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Anisotropy 
Directiondependent property. 

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Array 
A sequence of values corresponding to the elements in a rectilinear, ndimension matrix. Each value can be referenced by a unique index. 

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Average 
The statistical mean; the sum of a set of values divided by the number of values in the set. 

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Characteristic 
A quantity which can be easily identified and measured in a given environment. 

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Circular 
Relative to polarization, righthand circularly polarized light is defined such that the electric field is rotating clockwise as seen by an observer towards whom the wave is moving. Lefthand circularly polarized light is defined such that the electric field is rotating counterclockwise as seen by an observer towards whom the wave is moving. The polarization of magnetohydrodynamic waves is specified with respect to the ambient mean magnetic field : righthand polarized waves have a transverse electric field component which turns in a righthanded sense (that of the gyrating electrons) around the magnetic field. 

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Column 
A twodimensional measure of a quantity. The column is the area over which the quantity is measured. 

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Component 
Projection of a vector along one of the base axes of a coordinate system. 

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Component.I 
Projection of a vector along the first named axis of a coordinate system. Typically the X axis, but could be the R axis for an RTN coordinate system. 

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Component.J 
Projection of a vector along the second named axis of a coordinate system. Typically the Y axis, but could be the T axis for an RTN coordinate system. 

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Component.K 
Projection of a vector along the third named axis of a coordinate system. Typically the Z axis, but could be the N axis for an RTN coordinate system. 

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Core 
The central or main part of an object or calculated distribution. For example, the part of a distribution of particles at low energies that is a thermal (Maxwellian) population. 

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CrossSpectrum 
The Fourier transform of the cross correlation of two physical or empirical observations. 

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Deviation 
The difference between an observed value and the expected value of a quantity. 

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Differential 
A measurement within a narrow range of energy and/or solid angle. 

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Direction 
The spatial relation between an object and another object, the orientation of the object or the course along which the object points or moves. 

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DirectionAngle 
The angle between a position vector or measured vector (or one of its projections onto a plane) and one of the base axes of the coordinate system. 

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DirectionAngle.AzimuthAngle 
The angle between the projection into the ij plane of a position or measured vector and the iaxis of the coordinate system. Mathematically defined as arctan(j/i). This term could be also applied to angles measured in different planes, for example the IMF clock angle defined as arctan( 

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DirectionAngle.ElevationAngle 
The angle between the position or measured vector and the ij plane of the coordinate system. Mathematically defined as arctan(k/SQRT(i^2+j^2)). 

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DirectionAngle.PolarAngle 
The angle between the position or measured vector and the kaxis of the coordinate system. Mathematically defined as arctan([SQRT(i^2+j^2)]/k). This term could be also applied to angles between the vector and other components, for example the IMF cone angle defined as arccos(Bx/Bt). 

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Directional 
A measurement within a narrow range of solid angle. 

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FieldAligned 
The component of a quantity which is oriented in the same direction of a field. 

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Fit 
Values that make an model agree with the data. 

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Group 
An assemblage of values that a certain relation or common characteristic. 

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Halo 
The part of an object or distribution surrounding some central body or distribution. For example, the particles above the core energies that show enhancements above the thermal population. Typically, a power law tail shows a break from the core Maxwellian at a particular energy. 

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Integral 
A flux measurement in a broad range of energy and solid angle. 

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Integral.Area 
Integration over the extent of a planar region, or of the surface of a solid. 

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Integral.Bandwidth 
Integration over the width a frequency band. 

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Integral.SolidAngle 
Integration over the angle in threedimensional space that an object subtends at a point. 

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LineOfSight 
The line of sight is the line that connects the observer with the observed object. This expression is often used with measurements of Doppler velocity and magnetic field in magnetograms, where only the component of the vector field directed along the line of sight is measured. 

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Linear 
Polarization where the Efield vector is confined to a given plane 

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Magnitude 
A measure of the strength of a vector quantity or length of its representational vector. 

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Maximum 
The largest value of a batch or sample or the upper bound of a probability distribution. 

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Median 
The measure of central tendency of a set of n. values computed by ordering the values and taking the value at position (n. + 1) / 2 when n. is odd or the arithmetic mean of the values at positions n. / 2 and (n. / 2) + 1 when n. is even. 

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Minimum 
The smallest value of a batch or sample or the lower bound of a probability distribution. 

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Moment 
Parameters determined by integration over a distribution function convolved with a power of velocity. 

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Parallel 
Having the same direction as a given direction 

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Peak 
The maximum value for the quantity in question, over a period of time which is usually equal to the cadence. 

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Perpendicular 
At right angles to a given direction. 

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Perturbation 
Variations in the state of a system. 

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Phase 
A point or portion in a recurring series of changes. 

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PhaseAngle 
Phase difference between two or more waves, normally expressed in degrees. 

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Projection 
A measure of the length of a position or measured vector as projected into a plane of the coordinate system. 

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Projection.IJ 
A measure of the length of a position or measured vector projected into the ij (typically XY) plane of the coordinate system. 

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Projection.IK 
A measure of the length of a position or measured vector projected into the ik (typically XZ) plane of the coordinate system. 

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Projection.JK 
A measure of the length of a position or measured vector projected into the jk (typically YZ) plane of the coordinate system. 

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Pseudo 
Similar to or having the appearance of something else. Can be used to indicate an estimation or approximation of a particular quantity. 

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Ratio 
The relative magnitudes of two quantities. 

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Scalar 
A quantity that is completely specified by its magnitude and has no direction. 

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Spectral 
Characterized as a range or continuum of frequencies 

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StandardDeviation 
The square root of the average of the squares of deviations about the mean of a set of data. Standard deviation is a statistical measure of spread or variability. 

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StokesParameters 
A set of four parameters (usually called I,Q, U and V) which describe the polarization state of an electromagnetic wave propagating through space. 

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Strahl 
A distribution of particles concentrated in a narrow energy band. The band may be may be aligned with a secondary feature. For example, it may occur in a narrow cone aligned with the mean magnetic field direction. 

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Superhalo 
The part of an object or distribution surrounding some central body or distribution evident in a second break in the distribution function (e.g., a different power law). It consists of a population at a higher energies than for a halo. 

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Symmetric 
Equal distribution about one or more axes. 

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Tensor 
A generalized linear quantity or geometrical entity that can be expressed as a multidimensional array relative to a choice of basis of the particular space on which it is defined. 

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Total 
The summation of quantities over all possible species. 

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Trace 
The sum of the elements on the main diagonal (the diagonal from the upper left to the lower right) of a square matrix. 

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Uncertainty 
A statistically defined discrepancy between a measured quantity and the true value of that quantity that cannot be corrected by calculation or calibration. 

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Variance 
A measure of dispersion of a set of data points around their mean value. The expectation value of the squared deviations from the mean. 

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Vector 
A set of parameter values each along some independent variable (e.g., components of a field in three orthogonal spatial directions; atmospheric temperature values at several altitudes, or at a given latitude and longitude;). 
