The Low Resolution OMNI (LRO) data set is primarily a 1963-to-current compilation of hourly-averaged, near-Earth solar wind magnetic field and plasma parameter data from several spacecraft in geocentric or L1 (Lagrange point) orbits. The data have been extensively cross compared, and, for some spacecraft and parameters, cross-normalized. Time-shifts of higher resolution data to expected magnetosphere-arrival times are done for data from spacecraft in L1 orbits (ISEE 3, Wind, ACE), prior to taking hourly averages.
LRO also provides other widely accessed data that are frequently used with solar
wind data. In particular, LRO provides fluxes of protons with energies above
1, 2, 4, 10, 30, and 60 MeV from several IMP and GOES spacecraft, and provides
a wide range of geomagnetic and solar activity indices.
The data are made available at daily and 27-day resolutions, in addition to
hourly resolution.
They are made accessible with a variety of functionalities from https://omniweb.gsfc.nasa.gov/ow.html.
High Resolution OMNI (HRO) data set include 1-min and 5-min bow-shock-nose-
shifted solar wind magnetic field and plasma data from IMP 8, Geotail, Wind and ACE
see: https://omniweb.gsfc.nasa.gov/ow_min.html
YYYY-MM-DD (DDD) - YYYY-MM-DD (DDD) Parameters 1963-11-27 (331) - 2024-09-13 (257) IMF 1963-11-27 (331) - 2024-09-29 (273) Plasma 1967-05-30 (150) - 2020-03-04 (064) Energetic Proton Fluxes 1963-01-01 (001) - 2024-10-03 (277) Kp,ap indexes 1963-01-01 (001) - 2024-09-30 (274) New Sunspot Number(version 2) 1963-01-01 (001) - 2024-10-03 (277) F10.7 index 1963-01-01 (001) - 2020-12-31 (366) Dst Final indices 2021-01-01 (001) - 2023-12-31 (365) Provisional Dst indices 2024-01-01 (001) - 2024-04-30 (121) Quick Look Dst-index 2024-05-01 (122) - 2024-05-31 (152) Provisional Dst indices 2024-06-01 (153) - 2024-10-03 (277) Quick Look Dst-index 1963-01-01 (001) - 1988-06-30 (182) AE, AL,AU-index 1988-07-01 (183) - 1989-12-31 (365) No AE, AL,AU-indexes (except March of 1989) 1990-01-01 (001) - 2019-12-31 (365) Provisional AE, AL,AU-index 2024-05-10 (131) - 2024-05-14 (135) Provisional AE, AL, AU indexes 1963-01-01 (001) - 2024-10-02 (276) Solar Lyman-alpha 1975-01-01 (001) - 2023-12-31 (365) PCN index (Definitive) See below for differences among final, provisional and quick look Dst and AE indices
WORD TYPE Fill values MEANING UNITS/COMMENTS
1 I4 Year 1963,1964,1965...
2 I4 Decimal Day Day of year (Jan 1 = Day 1)
3 I3 Decimal Hour (0, 1, ...23; average for "1" is from
01:00 to 02:00)
4 I5 9999 Bartels Rotation Number
5 I3 99 ID for IMF SC See table below
6 I3 99 ID for SW Plasma SC See table below
7 I4 999 # of fine time scale
points in IMF Avgs
8 I4 999 # of fine time scale
points in Plasma Avgs
9 F6.1 999.9 Field Magnitude Avg, (scalar)
<F> nT
10 F6.1 999.9 Magnitude of Average nT
Field vector, |<B>|
11 F6.1 999.9 Lat. Angle of avg. Deg (GSE Coords)
Field vector
12 F6.1 999.9 Long. Angle of avg. Deg (GSE Coords)
Field vector
13 F6.1 999.9 Bx,GSE (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) see footnote 4
17 F6.1 999.9 Bz,GSM (nT) see footnote 4
18 F6.1 999.9 sigma-|B| RMS Standard deviation in avg
magnitude (wd. 10), nT
19 F6.1 999.9 sigma-B RMS Standard deviation in field
vector, in nT; see footnote 3
20 F6.1 999.9 sigma-Bx RMS Standard deviation in GSE X
comp. av, nT
21 F6.1 999.9 sigma-By RMS Standard deviation in GSE Y
comp, av, nT
22 F6.1 999.9 sigma-Bz RMS standard deviation in GSE Z
comp, av, nT
23 F9.0 9999999. Proton temperature Degrees Kelvin
24 F6.1 999.9 Proton density #N/cm**3
25 F6.0 9999. Bulk speed Km/sec. (scalar)
26 F6.1 999.9 Bulk flow longitude phi-V, degrees. phi-V increases positively/
negatively from zero as the flow direction
changes from being along
the -Xgse axis toward the +Ygse/-Ygse axis;
see footnote 1)
27 F6.1 999.9 Bulk flow latitude theta-V, degrees. theta-V increases positively/
negatively from zero as the flow direction changes
from being in
the Xgse-Ygse plane toward the +Zgse/-Zgse axis;
see footnote 1)
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
For details click HERE
30 F9.0 9999999. sigma-T Degrees Kelvin
31 F6.1 999.9 sigma-n cm -3
32 F6.0 9999. sigma-V km/sec
33 F6.1 999.9 sigma-phi-V deg
34 F6.1 999.9 sigma-theta-V deg
35 F6.3 9.999 sigma-ratio
36 F7.2 999.99 Electric field mV/m, -V(km/s) * Bz (nT; GSM) * 10**-3
37 F7.2 999.99 Plasma beta Beta = [(T*4.16/10**5) + 5.34] * Np / B**2,
For details click HERE
38 F6.1 999.9 Alfven mach number Ma = (V * Np**0.5) /(20 * B) ,
For details click HERE
39 I3 99 Kp*10 3-hr Kp index from GFZ, Potsdam
(See footnote 2)
40 I4 999 R Daily New sunspot Number (version 2) from
http://sidc.oma.be/silso/datafiles
Details HERE
41 I6 99999 DST Index nT, from Kyoto
42 I5 9999 AE-index nT, from Kyoto
43 F10.2 999999.99 PROT Flux 1/(cm^2 sec ster), >1 MeV
44 F9.2 99999.99 PROT Flux 1/(cm^2 sec ster), >2 MeV
45 F9.2 99999.99 PROT Flux 1/(cm^2 sec ster), >4 MeV
46 F9.2 99999.99 PROT Flux 1/(cm^2 sec ster), >10 MeV
47 F9.2 99999.99 PROT Flux 1/(cm^2 sec ster), >30 MeV
48 F9.2 99999.99 PROT Flux 1/(cm^2 sec ster), >60 MeV
49 I3 0 M'SPH Flux Flag = 6: No m'spheric contribution
= 5: M'sph contrib in lowest
energy channel
= 4: M'sph c in lowest 2 chnls
...
