;+
; NAME:
;  vt3d_dfluxdtemp_emit
; PURPOSE: (one line)
;  Return (d flux / d T) associated with thermal emission
; DESCRIPTION:
;  Return (d flux / d T) associated with thermal emission
; CATEGORY:
;  Volatile Transport
; CALLING SEQUENCE:
;  phi_e = vt3d_dfluxdtemp_emit(emis, temp)
; INPUTS:
;  emis : emissivity, unitless
;  temp : temperature, K
; OUTPUTS:
;  phi_e : d flux/d T in erg cm^-2 s^-1 K^-1
;    where flux is the thermal emission
; RESTRICTIONS:
; PROCEDURE:
;  Young, L. A. 2016, Volatile transport on inhomogeneous surfaces: II. Numerical calculations (VT3D)
;   Resubmitted to Icarus.
;   Eq. 3.2-9b
; MODIFICATION HISTORY:
;  Written 2011 Apr 10, by Leslie Young, SwRI
;  2011-05-18 LAY.  change from e*s*T^3 to 4*e*s*T^3
;  2011-12-30 LAY.  change from temp_0 to temp
;  2016 Mar 24 LAY. Modified for inclusion in vt3d library.
;-

function vt3d_dfluxdtemp_emit, emis, temp

    physconstants
    return, 4 * emis * !phys.sigma * temp^3.

end