  Shibata & Yokoyama (1999, 2002) proposed a method of estimating the coronal
magnetic field strengths ($B$) and magnetic loop lengths ($L$) of solar and
stellar flares, on the basis of magnetohydrodynamic simulations of the magnetic
reconnection model. Using the scaling law provided by Shibata & Yokoyama (1999,
2002), $B$ and $L$ are obtained as functions of the emission measure
($EM=n^2L^3$) and temperature ($T$) at the flare peak. Here, $n$ is the coronal
electron density of the flares. This scaling law enables the estimation of $B$
and $L$ for unresolved stellar flares from the observable physical quantities
$EM$ and $T$, which is helpful for studying stellar surface activities. To
apply this scaling law to stellar flares, we discuss its validity for spatially
resolved solar flares. $EM$ and $T$ were calculated from GOES soft X-ray flux
data, and $B$ and $L$ are theoretically estimated using the scaling law. For
the same flare events, $B$ and $L$ were also observationally estimated with
images taken by Solar Dynamics Observatory (SDO)/ Helioseismic and Magnetic
Imager (HMI) Magnetogram and Atmospheric Imaging Assembly (AIA) 94{\AA} pass
band. As expected, a positive correlation was found between the theoretically
and observationally estimated values. We interpret this result as indirect
evidence that flares are caused by magnetic reconnection. Moreover, this
analysis makes us confident in the validity of applying this scaling law to
stellar flares as well as solar flares.
