[1] Hourly averaged interplanetary magnetic field (IMF) and plasma data from the Advanced Composition Explorer (ACE) and Wind spacecraft, generated from 1 to 4 min resolution data time-shifted to Earth have been analyzed for systematic and random differences. ACE moments-based proton densities are larger than Wind/Solar Wind Experiment (SWE) fits-based densities by up to 18%, depending on solar wind speed. ACE temperatures are less than Wind/SWE temperatures by up to $25%. ACE densities and temperatures were normalized to equivalent Wind values in National Space Science Data Center's creation of the OMNI 2 data set that contains 1963-2004 solar wind field and plasma data and other data. For times of ACE-Wind transverse separations <60 R E , random differences between Wind values and normalized ACE values are $0.2 nT for jBj, $0.45 nT for IMF Cartesian components, $5 km/s for flow speed, and $15 and $30% for proton densities and temperatures. These differences grow as a function of transverse separation more rapidly for IMF parameters than for plasma parameters. Autocorrelation analyses show that spatial scales become progressively shorter for the parameter sequence: flow speed, IMF magnitude, plasma density and temperature, IMF X and Y components, and IMF Z component. IMF variations have shorter scales at solar quiet times than at solar active times, while plasma variations show no equivalent solar cycle dependence.Citation: King, J. H., and N. E. Papitashvili (2005), Solar wind spatial scales in and comparisons of hourly Wind and ACE plasma and magnetic field data,

ISEE 1, 2, 3, IMP 8, and Prognoz 7 observations of interplanetary shocks in 1978 and 1979 provide five instances where a single shock is observed by four spacecraft. These observations are used to determine best‐fit normals for these five shocks. In addition to providing well‐documented shocks for future investigations these data allow us to evaluate the accuracy of several shock normal determination techniques. When the angle between upstream and downstream magnetic field is greater than 20°, magnetic coplanarity can be an accurate single spacecraft method. However, no technique based solely on the magnetic measurements at one or multiple sites was universally accurate. Thus, we recommend using overdetermined shock normal solutions whenever possible, utilizing plasma measurements, separation vectors, and time delays together with magnetic constraints.

[1] It has been known that the variations in the interplanetary magnetic field (IMF) occur within surfaces that are tilted with respect to the solar wind velocity vector. This tilting of the IMF phase fronts may cause the propagation from a point of observation to another location to have delay times that vary substantially. Therefore for accurate delay calculations in real time, or for the creation of scientific data sets, it is necessary to be able to determine the phase surface orientation angles using the magnetic field measurements on one spacecraft only. Methods for calculating these tilt angles have been tested for accuracy by a comparison using IMF measurements on multiple satellites. One method is a variation of the minimum variance of the magnetic field, where it is constrained by the condition that the average field along the phase front's normal vector is zero. This method is referred to as MVAB-0. Another technique is to simply calculate the vector cross product between magnetic fields measured at two different sample times. The choices of the different parameters for the calculation and error discrimination are important. An optimization of parameters was done by testing how well the propagation delays from one spacecraft to others are predicted. The tests have indicated that, when optimized, both procedures work comparably well. It had also been found that further improvements to time delay predictions are obtained by combining together both the MVAB-0 and cross-product techniques, where the results of both methods must be in near agreement.Citation: Weimer, D. R., and J. H. King (2008), Improved calculations of interplanetary magnetic field phase front angles and propagation time delays,

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Abstract.NSSDC's OMNI dataset, which now spans 1963-1999, contains a collection of hourly means of interplanetary magnetic field (IMF) and solar wind (SW) plasma parameters measured near the Earth's orbit, as well as some auxiliary data. We report a study of solar cycle effects in planetary geomagnetic activity in which 27-day averages of several OMNI parameters are compared with equivalent Kp and Dst averages. Some established trends in these parameters over solar cycles are confirmed; for example, it is concluded that changes in the magnitude (rather than in direction) constitute the primary solar cycle variation in the IMF. However, this study also reveals that long-term changes in planetary geomagnetic activity are driven more actively by solar wind-magnetosphere coupling of an electrodynamic nature rather than by plasma transport into the magnetosphere. This suggests that ambient (background) interplanetary "electric" environment (in which the Earth's magnetosphere is immersed over the solar cycles) may play a more significant role in causing changes in the frequency of geomagnetic storms and substorms than previously realized.