[
{
"id": "authors:q5xb7-adz83",
"collection": "authors",
"collection_id": "q5xb7-adz83",
"cite_using_url": "https://authors.library.caltech.edu/records/q5xb7-adz83",
"type": "article",
"title": "Estimating Electron Densities in the Middle Solar Corona Using White-light and Radio Observations",
"author": [
{
"family_name": "Mondal",
"given_name": "Surajit",
"orcid": "0000-0002-2325-5298"
},
{
"family_name": "Shaik",
"given_name": "Shaheda Begum",
"orcid": "0000-0002-3089-3431"
},
{
"family_name": "Howard",
"given_name": "Russell A.",
"orcid": "0000-0001-9027-8249"
},
{
"family_name": "Zhang \u5f20",
"given_name": "Peijin \u6c9b\u9526",
"orcid": "0000-0001-6855-5799"
},
{
"family_name": "Chen",
"given_name": "Bin",
"orcid": "0000-0002-0660-3350"
},
{
"family_name": "Chen",
"given_name": "Xingyao",
"orcid": "0000-0002-1810-6706"
},
{
"family_name": "Yu",
"given_name": "Sijie",
"orcid": "0000-0003-2872-2614"
},
{
"family_name": "Gary",
"given_name": "Dale",
"orcid": "0000-0003-2520-8396"
},
{
"family_name": "Anderson",
"given_name": "Marin M.",
"orcid": "0000-0003-2238-2698",
"clpid": "Anderson-Marin-M"
},
{
"family_name": "Bowman",
"given_name": "Judd D.",
"orcid": "0000-0002-8475-2036"
},
{
"family_name": "Byrne",
"given_name": "Ruby",
"orcid": "0000-0003-4980-2736",
"clpid": "Byrne-Ruby"
},
{
"family_name": "Catha",
"given_name": "Morgan",
"clpid": "Catha-Morgan"
},
{
"family_name": "Chhabra",
"given_name": "Sherry",
"orcid": "0000-0001-7754-0804"
},
{
"family_name": "D'Addario",
"given_name": "Larry",
"clpid": "D'Addario-Larry"
},
{
"family_name": "Davis",
"given_name": "Ivey",
"orcid": "0000-0001-5397-5969",
"clpid": "Davis-Ivey"
},
{
"family_name": "Dowell",
"given_name": "Jayce",
"orcid": "0000-0003-1407-0141"
},
{
"family_name": "Hallinan",
"given_name": "Gregg",
"orcid": "0000-0002-7083-4049",
"clpid": "Hallinan-G"
},
{
"family_name": "Harnach",
"given_name": "Charlie",
"clpid": "Harnach-Charlie"
},
{
"family_name": "Hellbourg",
"given_name": "Greg",
"orcid": "0000-0002-8191-3885",
"clpid": "Hellbourg-Gregory"
},
{
"family_name": "Hickish",
"given_name": "Jack",
"orcid": "0000-0003-0216-1417"
},
{
"family_name": "Hobbs",
"given_name": "Rick",
"clpid": "Hobbs-Rick"
},
{
"family_name": "Hodge",
"given_name": "David",
"clpid": "Hodge-David"
},
{
"family_name": "Hodges",
"given_name": "Mark",
"clpid": "Hodges-Mark"
},
{
"family_name": "Huang",
"given_name": "Yuping",
"orcid": "0000-0003-4267-6108",
"clpid": "Huang-Yuping"
},
{
"family_name": "Isella",
"given_name": "Andrea",
"orcid": "0000-0001-8061-2207"
},
{
"family_name": "Jacobs",
"given_name": "Daniel C.",
"orcid": "0000-0002-0917-2269"
},
{
"family_name": "Kemby",
"given_name": "Ghislain",
"clpid": "Kemby-Ghislain"
},
{
"family_name": "Klinefelter",
"given_name": "John T.",
"clpid": "Klinefelter-John-T"
},
{
"family_name": "Kolopanis",
"given_name": "Matthew",
"orcid": "0000-0002-2950-2974"
},
{
"family_name": "Kosogorov",
"given_name": "Nikita",
"orcid": "0000-0003-1226-118X",
"clpid": "Kosogorov-Nikita"
},
{
"family_name": "Lamb",
