O M N I  DATA SET
                                             
  The  OMNI  directory contains the hourly mean values of the interplanetary 
  magnetic  field (IMF) and solar wind plasma parameters measured by various 
  spacecraft near  the  Earth's  orbit,  as  well  as  geomagnetic and solar 
  activity indices, and energetic proton fluxes. 
                   
  The table below identifies the dates for which different parameters of
  OMNI data are available:

  YYYY DDD - YYYY DDD                    

  1963 331 - 2002 343 (IMF)               
  1963 331 - 2001 207 (Plasma)            
  1963 306 - 2002 304 (Geomag.Activity)   
  1963 306 - 2002 181 (DST indices)       
  2000 001 - 2002 265 (Provisional DST)   
  1973 001 - 2001 168 (Particle Fluxes)  

  Data gaps were filled with dummy numbers for the missing hours or entire
  days to make all files of equal length.  The character '9' is used to
  fill all fields for missing data according to their format, e.g.
  ' 9999.9' for a field with the FORTRAN format F7.1. Note that format F7.1
  below really means (1X,F6.1),etc.

  This directory  includes  two types of the ASCII flat files: OMNIYYYY.DAT, 
  and OMNI_MYYYYR.DAT  where  YYYY  is  a given year. The OMNIYYYY.DAT files 
  contain the original data where  the  IMF  and solar wind velocity vectors 
  are presented in the GSE  coordinate  system. The  modified OMNI_MYYYY.DAT 
  files have been  created  from  these  files, but  the  IMF and velocity 
  vectors have been recomputed in the RTN coordinate system by the use of
  algorithm provided R. Parthasarathy (Hughes STX and NSSDC).
                            
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Daily and 27-day Averages

We have computed daily and 27-day 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.)  No 
threshold numbers of finer scale points were required.

The daily averages are taken over OMNI's basic hourly values, and the 27-
day averages are taken over the daily averages.  The corresponding standard 
deviations relate only to these averagings and do not capture the 
variances in the higher resolution data.

The 27-day averages are for discrete Bartels rotation numbers.  Thus the 
first such average fully within 1999 spans January 9 through February 4.

The record format for the daily and 27-day averages is the same as for the 
hourly data, although certain fields have special meanings.

The time words (year, day, hour) correspond to the first hour of the 
average.

The ID's for the magnetic field and plasma spacecraft are set to zero, 
since the daily and 27-day averages frequently involve data from multiple 
spacecraft.

The numbers of fine scale points in the plasma and field averages are 
counts of (1) hourly values contributing to daily averages or (2) daily 
values contributing to 27-day 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.

Kp was treated specially.  After determining daily or 27-averages from 
basic values such as 10 (1), 13 (1+), 17 (2-), 20 (2), the average was 
rounded to the nearest "standard value" of Kp (i.e., 10, 13, 17, 20, ...).  
For cases where the average was exactly in the middle between standard 
values (e.g., 15), the lower standard value (13 in this case) was used.
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                         OMNIYYYY.DAT FORMAT DESCRIPTION     
                              
