Coronal Mass Ejections I Posters
Presiding: P C Liewer, Jet Propulsion Laboratory, California Institute of Technology; A Vourlidas, Naval Research Lab
SP23A-01 1330h
Towards Real-Time Automated Prediction of Geo-Magnetic Storms Based on Observations of Source Regions of Halo CMEs
Halo Coronal Mass Ejections (CMEs), originating near disk center, are possible sources of large geomagnetic storms. Our goal is to predict geomagnetic activities automatically and in real time based on the observations of source regions of CMEs. We have achieved the following two steps: (1) We studied the magnetic structure of a number of famous active regions that produced large flares (X5 or larger), and found a close correlation between magnetic gradient and magnetic shear; and magnetic gradient could be even a better proxy to predict where a major flare might occur. Therefore, we can avoid complication of using vector magnetograms to derive magnetic shear. (2) We investigated the relationship between geoeffectiveness and the orientation of magnetic field in source active regions. Based on the flaring neutral lines detected by step (1), we extrapolated the magnetic structure in active region with three-dimensional (3D) numerical models. We started with the potential field model. We attempt to find relationship between the the orientation of magnetic field in the source region and the hourly averaged ACE measurements of the Bz component of the interplanetary magnetic fields, that is believed to be the indicator of geomagnetic storms.
SP23A-02 1330h
Automatic Detection of Prominence Eruption
In this paper, we present a method to automatically detect prominence eruption on the solar limb, based on analysis of full-disk Halpha images. As the part of the detection program, we extract the properties of prominences and their eruptions, such as location, height, and eruption speed. In the first step, we normalize the images to the same contrast and remove noises. In the second step, we detect the solar limb and isolate the limb and disk components. In the third step, we identify the prominence features. Finally, based on the extracted parameters of detected features, we characterize prominence eruption as a function of time. The method will be used to detect prominence eruptions in real time.
SP23A-03 1330h
Automatic Detection of Corona Mass Ejections Using Pattern Recognition Techniques
We present an automatic method to detect and categorize Corona Mass Ejections (CMEs) using the advanced pattern recognition technique. Our method is applied to LASCO (Large Angel Spectrometric Coronagraph) C2 and C3 images. CMEs are very complex features that are varied from time to time. The noises on the images also reduce the accuracy of the CME detections. Therefore, we propose different procedures for different structural CMEs that are described by Howard et al. (1985). There are three steps in our detection and characterization. (1)Preprocess: our program correlates C2 with C3 images, normalizes the images to the same contrast level and remove noises. Three original images are used to produce two difference images, and images are reformatted to angular images. (2) Characterization: automatic thresholding and morphology methods are used to segment and identify the principal objects from the images. CMEs are characterized according to their intensity, height, span, velocity and mass. (3) Classification: by detail study, twenty features are proposed to represent a CME. With these twenty features, the SVM classifiers are able to detect CMEs and categorize CMEs.
SP23A-04 1330h
Improving an Empirical Prediction of the Transit Time of Coronal Mass Ejections from the Sun to the Earth
At the 2004 AAS/SPD meeting, we presented initial results of an attempt to predict (or forecast) the arrival of Earth-directed coronal mass ejections at Earth. Our initial work, following closely on that of Gopalswamy et al. (2000, 2001), incorporated knowledge of the solar wind conditions at the time of the CME and of the source location. This resulted in an improvement in forecast accuracy over Gopalswamy et al. by 25% (2.6 hours). At the time of presenting these results, we discussed potential improvements to the prediction algorithm. First, we proposed to complete a more sophisticated incorporation of solar wind data. The initial study used the solar wind speed measured at ACE at the time of the launch of the CME as a proxy for the solar wind speed encountered by the CME as it travels towards Earth. In this poster, we improve on this by incorporating the Wang-Sheeley-Arge solar wind speed model to model the actual solar wind encountered by the CME through its entire transit from the Sun to the Earth. Second, the initial study used Sudden Impulse (SI) times as the measure for CME arrival at Earth. While this is a useful measure to use to provide a meaningful forecast, it makes comparison with other transit time predictions more difficult. Therefore, in addition to predicting the time until the SI begins, we also show how well we can predict when the associated shock arrives at L1.
SP23A-05 1330h
NOAA Satellites Provide a Keen View of the Martin Luther King Solar Storm of January 2005
Solar active region 0720 rotated onto the east limb on January 10th and put on a pyrotechnic display uncharacteristic for this phase of the solar cycle before disappearing beyond the west limb on January 23rd. On January 15th this region released the first of five X-class solar flares. The last of those flares, January 20th, was associated with an extraordinary ion storm whose effect reached Earth's surface. This paper highlights the record of this event made by NOAA's GOES satellites via their Space Environment Monitor (SEM) subsystems that measures X-ray, energetic particles, and the magnetic field vector at the satellite. Displays of those data are supplemented by neutron monitor data to illustrate their relationship to the January 20th Ground Level Event. GOES-12 is also equipped with the Solar X-ray Imager (SXI) that produces an image of the Sun in X-ray wavelengths once per minute. Movies created from those data perfectly illustrate the cause-and-effect relationship between intense solar activity and satellite disruptions. The flares on January 17th and 20th are closely followed by noise in the SXI telescope resulting from energetic ions penetrating SXI. Ions with sufficient velocity and atomic number can penetrate satellite components and deposit charge along their path. Sufficient charge deposition can introduce erroneous information into solid-state devices. A survey of satellites that experienced problems of this type during this event will also be presented.
