Ulysses Solar Wind Observations Over the Poles of the Sun (SWOOPS) Alpha Particle Distribution Functions, Level H2, 4 min Data

2021-04-27 15:38:11Z

This File contains the Distribution Function of Alpha Particles. DATA REDUCTION: The SWOOPS (Solar Wind Observations Over the Poles of the Sun) Ion Instrument is a Spherical-Section Curved-Plate Electrostatic Analyzer. Particle Arrival Directions are measured in Spacecraft Coordinates of Azimuth (scanned by Spacecraft Rotation) and Elevation (determined by the Detector Number) Angles. The Spacecraft Spin Axis was oriented toward the Earth. The Energy/Charge (E/q) Resolution was about 2.5% while the Azimuth (Phi) and Elevation (Theta) Resolutions were both ~5.6°. A Description of the SWOOPS is given in a Paper by S.J. Bame, D.J. McComas, B.L. Barraclough, J.L. Phillips, K.J. Sofaly, J.C. Chavez, B.E. Goldstein, and R.K. Sakurai, Astronomy and Astrophysics Supplement Series, Ulysses Instruments Special Issue, Vol. 92, No. 2, p.237-265, 1992. The Number of Counts in each E/q-Phi-Theta Bin were examined to determine the Peak of the Proton and Alpha Particle Distribution, respectively, and the Vector Magnetic Field (in Spacecraft Coordinates) was obtained for the Time at which the Peak was measured. A "coarse" Two-Dimensional Matrix was then formed by rotating the Data into a Coordinate System with Axes parallel and perpendicular to the Field Direction. Note that Gyrotropy is assumed in making that Transformation. The Resolution of the Matrix is "coarse" because the Vector Velocity assigned to each Bin was taken to be at the Center of the Bin. In reality, the Counts in each Bin were probably not smoothly distributed in Velocity Space over the Bin, but were weighted toward the Part of the Bin nearest the Center of the Peak of the Velocity Distribution. The "coarse" Distribution would thus yield Values for the Density and Temperature that were higher than the true Values. A Correction for that effect was accomplished by fitting Contours to the coarse Distribution, breaking each Bin or Pixel into Subpixels, and then using the Contours and the calibrated Angular Responses to distribute the Counts among the Subpixels. New Contours were then computed and the Process was continued until it converged. More Details about this Deconvolution of the Angular Data are given in the Appendix of a Paper by Neugebauer, M., et al., "Ion distributions in large magnetic holes in the fast solar wind" J. Geophys. Res., 106, 5635, 2001. This Procedure generated the Matrix of Velocity Distribution Functions of Protons and Alpha Particles parallel and perpendicular to the simultaneously measured Magnetic Field.

D.J. McComas, B.E. Goldstein, M.M. Neugebauer, A. Tenerani

spase://VSPO/NumericalData/Ulysses/SWOOPS/AlphaParticle/FitParameters/PT4M

Online

Open

CDF

None

D.J. McComas, B.E. Goldstein, M.M. Neugebauer, A. Tenerani. Please acknowledge the Data Providers and CDAWeb when using these Data.

Online

Open

CSV

D.J. McComas, B.E. Goldstein, M.M. Neugebauer, A. Tenerani. Please acknowledge the Data Providers and CDAWeb when using these Data.

PT4M

Epoch Time

Epoch

Epoch Time

This Parameter exhibits an increasing Monotonic Progression.

PT4M

ms

1.0e-3>s

18-Nov-1990 00:00:00.000

01-Jul-2009 00:00:00.000

-1.0e+31

Heliographic Latitude, HG

Time Series defined by using: EPOCH

heliographicLatitude

Heliographic Latitude in Heliographic, HG, Coordinates

PT4M

°

0.0174532925>rad

-90.0

90.0

-1.0e+31

Heliocentric Distance

Time Series defined by using: EPOCH

heliocentricDistance

Heliocentric Distance

PT4M

ua

1.495978706961e11>m

0.0

99999.0

-1.0e+31

Magnetic Field BR Component, RTN

Time Series defined by using: EPOCH

BR

Magnetic Field BR Component in Inertial Radial, Tangential, Normal, RTN, Coordinates

PT4M

nT

1.0e-9>T

-9999.0

9999.0

-1.0e+31

Magnetic Field BT Component, RTN

Time Series defined by using: EPOCH

BT

Magnetic Field BT Component in Inertial Radial, Tangential, Normal, RTN, Coordinates

PT4M

nT

1.0e-9>T

-9999.0

9999.0

-1.0e+31

Magnetic Field BN Component, RTN

Time Series defined by using: EPOCH

BN

Magnetic Field BN Component in Inertial Radial, Tangential, Normal, RTN, Coordinates

PT4M

nT

1.0e-9>T

-9999.0

9999.0

-1.0e+31

Magnetic Field Magnitude

Time Series defined by using: EPOCH

B_MAG

Magnetic Field Magnitude

PT4M

nT

1.0e-9>T

0.0

9999.0

-1.0e+31

He+ Flow Speed

Time Series defined by using: EPOCH

V_MAG

Alpha Particle, He+, Velocity, Magnitude

PT4M

km/s

1.0e3>m/s

0.0

999999.0

-1.0e+31

He+ Distribution Function, Log10

Time Series defined by using: EPOCH

Matrix

Alpha Particle, He+, Distribution Function, Base 10 Logarithm

Log10 of the Distribution Function. The Distribution Function is a 50⨯25 Matrix. If at a given Time, v_par and/or v_per have a smaller Number of Elements than 50 and 25, respectively, then the undefined Array Entries of v_par and/or v_per and of the Distribution Function are set to a FILLVAL equal to -1.0e30.

PT4M

s^3/(km^3 cm^3)

1.0e-3>s^3/m^6

-1.0e+31

He+ Velocity parallel to the Magnetic Field

Time Series defined by using: EPOCH

v_par

Alpha Particle, He+, Parallel Velocity, v_par, Speed parallel to the Magnetic Field

50 Element Array This Parameter exhibits an increasing Monotonic Progression.

PT4M

km/s

1.0e3>m/s

-1000.0

1000.0

-1.0e+31

He+ Velocity perpendicular to the Magnetic Field

Time Series defined by using: EPOCH

v_per

Alpha Particle, He+, Perpendicular Velocity, v_perp, Speed perpendicular to the Magnetic Field

25 Element Array This Parameter exhibits an increasing Monotonic Progression.

PT4M

km/s

1.0e3>m/s

-1000.0

1000.0

-1.0e+31

He+ Parallel Velocity index

Time Series defined by using: EPOCH

v_par_index

Alpha Particle, He+, Parallel Velocity Index

PT4M

1

50

-9

He+ Perpendicular Velocity Index

Time Series defined by using: EPOCH

v_per_index

Alpha Particle, He+, Perpendicular Velocity Index

PT4M

1

25

-9