Details of selected Madrigal Parameters
Madrigal parameters are a superset of Cedar parameters, defined in the
CEDAR File Format (pdf). The purpose of this
document is to more fully document these parameters than can be expressed in
the 40 character offical Cedar description field. Not all Madrigal parameters
can be found here.
SUNRISE_HOUR
Code 0: (not a cedar parameter) Ionospheric sunrise (hour)
This parameter gives the hour UT that sunrise occurs at that particular
point in space that particular day. If that point in space is either in sunlight or in shadow
the entire UT day, sunrise_hour will be missing. To find out which, display the
Shadow height (SDWHT) parameter. If shadow height is less that the altitude of the
point, its in sunlight; if shadow height is greater than the altitude, its in the earth's shadow.
Note that this calculation takes into account the changing earth-sun distance, and the geodetic shape
of the earth. It does not include atmospheric bending of light or earth's surface features (mountains, etc.).
SUNSET_HOUR
Code 0: (not a cedar parameter) Ionospheric sunset (hour)
This parameter gives the hour UT that sunset occurs at that particular
point in space that particular day. If that point in space is either in sunlight or in shadow
the entire UT day, sunset_hour will be missing. To find out which, display the
Shadow height (SDWHT) parameter. If shadow height is less that the altitude of the
point, its in sunlight; if shadow height is greater than the altitude, its in the earth's shadow.
Note that this calculation takes into account the changing earth-sun distance, and the geodetic shape
of the earth. It does not include atmospheric bending of light or earth's surface features (mountains, etc.).
CONJ_SUNRISE_H
Code 0: (not a cedar parameter) Mag conj point sunrise (hour)
This parameter gives the hour UT that sunrise occurs at the magnetic conjugate point of the particular
point in space that particular day. If the magnetic conjugate point in space is either in sunlight or in shadow
the entire UT day, conj_sunrise_h will be missing. To find out which, display the
Mag conj shadow height (MAGCONJSDWHT) parameter. If the mag conj shadow height is
less that the altitude of the
point, its in sunlight; if mag conj shadow height is greater than the altitude, its in the earth's shadow.
Note that this calculation takes into account the changing earth-sun distance, and the geodetic shape
of the earth. It does not include atmospheric bending of light or earth's surface features (mountains, etc.).
CONJ_SUNSET_H
Code 0: (not a cedar parameter) Mag conj point sunset (hour)
This parameter gives the hour UT that sunset occurs at the magnetic conjugate point of the particular
point in space that particular day. If the magnetic conjugate point in space is either in sunlight or in shadow
the entire UT day, conj_sunset_h will be missing. To find out which, display the
Mag conj shadow height (MAGCONJSDWHT) parameter. If the mag conj shadow height is
less that the altitude of the
point, its in sunlight; if mag conj shadow height is greater than the altitude, its in the earth's shadow.
Note that this calculation takes into account the changing earth-sun distance, and the geodetic shape
of the earth. It does not include atmospheric bending of light or earth's surface features (mountains, etc.).
MLT
Code 54: Magnetic Local Time (hour)
This parameter gives the magnetic local time of a particular point in space and time.
If derived, it uses the Altitude Adjusted Corrected Geomag. Coordinates to
define the magnetic coordinates of the sun and the location of
the point where MLT is desired. Uses code written by Kile Baker. Only works
for times after 1987.
JDAYNO
Julian day number (changes at UT midnight)
The number of days since Jan 1, 4713 BC 0 UT. Note that this is different by 12 hours from the astronomical definition, which starts at 12 UT that same day. See JULIAN_DAY for the parameter that starts at 12 UT.
JULIAN_DAY
Julian day number (changes at 12 UT)
The number of 24 hour periods since Jan 1, 4713 BC 12 UT. Note that this is the standard astronomical usage. See JDAYNO for the parameter that starts at 0 UT.
JULIAN_DATE
Julian date (float)
A floating point representation of the number of days since Jan 1, 4713 BC 12 UT. Note that this is the standard astronomical usage.
GDLAT2
Code 162: Geodetic latitude of second instrument (deg)
This parameter gives the latitude of a second instrument.
