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Wind Solar Wind Experiment (SWE) Electron Moments Parameters (6-12s rate) (1994-2001)

ResourceID
spase://NASA/NumericalData/Wind/SWE/H0/PT06S

Description

Wind SWE electron moments included in this data set are derived from the velocity moments integration of solar wind electron distributions measured by the Wind/SWE VEIS instrument (see Ogilvie et al., "SWE, a comprehensive plasma instrument for the WIND spacecraft", Space Sci. Rev., 71, 55, 1955). Moments parameters are computed from 3s measurements which are spaced either 6s or 12s in time. The moments parameters which will be of value to most users of this data set are the electron temperature, the electron temperature anisotropy, and the electron heat flux vector. These quantities are reliable and citable with caution, meaning that the PI advises that the user should discuss their interpretation with a member of the SWE science team before publishing. The following comments are intended to aid in the use and interpretation of the prime quantities of this data set, the electron temperature, the electron temperature anisotropy, and the electron heat flux. (All vector quantities are in GSE coordinates.) The temperature and temperature anisotropy are normalized to the derived electron density and, therefore, are not sensitive to the uncertainty in the density determination as discussed below. The electron temperature is derived from the pressure tensor divided by the electron density and the Boltzmann constant. The three eigenvalues of the diagonalized temperature tensor are the temperature parallel to the tensor principal axis and the two perpendicular components of the temperature. The temperature anisotropy is defined here as the ratio of the parallel temperature to the average of the two perpendicular temperature components. The electron temperature is one-third of the trace of the diagonalized temperaturetensor. Also included is the unit vector along the principal axis of the pressure tensor as well as the cosine of the angle between the principal axis and the magnetic field vector. An indication that the principal axis has been uniquely defined is that the temperature anisotropy is significantly different from unity and that the principal axis and the magnetic field are nearly parallel or anti-parallel.The heat flux vector included here is significant only when the magnitude rises above the noise level, i.e., above the level 0.002 to 0.005 ergs/cm/cm/s. The heat flux may be low in magnitude either due to a nearly isotropic distribution, due to electron counter-streaming, or due to a low counting rate of the instrument. An indicator of a significant net heat flux is that the heat flux direction should track with the magnetic field direction. For this purpose, the cosine of the angle between the heat flux vector and the magnetic field is included, and should be close to -1 or +1 in order for the heat flux to be significant. In some cases it will be necessary to use electron pitch angle distributions (available on request from the SWE team) to decide whether low electron flux or counterstreaming account for a low net heat flux. It is also strongly recommended that 3s magnetic field data from the WIND/MFI experiment (not included in this data set) be used inconjunction with the SWE electron heat flux data to ensure a correct interpretation of the heat flux. The electron density and electron bulk flow velocity are also included in this data set but no claim is made for their accuracy. The electron flow velocity is usually within 10% to 20% of the solar wind flow velocity derived from the SWE Faraday cup experiment and which are found in the SWE key parameter data set. The electron density, however, cannot be absolutely determined due to the spacecraft potential and the fact that the electron instrument response has varied over time. The electron density determination includes a first order attempt to determine the spacecraft potential by imposing the charge neutrality condition on the derived electron density and Faraday cup ion density. The electron density will be within a few percent of the solar wind density derived from the Faraday cup early in the mission (1994-1997), while later in the mission (1998 and onward), depending on the state of the instrument, there will be times when the derived electron density may be as much as a factor 2 too low. Although the electron density is not derived absolutely, relative changes in electron density can be relied on. Both the electron density and electron flow speed track with variations in the ion density and ion flow speed, respectively. However, the user is strongly advised to use the SWE ion key parameters for the bulk plasma density and flow speed.