= 1: M'sph c in lowest 5 chnls
= 0: M'sph c in all channels
=-1: Not checked for M'sph c:
relevant after 88/306
(See Flux)
50 I4 999 ap-index 3-hr ap index, nT, from GFZ, Potsdam
51 F6.1 999.9 f10.7_index Daily index,(10**-22) Watts/meter sq/hertz
adjusted to 1AU from Canada
52 F6.1 999.9 PC(N) DTU,Data Center for Geomagnetism, Copenhagen
53 I6 99999 AL-index nT, from Kyoto
54 I6 99999 AU-index nT, from Kyoto
55 F5.1 99.9 MAC 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
For details click HERE
56 F9.6 0.999999 Daily Solar Lyman-alpha, W/m^2
See http://lasp.colorado.edu/lisird/lya/
57 F7.4 9.9999 Proton Quasy-Invariant (QI)=(B^2/8*pi)/(Den*V^2/2)
QI ==SW (magnetic energy density)/(kinetic energy density)
For details click HERE
--------------------------------------------------------------------------
FORMAT(2I4,I3,I5,2I3,2I4,14F6.1,F9.0,F6.1,F6.0,2F6.1,F6.3,F6.2,
F9.0,F6.1,F6.0,2F6.1,F6.3,2F7.2,F6.1,I3,I4,I6,I5,F10.2,5F9.2,I3,I4,2F6.1,2I6,F5.1,F9.6,F7.4)
Note that for missing data, fill values consisting of a blank
followed by 9's which together constitute the Ix or Fx.y format are used.
Footnote 1:
The flow OMNI "phi" angle is opporite GSE "phi" angle, threrfore,
Flow-vector cartesian components in GSE coordinates
may be derived from the given speed and angles as
Vx = - V * cos(theta) * cos(phi)
Vy = + V * cos(theta) * sin(phi)
Vz = + V * sin(theta)
and vise versa: two angles may be derived from the given speed and Vx,Vy,Vz comp. as
a_theta=vz/V
theta=(180.*asin(a_theta))/!PI
a_phi=Vy/(-Vx)
phi=(180.*atan(a_phi))/!PI
Footnote 2:
Footnote 3:
Sigma-B is computed as:
SQRT [(sigma(Bx))**2 + (sigma(By))**2 + (sigma(Bz))**2].
Note that this is the length of the vector formed from the standard
deviations of component averages. It is not the standard deviation in
the length of the vector formedfrom the average components.
Footnote 4:
The computation of standard By and Bz, GSM
is taken from the GEOPACK-2008
software package developed by Drs. Nikolai Tsyganenko.
We have computed daily and 27-day average values for all the OMNI2 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. See special note on IMF angles below.
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 averaging period (day or 27-day interval).
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 higher standard value (17 in this case) was used.
On December 6, 2004, words 10-12 (magnitude and direction angles of vector-averaged IMF), which had been determined by simple averaging over finer scale values of these words, were replaced in OMNI by values computed from daily (or 27-day) averaged IMF Cartesian components.
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 MAG and Plasma/MIT IMP 7 (Expl 47) 44 Plasma/LANL IMP 8 (Expl 50) 50 MAG and Plasma/MIT IMP 8 (Expl 50) 45 Plasma/LANL 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 speeds 97 Merged LANL IMP-6,-7,-8 T,N,V 98 ISEE 3 13 ISEE 1 11 PROGNOZ 10 10 WIND 51-Mag, Plasma-KP; 52-for Plasma definitive data ACE 71 Geotail 60 -- No spacecraft 99 Note: our best final data for many years are: magnetic field data (S/C ID=51) and Wind definitive plasma data (S/C ID=52) from Wind. If we have no Wind definitive plasma data we use Wind Plasma-KP ( S/C ID=51) or other sources, see table above. So, Multiple source OMNI data base is not “hard” product, which stay unchanged after it has been made/updated, we try to make quality improvement when the new data became available. (e.g. one of the sources has been reprocessed by PI's)
The OMNI2 data set has, since its creation, contained daily sunspot numbers (Rz) assigned to each hour
of the relevant day and three geomagnetic activity indices: Kp (3-hr), AE (1-hr), and Dst (1-hr).
In 2009, additional indices were added: F10.7 (daily) , ap (3-hr), AL, AU and PCN.
The Kp, ap obtained from German Research Centre for Geosciences at https://kp.gfz-potsdam.de/en/data;
Note footnote 2 above, about OMNI's mapping of standard Kp values of
0, 0+, 1-, 1, 1+, ..., 9-, 9 to 0, 3, 7, 10, 13, ... 87, 90.
Daily Flux Density (F10.7) adjusted for 1 A.U, (for middle hour: 20:00) from Canada
( http://www.spaceweather.gc.ca/solarflux/sx-en.php, https://www.spaceweather.gc.ca/forecast-prevision/solar-solaire/solarflux/sx-5-flux-en.php)
at ftp://ftp.seismo.nrcan.gc.ca/spaceweather/solar_flux/daily_flux_values/fluxtable.txt
Rz ( sunspot numbers) from Belgium SILSO Cenrer at http://sidc.oma.be/silso/datafiles/.
Hourly AE, AL, AU and Dst indices are computed at and obtained from the
World Data Center for Geomagnetism, operated by the Data Analysis
Center for Geomagnetism and Space Magnetism at Kyoto University,
Japan. See http://swdcwww.kugi.kyoto-u.ac.jp/dstae/index.html.
This page, and those it links to, give full accounts of the derivations of final,
provisional and quick-look AE and Dst values. Definitive time
series of AE, Dst and other indices reach back to 1957 on the
Kyoto web site. There are provisional values of AE and Dst also
available from Kyoto Definitive hourly
values of AE and Dst are included in OMNI 2 from 1963 to their
ends and are extended when possible. We thank
Drs. T. Iyemori and T. Kamei for permission to include these
indices in OMNI 2.
PC(N) is the Polar Cap Index determined from the North polar cap station at Thule, Greenland.
The index is basically a 15-min index that we have averaged up to hourly for inclusion in OMNI.
PC(N) is taken from https://ftp.space.dtu.dk/WDC/indices/pcn/PCN_definitive/
, World Data Center for Geomagnetism,
National Space Institute, Copenhagen.
Note: WDC at Copenhagen stop to produce the PCN index after 2014.
Energetic particle data sources: Fluxes of protons above 6 energy thresholds (1, 2, 4, 10, 30, 60 Mev) from the IMP 7 and IMP 8 Charged Particle Measurement Experiment (CPME; Principal Investigator S.M. Krimigis, then R.B. Decker) are included in OMNI and OMNI 2 for the period January 1, 1973, through the end of 2005 shortly after which IMP 8 operations terminated. The data were prepared and provided by CPME Co- Investigator T.P. Armstrong and colleagues at U. Kansas and Fundamental Technologies, LLC. The instrument and data are further described at http://sd-www.jhuapl.edu/IMP/imp_index.html and at http://imp.ftecs.com/
Fluxes of protons above 1, 10, 30 and 60 MeV for mid-1967 through the end of 1972, from the JHU/APL Solar Proton Monitoring Experiment (SPME) on IMP 4 (1967/150 - 1969/123) and IMP 5 (1969/172 - 1972/358) were added to OMNI 2 shortly after its creation. The fluxes were computed at NSSDC from count rates provided on tape to NSSDC decades earlier. The values are not reliable absolute measures of quiet time galactic fluxes, but are good for solar and shock- accelerated particles. cf. Williams and Bostrom, J. Geophys. Res.,74, 3019, 1969.
