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NASA NTRS1998

Development and Preliminary Results of CTAS on Airline Operational Control Center Operations

Continued growth and expansion of air traffic and increased air carrier economic pressures have mandated greater flexibility and collaboration in air traffic management. The ability of airspace users to select their own routes, so called "free-flight", and to more actively manage their fleet operations for maximum economic advantage are receiving great attention. A first step toward greater airspace user and service provider collaboration is information sharing. In this work, arrival scheduling and airspace management data generated by the NASA/FAA Center/TRACON Automation System (CTAS) and used by the FAA service provider is shared with an airline with extensive operations within the CTAS operational domain. The design and development of a specialized airline CTAS "repeater" system is described, as well as some preliminary results of the impact and benefits of this information on the air carrier's operations. FAA controller per aircraft scheduling information, such as that provided by CTAS, has never before been shared in real-time with an airline. Expected airline benefits include improved fleet planning and arrival gate management, more informed "hold-go" decisions, and avoidance of costly aircraft diversions to alternate airports when faced with uncertain airborne arrival delays.

Zelenka, Richard↗
NASA NTRS2002

Coronal Heating and the Increase of Coronal Luminosity with Magnetic Flux

We present the observed scaling of coronal luminosity with magnetic flux in a set of quiet regions. Comparison of this with the observed scaling found for active regions suggests an underlying difference between coronal heating in active regions and quiet regions. From SOHO/EIT coronal images and SOHO/MDI magnetograms of four similar large quiet regions, we measure L(sub corona) and Phi(sub total) in random subregions ranging in area from about four supergranules [(70,000 km)(exp 2)] to about 100 supergranules [(0.5 R(sub sun))(exp 2)], where L(sub corona) is the luminosity of the corona in a subregion and Phi(sub total) is the flux content of the magnetic network in the subregion. This sampling of our quiet regions yields a correlation plot of Log L(sub corona) vs Log Phi(sub total) appropriate for comparison with the corresponding plot for active regions. For our quiet regions, the mean values of L(sub corona) and Phi(sub total) both increase linearly with area (simply because each set of subregions of the same area has very nearly the same mean coronal luminosity per unit area and mean magnetic flux per unit area), and in each constant-area set the values of L(sub corona) and Phi(sub total) 'scatter' about their means for that area. This results in the linear least-squares fit to the Log ((L (sub corona)), vs Log ((Phi (sub total)) plot having a slope somewhat less than one. If active regions mimicked our quiet regions in that all large sets of same-area active regions had the same mean coronal luminosity per unit area and same mean magnetic flux per unit area, then the least-squares fit to their Log((L (sub corona)) vs Log((Phi (sub total)) plot would also have a slope of less than one. Instead, the slope for active regions is 1.2. Given the observed factor of three scatter about the least-squares linear fit, this slope is consistent with Phi(sub total) on average increasing linearly with area (A) as in quiet regions, but L(sub corona) on average increasing as the volume (A(exp 1.5)) of the active region instead of as the area. This possibility is reasonable if the heating in active regions is a burning down of previously-stored coronal magnetic energy rather than a steady dissipation of energy flux from below as expected in quiet regions.

