The CAA Moments data are electron density, velocity vector,
pressure tensor and heat flux vector. The vectors and tensors are provided in GSE coordinates. Velocity and temperature
are also provided as components perpendicular and parallel to the magnetic field.
The magnetic field data is taken from CSDS FGM PP data, at present. In a possible future
release we would ideally use CAA FGM data, but it is considered unlikely that there will be major differences except in
very weak field regions. Furthermore :
* T_perp and T_para are determined by projecting the pressure tensor along the magnetic field and dividing by the density and by Boltzmanns constant. T_perp is the average of the two perpendicular components.
* v_para = (v.b) b and v_perp = v - (v.b) b. where v is the velocity vector and b is the magnetic field unit vector.
These data are produced on the ground using 3-D data and thus are available at time resolutions which are limited by the
rate at which 3-D data can be transmitted. The data source used to generate the mome
nts is always the best available resolution 3-D data; this means mainly 3DR data but in the case 3DX or 3DXP are available these
are used instead for the MOMENTS production (see Mode_DataOrigin_HEEA/LEEA). Choices on the best way to combine data from the two
sensors can be made in the moments production software; in the first release the moments are made using LEEA data in the
energy overlap region.
In some situations, use of both sensors together may be a better choice, for example in case
s where the distribution changes
during a spin as the method can resolve time aliasing errors. If resources allow, the Moments
product at CAA may be updated to take advantage of this possibility.
The advantage of these ground - calculated moments is that the best available
calibration data is used, a correction can be made for the spacecraft potential
measurements (collected by the EFW experiment), and spacecraft electrons can be
properly removed. The current release has been generated automatically
using default values to control the approach to
potential correction and photoelectron removal, and has not been systematically human
- validated, so some errors may exist.
Specifically, the spacecraft potential, Vsc, is set to be 1 V greater than the
measured probe - spacecraft potential provided by
the electric field experiment (EFW) and the lower energy cutoff for the moments
integration is set to reject the energy bin
containing the EFW potential and the one above that (which in practice
may also contain counts due to spacecraft electrons).
Sometimes cold electrons are present which can appear in the same energy bin as the spacecraft photoelectrons,
therefore both the cold electrons and spacecraft photoelectrons are removed resulting in underestimated electron densities.
Recent work
by the EFW team suggests a more accurate determination of from would be a term that increases linearly
above ~10 V (Cully et al., 2007) but this has not yet been
implemented in our CAA moments generation code.Version:2.4.1
The CAA Moments data are electron density, velocity vector,
pressure tensor and heat flux vector. The vectors and tensors are provided in GSE coordinates. Velocity and temperature
are also provided as components perpendicular and parallel to the magnetic field.
The magnetic field data is taken from CSDS FGM PP data, at present. In a possible future
release we would ideally use CAA FGM data, but it is considered unlikely that there will be major differences except in
very weak field regions. Furthermore :
* T_perp and T_para are determined by projecting the pressure tensor along the magnetic field and dividing by the density and by Boltzmanns constant. T_perp is the average of the two perpendicular components.
* v_para = (v.b) b and v_perp = v - (v.b) b. where v is the velocity vector and b is the magnetic field unit vector.
These data are produced on the ground using 3-D data and thus are available at time resolutions which are limited by the
rate at which 3-D data can be transmitted. The data source used to generate the mome
nts is always the best available resolution 3-D data; this means mainly 3DR data but in the case 3DX or 3DXP are available these
are used instead for the MOMENTS production (see Mode_DataOrigin_HEEA/LEEA). Choices on the best way to combine data from the two
sensors can be made in the moments production software; in the first release the moments are made using LEEA data in the
energy overlap region.
In some situations, use of both sensors together may be a better choice, for example in case
s where the distribution changes
during a spin as the method can resolve time aliasing errors. If resources allow, the Moments
product at CAA may be updated to take advantage of this possibility.
The advantage of these ground - calculated moments is that the best available
calibration data is used, a correction can be made for the spacecraft potential
measurements (collected by the EFW experiment), and spacecraft electrons can be
properly removed. The current release has been generated automatically
using default values to control the approach to
potential correction and photoelectron removal, and has not been systematically human
- validated, so some errors may exist.
Specifically, the spacecraft potential, Vsc, is set to be 1 V greater than the
measured probe - spacecraft potential provided by
the electric field experiment (EFW) and the lower energy cutoff for the moments
integration is set to reject the energy bin
containing the EFW potential and the one above that (which in practice
may also contain counts due to spacecraft electrons).
Sometimes cold electrons are present which can appear in the same energy bin as the spacecraft photoelectrons,
therefore both the cold electrons and spacecraft photoelectrons are removed resulting in underestimated electron densities.
Recent work
by the EFW team suggests a more accurate determination of from would be a term that increases linearly
above ~10 V (Cully et al., 2007) but this has not yet been
implemented in our CAA moments generation code.| Role | Person | StartDate | StopDate | Note | |
|---|---|---|---|---|---|
| 1. | PrincipalInvestigator | spase://SMWG/Person/Andrew.N.Fazakerley |
This site contains PEACE data documentation
This site provides information concerning the Cluster II Rumba Plasma Electron and Current Experiment Instrument.
Web Service to this product using the HAPI interface.
Access to Data via CDPP/AMDA Web application.
Electron number density at spin time resolution
Electron velocity at spin time resolution
Electron velocity at spin time resolution, in GSM
Electron parallel velocity at spin time resolution, in GSE
Electron parallel velocity at spin time resolution, in GSM
Electron perpendicular velocity at spin time resolution, in GSE
Electron perpendicular velocity at spin time resolution, in GSM
Parallel electron heat flux at spin time resolution, in GSE
Electron pressure tensor at spin time resolution, in GSE
Parallel electron temperature at spin time resolution
Perpendicular electron temperature at spin time resolution