OMNIWeb Data Explorer - Near-Earth Heliosphere Data
About using this interface

This note explains the analysis and display capabilities of the interface at http://omniweb.gsfc.nasa.gov/form/sc_scat_min2.html The underlying data, 1-min averaged unshifted Wind magnetic field and plasma data and ACE data as shifted to the Wind location by each of four shift techniques, are explained in a companion file at http://omniweb.gsfc.nasa.gov/html/sc_merge_data.html. In particular, each of the variables made accessible through this interface, and the 4 shift techniques, are described in detail there.

This interface allows users to choose any one variable for any pair of the five available data sets from ACE and Wind and for any time span of interest, with optional filtering described shortly, and to produce cross correlations between, and means and standard deviations of, the two time series, plus other parameters defined two paragraphs below.

Filtering means specifying minimum and/or maximum values, for either or both of the selected data sets, for the variable selected for analysis and/or for any other combination of variables in the data records and/or for the "impact parameter" between the two selected spacecraft. Impact parameter is the distance by which a downstream spacecraft misses seeing a plasma element previously seen by an upstream spacecraft; it is more fully described at http://omniweb.sci.gsfc.nasa.gov/ftpbrowser/impact.html. Records not satisfying the filtering conditions are excluded from the analysis.

The user makes an initial selection among full analysis, partial analysis, and list. In selecting data for analysis according to user criteria, a numeric table is assembled. The "list" option simply displays this numeric table and defines its columns. The "full analysis" option produces the means and standard deviations of the two time series and a cross correlation between the two, the initial impact parameter, a scatter plot, linear regression fit parameters and an rms deviation of the scatterplot points relative to the regression fit. The "partial analysis" option produces only the means and standard deviations of the two time series, the cross correlation function, and the initial impact parameter.

After specifying analysis level or list, the user must specify which of the 5 available data sets is to be the "X spacecraft" for the scatter plot and regression fit, and which is to be the "Y spacecraft." Then the desired time span is specified, to one hour resolution; note that span covered includes 1-min records of the first and last hour specified plus the hours in between. Finally, the user selects the variable to be analyzed (via the radial buttons on the left side) and specifies the filtering conditions, if any, via one or more of the four columns of boxes on the right side. (As an example, if the user wanted to limit data included to records wherein the flow speed of the Y spacecraft was 500 km/s or greater, he/she would key "500" into the third box to the right of "Flow speed, km/s" on the interface screen, leaving the other three boxes empty.)

The separate ability to specify an impact parameter range is a carryover from earlier interfaces to hourly resolution data wherein the individual runs may address time spans over which impact parameters change significantly. This interface automatically outputs the impact parameter at the start of the time interval specified regardless of whether a desired impact parameter range is specified.

There are two approaches to determining the linear regression fit parameters, one labeled "Delta-Y" and the other "Perpdist." These are described at http://omniweb.gsfc.nasa.gov/html/scat_des.html. Given that this interface only enables fitting a parameter from one data set against the same parameter from another data set, use of the "Perpdist" method is recommended for all runs.



If you have any questions/comments about this service contact: Dr. Natalia Papitashvili, Space Physics Data Facility Mail Code 672, NASA/Goddard Space Flight Center, Greenbelt, MD 20771

NASA Official: Dr. Robert McGuire, Head of the Space Physics Data Facility