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Solar-Wind High-Speed Stream (HSS) Alfvén Wave Fluctuations at High Heliospheric Latitudes: Ulysses Observations During Two Solar-Cycle Minima
Hajra, Rajkumar; Echer, Ezequiel; Franco, Adriane Marques de Souza +2 more
We study Alfvén wave fluctuations in solar-wind high-speed streams (HSSs) at high heliolatitudes during the last two solar-cycle minima (SCM). Solar-wind plasma and interplanetary magnetic field (IMF) measured by Ulysses during four 50-day intervals in 1994, 1995, 2007, and 2008 were analyzed using wavelet and Fourier analyses, cross-correlation a…
Reconciling Observational Challenges to the Impulsive-Piston Shock-Excitation Scenario. I. Kinematic Challenges
Grechnev, V. V.; Kiselev, V. I.; Uralov, A. M.
Until now, there is no consensus on the origin of coronal shock waves. Questions also remain about the patterns that govern the propagation of the presumably related disturbances observed in the extreme ultraviolet (EUV waves). We present arguments in favor of the initial excitation of the waves by the impulsive acceleration of erupting structures…
Properties of EUV Imaging Spectrometer (EIS) Slot Observations
Ugarte-Urra, Ignacio; Young, Peter R.
The Extreme ultraviolet Imaging Spectrometer (EIS) on board the Hinode spacecraft has been operating since 2006, returning high-resolution data in the 170 - 212 and 246 - 292 Å wavelength regions. EIS has four slit options, with the narrow 1'' and 2'' slits used for spectroscopy and the wide 40'' and 266''
Polarimetric Studies of a Fast Coronal Mass Ejection
Bemporad, Alessandro; Mierla, Marilena; Inhester, Bernd +4 more
In this work we performed a polarimetric study of a fast and wide coronal mass ejection (CME) observed on 12 July 2012 by the COR1 and COR2 instruments onboard the Solar TErrestrial RElations Observatory (STEREO) mission. The CME source region was an X1.4 flare located at approximately S15W01 on the solar disk, as observed from the Earth's perspec…
Reconciling Observational Challenges to the Impulsive-Piston Shock-Excitation Scenario. II. Shock Waves Produced in CME-Less Events with a Null-Point Topology
Grechnev, V. V.; Kiselev, V. I.; Uralov, A. M. +1 more
Continuing Article I, we revisit challenging events previously identified by different authors, whose analysis led to conclusions about various mechanisms of the shock-wave excitation. Here, we reconsider four events that involved fan-spine coronal configurations with a null-point topology (NPT). The presence of Type-II radio bursts in all events …
Sympathetic Quiet and Active Region Filament Eruptions
Joshi, Reetika; Chandra, Ramesh; Koleva, Kostadinka +3 more
We present the observations of three sympathetic filament eruptions occurring on 19 July 2015, namely F1, F2, and F3. The events were observed in UV and EUV by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and by Global Oscillation Network Group telescope in Hα line. As filament F1
Kinematic Study of Radio-Loud CMEs Associated with Solar Flares and DH Type-II Radio Emissions During Solar Cycles 23 and 24
Pappa Kalaivani, P.; Prakash, O.; Shanmugaraju, A. +2 more
We have statistically analyzed 379 radio-loud (RL) CMEs and their associated flares during the period 1996 - 2019 covering both Solar Cycles (SC) 23 and 24. We classified them into two populations based on the observation period: i ) 235 events that belong to SC 23 (August 1996 - December 2008) and ii ) 144 events that belong to SC 24 (January 200…
Updates to the SUMER Spectral Atlas
Wilhelm, Klaus; Schühle, Udo; Curdt, Werner +3 more
We present a reworked version of the SUMER spectral atlas (Curdt et al., 2001). New identifications are given for more than 100 emission lines; entries were corrected or added to the list. The solar emission curve - spectral radiance versus wavelength - in the SUMER spectral range is now available in digital format as electronic supplementary mate…
Type IV Radio Bursts and Associated Active Regions in Sunspot Cycle 24
Kumari, Anshu
We study the association of solar Type IV radio bursts with the location of active regions on the Sun during Solar Cycle 24. The active regions associated with moving and stationary Type IV bursts are categorized as close to disk center and far from disk center, based on their location on the solar surface (i.e. ≤45∘ or ≥45∘,…
Comparing the Sun Watcher Using Active Pixel System Detector and Image Processing Instrument to the Atmosphere Imaging Assembly Instrument Through Measurements of Polar Coronal Holes
West, Matthew J.; Pesnell, W. Dean; Kirk, Michael S. F. +2 more
The PRoject for OnBoard Autonomy 2/Sun Watcher using Active pixel system detector and image Processing (PROBA2/SWAP) instrument images the full-disk extreme ultraviolet (EUV) Sun using a complementary metal-oxide semiconductor active-pixel sensor (CMOS-APS) detector with a filter centered on a 174 Å passband at a cadence of one to two minutes. In …