"given_name": "James",
"orcid": "0000-0002-5959-1285",
"clpid": "Lamb-J-W"
},
{
"family_name": "Law",
"given_name": "Casey",
"orcid": "0000-0002-4119-9963",
"clpid": "Law-Casey-J"
},
{
"family_name": "Mahesh",
"given_name": "Nivedita",
"orcid": "0000-0003-2560-8023",
"clpid": "Mahesh-Nivedita"
},
{
"family_name": "O'Donnell",
"given_name": "Brian"
},
{
"family_name": "Plant",
"given_name": "Kathryn",
"orcid": "0000-0001-6360-6972",
"clpid": "Plant-Kathryn"
},
{
"family_name": "Posner",
"given_name": "Corey",
"clpid": "Posner-Corey"
},
{
"family_name": "Powell",
"given_name": "Travis",
"clpid": "Powell-Travis"
},
{
"family_name": "Prayag",
"given_name": "Vinand",
"clpid": "Prayag-Vinand"
},
{
"family_name": "Rizo",
"given_name": "Andres",
"clpid": "Rizo-Andres"
},
{
"family_name": "Romero-Wolf",
"given_name": "Andrew",
"orcid": "0000-0002-4992-4162",
"clpid": "Romero-Wolf-Andrew"
},
{
"family_name": "Shi",
"given_name": "Jun",
"orcid": "0000-0003-1647-7762",
"clpid": "Shi-Jun"
},
{
"family_name": "Taylor",
"given_name": "Greg",
"orcid": "0000-0001-6495-7731"
},
{
"family_name": "Trim",
"given_name": "Jordan",
"clpid": "Trim-Jordan"
},
{
"family_name": "Virgin",
"given_name": "Mike",
"clpid": "Virgin-Mike"
},
{
"family_name": "Vydula",
"given_name": "Akshatha",
"orcid": "0000-0002-6611-2668"
},
{
"family_name": "Weinreb",
"given_name": "Sandy",
"orcid": "0000-0002-9353-6204",
"clpid": "Weinreb-Sander"
},
{
"family_name": "White",
"given_name": "Scott",
"clpid": "White-Scott"
},
{
"family_name": "Woody",
"given_name": "David",
"orcid": "0000-0003-1734-2472",
"clpid": "Woody-David"
},
{
"family_name": "Zentmeyer",
"given_name": "Thomas",
"clpid": "Zentmeyer-Thomas"
}
],
"abstract": "The electron density of the solar corona is a fundamental parameter in many areas of solar physics. Traditionally, routine estimates of coronal density have relied exclusively on white-light observations. However, these density estimates, obtained by inverting the white-light data, require simplifying assumptions, which may affect the robustness of the measurements. Hence, to improve the reliability of coronal density measurements, it is highly desirable to explore other complementary methods. In this study, we estimate the coronal electron densities in the middle corona, between approximately 1.7 and 3.5 R\u2299, using low-frequency radio observations from the recently commissioned Long Wavelength Array at the Owens Valley Radio Observatory (OVRO-LWA). The results demonstrate consistency with those derived from white-light coronagraph data and predictions from theoretical models. We also derive a density model valid between 1.7 and 3.5 r\u2299, given by ρ(r′) = 1.27 r′\u207b² + 29.02 r′\u207b\u2074 + 71.18 r′\u207b\u2076, where r′ = r/R\u2299, with r the heliocentric distance. OVRO-LWA is a solar-dedicated radio interferometer that provides science-ready images with low latency, making it well suited for generating regular and independent estimates of coronal densities to complement existing white-light techniques.
