SWP_SPC>Solar Wind Electrons Alphas and Protons / Solar Probe Cup 

This file includes the densities, vector velocities, and scalar (radial component) temperatures of the solar wind protons measured by the Solar Probe Cup (SPC). These are determined both by a direct computation of the velocity moments of the reduced distribution function and by attempting to fit the primary peak in the ion I(V) curve with a Maxwellian model.

When such fitting is successful, the data set also includes Maxwellian model fits to the alpha-particle (He++) and tertiary (usually proton beam or shoulder) populations.

NASA open data policy applies. Consultation with the instrument team is strongly recommended.

This project acknowledges the Parker Solar Probe SWEAP instrument team and the SWEAP science data center for providing these solar wind plasma measurements.

Spacecraft ephemeris time, expressed as the number of nanoseconds since J2000 (2000-01-01T12:00:00.000000000) with leap seconds included.    Please refer to CDF TT2000 documentation with regards to this convention.  This time corresponds to the first measurement of the spectrum. Owing to frequent changes in the operating mode, this is usually NOT regular cadence.

The indication of the 32 elements of the data quality array is given by the metadata variable 'DQF_flagnames'. All flags are encoded as follows: --------- ---------------    = 0,   good/nominal/condition not present/etc     > 1,  bad/problematic/condition present/etc     = -1,  status not determined ("don't know")    < -1,  status does not matter ("don't care")  -1 ("don't know") is the default value for all flags.  The 0th flag array element is the [standardized] global quality flag, signifying whether the data are suitable for use without caveate. It is repeated in the "general_flag" variable.

Global quality flag, signifying whether the data for this epoch are suitable for use without caveate.

All flags are encoded as follows: --------------------------    = 0,   good/nominal/condition not present/etc     > 1,  bad/problematic/condition present/etc     = -1,  status not determined ("don't know")    < -1,  status does not matter ("don't care")  -1 ("don't know") is the default value for all flags.  The user is advised to consider the quoted measurement uncertainties, particularly when the general quality flag is zero. 

Proton bulk velocity from the 1st moment of the reduced distribution function, in the spacecraft frame (Only Good Quality)

This moment is a model-independant estimate of the proton bulk speed, but it is subject to confusion with alpha particles when present. Error bars represent estimated upper and lower limits.

proton bulk velocity moment upper uncertainty in the spacecraft frame

This moment is a model-independant estimate of the proton most-probable thermal speed, but it is subject to confusion with alpha particles when present. Error bars represent estimated upper and lower limits.

proton bulk velocity moment lower uncertainty in the spacecraft frame

Proton bulk velocity from the 1st moment of the reduced distribution function in [inertial] RTN coordinate system (Only Good Quality)

Proton density estimate from the 0th moment of the reduced distribution function (Only Good Quality)

This moment is a model-independant estimate of the proton density, but it is subject to confusion with alpha particles when present. Error bars represent estimated upper and lower limits.

Proton radial [most probable] thermal speed estimate from the 2nd velocity moment of the reduced distribution function (Only Good Quality)

Primary proton population velocity, from 1-dimensional Maxwellian fitting, in the spacecraft frame (Only Good Quality)

The strongest signal peak, which generally corresponds to the bulk proton population in the solar wind, is fit to a convected Maxwellian model. 

This uncertainty may be invalid when the Maxwellian is a poor model for the data. Refer to the data quality flags.  The flow angles relative to the SPC are obtained by comparing fluxes upon the four sensor quadrants. This uncertainty incorporates uncertainties in the absolute responses of the respective sensors.

Primary proton population velocity, from 1-dimensional Maxwellian fitting, in the [inertial] RTN frame (Only Good Quality)

Primary proton population density, from 1-dimensional Maxwellian fitting. (Only Good Quality)

The strongest signal peak, which generally corresponds to the bulk proton population in the solar wind, is fit to a convected Maxwellian model.

