  The origin of small-scale interplanetary magnetic flux-ropes (SIMFRs) and the
relationship between SIMFRs and magnetic clouds (MCs) are still controversial.
In this study, two populations of SMIFRs were collected, i.e., SIMFRs
originating from the Sun (SIMFR-SUN) and those originating from the solar wind
(SIMFR-SW). We defined the SIMFR-SUN (SIMFR-SW) as the SMIFRs that include
(exclude) the counter-streaming suprathermal electrons and stay away from
(close to) the heliospheric current sheet. After fitting with force-free
flux-rope model, 52 SIMFR-SUN and 57 SIMFR-SW events observed by Advanced
Composition Explorer (ACE) from 1998 February to 2011 August were qualified.
Using the approach of relating the measurements to their spatial position
within the flux-ropes, a comparative survey of plasma and composition
characteristics inside the two populations of SIMFRs is presented. Results show
that the two populations of SIMFRs have apparent differences. Compared with
SIMFR-SW, SIMFR-SUN are MC-like, featuring lower central proton density, higher
Vrad, higher low-FIP element abundances, higher and more fluctuate average ion
charge-states and the ion chargestate ratios which are related to the heating
in low corona. In addition, for the ion charge-state distributions inside
SIMFR-SUN, the sunward side is higher than earthward, which might be caused by
the flare heating during eruption. Moreover, both SIMFR-SUN and MCs show
anti-correlation between plasma beta and He/P trend. These characteristics
indicate that SIMFR-SUN and MCs are very likely to have the identical
origination. This study supports the two-source origin of SIMFRs, i.e., the
solar corona and the solar wind.