Fluxes of protons above 10, 30 and 60 MeV, as measured by NOAA's geosynchronous GOES 11 spacecraft for 2006-2010, from GOES 13 for 2011 -2017/11 and from GOES 14 for 2017/12 later; (cf. https://satdat.ngdc.noaa.gov/sem/goes/data/avg/), were added to OMNI 2. (The GOES 13 and 14 data added to OMNI 2 are actually averages over the fluxes given at NOAA for eastward- looking and westward looking sensors.) Principal Investigator for the GOES energetic particle instruments is currently T. Onsager, and key responsible NOAA person is D. Wilkinson. Comparisons of IMP 8, GOES 10 and GOES 11 proton flux values obtained between 1999 and 2005 show reasonably good agreement during solar particle flux events; see https://omniweb.gsfc.nasa.gov/ftpbrowser/flux_ogg.html.
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 spacecraft priorities for 7 intervals:
1. 1995/001-1998/180 Wind, ACE, IMP8, Geotail
2. 1998/181-1999/129 ACE, Wind, IMP8, Geotail
3. 1999/130-1999/228 Wind, ACE, IMP8, Geotail
4. 1999/229-2002/333 ACE, Wind, IMP8, Geotail
5. 2002/334-2003/222 Wind, ACE
6. 2003/223-2004/119 ACE, Wind,
7. 2004/120-current Wind, ACE
These ACE-prioritized intervals are when Wind either makes several magnetospheric
incursions or is unusually far (e.g., >200 Re) from the magnetosphere.
Table 1 shows the sources of LRO magnetic field data.
The parentheses after the spacecraft names show our numeric spacecraft identifiers.
As of 2014, Wind and ACE data were being periodically added to LRO.
The current latest date of magnetic field data in LRO is given at
https://omniweb.gsfc.nasa.gov/html/ow_data.html.
Table 1 ----------- Spacecraft Key persons Data time span References ---------- ----------- ----------------- ---------------- IMP 1 (18) Ness 11/27/63-02/15/64 Ness et al, 1964 IMP 3 (28) Ness 06/01/65-01/29/67 Ness et al, 1964 AIMP 1 (33) Ness 07/04/66-07/13/68 Behannon et al, 1968 IMP 4 (34) Ness 05/26/67-12/27/68 Fairfield, 1969 AIMP 2 (35) Ness 07/26/67-11/10/69 Ness et al, 1967 HEOS (1) Hedgecock 12/11/68-10/28/75 Hedgecock, 1975 IMP 5 (41) Ness 06/21/69-10/26/72 Fairfield & Ness, 1972 IMP 6 (43) Ness 03/14/71-07/21/74 Fairfield, 1974 IMP 7 (47) Ness 09/26/72-04/03/73 Mish & Lepping, 1976 IMP 8 (50) Ness, Szabo 10/30/73-05/12/00 Mish & Lepping, 1976 ISEE 3 (13) E.Smith 08/14/78-12/21/82 Frandsen et al, 1978 Prognoz 10 (10) Yeroshenko 04/27/85-11/04/85 Styazhkin et al, 1985 Wind (51) Lepping, Szabo 11/21/94-current Lepping et al, 1995 ACE (71) Smith 02/06/98-current Smith et al, 1998. Geotail (60) Nagai 05/08/95-12/31/06 ----------- ------ ----------------- ------------------Full citations for these references are given at: https://omniweb.gsfc.nasa.gov/html/omni2_doc_addition.html#references.
The web pages of the IMP 8, Geotail, Wind and ACE magnetometer teams are to be found at:
IMP 8: https://spdf.gsfc.nasa.gov/pub/data/imp/imp8/mag/
Wind: https://wind.nasa.gov/data/mfi/
ACE: http://www.srl.caltech.edu/ACE/ASC/level2/index.html
Geotail: http://cdaweb.gsfc.nasa.gov/
Of special relevance to LRO preparation is an FTPBrowser-accessible merged hourly IMP8-Geotail-Wind-ACE IMF data set at https://omniweb.gsfc.nasa.gov/ftpbrowser/mag_iwa.html from which one may make overlapping time-series plots. A second interface at https://omniweb.gsfc.nasa.gov/ftpbrowser/mag_iwa_s2.html enables one to make scatter plots and linear regression fits of user-selected parameter pairs and time span. Results of analyses of these data, with this latter tool, are reported below. A third interface at https://omniweb.gsfc.nasa.gov/ftpbrowser/mag_iwa_d.html enables one to determine distributions, means and their standard deviations, and medians of any IMF parameter from any of the spacecraft named, for any time span.
Most of the solar wind plasma data used in LRO are from the MIT Faraday Cups ( PI is Bridge in Table 2) or the Los
Alamos National Laboratory (LANL) electrostatic analyzers ( PI is Bame in Table 2). The data were mainly provided
to NSSDC or SPDF and used in OMNI as 1-hour averages.
Exceptions are:
1. The IMP 1, Vela and HEOS data which were provided as 3-hour averages and were assigned to each of three
successive one-hour records in OMNI,
2. The ISEE 3, Wind and ACE data whose 1-hour averages were computed at SPDF from time-shifted higher-resolution and
3. The LANL IMP 6, 7 and 8 data whose 1-hour averages were computed at SPDF from higher-resolution data.
At present time, Wind and ACE data were being periodically added to OMNI.
Information on current latest date of plasma data in OMNI is given at https://omniweb.gsfc.nasa.gov/html/ow_data.html
Table 2 -------- Spacecraft Key persons Time span Comments, Reference ---------- ----------- ---------------- -------------------- IMP 1 (18) Bridge 11/27/63-02/22/64 Bridge et al, 1965 Merged Vela (97) Bame 07/21/64-03/18/71 Bame et al, 1971 Vela 3 (3) Bame 07/26/65-11/13/67 Hundhausen et al, 1967 AIMP 1 (33) Bridge 07/06/66-09/23/69 Lyon et al, 1968 IMP 4 (34) Ogilvie 06/03/67-12/16/67 Ogilvie et al, 1968 AIMP 2 (35) Bridge 07/28/67-07/03/68 Lyon et al, 1967 OGO 5 (5) Neugebauer 03/05/68-04/29/71 Neugebauer, 1970 HEOS 1 (1) Bonetti 12/11/68-04/15/70 Bonetti et al, 1969 IMP 6 (43) Bame 03/18/71-07/21/74 Feldman et al, 1973 IMP 7 (44) Bame 10/06/72-09/29/78 Asbridge et al, 1976 IMP 7 (47) Bridge 01/03/75-09/20/78 Lazarus et al, 1998 IMP 8 (45) Bame 11/04/73-07/16/00 Asbridge et al, 1976 IMP 8 (50) Bridge 12/05/73-07/26/01 Lazarus et al, 1998 ISEE 1 (11) Bame 10/30/77-12/19/79 Bame et al, 1978b ISEE 3 (13) Bame 08/16/78-10/12/82 Bame et al, 1978a Wind (51) Lazarus and Kasper 01/01/95-current Kasper, 2002 ACE (71) McComas, R. Skoug 02/05/98-current McComas et al, 1998 Geotail (60) L.Frank 05/08/95-12/07/06Additional key scientists contributing to IMP 8 plasma data are have been J. Gosling and J. Steinberg at LANL and A. Lazarus, K. Paularena and J. Richardson at MIT.
