def add_footpoint_and_equatorial_drifts(inst, equ_mer_scalar=
    'equ_mer_drifts_scalar', equ_zonal_scalar='equ_zon_drifts_scalar',
    north_mer_scalar='north_footpoint_mer_drifts_scalar', north_zon_scalar=
    'north_footpoint_zon_drifts_scalar', south_mer_scalar=
    'south_footpoint_mer_drifts_scalar', south_zon_scalar=
    'south_footpoint_zon_drifts_scalar', mer_drift='iv_mer', zon_drift='iv_zon'
    ):
    """Translates geomagnetic ion velocities to those at footpoints and magnetic equator.
    Note
    ----
        Presumes scalar values for mapping ion velocities are already in the inst, labeled
        by north_footpoint_zon_drifts_scalar, north_footpoint_mer_drifts_scalar,
        equ_mer_drifts_scalar, equ_zon_drifts_scalar.
    
        Also presumes that ion motions in the geomagnetic system are present and labeled
        as 'iv_mer' and 'iv_zon' for meridional and zonal ion motions.
        
        This naming scheme is used by the other pysat oriented routines
        in this package.
    
    Parameters
    ----------
    inst : pysat.Instrument
    equ_mer_scalar : string
        Label used to identify equatorial scalar for meridional ion drift
    equ_zon_scalar : string
        Label used to identify equatorial scalar for zonal ion drift
    north_mer_scalar : string
        Label used to identify northern footpoint scalar for meridional ion drift
    north_zon_scalar : string
        Label used to identify northern footpoint scalar for zonal ion drift
    south_mer_scalar : string
        Label used to identify northern footpoint scalar for meridional ion drift
    south_zon_scalar : string
        Label used to identify southern footpoint scalar for zonal ion drift
    mer_drift : string
        Label used to identify meridional ion drifts within inst
    zon_drift : string
        Label used to identify zonal ion drifts within inst
        
