O M N I 2 DATA SET
The /data/omni/low_res_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
known as OMNI2 data.
OMNI2 was created at NSSDC in 2003 as a successor to the OMNI data set
first created in the mid-1970's.
Time spans of various parameters are periodically extended.
The documentation file at
http://omniweb.sci.gsfc.nasa.gov/html/ow_data.html
gives the current time spans of the following parameter groups:
Magnetic field
Plasma
Kp index and sunspot number
AE, AL,AU index
Provisional AE, AL, AU index
Quick look AE, AL, AU index
Dst index
Provisional Dst index
Quick look Dst
Energetic proton fluxes
ap-index and f10.7_index
PC(N) index
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Note: see "extended" directoty for more parameters.
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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 OMNI2_YYYY.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 having been transformed to RTN coordinate system.
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Daily and 27-day Averages files: omni_01_av.dat; omni_27_av.dat; omni_m_daily.dat
We have computed daily and 27-day average values for all the OMNI parameters in the
OMNI2_YYYY.dat files, and we have computed daily averages from the OMNI_MYYYY.dat files.
We have made these lower resolution averages also 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 99 ID for IMF spacecraft See table
6 I3 99 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
see http://geo.phys.spbu.ru/~tsyganenko/Geopack-2008.html
developed by Drs. Nikolai Tsyganenko.
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 (Flow) speed km/s
26 F6.1 999.9 Plasma Flow Long. Angle Degrees, quasi-GSE*
27 F6.1 999.9 Plasma Flow Lat. Angle Degrees, GSE*
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-Na/Np
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 (new version 2)
41 I6 99999 DST Index nT, from Kyoto
42 I5 9999 AE-index nT, from Kyoto
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)
50 I4 999 ap-index nT
51 F6.1 999.9 f10.7_index ( sfu = 10-22W.m-2.Hz-1)
52 F6.1 999.9 PC(N) index
53 I6 99999 AL-index, from Kyoto nT
54 I6 99999 AU-index, from Kyoto nT
55 F5.1 99.9 Magnetosonic mach number= = V/Magnetosonic_speed
Magnetosonic speed = [(sound speed)**2 + (Alfv speed)**2]**0.5
The Alfven speed = 20. * B / N**0.5
The sound speed = 0.12 * [T + 1.28*10**5]**0.5
About Magnetosonic speed check http://ftpbrowser.gsfc.nasa.gov/bow_derivation1.html also
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C O M M E N T S
(*) Quasi-GSE for the flow longitude angle means the angle increases from zero
to positive values as the flow changes from being aligned along the -X(GSE)
axis towards the +Y(GSE) axis. The flow longitude angle is positive for
flow from west of the sun, towards +Y(GSE).
The flow latitude angle is positive for flow from south of the sun,
towards +Z(GSE)
(**) - 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 data were not checked for magnetospheric
contamination; this is relevant after 1988/306.
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 -mag, plasma_KP; 52-Plasma_definitive
ACE 71
Geotail 60
No spacecraft 99
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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 Proton 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 GSFC/SPDF and OMNIWeb.
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SPDF contact:
Dr. N. Papitashvili E-mail: natalia.e.papitashvili@nasa.gov
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