Search Publications
Unusual Cosmic Ray Variations During the Forbush Decreases of June 2015
Mavromichalaki, H.; Samara, E.; Lingri, D. +3 more
Although the current Solar Cycle 24 is characterized by low solar activity, an intense geomagnetic storm (G4) was recorded in June 2015. It was a complex phenomenon that began on 22 June 2015 as the result of intense solar activity, accompanied by several flares and coronal mass ejections that interacted with the Earth's magnetic field. A Forbush …
Decameter Type IV Burst Associated with a Behind-the-limb CME Observed on 7 November 2013
Rucker, H. O.; Panchenko, M.; Konovalenko, A. A. +5 more
We report on the results of observations of a type IV burst made by the Ukrainian Radio interferometer of the Academy of Sciences (URAN-2) in the frequency range 22 - 33 MHz. The burst is associated with a coronal mass ejection (CME) initiated by a behind-the-limb active region (N05E151) and was also observed by the Nançay Decameter Array (NDA) ra…
Probing the Quiet Solar Atmosphere from the Photosphere to the Corona
Gontikakis, Costis; Tziotziou, Kostas; Kontogiannis, Ioannis +1 more
We investigate the morphology and temporal variability of a quiet-Sun network region in different solar layers. The emission in several extreme ultraviolet (EUV) spectral lines through both raster and slot time-series, recorded by the EUV Imaging Spectrometer (EIS) on board the Hinode spacecraft is studied along with Hα observations and high-resol…
Interferometric Observations of the Quiet Sun at 20 and 25 MHz in May 2014
Rucker, H. O.; Poedts, S.; Melnik, V. N. +3 more
We present the results of solar observations at 20 and 25 MHz with the Ukrainian T-shaped Radio telescope of the second modification (UTR-2) in the interferometric session from 27 May to 2 June 2014. In this case, the different baselines 225, 450, and 675 m between the sections of the east-west and north-south arms of UTR-2 were used. On 29 May 20…
Flare-related Recurring Active Region Jets: Evidence for Very Hot Plasma
Del Zanna, Giulio; Shimizu, Toshifumi; Mulay, Sargam M. +3 more
We present a study of two active region jets (AR jets) that are associated with two C-class X-ray flares. The recurrent, homologous jets originated from the northern periphery of a sunspot. We confirm flare-like temperatures at the footpoints of these jets using spectroscopic observations of Fe XXIII (263.76 Å) and Fe XXIV (255.11 Å) emission line…
Solar Models with Dynamic Screening and Early Mass Loss Tested by Helioseismic, Astrophysical, and Planetary Constraints
Guzik, Joyce A.; Wood, Suzannah R.; Mussack, Katie
The faint young Sun paradox remains an open question. Presented here is one possible solution to this apparent inconsistency, a more massive early Sun. Based on the conditions on early Earth and Mars, a luminosity constraint is set as a function of mass. We examine helioseismic constraints of these alternative mass-losing models. Additionally, we …
A Check on the Validity of Magnetic Field Reconstructions
Wheatland, M. S.; Gilchrist, S. A.; Mastrano, A.
We investigate a method to test whether a numerically computed model coronal magnetic field B departs from the divergence-free condition (also known as the solenoidality condition). The test requires a potential field B0 to be calculated, subject to Neumann boundary conditions, given by the normal components of the model field B at the …
Magnetic Lasso: A New Kinematic Solar Wind Propagation Method. Magnetic Lasso Propagation
Dósa, M.; Opitz, A.; Dálya, Z. +1 more
Solar wind propagation from the point of measurement to an arbitrary target in the heliosphere is an important input for heliospheric, planetary and cometary studies. In this paper a new kinematic propagation method, the magnetic lasso method is presented. Compared to the simple ballistic approach our method is based on reconstructing the ideal Pa…
Physical Properties of Umbral Dots Observed in Sunspots: A Hinode Observation
Mathew, Shibu K.; Yadav, Rahul
Umbral dots (UDs) are small-scale bright features observed in the umbral part of sunspots and pores. It is well established that they are manifestations of magnetoconvection phenomena inside umbrae. We study the physical properties of UDs in different sunspots and their dependence on decay rate and filling factor. We have selected high-resolution,…
Analysis of a Failed Eclipse Plasma Ejection Using EUV Observations
Koutchmy, S.; Tavabi, E.; Bazin, C.
The photometry of eclipse white-light (W-L) images showing a moving blob is interpreted for the first time together with observations from space with the PRoject for On Board Autonomy (PROBA-2) mission (ESA). An off-limb event seen with great details in W-L was analyzed with the SWAP imager (Sun Watcher using Active pixel system detector and image…