Scholarly Work - Physics
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/3458
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Item Tracing field lines that are reconnecting, or expanding, or both(Frontiers Media SA, 2024-07) Qiu, JiongThe explosive release of energy in the solar atmosphere is driven magnetically, but the mechanisms that trigger the onset of the eruption remain controversial. In the case of flares and coronal mass ejections (CMEs), ideal or non-ideal instabilities usually occur in the corona, but it is difficult to obtain direct observations and diagnostics there. To overcome this difficulty, we analyze observational signatures in the upper chromosphere or transition region, particularly brightening and dimming at the base of coronal magnetic structures. In this paper, we examine the time evolution of spatially resolved light curves in two eruptive flares and identify a variety of tempo-spatial sequences of brightening and dimming, such as dimming followed by brightening and dimming preceded by brightening. These brightening–dimming sequences are indicative of the configuration of energy release in the form of plasma heating or bulk motion. We demonstrate the potential of using these analyses to diagnose the properties of magnetic reconnection and plasma expansion in the corona during the early stages of the eruption.Item Tracing field lines that are reconnecting, or expanding, or both(Frontiers Media SA, 2024-07) Qiu, JiongThe explosive release of energy in the solar atmosphere is driven magnetically, but the mechanisms that trigger the onset of the eruption remain controversial. In the case of flares and coronal mass ejections (CMEs), ideal or non-ideal instabilities usually occur in the corona, but it is difficult to obtain direct observations and diagnostics there. To overcome this difficulty, we analyze observational signatures in the upper chromosphere or transition region, particularly brightening and dimming at the base of coronal magnetic structures. In this paper, we examine the time evolution of spatially resolved light curves in two eruptive flares and identify a variety of tempo-spatial sequences of brightening and dimming, such as dimming followed by brightening and dimming preceded by brightening. These brightening–dimming sequences are indicative of the configuration of energy release in the form of plasma heating or bulk motion. We demonstrate the potential of using these analyses to diagnose the properties of magnetic reconnection and plasma expansion in the corona during the early stages of the eruption.Item Correlated Spatio-temporal Evolution of Extreme-Ultraviolet Ribbons and Hard X-Rays in a Solar Flare(American Astronomical Society, 2022-02) Naus, S. J.; Qiu, J.; DeVore, C. R.; Antiochos, S. K.; Dahlin, J. T.; Drake, J. F.; Swisdak, M.We analyze the structure and evolution of ribbons from the M7.3 SOL2014-04-18T13 flare using ultraviolet images from the Interface Region Imaging Spectrograph and the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA), magnetic data from the SDO/Helioseismic and Magnetic Imager, hard X-ray (HXR) images from the Reuven Ramaty High Energy Solar Spectroscopic Imager, and light curves from the Fermi/Gamma-ray Burst Monitor, in order to infer properties of coronal magnetic reconnection. As the event progresses, two flare ribbons spread away from the magnetic polarity inversion line. The width of the newly brightened front along the extension of the ribbon is highly intermittent in both space and time, presumably reflecting nonuniformities in the structure and/or dynamics of the flare current sheet. Furthermore, the ribbon width grows most rapidly in regions exhibiting concentrated nonthermal HXR emission, with sharp increases slightly preceding the HXR bursts. The light curve of the ultraviolet emission matches the HXR light curve at photon energies above 25 keV. In other regions the ribbon-width evolution and light curves do not temporally correlate with the HXR emission. This indicates that the production of nonthermal electrons is highly nonuniform within the flare current sheet. Our results suggest a strong connection between the production of nonthermal electrons and the locally enhanced perpendicular extent of flare ribbon fronts, which in turn reflects the inhomogeneous structure and/or reconnection dynamics of the current sheet. Despite this variability, the ribbon fronts remain nearly continuous, quasi-one-dimensional features. Thus, although the reconnecting coronal current sheets are highly structured, they remain quasi-two-dimensional and the magnetic energy release occurs systematically, rather than stochastically, through the volume of the reconnecting magnetic flux.