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 D02: Solar Corona |
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Chair: Sijie Yu, New Jersey Institute of Technology Room: 201B |
Saturday, December 4, 2021 11:15AM - 11:51AM |
D02.00001: An automated framework for 3D data-constrained modeling of the coronal magneto-thermal structure of solar active regions Invited Speaker: Gelu Nita Data-constrained modeling of the coupling between the magnetic and thermal structures of solar active regions (ARs) is a crucial step towards understanding the source region of flares and coronal mass ejections. GX Simulator is a publicly available data-constrained 3D modeling package distributed through the SolarSoftWare (SSW) IDL repository, which has been developed for modeling multiwavelength emission in the microwave, X-ray, and EUV ranges from flaring loops (Nita et al. 2015, ApJ 799, 236) and solar active regions (Nita et al. 2018, ApJ 853, 66). To facilitate its use, a fully automatic GX Simulator-compatible model production pipeline (AMPP) has been developed. Based on minimal user input, provided as a script or through an intuitive graphical user interface (GUI), the AMPP downloads the required vector magnetic field data produced by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) and, optionally, the contextual Atmospheric Imaging Assembly (AIA) maps, performs potential and/or nonlinear force free field extrapolations, populates the volume with thermal coronal models that assume either steady-state or impulsive plasma heating, and generates non-LTE density and temperature distribution models of the chromosphere that are constrained by photosphere-level measurements. The standardized models produced by AMPP may be further customized through a set of GX Simulator interactive GUI tools, but the iterative search for the best model parameters for agreement between the model and observations is a time-consuming task that calls for a more efficient, automated approach. To this end, we have developed a coronal heating modeling pipeline (CHMP), which is a fully automated multi-threaded search engine that adaptively steps through a multi-dimensional parameter space to produce parametrized test models and generate synthetic maps, which are automatically compared with the reference observational data until the desired level of agreement is achieved, as measured by objective data-to-model comparison metrics. In this presentation, I will describe the architecture of the AMPP and CHMP components of the GX Simulator package and demonstrate their functionality in the case of a particular solar active region [Preview Abstract] |
Saturday, December 4, 2021 11:51AM - 12:27PM |
D02.00002: Characterizing weak impulsive narrowband radio emissions from the quiet solar corona$\backslash $ Invited Speaker: Surajit Mondal h $-abstract-$\backslash $pard In the past decade, significant advances have been made towards understanding and solving the coronal heating problem. There has been a number of observational evidences which suggest that the hypothesized "nanoflares" play a significant role in heating the corona. However to the best of our knowledge, these studies mainly focussed on understanding heating of the corona in the vicinity of the active regions, which are generally regions which harbor strong magnetic field. However the quiet corona is also hot, and often comprises the bulk of the corona. So it is equally important to understand the physical processes which maintain it at MK temperatures. If these nanoflares are happening even in the quiet solar corona, transient radio emissions are expected to be observed from the quiet sun. Hence detection these weak transient emissions would suggest that small scale reconnections are happening through out the corona and giving rise to nanoflares. By pushing the detection threshold of non-thermal emission by about two orders of magnitude lower than previous studies, Mondal et al. (2020) uncovered evidence of ubiquitous presence of reconnections throughout the quiet sun. We are continuing to explore different aspects of these impulsive nonthermal emissions, ranging from their spectral characteristics, temporal properties, energetics etc. I will summarize the status of these investigations in this presentation.$\backslash $pard-/abstract-$\backslash $\tex [Preview Abstract] |
Saturday, December 4, 2021 12:27PM - 12:39PM |