N V T phi-V theta-V alpha/prot IMP 6 x x x x x IMP7 (LANL) x x x x x IMP7 (MIT) x IMP8 (LANL) x x x x x IMP8 (MIT) x x x x x ISEE 1 x ISEE3 (protons) x x x x ISEE3 (electrons) x x Wind/SWE x x x x x x ACE/SWEPAM x x x x x x Geotail x x x x xWind SWE plasma parameter data are available in three separate data sets created by the Principal Investigator team.
Previously we used cross-normalized Wind/SWE KP to the definitiveSWE/NLF data, and we used cross-normalized ACE data thereafter. Now ( as 2019-03-31), we use for 1995-current the Wind definitine NLF SWE data and cross-normalized SWE KP data thereafter. and at the third priority we used cross-normalized ACE data.
92s proton and alpha particle NLF parameters, and proton MOM parameters, are available for solar wind intervals only, at https://omniweb.gsfc.nasa.gov/ftpbrowser/wind_swe_2m.html, and at https://omniweb.gsfc.nasa.gov/ftpbrowser/wind_swe_2mp.html for all orbit phases. Protons-only KP data are available for solar wind intervals only, at https://omniweb.gsfc.nasa.gov/ftpbrowser/wind_swe_kp.html and at https://spdf.gsfc.nasa.gov/pub/data/wind/swe/ascii/swe_kp_unspike/ The ACE/SWEPAM parameters provided by the SWRI/LANL plasma team were determined by taking moments over distribution functions. Additional interfaces for comparing Wind/SWE NLF and KP data to each other and to ACE/SWEPAM, IMP 8 (LANL and MIT) and Geotail are at https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_iwa.html time series plots, lists https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_iwa_s2.html 2-spacecraft scatter plots https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_iwa_s3.html sctr plots, log N&T https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_iwa_d.html statistics w. filteringReaders interested in the differences between the Wind moments-based and NLF-fits-based parameter-determination approaches may access https://omniweb.gsfc.nasa.gov/ftpbrowser/wind_swe2m_s.html
The LANL plasma instruments on ISEE 3 measured ions and electrons separately. The ion instrument failed February 19, 1980. Electron-based flow speeds and densities were used in OMNI 2 after the ion instrument failure until late 1982, but neither electron-based temperatures nor flow direction angles were included into OMNI 2. (This was also done for OMNI years ago.) It should be noted that on two days (July 4,1979, and July 31, 1979), ISEE 3 measured densities so low that for each of several hours, the hourly averaged density was less than 0.05/cc. Given OMNI's use of F6.1 format for densities, this yields an apparent density of 0.0 in OMNI for these few hours.
Only flow speeds are provided from IMP 7 (MIT) and from ISEE 1. In the former case, this limitation to flow speed was at the suggestion of A. Lazarus at MIT. In the case of ISEE 1, there were too few hours (<240) when ISEE 1 data were used in OMNI 2 (only when no other data were available) to prioritize doing new density and temperature normalizations.
Web pages of the primary contributors of recent plasma data to LRO are at:
IMP8/MIT: https://spdf.gsfc.nasa.gov/pub/data/imp/imp8/plasma_mit/ IMP8/LANL: https://spdf.gsfc.nasa.gov/pub/data/imp/imp8/plasma_lanl/ Wind/SWE: https://spdf.gsfc.nasa.gov/pub/data/wind/swe/ascii/2-min/ (definitive) Wind/SWE: https://spdf.gsfc.nasa.gov/pub/data/wind/swe/ascii/swe_kp_unspike/ ( Kp parameters) ACE/SWEPAM: https://izw1.caltech.edu/ACE/ASC/level2/ Geotail: http://cdaweb.gsfc.nasa.gov/As with the magnetometer data addressed earlier, hourly and higher resolution plasma data are available via multiple pathways, mostly cited on the foregoing web pages. They are available via ftp from https://spdf.gsfc.nasa.gov/pub/data/ and with display and subsetting capabilities via FTPBrowser and/or CDAWeb at https://omniweb.gsfc.nasa.gov/ftpbrowser/ and https://cdaweb.gsfc.nasa.gov/ Several multiple-source hourly data sets were created at SPDF to aid in data checking and cross-normalization. These are discussed in the "Data cleaning" section to follow and at https://omniweb.gsfc.nasa.gov/ftpbrowser/merged.html.
It is desirable that LRO data be as free of "bad data" as possible. Extensive checking of 1971-current magnetic field and plasma data was carried out at NSSDC and SPDF as part of creating the LRO data set. Several web-based tools were created and used to review input data sets individually and as compared to each other.
There are two sources of "bad data" in LRO. One is "noise points" in constituent data sets that may arise from transient instrument malfunction or, in the case of plasma parameters, from the time variation of plasma during the accumulation of one distribution function whose subsequent analysis for determining bulk parameters yields meaningless values. Such noise points typically yield single-point upward or downward spikes in parameter profiles. While instrument teams have removed most such points in the data they provided to NSSDC and SPDF, it has been beneficial to seek out and eliminate such points here.
The other main source of bad data in LRO is the inappropriate inclusion of magnetosheath field or plasma data in a data set intended as solarwind-only. This is more significant, the more times the source spacecraft crosses the Earth's bow shock. Thus it is insignificant for ACE which went into an upstream libration point orbit very shortly after launch, very significant for IMP 8 in its ~12-day geocentric orbit, and significant to an intermediate extent for Wind with its more complex and time- varying orbit.
The data sets provided to NSSDC and SPDF and used in LRO were nominally for solar wind periods only. The exceptions are: IMP 8 hourly data were submitted time continuously, and solar wind portion were extracted using the bowshock data base at https://omniweb.gsfc.nasa.gov/ftpbrowser/bowshock.html. and Geotail for which we established conservative solar wind intervals.
Among the tools developed and used for concurrently screening multi-source data and summarized at https://omniweb.gsfc.nasa.gov/ftpbrowser/merged.html were:
https://omniweb.gsfc.nasa.gov/ftpbrowser/mag_iwa.html
for plotting magnetic field intensity or components from IMP 8, Wind and ACE for 1994-2000;
https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_iwa.html
for plotting plasma parameters and/or variances from any pair of the 5 data sets IMP8/MIT,
IMP8/LANL, Wind/SWE (fits-based), Wind/SWE (moments-based) or ACE/SWEPAM for 1995-2001;
https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_iwa.html
for plotting plasma parameters and/or variances from IMP8/MIT and IMP8/LANL for 1973-2001;
https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_ii.html
for plotting plasma parameters and/or variances from IMP8/MIT, IMP8/LANL and ISEE 3 for 1978-1982;
https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_imp_678.html
for plotting plasma parameters and/or variances from IMP6/LANL, IMP7/LANL and IMP8/LANL for 1971-1978
These tools all work with time-shifted (see below) hourly-averaged data. They yield plots with one panel per physical parameter selected,
with color-coded intensity-time profiles from each of the data sources. They make noise points visible and they make intervals visible
when the apparent solar wind behavior at multiple sources differs significantly. Some cases of the latter correspond to one source being
magnetosheath-contaminated while other cases may correspond to real differences in the solar wind plasma domains seen at the two spacecraft.