This uncertainty may be invalid when the Maxwellian is a poor model for the data. Refer to the data quality flags.  This variable reflects *precision* uncertainty from fitting, summed in quadrature with the *accuracy* uncertainy associated with the absolute responses of the SPC sensors.

Primary proton population radial [most probable] thermal speed, from 1-dimensional Maxwellian fitting. (Only Good Quality)

The strongest signal peak, which generally corresponds to the bulk proton population in the solar wind, is fit to a convected Maxwellian model.  This measurement most accurately represents the thermal width of the reduced phase-space-distribution function along the SPC-normal direction. This roughly corresponds to the radial component of the temperature tensor.  This is a most probable thermal speed, i.e. the model distribution goes like exp(-v^2/w^2).

Proton bulk velocity, from 1-dimensional Maxwellian fitting, in the spacecraft frame (Only Good Quality)

the bulk proton population in the solar wind is fit to a group of convected Maxwellian models. 

Proton bulk velocity, from 1-dimensional Maxwellian fitting, in the [inertial] RTN frame (Only Good Quality)

[Total] proton density, from 1-dimensional Maxwellian fitting. (Only Good Quality)

the bulk proton population in the solar wind is fit to a group of convected Maxwellian models.

Proton radial [most probable] thermal speed component, from 1-dimensional Maxwellian fitting. (Only Good Quality)

Alpha particle velocity vector, from 1-dimensional Maxwellian fitting, in the spacecraft frame (Only Good Quality)

The alpha particle (He++) peak in the solar wind, when clearly distinguishable, is fit to a convected Maxwellian model. 

Alpha particle velocity vector, from 1-dimensional Maxwellian fitting, in the [inertial] RTN frame (Only Good Quality)

Alpha particle density, from 1-dimensional Maxwellian fitting. (Only Good Quality)

The alpha particle (He++) peak in the solar wind, when clearly distinguishable, is fit to a convected Maxwellian model.

Alpha particle radial [most probable] thermal speed, from 1-dimensional Maxwellian fitting. (Only Good Quality)

The alpha particle (He++) peak in the solar wind, when clearly distinguishable, is fit to a convected Maxwellian model.  This measurement most accurately represents the thermal width of the reduced phase-space-distribution function along the SPC-normal direction. This roughly corresponds to the radial component of the temperature tensor.  This is a most probable thermal speed, i.e. the model distribution goes like exp(-v^2/w^2).

Population 3 velocity vector, from 1-dimensional Maxwellian fitting, in the spacecraft frame (Only Good Quality)

The population 3 peak in the solar wind, when clearly distinguishable, is fit to a convected Maxwellian model.   Population 3 most typically characterizes a proton shoulder or beam (mtoq=1)

Population 3 velocity vector, from 1-dimensional Maxwellian fitting, in the [inertial] RTN frame (Only Good Quality)

Population 3 particle density, from 1-dimensional Maxwellian fitting. (Only Good Quality)

The population 3 particle peak in the solar wind, when clearly distinguishable, is fit to a convected Maxwellian model.  Population 3 most typically characterizes a proton shoulder or beam (mtoq=1)

Population 3 particle radial [most probable] thermal speed, from 1-dimensional Maxwellian fitting. (Only Good Quality)

The population 3 peak in the solar wind, when clearly distinguishable, is fit to a convected Maxwellian model.  Population 3 most typically characterizes a proton shoulder or beam (mtoq=1)  This measurement most accurately represents the thermal width of the reduced phase-space-distribution function along the SPC-normal direction. This roughly corresponds to the radial component of the temperature tensor.  This is a most probable thermal speed, i.e. the model distribution goes like exp(-v^2/w^2). 

Species identifier for third population fit (in addition to primary proton and alpha peaks) (Only Good Quality)

When the n3_fit, w3_fit, and/or v3_fit variables are valid, they indicate that a third ion population has been measured in addition to the primary proton and alpha particle populations. This variable indicates the estimated mass-per-charge for that population, in fundamental units (i.e. protons=1/1=1, alphas=4/2=2, O6=16/6=2.67). Population 3 most typically characterizes a proton shoulder or beam (mtoq=1)

PSP Spacecraft position in the Heliocentric Inertial system, in km

Also called Ecliptic J2000. Z is the solar north rotational axis, and X is the solar ascending node on the J2000 ecliptic.

