Search Publications
Global-Mode Analysis of Full-Disk Data from the Michelson Doppler Imager and the Helioseismic and Magnetic Imager
Schou, Jesper; Larson, Timothy P.
Building upon our previous work, in which we analyzed smoothed and subsampled velocity data from the Michelson Doppler Imager (MDI), we extend our analysis to unsmoothed, full-resolution MDI data. We also present results from the Helioseismic and Magnetic Imager (HMI), in both full resolution and processed to be a proxy for the low-resolution MDI …
First Analysis of Ground-Level Enhancement (GLE) 72 on 10 September 2017: Spectral and Anisotropy Characteristics
Usoskin, I.; Vainio, R.; Valtonen, E. +4 more
Using data obtained with neutron monitors and space-borne instruments, we analyzed the second ground-level enhancement (GLE) of Solar Cycle 24, namely the event of 10 September 2017 (GLE 72), and derived the spectral and angular characteristics of associated GLE particles. We employed a new neutron-monitor yield function and a recently proposed mo…
CMEs in the Heliosphere: I. A Statistical Analysis of the Observational Properties of CMEs Detected in the Heliosphere from 2007 to 2017 by STEREO/HI-1
Rodriguez, L.; Möstl, C.; Kilpua, E. K. J. +10 more
We present a statistical analysis of coronal mass ejections (CMEs) imaged by the Heliospheric Imager (HI) instruments on board NASA's twin-spacecraft STEREO mission between April 2007 and August 2017 for STEREO-A and between April 2007 and September 2014 for STEREO-B. The analysis exploits a catalogue that was generated within the FP7 HELCATS proj…
Subsurface Zonal and Meridional Flow During Cycles 23 and 24
Howe, R.; Komm, R.; Hill, F.
We study the solar-cycle variation of subsurface flows from the surface to a depth of 16 Mm. We have used ring-diagram analysis to analyze Dopplergrams obtained with the Michelson Doppler Imager (MDI) Dynamics Program, the Global Oscillation Network Group (GONG), and the Helioseismic and Magnetic Imager (HMI) instrument. We combined the zonal and …
Flux Accretion and Coronal Mass Ejection Dynamics
Welsch, Brian T.
Coronal mass ejections (CMEs) are the primary drivers of severe space weather disturbances in the heliosphere. Models of CME dynamics have been proposed that do not fully include the effects of magnetic reconnection on the forces driving the ejection. Both observations and numerical modeling, however, suggest that reconnection likely plays a major…
Densities Probed by Coronal Type III Radio Burst Imaging
Cairns, Iver H.; McCauley, Patrick I.; Morgan, John
We present coronal density profiles derived from low-frequency (80 - 240 MHz) imaging of three Type III solar radio bursts observed at the limb by the Murchison Widefield Array (MWA). Each event is associated with a white-light streamer at larger heights and is plausibly associated with thin extreme-ultraviolet rays at lower heights. Assuming harm…
Catalogue of {>} 55 MeV Wide-longitude Solar Proton Events Observed by SOHO, ACE, and the STEREOs at {≈} 1 AU During 2009 - 2016
Dresing, Nina; Heber, Bernd; Paassilta, Miikka +3 more
Based on energetic particle observations made at ≈1 AU, we present a catalogue of 46 wide-longitude (>45∘) solar energetic particle (SEP) events detected at multiple locations during 2009 - 2016. The particle kinetic energies of interest were chosen as >55 MeV for protons and 0.18 - 0.31 MeV for electrons. We make use of proton da…
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…
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…