D02.00003: Multiple Regions of Radio Quasi-Periodic Pulsations during the Impulsive Phase of a C1.8 Solar Flare Yingjie Luo, Bin Chen, Sijie Yu, Marina Battaglia, Rohit Sharma Flare-associated Quasi-periodic pulsations (QPPs) can reveal essential energy release, transport, and modulation processes during flares. However, the paucity of spatially resolved observations with a fast time cadence blocks us from improve our understanding of the physical nature of such QPPs. Here, we report ultra-high cadence radio imaging spectroscopy observations of QPPs using data from Karl G. Jansky Very Large Array (VLA) during the impulsive phase of a C1.8-class solar flare on February 18, 2016. The radio QPPs, observed in the 1--2 GHz L band with a sub-second cadence, consist of three spatially distinct radio sources with different physical characteristics, including periodicity, duration, bandwidth, and polarization. Two QPP sources are located near the conjugate footpoints of the brightening flare arcades with the opposite sense of polarization. An additional QPP source coincides with the location of a looptop X-ray source, which also shows a similar quasi-periodic pattern in its light curve. We suggest that the two footpoint radio QPP sources are likely due to electron cyclotron maser emission from trapped energetic electrons, while the looptop radio/X-ray QPP source may be more inherently related to modulations of the flare energy release. [Preview Abstract] |
Saturday, December 4, 2021 12:39PM - 12:51PM |
D02.00004: Coronal Magnetic Field Measurements along a Partially Erupting Filament in a Solar Flare Yuqian Wei, Bin Chen, Sijie Yu, Haimin Wang, Ju Jing, Dale Gary Magnetic flux ropes are the centerpiece of solar eruptions. Direct measurements for the magnetic field of flux ropes are crucial for understanding the triggering and energy release processes, yet they remain heretofore elusive. Here we report microwave imaging spectroscopy observations of an M1.4-class solar flare that occurred on 2017 September 6, using data obtained by the Expanded Owens Valley Solar Array. This flare event is associated with a partial eruption of a twisted filament observed in H$\alpha$ by the Goode Solar Telescope at the Big Bear Solar Observatory. The extreme ultraviolet (EUV) and X-ray signatures of the event are generally consistent with the standard scenario of eruptive flares, with the presence of double flare ribbons connected by a bright flare arcade. Intriguingly, this partial eruption event features a microwave counterpart, whose spatial and temporal evolution closely follow the filament seen in H$\alpha$ and EUV. The spectral properties of the microwave source are consistent with nonthermal gyrosynchrotron radiation. Using spatially resolved microwave spectral analysis, we derive the magnetic field strength along the filament spine, which ranges from 600--1400 Gauss from its apex to the legs. The results agree well with the non-linear force-free mag [Preview Abstract] |
Saturday, December 4, 2021 12:51PM - 1:03PM |
D02.00005: An In Situ Type III Radio Burst Event Observed Jointly by the Expanded Owens Valley Solar Array and the Parker Solar Probe Meiqi Wang, Bin Chen, Sijie Yu, Dale Gary, Jeongwoo Lee Solar type III radio bursts are generated by beams of energetic electrons that travel outward along open magnetic field lines through the corona and the interplanetary space. Here we report a type III burst event observed jointly by the Expanded Owens Valley Solar Array (EOVSA) and the Parker Solar Probe (PSP) shortly after its second perihelion in April 2019. This type III burst event is associated with a solar jet near the western boundary of a solar active region, which manifests in EOVSA 1--18 GHz dynamic spectrum as a group of impulsive microwave bursts. The type III burst event continues to the interplanetary space in the decameter--kilometer wavelength range (300 kHz--30 MHz) observed by multiple spacecraft including PSP/FIELDS, Wind/WAVEs, and STEREO/WAVES, and appears to reach the local plasma frequency at the PSP spacecraft. The multi-point spacecraft measurements allow us to constrain the source location of the bursts and their directivity in the interplanetary space. In addition, the type III burst event coincides with an enhanced suprathermal electron population with an anti-sunward beam-like component as measured by PSP/SWEAP. We argue that the type-III-burst-emitting energetic electrons observed in situ may be associated with an electron beam produced during the jet event that propagating upwards along open field lines reaching the PSP spacecraft. [Preview Abstract] |
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