    Returns
    -------
    None
        Modifies pysat.Instrument object in place. Drifts mapped to the magnetic equator
        are labeled 'equ_mer_drift' and 'equ_zon_drift'. Mappings to the northern
        and southern footpoints are labeled 'south_footpoint_mer_drift' and
        'south_footpoint_zon_drift'. Similarly for the northern hemisphere.
    """
    inst['equ_mer_drift'] = {'data': inst[equ_mer_scalar] * inst[mer_drift],
        'units': 'm/s', 'long_name': 'Equatorial meridional ion velocity',
        'notes':
        'Velocity along meridional direction, perpendicular to field and within meridional plane, scaled to magnetic equator. Positive is up at magnetic equator. Velocity obtained using ion velocities relative to co-rotation in the instrument frame along with the corresponding unit vectors expressed in the instrument frame. Field-line mapping and the assumption of equi-potential field lines is used to translate the locally measured ion motion to the magnetic equator. The mapping is used to determine the change in magnetic field line distance, which, under assumption of equipotential field lines, in turn alters the electric field at that location (E=V/d). '
        , 'label': 'Equatorial Meridional Ion Velocity', 'axis':
        'Equatorial Meridional Ion Velocity', 'desc':
        'Equatorial Meridional Ion Velocity', 'scale': 'Linear',
        'value_min': -500.0, 'value_max': 500.0}
    inst['equ_zon_drift'] = {'data': inst[equ_zonal_scalar] * inst[
        zon_drift], 'units': 'm/s', 'long_name':
        'Equatorial zonal ion velocity', 'notes':
        'Velocity along zonal direction, perpendicular to field and the meridional plane, scaled to magnetic equator. Positive is generally eastward. Velocity obtained using ion velocities relative to co-rotation in the instrument frame along with the corresponding unit vectors expressed in the instrument frame. Field-line mapping and the assumption of equi-potential field lines is used to translate the locally measured ion motion to the magnetic equator. The mapping is used to determine the change in magnetic field line distance, which, under assumption of equipotential field lines, in turn alters the electric field at that location (E=V/d). '
        , 'label': 'Equatorial Zonal Ion Velocity', 'axis':
        'Equatorial Zonal Ion Velocity', 'desc':
        'Equatorial Zonal Ion Velocity', 'scale': 'Linear', 'value_min': -
        500.0, 'value_max': 500.0}
    inst['south_footpoint_mer_drift'] = {'data': inst[south_mer_scalar] *
        inst[mer_drift], 'units': 'm/s', 'long_name':
        'Southern meridional ion velocity', 'notes':
        'Velocity along meridional direction, perpendicular to field and within meridional plane, scaled to southern footpoint. Positive is up at magnetic equator. Velocity obtained using ion velocities relative to co-rotation in the instrument frame along with the corresponding unit vectors expressed in the instrument frame. Field-line mapping and the assumption of equi-potential field lines is used to translate the locally measured ion motion to the magnetic footpoint. The mapping is used to determine the change in magnetic field line distance, which, under assumption of equipotential field lines, in turn alters the electric field at that location (E=V/d). '
        , 'label': 'Southern Meridional Ion Velocity', 'axis':
        'Southern Meridional Ion Velocity', 'desc':
        'Southern Meridional Ion Velocity', 'scale': 'Linear', 'value_min':
        -500.0, 'value_max': 500.0}
    inst['south_footpoint_zon_drift'] = {'data': inst[south_zon_scalar] *
        inst[zon_drift], 'units': 'm/s', 'long_name':
        'Southern zonal ion velocity', 'notes':
        'Velocity along zonal direction, perpendicular to field and the meridional plane, scaled to southern footpoint. Positive is generally eastward. Velocity obtained using ion velocities relative to co-rotation in the instrument frame along with the corresponding unit vectors expressed in the instrument frame. Field-line mapping and the assumption of equi-potential field lines is used to translate the locally measured ion motion to the southern footpoint. The mapping is used to determine the change in magnetic field line distance, which, under assumption of equipotential field lines, in turn alters the electric field at that location (E=V/d). '
        , 'label': 'Southern Zonal Ion Velocity', 'axis':
        'Southern Zonal Ion Velocity', 'desc':
        'Southern Zonal Ion Velocity', 'scale': 'Linear', 'value_min': -
        500.0, 'value_max': 500.0}
    inst['north_footpoint_mer_drift'] = {'data': inst[north_mer_scalar] *
        inst[mer_drift], 'units': 'm/s', 'long_name':
        'Northern meridional ion velocity', 'notes':
        'Velocity along meridional direction, perpendicular to field and within meridional plane, scaled to northern footpoint. Positive is up at magnetic equator. Velocity obtained using ion velocities relative to co-rotation in the instrument frame along with the corresponding unit vectors expressed in the instrument frame. Field-line mapping and the assumption of equi-potential field lines is used to translate the locally measured ion motion to the magnetic footpoint. The mapping is used to determine the change in magnetic field line distance, which, under assumption of equipotential field lines, in turn alters the electric field at that location (E=V/d). '
        , 'label': 'Northern Meridional Ion Velocity', 'axis':
        'Northern Meridional Ion Velocity', 'desc':
        'Northern Meridional Ion Velocity', 'scale': 'Linear', 'value_min':
        -500.0, 'value_max': 500.0}
    inst['north_footpoint_zon_drift'] = {'data': inst[north_zon_scalar] *
        inst[zon_drift], 'units': 'm/s', 'long_name':
        'Northern zonal ion velocity', 'notes':
        'Velocity along zonal direction, perpendicular to field and the meridional plane, scaled to northern footpoint. Positive is generally eastward. Velocity obtained using ion velocities relative to co-rotation in the instrument frame along with the corresponding unit vectors expressed in the instrument frame. Field-line mapping and the assumption of equi-potential field lines is used to translate the locally measured ion motion to the northern footpoint. The mapping is used to determine the change in magnetic field line distance, which, under assumption of equipotential field lines, in turn alters the electric field at that location (E=V/d). '
        , 'label': 'Northern Zonal Ion Velocity', 'axis':
        'Northern Zonal Ion Velocity', 'desc':
        'Northern Zonal Ion Velocity', 'scale': 'Linear', 'value_min': -
        500.0, 'value_max': 500.0}
