Magnetosheath for almost-aligned solar wind magneticfield and flow vectors: Wind observations across the dawnside magnetosheath at X= -12 Re

FARRUGIA, C. J.; ERKAEV, N. V.; TORBERT, R.; BIERNAT, H. K.; GRATTON, F. T.; SZABO, A.; RP LIN,; OGILVIE, K.; LEPPING, R. P.; SMITH, C. W.

Bremen

Conferencia; 38th COSPAR; 2010

COSPAR

Many approximations describe flow of solar wind past the magnetosphere. The  case of a perfectly aligned IP magnetic field, and solar wind flow vectors, can be treated exactly in MHD (Spreiter and Rizzi, 1974) We examine a case of nearly-opposed  IP field and flow vectors (within 15o). On October 24, 2001,  Wind did a 5-hour-long magnetosheath crossing close to Earth and near the ecliptic plane (Z = -0.7 Re) at X = -13 Re. We compare the predictions of the Spreiter and Rizzi theory with the Wind magnetosheath observations and find a fair agreement. We carry out a small perturbation analysis of the S&R solution to account for the small IMF components perpendicular to the flow vector. We compare with the time series of the observations, and show that a satisfactory agreement is obtained.  Various time-dependent effects in the data are not included in either theory, therefore the agreement  between theory and observations is to be understood only in a time-averaged sense.