It is used whenever a difference is given between a parameter measured at this
instrument minus the value at a second instrument. For example, this parameter can be used
to given the difference between two magnetometer readings.
GLON2
Code 172: Geodetic longitude of second inst (deg)
This parameter gives the longitude of a second instrument.
It is used whenever a difference is given between a parameter measured at this
instrument minus the value at a second instrument. For example, this parameter can be used
to given the difference between two magnetometer readings.
SZEN
Code 180: Solar zenith angle in measurement vol (deg)
This parameter gives the solar zenith angle in degrees. If 0 degrees, the sun is directly
overhead. A solar zenith angle of between 90 and 180 degrees does not mean the sun is not
visible, due to the finite solid angle of the sun and the altitude the point may be above the
earth's surface. Use Shadow height (SDWHT) parameter to determine if a point
is in sunlight. If shadow height is less that the altitude of the
point, its in sunlight; if shadow height is greater than the altitude, its in the earth's shadow.
SZENC
Code 183: Conjugate solar zenith angle (deg)
This parameter gives the solar zenith angle at the magnetic confugate point in degrees. If 0 degrees, the sun is directly
overhead the magnetic conjugate point. A solar zenith angle of between 90 and 180 degrees does not mean the sun is not
visible at the mag conj point, due to the finite solid angle of the sun and the altitude the point may be above the
earth's surface. Use the Mag conj shadow height (MAGCONJSDWHT) parameter to determine if the
magnetic conjugate point is in sunlight. If shadow height is less that the altitude of the
point, its in sunlight; if shadow height is greater than the altitude, its in the earth's shadow.
SDWHT
Code 186: Shadow height (km)
This parameter gives the height above the earth's surface at which any part of the sun can be seen. It depends only
on the time, and on the geodetic latitude and longitude. During the day shadow height will be zero. Since the sun is
larger than the earth, the shadow height is always finite. If shadow height is less that the altitude of a given
point in space, its in sunlight; if shadow height is greater than the altitude, its in the earth's shadow.
Note that this calculation takes into account the changing earth-sun distance, and the geodetic shape
of the earth. It does not include atmospheric bending of light or earth's surface features (mountains, etc.).
IGRF model
Based on IGRF 11 released in January 2010.
BDH
Code 236: Delta H-comp of geomag fld (local-remote)
This parameter gives the difference in the horizontal component of the magnetic
field between this instrument's location, and a second instrument. The parameters
GDLAT2 and GLON2 specify the location of the second instrument. The difference
is the local instrument minus the second instrument.
HAV0LT_L
Code 238: Avg of geomag H comp - 22-02LT (local)
This parameter represents the average geomagnetic horizontal component taken for the
four contiguous hours around that UT day's local midnight (from 22 local time to 02
local time). For an instrument just to the east of 0 degrees longitude, this means
that the average may include measurements from the previous UT day. For an instrument
just to the west of 0 degrees longitude, this means the the average may include
measurements from the following UT day. This value will be constant for the entire
UT day. This parameter uses the local instrument's data.
HAV0LT_R
Code 240: Avg of geomag H comp - 22-02LT (remote)
This parameter is similar to HAV0LT_L, except that is uses data from the remote
magnetometer located at the position set by GDLAT2 and GLON2. It represents the average
geomagnetic horizontal component taken for the
four contiguous hours around that UT day's local midnight (from 22 local time to 02
local time). For an instrument just to the east of 0 degrees longitude, this means
that the average may include measurements from the previous UT day. For an instrument
just to the west of 0 degrees longitude, this means the the average may include
measurements from the following UT day. This value will be constant for the entire
UT day.
MAGCONJSDWHT
Code 0: (not a cedar parameter) Magnetic conjugate shadow height (km)
This parameter gives the height above the earth's surface at the magnetic conjugate point's latitude and longitude at
which any part of the sun can be seen. See Shadow height (SDWHT) parameter for more details.
CGM_LAT
Code 0: (not a cedar parameter) Corrected geomagnetic latitude (deg)
This parameter gives the location of a point in Corrected geomagnetic latitude.
