Analysis of the heliospheric current sheet fine structure: Single or multiple current sheets

Blanco, J. J.; Rodrı́guez-Pacheco, J.; Hidalgo, M. A.; Sequeiros, J.

doi:10.1016/j.jastp.2006.08.007

Cited by 23 publications

(20 citation statements)

References 23 publications

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“…However, similarly as for simulations for helmet streamers, the thickness of the HCS is too small to clearly explain the formation of structures as large as 0.05 AU: the HCS is ≈ 10 4 km at 1 AU, so less than 10 −4 AU (e.g. the review of Smith, 2001, and more recently Blanco et al, 2006). This is ten times lower than the smallest FRs detected.…”

Section: What Origins For the Small Flux Ropes?mentioning

confidence: 85%

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

2014

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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.

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Section: What Origins For the Small Flux Ropes?mentioning

confidence: 85%

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

2014

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“…They believe that the number of magnetic lines originally connected with the Sun is reduced by prolonged reconnection. The HCS is known as a zone of raised turbulence (Crooker et al 2004;Blanco et al 2006). Repeating reconnection produces discontinuities, waves, magnetic islands, and additional local neutral-lines around the main current sheet (Drake et al 2009;Khabarova & Zastenker 2011).…”

Section: Discussionmentioning

confidence: 99%

Puzzles of the Interplanetary Magnetic Field in the Inner Heliosphere

Khabarova

Обридко

2012

ApJ

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Deviations of the interplanetary magnetic field (IMF) from Parker's model are frequently observed in the heliosphere at different distances r from the Sun. Usually, it is supposed that the IMF behavior corresponds to Parker's model overall, but there is some turbulent component that impacts and disrupts the full picture of the IMF spatial and temporal distribution. However, the analysis of multi-spacecraft in-ecliptic IMF measurements from 0.29 AU to 5 AU shows that the IMF radial evolution is rather far from expected. The radial IMF component decreases with the adiabatic power index (|B r | ∝ r −5/3 ), the tangential component |B r | ∝ r −1 , and the IMF strength B ∝ r −1.4 . This means that the IMF is not completely frozen in the solar wind. It is possible that turbulent processes in the inner heliosphere significantly influence the IMF expansion. This is confirmed by the analysis of the B r distribution's radial evolution. B r has a well-known bimodal histogram only at 0.7-2.0 AU. The bimodality effect gradually disappears from 1 AU to 4 AU, and B r becomes quasi-normally distributed at 3-4 AU (which is a sign of rapid vanishing of the stable sector structure with heliocentric distance). We consider a quasi-continuous magnetic reconnection, occurring both at the heliospheric current sheet and at local current sheets inside the IMF sectors, to be a key process responsible for the solar wind turbulization with heliocentric distance as well as for the breakdown of the "frozen-in IMF" law.

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“…Furthermore, some uncertainty remains about the nature of non-planar structures, generally small perturbations of the HCS or discontinuity normals, which may be attributed to the existence of ripples on a single current sheet surface or to non-parallel multiple surfaces Blanco et al, 2006;Neugebauer, 2008). The perturbations could be caused by waves or vortices on the current sheet surfaces, e.g., Alfvénic fluctuations (Belcher and Daviss, 1971;Roberts et al, 1987;Tsurutani et al, 1994), originating in the corona or generated by shear flows across the HCS (see Neugebauer et al, 1986;Suess et al, 1995 and references therein).…”

Section: Introductionmentioning

confidence: 99%

The Apparent Layered Structure of the Heliospheric Current Sheet: Multi-Spacecraft Observations

et al. 2009

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Multiple current sheet crossings are ubiquitous features of the solar wind associated with high-beta plasma sheets, notably during the passage of the heliospheric current sheet (HCS). As the HCS is being convected past near-Earth, we attempt to resolve spatial scales and temporal variations of the apparent layered structure of the HCS, including adjacent large scale field reversals. We use several spacecraft for good spatial and cross-scale STEREO Results at Solar Minimum C. Foullon et al.coverage, spanning 550 R E across and 900 R E along the Sun -Earth line: STEREO, ACE and Cluster. The multi-spacecraft magnetic and plasma observations within the leading edge of the sector boundary are consistent with i) a broad multi-layered structure; ii) occasional non-planar structures and Alfvénic fluctuations; iii) various stages of transient outflowing loops formed by interchange reconnection. By comparison of the observations at each spacecraft, we obtain a synthesis of the evolution between the patterns of loops, and hence of the transient outflow evolution along the sector boundary. In particular, we present circumstantial evidence that a heat flux dropout, traditionally signalling disconnection, can arise from interchange reconnection and scattering. Moreover, the inter-spacecraft comparison eliminates ambiguities between interpretations of electron counterstreaming. Overall, the sector boundary layer remains, locally, a steady structure as it is convected in the solar wind across a radial heliospheric distance of 560 -580 R E . However, non-planar structures on the Cluster spatial scale, as well as the variations in angular changes and transition durations on the broader scale, indicate that we are not following the evolution of single loops but more likely a bunch of loops with variable properties.

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Analysis of the heliospheric current sheet fine structure: Single or multiple current sheets

Cited by 23 publications

References 23 publications

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

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

Puzzles of the Interplanetary Magnetic Field in the Inner Heliosphere

The Apparent Layered Structure of the Heliospheric Current Sheet: Multi-Spacecraft Observations

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