",
"doi": "10.3847/1538-4357/ae4353",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2026-03-10",
"series_number": "2",
"volume": "999",
"issue": "2",
"pages": "237"
},
{
"id": "authors:ahk4j-k6h31",
"collection": "authors",
"collection_id": "ahk4j-k6h31",
"cite_using_url": "https://authors.library.caltech.edu/records/ahk4j-k6h31",
"type": "article",
"title": "Searches for Prompt Low-frequency Radio Counterparts to Gravitational-wave Event S250206dm with the OVRO-LWA Time Machine",
"author": [
{
"family_name": "Kosogorov",
"given_name": "Nikita",
"orcid": "0000-0003-1226-118X",
"clpid": "Kosogorov-Nikita"
},
{
"family_name": "Hallinan",
"given_name": "Gregg",
"orcid": "0000-0002-7083-4049",
"clpid": "Hallinan-G"
},
{
"family_name": "Law",
"given_name": "Casey",
"orcid": "0000-0002-4119-9963",
"clpid": "Law-Casey"
},
{
"family_name": "Hickish",
"given_name": "Jack",
"orcid": "0000-0003-0216-1417"
},
{
"family_name": "Dowell",
"given_name": "Jayce",
"orcid": "0000-0003-1407-0141"
},
{
"family_name": "Mooley",
"given_name": "Kunal P.",
"orcid": "0000-0002-2557-5180",
"clpid": "Mooley-Kunal-P"
},
{
"family_name": "Anderson",
"given_name": "Marin M.",
"orcid": "0000-0003-2238-2698",
"clpid": "Anderson-Marin-M"
},
{
"family_name": "Bowman",
"given_name": "Judd D.",
"orcid": "0000-0002-8475-2036"
},
{
"family_name": "Byrne",
"given_name": "Ruby",
"orcid": "0000-0003-4980-2736",
"clpid": "Byrne-Ruby"
},
{
"family_name": "Catha",
"given_name": "Morgan",
"clpid": "Catha-Morgan"
},
{
"family_name": "Chen",
"given_name": "Bin",
"orcid": "0000-0002-0660-3350"
},
{
"family_name": "Chen",
"given_name": "Xingyao",
"orcid": "0000-0002-1810-6706"
},
{
"family_name": "Chhabra",
"given_name": "Sherry",
"orcid": "0000-0001-7754-0804"
},
{
"family_name": "D'Addario",
"given_name": "Larry",
"clpid": "D'Addario-Larry"
},
{
"family_name": "Davis",
"given_name": "Ivey",
"clpid": "Davis-Ivey"
},
{
"family_name": "Elder",
"given_name": "Katherine"
},
{
"family_name": "Gary",
"given_name": "Dale",
"orcid": "0000-0003-2520-8396"
},
{
"family_name": "Harnach",
"given_name": "Charlie",
"clpid": "Harnach-Charlie"
},
{
"family_name": "Hellbourg",
"given_name": "Greg",
"orcid": "0000-0002-8191-3885",
"clpid": "Hellbourg-Gregory"
},
{
"family_name": "Hobbs",
"given_name": "Rick",
"clpid": "Hobbs-Rick"
},
{
"family_name": "Hodge",
"given_name": "David",
"clpid": "Hodge-David"
},
{
"family_name": "Hodges",
"given_name": "Mark",
"clpid": "Hodges-Mark"
},
{
"family_name": "Huang",
"given_name": "Yuping",
"clpid": "Huang-Yuping"
},
{
"family_name": "Isella",
"given_name": "Andrea",
"orcid": "0000-0001-8061-2207"
},
{
"family_name": "Jacobs",
"given_name": "Daniel C."
},
{
"family_name": "Kemby",
"given_name": "Ghislain",
"clpid": "Kemby-Ghislain"
},
{
"family_name": "Klinefelter",
"given_name": "John T.",
"clpid": "Klinefelter-John-T"
},
{
"family_name": "Kolopanis",
"given_name": "Matthew",
"orcid": "0000-0002-2950-2974"
},
{
"family_name": "Lamb",
"given_name": "James",
"orcid": "0000-0002-5959-1285",
"clpid": "Lamb-J-W"
},
{
"family_name": "Mahesh",
"given_name": "Nivedita",
"clpid": "Mahesh-Nivedita"
},
{
"family_name": "Mondal",
"given_name": "Surajit",
"orcid": "0000-0002-2325-5298"
},
{
"family_name": "O'Donnell",
"given_name": "Brian",
"orcid": "0000-0003-2802-850X"
},
{
"family_name": "Plant",
"given_name": "Kathryn",
"clpid": "Plant-Kathryn"
},
{
"family_name": "Posner",
"given_name": "Corey",
"clpid": "Posner-Corey"
},
{
"family_name": "Powell",
"given_name": "Travis",
"clpid": "Powell-Travis"
},
{
"family_name": "Prayag",
"given_name": "Vinand",
"clpid": "Prayag-Vinand"
},
{
"family_name": "Rizo",
"given_name": "Andres",
"clpid": "Rizo-Andres"
},
{
"family_name": "Romero-Wolf",
"given_name": "Andrew",
"orcid": "0000-0002-4992-4162",
"clpid": "Romero-Wolf-Andrew"
},
{
"family_name": "Shi",
"given_name": "Jun",
"orcid": "0000-0003-1647-7762",
"clpid": "Shi-Jun"
},
{
"family_name": "Taylor",
"given_name": "Greg",
"orcid": "0000-0001-6495-7731"
},
{
"family_name": "Trim",
"given_name": "Jordan",
"clpid": "Trim-Jordan"
},
{
"family_name": "Virgin",
"given_name": "Mike",
"clpid": "Virgin-Mike"
},
{
"family_name": "Vydula",
"given_name": "Akshatha",
"orcid": "0000-0002-6611-2668"
},
{
"family_name": "Weinreb",
"given_name": "Sandy",
"orcid": "0000-0002-9353-6204",
"clpid": "Weinreb-Sander"
},
{
"family_name": "White",
"given_name": "Scott",
"clpid": "White-Scott"
},
{
"family_name": "Woody",
"given_name": "David",
"orcid": "0000-0003-1734-2472",
"clpid": "Woody-David"
},
{
"family_name": "Yu",
"given_name": "Sijie",
"orcid": "0000-0003-2872-2614"
},
{
"family_name": "Zentmeyer",
"given_name": "Thomas",
"clpid": "Zentmeyer-Thomas"
},
{
"family_name": "Zhang (\u5f20\u6c9b\u9526)",
"given_name": "Peijin",
"orcid": "0000-0001-6855-5799"
}
],
"abstract": "\n
We report on a search for prompt, low-frequency radio emission from the gravitational-wave (GW) merger S250206dm using the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA). Early alerts favored a neutron-star-containing merger, making this a compelling target. Motivated by theoretical predictions of coherent radio bursts from mergers involving a neutron star, we utilized the OVRO-LWA Time Machine system to analyze voltage data recorded around the time of the event. Time Machine is a two-stage voltage buffer and processing pipeline that continuously buffers raw data from all antennas across the array’s nearly full-hemisphere instantaneous field of view, enabling retrospective beamforming, dedispersion, and fast-transient candidate identification. For this event, we analyzed a 30 minute interval beginning 3.5 minutes after the merger, which included 2 minutes of pre-alert data recovered by the ring buffer. We searched the 50% localization probability region with millisecond time resolution in the 69–86 MHz frequency band. No radio counterpart was detected above a 7σ fluence detection threshold of ∼150 Jy ms. Using Bayesian analysis, we place a 95% confidence upper limit on the source luminosity of L95 = 4 × 1041 erg s−1. These constraints start to probe the bright end of the coherent-emission parameter space predicted by jet–interstellar medium shock processes, magnetar and blitzar-like mechanisms, and recent simulation-based scenarios for neutron-star-containing mergers. This study presents the first sensitive, large-area, millisecond-timescale search for prompt low-frequency radio emission from a GW merger with the OVRO-LWA, establishing a framework in which about 10 additional events will yield stringent population-level constraints.
\n
Decades of solar coronal observations have provided substantial evidence for accelerated particles in the corona. In most cases, the location of particle acceleration can be roughly identified by combining high spatial and temporal resolution data from multiple instruments across a broad frequency range. In almost all cases, these nonthermal particles are associated with quiescent active regions, flares, and coronal mass ejections (CMEs). Only recently, some evidence of the existence of nonthermal electrons at locations outside these well-accepted regions has been found. Here, we report for the first time multiple cases of transient nonthermal emissions, in the heliocentric range of ∼3–7 R \u2299 , which do not have any obvious counterparts in other wave bands, like white-light and extreme ultraviolet. These detections were made possible by the regular availability of high dynamic-range low-frequency radio images from the Owens Valley Radio Observatory's Long Wavelength Array. While earlier detections of nonthermal emissions at these high heliocentric distances often had comparable extensions in the plane of sky, they were primarily associated with radio CMEs, unlike the cases reported here. Thus, these results add on to the evidence that the middle corona is extremely dynamic and contains a population of nonthermal electrons, which is only becoming visible with high dynamic-range low-frequency radio images.
