HR: 0800h
AN: SH21C-0437    [Abstracts]
TI: Correlation of Solar Wind Parameters between SoHO and Wind
AU: * Ogilvie, K W
EM: Keith.W.Ogilvie@nasa.gov
AF: NASA Goddard Space Flight Center, Code 692, Greenbelt, MD 20771 United States
AU: Coplan, M A
EM: coplan@glue.umd.edu
AF: IPST, University of Maryland, College Park, MD 20742
AU: Desch, M
EM: michael.desh@nasa.gov
AF: NASA Goddard Space Flight Center , Code 695, Greenbelt, MD 20771 United States
AU: Roberts, D A
EM: aaron.roberts@nasa.gov
AF: NASA Goddard Space Flight Center, Code 692, Greenbelt, MD 20771 United States
AU: Ipavich, F
AF: IPST, University of Maryland, College Park, MD 20742
AB: SoHO was launched in December 1995, and reached L1 in January 1996. Since then it has been in a halo orbit about L1 with a semi-major axis of $103 R_e (\Delta Y_{GSE})$ and a semi-minor axis of $31 R_e$. $\Delta Z_{GSE}$ is approximately $19 R_e$. Wind was launched in November 1994, and has occupied a variety of orbits, spending most of the time in the interplanetary medium at distances greater than $100 R_e$ from Earth. Plasma instruments aboard SoHO and Wind have been operating reliably and stably since the minimum of solar cycle 23 in 1996, and have provided an opportunity to study correlations between their measurements over a period of more than half a solar cycle. We have calculated the maximum correlation coefficients between densities and fluxes measured at both spacecraft as a function of lag for the range $\pm 1$ hour (lag = time of maximum correlation - advection time). We find that the yearly averages of these correlations show a small decrease of 5% over the period 1996 through 2002, while the sunspot number increased by more than an order of magnitude. During the period 2000 through 2003, when Wind was in a distant pro-grade orbit, separation between the spacecraft was up to $\pm 400 R_e$ in the $Y_{GSE}$ direction. The correlation coefficients, averaged over 30 days, on each side of the XGSE axis, were equal to within measurement precision, indicating that the scale length in the interplanetary medium exceeds $800 R_e$. The yearly histograms of correlation coefficients for each of the years, 1996 through 2003, can be very well represented by the sum of two Gaussian functions, suggesting two distinct regimes. Individual events giving large correlation coefficients are due to shocks or discontinuities in the data stream. We suggest that events leading to small correlation coefficients can be associated with small-scale turbulence. These findings will be illustrated in a quantitative way.
DE: 2164 Solar wind plasma
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting