Modeling and Measuring the Flux Reconnected and Ejected by the Two-Ribbon Flare/CME Event on 7 November 2004

Longcope, D. W.; Beveridge, C.; Qiu, Jiong; Ravindra, B.; Barnes, G.; Dasso, S.

doi:10.1007/s11207-007-0330-7

Cited by 113 publications

(115 citation statements)

References 63 publications

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“…Various measurements indicate that the total magnetic flux of a single active region is about 10 22 Mx (Longcope et al 2007;Jeong and Chae 2007;Magara 2008). Thus, the measured total polar flux barely corresponds to that of single active region.…”

Section: Total Magnetic Fluxmentioning

confidence: 99%

Small-Scale Solar Magnetic Fields

et al. 2008

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As we resolve ever smaller structures in the solar atmosphere, it has become clear that magnetism is an important component of those small structures. Small-scale magnetism holds the key to many poorly understood facets of solar magnetism on all scales, such as the existence of a local dynamo, chromospheric heating, and flux emergence, to name a few. Here, we review our knowledge of small-scale photospheric fields, with particular emphasis on quiet-sun field, and discuss the implications of several results obtained recently using new instruments, as well as future prospects in this field of research.

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Section: Total Magnetic Fluxmentioning

confidence: 99%

Small-Scale Solar Magnetic Fields

et al. 2008

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“…Quantitative studies of F and H both in MCs and in the solar corona are used to relate MCs to their solar sources (using F and H approximative conserved properties). Moreover, these studies set constrains to coronal magnetic configurations and on flux rope formation/eruption models Luoni et al 2005;Attrill et al 2006;Longcope et al 2007;Qiu et al 2007;Harra et al 2007;Mandrini et al 2007;Rodriguez et al 2008;Möstl et al 2008;Ravindra et al 2011). Lepping et al (2011) studied some properties of MCs observed at one astronomical unit by the spacecraft Wind in the two last solar minima.…”

Section: Magnetic Flux and Helicitymentioning

confidence: 99%

Magnetic clouds along the solar cycle: expansion and magnetic helicity

Dasso

Démoulin²,

Gulisano³

2011

Proc. IAU

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Abstract. Magnetic clouds (MCs) are objects of extreme importance in the heliosphere. They have a major role on releasing magnetic helicity from the Sun (with crucial consequences on the solar dynamo), they are the hugest transient object in the interplanetary medium, and the main actors for the Sun-Earth coupling. The comparison between models and observations is beginning to clarify several open questions on MCs, such as their internal magnetic configuration and their interaction with the ambient solar wind. Due to the decay of the solar wind pressure with the distance to the Sun, MCs are typically in expansion. However, their detailed and local expansion properties depend on their environment plasma properties. On the other hand, while it is well known that the solar cycle determines several properties of the heliosphere, the effects of the cycle on MC properties are not so well understood. In this work we review two major properties of MCs: (i) their expansion, and (ii) the magnetic flux and helicity that they transport through the interplanetary medium. We find that the amount of magnetic flux and helicity released via MCs during the last solar minimum (years 2007-2009) was significantly lower than in the previous one (years [1995][1996][1997]. Moreover, both MC size and mean velocity are in phase with the solar cycle while the expansion rate is weakly variable and has no relationship with the cycle.

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“…This possibility should be borne in mind as it influences the MC magnetic flux budget, which is important for establishing the Sun -Earth link (e.g. Longcope et al, 2007;Qiu et al, 2007;Démoulin, 2008;Möstl et al, 2009). However, aside from very few events (Mulligan et al, 1999;Mulligan and Russell, 2001), the shape of the MC cross-section and its longitudinal extent are not well known due to a lack of suitable multi-spacecraft observations.…”

Section: Introductionmentioning

confidence: 99%

Optimized Grad – Shafranov Reconstruction of a Magnetic Cloud Using STEREO-Wind Observations

et al. 2009

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We present results on the geometry of a magnetic cloud (MC) on 23 May 2007 from a comprehensive analysis of Wind and STEREO observations. We first apply a GradShafranov reconstruction to the STEREO-A plasma and magnetic field data, delivered by the PLASTIC and IMPACT instruments. We then optimize the resulting field map with the aid of observations by Wind, which were made at the very outer boundary of the cloud, at a spacecraft angular separation of 6°. For the correct choice of reconstruction parameters such as axis orientation, interval and grid size, we find both a very good match between the predicted magnetic field at the position of Wind and the actual observations as well as consistent timing. We argue that the reconstruction captures almost the full extent of the cross-section of the cloud. The resulting shape transverse to the invariant axis consists of distorted ellipses and is slightly flattened in the direction of motion. The MC axis is inclined at −58°to the ecliptic with an axial field strength of 12 nT. We derive integrated axial fluxes and currents with increased precision, which we contrast with the results from linear force- free fitting. The helical geometry of the MC with almost constant twist (≈1.5 turns AU −1 ) is not consistent with the linear force-free Lundquist model. We also find that the cloud is non-force-free (|J ⊥ |/|J | > 0.3) in about a quarter of the cloud cross sectional area, particularly in the back part which is interacting with the trailing high speed stream. Based on the optimized reconstruction we put forward preliminary guidelines for the improved use of single-spacecraft Grad -Shafranov reconstruction. The results also give us the opportunity to compare the CME direction inferred from STEREO/SECCHI observations by Mierla et al. (Solar Phys. 252, 385, 2008) with the three-dimensional configuration of the MC at 1 AU. This yields an almost radial CME propagation from the Sun to the Earth.

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Modeling and Measuring the Flux Reconnected and Ejected by the Two-Ribbon Flare/CME Event on 7 November 2004

Cited by 113 publications

References 63 publications

Small-Scale Solar Magnetic Fields

Small-Scale Solar Magnetic Fields

Magnetic clouds along the solar cycle: expansion and magnetic helicity

Optimized Grad – Shafranov Reconstruction of a Magnetic Cloud Using STEREO-Wind Observations

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