Moore, R. L.↗
NASA NTRS2002

Forecasting Coronal Mass Ejections from Vector Magnetograms

Identification of active regions from which Earthward halo Coronal Mass Ejections (CMEs) are likely to originate is important both for understanding how CMEs are produced and for prediction of hazardous space weather. In previous work, from a set of 17 MSFC (Marshall Space Flight Center) vector magnetograms of 12 bipolar active regions situated within +/- 2 days of rotation from central meridian, we have evaluated four different measures of the global nonpotentiality of the magnetic field of each active region, and have found that the nonpotentiality of these active regions is strongly correlated with their CME productivity during the time interval of +/- 2 days centered on the day of the magnetogram: strongly nonpotential bipolar active regions are much more likely to produce a CME during this interval that are weakly nonpotential bipolar active regions. To further establish the use of active-region nonpotentiality for forecasting CMEs, we have expanded the sample to 19 additional bipolar active regions, with vector magnetograms taken with the upgraded MSFC vector magnetograph from September 2000 through June 2001 with support from our LWS grant (M. J. Hagyard, PI). The four global measures of nonpotentiality are the length of strong-shear, strong-field main neutral line, the net current, and two other measures of the overall twist in the magnetic field of the active-region bipole. We find: 1) The statistical significance of the correlation of the nonpotentiality of active regions with their CME productivity within +/- 2 days of the day of the magnetogram is greater than 99%. 2) 67% of the strongly nonpotential active regions produced CMEs within the +/- 2 day window, while only 17% of the weakly nonpotential ones did. 3) The statistical significance of the correlation of the nonpotentiality of active regions with their CME productivity during 0-2 days after the day of the magnetogram is about 97%. 4) 42% of the strongly nonpotential active regions produced CMEs within the 0-2 day window, while only 10% of the weakly nonpotential ones did. 5) The four different measures of an active region's nonpotentiality agree most of the time in their classification of the nonpotentiality as strong or weak (75%-90% depending on the pair of measurements). Additional information is included in the original extended abstract.

Moore, R. L.↗
NASA NTRS2002

Initiation of Coronal Mass Ejections by Tether-Cutting Reconnection

We present and interpret examples of the eruptive motion and flare brightening observed in the onset of magnetic explosions that produce coronal mass ejections. The observations are photospheric magnetograms and sequences of coronal and/or chromospheric images. In our examples, the explosion is apparently driven by the ejective eruption of a sigmoidal sheared-field flux rope from the core of an initially closed bipole. This eruption is initiated (triggered and unleashed) by reconnection located either (1) internally, low in the sheared core field, or (2) externally, at a magnetic null above the closed bipole. The internal reconnection is commonly called 'tether-cutting" reconnection, and the external reconnection is commonly called "break-out' reconnection. We point out that break-out reconnection amounts to external tether cutting. In one example, the eruptive motion of the sheared core field starts several minutes prior to any detectable brightening in the coronal images. We suggest that in this case the eruption is triggered by internal tether-cutting reconnection that at first is too slow and/or too localized to produce detectable heating in the coronal images. This work is supported by NASA's Office of Space Science through its Solar & Heliospheric Physics Supporting Research & Technology program and its Sun-Earth Connection Guest Investigator program.

Moore, Ronald L.↗
NASA NTRS2003

CME Prediction from Line-of-Sight Magnetogram

We have previously shown for bipolar active regions that measures of active-region nonpotentiality from vector magnetograms are correlated with active-region CME productivity. We have now obtained a measure from line-of-sight magnetograms that is well correlated both with our measures of active-region nonpotentiality from vector magnetograms and with active-region CME productivity. The measure is the length of strong-gradient main neutral line (L(sub G)). This is the length of the bipolar region's main neutral line on which the potential transverse field is greater than 150G, and the gradient in the line-of-sight field is greater than 50G/Mm. From the sample of 17 MSFC magnetograms of 12 basically bipolar active regions used in our previous paper, we find that L(sub G) is strongly correlated with one of our vector-magnetogram measures of nonpotentiality, the length of strong-gradient main neutral line L(sub SS) (99.7%). We also find that L(sub G) is as strongly correlated with CME productivity (99.7%) as is L(sub SS). Being obtainable from line-of-sight magnetograms, L(sub G) makes the much larger data set of line-of-sight magnetograms (i.e. from SOHO/MDI and Kitt Peak) available for CME prediction study. This is especially important for evolutionary studies, with SOHO/MDI having no daylight, cloudy weather, or atmospheric seeing problems. This work was supported by funding from NSF's division of Atmospheric Sciences (Space Weather and Shine Programs) and by NASA's office of Space Science (Living with a Star program Solar and Heliospheric Physics Supporting Research and Technology program).

