Search Publications
An Extended Study of the Precursory Signs of Forbush Decreases: New Findings over the Years 2008 - 2016
Mavromichalaki, H.; Belov, A.; Eroshenko, E. +3 more
In spite of the fact that the current Solar Cycle 24 is close to its end now, it is a less active Solar Cycle, during its time period (2008 - 2016) and a lot of Forbush decreases of cosmic ray intensity with rigidity 10 GV and amplitude greater than 2% were recorded by the ground-based neutron monitors. Among these events, the ones associated with…
Study of Sunspot Penumbra to Umbra Area Ratio Using Kodaikanal White-light Digitised Data
Banerjee, Dipankar; Jha, Bibhuti Kumar; Mandal, Sudip
We study the long-term behaviour of the sunspot penumbra to umbra area ratio by analysing recently digitised Kodaikanal white-light data (1923 - 2011). We implement an automatic umbra extraction method and compute the ratio over eight solar cycles (Cycles 16 - 23). Although the average ratio does not show any variation with spot latitudes, cycle p…
Parametric Study of ICME Properties Related to Space Weather Disturbances via a Series of Three-Dimensional MHD Simulations
Moon, Yong-Jae; Magara, Tetsuya; Hayashi, Keiji +1 more
Interplanetary coronal mass ejections (ICMEs) are important drivers of space-weather disturbances observed at the Earth. We use a parameterized ICME model to investigate the relation between the physical properties of an ICME and these disturbances. Compared to those studies focused on deriving a best set of ICME parameter values matched with obse…
On the Power-Law Distribution of Pitch-Angle Scattering Times in Solar Wind Turbulence
Zimbardo, Gaetano; Perri, Silvia; Pucci, Francesco +1 more
The propagation of energetic particles in the solar wind depends in a sensitive way on the pitch-angle scattering of particles in the presence of magnetic turbulence. The well-known quasi-linear theory gives an expression for the pitch-angle scattering rate under the assumption of small turbulence levels, but both in the solar wind and in other as…
Excess H, Suppressed He, and the Abundances of Elements in Solar Energetic Particles
Reames, Donald V.
Recent studies of the abundances of H and He relative to those of heavier ions in solar energetic particle (SEP) events suggest new features in the underlying physics. Impulsive SEP events, defined by uniquely large enhancements of Fe/O, emerge from magnetic reconnection in solar jets. In small, "pure," shock-free, impulsive SEP events, protons wi…
New Evidence for Third Harmonic Electromagnetic Radiation in Interplanetary Type III Solar Radio Bursts
MacDowall, R. J.; Reiner, M. J.
This article provides new evidence for a third harmonic component in the electromagnetic radiation generated by interplanetary type III solar radio bursts observed locally near 1 AU. This evidence comes mainly from the analysis of the low-frequency radio emissions observed by the Wind spacecraft. The analysis examines, at high-time and high-freque…
Modeling the Global Distribution of Solar Wind Parameters on the Source Surface Using Multiple Observations and the Artificial Neural Network Technique
Shen, Fang; Yang, Yi
The global distribution of magnetic field and other plasma parameters on the source surface, which we set at 2.5 solar radii, is important for coronal and heliospheric modeling. In this article, we introduce a new data-driven self-consistent method to obtain the global distribution of different parameters. The magnetic and polarized brightness (p …
Estimation of Arrival Time of Coronal Mass Ejections in the Vicinity of the Earth Using SOlar and Heliospheric Observatory and Solar TErrestrial RElations Observatory Observations
Ravishankar, Anitha; Michałek, Grzegorz
The arrival time of coronal mass ejections (CMEs) in the vicinity of the Earth is one of the most important parameters in determining space weather. We have used a new approach to predicting this parameter. First, in our study, we have introduced a new definition of the speed of ejection. It can be considered as the maximum speed that the CME achi…
Coordinated Interplanetary Scintillation Observations in Japan and Russia for Coronal Mass Ejection Events in Early September 2017
Tokumaru, Munetoshi; Fujiki, Ken'ichi; Iwai, Kazumasa +2 more
Interplanetary (IP) shocks traveling between the Sun and the Earth's orbit were clearly detected in interplanetary scintillation (IPS) observations made at Toyokawa (Japan) and Pushchino (Russia), in association with two halo coronal mass ejections (CMEs) that occurred on 04 and 06 September 2017. Since the observation times at Toyokawa and Pushch…
Characteristics of the Solar Coronal Line Profiles from Fabry-Perot Interferometric Observations
Chandrasekhar, T.; Raju, K. P.; Prabhakar, Maya
This article reports the analysis of a set of Fabry-Perot interferograms that were studied to probe the physical parameters of the inner solar corona. The observations were carried out in the coronal green line, Fe XIV 5302.86 Å, during the total solar eclipse of 21 June 2001 that occurred in Lusaka, Zambia. The study was performed in the radial r…