This method uses code developed by Vladimir Papitashvili. For more information on CGM coordinates
and this code, click here.
CGM_LONG
Code 0: (not a cedar parameter) Corrected geomagnetic longitude (deg)
This parameter gives the location of a point in Corrected geomagnetic longitude.
This method uses code developed by Vladimir Papitashvili. For more information on CGM coordinates
and this code, click here.
TSYG_EQ_XGSM
Code 0: (not a cedar parameter) Tsyganenko field GSM XY plane X point (earth radii)
This parameter gives the X value in GSM coordinates of where the field line associated
with a given input point in space and time crosses the GSM XY plane. GSM stands for
Geocentric Solar Magnetospheric System, and its XY plane is the equatorial plane of
the earth's magnetic dipole field. The field lines are traced using the
Tsyganenko
Magnetospheric model, so external effects on the earth's magnetic field such the solar wind are
taken into account. This code uses the 2001 Tsyganenko model, which averages solar wind values
over the past hour, instead of simply using present values.
TSYG_EQ_YGSM
Code 0: (not a cedar parameter) Tsyganenko field GSM XY plane Y point (earth radii)
This parameter gives the Y value in GSM coordinates of where the field line associated
with a given input point in space and time crosses the GSM XY plane. GSM stands for
Geocentric Solar Magnetospheric System, and its XY plane is the equatorial plane of
the earth's magnetic dipole field. The field lines are traced using the
Tsyganenko
Magnetospheric model, so external effects on the earth's magnetic field such the solar wind are
taken into account. This code uses the 2001 Tsyganenko model, which averages solar wind values
over the past hour, instead of simply using present values.
TSYG_EQ_XGSM
Code 0: (not a cedar parameter) Tsyganenko field GSE XY plane X point (earth radii)
This parameter gives the X value in GSE coordinates of where the field line associated
with a given input point in space and time crosses the GSE XY plane. GSE stands for
Geocentric Solar Ecliptic System, and its XY plane is the equatorial plane of
the earth's rotation. The field lines are traced using the
Tsyganenko
Magnetospheric model, so external effects on the earth's magnetic field such the solar wind are
taken into account. This code uses the 2001 Tsyganenko model, which averages solar wind values
over the past hour, instead of simply using present values.
TSYG_EQ_YGSM
Code 0: (not a cedar parameter) Tsyganenko field GSE XY plane Y point (earth radii)
This parameter gives the Y value in GSE coordinates of where the field line associated
with a given input point in space and time crosses the GSE XY plane. GSE stands for
Geocentric Solar Ecliptic System, and its XY plane is the equatorial plane of
the earth's rotation. The field lines are traced using the
Tsyganenko
Magnetospheric model, so external effects on the earth's magnetic field such the solar wind are
taken into account. This code uses the 2001 Tsyganenko model, which averages solar wind values
over the past hour, instead of simply using present values.
Parameters describing the interception point of the magnetic field line associated with a given point in space
with the E region. Input point must be above 150 km, or missing returned.
- E_REG_S_LAT - The latitude of the southern point where the magnetic field line defined by the input
point hits the E region (100 km)
- E_REG_S_LON - The longitude of the southern point where the magnetic field line defined by the input
point hits the E region (100 km)
- E_REG_S_SDWHT - The shadow height of the southern point where the magnetic field line defined by the input
point hits the E region (100 km). Shadow height is the altitude of the lowest point on the line of constant geodetic
lat and lon in sunlight.
- E_REG_N_LAT - The latitude of the northern point where the magnetic field line defined by the input
point hits the E region (100 km)
- E_REG_N_LON - The longitude of the northern point where the magnetic field line defined by the input
point hits the E region (100 km)
- E_REG_N_SDWHT - The shadow height of the northern point where the magnetic field line defined by the input
point hits the E region (100 km). Shadow height is the altitude of the lowest point on the line of constant geodetic
lat and lon in sunlight.
Code 0: (not a cedar parameter) These parameters are considered missing if the input point in below the E region.
