1: Purpose of this document

This document describes at a high level the underlying OMNI High res. data contained in OMNIWeb system. A companion file at http://omniweb.gsfc.nasa.gov/html/omni_min_doc.html gives significantly more detail.

4: Description of records and words

This section lists all the words in the records of the OMNI data set, and various notes and units as appropriate. The format for each word is as contained in the ftp-accessible monthly annual ASCII files. Each record contains 37 words as described below.

   WORD      TYPE       MEANING                UNITS/COMMENTS

     1       I4         Year                   1963,1964,1965...
     2       I4         Decimal Day            Day of year (Jan 1 = Day 1)
     3       I3         Decimal Hour           (0, 1, ...23; average for "1" is from
                                                01:00 to 02:00)
     4       I3         Minute                 (0,1,...59)

     5       I3         ID for IMF SC          See table in section 6
     6       I3         ID for SW Plasma SC    See table in section 6
     7       I4         # of fine time scale
                        points in IMF Avgs
     8       I4         # of fine time scale
                        points in Plasma Avgs
     9       I4         Persent of Interpolation
    10       I7         Timeshift                 sec
    11       I7         RMS Timeshift             sec
    12       F6.2       RMS Min Var vector
    13       I7         Time between observations sec
    14       F8.2       Field Magnitude Avg, 
                              <F>               nT
    15       F8.2        Bx,GSE                 (nT)
    16       F8.2        By,GSE                 (nT)
    17       F8.2        Bz,GSE                 (nT)
    18       F8.2        By,GSM                 (nT)
    19       F8.2        Bz,GSM                 (nT)
                                                 see footnote GSM



    20       F8.2        sigma-|B|              RMS Standard deviation in avg
                                               magnitude (wd. 14), nT
    21       F8.2        sigma-B                RMS Standard deviation in field
                                               vector, in nT; see footnote 3
    22       F8.1        Bulk speed             GSE, Km/sec.
    23       F8.1        Vx, Velocity           GSE, Km/sec.
    24       F8.1        Vy, Velocity           GSE, Km/sec.
    25       F8.1        Vz, Velocity           GSE, Km/sec.
    26       F7.2        Proton density          #N/cm**3

    27       F9.0        Proton temperature     Degrees Kelvin
    28       F6.2        Flow Pressure          P (nPa) = (1.67/10**6) * Np*V**2 * (1+ 4*Na/Np)
                                                for hours with non-fill Na/Np ratios and
                                                P (nPa) = (2.0/10**6) * Np*V**2
                                                for hours with fill values for Na/Np more 

    29       F7.2        Electric field         mV/m, -V(km/s) * Bz (nT; GSM) * 10**-3 
    30       F7.2        Plasma beta            Beta = [(T*4.16/10**5) + 5.34] * Np / B**2, more 
    31       F6.1        Alfven mach number     Ma = (V * Np**0.5) / 20 * B , more  
    32       F8.2        S/c position X         GSE,Re 
    33       F8.2        S/c position Y         GSE,Re 
    34       F8.2        S/c position Y         GSE,Re 
    35       F8.2        BSN, X                 Bowshock position X, GSE,Re 
    36       F8.2        BSN, Y                 Bowshock position Y, GSE,Re 
    37       F8.2        BSN  Z                 Bowshock position Z, GSE,Re 

--------------------------------------------------------------------------
format='(2I4,4I3,3I4,2I7,F6.2,I7, 8f8.2,4f8.1,f7.2,f9.0,f6.2,2f7.2,f6.1,6F8.2)'

Footnote 1:
Flow-vector cartesian components and angles in GSE coordinates:
Vx = - V * cos(theta) * cos(phi)
Vy = + V * cos(theta) * sin(phi)
Vz = + V * sin(theta)

Footnote gsm:
The computation of standard By and Bz, GSM is taken from the GEOPACK-2008 software package developed by Drs. Nikolai Tsyganenko.

Footnote 3:
Sigma-B is computed as: SQRT [(sigma(Bx))**2 + (sigma(By))**2 + (sigma(Bz))**2]. Note that this is the length of the vector formed from the standard deviations of component averages. It is not the standard deviation in the length of the vector formed from the average components.

5: 5-min Averages

We have computed 5-min average values for all the OMNI parameters, and have made them accessible via OMNIWeb and via anon/ftp. Only arithmetic averaging was done. (No averaging of logarithms.)

The 5-min averages are taken over OMNI's basic hourly values. The corresponding standard deviations relate only to these averagings and do not capture the variances in the higher resolution data.

The record format for 5-min averages is the same as for the minute data. The time words (year, day, hour,min) correspond to the first minute of the averaging period 5-min interval.

The ID's for the magnetic field and plasma spacecraft are set to zero, since the 5-min averages frequently involve data from multiple spacecraft.

The numbers of fine scale points in the plasma and field averages are counts of minute values contributing to 5-min averages. NOTE THAT WE HAVE NOT REQUIRED ANY MINIMUM NUMBER OF POINTS TO COMPUTE AN AVERAGE. For cases where there was only one point, the standard deviations were set to zero.

6: Spacecraft identifiers

Spacecraft name         Spacecraft ID
---------------         -------------

IMP 8 (Expl 50)                50 
WIND                           51
ACE                            71 

8: Contact and General Information

For questions or comments about the OMNI data contents, please contact Dr. Natalia Papitashvili, Natalia.E.Papitashvili@gsfc.nasa.gov, Code 612, Goddard Space Flight Center, Greenbelt, MD, 20771.

---

Acknowledgement to the SPDF OMNIWeb database as the source of data used in publications is requested: "The OMNI data were obtained from the GSFC/SPDF OMNIWeb interface at http://omniweb.gsfc.nasa.gov". Further, for recent years when few sources (IMP 8, Wind, ACE) contributed to OMNI, it would be appropriate to also cite the PI's who provided the data to OMNI. Copies of preprints or reprints of OMNI-based publications sent to Natalia Papitashvili (address below) would be appreciated for tracking purposes.

The best citable reference to OMNI data is J.H. King and N.E. Papitashvili, Solar wind spatial scales in and comparisons of hourly Wind and ACE plasma and magnetic field data, J. Geophys. Res., Vol. 110, No. A2, A02209, 10.1029/2004JA010804.

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