Are There Different Populations of Flux Ropes in the Solar Wind?

Abstract

Flux ropes are twisted magnetic structures, which can be detected by in-situ measurements in the solar wind. However, different properties of detected flux ropes suggest different types of flux-rope population. As such, are there different populations of flux ropes? The answer is positive, and is the result of the analysis of four lists of flux ropes, including magnetic clouds (MCs), observed at 1 AU. The in-situ data for the four lists have been fitted with the same cylindrical force-free model, which provides an estimation of the local flux-rope parameters such as its radius and orientation. Since the flux-rope distributions have a large dynamic range, we go beyond a simple histogram analysis by developing a partition technique that uniformly distributes the statistical fluctuations over the radius range. By doing so, we find that small flux ropes with radius R < 0.1 AU have a steep power-law distribution in contrast to the larger flux ropes (identified as MCs), which have a Gaussian-like distribution. Next, from four CME catalogs, we estimate the expected flux-rope frequency per year at 1 AU. We find that the predicted numbers are similar to the frequencies of MCs observed in-situ. However, we also find that small flux ropes are at least ten times too abundant to correspond to CMEs, even to narrow ones. Investigating the different possible scenarios for the origin of those small flux ropes, we conclude that these twisted structures can be formed by blowout jets in the low corona or in coronal streamers.

Counterstreaming electrons in small interplanetary magnetic flux ropes

“…Therefore, Feng et al [] proposed that SIMFRs originate from the Sun and are interplanetary manifestations of small coronal mass ejections (CMEs). In addition, some authors discussed the origin of SIMFRs by investigating the possible relationship between SIMFRs and MCs and found that SIMFRs and MCs have many common and similar (or relative) characteristics [e.g., Feng et al , , , ; Cartwright and Moldwin, ; Feng and Wu, ; Yu et al , ; Janvier et al , , ; Feng and Wang, ]. These authors tend to agree with the view that SIMFRs originate from solar corona.…”

The Contribution of Coronal Jets to the Solar Wind

“…Coronagraph and in-situ observations revealed that coronal jets can produce signatures in the outer corona, sometimes even at Earth or beyond (St. Cyr et al 1997;Wang et al 1998;Wood et al 1999;Corti et al 2007;Neugebauer 2012;Janvier et al 2014;Yu et al 2014). It was therefore suggested that they contribute to powering the corona and solar wind (e.g., Shibata et al 2007;Cirtain et al 2007).…”

The Distributions of Iron Average Charge States in Small Flux Ropes in Interplanetary Space: Clues to Their Twisted Structures

“…MCs are of great interest due to their associations with strong solar eruptions and potentially immense geoeffectiveness (e.g., H. Hu et al, ; Wang, Zhang, et al, ). SFRs contribute mainly to slow solar wind, and their source regions and formation mechanisms are still under discussion (e.g., Feng et al, , ; Janvier et al, , ; Kilpua et al, ; Tian et al, ; Yu et al, , ; Zheng & Hu, ).…”

“…Different from MCs that originate from the solar corona, SFRs are believed to have two source regions: the solar corona and the interplanetary medium (e.g., Cartwright & Moldwin, ; Feng et al, ; Janvier et al, ; Moldwin et al, ; Rouillard et al, ; Tian et al, ; Yu et al, , ). SFRs originating in the solar corona can be classified into two categories.…”