Search Publications
Signature of the turbulent component of the solar dynamo on active region scales and its association with flaring activity
Abramenko, Valentina I.
It is a challenging problem to obtain observational evidence of the turbulent component of solar dynamo operating in the convective zone because the dynamo action is hidden below the photosphere. Here we present results of a statistical study of flaring active regions (ARs) that produced strong solar flares of an X-ray class X1.0 and higher during…
Evolutionary stages and triggering process of a complex eruptive flare with circular and parallel ribbons
Joshi, Bhuwan; Joshi, Navin Chandra; Mitra, Prabir K.
We report multiwavelength study of a complex M-class solar eruptive flare that consists of three different sets of flare ribbons, viz. circular, parallel, and remote ribbons. Magnetic field modelling of source active region NOAA 12242 exhibits the presence of 3D null-point magnetic topology that encompasses an inner bipolar region. The event initi…
Forward modelling of Kepler-band variability due to faculae and spots
Solanki, Sami K.; Shapiro, Alexander I.; Krivova, Natalie +4 more
Variability observed in photometric light curves of late-type stars (on time-scales longer than a day) is a dominant noise source in exoplanet surveys and results predominantly from surface manifestations of stellar magnetic activity, namely faculae and spots. The implementation of faculae in light-curve models is an open problem, with scaling typ…
The impact of a stealth CME on the Martian topside ionosphere
Nampoothiri, Govind G.; Thampi, Smitha V.; Pant, Tarun K. +1 more
Solar cycle 24 is one of the weakest solar cycles recorded, but surprisingly the declining phase of it had a slow coronal mass ejection (CME) that evolved without any low coronal signature and is classified as a stealth CME that was responsible for an intense geomagnetic storm at Earth (Dst = -176 nT). The impact of this space weather event on the…
Solar wind temperature-velocity relationship over the last five solar cycles and Forbush decreases associated with different types of interplanetary disturbance
Melkumyan, A. A.; Belov, A. V.; Abunina, M. A. +4 more
The behaviour of the solar wind (SW) proton temperature and velocity and their relationship during Forbush decreases (FDs) associated with various types of solar source - coronal mass ejections (CMEs) and coronal holes (CHs) - have been studied. Analysis of cosmic ray variations, SW temperature, velocity, density, plasma beta, and magnetic field (…
On the partial eruption of a bifurcated solar filament structure
Liu, Jiajia; Uddin, Wahab; Chandra, Ramesh +4 more
The partial eruption of a filament channel with bifurcated substructures is investigated using data sets obtained from both ground-based and space-borne facilities. Small-scale flux reconnection/cancellation events in the region triggered the pile-up of ambient magnetic field, observed as bright extreme ultraviolet (EUV) loops in close proximity t…
On the origin of the Kreutz family of sungrazing comets
Lemos, Pablo; Fernández, Julio A.; Gallardo, Tabaré
We evaluate numerically three different models for the parent comet of the Kreutz family of sungrazers: (i) A Centaur on a highly inclined or retrograde orbit that diffuse to the inner planetary region where it became a sungrazer (Model 1). (ii) A parent comet injected from the Oort cloud straight into a near-parabolic, sungrazing orbit. Near peri…
Multipoint remote and in situ observations of interplanetary coronal mass ejection structures during 2011 and associated geomagnetic storms
Teriaca, Luca; Srivastava, Nandita; Mishra, Wageesh +1 more
We present multipoint remote and in situ observations of interplanetary coronal mass ejection (ICME) structures during the year 2011. The selected ICMEs arrived at Earth on 2011 March 11 and 2011 August 6, and led to geomagnetic storms. Around the launch of these CMEs from the Sun, the coronagraphs onboard STEREO-Aand-B and SOHO enabled the CMEs t…
Updated values of solar gravitational moments J2n using HMI helioseismic inference of internal rotation
Meftah, M.; Mecheri, R.
The solar gravitational moments J2n are important astronomical quantities whose precise determination is relevant for solar physics, gravitational theory and high precision astrometry, and celestial mechanics. Accordingly, we propose in the present work to calculate new values of J2n (for n = 1, 2, 3, 4, and 5) using recent t…
Registration and imaging polarimetry of the Fe 6374 Å red coronal line during the 2017 total solar eclipse
Li, S. Y.; Qu, Z. Q.; Liang, Y. +3 more
Strict registration is critical for imaging polarimetry; a highly accurate registration approach to the coronal image and imaging polarimetry of the Fe 6374 Å red coronal line have been researched in this paper. In order to improve the registration accuracy, this paper proposes the idea of image enhancement based on blind deconvolution combined wi…