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/. Time spans of various parameters are periodically extended. The documentation file at http://omniweb.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 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 having been transformed to RTN coordinate system by the use of algorithm provided R. Parthasarathy (QSS and NSSDC). --------------------------------------------------------------------------- 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. ------------------------------------------------------------------------- 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 (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 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) 50 I4 ap-index, nT, from NGDC 51 F6.1 f10.7_index, from NGDC 52 F6.1 PC(N) index, from NGDC 53 I6 AL-index, nT, from Kyoto 54 I6 AU-index, nT, from Kyoto 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 ACE 71 Geotail 60 No spacecraft 99 --------------------------------------------------------------------------------- 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. -------------------------------------------------------------------------- Convention for Latitude and Longitude Angles -------------------------------------------------------------------------- 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. -------------------------------------------------------------------------- Acknowledgement: Use of these data in publications should be accompanied at minimum by acknowledgements of the GSFC/SPDF and OMNIWeb. ------------------------------------------------------------------------- SPDF contact: Dr. N. Papitashvili E-mail: natalia.e.papitashvili@nasa.gov Code 673,GSFC/NASA, Greenbelt, MD, 20771. --------------------------------------------------------------------- --------------------------------------------------------------------------------