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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…
Dynamics of Flare Processes and Variety of the Fine Structure of Solar Radio Emission over a Wide Frequency Range of 30 - 7000 MHz
Tan, Baolin; Tan, Chengming; Yan, Yihua +3 more
Radiobursts exhibiting fine structure observed over two years during the rising phase of Cycle 24 by the Chinese Solar Broadband Radio Spectrometer (SBRS/Huairou) in the range 1 - 7.6 GHz and the spectrograph IZMIRAN in the meter range (25 - 270 MHz) are analyzed. In five events the zebra structure, various fiber bursts, and fast pulsations were o…
Coronal Mass Ejections from the Same Active Region Cluster: Two Different Perspectives
Mandrini, C. H.; Schmieder, B.; Cremades, H. +1 more
The cluster formed by active regions (ARs) NOAA 11121 and 11123, approximately located on the solar central meridian on 11 November 2010, is of great scientific interest. This complex was the site of violent flux emergence and the source of a series of Earth-directed events on the same day. The onset of the events was nearly simultaneously observe…
The Relationship Between Solar Coronal X-Ray Brightness and Active Region Magnetic Fields: A Study Using High-Resolution Hinode Observations
Hazra, Soumitra; Nandy, Dibyendu; Ravindra, B.
By using high-resolution observations of nearly co-temporal and co-spatial Solar Optical Telescope spectropolarimeter and X-Ray Telescope coronal X-ray data onboard Hinode, we revisit the problematic relationship between global magnetic quantities and coronal X-ray brightness. Co-aligned vector magnetogram and X-ray data were used for this study. …
Detection of Solar Wind Disturbances: Mexican Array Radio Telescope IPS Observations at 140 MHz
Aguilar-Rodriguez, E.; Gonzalez-Esparza, J. A.; Romero-Hernandez, E. +2 more
The interplanetary scintillation (IPS) technique is a remote-sensing method for monitoring solar-wind perturbations. The Mexican Array Radio Telescope (MEXART) is a single-station instrument operating at 140 MHz, fully dedicated to performing solar-wind studies employing the IPS technique. We report MEXART solar-wind measurements (scintillation in…
An Interpretation of a Possible Mechanism for the First Ground-Level Enhancement of Solar Cycle 24
Gan, W. Q.; Rodríguez-Pacheco, J.; Li, Y. P. +1 more
It is well known that solar flares and shocks driven by coronal mass ejections (CMEs) are high-energy particle acceleration processes that might cause a high-energy particle event known as a ground-level enhancement (GLE). In this context, we have attempted to understand the processes responsible for the first GLE event (GLE71 17 May 2012 01:50 UT…
A Study of the Coronal Non-thermal Velocity in Polar Regions During the Rise from Solar Minimum to Solar Maximum in Cycle 24
van Driel-Gesztelyi, L.; Howe, R.; Harra, L. +3 more
We explore the changes in coronal non-thermal velocity (Vnt) measurements at the poles from solar minimum to solar maximum using Hinode EUV Imaging Spectrometer data. We find that although the intensity in the corona at the poles does tend to increase with the cycle, there are no significant changes in the Vnt values. The loc…
A Minimum Energy Fit Method to Reconstruct Photospheric Velocity and Magnetic Diffusivity in Active Regions from Observed Magnetograms and Dopplergrams
Tremblay, Benoit; Vincent, Alain
We introduce MEF-R, a generalization of the minimum energy fit (MEF; Longcope, Astrophys. J.612, 1181, 2004) to a non-ideal (resistive) gas. The new technique requires both vector magnetograms and Doppler velocities as input fields. However, in the case of active regions observed only with the Michelson-Doppler Imager (MDI) onboard the Solar and H…