Another family of tools was also developed that generates scatter plots of parameter values from various pairs of plasma data sources. (These tools also determine regression fits as will be further discussed in the later data comparison and cross- normalization sections of this wtiteup.) This set of tools makes outliers very visible and has led to identification of several magnetosheath-contaminated data-hours. These tools include:
https://omniweb.gsfc.nasa.gov/ftpbrowser/mag_iwa_s2.html
for 1994-latest_available IMP 8, Wind, ACE and Geotail magnetic field parameters
https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_iwa_s2.html
for 1995-2001 IMP 8, Wind and ACE plasma parameters
https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_lm_s2.html
for 1995-latest_available IMP 8, Wind, ACE and Geotail plasma parameters
https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_ii_s2.html
for 1978-1982 IMP8/MIT, IMP8/LANL and ISEE 3 plasma parameters.
https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_imp_678_s2.html
for 1997-1998 LANL IMP 6, 7 and 8 plasma parameters.
Replacing the "s2" in these url's with "s3" in the last four of these gives a variant of the pages for working with base-10 logarithms of
densities and temperatures rather than with densities and temperatures themselves. These tools allow filtering by values of any of the
parameters in the relevant data records, including numbers of fine scale points in the hour-averages. The second of them also allows
filtering by the impact parameter (transverse separation distance, see below) between any pair of spacecraft.
For many years, the IMP 8 spacecraft was the only LRO source, and was the dominant OMNI/LRO data source from its late-1973 launch to the mid-1978 ISEE 3 launch and again from the late-1982 departure of ISEE 3 from an L1 orbit until the late-1994 Wind launch. In its 12-day, 35-Re near-circular geocentric orbit, IMP made at least 2 and frequently 10-20 transitions into and out of the solar wind, across the Earth's time-varying bow shock.
To enable a more reliable exclusion of magnetosheath-contaminated IMP 8 field or plasma data, and a more reliable inclusion of interesting solar wind intervals (that might once have been excluded by the magnetic field or plasma teams in their SPDF and NSSDC submissions of hourly solar wind data as being magnetosheath-contaminated), a major effort was undertaken (with support from a NASA/AISRP grant) by the IMP 8 magnetic field team at GSFC and the plasma team at MIT to jointly study the field and plasma data and to identify and characterize all IMP 8 bow shock crossings. The fruits of this effort for 1973 to 2000 are visible at https://omniweb.gsfc.nasa.gov/ftpbrowser/bowshock.html. We have used this file to identify and delete magnetic field or plasma data when IMP 8 was not wholly in the solar wind. (The exception was that, for the case of LANL plasma data wherein hourly averages were created from ~2-min data previously separated at LANL as being in the solar wind vs. magnetosheath, LANL hourly averages were retained in OMNI 2 for hours in which IMP encountered shock crossings and was therefore partly in the solar wind.)
In this section we address why, when and how we time shift data of ~minute resolution before building hourly averages for inclusion in OMNI 2.
Why and when to shift: That most of the source spacecraft contributing to LRO make IMF and plasma observations minutes upstream of the magnetosphere (e.g., <= 15 minutes for the moon-orbiting, late-1960's Explorer 35 spacecraft at ~60 Re) was not factored into the hourly averages interspersed into LRO. However, the ISEE 3, Wind and ACE spacecraft are frequently or always about an hour upstream of the magnetosphere. As their data are to be interspersed with data from much-closer-to-Earth spacecraft (e.g., IMP 8), it is appropriate to time-shift the hour-upstream data at higher resolution and to compute hourly averages "at Earth" for inclusion in LRO. Such shifting has been done for the field and plasma data of these three spacecraft, as described herein.
How to shift: Several factors determine optimal shifts: the geometry of the Earth- spacecraft separation vector; the Earth's orbital motion about the sun between observations upstream and at Earth; the geometry (shape, orientation) of the solar wind variation phase front; the solar wind flow direction; and local propagation of the phase front relative to the mean solar wind. (In the above, "Earth" can be replaced by "second spacecraft" for time shifts made for two-spacecraft comparisons.) However, for the purpose of shifting many years of upstream data for LRO, we seek a statistically optimal approach. Relative to the above factors, we assume the variation phase fronts are planar, of arbitrarily large extent normal to the Sun-Earth line and normal to the ecliptic, and that they merely convect outward with a solar wind flow assumed radial. It remains to specify the angle between the Sun-Earth line and the intersection between the phase front and the ecliptic plane.
It is useful to introduce the concept of impact parameter (IP) as the distance by which a plasma element, flowing radially from the sun with speed V and observed by one spacecraft misses being seen by a downstream spacecraft (or Earth). Simple geometrical considerations show that for bodies indexed by i and j and located at (Xi, Yi, Zi) and (Xj, Yj, Zj),
IPij = SQRT {[(Yi-Yj)+(Xi-Xj)*Ve/V]**2 + (Zi-Zj)**2}
Time-series plots of IPij for various combinations of Earth, IMP 8, ISEE 3, Wind and
ACE are available (given that Ve = 30 km/s and assuming V = 390 km/s) at
https://omniweb.gsfc.nasa.gov/ftpbrowser/impact_ii.html
and at
https://omniweb.gsfc.nasa.gov/ftpbrowser/impact.iwag.html.
IP values were used as filters in doing data set pair regressions
For solar wind variation phase fronts normal to the ecliptic (no Zi-Zj dependence),
geometric considerations say that the time delay equation for one spacecraft and Earth is
Delta-t = (X/V) * {[1 + (Y*W)/X]/[1 - Ve*W/V]},
where
Delta-t is the time shift in seconds,
X and Y are GSE X and Y components of the spacecraft position vector, in km,
V is the observed solar wind speed in km/s (assumed radial),
Ve is the speed of the Earth's orbital motion (30 km/s).
W=tan [0.5 * atan (V/428)] is parameter related to the assumed orientation of the phase front relative
to the Earth-sun line. It is Half-way between corotation geometry and convection geometry.
Doing the time shifts: We have shifted 1-5 min ISEE 3, Wind and ACE IMF and plasma data using the above time-shift equation, using known locations of those spacecraft and using observed solar wind flow speeds in the data sets being shifted. We then created averages over all fine scale values whose shifted time tags placed them within a given hour "at Earth." Thus all the values with shifted time tags between 00:00 and 01:00 were averaged to give the first OMNI 2 average for a day.
The upstream orbits: Let us review the ISEE 3, Wind and ACE orbits briefly. From shortly after its 8/12/78 launch until August, 1982, when it was directed towards the Earth's deep magnetotail, ISEE 3 was in an L1 libration point orbit with X in the range ~200-260 Re, Y in the range ~ +/- 100 Re, and Z in the range ~ -15 Re to + 20 Re. At its extremes (X ~ 220 Re, Y ~ +/- 100 Re, Z ~ 0), the impact parameter (IP, see above) values for ISEE 3 relative to Earth were ~ 83 Re and ~117 Re, where the asymmetry results from the Earth's motion towards -Y during the ~hour that the solar wind moves from Xisee to Xearth. Note that the time shifts for ISEE 3 could range between ~25 min for high flow speed (700 km/s) and Ygse = -100 Re and ~ 80 min for low speed (350 km/s) and Ygse = +100 km/s.