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Details

Version:2.2.9

NumericalData

ResourceID
spase://NASA/NumericalData/Wind/SWE/H0/PT06S
ResourceHeader
ResourceName
Wind Solar Wind Experiment (SWE) Electron Moments Parameters (6-12s rate) (1994-2001)
AlternateName
WI_H0_SWE_v01
AlternateName
WI_H0_SWE_v02
ReleaseDate
2020-07-07 21:16:05Z
Description

Wind SWE electron moments included in this data set are derived from the velocity moments integration of solar wind electron distributions measured by the Wind/SWE VEIS instrument (see Ogilvie et al., "SWE, a comprehensive plasma instrument for the WIND spacecraft", Space Sci. Rev., 71, 55, 1955). Moments parameters are computed from 3s measurements which are spaced either 6s or 12s in time. The moments parameters which will be of value to most users of this data set are the electron temperature, the electron temperature anisotropy, and the electron heat flux vector. These quantities are reliable and citable with caution, meaning that the PI advises that the user should discuss their interpretation with a member of the SWE science team before publishing. The following comments are intended to aid in the use and interpretation of the prime quantities of this data set, the electron temperature, the electron temperature anisotropy, and the electron heat flux. (All vector quantities are in GSE coordinates.) The temperature and temperature anisotropy are normalized to the derived electron density and, therefore, are not sensitive to the uncertainty in the density determination as discussed below. The electron temperature is derived from the pressure tensor divided by the electron density and the Boltzmann constant. The three eigenvalues of the diagonalized temperature tensor are the temperature parallel to the tensor principal axis and the two perpendicular components of the temperature. The temperature anisotropy is defined here as the ratio of the parallel temperature to the average of the two perpendicular temperature components. The electron temperature is one-third of the trace of the diagonalized temperaturetensor. Also included is the unit vector along the principal axis of the pressure tensor as well as the cosine of the angle between the principal axis and the magnetic field vector. An indication that the principal axis has been uniquely defined is that the temperature anisotropy is significantly different from unity and that the principal axis and the magnetic field are nearly parallel or anti-parallel.The heat flux vector included here is significant only when the magnitude rises above the noise level, i.e., above the level 0.002 to 0.005 ergs/cm/cm/s. The heat flux may be low in magnitude either due to a nearly isotropic distribution, due to electron counter-streaming, or due to a low counting rate of the instrument. An indicator of a significant net heat flux is that the heat flux direction should track with the magnetic field direction. For this purpose, the cosine of the angle between the heat flux vector and the magnetic field is included, and should be close to -1 or +1 in order for the heat flux to be significant. In some cases it will be necessary to use electron pitch angle distributions (available on request from the SWE team) to decide whether low electron flux or counterstreaming account for a low net heat flux. It is also strongly recommended that 3s magnetic field data from the WIND/MFI experiment (not included in this data set) be used inconjunction with the SWE electron heat flux data to ensure a correct interpretation of the heat flux. The electron density and electron bulk flow velocity are also included in this data set but no claim is made for their accuracy. The electron flow velocity is usually within 10% to 20% of the solar wind flow velocity derived from the SWE Faraday cup experiment and which are found in the SWE key parameter data set. The electron density, however, cannot be absolutely determined due to the spacecraft potential and the fact that the electron instrument response has varied over time. The electron density determination includes a first order attempt to determine the spacecraft potential by imposing the charge neutrality condition on the derived electron density and Faraday cup ion density. The electron density will be within a few percent of the solar wind density derived from the Faraday cup early in the mission (1994-1997), while later in the mission (1998 and onward), depending on the state of the instrument, there will be times when the derived electron density may be as much as a factor 2 too low. Although the electron density is not derived absolutely, relative changes in electron density can be relied on. Both the electron density and electron flow speed track with variations in the ion density and ion flow speed, respectively. However, the user is strongly advised to use the SWE ion key parameters for the bulk plasma density and flow speed.

Acknowledgement
Please acknowledge the Wind/SWE electron instrument team and NASA/GSFC.
Contacts
RolePerson
1.PrincipalInvestigatorspase://SMWG/Person/Keith.W.Ogilvie
InformationURL
Name
Wind/SWE Description
URL
https://wind.nasa.gov/swe/index.html
Description

Wind/SWE (Solar Wind Experiment) electron instruments, history and data products

PriorIDs
spase://VHO/NumericalData/Wind/SWE/H0_PT06S
spase://VSPO/NumericalData/Wind/SWE/H0/PT06S
AccessInformation
RepositoryID
spase://SMWG/Repository/NASA/GSFC/SPDF/CDAWeb
Availability
Online
AccessRights
Open
AccessURL
Name
FTPS from SPDF (not with most browsers)
URL
ftps://spdf.gsfc.nasa.gov/pub/data/wind/swe/swe_h0/
Description

Repository of the Wind/SWE H0 electron data.

