Search Publications
Solar UV and X-ray spectral diagnostics
Del Zanna, Giulio; Mason, Helen E.
X-ray and ultraviolet (UV) observations of the outer solar atmosphere have been used for many decades to measure the fundamental parameters of the solar plasma. This review focuses on the optically thin emission from the solar atmosphere, mostly found at UV and X-ray (XUV) wavelengths, and discusses some of the diagnostic methods that have been us…
Sun-to-Earth MHD Simulation of the 2000 July 14 “Bastille Day” Eruption
Downs, Cooper; Riley, Pete; Linker, Jon A. +6 more
Solar eruptions are the main driver of space-weather disturbances at Earth. Extreme events are of particular interest, not only because of the scientific challenges they pose, but also because of their possible societal consequences. Here we present a magnetohydrodynamic (MHD) simulation of the 2000 July 14 “Bastille Day” eruption, which produced …
Deep Learning Based Solar Flare Forecasting Model. I. Results for Line-of-sight Magnetograms
Xu, Long; Huang, Xin; Wang, Huaning +3 more
Solar flares originate from the release of the energy stored in the magnetic field of solar active regions, the triggering mechanism for these flares, however, remains unknown. For this reason, the conventional solar flare forecast is essentially based on the statistic relationship between solar flares and measures extracted from observational dat…
Forecasting the Arrival Time of Coronal Mass Ejections: Analysis of the CCMC CME Scoreboard
Dumbović, Mateja; Temmer, Manuela; Feng, Xueshang +15 more
Accurate forecasting of the properties of coronal mass ejections (CMEs) as they approach Earth is now recognized as an important strategic objective for both NOAA and NASA. The time of arrival of such events is a key parameter, one that had been anticipated to be relatively straightforward to constrain. In this study, we analyze forecasts submitte…
Observations of Turbulent Magnetic Reconnection within a Solar Current Sheet
Cheng, X.; Ding, M. D.; Zhang, J. +4 more
Magnetic reconnection is a fundamental physical process in various astrophysical, space, and laboratory environments. Many pieces of evidence for magnetic reconnection have been uncovered. However, its specific processes that could be fragmented and turbulent have been short of direct observational evidence. Here, we present observations of a supe…
Solar Ultraviolet Bursts
Chitta, L. P.; Heinzel, Petr; Toriumi, Shin +16 more
The term "ultraviolet (UV) burst" is introduced to describe small, intense, transient brightenings in ultraviolet images of solar active regions. We inventorize their properties and provide a definition based on image sequences in transition-region lines. Coronal signatures are rare, and most bursts are associated with small-scale, canceling oppos…
Genesis and Impulsive Evolution of the 2017 September 10 Coronal Mass Ejection
Veronig, Astrid M.; Temmer, Manuela; Dissauer, Karin +7 more
The X8.2 event of 2017 September 10 provides unique observations to study the genesis, magnetic morphology, and impulsive dynamics of a very fast coronal mass ejection (CME). Combining GOES-16/SUVI and SDO/AIA EUV imagery, we identify a hot (T ≈ 10-15 MK) bright rim around a quickly expanding cavity, embedded inside a much larger CME shell (T ≈ 1-…
The 6 September 2017 X-Class Solar Flares and Their Impacts on the Ionosphere, GNSS, and HF Radio Wave Propagation
Yasyukevich, Y.; Astafyeva, E.; Padokhin, A. +3 more
On 6 September 2017, the Sun emitted two significant solar flares (SFs). The first SF, classified X2.2, peaked at 09:10 UT. The second one, X9.3, which is the most intensive SF in the current solar cycle, peaked at 12:02 UT and was accompanied by solar radio emission. In this work, we study ionospheric response to the two X-class SFs and their imp…
Successive X-class Flares and Coronal Mass Ejections Driven by Shearing Motion and Sunspot Rotation in Active Region NOAA 12673
Feng, X. S.; Yan, X. L.; Xue, Z. K. +5 more
We present a clear case study on the occurrence of two successive X-class flares, including a decade-class flare (X9.3) and two coronal mass ejections (CMEs) triggered by shearing motion and sunspot rotation in active region NOAA 12673 on 2017 September 6. A shearing motion between the main sunspots with opposite polarities began on September 5 an…
Solar total and spectral irradiance reconstruction over the last 9000 years
Solanki, S. K.; Wu, C. -J.; Krivova, N. A. +1 more
Context. Changes in solar irradiance and in its spectral distribution are among the main natural drivers of the climate on Earth. However, irradiance measurements are only available for less than four decades, while assessment of solar influence on Earth requires much longer records.
Aims: The aim of this work is to provide the most up-to-dat…