Wind has been in a variable orbit since its 11/01/94 launch. Through 1998, Wind executed a series of ~30 geocentric orbits with near-noon apogees of distances ranging between ~50 Re and ~250 Re and periods ranging between ~20 days and ~150 days. During these years, the Y component of the Wind position vector was typically in the range +/- 40 Re and almost never exceeded the range +/- 60 Re. For 1999 through the first half of 2000, Wind had three orbits reaching X values of 210, 180 and 100 Re, but otherwise many Wind apogees were of lower altitude and well away from the noon meridian. Starting in mid-2000, Wind was put into an orbit reaching extreme values of +/- 250-260 Re in the dawn-dusk meridian. After some time in this orbit, Wind was placed in an L1 orbit. Figure 4 shows the Wind-Earth impact parameter for 1994-2003
ACE has been in a regular L1 orbit since shortly after its 08/25/97 launch, with X in the range ~218-248 Re, Y in the +/-40 Re range and Z in the +/- 24 Re range. The ACE project was assessing orbit adjustments in 2003.
The high resolution data sets that were fed into the time shift algorithm were:
ISEE 3 2-min merged IMF/plasma data at
https://omniweb.gsfc.nasa.gov/ftpbrowser/isee3_merged.html
Wind/SWE 92-s plasma data at
https://omniweb.gsfc.nasa.gov/ftpbrowser/wind_swe_2m.html
Wind 1-m IMF data at
https://spdf.gsfc.nasa.gov/pub/data/wind/mfi/ascii/1min_ascii/
ACE 4-min merged IMF/plasma data at
https://omniweb.gsfc.nasa.gov/ftpbrowser/ace_merge.html.
Geotail mag. data were processed from 15 sec. data, as a part of HRO preparation
and they are accesiible from https://omniweb.gsfc.nasa.gov/ftpbrowser/geotail_mag15s.html
Geotail plasma data were processed from: http://cdaweb.gsfc.nasa.gov/ (GE_H0_CPI)
(for details see HRO preparation at https://omniweb.gsfc.nasa.gov/html/omni_min_data.html)
For ISEE 3, a given field-plasma-merged record was given a shifted time tag only if it had a flow speed value to use in the time shift equation above. If the record had no flow speed value, then its IMF data, if present, were not shifted nor otherwise carried forward for inclusion in OMNI 2. However, for both ACE and Wind, IMF data were shifted using a flow speed interpolated to the IMF record time tag with input from the closest-before and closest-after good flow speed values, regardless of the duration between the two input points used. (The treatment of ACE data in this regard was changed from being ISEE-3-like to being Wind-like in February, 2006.) Since plasma gaps may have been over many hours, users of shifted IMF data may want to assess the goodness of their time tags by examining whether there are concurrent plasma data and, if not, how long a plasma gap (during which flow speeds might have varied significantly) there was.
For OMNI 2, we shifted each ISEE 3 electron- based density and flow speed in the LANL-provided hourly data set by one hour. No new "half-way" time shift of these electron-based parameters was done.
The hourly averages determined from the shifted field and plasma ISEE 3, Wind and ACE data are available, along with concurrent but unshifted IMP 8 data, at https://omniweb.gsfc.nasa.gov/ftpbrowser/merged.html.
There are random and systematic differences between hourly averages of pairs of like parameters obtained by two spacecraft. Among the reasons for the random differences may be (1) the two averages have differently time-located gaps in the averages, (2) spatial gradients in parameters being measured combined with offsets of the spacecraft locations relative to the flow direction, (3) incorrect (or no) time shifts used for one or another data set prior to hourly-average construction (see prior section), (4) etc. Among the reasons for systematic differences are differing processing approaches (e.g., taking fits vs. moments for deriving flow parameters from distribution functions), subtle calibration factors not adequately accounted for in data processing, etc.
As OMNI 2 involves the interspersal of IMF data and of plasma data from each of several spacecraft, it is desirable to understand and to compensate for the differences between pairs of sources. It is not feasible to decrease random differences between pairs of sources (except via identification and exclusion of "bad data" as discussed earlier), but it is valuable to understand their magnitude in order to understand the "accuracy" of the OMNI 2 data as representative of the nearby solar wind. It is feasible to find and compensate for systematic differences between pairs of data sets.
13.1 Magnetic field comparisons:
Using the scatter plot and regression fit interface at
https://omniweb.gsfc.nasa.gov/ftpbrowser/mag_iwa_s2.html, we have done several runs of the
form Bi,j = a + b * Bi,k, where i designates a field component (GSE X, Y, Z) or field
magnitude ( <|B|>), where j, k designate a spacecraft pair and
where a and b are intercept and slope of a linear regression fit determined by
minimizing sums of squares of perpendicular distances between (Bi,j, Bi,k) data points
and the best fit line. Use of the "perpdist" regression approach rather than the
"delta-Y" regression approach is more appropriate to cases where the uncertainties or
errors in the Y and X variables are comparable. In all the runs, we required at least
half an hour's coverage in each hourly average.
All details are discussed at https://omniweb.gsfc.nasa.gov/html/omni2_doc_old.html
Summarizing of the magnetic field comparisons results we have:
In the range +/- 10 nT, where most IMF values lie, the difference between an observed
value and any of the values computed from the above equations is almost always within
0.2 nT of zero. 0.2 nT is much less that the natural spread of data points about the
best fit regression lines so we shall not perform any cross-normalizations of magnetic field data.
It was determined that the only IMF normalization needed for Geotail and Prognoz-10 data
Magnetic field normalization for Geotail :
The Geotail magnetic field data we worked with had preliminary and incorrect Bz offset values.
Accordingly, we compared Geotail data with data from the other spacecraft and derived the
following "normalizations" of the Geotail data:
Bx and By, all time, all Bz: Bx(norm) = 1.02 * Bx(obsvd) By(norm) = 1.02 * By(obsvd) Bz (depends on time) 19950101-19951231: Bz(norm) = -0.490 + 1.004 * Bz(obsvd) 19960101-19991231: Bz(norm) = -0.597 + 1.017 * Bz(obsvd) 20000101-20040401: Bz(norm) = -0.149 + 1.019 * Bz(obsvd) 20040402-20050401 : Bz(norm) = -0.461 + 1.020 * Bz(obsvd) 20050402-20051231: Bz(norm) = -0.663 + 1.023 * Bz(obsvd) Bt (depends on time and on sign of Bz) 19950101-19991231, Bz<0: Bt(norm) = 0.123 + 1.022 * Bt(obsvd) 19950101-19991231, Bz>0: Bt(norm) = -0.180 + 1.012 * Bt(obsvd) 20000101-20040401, Bz<0: Bt(norm) = 0.052 + 1.016 * Bt(obsvd) 20000101-20040401, Bz>0: Bt(norm) = -0.021 + 1.014 * Bt(obsvd) 20040402-20051231, Bz<0: Bt(norm) = 0.123 + 1.022 * Bt(obsvd) 20040402-20051231, Bz>0: Bt(norm) = -0.180 + 1.012 * Bt(obsvd)Magnetic field normalization for Prognoz:
13.2 Plasma parameter comparisons:
We use the same approach to comparing multi-source
plasma flow speed, density and temperature values as was used for IMF parameters.