Falconer, D. A.↗
NASA NTRS2003

A Measure from Line-of-Sight Magnetograms for Prediction of Coronal Mass Ejections

From a sample of 17 vector magnetograms of 12 bipolar active regions, we have recently found (1) that a measure of the overall nonpotentiality (the overall twist and shear in the magnetic field) of an active region is given by the strong-shear length L(sub SS), the length of the portion of the main neutral line on which the observed transverse fields is strong (greater than 150 G) and strongly sheared (shear angle greater than 45 deg), and (2) that L(sub SS) is well correlated with the CME productivity of the active regions during the +/- 2-day time window centered on the day of the magnetogram. In the present paper, from the same sample of 17 vector magnetograms, we show that there is a viable proxy for L(sub SS) that can be measured from a line-of-sight magnetogram. This proxy is the strong-gradient length L(sub SG), the length of the portion of the main neutral line on which the potential transverse field is strong (greater than 150 G) and the gradient of the line-of-sight field is sufficiently steep (greater than or approximately 50 G/Mm). In our sample of active regions, L(sub SG) is statistically significantly correlated with L(sub SS) (correlation confidence level greater than 95%), and L(sub SG) is as strongly correlated with active-region CME productivity as is L(sub SS)(correlation confidence level approximately 99.7%). Because L(sub SG) can be measured from line-of-sight magnetograms obtained from conventional magnetographs, such as the magnetograph mode of the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO), it is a dependable substitute for L(sub SS) for use in operational CME forecasting. In addition, via measurement of L(sub SG), the years-long, nearly continuous sequence of 1.5-hour-cadence full-disk line-of-sight magnetograms from MDI can be used to track the growth and decay of the large-scale nonpotentiality in active regions and to examine the role of this evolution in active-region CME productivity.

Falconer, D. A.↗
NASA NTRS2003

Solar Coronal Heating and the Magnetic Flux Content of the Network

We investigate the heating of the quiet corona by measuring the increase of coronal luminosity with the amount of magnetic flux in the underlying network at solar minimum when there were no active regions on the face of the Sun. The coronal luminosity is measured from Fe IX/X-Fe XII pairs of coronal images from SOHO/EIT. The network magnetic flux content is measured from SOHO/MDI magnetograms. We find that the luminosity of the corona in our quiet regions increases roughly in proportion to the square root of the magnetic flux content of the network and roughly in proportion to the length of the perimeter of the network magnetic flux clumps. From (1) this result, (2) other observations of many fine-scale explosive events at the edges of network flux clumps, and (3) a demonstration that it is energetically feasible for the heating of the corona in quiet regions to be driven by explosions of granule-sized sheared-core magnetic bipoles embedded in the edges of network flux clumps, we infer that in quiet regions that are not influenced by active regions the corona is mainly heated by such magnetic activity in the edges of the network flux clumps. Our observational results together with our feasibility analysis allow us to predict that (1) at the edges of the network flux clumps there are many transient sheared-core bipoles of the size and lifetime of granules and having transverse field strengths greater than approximately - 100 G, (2) approximately 30 of these bipoles are present per supergranule, and (3) most spicules are produced by explosions of these bipoles.

Moore, R. L.↗
NASA NTRS2003

CME Prediction from Magnetograms

We have found that active regions that are likely to be CME productive can be identified from measures of their nonpotentiality from magnetograms. We have developed four different measures from vector magnetograms and another that can be obtained from a line-of-sight magnetogram. We find that all five measures are strongly correlated with CME productivity to a similar degree. Hence, all five are roughly equally good predictors of active-region CME productivity. Since the measures all have similar predictive ability, the measures that are easiest to reliably measure are the best for operational forecasting of CMEs. The two best measures are the length of strong-shear main neutral line L(sub SS) (the length of the main neutral line with the magnetic shear angle greater than 45deg and observed transverse field greater than 150G) and the length of strong-gradient main neutral line L(sub G) (the length of the main neutral line with line-of-sight magnetic field greater than 50G/Mm and potential transverse field greater than 150G). As L(sub G) is measured from line-of-sight magnetograms it opens the larger data base of SOHO/MDI and Kitt Peak line-of-sight magnetograms for CME prediction study. This is especially important for evolutionary studies, with SOHO/MDI having no daylight, cloudy weather, or atmospheric seeing problems.

