This work extends recent efforts on the force-free modeling of large flux
rope-type structures (magnetic clouds, MCs) to much smaller spatial scales. We
first select small flux ropes (SFRs) by eye whose duration is unambiguous and
which were observed by the Solar Terrestrial Relations Observatory (STEREO) or
Wind spacecraft during solar maximum years. We inquire into which analytical
technique is physically most appropriate. We consider three models: (i) linear
force-free field ($\bigtriangledown\times$ B = $\alpha (r) $ B) with a
specific, prescribed constant $\alpha$ (Lundquist solution), and (ii) with
$\alpha$ as a free constant parameter (Lundquist-alpha solution), (iii) uniform
twist field (Gold-Hoyle solution). We retain only those cases where the impact
parameter is less than one-half the FR radius, $R$, so the results should be
robust (29 cases). The SFR radii lie in the range [$\sim$ 0.003, 0.059] AU.
Comparing results, we find that the Lundquist-alpha and uniform twist solutions
yielded comparable and small normalized $\chi^2$ values in most cases. We then
use Grad-Shafranov (GS) reconstruction to analyze these events further. We then
considered the twist per unit length, $\tau$, both its profile through the FR
and its absolute value. We find $\tau$ to lie in the range [5.6, 34] turns/AU.
The GH model-derived $\tau$ values are comparable to those obtained from GS
reconstruction. We find that twist unit length ($L$) is inversely proportional
to $R$, as $\tau \sim 0.17/R$. We combine MC and SFR results on $\tau (R)$ and
give a relation which is approximately valid for both sets. The axial and
azimuthal fluxes, $F_z$ and $F_\phi$, vary as $\approx 2.1 B_0 R^2
\times10^{21}$ Mx and $F_{\phi}/L \approx 0.36 B_0 R \times10^{21}$Mx/AU. The
relative helicity per unit length, $H/L \approx 0.75 B_0^2 R^3$$\times 10^{42}$
Mx$^2$/AU.
