Magnetic and Electric Phenomena in the Sun's Atmosphere associated with Sunspots

Giovanelli, R. G.

doi:10.1093/mnras/107.4.338

Cited by 156 publications

(52 citation statements)

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“…It began with the observations of Giovanelli (1947), while still a graduate student, that solar flares usually occurred where formation of a magnetic null was expected based on the magnetic polarities of nearby sunspots. His advisor, Sir Fred Hoyle (1949) extended this idea by suggesting that strong currents are expected at magnetic null points in the solar atmosphere and should also occur at the null points formed between the solar and geomagnetic fields, causing particle acceleration and aurora.…”

Section: Current Understanding Of Magnetic Reconnectionmentioning

confidence: 99%

Magnetospheric Multiscale Overview and Science Objectives

et al. 2015

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Magnetospheric Multiscale (MMS), a NASA four-spacecraft constellation mission launched on March 12, 2015, will investigate magnetic reconnection in the boundary regions of the Earth's magnetosphere, particularly along its dayside boundary with the solar wind and the neutral sheet in the magnetic tail. The most important goal of MMS is to conduct a definitive experiment to determine what causes magnetic field lines to reconnect in a collisionless plasma. The significance of the MMS results will extend far beyond the Earth's magnetosphere because reconnection is known to occur in interplanetary space and in the solar corona where it is responsible for solar flares and the disconnection events known as coronal mass ejections. Active research is also being conducted on reconnection in the laboratory and specifically in magnetic-confinement fusion devices in which it is a limiting factor in achieving and maintaining electron temperatures high enough to initiate fusion. Finally, reconnection is proposed as the cause of numerous phenomena throughout the universe such as comet-tail disconnection events, magnetar flares, supernova ejections, and dynamics of neutron-star accretion disks. The MMS mission design is focused on answering specific questions about reconnection at the Earth's magnetosphere. The prime focus of the mission is on determining the kinetic processes occurring in the electron diffusion region that are responsible for reconnection and that determine how it is initiated; but the mission will also place that physics into the context of the broad spectrum of physical processes associated with reconnection. Connections to other disciplines such as solar physics, astrophysics, and laboratory plasma physics are expected to be made through theory and modeling as informed by the MMS results.

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Section: Current Understanding Of Magnetic Reconnectionmentioning

confidence: 99%

Magnetospheric Multiscale Overview and Science Objectives

et al. 2015

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“…The importance of this process was first recognized in the context of solar flare observations [Giovanelli, 1947] and later in the solar windmagnetosphere system [Dungey, 1961]. In particular in the latter case, reconnection has been investigated theoretically, via both analytical studies [Petschek, 1964;Vasyliunas, 1975;Galeev et al, 1986;Biernat, 1993; 2.…”

Section: Introductionmentioning

confidence: 99%

Magnetic reconnection: Observations on October 29, 1979, and model results

Biernat¹,

Semenov²,

Drobysh³

et al. 1998

J. Geophys. Res.

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Abstract. We discuss the structure of the reconnection layer as recorded by ISEE 2 during an outbound crossing of the dayside, northern magnetopause on October 29, 1979. Besides a rotational discontinuity, this crossing shows slow mode shock structure. We interpret this event theoretically in terms of magnetic field line reconnection based on a pulse-like Petschek-type model, rather than in terms of steady state reconnection on a moving magnetopause. Our model is generalized through the introduction of a space-and time-varying reconnection rate. Furthermore, the magnetic fields and velocities on either side of the magnetopause current sheet may have arbitrary strength and orientation with respect to each other; additionally, the densities on either side of the current sheet may be different in general. Using boundary/initial conditions from the spacecraft data, we calculate the temporal/spatial behavior of all reconnection-associated structures. In particular, having chosen a suitable trajectory through the magnetopause, we consider the temporal behavior of the magnetic field and plasma parameters as these reconnection-associated events pass by. The results reproduce the behavior of the data reasonably well.

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“…Indeed, as was already recognised by Gold & Hoyle (1960), it is important for a model to include the suddenness of flaring events. In particular, they acknowledged the necessity of force-free fields to progressively store free magnetic energy, which exist prior to the flare.…”

Section: Current Layer Formation and Evolutionmentioning

confidence: 98%

Three-dimensional magnetic reconnection and its application to solar flares

Janvier

2017

J. Plasma Phys.

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Solar flares are powerful radiations occurring in the Sun's atmosphere. They are powered by magnetic reconnection, a phenomenon that can convert magnetic energy into other forms of energy such as heat and kinetic energy, and which is believed to be ubiquitous in the universe. With the ever increasing spatial and temporal resolutions of solar observations, as well as numerical simulations benefiting from increasing computer power, we can now probe into the nature and the characteristics of magnetic reconnection in three dimensions to better understand the phenomenon's consequences during eruptive flares in our star's atmosphere. We review in the following the efforts made on different fronts to approach the problem of magnetic reconnection. In particular, we will see how understanding the magnetic topology in three dimensions helps in locating the most probable regions for reconnection to occur, how the current layer evolves in three dimensions and how reconnection leads to the formation of flux ropes, plasmoids and flaring loops.

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Magnetic and Electric Phenomena in the Sun's Atmosphere associated with Sunspots

Cited by 156 publications

References 0 publications

Magnetospheric Multiscale Overview and Science Objectives

Magnetospheric Multiscale Overview and Science Objectives

Magnetic reconnection: Observations on October 29, 1979, and model results

Three-dimensional magnetic reconnection and its application to solar flares

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