Bulletin of the American Physical Society
Mid-Atlantic Section Fall Meeting 2020
Volume 65, Number 20
Friday–Sunday, December 4–6, 2020; Virtual
Session D03: Solar Flares at High Energy |
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Chair: Nicholeen Viall-Kepko, NASA Goddard Space Flight Center |
Saturday, December 5, 2020 9:00AM - 9:36AM |
D03.00001: Radio-based Studies of Solar Flares: Looking Ahead to the Next Solar Maximum in 2025 Invited Speaker: Dale Gary NJIT's Expanded Owens Valley Solar Array (EOVSA) has amply demonstrated the power of radio imaging spectroscopy for imaging and quantitative diagnostics of both the flaring and non-flaring Sun. The unique sensitivity of radio emission to the flaring coronal magnetic field has been dramatically shown in a series of recent papers, along with accelerated-electron diagnostics in the same volume. The coming solar maximum (cycle 25) is slated to peak in 2025-2026, which promises to bring new space- and ground-based instruments together with EOVSA to provide our best observational view of solar flares ever achieved. Here we describe the preparations underway and what we hope to learn in the coming solar cycle from radio-based studies of solar flares. [Preview Abstract] |
Saturday, December 5, 2020 9:36AM - 10:12AM |
D03.00002: Solar flare energetic electron diagnostics: Beyond hard X-ray power-law spectra Invited Speaker: Meriem Alaoui During solar flares, a large flux of highly energetic electrons is transported from the tops of reconnecting magnetic flux tubes toward the lower solar atmosphere. Substantial progress has been made in understanding the interaction of these flare-accelerated energetic electrons with their environment through observations of their X-ray spectra using the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). I will review previous conclusions regarding the accelerated electron distribution and the environment in which the nonthermal beam propagates, with a focus on recent advances about how observational deviations from single power-law distributions provide new constraints on particle propagation mechanisms and the accelerated distribution of electrons. I will present recent observational and theoretical progress toward understanding the following fundamental questions: How are the acceleration and propagation regions coupled? How much energy is deposited and at what depths in the solar atmosphere? To what extent is the shape of X-ray spectra, especially the flattening observed at lower energies (a few tens of keV) a consequence of the acceleration mechanism or propagation processes? [Preview Abstract] |
Saturday, December 5, 2020 10:12AM - 10:48AM |
D03.00003: Dynamic imaging spectroscopy at radio wavelength: new insight into energetic processes on the Sun Invited Speaker: Sijie Yu Thanks to recent advances in radio interferometric instrumentation, we've entered a new era of solar radio observations---broadband dynamic imaging spectroscopy. In this talk, I will first introduce the history of solar radio observations based on either total-power (integrated over the Sun) dynamic spectral measurements or imaging at a few discrete frequencies, then review some recent progress based on dynamic imaging spectroscopy over a wide frequency range that has placed us in a strong position to make revolutionary breakthroughs in understanding high-energy processes in the solar corona. Future perspectives will also be briefly discussed. [Preview Abstract] |
Saturday, December 5, 2020 10:48AM - 11:00AM |
D03.00004: On Propagation of Electron Holes in Current Sheets Ilya Kuzichev, Pavel Shustov, Ivan Vasko, Anton Artemyev, Andrew Gerrard Spacecraft measurements around reconnecting current sheets in the Earth's magnetotail show the presence of electron holes with distinctly different velocities. Fast electron holes are considered to be the evidence of electron bump-on-tail instabilities, while slow electron holes are thought to be the evidence of electron two-stream and Buneman instabilities. But there is another possible mechanism of formation of the slow electron holes. In the case of a sufficiently long lifetime, electron holes observed aboard a spacecraft might be generated not locally, but might reach the spacecraft from a distant generation region. In this report, we present the results of our study exploring, for the first time, this mechanism via 1.5D Vlasov simulations of the electron hole propagation in non-uniform magnetic and electric fields typical of current sheets and, particularly, of the Earth's magnetotail current sheet. We demonstrate how parameters of the electron holes evolve as the holes propagate in the inhomogeneous plasma of the current sheet. The simulations indicate that in the case of sufficiently long lifetime, slow electron holes might be indeed produced due to braking of initially fast electron holes in the course of their propagation. [Preview Abstract] |
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