O M N I 2 DATA SET
The OMNI 2 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.
OMNI 2 was created at NSSDC in 2003 as a successor to the OMNI data set
first created in the mid-1970's. A detailed discussion of the creation
OMNI 2 is at http://nssdc.gsfc.nasa.gov/omniweb/.
The table below identifies the dates for which different parameters of
OMNI data are available:
YYYY DDD - YYYY DDD
1963 331 - 2006 232 (IMF)
1963 331 - 2006 232 (Plasma)
1963 001 - 2006 304 (Kp index and sunspot number)
1963 001 - 1988 182 (AE index)
1990 001 - 1994 365 (Provisional AE index)
1963 001 - 2002 365 (Dst index)
2002 181 - 2006 120 (Provisional Dst)
1967 150 - 2004 366 (Energetic proton 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: OMNI2_YYYY.DAT,
and OMNI_MYYYY.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 GSE and, for IMF, GSM coordinate systems. The modified
OMNI_MYYYY.DAT files have been created from these files with reformatting
for COHOWeb compatibility and with the IMF and velocity
vectors have been transformed to RTN coordinate system by the use of
algorithm provided R. Parthasarathy (QSS and NSSDC).
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Daily and 27-day Averages files: omni_01_av.dat and omni_27_av.dat
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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OMNI2_YYYY.DAT FORMAT DESCRIPTION
WORD FORMAT Fill Value MEANING UNITS/COMMENTS
1 I4 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
19 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 9999999. 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 F6.3 9.999 Na/Np Alpha/Proton ratio
29 F6.2 99.99 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
30 F9.0 9999999. sigma T Degrees, K
31 F6.1 999.9 sigma N N/cm^3
32 F6.0 9999. sigma V km/s
33 F6.1 999.9 sigma phi V Degrees
34 F6.1 999.9 sigma theta V Degrees
35 F6.3 9.999 sigma-ratio
36 F7.2 999.99 Electric field -[V(km/s) * Bz (nT; GSM)] * 10**-3. (mV/m)
37 F7.2 999.99 Plasma beta Beta = [(T*4.16/10**5) + 5.34] * Np / B**2
38 F6.1 999.9 Alfven mach number Ma = (V * Np**0.5) / 20 * B
39 I3 99 Kp Planetary Geomagnetic Activity Index
(e.g. 3+ = 33, 6- = 57, 4 = 40, etc.)
40 I4 999 R Sunspot number
41 I6 99999 DST Index nT
42 I5 9999 AE-index from NGDC
43 F10.2 999999.99 Proton flux number/cmsq sec sr >1 Mev
44 F9.2 99999.99 Proton flux number/cmsq sec sr >2 Mev
45 F9.2 99999.99 Proton flux number/cmsq sec sr >4 Mev
46 F9.2 99999.99 Proton flux number/cmsq sec sr >10 Mev
47 F9.2 99999.99 Proton flux number/cmsq sec sr >30 Mev
48 F9.2 99999.99 Proton flux number/cmsq sec sr >60 Mev
49 I3 0 Flag(***) (-1,0,1,2,3,4,5,6)
C O M M E N T S
(**) - 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 (Explorer 18) 18
IMP 3 (Explorer 28) 28
IMP 4 (Explorer 34) 34
IMP 5 (Explorer 41) 41
IMP 6 (Explorer 43) 43
IMP 7 (Explorer 47) 47 MAG and Plasma/MIT
IMP 7 (Explorer 47) 44 Plasma/LANL
IMP 8 (Explorer 50) 50 MAG and Plasma/MIT
IMP 8 (Explorer 50) 45 Plasma/LANL
AIMP 1 (Explorer 33) 33
AIMP 2 (Explorer 35) 35
HEOS 1 and HEOS 2 1
VELA 3 3
OGO 5 5
Merged LANL VELA Speed Data (July 1964 - March 1971) 97
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 99
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For the daily resolution data (omni_m_daily.dat), simple averages were taken over
the hourly values. The format is identical to that for the hour averages
However, the "hour" field has 0 as a value.and the "Magnitude of Average
Vector" field is the simple average of the 24 hourly values of this parameter.
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. N. Papitashvili
E-mail: natasha@mail630.gsfc.nasa.gov
Code 633,GSFC/NASA, Greenbelt, MD, 20771.
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