ASPECT
Code 0: (not a cedar parameter) Magnetic aspect angle
The angle between the magnetic field line and the radar beam at a given point in the beam. A radar beam
looking up the magnetic field line would have ASPECT == 0 (or 180), and a beam perpendicular to the magnetic field line
would have an aspect angle of 90 degrees.
DST
Code 330: Dst Index (nT)
The Madrigal DST data is taken from two sources. If available, verified DST data is taken from
ftp://ftp.ngdc.noaa.gov/STP/GEOMAGNETIC_DATA/INDICES/DST. If not available there,
realtime DST data is taken from the World Data Center for Geomagnetism, Kyoto at
http://swdcwww.kugi.kyoto-u.ac.jp/dst_realtime.
FBAR
Code 352: F10.7 Multiday average observed (Ottawa/Penticton)
The 81 day average value of F10.7, centered at the day of interest.
For days less than 41 days in the past, the average is always over
the last 81 days from the present.
This data comes from ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_RADIO/FLUX/. The
following is from their website:
The sun emits radio energy with a slowly varying intensity. This radio flux,
which originates from atmospheric layers high in the sun's chromosphere and low
in its corona, changes gradually from day-to-day, in response to the number of
spot groups on the disk. Radio intensity levels consist of emission from three
sources: from the undisturbed solar surface, from developing active regions,
and from short-lived enhancements above the daily level. Solar flux density at
2800 megaHertz has been recorded routinely by radio telescope near Ottawa since
February 14, 1947. Each day, levels are determined at local noon (1700 GMT)
and then corrected to within a few percent for factors such as antenna gain,
atmospheric absorption, bursts in progress, and background sky temperature.
Beginning in June 1991, the solar flux density measurement source is Penticton,
B.C., Canada.
HPOW and HPOW_I
Code 365: Hemispheric Power Input and Code 366: Hemispheric Power Index
The Hemispheric Power calculation is based on the original method that was developed from the NASA TIROS satellites that had energy channels that went up to approximately the same energy as the second highest channel in the DMSP SSJ instruments. The algorithm integrates the total power through an auroral pass omitting the top channel for consistency with the earlier satellites, evaluates statistical error estimate, and normalizes the total based on the estimate of the geometry of the pass (e.g., cutting directly through both sides of the auroral oval vs just skimming it along the edge).
The Hemispheric Power Index (HPOW_I) is an integer related to the Hemispheric Power Input (HPOW) in Watts by:
HPOW_I = round(2.09 ln (HPOW/1.0E9))
References:
Hardy, D. A., M. S. Gussenhoven, and E. Holeman (1985), A statistical model of auroral electron precipitation, J. Geophys. Res., 90(A5), 4229–4248, doi:10.1029/JA090iA05p04229.
Fuller-Rowell, T. J., and D. S. Evans (1987), Height-integrated Pedersen and Hall conductivity patterns inferred from the TIROS-NOAA satellite data, J. Geophys. Res., 92(A7), 7606–7618, doi:10.1029/JA092iA07p07606.
Maeda, S., T. J. Fuller-Rowell, and D. S. Evans (1989), "Zonally averaged dynamical and compositional response of the thermosphere to auroral activity during September 18–24, 1984"", J. Geophys. Res., 94(A12), 16869–16883, doi:10.1029/JA094iA12p16869.
FPI_DATAQUAL
Code 461: FPI data quality code
FPI data are ONLY included in the Madrigal files if:
- absolute value of (FWHMi - FWHMm) < FWHMm*0.2, where FWHMi is the Gaussian fit FWHM of the ith record number (data point), and FWHMm is the median FWHM for all points sampled during a given night of data, AND
- absolute value of (LCi - LCm) < LCm*0.2, where LCi is the Gaussian fit line center of the ith record number (data point), and LCm is the median line center for all points sampled during a given night, AND
- BKi < BKm*10.0 where BKi is the constant term of the Gaussian fit to the spectral background (we fit for constant, linear, & quadratic terms) of the ith record number (data point), and BKm is the median constant background term for all points sampled during a given night of data, AND
- (TRESi - TRESm) < TRESm*3.0, where TRESi is the absolute value of the total residual (spectral data points - Gaussian fit) of the ith record number (data point), and TRESm is the median of the total residual values sampled during a given night of data, AND
- AMPi/BKi > 0.2, where AMPi is the Gaussian amplitude maximum of the ith record number (data point) and BKi is the constant background term of the same, ith record number. (We require that the background not be more than 5X brighter than the signal.)