Falconer, D. A.↗
NASA NTRS2003

Solar Coronal Heating and the Magnetic Flux Content of the Network

We investigate the heating of the quiet corona by measuring the increase of coronal luminosity with the amount of magnetic flux in the underlying network at solar minimum when there were no active regions on the face of the Sun. The coronal luminosity is measured from Fe IX/X-Fe XII pairs of coronal images from SOHO/EIT. The network magnetic flux content is measured from SOHO/MDI magnetograms. We find that the luminosity of the corona in our quiet regions increases roughly in proportion to the square root of the magnetic flux content of the network and roughly in proportion to the length of the perimeter of the network magnetic flux clumps. From (1) this result, (2) other observations of many fine-scale explosive events at the edges of network flux clumps, and (3) a demonstration that it is energetically feasible for the heating of the corona in quiet regions to be driven by explosions of granule-sized sheared-core magnetic bipoles embedded in the edges of network flux clumps, we infer that in quiet regions that are not influenced by active regions the corona is mainly heated by such magnetic activity in the edges of the network flux clumps. Our observational results together with our feasibility analysis allow us to predict that (1) at the edges of the network flux clumps there are many transient sheared-core bipoles of the size and lifetime of granules and having transverse field strengths > approx. 100 G, (2) approx. 30 of these bipoles are present per supergranule, and (3) most spicules are produced by explosions of these bipoles.

Falconer, D. A.↗
NASA NTRS2003

Testing Fractal Methods on Observed and Simulated Solar Magnetograms

The term "magnetic complexity" has not been sufficiently quantified. To accomplish this, we must understand the relationship between the observed magnetic field of solar active regions and fractal dimension measurements. Using data from the Marshall Space Flight Center's vector magnetograph ranging from December 1991 to July 2001, we compare the results of several methods of calculating a fractal dimension, e.g., Hurst coefficient, the Higuchi method, power spectrum, and 2-D Wavelet Packet Analysis. In addition, we apply these methods to synthetic data, beginning with representations of very simple dipole regions, ending with regions that are magnetically complex.

Adams, M.↗
NASA NTRS2004

Prediction of Active-Region CME Productivity from Magnetograms

We report results of an expanded evaluation of whole-active-region magnetic measures as predictors of active-region coronal mass ejection (CME) productivity. Previously, in a sample of 17 vector magnetograms of 12 bipolar active regions observed by the Marshall Space Flight Center (MSFC) vector magnetograph, from each magnetogram we extracted a measure of the size of the active region (the active region s total magnetic flux a) and four measures of the nonpotentiality of the active region: the strong-shear length L(sub SS), the strong-gradient length L(sub SG), the net vertical electric current I(sub N), and the net-current magnetic twist parameter alpha (sub IN). This sample size allowed us to show that each of the four nonpotentiality measures was statistically significantly correlated with active-region CME productivity in time windows of a few days centered on the day of the magnetogram. We have now added a fifth measure of active-region nonpotentiality (the best-constant-alpha magnetic twist parameter (alpha sub BC)), and have expanded the sample to 36 MSFC vector magnetograms of 31 bipolar active regions. This larger sample allows us to demonstrate statistically significant correlations of each of the five nonpotentiality measures with future CME productivity, in time windows of a few days starting from the day of the magnetogram. The two magnetic twist parameters (alpha (sub 1N) and alpha (sub BC)) are normalized measures of an active region s nonpotentially in that they do not depend directly on the size of the active region, while the other three nonpotentiality measures (L(sub SS), L(sub SG), and I(sub N)) are non-normalized measures in that they do depend directly on active-region size. We find (1) Each of the five nonpotentiality measures is statistically significantly correlated (correlation confidence level greater than 95%) with future CME productivity and has a CME prediction success rate of approximately 80%. (2) None of the nonpotentiality measures is a significantly better CME predictor than the others. (3) The active-region phi shows some correlation with CME productivity, but well below a statistically significant level (correlation confidence level less than approximately 80%; CME prediction success rate less than approximately 65%). (4) In addition to depending on magnetic twist, CME productivity appears to have some direct dependence on active-region size (rather than only an indirect dependence through a correlation of magnetic twist with active-region size), but it will take a still larger sample of active regions (50 or more) to certify this. (5) Of the five nonpotentiality measures, L(sub SG) appears to be the best for operational CME forecasting because it is as good or better a CME predictor than the others and it alone does not require a vector magnetogram; L(sub SG) can be measured from a line-of-sight magnetogram such as from the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO).