AccessURL
Name
HTTPS from SPDF
URL
https://spdf.gsfc.nasa.gov/pub/data/wind/swe/swe_h0/
Description

In CDF via HTTP from SPDF

AccessURL
Name
CDAWeb
URL
https://cdaweb.sci.gsfc.nasa.gov/cgi-bin/eval2.cgi?dataset=WI_H0_SWE&index=sp_phys
ProductKey
WI_H0_SWE
Format
CDF
Acknowledgement
Please acknowledge the CDAWeb team and NASA/GSFC's NSSDC.
ProviderResourceName
WI_H0_SWE
ProviderVersion
v01
InstrumentIDs
spase://SMWG/Instrument/Wind/SWE
MeasurementType
ThermalPlasma
TemporalDescription
TimeSpan
StartDate
1994-12-29 00:00:02.409Z
StopDate
2001-05-31 23:59:57.381Z
Cadence
PT06S
Exposure
PT03S
ObservedRegion
Heliosphere.NearEarth
ObservedRegion
Heliosphere.Inner
ObservedRegion
Earth.Magnetosheath
ObservedRegion
Earth.Magnetosphere.Magnetotail
Keywords
Solar Wind Plasma
Parameter #1
Name
Time
ParameterKey
Epoch
Description

Timestamp marks beginning of a measurement interval.

Caveats
Measurements are from observations over one spin periods, totaling approx 3 sec, but read out about 6-12 sec, depending on real-time telemetery throughput.
Units
CDF_Epoch
ValidMin
01-Jan-1990 00:00:00.000
ValidMax
31-Dec-2029 23:59:59.999
FillValue
31-Dec-9999 23:59:59.999
Support
SupportQuantity
Temporal
Parameter #2
Name
Electron Temperature
ParameterKey
Te
Description

Electron temperature, Te. Te = (trace of pressure tensor)/(electron density * Boltzman constant)/3 = (2*Te_perp + Te_para)/3

Units
K
ValidMin
10000.0
ValidMax
1.0E+06
FillValue
-1.0E31
Particle
ParticleType
Electron
Qualifier
Total
ParticleQuantity
Temperature
Parameter #3
Name
Electron Temperature Anisotropy
ParameterKey
Te_anisotropy
Description

Electron temperature anisotropy (Te_Para/Te_Perp). Te_perp = average of the perpendicular elements of the temperature tensor. Te_para = parallel component of the temperature tensor.

Units
unitless
ValidMin
0.5
ValidMax
2.0
FillValue
-1.0E31
Particle
ParticleType
Electron
Qualifier
Anisotropy
ParticleQuantity
Temperature
Parameter #4
Name
Electron Thermal Energy, Average
ParameterKey
average_energy
Description

Average electron thermal energy = (3/2)Boltzmann constant * Te

Units
eV
ValidMin
0.0
ValidMax
75.0
FillValue
-1.0E31
Particle
ParticleType
Electron
Qualifier
Average
ParticleQuantity
Energy
Parameter #5
Name
Principle axis of pressure tensor - unit vector
ParameterKey
pa_press_tensor
Description

Principle axis of pressure tensor - unit vector

CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
GSE
Structure
Size
3
Element
Name
pa_press_tensor_x
Qualifier
Component.I
Index
1
Element
Name
pa_press_tensor_y
Qualifier
Component.J
Index
2
Element
Name
pa_press_tensor_z
Qualifier
Component.K
Index
3
ValidMin
-1.0
ValidMax
1.0
FillValue
-1.0E31
Support
Qualifier
Vector
SupportQuantity
Other
Parameter #6
Name
Pressure tensor PA dot B unit vector
ParameterKey
pa_dot_B
Description

Pressure tensor principle axis dot magnetic field unit vector

ValidMin
-1.0
ValidMax
1.0
FillValue
-1.0E31
Mixed
MixedQuantity
Other
ParticleType
Electron
Parameter #7
Name
Heat flux magnitude
ParameterKey
heat_flux_magn
Description

Electron heat flux magnitude

Units
ergs/(cm^2 s)
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GSE
ValidMin
0.001
ValidMax
0.03
FillValue
-1.0E31
Particle
ParticleType
Electron
Qualifier
Magnitude
ParticleQuantity
HeatFlux
Parameter #8
Name
Heat flux elevation
ParameterKey
heat_flux_el
Description