For plasma we have four multi-source data sets:
1971-1978 LANL IMP6/IMP7/IMP8 data;
1973-2001 IMP8 MIT/LANL data;
1978-1982 IMP8/MIT/LANL-ISEE3/LANL data;
1995-present IMP8/MIT-IMP8/LANL; Wind/SWE/fits; ACE/SWEPAM; Geotail data.
The relevant interfaces for both scatter plots and regression fits and for overlying
intensity-time profiles are at https://omniweb.gsfc.nasa.gov/ftpbrowser/merged.html
It is likely that comparisons among currently active
Wind/SWE and ACE/SWEPAM plasma data sources will be of most current interest.
Only the SWE/NLF ( Non-Linear Fits) set was directly compared to the ACE data,
as this set is believed to be significantly more reliable by the SWE team.
Owing to the significant differences between Wind/NLF and ACE values, for both densities and temperatures,
cross normalization of ACE values to equivalent Wind values were performed in creating the OMNI 2 data set.
That the Wind/SWE plasma data set was chosen as the baseline was the result of analysis at MIT
comparing fits-based proton densities and alpha particle densities, plus a model-based contribution
for electrons from higher-Z species, with total electron content from the independent Wind/WAVES instrument.
From this analysis the uncertainty in the SWE proton density was estimated as 2%.
Finally, "physics-based" tests of the goodness of the nonlinear fits (NLF)-based velocities (~0.16% in speed, ~3 deg in direction),
densities (~3%)and temperatures (~8%) are discussed in
(Kasper, 2006, see https://omniweb.gsfc.nasa.gov/html/HROdocum.html#6).
So,for plasma comparisons, we used P(Wind/NLF) = a + b * P(2) where now P(2) might be ACE or IMP 8 or Wind/KP, and where a and b are the intercepts and slopes in the equations and NLF- nonlinear fit data
We have not systematically regressed flow direction angles (Users may make comparisons of such parameters from the https://omniweb.gsfc.nasa.gov/ftpbrowser/merged.html interface.)
While we have done both linear (the "_s2" interfaces) and logarithmic (the "_s3"
interfaces) regressions ("logarithmic regression" is shorthand for "linear
regressions of logs of parameters") for density (N) and temperature (T), we have normalized
densities and temperatures using the results of the logarithmic regressions because
densities and temperatures tend to be more log-normally distributed than linearly
distributed.
The normalization parameters will be specified as pairs (a b)
(logN)norm = a + b * (logN)obsvd
(logT)norm = a + b * (logT)obsvd
We showed that, with rare exceptions, flow speed regression lines are typically within a few km/s of the Y = X line over the 300-800 km/s range, so we have not normalized any flow speed data.
Our interfaces also allow one to filter the data used in a given regression run by the numbers of fine scale points in the hourly averages and by the "impact parameter" IP for the pair of spacecraft contributing data to the run. The IP is the transverse separation of the spacecraft pair. IP's are available for IMP8-ISEE3, IMP8-Wind, IMP8-ACE and Wind-ACE from https://omniweb.gsfc.nasa.gov/ftpbrowser/impact_iwag.html and from https://omniweb.gsfc.nasa.gov/ftpbrowser/impact_ii.html. Virtually all IP-relevant runs were done with IP<60 Re to minimize basing comparisons and subsequent cross- normalizations on plasma parameters from different plasma regimes. The filtering on numbers of fine scale points enabled us to minimize the effects of hours wherein hourly averages may be based on limited and different coverages during an hour.
We note that solar wind densities are expected to decrease as 1/R**2 on average, with R the heliocentric distance. The L1 libration point at 200+ Re from Earth is close to 0.99 AU from the sun. This means the density of a plasma element measured at L1 should be decreased by ~ 2% when it reaches the Earth's magnetosphere at ~1.00 AU. We have not used this fact in our analysis, but we note that the density differences we find in comparing sources are typically greater than 2%.
The comparisons among currently active Wind/SWE and other plasma data sources gave us following results: -----------------------------------
Normalizing Wind/SWE Kp data to the Wind/SWE/NLF
Fist we normalized SWE KP data (for 1995-current) to the SWE/NLF data (that is basic data)
Summarized the new results 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) = -0.30 + 1.055 * LogT(Wind/KP, obsvd)
For Tp, for all V and for >= 1998,
LogT(Wind/KP, norm) = LogT(Wind/KP, obsvd)
-------------------------------------------------
Normalizing ACE/SWEPAM data to Wind/SWE/NLF :
Summarizing ACE/SWEPAM Np and Tp data to the SWE/NLF we have:
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 395 < V < 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)
(Important Note: 11-06-2018 We removed ACE Alpha/Proton density Ratio
from OMNI Data sets for all years , because there was a very poor
correlation between the Wind/SWE/NLF Alpha/Proton density ratios and ACE/SWEPAM.
We have been got complains about unreliable ACE Na/Np parameter from our users also.
Users may look at such kind of differences comparing Alpha/Proton density from Wind
and ACE at https://omniweb.gsfc.nasa.gov/ftpbrowser/merged.html.)
(Important Note 2: 03-20-2019 we added Wind/SWE/NLF Alpha/Proton density ratios
to the records where ACE ratios were removed, (see previous Note).
(Important Note 3: At 2021 year the ACE SWEPAM
plasma data were reproceesed by people from ACE data center for 2013-present
( see https://izw1.caltech.edu/ACE/ASC/DATA/level2/swepam/swepam_release_notes)
This reprocessing took into accounts additional detectors and improved the density
values calculated from SWEPAM plasma data.
So, we checked our coeff of cross-normalization ( 2013-present) for plasma data
and found that the coeff. started from 2019 should be changes as:
For Np, for all V for 2019-2021,
LogN(ACE/SWEPAM, norm) = -0.010 + 1.006 * LogN(ACE/SWEPAM, obsvd)
For Tp, for all V and for 2019-2020,
LogT(ACE/SWEPAM, norm) = 0.266 + 0.947 * LogT(ACE/SWEPAM, obsvd) )
-----------------------------------------------------------------
Normalizing Geotail/CPI data to Wind/SWE/NLF
For Geotail, we use:
Density (all time and all V): LogN(norm) = -0.072 + 0.980 * LogN(obsvd)
Temperature (1995-1998, all V): LogT(norm) = 0.166 + 0.925 * LogT(obsvd)
Temperature (1999-2005, all V): LogT(norm) = -0.362 + 1.052 * LogT(obsvd)
No Na/Np Ratio for this instrument
--------------------------------------------------------------------------
Normalizing IMP8/MIT and IMP8/LANL data to Wind/SWE/NLF
IMP 8 plasma data span a 28-year, 1973-2001 interval. We report herein the results of
comparisons of IMP8/MIT, IMP8/LANL and Wind/SWE data. We shall also use the flow speed
bins <350 km/s, 350-450 km/s and >450 km/s in performing normalizations. Another key
assumption is that there has been no significant time variation in IMP8/MIT density and
temperature not previously found and compensated for by the MIT team. This enables us to
normalize IMP-8/MIT to Wind/SWE data and then to normalize all other data sources
(not contemporaneous with Wind/SWE) by chaining the regressions of each such data set to
IMP 8 with the IMP8-Wind/SWE regressions.