",
"doi": "10.3847/1538-4357/ae113b",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-12-01",
"series_number": "2",
"volume": "994",
"issue": "2",
"pages": "254"
},
{
"id": "authors:6y3h7-m3t18",
"collection": "authors",
"collection_id": "6y3h7-m3t18",
"cite_using_url": "https://authors.library.caltech.edu/records/6y3h7-m3t18",
"type": "article",
"title": "A Dedicated System for Coordinated Radio and Optical Monitoring of the Space Weather of Young, Solar-type Stars",
"author": [
{
"family_name": "Davis",
"given_name": "Ivey",
"orcid": "0000-0001-5397-5969",
"clpid": "Davis-Ivey"
},
{
"family_name": "Hallinan",
"given_name": "Gregg",
"orcid": "0000-0002-7083-4049",
"clpid": "Hallinan-G"
},
{
"family_name": "Saini",
"given_name": "Navtej",
"clpid": "Saini-Navtej"
},
{
"family_name": "Law",
"given_name": "Casey",
"orcid": "0000-0002-4119-9963",
"clpid": "Law-Casey"
},
{
"family_name": "Huang",
"given_name": "Yuping",
"orcid": "0000-0003-4267-6108",
"clpid": "Huang-Yuping"
},
{
"family_name": "Burruss",
"given_name": "Rick",
"clpid": "Burruss-Rick"
},
{
"family_name": "Zolkower",
"given_name": "Jeffry",
"clpid": "Zolkower-Jeffry"
},
{
"family_name": "Baker",
"given_name": "John",
"clpid": "Baker-John"
},
{
"family_name": "Corcoran",
"given_name": "Curt",
"clpid": "Corcoran-Curt"
},
{
"family_name": "Heffner",
"given_name": "Carolyn",
"clpid": "Heffner-Carolyn"
},
{
"family_name": "Plant",
"given_name": "Kathryn",
"orcid": "0000-0001-6360-6972",
"clpid": "Plant-Kathryn"
},
{
"family_name": "Kosogorov",
"given_name": "Nikita",
"orcid": "0000-0003-1226-118X",
"clpid": "Kosogorov-Nikita"
},
{
"family_name": "Anderson",
"given_name": "Marin",
"orcid": "0000-0003-2238-2698",
"clpid": "Anderson-Marin"
},
{
"family_name": "Isella",
"given_name": "Andrea"
},
{
"family_name": "D'Addario",
"given_name": "Larry",
"clpid": "D'Addario-Larry"
},
{
"family_name": "Shi",
"given_name": "Jun",
"orcid": "0000-0003-1647-7762",
"clpid": "Shi-Jun"
},
{
"family_name": "Hellbourg",
"given_name": "Greg",
"orcid": "0000-0002-8191-3885",
"clpid": "Hellbourg-Gregory"
},
{
"family_name": "Hodge",
"given_name": "David",
"clpid": "Hodge-David"
},
{
"family_name": "Weinreb",
"given_name": "Sandy",
"orcid": "0000-0002-9353-6204",
"clpid": "Weinreb-Sandy"
},
{
"family_name": "Mahesh",
"given_name": "Nivedita",
"clpid": "Mahesh-Nivedita"
},
{
"family_name": "Byrne",
"given_name": "Ruby",
"orcid": "0000-0003-4980-2736",
"clpid": "Byrne-Ruby"
},
{
"family_name": "Hickish",
"given_name": "Jack",
"orcid": "0000-0003-0216-1417"
},
{
"family_name": "Hobbs",
"given_name": "Rick",
"clpid": "Hobbs-Rick"
},
{
"family_name": "Virgin",
"given_name": "Mike",
"clpid": "Virgin-Mike"
},
{
"family_name": "Kemby",
"given_name": "Ghislain",
"clpid": "Kemby-Ghislain"
},
{
"family_name": "Posner",
"given_name": "Corey",
"clpid": "Posner-Corey"
},
{
"family_name": "Klinefelter",
"given_name": "John T.",
"clpid": "Klinefelter-John-T"
},
{
"family_name": "Catha",
"given_name": "Morgan",
"clpid": "Catha-Morgan"
},
{
"family_name": "Lamb",
"given_name": "James",
"orcid": "0000-0002-5959-1285",
"clpid": "Lamb-J-W"
},
{
"family_name": "Hodges",
"given_name": "Mark",
"clpid": "Hodges-Mark"
},
{
"family_name": "Harnach",
"given_name": "Charlie",
"clpid": "Harnach-Charlie"
},
{
"family_name": "Prayag",
"given_name": "Vinand",
"clpid": "Prayag-Vinand"
},
{
"family_name": "Woody",
"given_name": "David",
"orcid": "0000-0003-1734-2472",
"clpid": "Woody-David"
},
{
"family_name": "Rizo",
"given_name": "Andres",
"clpid": "Rizo-Andres"
},
{
"family_name": "Romero-Wolf",
"given_name": "Andrew",
"orcid": "0000-0002-4992-4162",
"clpid": "Romero-Wolf-Andrew"
},
{
"family_name": "Bowman",
"given_name": "Judd D.",
"orcid": "0000-0002-8475-2036"
},
{
"family_name": "Jacobs",
"given_name": "Daniel C."