Therefore data are already filtered for bad points. A "FPI Data Quality" assessements is then assigned beyond that. The data user can choose to include or exclude qualities of 1 or 2 as they see fit. It is not immediately evident that surviving data records with quality assignments of "1" or "2" might be auroral (for example), or slight contamination, or just bright twilight.
The quality designation moves from 0 --> 1 if:
- TRESi > 25. Rayleighs, or
- BKi > 50. Rayleighs, or
- AMPi/BKi < 0.75 or
- moon phase > 75%
The quality designation moves from 1 --> 2 if:
- TRESi > 75 Rayleighs, or
- BKi > 200. Rayleighs, or
- AMPi/BKi < 0.5 or
- moon phase > 90%
CHISQ
Code 420: Reduced-chi square of fit
If all statistical assumptions are correct, the expectation value of
chi-square is one. In fact, it tends to be much smaller when the
signal-to-noise ratio is large. This is probably due to the large
correlations between the lag products in this case, which are not
taken into account in the fit.
GFIT
Code 430: Goodness of fit
This is 1000 times the root mean square deviation of the fit from
the the measured autocorrelation function (ACF). Since the ACF is
normalized to 1.0, values of ~1000 indicate ~100% deviations, values
of ~100 indicate ~10% deviations and values ~10 indicate ~1%
deviations.
MHDQC1
Code 461: Millstone Hill data quality code 1
The data quality parameter is generated by an algorithm which
attempts to detect the presence of either a satellite echo or
radio frequency interference (RFI), resulting in a 0 for clean
spectra and a 1 for contaminated spectra. The algorithm's
thresholds are deliberately set to avoid false detections on
genuine incoherent scatter signals, and therefore data
contaminated by weaker satellite or RFI signals will not always
be flagged. In particular, the algorithm will miss
satellites/RFI at altitudes with significant heavy ion (mass >
O+) fractions, or for altitudes with temperatures < 300 K. This
parameter should not be used as the sole data quality flag.
DPOPL
Code -505: Uncertainty in Log10(uncorrected electron density)
This is computed from the statistical uncertainty of the fit ACF at
zero lag. In conformity with the CEDAR standard, it is the logarithm
of the uncertainty, not the uncertainty of the logarithm. If the fit
fails, the density itself is still stored in the data record, and
the uncertainty is missing. This statistical uncertainty is
normally much smaller than the larger uncertainty in the density
calibration, which is ~20%.
INCOHERENT SCATTER RADAR IONOSPHERIC MODEL (ISRIM)
ISRIMs have been developed from long-term datasets of seven incoherent
scatter radars spanning invariant latitudes from 25 to 75 degrees in
American, European and Asian longitudes at Svalbard, Tromso, Sondrestrom,
Millstone Hill, St. Santin, Arecibo and Shigaraki. These models represent
electron density, ion and electron temperatures, and ion drifts in the E and F
regions, giving a comprehensive quantitative description of ionospheric properties.
The modelled values of HMAX and NMAX are always based on local models.
The parameters *_MODEL give model results; the parameters *_MODELDIFF give (measured - model) results.
- Ne - electron density in m^-3
- Nel - log10(electron density in m^-3)
- Te - electron temperature in K
- Ti - ion temperature in K
- Vo - line of sight ion velocity in m/s (pos=away)
- Hmax - Height of peak denity in km
- Nmax - Electron density at peak in m^-3
Visit http://madrigal.haystack.mit.edu/models/ or contact
Shunrong Zhang at MIT Haystack for more information and latest development. Detailed descriptions about
the ISRIMs are given in the following papers:
- Zhang, S.-R., J. M. Holt, A. P. van Eyken, M. McCready, C. Amory-Mazaudier, S. Fukao,
and M. Sulzer (2005), Ionospheric local model and climatology from long-term databases
of multiple incoherent scatter radars, Geophys. Res. Lett., 32,
L20102, doi:10.1029/2005GL023603
- Holt, J. M., S.-R. Zhang, and M. J. Buonsanto (2002), Regional and local ionospheric
models based on Millstone Hill incoherent scatter radar data, Geophys. Res. Lett.,
29(8), 10.1029/2002GL014678.