Normalizing IMP8/MIT Density and Temperature to Wind/SWE/NLF
Normalization coeff. a and b for IMP8/MIT for entire time interval to Wind/SWE for different
bins are given below:
V<=350. V>350 and V<=450 V>450
N: (.020 .941) (.033 .919) (.019 .907)
T: (.864 .839) (.491 .920) (.702 .890)
No Na/Np Ratio for this instrument
Normalizing IMP8/LANL Density, Temperature, and Na/Np Ratio to Wind/SWE/NLF
We obtained time dependent normalization coeff. a and b for IMP8/LANL
to Wind/SWE/NLF, finding normalization coeff IMP8/LANL to IMP8/MIT for each LANL group of years:
If a" and b" normalization coeff IMP8/MIT to IMP8/LANL: Log(Nlan)=a"+ b"*Log(Nmit)
( see Appendix 3 in omni2_doc_old.html) then the coeff. a' and b' for IMP8/LANL to IMP8/MIT
will be: Log(Nmit)=a'+ b'*Log(Nlan) then we have Log(Nmit)=[Log(Nlan)-a")]/b" ,
where a'=-a"/b"; b'= 1/b";
And then we normalised obtained data data to Wind/SWE/NLF.
The normalization coeff. a and b for IMP8/LANL to Wind/SWE/NLF are:
Normalization for Density
Year V<=350. V>350 and V<=450 V>450
1973-1979 (.111 .943) (.064 .951) (-.011 .958)
1980-1981 (.140 1.024) (.092 1.010) (-.028 1.048)
1982-1994 (.064 .965) (-.020 1.000) (-.085 1.006)
1995-2001 (.040 1.007) (-.023 1.013) (-.093 1.022)
Normalization for Temperature
1973-1979 (.621 .879) (.290 .958) (.271 .969)
1980-1981 (.840 .811) (-.482 1.091) (.207 .964)
1982-1994 (.497 .894) (+.044 .997) (.130 .982)
1995-2001 (.441 .895) (-.044 1.008) (-.165 1.036)
Normalization for Na/Np ratio
We found Coefficient X-normalization of alpha/proton ratios for IMP 8 to Wind:
Na/Np(norm) = 0.78 * Na/Np(obsvd)
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Normalizations for IMP6, IMP7 to WIND/SWE/NLF
There were LANL plasma instruments on IMP 6 (1971-1974) and IMP 7 (1972-1978)
First we normalized IMP6/LANL or IMP7/LANL to IMP8/LANL with coeff Ax and Bx that we got using
interface: https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_imp_678_s3.html
and then we
normalised rezults from previous step to Wind SWE using coeff. for IMP8/LANL to Wind/SWE.
(with help of interface: https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_iwa_s3.html)
In this case our equations looks like:
log(Ni)=Ax + Bx*log(Nx)
where
log(Nx)-Log of density of X spacecraft, X=IMP6 or IML7, or ISEE3
log(Ni)- Log of density normalized to IMP8/LANL,
Ax, Bx coeff of normalization X- spacecraft to IMP8/LANL,
then we normalized to Wind:
log(Nw)=Ai + Bi*Log(Ni)
where Ai, Bi coeff of normalization IMP8/LANL to Wind/SWE.
log(Nw)- Log of density normalized to Wind/SWE,
last equation can be modified:
log(Nw)=Ai+Bi*(Ax + Bx*log(Nx)) or log(Nw)=Ai+Bi*Ax +Bi*Bx*Log(Nx)
final: log(Nw)=Aw+Bw*Log(Nx),
Aw= Ai+Bi*Ax; Bw=Bi*Bx
Coeff. Aw and Bw for Density and Temperature for IMP6/LANL are given in the table:
V<=350. V>350 and V<=450 V>450
Aw Bw Aw Bw Aw Bw
N: (.000 1.075) (.037 1.007) (.018 .952)
T: (.509 .894) (.308 .950) (.560 .910)
Coeff. Aw and Bw for Density and Temperature for IMP7/LANL are given in the table:
V<=350. V>350 and V<=450 V>450
Aw Bw Aw Bw Aw Bw
N: (-.050 .983) (-.053 .967) (-.099 .968)
T: (.641 .872) (.359 .942) (.322 .957)
Normalizing of IMP6/7 LANL Na/Np ratios to Wind/SWE/NLF Na/Np ratio:
Analysis shows there is no need to normalizing IMP 6 or IMP 7 to IMP 8 and then to Wind
because the Na/Np from IMP6 and IMP7 approximately [statistically] equals Na/Np from IMP 8
(See https://omniweb.gsfc.nasa.gov/ftpbrowser/pla_imp_678_s2.html) and the equation is:
Na/Np(norm) = 0.78 * Na/Np(obsvd) ( the same as for IMP8 for Wind )
---------------------------------------------------------------------------
Normalizations for proton and electron from ISEE3 to WIND/SWE/NLF
ISEE 3 (1978-1982) was a very significant near-Earth solar wind monitor from shortly after its
1978/08/12 launch until late 1982 when it was moved from its L1 orbit to probe the deep geomagnetic tail.
The LANL plasma experiment on ISEE 3 separately measured ions and electrons.
Unfortunately the ion instrument failed on February 19, 1980. We include in OMNI 2 (as
we did for OMNI) ion-based density, flow speed, temperature and flow azimuth information
through 1980/02/19, but only electron-based density and flow speed thereafter.
Further details see Appendix 4 at https://omniweb.gsfc.nasa.gov/html/omni2_doc_addition.html
that shows the results of comparisons of IMP 8 data with ISEE 3 ion-based and electron-based parameters.
Coeff. Aw and Bw for Density and Temperature of ISEE3/Proton data to Wind/SWE/NLF:
( See previous section for calculations of Aw, Bw)
V<=350. V>350 and V<=450 V>450
Aw Bw Aw Bw Aw Bw
N: (.059 .855) (.097 .911) (.076 .972)
T: (.348 .926) (.007 1.000) (-.053 1.016)
-----------------------------------------------
The normalization equations for Density of ISEE3/Electron data to Wind/SWE:
V<=350. V>350 and V<=450 V>450
N: (.019 .888) (.052 .842) (.004 .859)
--------------------------------------------
Appendixes 1-5 at https://omniweb.gsfc.nasa.gov/html/omni2_doc_old.html
contains the some more details of comparisons across different spacecraft pairs
(specially for old spacecraft).
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The best citable reference to OMNI data is J.H. King and N.E. Papitashvili,
Solar wind spatial scales in and comparisons of hourly Wind and ACE plasma
and magnetic field data, J. Geophys. Res., Vol. 110, No. A2, A02209,
10.1029/2004JA010649.
https://doi.org/10.1029/2004JA010649 ->
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2004JA010649
If you have any questions/comments about OMNI/OMNIWEB data and service, contact: Dr. Natalia Papitashvili, Space Physics Data Facility, Mail Code 672, NASA/Goddard Space Flight Center, Greenbelt, MD 20771
