OMNI 2 PreparationNew version of Hourly OMNI data set issued. (February, 2013)
Joe King and Natalia Papitashvili, NASA/SPDF and ADNET Systems, Inc.
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 395The full old OMNI documentation package is available HERE.
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) ----------------------------------------------------------------
If you have any questions/comments about OMNIWEB system, contact:
Dr. Natalia Papitashvili Mail Code 672,
NASA/Goddard Space Flight Center, Greenbelt, MD 20771|