https://spdf.gsfc.nasa.gov/pub/data/geotail/merged/sw_min_merged_ascii/00readme file
Geotail 1-min unshifted merged data
As part of an effort to create a multi-year, solar_wind-only, 1-min-resolution
Geotail magnetic field and plasma data set shifted to the Earth's bow shock
nose, and then to incorporate such data into the multi-spacecraft OMNI
data sets, we have created an unshifted solar_wind-only, 1-min Geotail
magnetic field and plasma data set which we describe in this readme file.
The effort is funded through a contract between NASA and QSS Group
and is carried out at GSFC/SPDF.
Equivalent shifted 1-min data from Wind, ACE and IMP 8, and the 1-min
and 5-min OMNI data sets, are accessible from
http://omniweb.gsfc.nasa.gov/ow_min.html. The hourly OMNI data set
is accessible from http://omniweb.gsfc.nasa.gov/. The shifted 1-min
Geotail data will be added to the former site when available.
An FTPBrowser interface to the 1-min unshifted Geotail data is at
http://omniweb.gsfc.nasa.gov/ftpbrowser/geotail_min.html
The basic Geotail data processing cycle was as follows.
Input Geotail data were obtained from CDAWeb. CPI/SWA (Charged
Particle Investigation/Solar Wind Analyzer) plasma data are CDAWeb-
labelled GE_H0_CPI and MGF (Fluxgate Magnetometer) data are
CDAWeb-labelled EDB3SEC_MGF. The CPI data are at
48-s or 96-s resolution, and the MGF data are at 3-sec resolution. Current
Principal Investigators are Bill Paterson, Hampton University, for CPI
and Tsugunobu Nagai, Tokyo Institute of Technology, for MGF. Original
PI's were Louis Frank, U. Iowa, and Susumu Kokobun, Tokyo University,
respectively.
Geotail solar wind "seasons" were determined by considering the Geotail orbit.
These seasons are of ~7 months duration, and shift by ~14 days from one year
to the next. Most but not all Geotail solar wind data occur during these intervals.
The small amount outside these intervals is neglected. These seasons are
listed at "solar_wind_seasons.txt" file of this directory.
First-cut identifications of Geotail solar wind intervals within the solar wind
seasons were then determined by scanning the CPI/SWA spectral plots at U. Iowa:
http://erebus.physics.uiowa.edu/cpi-data/survey/sw/. Identifications of the
(non-solar_wind) intervals between the solar wind intervals thus identified are
listed at "non-solar_wind_intervals.txt" file of this directory.
For the solar wind intervals, 15-s MGF averages were created from the input 3-s
data. This was so that IMF input to our version of the Weimer phase-front-normal
determination software would be of the same resolution as that used previously for
ACE, Wind and IMP. 15-s MGF records with absolute-magnitude values of IMF magnitude
or any component > 70 nT were assumed to be bad data and were not carried forward.
CPI data were despiked using the same software previously applied to Wind and
IMP plasma data. This is described at
http://omniweb.gsfc.nasa.gov/html/HROdocum.html#ap3. The approach is good for
single-point spikes but not for multi-point intervals of bad/suspicious data.
Despiked MGF 15-s and CPI 48-s (or 96-s) ASCII solar-wind-interval data sets
were created and made FTPBrowser-accessible at
http://omniweb.gsfc.nasa.gov/ftpbrowser/geotail_mag15s.html and
http:///omniweb.gsfc.nasa.gov/ftpbrowser/geotail_pla_cpi.html respectively.
30-day MGF and CPI plots were then created for the solar wind seasons of
1995-2005. (Post-2005 MGF data were not yet available to CDAWeb from
Japan/DARTS as of this writing.) These plots were examined for magnetosheath
intervals (for which a drop in flow speed was taken as the primary signature)
and for other �multi-point spikes� that were eliminated. In general, we did not
exclude intervals of foreshock variability if we believed Geotail was indeed in
the solar wind. We did examine concurrent 1-min bow-shock-nose-shifted ACE
and Wind field and plasma data through
http://omniweb.gsfc.nasa.gov/form/sc_merge_min1.html to help resolve
uncertainties as to whether Geotail was in the solar wind or not.
In the process of comparing Geotail data with Wind and ACE data, we became
aware that at very low solar wind temperatures, the Geotail plasma parameters
become unreliable. Based on this, we excluded plasma data for an additional
dozen intervals.
All the points and intervals excluded based on these manual data examinations
are given at "additional_exclusions.txt" file of this directory.
While we cannot guarantee that all non-solarwind data have been removed
from our Geotail �solar wind� data sets, we can say our inclination has been
to eliminate rather than retain suspicious data. The CPI and MGF Investigators
were sent our lists for their comments and, months later, had provided no comments.
With the 15-s magnetic field data and the 48-to-96 sec plasma data believed
to be solar wind only, we then took 1-min averages using the approach
previously applied to Wind, ACE and IMP 8 data and described in detail at
http://omniweb.gsfc.nasa.gov/html/HROdocum.html#ap5. It is these 1-min
data that are in the data files of this directory.
Each 1-min data record has the following format. Note that there is one record
for every minute of the year in each annual file, with only fill values in many of
the records.
The contents/format of records are:
Wd Format Fill values Parameters Units, Comments
1 I4 9999 Year 1995,1996,...
2 I4 999 Doy 1-366
3 I3 99 Hour 0-23
4 I3 99 Minute 0-59
5 I3 99 Nm, Number of mag field points
6 F8.2 9999.99 Field Magnitude Average <|B|>, nT
7 F8.2 9999.99 Magnitude of Avg Field Vr |<B>|,nT
sqrt(<Bx>^2+<By>^2+<Bz>^2)
8 F8.2 9999.99 Bx GSE, GSM nT
9 F8.2 9999.99 By GSE nT
10 F8.2 9999.99 Bz GSE nT
11 F8.2 9999.99 By GSM nT
12 F8.2 9999.99 Bz GSM nT
13 F8.2 9999.99 sigma|B| RMS Std Dev in avg magnitude, nT
14 F8.2 9999.99 sigma B SQRT[sigma(Bx)**2 + Sigma(By)**2
+ Sigma(Bz)**2], nT
15 F8.2 9999.99 sigma Bx RMS Std Dev in Bx GSE, nT
16 F8.2 9999.99 sigma By RMS Std Dev in By GSE, nT
17 F8.2 9999.99 sigma Bz RMS Std Dev in Bz GSE, nT
18 I3 99 Np, Number of plasma points
19 F8.1 99999.9 V, Flow Speed km/s
20 F8.1 99999.9 Vx Velocity, GSE km/s
21 F8.1 99999.9 Vy Velocity, GSE km/s
22 F8.1 99999.9 Vz Velocity, GSE km/s
23 F7.1 999.99 Proton Density_fit n/cc
24 F9.0 9999999. Proton Temperature_fit K
25 F8.2 9999.99 X, GSE S/C position component, Re
26 F8.2 9999.99 Y, GSE "
27 F8.2 9999.99 Z, GSE "
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RRelated data and directories:
SPDF Data and Orbits Services <http://spdf.gsfc.nasa.gov/>
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SPDF Contact:
Natalia Papitashvili <Natalia.E.Papitashvili@nasa.gov>
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Please acknowledge NASA's Space Physics Data Facility and
and relevant scientists identified above for data usage.
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Authorizing NASA Official: Robert.M.Candey, Head, SPDF, NASA Goddard Space Flight Center
e-mail: Robert.M.Candey@nasa.gov
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