Falconer, D. A.↗
NASA NTRS2003

A Measure from Line-of-Sight Magnetograms for Prediction of Coronal Mass Ejections

From a sample of 17 vector magnetograms of 12 bipolar active regions we have recently found (1) that a measure of the overall nonpotentiality (the overall twist and shear in the magnetic field) of an active region is given by the strong shear length Lss, the length of the portion of the main neutral line on which the observed transverse fields is strong (greater than 150 Guass (G)) and strongly sheared (shear angle greater than 45 degrees), and (2) that L(sub ss) is well correlated with the coronal mass ejection (CME) productivity of the active regions during the plus or minus 2-day time window centered on the day of the magnetogram. In the present paper, from the same sample of 17 vector magnetograms, we show that there is a viable proxy for L(sub ss) that can be measured from a line-of-sight magnetogram. This proxy is the strong gradient length L(sub SG), the length of the portion of the main neutral line on which the potential transverse field is strong (greater than 150 G), and the gradient of the line-of-sight field is sufficiently steep (greater than approximately 50 G/Mm). In our sample of active regions, L(sub SG) is statistically significantly correlated with Lss (correlation confidence level greater than 95%), and L(sub SG) is as strongly correlated with active region CME productivity as is L(sub SS) (correlation confidence level approximately 99.7%). Because L(sub SG) can be measured from line-of-sight magnetograms obtained from conventional magnetographs, such as the magnetograph mode of the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory, it is a dependable substitute for L(sub SS) for use in operational CME forecasting. In addition, via measurement of L(sub SG), the years-long, nearly continuous sequence of 1.5-hour cadence full disk line-of-sight magnetograms from MDI can be used to track the growth and decay of the large-scale nonpotentiality in active regions and to examine the role of this evolution in active region CME productivity.

Falconer, D. A.↗
NASA NTRS2004

Triggering of the Two X-class Flares of 28 and 29 October 2003

From H-alpha movies from Aryabhatta Research Institute of Observational Sciences and from Prairie View Solar Observatory, hard X-ray movies from RHESSI, line-of-sight magnetogram movies from SOHO/MDI, and vector magnetograms from Marshal Space Flight Center, we examine the magnetic structure and evolution of the large delta-sunspot active region NOAA 10486 in relation to the onset and development of the two X-class flares that occurred in this active region on 28 and 29 October 2003. We find evidence that each of these flares was triggered by strongly sheared magnetic field via "tether-cutting" reconnection with adjacent/overlying strongly sheared field. In the first flare, the initial brightening in H-alpha: (1) was partly rooted in emerging sheared magnetic field along the edge of the large positive-polarity flux domain of the delta sunspot, and (2) consisted of four flare kernels, two in negative magnetic flux and two in positive magnetic flux. In the second flare, the brightening started in the core of a Z-shaped sigmoidal sheared magnetic field and the inner two of four H-alpha kernels were visible in 30-50 Kev hard X-ray image from RHESSI. Each flare spread from the initial quadrupolar brightening to develop into a much larger two-ribbon flare straddling a much more extensive swath of strongly sheared field along the edge of the large positive-flux domain of the delta sunspot, the first flare on the leading side and the second flare on the trailing side of this domain. Thus, localized internal reconnection triggered the explosion of these extensive sheared magnetic fields.

