OMNIWeb Data Explorer - Near-Earth Heliosphere Data - NSSDC - Goddard Space Flight Center
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                 OMNI 2 Preparation 
Joe King and Natalia Papitashvili, NASA/SPDF and ADNET Systems, Inc.
New version of Hourly OMNI data set issued.  (February, 2013)
The hourly OMNI data set provides an almost 50-year record of near-Earth
solar wind magnetic field and plasma parameter variations, plus
geomagnetic activity indices and solar energetic particle fluxes. See
http://omniweb.gsfc.nasa.gov/ow.html.
New upgrades to this data set include:
1. A new prioritization on which spacecraft to use for hours with
   multiple sources.  Previously, we prioritized Wind over ACE through
   the end of 1999, and prioritized ACE thereafter.  Now, we have
   defined three intervals within 1998-2004 during which ACE is
   prioritized and outside of which (and after which) Wind is prioritized.
   The ACE-prioritized intervals are 1998/181-1999/129, 1999/229-2002/333, and
   2003/223-2004/119.  These ACE-prioritized intervals are when Wind either
   makes several magnetospheric incursions or is unusually far
   (e.g., >200 Re) from the magnetosphere.

2. IMP 6, 7, and 8 LANL and ACE/SWEPAM Na/Np ratios are cross
   normalized to Wind/SWE nonlinear-fit-based Na/Np ratios using the equations
   Na/Np(A,norm) = 1.23 * Na/Np(A,obsvd)
   Na/Np(I,norm) = 0.78 * Na/Np(I,obsvd)
   where A and I designate ACE and IMP respectively and "norm" designates
   the normalized values used in OMNI.  (No Na/Np cross
   normalization for any OMNI data source had been done prior to this update.)

3. Wind and ACE proton parameters.  Previously we used Wind/SWE parameters
   based on anisotropic nonlinear fits to Wind/SWE plasma distributions through
   November 2004, and we used cross-normalized Wind/SWE Key Parameter data
   thereafter.  Now, owing to their greater "robustness," the only Wind/SWE
   proton data we use for 1995-current are the cross-normalized SWE KP data.
   (SWE KP cross-normalization is to the SWE nonlinear fit data.)

   New cross-normalizations for Wind KP and ACE proton density and
   temperature values have been developed and used.  These are -
  
     For Wind/SWE KP Np and Tp data
     For Np, for all V and time,
     LogN(Wind/KP, norm) = -0.055 + 1.037 * LogN(Wind/KP, obsvd)
     For Tp, for all V and for 1995-7,
     LogT(Wind/KP, norm) = -0.030 + 1.055 * LogT(Wind/KP, obsvd)
     For Tp, for all V and for >= 1998,
     LogT(Wind/KP, norm) = LogT(Wind/KP, obsvd)

    ACE/SWEPAM Np and Tp data:
    Let t be fractional years since 1998.0. (E.g., t = 1.5 on July 1, 1999.)
    Let V = solar wind speed
    N = ACE/SWEPAM proton density as observed
    Nn = value of N as normalized to equivalent Wind/SWE nonlinear fit proton densities
    For V < 395 km/s, Nn = [0.925 + 0.0039 * t] * N
    For V > 405 km/s, Nn = [0.761 + 0.0210 * t] * N
    For 395 < V < 405, Nn = [74.02 - 0.164*V - 6.72*t + 0.0171*t*V] * N/10
    For temperature (all V), LogT(norm) = -0.069 + 1.024 * LogT(obsvd)
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The full old OMNI documentation package is available HERE.
A new comprehensive documentation page will be available soon.


If you have any questions/comments about OMNIWEB system, contact: Dr. Natalia Papitashvili Mail Code 672, NASA/Goddard Space Flight Center, Greenbelt, MD 20771

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