},
{
"family_name": "Kolopanis",
"given_name": "Matthew",
"orcid": "0000-0002-2950-2974"
},
{
"family_name": "Elder",
"given_name": "Katherine"
},
{
"family_name": "Vydula",
"given_name": "Akshatha K.",
"orcid": "0000-0002-6611-2668"
},
{
"family_name": "Gary",
"given_name": "Dale",
"orcid": "0000-0003-2520-8396"
},
{
"family_name": "Chen",
"given_name": "Bin",
"orcid": "0000-0002-0660-3350"
},
{
"family_name": "Mondal",
"given_name": "Surajit",
"orcid": "0000-0002-2325-5298"
},
{
"family_name": "Zhang",
"given_name": "Peijin",
"orcid": "0000-0001-6855-5799"
},
{
"family_name": "Yu",
"given_name": "Sijie",
"orcid": "0000-0003-2872-2614"
},
{
"family_name": "Chhabra",
"given_name": "Sherry",
"orcid": "0000-0001-7754-0804"
},
{
"family_name": "O'Donnell",
"given_name": "Brian",
"orcid": "0000-0003-2802-850X"
},
{
"family_name": "Dowell",
"given_name": "Jayce",
"orcid": "0000-0003-1407-0141"
},
{
"family_name": "Taylor",
"given_name": "Greg",
"orcid": "0000-0001-6495-7731"
}
],
"abstract": "\n
Low-frequency radio emission in the form of type II and III bursts is a direct indicator of plasma motion in the solar corona and interplanetary medium. However, detecting equivalent events on solar analogs requires thousands of observing hours and complementary multiwavelength observations to constrain the origin of the radio emission. To address this, we have begun the Study of Space Weather Around Young Suns (SWAYS), a multiwavelength program for monitoring space weather around young, solar-type stars. This program currently focuses on five solar-type stars spanning 100–800 Myr in age. It includes a dedicated observing scheme from the recently upgraded Owens Valley Radio Observatory (OVRO) Long Wavelength Array (LWA) operating at 13–86 MHz to search for stellar analogs of solar type II and III bursts. We have built the optical photometry instrument Flarescope to operate simultaneously with OVRO-LWA observations to investigate whether radio bursts are accompanied by magnetic reconnection events. We analyze the performance based on a 1 hr observation of π1 UMa, which shows that Flarescope can reach submillimagnitude precision through nondifferential photometry on π1 UMa in 60 s integration times when diffusing the light with engineered diffusers. A small field of OVRO-LWA cross-correlated data centered on π1 UMa reaches a noise level of 740 mJy at 10 s integration time, consistent with confusion noise. With this precision, we should be able to detect large optical flares and related radio bursts that may indicate accompanying coronal mass ejections and energetic particle events. In this paper, we present the design, framework, and performance of the SWAYS program.
\n
Measuring plasma parameters in the upper solar corona and inner heliosphere is challenging because of the region's weakly emissive nature and inaccessibility for most in situ observations. Radio imaging of broadened and distorted background astronomical radio sources during solar conjunction can provide unique constraints for the coronal material along the line of sight. In this study, we present radio spectral imaging observations of the Crab Nebula (Tau A) from 2024 June 9 to June 22 when it was near the Sun with a projected heliocentric distance of 5–27 solar radii, using the Owens Valley Radio Observatory's Long Wavelength Array at multiple frequencies in the 30–80 MHz range. The imaging data reveal frequency-dependent broadening and distortion effects caused by anisotropic wave propagation through the turbulent solar corona at different distances. We analyze the brightness, size, and anisotropy of the broadened images. Our results provide detailed observations showing that the eccentricity of the unresolved source increases as the line of sight approaches the Sun, suggesting a higher anisotropic ratio of the plasma turbulence closer to the Sun. In addition, the major axis of the elongated source is consistently oriented in the direction perpendicular to the radial direction, suggesting that the turbulence-induced scattering effect is more pronounced in the direction transverse to the coronal magnetic field. Lastly, when the source undergoes large-scale refraction as the line of sight passes through a streamer, the apparent source exhibits substructures at lower frequencies. This study demonstrates that observations of celestial radio sources with lines of sight near the Sun provide a promising method for measuring turbulence parameters in the inner heliosphere.
