Measurement of Magnetic Helicity Injection and Free Energy Loading into the Solar Corona

Kusano, K.; Maeshiro, T.; Yokoyama, T.; Sakurai, Takashi

doi:10.1086/342171

Cited by 223 publications

(202 citation statements)

References 18 publications

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“…While in one part an accumulation of negative helicity was recorded, an injection of positive helicity was found in another part. Vemareddy et al (2012b) recognized that major flaring activity only occurred at times when helicity was injected in the AR with a sign opposite to the dominant sign of the AR (see also Kusano et al 2002). Similar findings have been presented for CME- (Wang et al 2004) and MC-productive (Chandra et al 2010) ARs.…”

Section: Helicity Buildup and Storagesupporting

confidence: 59%

The magnetic field in the solar atmosphere

Wiegelmann

Thalmann

Solanki

2014

Astron Astrophys Rev

182

125

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This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also responsible for all solar activity in its numerous manifestations. Thus, dynamic phenomena such as coronal mass ejections and flares are magnetically driven. In addition, the field also plays a crucial role in heating the solar chromosphere and corona as well as in accelerating the solar wind. Our main emphasis is the magnetic field in the upper solar atmosphere so that photospheric and chromospheric magnetic structures are mainly discussed where relevant for higher solar layers. Also, the discussion of the solar atmosphere and activity is limited to those topics of direct relevance to the magnetic field. After giving a brief overview about the solar magnetic field in general and its global structure, we discuss in more detail the magnetic field in active regions, the quiet Sun and coronal holes.

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Section: Helicity Buildup and Storagesupporting

confidence: 59%

The magnetic field in the solar atmosphere

Wiegelmann

Thalmann

Solanki

2014

Astron Astrophys Rev

182

125

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“…Deriving observationally how much magnetic helicity is injected into the atmosphere has widely been done, which is a key to the understanding of the relationship between helicity evolution and the occurrence of active phenomena including flares (Chae, 2001;Moon et al, 2002;Nindos and Zhang, 2002;Kusano et al, 2002;Démoulin and Berger, 2003;Yang et al, 2004;Pariat et al, 2005;Jeong and Chae, 2007;Magara and Tsuneta, 2008). These studies are important in that we can derive the characteristics of helicity evolution and use it to predict the occurrence of active phenomena on the Sun.…”

Section: Living Reviews In Solar Physicsmentioning

confidence: 99%

Solar Flares: Magnetohydrodynamic Processes

Shibata

Magara

2011

Living Rev. Solar Phys.

762

647

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This paper outlines the current understanding of solar flares, mainly focused on magnetohydrodynamic (MHD) processes responsible for producing a flare. Observations show that flares are one of the most explosive phenomena in the atmosphere of the Sun, releasing a huge amount of energy up to about 10 32 erg on the timescale of hours. Flares involve the heating of plasma, mass ejection, and particle acceleration that generates high-energy particles. The key physical processes for producing a flare are: the emergence of magnetic field from the solar interior to the solar atmosphere (flux emergence), local enhancement of electric current in the corona (formation of a current sheet), and rapid dissipation of electric current (magnetic reconnection) that causes shock heating, mass ejection, and particle acceleration. The evolution toward the onset of a flare is rather quasi-static when free energy is accumulated in the form of coronal electric current (field-aligned current, more precisely), while the dissipation of coronal current proceeds rapidly, producing various dynamic events that affect lower atmospheres such as the chromosphere and photosphere. Flares manifest such rapid dissipation of coronal current, and their theoretical modeling has been developed in accordance with observations, in which numerical simulations proved to be a strong tool reproducing the time-dependent, nonlinear evolution of a flare. We review the models proposed to explain the physical mechanism of flares, giving an comprehensive explanation of the key processes mentioned above. We start with basic properties of flares, then go into the details of energy build-up, release and transport in flares where magnetic reconnection works as the central engine to produce a flare.

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“…It is widely accepted that the corona is energized by photospheric or sub-photospheric activities, such as shearing motions near PILs (e.g., Kusano et al 2002;Moon et al 2002), emerging magnetic flux (e.g., Feynman & Martin 1995), and flux cancellation (e.g., Livi et al 1989). However, it is still under debate how exactly coronal eruptions are triggered.…”

Section: Introductionmentioning

confidence: 99%

A Prominence Eruption Driven by Flux Feeding From Chromospheric Fibrils

Zhang

Wang

et al. 2014

ApJ

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We present multi-wavelength observations of a prominence eruption originating from a quadrupolar field configuration, in which the prominence was embedded in a side arcade. Within the two-day period prior to its eruption on 2012 October 22, the prominence was perturbed three times by chromospheric fibrils underneath, which rose upward, became brightened, and merged into the prominence, resulting in horizontal flows along the prominence axis, suggesting that the fluxes carried by the fibrils were incorporated into the magnetic field of the prominence. These perturbations caused the prominence to oscillate and to rise faster than before. The absence of intense heating within the first two hours after the onset of the prominence eruption, which followed an exponential increase in height, indicates that ideal instability played a crucial role. The eruption involved interactions with the other side arcade, leading up to a twin coronal mass ejection, which was accompanied by transient surface brightenings in the central arcade, followed by transient dimmings and brightenings in the two side arcades. We suggest that flux feeding from chromospheric fibrils might be an important mechanism to trigger coronal eruptions.

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Measurement of Magnetic Helicity Injection and Free Energy Loading into the Solar Corona

Cited by 223 publications

References 18 publications

The magnetic field in the solar atmosphere

The magnetic field in the solar atmosphere

Solar Flares: Magnetohydrodynamic Processes

A Prominence Eruption Driven by Flux Feeding From Chromospheric Fibrils

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