Search Publications
On the Origin of Ortho-Gardenhose Heliospheric Flux
Lockwood, Mike; Owens, Mathew J.; Macneil, Allan
Parker-spiral theory predicts that the heliospheric magnetic field (HMF) will have components of opposite polarity radially toward the Sun and tangentially antiparallel to the solar rotation direction (i.e., in Geocentric Solar Ecliptic (GSE) coordinates, with BX/BY<0 ). This theory explains the average orientation of the …
Coronal Imaging with the Solar UltraViolet Imager
Seaton, Daniel B.; Tadikonda, Sivakumara K.; Krimchansky, Alexander +3 more
We investigate the coronal imaging capabilities of the Solar UltraViolet Imager (SUVI) on board the Geostationary Operational Environmental Satellite-R series spacecraft. Nominally Sun-pointed, SUVI provides solar images in six extreme ultraviolet (EUV) wavelengths. On-orbit data indicated that SUVI had sufficient dynamic range and sensitivity to …
Modeling of the Sunspot-Associated Microwave Emission Using a New Method of DEM Inversion
Patsourakos, S.; Alissandrakis, C. E.; Bogod, V. M. +2 more
We develope a method to compute the temperature and density structure along the line of sight by inversion of the differential emission measure (DEM), under the assumptions of stratification and hydrostatic equilibrium. We apply this method to the DEM obtained from the Atmospheric Imaging Assembly (AIA) observations and use the results, together w…
Kinematics and Energetics of the EUV Waves on 11 April 2013
Srivastava, A. K.; Chen, P. F.; Uddin, Wahab +3 more
In this study, we present the observations of extreme-ultraviolet (EUV) waves associated with an M6.5 flare on 2013 April 11. The event was observed by Solar Dynamics Observatory (SDO) in different EUV channels. The flare was also associated with a halo CME and type II radio bursts. We observed both fast and slow components of the EUV wave. The sp…
Properties of High-Energy Solar Particle Events Associated with Solar Radio Emissions
Valtonen, Eino; Pohjolainen, Silja; Ameri, Dheyaa
We have analysed 58 high-energy proton events and 36 temporally related near-relativistic electron events from the years 1997 - 2015 for which the velocity dispersion analysis of the first-arriving particles gave the apparent path lengths between 1 and 3 AU. We investigated the dependence of the characteristics of the proton events on the associat…
Twin CME Launched by a Blowout Jet Originated from the Eruption of a Quiet-Sun Mini-filament
Srivastava, A. K.; Dwivedi, B. N.; Rao, Y. K. +1 more
We study a quiet-Sun blowout jet which was observed on 2014 May 16 by the instruments on board the Solar Dynamics Observatory (SDO). We find the twin CME as jet-like and bubble-like CMEs simultaneously as observed by LASCO C2 on board the Solar and Heliospheric Observatory (SoHO), and the Solar Terrestrial Relation Observatory (STEREO_A and STEREO…
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…