Analysis of Small-scale Magnetic Flux Ropes Covering the Whole Ulysses Mission. (arXiv:1905.00986v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Chen_Y/0/1/0/all/0/1">Yu Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hu_Q/0/1/0/all/0/1">Qiang Hu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Roux_J/0/1/0/all/0/1">Jakobus le Roux</a>
Small-scale magnetic flux ropes, in the solar wind, have been studied for
decades via the approach of both simulation and observation. Statistical
analysis utilizing various in-situ spacecraft measurements is the main
observational approach. In this study, we extend the automated detection of
small-scale flux ropes based on the Grad-Shafranov reconstruction to the
complete dataset of emph{Ulysses} spacecraft in-situ measurements. We first
discuss the temporal variation of the bulk properties of 22,719 flux ropes
found through our approach, namely, the average magnetic field and plasma
parameters, etc., as functions of the heliographical latitudes and heliocentric
radial distances. We then categorize all identified events into three groups
based on event distributions in different latitudes separated at 30$^{circ}$,
at different radial distances, and under different solar activities,
respectively. By the detailed statistical analysis, we conclude as follows. (1)
The properties of flux ropes, such as the duration, scale size, etc., follow
the power-law distributions, but with different slope indices, especially for
distributions at different radial distances. (2) Also, they are affected by the
solar wind speed which has different distributions under the different solar
activities, which is manifested as the latitudinal effect. (3) The main
difference in flux rope properties between the low and high latitudes is
attributed to possible Alfv’enic structures or waves. (4) Flux ropes with
longer duration and larger scale sizes occur more often at larger radial
distances. (5) With more strict Wal’en slope threshold, more events are
excluded at higher latitudes. The entire database is published online at
url{this http URL}.
Small-scale magnetic flux ropes, in the solar wind, have been studied for
decades via the approach of both simulation and observation. Statistical
analysis utilizing various in-situ spacecraft measurements is the main
observational approach. In this study, we extend the automated detection of
small-scale flux ropes based on the Grad-Shafranov reconstruction to the
complete dataset of emph{Ulysses} spacecraft in-situ measurements. We first
discuss the temporal variation of the bulk properties of 22,719 flux ropes
found through our approach, namely, the average magnetic field and plasma
parameters, etc., as functions of the heliographical latitudes and heliocentric
radial distances. We then categorize all identified events into three groups
based on event distributions in different latitudes separated at 30$^{circ}$,
at different radial distances, and under different solar activities,
respectively. By the detailed statistical analysis, we conclude as follows. (1)
The properties of flux ropes, such as the duration, scale size, etc., follow
the power-law distributions, but with different slope indices, especially for
distributions at different radial distances. (2) Also, they are affected by the
solar wind speed which has different distributions under the different solar
activities, which is manifested as the latitudinal effect. (3) The main
difference in flux rope properties between the low and high latitudes is
attributed to possible Alfv’enic structures or waves. (4) Flux ropes with
longer duration and larger scale sizes occur more often at larger radial
distances. (5) With more strict Wal’en slope threshold, more events are
excluded at higher latitudes. The entire database is published online at
url{this http URL}.
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