Search Publications
High-Resolution Spectral and Anisotropy Characteristics of Solar Protons During the GLE N∘73 on 28 October 2021 Derived with Neutron-Monitor Data Analysis
Vainio, Rami; Riihonen, Esa; Mishev, Alexander L. +4 more
The first ground-level enhancement of the current Solar Cycle 25 occurred on 28 October 2021. It was observed by several space-borne and ground-based instruments, specifically neutron monitors. A moderate count-rate increase over the background was observed by high-altitude polar stations on the South Pole and Dome C stations at the Antarctic plat…
First Hard X-Ray Imaging Results by Solar Orbiter STIX
Volpara, Anna; Massa, Paolo; Krucker, Säm +15 more
The Spectrometer/Telescope for Imaging X-rays (STIX) is one of six remote sensing instruments on-board Solar Orbiter. The telescope applies an indirect imaging technique that uses the measurement of 30 visibilities, i.e., angular Fourier components of the solar flare X-ray source. Hence, the imaging problem for STIX consists of the Fourier inversi…
Transverse Coronal-Loop Oscillations Induced by the Non-radial Eruption of a Magnetic Flux Rope
Li, D.; Zhang, Q. M.; Lu, L. +2 more
We investigate the transverse coronal-loop oscillations induced by the eruption of a prominence-carrying flux rope on 7 December 2012. The flux rope, originating from NOAA Active Region (AR) 11621, was observed in extreme-ultraviolet (EUV) wavelengths by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) spacecraft…
Group Sunspot Numbers: A New Reconstruction of Sunspot Activity Variations from Historical Sunspot Records Using Algorithms from Machine Learning
Velasco Herrera, Víctor Manuel; Soon, Willie; Hoyt, Douglas V. +1 more
Historical sunspot records and the construction of a comprehensive database are among the most sought after research activities in solar physics. Here, we revisit the issues and remaining questions on the reconstruction of the so-called group sunspot numbers (GSN) that was pioneered by D. Hoyt and colleagues. We use the modern tools of artificial …
Invited Review: Short-term Variability with the Observations from the Helioseismic and Magnetic Imager (HMI) Onboard the Solar Dynamics Observatory (SDO): Insights into Flare Magnetism
Kazachenko, Maria D.; Welsch, Brian T.; Albelo-Corchado, Marcel F. +1 more
Continuous vector magnetic-field measurements by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) allow us to study magnetic-field properties of many flares. Here, we review new observational aspects of flare magnetism described using SDO data, including statistical properties of magnetic-reconnection fluxes …
Exploring the Circular Polarisation of Low-Frequency Solar Radio Bursts with LOFAR
Kumari, Anshu; Zucca, Pietro; Vocks, Christian +9 more
The Sun is an active star that often produces numerous bursts of electromagnetic radiation at radio wavelengths. Low frequency radio bursts have recently been brought back to light with the advancement of novel radio interferometers. However, their polarisation properties have not yet been explored in detail, especially with the Low Frequency Arra…
Extreme-Ultraviolet Wave and Accompanying Loop Oscillations
Awasthi, Arun Kumar; Schmieder, Brigitte; Joshi, Reetika +2 more
We present the observations of an extreme-ultraviolet (EUV) wave, which originated from the active region (AR) NOAA 12887 on 28 October 2021, and its impact on neighboring loops. The event was observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) satellite at various wavebands and by the Solar TErrestrial…
A Simple Radial Gradient Filter for Batch-Processing of Coronagraph Images
Pant, Vaibhav; Banerjee, Dipankar; Patel, Ritesh +1 more
Images of the extended solar corona, as observed by different white-light coronagraphs, include the K- and F-corona and suffer from a radial variation in intensity. These images require separation of the two coronal components with some additional image-processing to reduce the intensity gradient and analyse the structures and processes occurring …
Disambiguation of Vector Magnetograms by Stereoscopic Observations from the Solar Orbiter (SO)/Polarimetric and Helioseismic Imager (PHI) and the Solar Dynamic Observatory (SDO)/Helioseismic and Magnetic Imager (HMI)
Hirzberger, Johann; Valori, Gherardo; Chen, Feng +3 more
Spectropolarimetric reconstructions of the photospheric vector magnetic field are intrinsically limited by the 180∘ ambiguity in the orientation of the transverse component. The successful launch and operation of Solar Orbiter have made the removal of the 180∘ ambiguity possible using solely observations obtained from two dif…
Interplanetary Sheaths and Corotating Interaction Regions: A Comparative Statistical Study on Their Characteristics and Geoeffectiveness
Hajra, Rajkumar; Sunny, Jibin V.; Babu, Megha +1 more
Interplanetary sheaths and corotating interaction regions (CIRs), while having different solar sources, represent turbulent solar-wind plasma and magnetic field that can perturb the Earth's magnetosphere. We explore long-term solar-wind measurements upstream of the Earth during Solar Cycle 24, from January 2008 to December 2019, to compare their s…