def alpha_abrupt(t, intensity=0.5):
    """
    Correspond to the function alpha(t) of the sudden incident.

    Parameters
    ----------
    t : float,
        Time.
    intensity : float,
        Intensity of the step of the function. The default is 1.

    Returns
    -------
    float
        The function \alpha(t).

    """
    if int(t/30) % 2 != 0:
        return 1.5

    return 1.5+2*intensity