Interplanetary coronal mass ejections in the near-Earth solar wind during the minimum periods following solar cycles 22 and 23

Kilpua, Emilia; Lee, Christina O.; Luhmann, J. G.; Li, Y.

doi:10.5194/angeo-29-1455-2011

Cited by 27 publications

(12 citation statements)

References 48 publications

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“…We also demonstrated that there was a significant reduction in the Alfvénicity during these years. This clear drop in the amount of fast wind is related to the changes in the coronal global magnetic field structure [ Kilpua et al , ]. At these years, the coronal streamer belt neutral line was flat and confined close to the ecliptic and thus it was mostly the slow solar wind from the streamer belt region or coronal hole boundaries that reached the ecliptic.…”

Section: Discussionmentioning

confidence: 99%

An automated identification method for Alfvénic streams and their geoeffectiveness

2013

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[1] Previous statistical studies have found a close relationship between high-speed streams and high-latitude geomagnetic activity. The speed by itself would increase the geoeffectivity of the solar wind. But it is also believed that pure Alfvénic fluctuations, often found in the trailing part of the streams, play a role in the solar wind driving of geomagnetic activity by amplifying the north-south component of the magnetic field (B Z ), and thereby the dayside reconnection electric field. By automatically identifying slow and fast solar wind streams and by analyzing them for more than one solar cycle, we aimed to study the relation between speed, Alfvénicity, and B Z in the solar wind. It was found out that streams, whose trailing parts are dominated by pure Alfvénic fluctuations, are the most geoeffective streams on average. However, it is not the pure Alfvénic fluctuations themselves which cause the streams to be more geoeffective. There is only a variation of about 10% in B Z due to the Alfvénicity of the fluctuations. Instead the streams are more geoeffective because the pure Alfvénic fluctuations tend to occur during high-solar wind speed and strong interplanetary magnetic field. There is a substantial variation within the solar cycle of how Alfvénic the solar-wind streams are, and years with many extremely Alfvénic streams tend to have more days with moderately large geoeffectivity. The list of solar wind streams is included as extra material to this paper.

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Section: Discussionmentioning

confidence: 99%

An automated identification method for Alfvénic streams and their geoeffectiveness

2013

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“…The MO starts at 07:00 UT and lasts until 19:11 UT. In the case of 2010 January 1 shown in Figure 5 (Kilpua et al 2011), the EPP analysis provides some clue for defining the ICME extent. At the ICME start on 22:04 UT, the EPP is zero during the first half of the MO obstacle but some electron bidirectionality is observed in the second half.…”

Section: In Situ Flux-rope Observationsmentioning

confidence: 99%

A Circular-Cylindrical Flux-Rope Analytical Model for Magnetic Clouds

Nieves‐Chinchilla

Linton

Hidalgo

et al. 2016

ApJ

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We present an analytical model to describe magnetic flux-rope topologies. When these structures are observed embedded in Interplanetary Coronal Mass Ejections (ICMEs) with a depressed proton temperature, they are called Magnetic Clouds (MCs). Our model extends the circular-cylindrical concept of Hidalgo et al. by introducing a general form for the radial dependence of the current density. This generalization provides information on the force distribution inside the flux rope in addition to the usual parameters of MC geometrical information and orientation. The generalized model provides flexibility for implementation in 3D MHD simulations. Here, we evaluate its performance in the reconstruction of MCs in in situ observations. Four Earth-directed ICME events, observed by the Wind spacecraft, are used to validate the technique. The events are selected from the ICME Wind list with the magnetic obstacle boundaries chosen consistently with the magnetic field and plasma in situ observations and with a new parameter (EPP, the Electron Pitch angle distribution Parameter) which quantifies the bidirectionally of the plasma electrons. The goodness of the fit is evaluated with a single correlation parameter to enable comparative analysis of the events. In general, at first glance, the model fits the selected events very well. However, a detailed analysis of events with signatures of significant compression indicates the need to explore geometries other than the circular-cylindrical. An extension of our current modeling framework to account for such non-circular CMEs will be presented in a forthcoming publication.

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“…The diameter of the MC at 1 AU was about 0.12 AU, calculated by multiplying the duration of the MC with its average speed. The obtained width is slightly smaller than the typical MC dimension at 1 AU at solar minimum between cycles 23 and 24 of about 0.25 AU at the orbit of the Earth (Kilpua et al, 2011). The rear end of the MC was observed by Wind at about 03:45 UT when the temperature increased to 2.6 × 10 5 K, the magnetic field decreased from 11 nT to 6.5 nT and the solar wind speed increased to 500 km s −1 .…”

Section: Event Overviewmentioning

confidence: 54%

Analysis of the substructure within a complex magnetic cloud on 3–4 September 2008

et al. 2013

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In this paper we have analyzed a substructure found within a leading part of a north–south-oriented magnetic cloud (MC) observed on 3–4 September 2008 in the near-Earth solar wind by multiple spacecraft (ACE, Wind, THEMIS B and C). The MC was preceded by a stream interface (SI) and followed by a high-speed stream (HSS). The identified substructure featured a strong depletion of suprathermal halo electrons and showed distinct magnetic field and plasma signatures. It occurred where suprathermal electron flow within a cloud changed from bidirectional to unidirectional, indicating change in the field line connectivity to the Sun. We found that the substructure maintained roughly its integrity from the first Lagrangian point to the vicinity of the Earth's bow shock in the front edge of the MC, but revealed small changes in the structure which could be explained either by temporal evolution or spatial configuration of the spacecraft

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Interplanetary coronal mass ejections in the near-Earth solar wind during the minimum periods following solar cycles 22 and 23

Cited by 27 publications

References 48 publications

An automated identification method for Alfvénic streams and their geoeffectiveness

An automated identification method for Alfvénic streams and their geoeffectiveness

A Circular-Cylindrical Flux-Rope Analytical Model for Magnetic Clouds

Analysis of the substructure within a complex magnetic cloud on 3–4 September 2008

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