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tokens: this, for the remainder of this paper we will treat the plasma density within the loops as approximately uniform in space and constant in time, with a value of n e ≈ 10 11 cm −3 . Figure 6. Histogram of plasma electron number densities (with bin size ) for reliable pixels located within the bullet. 4.5. Cooling Time As noted in Section 4.2 , the loop emission appears first in Fe xxi and subsequently appears ∼11 minutes later in Si iv and O iv . The similar spatial location and appearance of the intensity features discussed above in Figure 3 suggests that the Si iv emission originates from the same evaporated plasma as the Fe xxi emission, which has subsequently cooled into the cooler spectral lines. Further, the nearly constant density in the loops (noted above) suggests that the cooling process is approximately isovolumetric. To estimate the cooling time, we recall from Aschwanden ( 2005 ) that the radiative and conductive cooling times (in seconds) are given, respectively, byandwhere T is the plasma temperature (in K), n e is the electron number density (in cm −3 ), and L is temperature gradient length scale (in cm); we have also defined the proton mass m p , the heat capacity at constant volume c v , the conductive coefficient κ 0 = 1.1 × 10 −6 , and the radiative loss function (Aschwanden 2005 ). For our purposes, we will approximate the temperature gradient length scale as the loop half-length. From inspection of Figure 1 (c) (which best shows the coronal loops), we find that the footpoint separation for the loops that cross the slit is about 217. As this observation was relatively close to disk center at the time of the flare, for the purposes of this study we will adopt a conversion factor of 730 km arcsec −1 to obtain a footpoint separation of ∼15.8 Mm and a loop half-length (assuming a elliptical loop with eccentricity e = 0.8; see Section 5 for our explanation of this choice) of ∼10.1 Mm. From Equations ( 2 ) and ( 3 ) we note that, for a 10.1 Mm loop that begins at ∼11 MK at density ∼10 11 cm −3 , the conductive cooling time is significantly shorter than the radiative cooling time and will dominate the energy losses. As noted above, thermal conduction will quickly eliminate any initial temperature inhomogeneities that were present in the loop, resulting in the loop possessing a uniform temperature structure. Later, by the time the loop plasma has cooled sufficiently for significant Si iv and O iv emission to appear, it is the radiative energy losses that dominate. To estimate a timescale for the overall cooling from the ∼10 MK to ∼80,000 K, we equate these two timescales and solve for T . This yields an approximate crossover temperature, T *, at which the two energy-loss processes are approximately equal, given byFor a loop as described above, this yields a crossover temperature of T * ≈ 5.7 MK, and substituting back into Equations ( 2 ) or ( 3 ) above gives a timescale for the loop cooling from the Fe xxi temperatures to Si iv