IRI
The following parameters are derived using the
International Reference Ionosphere (IRI)
model - 2007 version:
- NE_IRI - IRI Electron density (Ne) m-3
- NEL_IRI - IRI Log Electron density (Ne) lg(m-3)
- TN_IRI - IRI Neutral temperature K
- TI_IRI - IRI Ion temperature K
- TE_IRI - IRI Electron temperature K
- PO+_IRI - IRI Composition - [O+]/Ne
- PNO+_IRI - IRI Composition - [NO+]/Ne
- PO2+_IRI - IRI Composition - [O2+]/Ne
- PHE+_IRI - IRI Composition - [HE+]/Ne
- PH+_IRI - IRI Composition - [H+]/Ne
- PN+_IRI - IRI Composition - [N+]/Ne
The IRI code was last imported into Madrigal in August 2007. The routine irisub is called using all the suggested defaults,
as listed in the source code comments. The code is modified only to use geophysical parameters from Madrigal rather than from the
files included in the source code distribution. This is to allow more frequent and automatic updating of those geophysical
parameters.
VNHLU
Code 807: Line of sight horizontal velocity of the neutral atmosphere (positive = away from instrument)
in meters/second. If all the velocity is horizontal, then this is equal to the line of sight velocity
divided by the cosine of the elevation calculated at the pierce point.
MSIS 2000
The following neutral atmosphere parameters are derived using the
MSIS 2000 model.
The MSIS 2000 model is run with the anomalous oxygen option included. Inputs to the model include an array
of Ap data covering times from the time requested to 57 hours prior to the requested time. Madrigal uses its
internal database of Ap values to populate all these times. Other inputs include F10.7 data from 24 hours earlier
and from an 81 day average centered on the time requested. This means the model will not calculate MSIS values for
days less than 40 days in the past.
- TNM - Code 811: Model Neutral temperature K
- TINFM - Code 821: Model Exospheric temperature K
- MOL - Code 830: Log10 (nutrl atm mass density in kg/m3) lg(m-3)
- NTOTL - Code 840: Log10 (nutrl atm number density in m-3) lg(m-3)
- NN2L - Code 850: Nutrl atm compositn-log10([N2] in m-3) lg(m-3)
- NO2L - Code 860: Nutrl atm compositn-log10([O2] in m-3) lg(m-3)
- NOL - Code 870: Nutrl atm composition-log10([O] in m-3) lg(m-3)
- NARL - Code 880: Nutrl atm compositn-log10([AR] in m-3) lg(m-3)
- NHEL - Code 890: Nutrl atm compositn-log10([HE] in M-3) lg(m-3)
- NHL - Code 900: Nutrl atm composition-log10([H] in m-3) lg(m-3)
- NN4SL - Code 902: Nutrl atm compstn-log10([N(4S)] in m-3) lg(m-3)
Notes on conductivity parameters
When derived by the Madrigal derivation engine, Pedersen and Hall conductivities are calculated following
R. W. Schunk and A F. Nagy, in Ionospheres: Physics, Plasma Physics, and Chemistry. See
http://atlas.haystack.mit.edu/cgi-bin/millstone_viewvc.cgi/openmadrigal/trunk/madroot/source/madf/geolib/conduct.f for source code.
Electron density, and ion and electron temperatures are taken from ISR data. The molecular percentage and
the percent hydrogen are taken from the IRI model, and neutral parameters are taken from MSIS.
