  Magnetic loops are building blocks of the closed-field corona. While active
region loops are readily seen in images taken at EUV and X-ray wavelengths,
quiet Sun loops are seldom identifiable and therefore difficult to study on an
individual basis. The first analysis of solar minimum (Carrington Rotation
2077) quiet Sun (QS) coronal loops utilizing a novel technique called the
Michigan Loop Diagnostic Technique (MLDT) is presented. This technique combines
Differential Emission Measure Tomography (DEMT) and a potential field source
surface (PFSS) model, and consists of tracing PFSS field lines through the
tomographic grid on which the Local Differential Emission Measure (LDEM) is
determined. As a result, the electron temperature Te and density Ne at each
point along each individual field line can be obtained. Using data from
STEREO/EUVI and SOHO/MDI, the MLDT identifies two types of QS loops in the
corona: so-called "up" loops in which the temperature increases with height,
and so-called "down" loops in which the temperature decreases with height. Up
loops are expected, however, down loops are a surprise, and furthermore, they
are ubiquitous in the low-latitude corona. Up loops dominate the QS at higher
latitudes. The MLDT allows independent determination of the empirical pressure
and density scale heights, and the differences between the two remain to be
explained. The down loops appear to be a newly discovered property of the solar
minimum corona that may shed light on the physics of coronal heating. The
results are shown to be robust to the calibration uncertainties of the EUVI
instrument.