",
"doi": "10.3847/1538-4357/adff56",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-10-10",
"series_number": "1",
"volume": "992",
"issue": "1",
"pages": "128"
},
{
"id": "authors:9bjac-7yw52",
"collection": "authors",
"collection_id": "9bjac-7yw52",
"cite_using_url": "https://authors.library.caltech.edu/records/9bjac-7yw52",
"type": "article",
"title": "Possible First Detection of Gyroresonance Emission from a Coronal Mass Ejection in the Middle Corona",
"author": [
{
"family_name": "Mondal",
"given_name": "Surajit",
"orcid": "0000-0002-2325-5298"
},
{
"family_name": "Chen",
"given_name": "Bin",
"orcid": "0000-0002-0660-3350"
},
{
"family_name": "Chen",
"given_name": "Xingyao",
"orcid": "0000-0002-1810-6706"
},
{
"family_name": "Yu",
"given_name": "Sijie",
"orcid": "0000-0003-2872-2614"
},
{
"family_name": "Gary",
"given_name": "Dale",
"orcid": "0000-0003-2520-8396"
},
{
"family_name": "Zhang",
"given_name": "Peijin",
"orcid": "0000-0001-6855-5799"
},
{
"family_name": "Anderson",
"given_name": "Marin M.",
"orcid": "0000-0003-2238-2698",
"clpid": "Anderson-Marin-M"
},
{
"family_name": "Bowman",
"given_name": "Judd D.",
"orcid": "0000-0002-8475-2036"
},
{
"family_name": "Byrne",
"given_name": "Ruby",
"orcid": "0000-0003-4980-2736",
"clpid": "Byrne-Ruby"
},
{
"family_name": "Catha",
"given_name": "Morgan",
"clpid": "Catha-Morgan"
},
{
"family_name": "Chhabra",
"given_name": "Sherry",
"orcid": "0000-0001-7754-0804"
},
{
"family_name": "D'Addario",
"given_name": "Larry",
"clpid": "D'Addario-Larry"
},
{
"family_name": "Davis",
"given_name": "Ivey",
"orcid": "0000-0001-5397-5969",
"clpid": "Davis-Ivey"
},
{
"family_name": "Dowell",
"given_name": "Jayce",
"orcid": "0000-0003-1407-0141"
},
{
"family_name": "Elder",
"given_name": "Katherine"
},
{
"family_name": "Hallinan",
"given_name": "Gregg",
"orcid": "0000-0002-7083-4049",
"clpid": "Hallinan-G"
},
{
"family_name": "Harnach",
"given_name": "Charlie",
"clpid": "Harnach-Charlie"
},
{
"family_name": "Hellbourg",
"given_name": "Greg",
"orcid": "0000-0002-8191-3885",
"clpid": "Hellbourg-Gregory"
},
{
"family_name": "Hickish",
"given_name": "Jack",
"orcid": "0000-0003-0216-1417"
},
{
"family_name": "Hobbs",
"given_name": "Rick",
"clpid": "Hobbs-Rick"
},
{
"family_name": "Hodge",
"given_name": "David",
"clpid": "Hodge-David"
},
{
"family_name": "Hodges",
"given_name": "Mark",
"clpid": "Hodges-Mark"
},
{
"family_name": "Huang",
"given_name": "Yuping",
"orcid": "0000-0003-4267-6108",
"clpid": "Huang-Yuping"
},
{
"family_name": "Isella",
"given_name": "Andrea"
},
{
"family_name": "Jacobs",
"given_name": "Daniel C.",
"orcid": "0000-0002-0917-2269"
},
{
"family_name": "Kemby",
"given_name": "Ghislain",
"clpid": "Kemby-Ghislain"
},
{
"family_name": "Klinefelter",
"given_name": "John T.",
"clpid": "Klinefelter-John-T"
},
{
"family_name": "Kolopanis",
"given_name": "Matthew",
"orcid": "0000-0002-2950-2974"
},
{
"family_name": "Kosogorov",
"given_name": "Nikita",
"orcid": "0000-0003-1226-118X",
"clpid": "Kosogorov-Nikita"
},
{
"family_name": "Lamb",
"given_name": "James",
"orcid": "0000-0002-5959-1285",
"clpid": "Lamb-J-W"
},
{
"family_name": "Law",
"given_name": "Casey",
"orcid": "0000-0002-4119-9963",
"clpid": "Law-Casey"
},
{
"family_name": "Mahesh",
"given_name": "Nivedita",
"clpid": "Mahesh-Nivedita"
},
{
"family_name": "O'Donnell",
"given_name": "Brian",
"orcid": "0000-0003-2802-850X"
},
{
"family_name": "Plant",
"given_name": "Kathryn",
"orcid": "0000-0001-6360-6972",
"clpid": "Plant-Kathryn"
},
{
"family_name": "Posner",
"given_name": "Corey",
"clpid": "Posner-Corey"
},
{
"family_name": "Powell",
"given_name": "Travis",
"clpid": "Powell-Travis"
},
{
"family_name": "Prayag",
"given_name": "Vinand",
"clpid": "Prayag-Vinand"
},
{
"family_name": "Rizo",
"given_name": "Andres",
"clpid": "Rizo-Andres"
},
{
"family_name": "Romero-Wolf",
"given_name": "Andrew",
"orcid": "0000-0002-4992-4162",
"clpid": "Romero-Wolf-Andrew"
},
{
"family_name": "Shi",
"given_name": "Jun",
"orcid": "0000-0003-1647-7762",
"clpid": "Shi-Jun"
},
{
"family_name": "Taylor",
"given_name": "Greg",
"orcid": "0000-0001-6495-7731"
},
{
"family_name": "Trim",
"given_name": "Jordan",
"clpid": "Trim-Jordan"
},
{
"family_name": "Virgin",
"given_name": "Mike",
"clpid": "Virgin-Mike"
},
{
"family_name": "Vydula",