PSP Spacecraft velocity in the Heliocentric Inertial system, in km/s

Proton bulk velocity from the 1st moment of the reduced distribution function, in the spacecraft frame (All Qualities)

Proton bulk velocity from the 1st moment of the reduced distribution function in [inertial] RTN coordinate system (All Qualities)

Proton density estimate from the 0th moment of the reduced distribution function (All Qualities)

Proton radial [most probable] thermal speed estimate from the 2nd velocity moment of the reduced distribution function (All Qualities)

Primary proton population velocity, from 1-dimensional Maxwellian fitting, in the spacecraft frame (All Qualities)

Primary proton population velocity, from 1-dimensional Maxwellian fitting, in the [inertial] RTN frame (All Qualities)

Primary proton population density, from 1-dimensional Maxwellian fitting. (All Qualities)

Primary proton population radial [most probable] thermal speed, from 1-dimensional Maxwellian fitting. (All Qualities)

Proton bulk velocity, from 1-dimensional Maxwellian fitting, in the spacecraft frame (All Qualities)

Proton bulk velocity, from 1-dimensional Maxwellian fitting, in the [inertial] RTN frame (All Qualities)

[Total] proton density, from 1-dimensional Maxwellian fitting. (All Qualities)

Proton radial [most probable] thermal speed component, from 1-dimensional Maxwellian fitting. (All Qualities)

Alpha particle velocity vector, from 1-dimensional Maxwellian fitting, in the spacecraft frame (All Qualities)

Alpha particle velocity vector, from 1-dimensional Maxwellian fitting, in the [inertial] RTN frame (All Qualities)

Alpha particle density, from 1-dimensional Maxwellian fitting. (All Qualities)

Alpha particle radial [most probable] thermal speed, from 1-dimensional Maxwellian fitting. (All Qualities)

Population 3 velocity vector, from 1-dimensional Maxwellian fitting, in the spacecraft frame (All Qualities)

Population 3 velocity vector, from 1-dimensional Maxwellian fitting, in the [inertial] RTN frame (All Qualities)

Population 3 particle density, from 1-dimensional Maxwellian fitting. (All Qualities)

Population 3 particle radial [most probable] thermal speed, from 1-dimensional Maxwellian fitting. (All Qualities)

Species identifier for third population fit (in addition to primary proton and alpha peaks) (All Qualities)

This coordinate system is aligned with the Solar Probe Cup. In encounter orientations, the X-axis points in the spacecraft RAM direction, the Z-axis points [roughly] towards the sun, and the Y-axis points south relative to the solar ecliptic plane.  This system is roughly, but not strictly aligned with the heliographic RTN system (R = -Z_SC, T = X_SC, N = -Y_SC) in encounters.  Note that this system is co-moving with the spacecraft. Flows from the sun appear aberrated and shifted in the spacecraft frame according to the instantaneous velocity of the spacecraft.

This coordinate system is oriented such that the R basis vector points along the sun-spacecraft line. The T basis vector is the cross product of the solar rotation axis with R, and the N basis vector completes the triad.  This frame is inertial, i.e. it is the so-oriented inertial frame for the spacecraft's instantaneous position. Vector velocities in this frame are measured relative to the fixed stars.

The 0th flag array element is the [standardized] global quality flag, signifying whether the data are suitable for use without caveate. Refer to the SPC science data center documentation for descriptions of other elements and value definitions.

(17) reduced data quality: anomalous periodic noise type A, (>1 Hz)

(18) reduced data quality: anomalous periodic noise type B (< 1Hz)

(19) temperature/survival heater cycling: potential fluctuations

(20) reduced data quality: broadband or other anomalous noise (type C)


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