Search Publications
Nowcasting Solar Energetic Particle Events Using Principal Component Analysis
Vainio, R.; Valtonen, E.; Papaioannou, A. +7 more
We perform a principal component analysis (PCA) on a set of six solar variables (i.e. width/size (s ) and velocity (u ) of a coronal mass ejection, logarithm of the solar flare (SF) magnitude (logSXRs ), SF longitude (lon ), duration (DT ), and rise time (RT )). We classify the solar energetic particle (SEP) event radiation impact (in terms of the…
IRIS Observations of Spicules and Structures Near the Solar Limb
Vial, J. -C.; Alissandrakis, C. E.; Buchlin, E. +2 more
We have analyzed Interface Region Imaging Spectrograph (IRIS) spectral and slit-jaw observations of a quiet region near the South Pole. In this article we present an overview of the observations, the corrections, and the absolute calibration of the intensity. We focus on the average profiles of strong (Mg II h and k, C II and Si IV), as well as of…
A Major Geoeffective CME from NOAA 12371: Initiation, CME-CME Interactions, and Interplanetary Consequences
Joshi, Bhuwan; Shanmugaraju, A.; Chakrabarty, D. +1 more
In this article, we present a multi-wavelength and multi-instrument investigation of a halo coronal mass ejection (CME) from active region NOAA 12371 on 21 June 2015 that led to a major geomagnetic storm of minimum Dst =−204 nT. The observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory in the hot EUV channel of …
Automated Identification of Coronal Holes from Synoptic EUV Maps
Asikainen, Timo; Mursula, Kalevi; Virtanen, Ilpo +1 more
Coronal holes (CHs) are regions of open magnetic field lines in the solar corona and the source of the fast solar wind. Understanding the evolution of coronal holes is critical for solar magnetism as well as for accurate space weather forecasts. We study the extreme ultraviolet (EUV) synoptic maps at three wavelengths (195 Å/193 Å, 171 Å and 304 Å…
Connecting Coronal Mass Ejections to Their Solar Active Region Sources: Combining Results from the HELCATS and FLARECAST Projects
Gallagher, Peter T.; Murray, Sophie A.; Guerra, Jordan A. +5 more
Coronal mass ejections (CMEs) and other solar eruptive phenomena can be physically linked by combining data from a multitude of ground-based and space-based instruments alongside models; however, this can be challenging for automated operational systems. The EU Framework Package 7 HELCATS project provides catalogues of CME observations and propert…
Magnetic Clouds: Solar Cycle Dependence, Sources, and Geomagnetic Impacts
Luhmann, J. G.; Li, Y.; Lynch, B. J.
Magnetic clouds (MCs) are transient magnetic structures giving the strongest southward magnetic field (Bz south) in the solar wind. The sheath regions of MCs may also carry a southward magnetic field. The southward magnetic field is responsible for space-weather disturbances. We report a comprehensive analysis of MCs and Bz components in their she…
Statistical Properties of Ribbon Evolution and Reconnection Electric Fields in Eruptive and Confined Flares
Veronig, A. M.; Thalmann, J. K.; Pötzi, W. +2 more
A statistical study of the chromospheric ribbon evolution in Hα two-ribbon flares was performed. The data set consists of 50 confined (62%) and eruptive (38%) flares that occurred from June 2000 to June 2015. The flares were selected homogeneously over the Hα and Geostationary Operational Environmental Satellite (GOES) classes, with an emphasis on…
Radio, Hard X-Ray, and Gamma-Ray Emissions Associated with a Far-Side Solar Event
Zimovets, I. V.; Grechnev, V. V.; Mitrofanov, I. G. +9 more
The far-side solar eruptive event SOL2014-09-01 produced hard electromagnetic and radio emissions that were observed with detectors at near-Earth vantage points. Especially challenging was a long-duration > 100 MeV γ -ray burst that was probably produced by accelerated protons exceeding 300 MeV. This observation raised the question how high-ene…
Fragile Detection of Solar g -Modes by Fossat et al.
Gizon, Laurent; Gaulme, Patrick; Schou, Jesper +1 more
The internal gravity modes of the Sun are notoriously difficult to detect, and the claimed detection of gravity modes presented by Fossat et al. (Astron. Astrophys.604, A40, 2017) is thus very exciting. Given the importance of these modes for understanding solar structure and dynamics, the results must be robust. While Fossat et al. described thei…
A Solar Stationary Type IV Radio Burst and Its Radiation Mechanism
Koval, Artem; Chen, Yao; Feng, Shiwei +6 more
A stationary Type IV (IVs) radio burst was observed on September 24, 2011. Observations from the Nançay RadioHeliograph (NRH) show that the brightness temperature (TB) of this burst is extremely high, over 1011 K at 150 MHz and over 108 K in general. The degree of circular polarization (q ) is between −60 % ∼−100 %…