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3 results on '"Binal D. Patel"'

1. Source Region and Launch Characteristics of Magnetic-arch-blowout Solar Coronal Mass Ejections Driven by Homologous Compact-flare Blowout Jets

Author

Binal D. Patel, Bhuwan Joshi, Alphonse C. Sterling, and Ronald L. Moore

Subjects
Solar coronal mass ejections, Solar active regions, Solar active region filaments, Solar flares, Solar coronal transients, Solar magnetic fields, Astrophysics, QB460-466
Abstract

We study the formation of four coronal mass ejections (CMEs) originating from homologous blowout jets. All of the blowout jets originated from NOAA Active Region (AR) 11515 on 2012 July 2, within a time interval of ≈14 hr. All of the CMEs were wide (angular widths ≈ 95°–150°), and propagated with speeds ranging between ≈300 and 500 km s ^−1 in LASCO coronagraph images. Observations at various EUV wavelengths in Solar Dynamics Observatory/Atmospheric Imaging Assembly images reveal that in all the cases, the source region of the jets lies at the boundary of the leading part of AR 11515 that hosts a small filament before each event. Coronal magnetic field modeling based on nonlinear force-free extrapolations indicates that in each case, the filament is contained inside of a magnetic flux rope that remains constrained by overlying compact loops. The southern footpoint of each filament is rooted in the negative polarity region where the eruption onsets occur. This negative polarity region undergoes continuous flux changes, including emergence and cancellation with opposite polarity in the vicinity of the flux rope, and the EUV images reveal brightening episodes near the filament’s southeastern footpoint before each eruption. Therefore, these flux changes are likely the cause of the subsequent eruptions. These four homologous eruptions originate near adjacent feet of two large-scale loop systems connecting from that positive polarity part of the AR to two remote negative polarity regions, and result in large-scale consequences in the solar corona.

Published
2024
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2. Near-Earth Interplanetary Coronal Mass Ejections and Their Association with DH Type II Radio Bursts During Solar Cycles 23 and 24

Author

Binal D. Patel, Bhuwan Joshi, Kyung-Suk Cho, Rok-Soon Kim, and Yong-Jae Moon

Subjects
Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astronomy and Astrophysics
Abstract

We analyse the characteristics of interplanetary coronal mass ejections (ICMEs) during Solar Cycles 23 and 24. The present analysis is primarily based on the near-Earth ICME catalogue (Richardson and Cane, 2010). An important aspect of this study is to understand the near-Earth and geoeffective aspects of ICMEs in terms of their association (type II ICMEs) versus absence (non-type II ICMEs) of decameter-hectometer (DH) type II radio bursts, detected by Wind/WAVES and STEREOS/WAVES. Notably, DH type II radio bursts driven by a CME indicate powerful MHD shocks leaving the inner corona and entering the interplanetary medium. We find a drastic reduction in the occurrence of ICMEs by 56% in Solar Cycle 24 compared to the previous cycle (64 versus 147 events). Interestingly, despite a significant decrease in ICME/CME counts, both cycles contain almost the same fraction of type II ICMEs (~47%). Our analysis reveals that, even at a large distance of 1 AU, type II CMEs maintain significantly higher speeds compared to non-type II events (523 km/s versus 440 km/s). While there is an obvious trend of decrease in ICME transit times with increase in the CME initial speed, there also exists a noticeable wide range of transit times for a given CME speed. Contextually, Cycle 23 exhibits 10 events with shorter transit times ranging between 20-40 hours of predominantly type II categories while, interestingly, Cycle 24 almost completely lacks such "fast" events. We find a significant reduction in the parameter $V_{ICME} \times B_{z}$, the dawn to dusk electric field, by 39% during Solar Cycle 24 in comparison with the previous cycle. Further, $V_{ICME} \times B_{z}$ shows a strong correlation with Dst index, which even surpasses the consideration of $B_{z}$ and $V_{ICME}$ alone. The above results imply the crucial role of $V_{ICME} \times B_{z}$ toward effectively modulating the geoeffectiveness of ICMEs., Comment: 26 Pages, 13 Figures

Published
2022

3. DH Type II Radio Bursts During Solar Cycles 23 and 24: Frequency-dependent Classification and their Flare-CME Associations

Author

Rok-Soon Kim, Kyung-Suk Cho, Binal D. Patel, and Bhuwan Joshi

Subjects
Physics, education.field_of_study, Density model, Population, FOS: Physical sciences, Interplanetary medium, Astronomy and Astrophysics, Astrophysics, law.invention, Multiple factors, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, law, Coronal mass ejection, Halo, Interplanetary spaceflight, education, Solar and Stellar Astrophysics (astro-ph.SR), Flare
Abstract

We present the characteristics of DH type II bursts for the Solar Cycles 23 and 24. The bursts are classified according to their end frequencies into three categories, i.e. Low Frequency Group (LFG; 20 kHz $\leq$ $f$ $\leq$ 200 kHz), Medium Frequency Group (MFG; 200 kHz $, Comment: 33 pages, 20 Figures. Accepted in Solar Physics

Published
2021

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