def list_remote_files(tag, sat_id, user=None, password=None):
    """Return a Pandas Series of every file for chosen remote data.

    This routine is intended to be used by pysat instrument modules supporting
    a particular NASA CDAWeb dataset.

    Parameters
    -----------
    tag : (string or NoneType)
        Denotes type of file to load.  Accepted types are <tag strings>.
        (default=None)
    sat_id : (string or NoneType)
        Specifies the satellite ID for a constellation.  Not used.
        (default=None)
    user : (string or NoneType)
        Username to be passed along to resource with relevant data.
        (default=None)
    password : (string or NoneType)
        User password to be passed along to resource with relevant data.
        (default=None)

    Returns
    --------
    pandas.Series
        A Series formatted for the Files class (pysat._files.Files)
        containing filenames and indexed by date and time

    """
    pass