"given_name": "Akshatha",
"orcid": "0000-0002-6611-2668"
},
{
"family_name": "Weinreb",
"given_name": "Sandy",
"clpid": "Weinreb-Sandy"
},
{
"family_name": "White",
"given_name": "Scott",
"clpid": "White-Scott"
},
{
"family_name": "Woody",
"given_name": "David",
"orcid": "0000-0003-1734-2472",
"clpid": "Woody-David"
},
{
"family_name": "Zentmeyer",
"given_name": "Thomas",
"clpid": "Zentmeyer-Thomas"
}
],
"abstract": "\n
Routine measurements of the magnetic field of coronal mass ejections (CMEs) have been a key challenge in solar physics. Making such measurements is important both from a space weather perspective and for understanding the detailed evolution of the CME. In spite of significant efforts and multiple proposed methods, achieving this goal has not been possible to date. Here we report the first possible detection of gyroresonance emission from a CME. Assuming that the emission is happening at the third harmonic, we estimate that the magnetic field strength ranges from 7.9 to 5.6 G between 4.9 and 7.5 R\u2299. We also demonstrate that this high magnetic field is not the average magnetic field inside the CME, but most probably is related to small magnetic islands, which are also being observed more frequently with the availability of high-resolution and high-quality white-light images.
\n
\n
A major challenge in understanding the initiation and evolution of coronal mass ejections (CMEs) is measuring the magnetic field of the magnetic flux ropes (MFRs) that drive CMEs. Recent developments in radio imaging spectroscopy have paved the way for diagnosing the CMEs’ magnetic field using gyrosynchrotron radiation. We present magnetic field measurements of a CME associated with an X5-class flare by combining radio imaging spectroscopy data in microwaves (1–18 GHz) and meter waves (20–88 MHz), obtained by the Owens Valley Radio Observatory’s Expanded Owens Valley Solar Array (EOVSA) and Long Wavelength Array (OVRO-LWA), respectively. EOVSA observations reveal that the microwave source, observed in the low corona during the initiation phase of the eruption, outlines the bottom of the rising MFR-hosting CME bubble seen in extreme ultraviolet and expands as the bubble evolves. As the MFR erupts into the middle corona and appears as a white-light CME, its meter-wave counterpart, observed by OVRO-LWA, displays a similar morphology. For the first time, using gyrosynchrotron spectral diagnostics, we obtain magnetic field measurements of the erupting MFR in both the low and middle corona, corresponding to coronal heights of 0.02 and 1.83 R\u2299. The magnetic field strength is found to be around 300 G at 0.02 R\u2299 during the CME initiation and about 0.6 G near the leading edge of the CME when it propagates to 1.83 R\u2299. These results provide critical new insights into the magnetic structure of the CME and its evolution during the early stages of its eruption.
\n
\n
A number of theoretical studies have proposed a prompt or precursor low-frequency radio counterpart to gravitational wave events detected by LIGO and Virgo. Detection of such events would offer a new window on the immediate environment of the merger and provide an avenue to rapid localization. However, identifying fast transients in real-time in localization regions spanning hundreds to thousands of square degrees presents severe technical challenges. To address these challenges, we present a novel technique embodied in the Time Machine, a system featuring a two-stage voltage buffer and subsequent processing pipeline designed for the Long Wavelength Array at the Owens Valley Radio Observatory. This array is developed to instantaneously image the entire viewable sky. We detail the system's buffer structure that allows data collection from several minutes before a trigger event, up to 30 minutes after an event. The processing of this voltage data involves beamforming and searching the full 90th-percentile localization region above the horizon with ms-time resolution and the ability to detect events with ∼100 Jy ms (7σ) fluence within the 55–85 MHz band. Furthermore, we incorporate an offline cross-correlation pipeline to improve positional accuracy of identified transients to within subarcminute levels. We present a full overview of the system design and initial testing results.
\n