Bulletin of the American Physical Society
Mid-Atlantic Section Meeting 2021
Volume 66, Number 18
Friday–Sunday, December 3–5, 2021; Rutgers University, New Brunswick, New Jersey
Session B02: Solar Eruptions |
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Chair: Sijie Yu, New Jersey Institute of Technology Room: 201B |
Friday, December 3, 2021 5:00PM - 5:36PM |
B02.00001: Implications of electron beam propagation and its associated return current on energy deposition in solar flares Invited Speaker: Meriem Alaoui During solar flares, a large flux of energetic electrons propagate from the tops of reconnecting magnetic flux tubes toward the lower atmosphere. Over the course of the electrons' transport, a co-spatial counter-streaming return current is induced, thereby balancing the current density. In response to the return current electric field, a fraction of the ambient electrons will be accelerated into the runaway regime. In a recent paper, we developed a model describing the accelerated electron beam/return-current system which self-consistently accounts for these suprathermal runaway electrons. I will show a systematic study of the effect of the return current on the energy deposition by the electron beam in the corona versus the chromosphere by varying the beam parameters (total electron flux density, spectral index, and low-energy cutoff) and the initial atmosphere in which the beam is injected. [Preview Abstract] |
Friday, December 3, 2021 5:36PM - 6:12PM |
B02.00002: The Nature of Solar Flare Reconnection Invited Speaker: Joel Dahlin Solar flares are among the most energetic events in the solar system, capable of releasing over 10^32 ergs in the forms of heating, energetic particles, and bulk motion. This energy release is known to be driven by magnetic reconnection, a plasma process that explosively releases stored magnetic energy through a rearrangement of the magnetic topology. Determining the structure and dynamics of flare reconnection is therefore essential for modeling and predicting the energy release channels of these events. Whereas direct observation of the reconnection dynamics is difficult, detailed constraints on the dynamics can be obtained from the “flare ribbons” that track the chromospheric footpoints of newly reconnected field lines and the “flare loops” of very hot (>10MK) plasma that illuminate the reconnected magnetic structures. We present a new high-resolution, three-dimensional magnetohydrodynamics model of a solar flare performed with the ARMS code. In our model, the flare ribbons exhibit characteristic ‘whorls’ that represent indirect evidence of reconnection-generated structures known as plasmoids that are thought to be important for particle acceleration. We furthermore show that the orientation of the flare loops reveals important information about the so-called ‘guide magnetic field’ thought to play a critical role in plasmoid structure and associated particle acceleration efficiency. We discuss implications for understanding how, when, and where solar flares accelerate particles. [Preview Abstract] |
Friday, December 3, 2021 6:12PM - 6:24PM |
B02.00003: What Condition is Necessary for Solar Eruptions? Satoshi Inoue We conducted a magnetohydrodynamic (MHD) simulation of solar active region 12673. This active region produced huge X-flares on September 6 2017, but our recent study found that the magnetic flux rope (MFR), which is a bundle of the twisted magnetic field lines and caused the X-flares, stably existed as of 2 days before the X-flares takes place (Yamasaki et al.. 2021). The purpose of this study is to reveal what condition is necessary for the eruption of the MFR, as of September 4, in the region where the X-flares occurred. We used a non-linear force-free field (NLFFF) as the initial condition of the simulation that is reconstructed from the observed photospheric magnetic field. As a result, although the NLFFF, which includes highly twisted field lines, was stable to small disturbances, the eruption could be achieved if the highly twisted MFR which is composed of strongly twisted lines with more than one-turn is formed through the reconnection. We estimated a ratio of the magnetic flux of the newly created MFR and the magnetic field lines surrounding it before the eruption. We found that when the flux ratio is over $\sim$ 0.1, the MFR could be driven upward before it becomes torus instability which is considered as a strong candidate for the onset mechanism of the MFR eruptions. [Preview Abstract] |
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