Notes on interplanetary magnetic field parameters
The interplanetary magnetic field data is taken from ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/omni/. The following
are the notes supplied with this data:
These are the "OMNI" data, hourly interplanetary magnetic field
and solar wind as data prepared by NSSDC, NASA GSFC. Users
are encouraged to acknowledge NSSDC. The IMF/Solar wind qualifier
(parameter SWQ) identifies the observing satellite; the
thousands and hundreds digits are the IMF ID and the tens and ones
digits are the solar wind ID:
| -- Satellite Name -- | -- ID -- |
|---|
| No spacecraft | 0 |
| HEOS 1 and HEOS 2 | 1 |
| VELA 3 | 3 |
| OGO 5 | 5 |
| PROGNOZ 10 | 10 |
| ISEE 1 | 11 |
| ISEE 2 | 12 |
| ISEE 3 | 13 |
| IMP 1 (Expl 18) | 18 |
| IMP 3 (Expl 28) | 28 |
| AIMP 1 (Expl 33) | 33 |
| IMP 4 (Expl 34) | 34 |
| AIMP 2 (Expl 35) | 35 |
| IMP 5 (Expl 41) | 41 |
| IMP 6 (Expl 43) | 43 |
| IMP 7 (Expl 47) | 47 |
| IMP 8 (Expl 50) | 50 |
| WIND | 51
|
Use of these data in publications should be accompanied by
acknowledgements of the National Space Science Data Center.
NSSDC Contact:
Dr. J. H. King, king@nssdca.gsfc.nasa.gov
Dr. N. Papitashvili, natasha@nssdca.gsfc.nasa.gov
Code 633,GSFC/NASA, Greenbelt, MD, 20771
Explanation of coordinate systems
The interplanetary magnetic field data are available in two coordinate systems,
the Geocentric Solar Magnetospheric System (GSM) which has parameters BXGSM,
BYGSM, and BZGSM, and the Geocentric Solar Ecliptic System (GSE) which has parameters BXGSE,
BYGSE, and BZGSE. The following explanation of these two system was taken from a more
complete
tutorial:
Geocentric Solar Magnetospheric System
The Geocentric Solar Magnetospheric System (GSM), as with both the GSE and GSEQ systems,
has its X-axis from the Earth to the
Sun. The Y-axis is defined to be perpendicular to the Earth's magnetic dipole so that the
X-Z plane contains the dipole axis. The positive
Z-axis is chosen to be in the same sense as the northern magnetic pole. The difference
between the GSM system and the GSE and
GSEQ is simply a rotation about the X-axis.
Geocentric Solar Ecliptic System
The Geocentric Solar Ecliptic System (GSE) has its X-axis pointing from the Earth towards the
sun and its Y-axis is chosen to be in the
ecliptic plane pointing towards dusk (thus opposing planetary motion). Its Z-axis is parallel
to the ecliptic pole. Relative to an inertial
system this system has a yearly rotation.
CXR CYR CZR
Code 3331: Bperp. Direction Cosine (South [Apex])
Code 3332: Bperp. Direction Cosine (East [Apex])
Code 3333: Direction Cosine (Up field line [Apex])
The simple definition of these parameters is as follows:
- CXR = x-direction cosine of the radar line-of-sight with respect to apex coords.
- CYR = y-direction cosine of the radar line-of-sight with respect to apex coords.
- CZR = z-direction cosine of the radar line-of-sight with respect to apex coords.
Where
- x = -apex latitude (apex south)
- y = apex longitude (apex east)
- z = distance upward along field line
The precise definition is as follows:
cxr, cyr, czr are the contravariant components of the unit-length radar
line-of-sight vector with respect to a non-orthogonal coordinate system
("apex coordinates") defined for all points by -1 times the apex
latitude of the point (apex south), the geographic longitude of the
apex of the field line on which the point lies (apex east) and the
distance along the field line of the point (apex up-B).
NSAMPLES_SNR_SUMRUL
Code 3347: Num Samples SNR sum rule
Number of range samples used for summation
rule in constructing SNR profile.
NSTEP_SNR_SUMRULEO
Code 3348: Num steps SNR sum rule
Step in samples between consecutive
applications of the SNR summation rule.
VDOPP
Code 3350: Line of sight Doppler Vlos (pos = away)
This is a separate non-linear least squares calculation of the
Doppler velocity, which, unlike parameter 580, does not assume an
incoherent scatter spectrum. This may be particularly useful in
coherent echo studies.
Revised: October 25, 2005