Search Publications
Resolving the 180° Ambiguity in Solar Vector Magnetic Field Data: Evaluating the Effects of Noise, Spatial Resolution, and Method Assumptions
Liu, Y.; Jing, Ju; Leka, K. D. +4 more
The objective testing of algorithms for performing ambiguity resolution in vector magnetic field data is continued, with an examination of the effects of noise in the data. Through the use of analytic magnetic field models, two types of noise are "added" prior to resolving: noise to simulate Poisson photon noise in the observed polarization spectr…
Automated Coronal Hole Detection Using Local Intensity Thresholding Techniques
Gallagher, Peter T.; Krista, Larisza D.
We identify coronal holes using a histogram-based intensity thresholding technique and compare their properties to fast solar wind streams at three different points in the heliosphere. The thresholding technique was tested on EUV and X-ray images obtained using instruments onboard STEREO, SOHO and Hinode. The full-disk images were transformed into…
Statistical Assessment of Photospheric Magnetic Features in Imminent Solar Flare Predictions
Jing, Ju; Wang, Haimin; Yurchyshyn, Vasyl +3 more
In this study we use the ordinal logistic regression method to establish a prediction model, which estimates the probability for each solar active region to produce X-, M-, or C-class flares during the next 1-day time period. The three predictive parameters are (1) the total unsigned magnetic flux Tflux, which is a measure of an active …
The Rotating Sunspot in AR 10930
Chae, Jongchul; Min, Soonyoung
We study the pattern and behavior of a rotating sunspot in Active Region 10930. The rotational angular speed has been extracted from the apparent motions of the sunspot determined by applying a new optical technique - called non-linear affine velocity estimator (NAVE) - to high-resolution G-band images taken by the Solar Optical Telescope (SOT) on…
X-Ray Jet Dynamics in a Polar Coronal Hole Region
Golub, Leon; Filippov, Boris; Koutchmy, Serge
New X-ray observations of the north polar region taken from the X-ray Telescope (XRT) of the Hinode spacecraft are used to analyze several time sequences showing small loop brightenings with a long ray above. We focus on the formation of the jet and discuss scenarios to explain the main features of the events: the relationship with the expected su…
Parameters of the Magnetic Flux inside Coronal Holes
Yurchyshyn, Vasyl; Abramenko, Valentyna; Watanabe, Hiroko
The parameters of the magnetic flux distribution inside low-latitude coronal holes (CHs) were analyzed. A statistical study of 44 CHs based on Solar and Heliospheric Observatory (SOHO)/MDI full disk magnetograms and SOHO/EIT 284 Å images showed that the density of the net magnetic flux, Bnet, does not correlate with the associated solar…
Analysis of Reconstruction Methods for Nonlinear Force-Free Fields
Myshyakov, I. I.; Rudenko, G. V.
We focus on quantitative evaluation of several methods for the reconstruction of force-free magnetic fields in the solar corona. We have studied two topics. The first is to carry out a comparison test of two approaches to implement the optimization method: (1) using a boundary layer with a weighting function and (2) involving an optimization algor…
Formation, Interaction and Merger of an Active Region and a Quiescent Filament Prior to Their Eruption on 19 May 2007
van Driel-Gesztelyi, L.; Bone, L. A.; Culhane, J. L. +2 more
We report observations of the formation of two filaments - one active and one quiescent, and their subsequent interactions prior to eruption. The active region filament appeared on 17 May 2007, followed by the quiescent filament about 24 hours later. In the 26 hour interval preceding the eruption, which occurred at around 12:50 UT on 19 May 2007, …
Modeling a Shallow Solar Dynamo
Schatten, Kenneth H.
Photospheric ephemeral regions (EPRs) cover the Sun like a magnetic carpet. From this, we update the Babcock - Leighton solar dynamo. Rather than sunspot fields appearing in the photosphere de novo from eruptions originating in the deep interior, we consider that sunspots form directly in the photosphere by a rapid accumulation of like-sign field …
A Cross-Comparison of Cotemporal Magnetograms Obtained with MDI/SOHO and SP/ Hinode
Li, H.; Zhang, H. Q.; Zhang, M. +1 more
We compared a set of cotemporal magnetograms of active regions obtained with the Michelson Doppler Imager (MDI) aboard SOHO and the Spectro-Polarimeter (SP) of the Solar Optical Telescope (SOT) on board Hinode. The comparison shows that even with the recent calibration of level-1.8 data, the magnetic flux density derived from the MDI data is still…