Search Publications
Coronal Radio Occultation Experiments with the Helios Solar Probes: Correlation/Spectral Analysis of Faraday Rotation Fluctuations
Pätzold, M.; Bird, M. K.; Efimov, A. I. +4 more
The coronal Faraday rotation (FR) experiments using the linearly polarized signals of the Helios-1 and Helios-2 interplanetary probes remain a unique investigation of the magnetic field of the solar corona and its aperiodic and quasi-periodic variations. The unexpectedly long lifetime of these spacecraft (1974 - 1986) enabled studies from very dee…
MLSO Mark III K-Coronameter Observations of the CME Rate from 1989 - 1996
St. Cyr, O. C.; Webb, D. F.; Stanger, A. L. +5 more
We report here an attempt to fill the 1990 - 1995 gap in the CME rate using the Mauna Loa Solar Observatory's Mark III (Mk3) K-coronameter. The Mk3 instrument observed routinely several hours most days beginning in 1980 until it was upgraded to Mk4 in 1999. We describe the statistical properties of the CMEs detected during 1989 - 1996, and we dete…
Time Evolution of Force-Free Parameter and Free Magnetic Energy in Active Region NOAA 10365
van Driel-Gesztelyi, L.; Romano, P.; Valori, G. +6 more
We describe the variation of the accumulated coronal helicity derived from the magnetic helicity flux through the photosphere in active region (AR) NOAA 10365, where several large flares and coronal mass ejections (CMEs) occurred. We used SOHO/MDI full-disk line-of-sight magnetograms to measure the helicity flux, and the integral of GOES X-ray flu…
Investigation of X-class Flare-Associated Coronal Mass Ejections with and without DH Type II Radio Bursts
Shanmugaraju, A.; Vršnak, Bojan; Lawrance, M. Bendict
A statistical analysis of 135 out of 141 X-class flares observed during 1997 - 2012 with and without deca-hectometric (DH) type II radio bursts has been performed. It was found that 79 events (X-class flares and coronal mass ejections - Group I) were associated with DH type II radio bursts and 62 X-class flare events were not. Out of these 62 even…
Forecast of a Daily Halo CME Occurrence Probability Depending on Class and Area Change of the Associated Sunspot
Moon, Yong-Jae; Lee, Jin-Yi; Lee, Kangjin
We investigate the halo (partial and full) coronal mass ejection (CME) occurrence probability depending on class and area change of the associated sunspot using front-side halo CMEs from 1996 to 2011. We select the most halo CME-productive 14 sunspot classifications: Cao, Cko, Dai, Dao, Dko, Dki, Dkc, Eao, Eai, Eko, Eki, Ekc, Fki, and Fkc. For eac…
Families of Granules, Flows, and Acoustic Events in the Solar Atmosphere from Hinode Observations
Roudier, T.; Rieutord, M.; Malherbe, J. -M. +1 more
We investigate the relationship between trees of fragmenting granules (TFG), horizontal and vertical flows, and acoustic events (AE) in the photospheric network. AE are spatially concentrated and short-duration locations of acoustic energy flux. We performed observations at disk center of a 2D field of view (FOV) with high spatial and temporal res…
Atmospheric Response of an Active Region to New Small Flux Emergence
Harra, L.; Green, L.; Shelton, D.
We investigate the atmospheric response to a small emerging flux region (EFR) that occurred in the positive polarity of Active Region 11236 on 23 - 24 June 2011. Data from the Solar Dynamics Observatory's Atmospheric Imaging Assembly (AIA), the Helioseismic and Magnetic Imager (HMI), and Hinode's EUV imaging spectrometer (EIS) are used to determin…
Persistent Near-Surface Flow Structures from Local Helioseismology
van Driel-Gesztelyi, L.; Harra, L.; Baker, D. +3 more
Near-surface flows measured by the ring-diagram technique of local helioseismology show structures that persist over multiple rotations. We examine these phenomena using data from the Global Oscillation Network Group (GONG) and the Helioseismic and Magnetic Imager (HMI) and show that a correlation analysis of the structures can be used to estimate…
Halo Coronal Mass Ejections and Their Relation to DH Type-II Radio Bursts
Shanmugaraju, A.; Bendict Lawrance, M.
A set of 88 halo CMEs observed by the Solar and Heliospheric Observatory/Large Angle Solar Coronagraph (SOHO/LASCO) during the period 2005 to 2010 is considered to study the relationship of these halo CMEs with Type-II radio bursts in the deca-hectametric (DH) wavelength range observed by Wind/(Plasma and Radio Waves: WAVES). Among the 88 events, …
Reduced Coronal Emission Above Large Isolated Sunspots
Gary, D. E.; Shibasaki, K.; Peterova, N. G. +2 more
We analysed specific regions of reduced soft X-ray and microwave emission in five large isolated sunspots. The Nobeyama Radioheliograph 17 GHz observations reveal a local depression of microwave brightness in the peripheral area of the sunspots. The depression regions appear light (weak absorption) in the He 10830 Å line in areas with extended (op…