  Logical record: 250 characters + CR/LF                     
         
WORD  FORMAT  Fill Value         MEANING                  UNITS/COMMENTS
                               
 1      I5              Year                              1963, 1964, etc.
 2      I4              Decimal Day                       January 1 = Day 1
 3      I3              Hour                              0, 1,...,23   
 4      I5   9999      Bartels rotation number
 5      I3    0        ID for IMF spacecraft             See table
 6      I3    0        ID for SW plasma spacecraft       See table
 7      I4   999       # of points in the IMF averages 
 8      I4   999       # of points in the plasma averages 
 9     F6.1  999.9     Field Magnitude Average |B|       1/N SUM |B|, nT
10     F6.1  999.9     Magnitude of Average Field Vector sqrt(Bx^2+By^2+Bz^2) 
11     F6.1  999.9     Lat.Angle of Aver. Field Vector   Degrees (GSE coords) 
12     F6.1  999.9     Long.Angle of Aver.Field Vector   Degrees (GSE coords) 
13     F6.1  999.9     Bx GSE, GSM                       nT 
14     F6.1  999.9     By GSE                            nT 
15     F6.1  999.9     Bz GSE                            nT
16     F6.1  999.9     By GSM                            nT
17     F6 1  999.9     Bz GSM                            nT
18     F6.1  999.9     sigma|B|            RMS Standard Deviation in average
                                               magnitude (word 10), nT
29     F6.1  999.9     sigma B             RMS Standard Deviation in field
                                          vector, nT (**)
20     F6.1  999.9     sigma Bx            RMS Standard Deviation in GSE 
                                          X-component average, nT (*)
21     F6.1  999.9     sigma By            RMS Standard Deviation in GSE
                                          Y-component average, nT (*)
22     F6.1  999.9     sigma Bz            RMS Standard Deviation in GSE 
                                          Z-component average, nT (*)
23     F9.0  9999990.  Proton temperature                Degrees, K
24     F6.1  999.9     Proton Density                       N/cm^3 
25     F6.0  9999.     Plasma (Bulk) speed               km/s
26     F6.1  999.9     Plasma (Bulk) Flow Long. Angle    Degrees, GSE*, i.e.
                                     positive from from -X to Y or positive
                                     flow from the west limb of the Sun
27     F6.1  999.9     Plasma (Bulk) Flow Lat. Angle     Degrees, GSE, 
                                     positive to the northern heliosphere
28     F9.0  9999990.  sigma T                           Degrees, K
29     F6.1  999.9     sigma N                           N/cm^3
30     F6.0  9999.     sigma V                           km/s
31     F6.1  999.9     sigma phi V                       Degrees
32     F6.1  999.9     sigma theta V                     Degrees
33     I3    99        Kp               Planetary Geomagnetic Activity Index
                                       (e.g. 3+ = 33, 6- = 57, 4 = 40, etc.)
34      I3   99        C9               Geomagnetic activity index (0 to 9)
35      I4   999        R                                 Sunspot number
36      I6   99999     DST Index                         nT
37     F9.2  99999.90  Proton flux                 number/cmsq sec sr >1 Mev 
38     F9.2  99999.90  Proton flux                 number/cmsq sec sr >2 Mev
39     F8.2  9999.99   Proton flux                 number/cmsq sec sr >4 Mev
40     F8.2  9999.99   Proton flux                 number/cmsq sec sr >10 Mev
41     F8.2  9999.99   Proton flux                 number/cmsq sec sr >30 Mev
42     F8.2  9999.99   Proton flux                 number/cmsq sec sr >60 Mev
43      I3   0         Flag(***)                       (-1,0,1,2,3,4,5,6)     
                  
                                C O M M E N T S 
                       
    (*) - The sigma B values were not provided with HEOS IMF data, i.e. for
          such records the words 21-23 contain sigma|B| (repeat word 19),
          sigma theta B and sigma phi B in degrees respectively.
                        
   (**) - sigma B is sqrt((sigma Bx)^2 + (sigma By)^2 +(sigma Bz)^2)
                          
  (***) - If the flag is 0 there are no Proton Flux data, or all of the
          Proton Flux data are contaminated by the magnetospheric events
                     
          If the flag is 1 then the channels >1,>2,>4,>10,>30 Mev were
          judged to have magnetospheric `contamination'
                    
          If the flag is 2 then the channels >1,>2,>4,>10 Mev were judged
          to have magnetospheric `contamination'
                              
          If the flag is 3 then the channels>1,>2,>4 Mev were judged to 
          have magnetospheric `contamination'
                            
          If the flag is 4 then the channels >1,>2 Mev were judged to have
          magnetospheric `contamination'
                          
          If the flag is 5 then the channels >1 Mev channels were judged to
          have magnetospheric `contamination'
                          
          If the flag is 6 then no channel was judged to have magnetospheric
          `contamination'

          If the flag is -1 then not checked for M'sph c: relevant after 
          88/306.
         
