Search Publications
Immersed in Solar Physics
Hirayama, Tadashi
Since I have lived a rather ordinary life, my focus will center on what I have studied, with only exceptional personal matters being discussed. Nevertheless, rather new ideas are presented in Section 6.2 on the flare theory and in Section 9 on the mechanism of the 22-year solar cycle. These ideas have been included in light of my 90 years of age, …
Reconstructing Sunspot Number by Forward-Modelling Open Solar Flux
Pope, Benjamin J. S.; Lockwood, Mike; Owens, Mathew J. +4 more
The open solar flux (OSF) is the integrated unsigned magnetic flux leaving the top of the solar atmosphere to form the heliospheric magnetic field. As the OSF modulates the intensity of galactic cosmic rays at Earth, the production rate of cosmogenic isotopes - such as 14C and 10Be stored in tree rings and ice sheets - is clo…
Reconstruction of Carrington Rotation Means of Open Solar Flux over the Past 154 Years
Lockwood, Mike; Owens, Mat
We generate reconstructions of signed open solar flux (OSF) for the past 154 years using observations of geomagnetic activity. Previous reconstructions have been limited to annual resolution, but this is here increased by a factor of more than 13 by using averages over Carrington rotation (CR) intervals. We use two indices of geomagnetic activity,…
Statistical Analysis of Interplanetary Shocks from Mercury to Jupiter
Janvier, Miho; Nieves-Chinchilla, Teresa; Démoulin, Pascal +3 more
In situ observations of interplanetary (IP) coronal mass ejections (ICMEs) and IP shocks are important to study as they are the main components of solar activity. Hundreds of IP shocks have been detected by various space missions at different times and heliocentric distances. Some of these are followed by clearly identified drivers, while some oth…
Solar Energetic-Particle-Associated Coronal Mass Ejections Observed by the Mauna Loa Solar Observatory Mk3 and Mk4 Coronameters
St. Cyr, O. C.; Thompson, B. J.; Burkepile, J. T. +2 more
We report on the first comprehensive study of the coronal mass ejections (CMEs) associated with ∼25 MeV solar energetic-proton (SEP) events in 1980 - 2013 observed in the low/inner corona by the Mauna Loa Solar Observatory (MLSO) Mk3 and Mk4 coronameters. Where possible, these observations are combined with space-based observations from the Solar …
Multi-Spacecraft Observations of an Interplanetary Coronal Mass Ejection Interacting with Two Solar-Wind Regimes Observed by the Ulysses and Twin-STEREO Spacecraft
Foullon, Claire; Barnes, David; Davies, Jackie +2 more
We present a combined study of a coronal mass ejection (CME), revealed in a unique orbital configuration that permits the analysis of remote-sensing observations on 27 June 2007 from the twin Solar Terrestrial Relations Observatory (STEREO)-A and -B spacecraft and of its subsequent in situ counterpart outside the ecliptic plane, the interplanetary…
Migrating Dynamo Waves and Consequences for Stellar Current Sheets
Sokoloff, Dmitry; Malova, Helmi; Popov, Victor +2 more
We study the relation between stellar dynamo-wave propagation and the structure of the stellar magnetic field. Modeling dynamo waves by the well-known Parker migratory dynamo, we vary the intensity of dynamo drivers in order to obtain activity-wave propagation toward the Equator (as in the solar-activity cycle) or towards the Poles. We match the m…
Solar-Wind High-Speed Stream (HSS) Alfvén Wave Fluctuations at High Heliospheric Latitudes: Ulysses Observations During Two Solar-Cycle Minima
Hajra, Rajkumar; Echer, Ezequiel; Franco, Adriane Marques de Souza +2 more
We study Alfvén wave fluctuations in solar-wind high-speed streams (HSSs) at high heliolatitudes during the last two solar-cycle minima (SCM). Solar-wind plasma and interplanetary magnetic field (IMF) measured by Ulysses during four 50-day intervals in 1994, 1995, 2007, and 2008 were analyzed using wavelet and Fourier analyses, cross-correlation a…
Active Region Contributions to the Solar Wind over Multiple Solar Cycles
van Driel-Gesztelyi, Lidia; Green, Lucie M.; Horbury, Timothy S. +1 more
Both coronal holes and active regions are source regions of the solar wind. The distribution of these coronal structures across both space and time is well known, but it is unclear how much each source contributes to the solar wind. In this study we use photospheric magnetic field maps observed over the past four solar cycles to estimate what frac…
LASCO-C3 Observations of the K- and F-Coronae over 24 Years (1996 - 2019): Photopolarimetry and Electron Density Distribution
Lamy, Philippe; Quémerais, Eric; Gilardy, Hugo +2 more
We present the polarimetric analysis of the white-light images of the corona obtained with the Large-Angle Spectrometric COronagraph LASCO-C3 onboard the Solar and Heliospheric Observatory (SOHO) from 1996 to 2019, leading to the separation of the K- and F-components and the derivation of the electron-density distribution. The analysis makes use o…