Search Publications
Using Polar Coronal Hole Area Measurements to Determine the Solar Polar Magnetic Field Reversal in Solar Cycle 24
Karna, N.; Hess Webber, S. A.; Pesnell, W. D.
An analysis of solar polar coronal hole (PCH) areas since the launch of the Solar Dynamics Observatory (SDO) shows how the polar regions have evolved during Solar Cycle 24. We present PCH areas from mid-2010 through 2013 using data from the Atmospheric Imager Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) instruments onboard SDO. Our an…
The First Ground-Level Enhancement of Solar Cycle 24 on 17 May 2012 and Its Real-Time Detection
Mavromichalaki, H.; Papaioannou, A.; Souvatzoglou, G. +2 more
Ground-level enhancements (GLEs) are defined as sudden increases in the recorded intensity of cosmic-ray particles, usually by neutron monitors (NMs). In this work we present a time-shifting analysis (TSA) for the first arriving particles that were detected at Earth by NMs. We also present an automated real-time GLE alert that has been developed a…
Very Fast and Accurate Azimuth Disambiguation of Vector Magnetograms
Anfinogentov, S. A.; Rudenko, G. V.
We present a method for fast and accurate azimuth disambiguation of vector magnetogram data regardless of the location of the analyzed region on the solar disk. The direction of the transverse field is determined with the principle of minimum deviation of the field from the reference (potential) field. The new disambiguation (NDA) code is examined…
Survey and Merging of Sunspot Catalogs
Clette, Frédéric; Lefevre, Laure
In view of the construction of new sunspot-based activity indices and proxies, we conducted a comprehensive survey of all existing catalogs providing detailed parameters of photospheric features over long time intervals. Although there are a fair number of such catalogs, a global evaluation showed that they suffer from multiple limitations: finite…
Variations in Abundance Enhancements in Impulsive Solar Energetic-Particle Events and Related CMEs and Flares
Reames, Donald V.; Kahler, Stephen W.; Cliver, Edward W.
We study event-to-event variations in the abundance enhancements of the elements He through Pb for Fe-rich impulsive solar energetic-particle (SEP) events, and their relationship with properties of associated coronal mass ejections (CMEs) and solar flares. Using a least-squares procedure we fit the power-law enhancement of element abundances as a …
Tracking Solar Active Region Outflow Plasma from Its Source to the Near-Earth Environment
Mandrini, C. H.; van Driel-Gesztelyi, L.; Culhane, J. L. +6 more
Seeking to establish whether active-region upflow material contributes to the slow solar wind, we examine in detail the plasma upflows from Active Region (AR) 10978, which crossed the Sun's disc in the interval 8 to 16 December 2007 during Carrington rotation (CR) 2064. In previous work, using data from the Hinode/EUV Imaging Spectrometer, upflow …
Identification of Interplanetary Coronal Mass Ejections at Ulysses Using Multiple Solar Wind Signatures
Richardson, I. G.
Previous studies have discussed the identification of interplanetary coronal mass ejections (ICMEs) near the Earth based on various solar wind signatures. In particular, methods have been developed of identifying regions of anomalously low solar wind proton temperatures (Tp) and plasma compositional anomalies relative to the composition…
Far- and Extreme-UV Solar Spectral Irradiance and Radiance from Simplified Atmospheric Physical Models
Fontenla, J. M.; Landi, E.; Snow, M. +1 more
This article describes an update of the physical models that we use to reconstruct the FUV and EUV irradiance spectra and the radiance spectra of the features that at any given point in time may cover the solar disk depending on the state of solar activity. The present update introduces important modifications to the chromosphere-corona transition…
Gauribidanur Low-Frequency Solar Spectrograph
Ramesh, R.; Kathiravan, C.; Kishore, P. +2 more
A new radio spectrograph, dedicated to observe the Sun, has been recently commissioned by the Indian Institute of Astrophysics (IIA) at the Gauribidanur Radio Observatory, about 100 km North of Bangalore. The instrument, called the Gauribidanur Low-frequency Solar Spectrograph (GLOSS), operates in the frequency range≈40 - 440 MHz. Radio emission i…
CME Expansion as the Driver of Metric Type II Shock Emission as Revealed by Self-consistent Analysis of High-Cadence EUV Images and Radio Spectrograms
Hillaris, A.; Preka-Papadema, P.; Moussas, X. +6 more
On 13 June 2010, an eruptive event occurred near the solar limb. It included a small filament eruption and the onset of a relatively narrow coronal mass ejection (CME) surrounded by an extreme ultraviolet (EUV) wave front recorded by the Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA) at high cadence. The ejection was accompa…