Interplanetary fast shocks and associated drivers observed through the 23rd solar minimum by Wind over its first 2.5 years

A list of the interplanetary shocks observed by Wind from its launch tin No v 1994) to May 1997 is presented. The magnetohydrodynamic nature of the sho cks is investigated, and the associated shock parameters and their uncertai nties are accurately computed using two techniques. These are: 1) a combina tion of the "preaveraged" magnetic-coplanarity, velocity-coplanarity, and t he Abraham-Schrauner-mixed methods, and 2) the Vinas and Scudder [1986] tec hnique for solving the nonlinear least squares Rankine-Hugoniot equations. Within acceptable limits these two techniques generally gave the same resul ts, with some exceptions. The reasons for the exceptions are discussed. The mean strength and rate of occurrence of the shocks appear to correlate wit h the solar cycle. Both showed a decrease in 1996 coincident with the time of the lowest ultraviolet solar radiance, indicative of solar minimum and t he beginning of solar cycle 23. Eighteen shocks appeared to be associated w ith corotating interaction regions (CIRs). The shock normal distribution sh owed a mean direction peaking in the ecliptic plane and with a longitude of similar to 200 degrees (GSE coordinates). Another 16 shocks were determine d to be driven by solar transients, including magnetic clouds. These had a broader distribution of normal directions than those of the CLR cases with a mean direction close to the Sun-Earth line. Eight shocks of unknown origi n had normal orientations far off the ecliptic plane. No shock propagated w ith longitude phi (n) greater than or equal to 220+/-10 degrees, i.e. again st the average Parker spiral direction. Examination of the obliquity angle theta (Bn) (i.e., between the shock normal and the upstream interplanetary magnetic field) for the full set of shocks revealed that about 58% were qua siperpendicular, and about 32% of the shocks oblique, and the rest quasi-pa rallel. Small uncertainty in the estimated angle theta (Bn) was obtained fo r about 10 shocks with magnetosonic Mach numbers between 1 and 2.