Choudhary, Debi Prasad↗
NASA NTRS2004

Main-Sequence CMEs as Magnetic Explosions: Compatibility with Observed Kinematics

We examine the kinematics of 26 CMEs of the morphological main sequence of CMEs, those having the classic three-part bubble structure of (1) a bright front eveloping (2) a dark cavity within which rides (3) a bright blob/filamentary feature. Each CME is observed in Yohkoh/SXT images to originate from near the limb (> or equal to 0.7 R(sub Sun) from disk center). The basic data (from the SOHO LASCO CME Catalog) for the kinematics of each CME are the sequence of LASCO images of the CME, the time of each image, the measured radial distance of the front edge of the CME in each image, and the measured angular extent of the CME. About half of our CMEs (12) occur with a flare, and the rest (14) occur without a flare. While the average linear-fit speed of the flare CMEs (1000 km/s) is twice that of the non-flare CMEs (510 km/s), the flare CMEs and the non-flare CMEs are similar in that some have nearly flat velocity-height (radial extent) profiles (little acceleration), some have noticeably falling velocity profiles (noticeable deceleration), and the rest have velocity profiles that rise considerably through the outer corona (blatant acceleration). This suggests that in addition to sharing similar morphology, main-sequence CMEs all have basically the same driving mechanism. The observed radial progression of each of our 26 CMEs is fit by a simple model magnetic plasmoid that is in pressure balance with the radial magnetic field in the outer corona and that propels itself outward by magnetic expansion, doing no net work on its surroundings. On average over the 26 CMEs, this model fits the observations as well as the assumption of constant acceleration. This is compatible with main-sequence CMEs being magnetically driven, basically magnetic explosions, with the velocity profile in the outer corona being largely dictated by the initial Alfien speed in the CME (when the front is at approx. 3 (sub Sun), analogous to the mass of a main-sequence star dictating the luminosity.

Moore, Ron↗
NASA NTRS2005

Shape and Reconnection of the Exploding Magnetic Field in the Onset of CMEs

From chromospheric and coronal images and line-of-sight and vector magnetograms of magnetic regions that produce CMEs, and from chromospheric and coronal movies of the onsets of CME eruptions, it appears that the magnetic field that explodes to drive the CME is initially the strongly sheared core of a magnetic arcade encasing a polarity dividing line in the magnetic flux. Before or during the onset of the explosion, the sheared core field becomes a flux rope, often carrying chromospheric material within it. For the erupting flux rope to drive the explosion, that is, for its magnetic energy content to decrease in the explosion, the flux rope's cross-sectional area must increase faster than its length. For instance, for isotropic expansion, the area increases as the square of the length, and the magnetic energy content of the flux rope decreases as the inverse of the length. The instability that initiates the eruption of the flux rope might be an ideal MHD kink instability, or might involve runaway tether-cutting reconnection. The reconnection begins below the flux rope (internal to the arcade) when the overall field configuration of the region is effectively that of a single bipole. When the flux rope resides in a multi- bipolar configuration having a magnetic null above the flux rope, the runaway tether- cutting reconnection might begin either below the flux rope or at the null above (external to) the arcade. We present examples of observed CME onsets that illustrate the above alternatives. In each example, reconnection below the flux rope begins early in the eruption. This indicates that internal tether cutting reconnection (classic tether-cutting reconnection) is important in unleashing the CME explosion in all cases, including those in which the explosion may be triggered by MHD kinking or by external reconnection (classic breakout reconnection).

