Search Publications
Investigation on Radio-Quiet and Radio-Loud Fast CMEs and Their Associated Flares During Solar Cycles 23 and 24
Shanmugaraju, A.; Suresh, K.
We present the results of a detailed analysis on the differences between radio-loud (RL) and radio-quiet (RQ) fast coronal mass ejections (CMEs) (V≥900 km s−1) observed during the period 1996 - 2012. The analysis consists of three different steps in which we examined the properties of (i) RL and RQ CMEs, (ii) accelerating (class-A) and …
Investigation of the Geoeffectiveness of CMEs Associated with IP Type II Radio Bursts
Chen, Y.; Kong, X. L.; Wang, B. +1 more
We perform a statistical analysis of the geoeffectiveness of coronal mass ejections (CMEs) that are associated with interplanetary (IP) type II bursts in Solar Cycle 23 during the period 1997 - 2008. About 47 % (109 out of 232) of IP type II bursts are found to be associated with geomagnetic storms. Of these 47 %, 27 % are associated with moderate…
Active-Region Twist Derived from Magnetic Tongues and Linear Force-Free Extrapolations
Démoulin, Pascal; Mandrini, Cristina H.; López Fuentes, Marcelo +1 more
The main aim of this study is to compare the amount of twist present in emerging active regions (ARs) from photospheric and coronal data. We use linear force-free field models of the observed coronal structure of ARs to determine the global twist. The coronal twist is derived, on one hand, from the force-free parameter [α ] of the model and, on th…
Identifying and Tracking of Peripheral and Central Umbral Dots
Yang, Yunfei; Ji, Kaifan; Feng, Song +3 more
Umbral dots (UDs) are small isolated brightening observed in sunspot umbrae. They are usually classified into peripheral UDs (PUDs) and central UDs (CUDs) according to their positions inside an umbra. To accurately investigate the similarities and the distinctions between PUDs and CUDs and better understand their formation mechanisms, we propose a…
Dynamics of CMEs in the LASCO Field of View
Gopalswamy, N.; Bronarska, K.; Michalek, G. +1 more
A large set (16 000) of coronal mass ejections (CMEs) observed during 1996 - 2011 was selected to study their dynamics in the LASCO field of view (LFOV). These events were selected based on the criterion that at least three height-time measurements were available for each CME. The height-time measurements included in the SOHO/LASCO catalog were us…
Decameter U-burst Harmonic Pair from a High Loop
Rucker, H. O.; Panchenko, M.; Poedts, S. +6 more
The results of the first observations of solar sporadic radio emission within 10 - 70 MHz by the Giant Ukrainian Radio Telescope (GURT) are presented and discussed. Observations in such a wide range of frequencies considerably facilitate the registration of harmonic pairs. The solar U-burst harmonic pair observed on 8 August 2012 is analyzed. The …
Evolution and Flare Activity of δ -Sunspots in Cycle 23
Takizawa, K.; Kitai, R.
The emergence and magnetic evolution of solar active regions (ARs) of β γ δ -type, which are known to be highly flare-productive, were studied with SOHO/MDI data in Cycle 23. We selected 31 ARs that can be observed from their birth phase as unbiased samples for our study. From the analysis of the magnetic topology (twist and writhe), we obtained t…
RATAN-600 Observations of Small-Scale Structures with High Spectral Resolution
Alissandrakis, C. E.; Bogod, V. M.; Kaltman, T. I. +1 more
We present observations of quiet-Sun small-scale structures (SSS) in the microwave range with the Radio Astronomical Telescope of the Academy of Sciences 600 (RATAN-600) spectral-polarization facility in a wide range of frequencies. The SSS are regularly recorded in routine observations of the large reflector-type radio telescope and represent man…
Relationship Between the Magnetic Flux of Solar Eruptions and the Ap Index of Geomagnetic Storms
Grechnev, V. V.; Chertok, I. M.; Belov, A. V. +2 more
Solar coronal mass ejections (CMEs) are the main drivers of the most powerful non-recurrent geomagnetic storms. In the extreme-ultraviolet range, CMEs are accompanied by bright post-eruption arcades and dark dimmings. The analysis of events of Solar Cycle 23 (Chertok et al. in Solar Phys.282, 175, 2013) revealed that the summarized unsigned magnet…
Intersunspot Microwave Sources
Bakunina, I. A.; Melnikov, V. F.; Solov'ev, A. A. +1 more
We studied a number of solar active regions using two-dimensional spatially resolved microwave observations. Data from the Nobeyama Radioheliograph and the Siberian Solar Radio Telescope together with observations by the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO) have allowed us to identify long-lived inte…