Electron heat flux elevation

Units
degrees
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GSE
ValidMin
-90.0
ValidMax
90.0
FillValue
-1.0E31
Particle
ParticleType
Electron
Qualifier
DirectionAngle.ElevationAngle
ParticleQuantity
HeatFlux
Parameter #9
Name
Heat flux azimuth
ParameterKey
heat_flux_az
Description

Electron heat flux azimuth

Units
degrees
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GSE
ValidMin
0.0
ValidMax
360.0
FillValue
-1.0E31
Particle
ParticleType
Electron
Qualifier
DirectionAngle.AzimuthAngle
ParticleQuantity
HeatFlux
Parameter #10
Name
Heat flux dot B unit vector
ParameterKey
Q_dot_B
Description

Heat flux dot B unit vector

ValidMin
-1.0
ValidMax
1.0
FillValue
-1.0E31
Mixed
MixedQuantity
Other
ParticleType
Electron
Parameter #11
Name
Spacecraft Position (GSE)
ParameterKey
sc_position
Description

Spacecraft Position (GSE)

Units
Re
CoordinateSystem
CoordinateRepresentation
Cartesian
CoordinateSystemName
GSE
Structure
Size
3
Element
Name
SC_X_GSE
Qualifier
Component.I
Index
1
Element
Name
SC_Y_GSE
Qualifier
Component.J
Index
2
Element
Name
SC_Z_GSE
Qualifier
Component.K
Index
3
ValidMin
-220.0
ValidMax
220.0
FillValue
-1.0E31
Support
Qualifier
Vector
SupportQuantity
Positional
Parameter #12
Name
el_bulk_vel_magnitude
ParameterKey
el_bulk_vel_magn
Description

Electron bulk velocity - magnitude

Caveats
See the global product description.
Units
km/s
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GSE
ValidMin
200.0
ValidMax
1000.0
FillValue
-1.0E31
Particle
ParticleType
Electron
Qualifier
Magnitude
ParticleQuantity
FlowVelocity
Parameter #13
Name
el_bulk_vel_elevation
ParameterKey
el_bulk_vel_el
Description

Electron bulk velocity - elevation

Caveats
See the global product description.
Units
degrees
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GSE
ValidMin
-90.0
ValidMax
90.0
FillValue
-1.0E31
Particle
ParticleType
Electron
Qualifier
DirectionAngle.ElevationAngle
ParticleQuantity
FlowVelocity
Parameter #14
Name
el_bulk_vel_azimuth
ParameterKey
el_bulk_vel_az
Description

Electron bulk velocity - azimuth

Caveats
See the global product description.
Units
degrees
CoordinateSystem
CoordinateRepresentation
Spherical
CoordinateSystemName
GSE
ValidMin
0.0
ValidMax
360.0
FillValue
-1.0E31
Particle
ParticleType
Electron
Qualifier
DirectionAngle.AzimuthAngle
ParticleQuantity
FlowVelocity
Parameter #15
Name
Electron density
ParameterKey
el_density
Description

Electron density

Caveats
See the global product description.
Units
/cc
ValidMin
0.1
ValidMax
100.0
FillValue
-1.0E31
Particle
ParticleType
Electron
ParticleQuantity
NumberDensity
Parameter #16
Name
Spacecraft Potential
ParameterKey
sc_pot
Description

Spacecraft Potential

Caveats
Forst-order estimate only; see the global product description.
Units
Volts
ValidMin
0.0
ValidMax
20.0
FillValue
-1.0E31
Support
SupportQuantity
Other
Parameter #17
Name
Quality Flag yet to be defined
ParameterKey
flag
Description

Quality Flag, yet to be defined

ValidMin
0
ValidMax
9
FillValue
-32768
Support
SupportQuantity
Other
Parameter #18
Name
major_frame_record _number
ParameterKey
major_fr_rec
Description

major frame record number

ValidMin
0
ValidMax
1900
FillValue
-2147483648
Support
SupportQuantity
Other
Parameter #19
Name
major_frame_spin_number
ParameterKey
major_fr_spin_number
Description

Major frame spin number

ValidMin
0
ValidMax
7
FillValue
-2147483648
Support
SupportQuantity
Other