Moore, R. L.↗
NASA NTRS2006

Magnetic Causes of Solar Coronal Mass Ejections: Dominance of the Free Magnetic Energy over Either the Magnetic Twist or Size Alone

We report further results from our ongoing assessment of magnetogram-based measures of active-region nonpotentiality and size as predictors of coronal mass ejections (CMEs). We have devised improved generalized measures of active-region nonpotentiality that apply to active regions of any degree of magnetic complexity, rather than being limited to bipolar active regions as our initial measures were. From a set of approx.50 active-regions, we have found that measures of total nonpotentiality have a 75-80% success rate n predicting whether an active region will produce a CME in 2 days after the magnetogram. This makes measures of total nonpotentiality a better predictor than either active-region size, or active region twist (size-normalized nonpotentiality), which have a approx.65% success rates. We have also found that we can measure from the line-of-sight magnetograms an active region's total nonpotentiality and the size, which allows use to use MDI to evaluate these quantities for 4-5 consecutive days for each active region, and to investigate if there is some combination of size and total nonpotentiality that have a stronger predictive power than does total nonpotentiality. This work was funded by NASA through its LWS TR&T Program and its Solar and Heliospheric Physics SR&T Program, and by NSF through its Solar Terrestrial Research and SHINE programs.

Falconer, D. A.↗
NASA NTRS2006

Discovery of an Extreme MeV Blazar with the Swift Burst Alert Telescope

The Burst Alert Telescope (BAT) onboard Swift detected bright emission from 15-195 keV from the source SWIFT J0746.3+2548 (J0746 in the following), identified with the optically-faint (R approx. 19), z=2.979 quasar SDSS J074625.87+244901.2. Here we present Swift and multiwavelength observations of this source. The X-ray emission from J0746 is variable on timescales of hours to weeks in 0.5-8 keV and of a few months in 15-195 keV, but there is no accompanying spectral variability in the 0.5-8 keV band. There is a suggestion that the BAT spectrum, initially very hard (photon index Gamma approx. 0.7), steepened to Gamma approx. 1.3 in a few months, together with a decrease of the 15-195 keV flux by a factor approx. 2. The 0.5-8 keV continuum is well described by a power law with Gamma approx. 1.3, and spectral flattening below 1 keV. The latter can be described with a column density in excess of the Galactic value with intrinsic column density Nz(sub H) approx. 10(exp 22)/sq cm , or with a flatter power law, implying a sharp (Delta(Gamma) less than or approx. 1) break across 16 keV in the quasar's rest-frame. The Spectral Energy Distribution of J0746 is double-humped, with the first component peaking at IR wavelengths and the second component at MeV energies. These properties suggest that J0746 is a a blazar with high gamma-ray luminosity and low peak energy (MeV) stretching the blazar sequence to an extreme.

Sambruna, R. M.↗
NASA NTRS2006

Magnetic Causes of Solar Coronal Mass Ejections: Dominance of the Free Magnetic Energy Over the Magnetic Twist Alone

We examine the magnetic causes of coronal mass ejections (CMEs) by examining, along with the correlations of active-region magnetic measures with each other, the correlations of these measures with active-region CME productivity observed in time windows of a few days, either centered on or extending forward from the day of the magnetic measurement. The measures are from 36 vector magnetograms of bipolar active regions observed within -30" of disk center by the Marshal Space Flight Center (MSFC) vector magnetograph. From each magnetogram, we extract six whole-active-region measures twice, once from the original plane-of-the-sky magnetogram and again a h r deprojection of the magnetogram to disk center. Three of the measures are alternative measures of the total nonpotentiality of the active region, two are alternative measures of the overall twist in the active-region's magnetic field, and one is a measure of the magnetic size of the active region (the active region's magnetic flux content). From the deprojected magnetograms, we find evidence that (1) magnetic twist and magnetic size are separate but comparably strong causes of active-region CME Productivity, and (2) the total free magnetic energy in an active region's magnetic field is a stronger determinant of the active region's CME productivity than is the field's overall twist (or helicity) alone. From comparison of results from the non-deprojected magnetograms with corresponding results from the deprojected magnetograms, we find evidence that (for prediction of active-region CME productivity and for further studies of active-region magnetic size as a cause of CMEs), for active regions within approx.30deg of disk center, active-region total nonpotentiality and flux content can be adequately measured from line-of-sight magnetograms, such as from SOH0 MDI.

Falconer, D. A.↗