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ARMSTRONG, T. and CHOO, T. (U. Kansas, USA). SARRIS,E.(Dernocritos U., Thrace, Greece). SIMNETT, G. (U.Birmingham, UK). ROELOF, E. (Johns Hopkins U./APL, USA)Ion and Electron Anigotropies During the March 23, 15:43UT Shock Observed at Ulysses

The HiScale instrument aboard Ulysses observes ion and electronangular distributions in 4 or 8 angular sectors as the spacecraftspins. Two 8 sector and two 4 sector measurements cover nearlyall possible arrival directions within one or two spacecraftrevolutions (12 or 24 seconds). The energies observed range fromabout 30 ReV to about 5 MeV spanning the interval typically moststrongly affected by interplanetary shocks. Pitch angledistributions (with magnetic field direction supplied by the HEDteam, Andre Balough, P1) of the energetic ions show unidirectionalflow in the region far upstream towards the approaching shock.Closer to the shock, but still upstream, reflected ions areobserved (with the highest energies observed earliest). Withinseveral ion gyroradii of the shock nongyrotropic effects areobserved. Downstream from the shock the anisotropies peakperpendicular to the magnetic field. These characteristics areconsistent with shock drift acceleration.

BADRUDDIN (S.P. Degree College, Shohratgarh, India).Cosmic Ray Modulation by Transient and Corotating HighSpeed Streams in the Heliosphere

High speed streams detected in the solar wind plasma have beenclassified into two types, namely transient and corotatingstreams. These two types of streams are considered and modulationof cosmic rays due to these streams have been studied in detail.Observed interplanetary plasma and field parameters of thesestreams such as speed, field strength and its variance have alsobeen utilized in a systematic manner in order to see their effectsin modulating cosmic rays. The observed effects of streamsindicate that out of three parameters of streams — speed, fieldstrength and its variance — the field variance plays moreimportant role in transient cosmic ray modulation. Implicationsof these results are discussed.

CHALOV, S., (Inst. for Problems in Mechanics U.S.S.R.).The Longitudinal Distribution of Anomalous Hydrogen nearthe Solar Wind Termination Shock

Hydrodynamic calculations show that the solar wind terminationshock has a prolate shape. Consequently, the angle between theshock normal vector and the magnetic field lines varies with thevariation of longitude. Near the ecliptic the minimum speed foran upstream ion to be reflected by the shock, or for a downstreamion to overtake the shock decreases on the shock flanks. If thisreflected ions constitute a seed population for a first orderFermi acceleration, then the injection process will be mostefficient on the flanks of the termination shock. We show thatthe injection efficiency falls off steeply near the nose of thetermination shock in the case of pick-up hydrogen. Thelongitudinal gradients of anomalous hydrogren along thetermination shock are calculated.

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