  The formation of macroscopic reconnected magnetic structures (islands) have
been observed in advanced experiments on weakly collisional, well confined
plasmas while established theories of the drift-tearing modes, which depend
strongly on the electron temperature gradient and can describe the formation of
these structures, had predicted practically inaccessible excitation thresholds
for them in these regimes. The relevant theoretical dilemma is resolved as
mesoscopic modes that depend critically on the ratio of the transverse (to the
magnetic field) to the longitudinal thermal
conductivity${D^e_{\perp}/D^e_{\|}$, can produce large scale magnetic
reconnection. These modes are envisioned to emerge from a background, which can
be coherent, of collisionless microscopic reconnecting modes driven by the
electron temperature gradient, that create a sequence of adjacent strings of
magnetic islands and increase considerably the ratio ${D^e_{\perp}/D^e_{\|}$
over its classical value. The mesoscopic reconnecting mode is treated by a
singular perturbation analysis involving three asymptotic regions and the small
parameters ${(D^e_{\perp}/D^e_{\|})}^{1/4}$ and ${\epsilon}^{1/4}_{*}$, where
${\epsilon}_{*} {\equiv}D_m/D_A$, $D_m$ is the magnetic diffusion coefficient,
$D_A\sim\texttt{v}^{2}_{A}r_{Te}/(D_Bk_{\perp})$,
$r_{Te}\equiv(-d\texttt{ln}T_e/dr)^{-1}$, $k_{\perp}$ is the transverse mode
number, $\texttt{v}^{2}_{A}=B^{2}/(4\pi{nm}_{i})}$ and $D_B=cT_e/(eB)$.