              
                         TABLE: SPACECRAFT IDENTIFIERS 
                    
       Spacecraft Name                                    Spacecraft ID
                            
       IMP 1 (Expl 18)                                          18
       IMP 3 (Expl 28)                                          28    
       IMP 4 (Expl 34)                                          34
       IMP 5 (Expl 41)                                          41    
       IMP 6 (Expl 43)                                          43
       IMP 7 (Expl 47)                                          47    
       IMP 8 (Expl 50)                                          50 
       AIMP 1 (Expl 33)                                         33    
       AIMP 2 (Expl 35)                                         35   
       HEOS 1 and HEOS 2                                         1
       VELA 3                                                    3
       OGO 5                                                     5
       Merged LANL VELA Speed Data (July 1964 - March 1971)     99
       Merged LANL IMP T,N,V (Including all IMP 8 LANL Plasma)  98
       ISEE 1                                                   11
       ISEE 2                                                   12
       ISEE 3                                                   13
       PROGNOZ 10                                               10
       WIND                                                     51
       ACE                                                      71 
       No spacecraft                                             0
                  
                  
                        
                          OMNI_MYYYY.DAT FORMAT DESCRIPTION
                                                          
  Logical record = 82 characters + CR/LF  
                  
WORD  FORMAT FILL Value   MEANING                     UNITS/COMMENTS
                
1       I4                Year                              1963, 1964, 1965, etc.
2       I4                Decimal Day                       January 1 = Day 1  
3       I3                Hour                              0,1,...,23 
4      F7.1  9999.9       Heliographic Inertial Latitude    Degrees, +/-90
                          of the Earth 
5      F7.1  9999.9       Heliographic Inertial Longitude   Degrees, 0-360
                          of the Earth 
6      F6.1  999.9        BR RTN                            nanoteslas
7      F6.1  999.9        BT RTN                            nanoteslas
8      F6.1  999.9        BN RTN                            nanoteslas
9      F6.1  999.9        Field Magnitude Average |B        1/N SUM |B|, nT
10     F6.0  9999.        Bulk Flow speed                   km/s
11     F6.1  999.9       THETA - elevation angle           Degrees        
                          of the velocity vector (RTN) 
12     F6.1  999.9       PHI- azimuth angle                Degrees
                          of the velocity vector (RTN) 
13     F6.1  999.9        ION Density                       N/cm^3
14     F9.0  9999999.     Temperature                       Degrees, K   
                
                      
                  DESCRIPTION OF COORDINATE SYSTEMS
 
  The Heliographic Inertial (HGI) coordinates are Sun-centered and inertially
  fixed with respect to an X-axis directed along the intersection line of the
  ecliptic and solar equatorial  planes. The solar equator plane is inclined
  at 7.25 degrees from the ecliptic. This direction was towards ecliptic 
  longitude of 74.367 degrees  on  1  January  1900  at  1200  UT; because of
  precession of the celestial  equator, this longitude increases by 1.4 
  degrees/century. The Z axis  is  directed perpendicular and northward from 
  the solar equator, and the  Y-axis  completes  the right-handed set. This 
  system differs from the usual  heliographic  coordinates  (e.g.  Carrington
  longitudes) which are fixed in the frame of the rotating Sun. 

  The RTN system is fixed at a spacecraft (or the planet). The R  axis 
  is directed radially away from the Sun, the T axis is the cross product of 
  the solar rotation axis and  the  R  axis,  and  the  N  axis is the cross 
  product of the R  and  T  axes.  At  zero  heliographic latitude, when the 
  spacecraft is in the solar equatorial plane, the N and solar rotation axes 
  are parallel.
                      
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                 Convention for Latitude and Longitude Angles
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  Latitude  and  longitude  angles  of  solar wind plasma flow are generally
  measured  from the radius vector away from the Sun. In all cases, latitude
  angles  are  positive for north-going flow. The flow longitude angles have
  been  treated differently for the near-Earth data, i.e. the OMNI, and for 
  the deep space data. The flow is positive for  the  near-Earth  data  when
  coming from the right side of the Sun as viewed  from  the Earth, i.e. 
  flowing toward +Y from -X GSE or opposite to the  direction of planetary 
  motion. On the other hand, the flow longitudes for the deep space spacecraft
  use the opposite sign convection, i.e. positive for flow in the +T direction
  in the RTN system.
                                    
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  Acknowledgement:

 Use of these data in publications should be accompanied at minimum by
 acknowledgements of the National Space Science Data Center.  
             
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                                 NSSDC contact:
 
  Dr. J. H. King,                           Dr. N. Papitashvili  
  E-mail: king@nssdca.gsfc.nasa.gov       E-mail: natasha@nssdca.gsfc.nasa.gov
                  
                   Code 633,GSFC/NASA, Greenbelt, MD, 20771.
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