http://sxi.ngdc.noaa.gov/sxi_greatest.html
SP23A-06 1330h
Very Large Array Observations of the Evolving Source Regions and Initial Onset of Coronal Mass Ejections and Eruptive EUV Events
Very Large Array (VLA) observations at decimetric and metric wavelengths are combined with data from the SOHO EIT, and LASCO to study the source regions of coronal mass ejections and eruptive EUV events. On one day, the passage of a CME and an associated EUV ejection event coincided with an increase in the 91 cm brightness temperature of an extended coronal loop located a significant distance away and with the displacement of the 91 cm source during the early stage of the CME.. We suggest that the energy deposited into the corona by the CME may have caused a local increase in the thermal or nonthermal electron density or in the electron temperature in the middle corona resulting in a transient increase in the brightness of the 91 cm loop. The loop-like CME appeared to have had one footpoint rooted on the disk near the west limb, and the other behind the limb where the radio emission was occulted by the disk. The observed projected motion of the 91 cm source, with a speed of v 28 km/sec, represents the initial sideways expansion speed of the CME loop. To our knowledge, this component of the CME motion has not been determined before in such a direct way on the disk.
SP23A-07 1330h
Magnetic Reconnection and Mass Acceleration in Solar Eruptions
We study the relationship between magnetic reconnection and mass acceleration in solar eruptive events of different magnetic configurations. The preliminary results of the case studies confirm the temporal correlation and magnitude scaling between reconnection rate and acceleration. We find that such observationally determined reconnection-acceleration relationship is independent of magnetic configurations of source regions, such as weak bipolar magnetic fields or multi-polar active regions, and regardless of whether CMEs are accompanied by filament eruption or not, or whether reconnection may take place above or below the flux rope. Other properties of coronal magnetic reconnection, including the reconnection height and the total magnetic flux transferred by reconnection, are also studied in these events in view of the role of magnetic reconnection in solar eruptions.
SP23A-08 1330h
CME Onset Due to Loss of Confinement of Twisted Magnetic Flux Ropes
We present MHD simulations in both 2D axisymmetric and 3D spherical geometries of the evolution of a twisted magnetic flux rope emerging into the low-β corona previously occupied by a potential arcade field. We describe both the initial quasi-static evolution whereby stable equilibrium structures can form with stored free magnetic energy, and the eventual loss of confinement or equilibrium of the twisted magnetic flux rope as sufficient twist is being transported into the corona, resulting in the onset of a CME. We investigate how the evolution and the loss of equilibrium for a 3D line-tied flux rope differ compared to the case of a 2D axisymmetric flux rope.
SP23A-09 1330h
CME Population Distributions: Science Facilitated by the VSO
The Virtual Solar Observatory (VSO) exists to simplify and unify access to Solar Physics data. It provides a single interface to a broad spectrum of data types and sources which previously would have required considerable effort to collect. Using this ability to combine data sources, we access the entire SOHO/LASCO CME catalog and compare it with GOES observations of X-ray flares. Because we consider these data in their entirety, we find several instances where the results of less extensive studies may show unintentional selection effects. As a subpopulation, we specifically consider LASCO-observed halo CMEs. In agreement with previous studies, we find halo CMEs are the bulk of the fastest events. This selection effect is consistent with randomly-distributed CMEs extending over wide angles (>120 degrees). We also examine the lack of slower halo CMEs; otherwise randomly-distributed events are rarely Earth-directed. While geometric and Thomson scattering issues make less-energetic halo CMEs hard to detect, this dearth of slow observations may represent an additional seeing threshold. The lack of low-energy detections may account for the disparity in LASCO.s prediction of Kp ≥ 6 vs. Kp ≥ 5 geomagnetic storms.
SP23A-10 1330h
Examination of Type II Origin with SOHO/LASCO Observations
We examine a possibility that the origin of metric-type II solar radio bursts are coronal mass ejections (CMEs). For this we consider 129 type IIs-flare events from February 1997 to October 2000, and examine their association with SOHO/LASCO CMEs according to their time closeness. Among 129 events, we select 27 limb type II-CME events whose solar surface locations are identified by comparing LASCO and EIT running difference images. In addition, we examine four CMEs observed by LASCO C1 or MLSO Mk4 coronagraph at the time of type II bursts. Under the assumption that the observed type IIs are all generated by CMEs, we determine the formation heights of the CME-associated type IIs using LASCO CME seeds and type II onset times. The criteria for shock formation is assumed that the CME speed is larger than the empirically determined Alfvén speed, and the shock formation height is located within the range taking into account the coronal density effect and the observed type II starting frequencies. From these studies, we have found: (1) the type II bursts associated with CMEs do not strongly depend on longitude but more than 80 % events of the limb events seems to have temporal and spatial association with CMEs; (2) while 61 % (19/31) CMEs (Class I) satisfy the criteria for coronal shock formation, 39% (12/31) CMEs (Class II) violate the criteria; (3) the onset time comparison shows that while the Class I CMEs occurred just before (or nearly simultaneously) the type II onset, the onset time differences (CME - type II) of the Class II CMEs are widely scattered; and (4) the speeds of the Class I CMEs have a much better correlation with coronal shock speeds estimated from type II data than those of the Class II CMEs. Our results show that all type II bursts can not be explained by only CMEs, but large fraction of type IIs have close association with CMEs.