received 10 April 1997; accepted 3 October 1997.

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Citation: Maia, D., O. Malandraki, M. Pick, E. T. Sarris, G. Kasotakis, L. J. Lanzerotti, C. G. MacLennan, and P. C. Trochoutsos (1998), Particle propagation channel detected at 4.7 AU inside a corotating interaction region, J. Geophys. Res., 103(A5), 9545–9551.

Copyright 1998 by the American Geophysical Union.