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…
Relation Between Type II Bursts and CMEs Inferred from STEREO Observations
Kaiser, M. L.; Howard, R. A.; Gopalswamy, N. +6 more
The inner coronagraph (COR1) of the Solar Terrestrial Relations Observatory (STEREO) mission has made it possible to observe CMEs in the spatial domain overlapping with that of the metric type II radio bursts. The type II bursts were associated with generally weak flares (mostly B and C class soft X-ray flares), but the CMEs were quite energetic. …
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 …
Multispacecraft Observations of Magnetic Clouds and Their Solar Origins between 19 and 23 May 2007
Liu, Y.; Luhmann, J. G.; Russell, C. T. +11 more
We analyze a series of complex interplanetary events and their solar origins that occurred between 19 and 23 May 2007 using observations by the STEREO and Wind satellites. The analyses demonstrate the new opportunities offered by the STEREO multispacecraft configuration for diagnosing the structure of in situ events and relating them to their sola…
Short-Term Solar Flare Prediction Using a Sequential Supervised Learning Method
Huang, Xin; Yu, Daren; Wang, Huaning +1 more
Solar flares are powered by the energy stored in magnetic fields, so evolutionary information of the magnetic field is important for short-term prediction of solar flares. However, the existing solar flare prediction models only use the current information of the active region. A sequential supervised learning method is introduced to add the evolu…
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…
Automated detection of EUV Polar Coronal Holes during Solar Cycle 23
Hess Webber, S. A.; Pesnell, W. D.; Young, C. A. +1 more
A new method for automated detection of polar coronal holes is presented. This method, called perimeter tracing, uses a series of 171, 195, and 304 Å full disk images from the Extreme ultraviolet Imaging Telescope (EIT) on SOHO over solar cycle 23 to measure the perimeter of polar coronal holes as they appear on the limbs. Perimeter tracing minimi…
CME Projection Effects Studied with STEREO/COR and SOHO/LASCO
Temmer, M.; Veronig, A. M.; Preiss, S.
Based on a set of 11 CME events we study the impact of projection effects by tracking CME leading edge features in the plane of sky (traditional CME tracking) from combined STEREO-SECCHI and SOHO-LASCO observations up to 20R⊙. By using CME observations from two vantage points and applying triangulation techniques, the source region loca…
Evidence of Magnetic Helicity in Emerging Flux and Associated Flare
Aulanier, G.; Schmieder, B.; Malherbe, J. M. +1 more
The aim of this paper is to look at the magnetic helicity structure of an emerging active region and show that both emergence and flaring signatures are consistent with a same sign for magnetic helicity. We present a multiwavelength analysis of an M1.6 flare occurring in the NOAA active region 10365 on 27 May 2003, in which a large new bipole emer…