Comparison of Yohkoh Soft X-Ray Images and MSFC Vector Magnetograms of Solar Active Regions

ar032.moore01
Posted:  03-Sep-92
Updated: 10-Nov-92, 04-Oct-93, 06-Apr-94, 27-Dec-94, 3-Sep-95, 7-May-96, 27-Jan-97
Events specified: N/A

COLLABORATORS: R. Moore and J. Porter/MSFC, S. Tsuneta/ISAS, P. Sturrock/Stanford U., and L. Acton/LPARL ABSTRACT: Active regions with different amounts of magnetic shear as seen in MSFC vector magnetograms will be studied in the Yohkoh soft X-ray images for the coronal magnetic structure and the occurrence of microflares and flares on and above the photospheric magnetic polarity inversion lines. Particular attention will be given to the preflare coronal structure at sites of strong photospheric magnetic shear that produce big flares, and to any change in this structure just pior to the onset of these flares. The goal is to find evidence for or against the hypothesis that a core of sheared field low along the inversion line erupts upward at or just before flare onset. We also want to see if the presence of strong magnetic shear in the photosphere noticeably enhances or suppresses the occurrence of micorflaring in the overlying corona. For the first step of the collaboration, Porter and Moore will visit Stanford University for a preliminary comparison of selected MSFC vector magnetograms with Yohkoh SXT images of the same active regions. This will help better define the project and prepare Porter and Moore for a follow-up visit to Japan for direct collaboration with Tsuneta and his colleagues at ISAS.

Update 27-Jan-97

Present Collaborators: R. Moore, J. Porter, D. Falconer, A. Gary/MSFC; T. Shimizu/U. Tokyo; K. Harvey, D. Rabin/NSO

Recent Work:

1. A paper was completed and submitted to ApJ. We recently submitted the second revision in response to the referee, and expect that this version will be accepted for publication.

Title: Neutral-Line Magnetic Shear and Enhanced Coronal Heating in Solar Active Regions

Authors: D. A. Falconer, R. L. Moore, J. G. Porter, G. A. Gary, T. Shimizu

Abstract:

By examining the magnetic structure at sites of nonflare persistent strong coronal heating in the bright coronal interiors of active regions, we establish some new characteristics of the magnetic origins of this heating. We have examined the magnetic structure of these sites in 5 active regions, each of which (1) was well observed by both the Yohkoh SXT and the Marshall Space Flight Center Vector Magnetograph, and (2) showed strong shear in its magnetic field along part of at least one neutral line (polarity inversion). Thus, we can assess whether this typical form of nonpotential field structure in active regions is a characteristic of enhanced coronal heating and vice versa. From 27 orbits of Yohkoh SXT images of the 5 active regions we have obtained a sample of 94 persistently bright coronal features (bright in all images from one orbit), 40 long (>~ 20,000 km) neutral-line segments having strong magnetic shear throughout (shear angle > 45 degrees), and 39 long neutral-line segments having weak magnetic shear throughout (shear angle < 45 degrees). From this sample, we find: (1) all of our persistently bright coronal features are rooted in magnetic fields that are stronger than 150 G; (2) nearly all (95%) of these enhanced coronal features are rooted near (closer than 10,000 km) neutral lines; (3) a great majority (80%) of the bright features are rooted near strong-shear portions of neutral lines; (4) a great majority (85%) of long strong-shear segments of neutral lines have persistently bright coronal features rooted near them; (5) a large minority (40%) of long weak-shear segments of neutral lines have persistently bright coronal features rooted near them; (6) the brightness of a persitently bright coronal feature often changes greatly over a few hours. From these results, we conclude that most persistent enhnaced heating of coronal loops in active regions (1) requires the presence of a polarity inversion in the magnetic field near at least one of the loop footpoints, (2) is greatly aided by the presence of strong shear in the core magnetic field along that neutral line, and (3) is controlled by some variable prosess that acts in this magnetic environment. We infer that this variable process is low-lying reconnection accompanying magnetic flux cancellation.

2. The Porter et al poster paper presented at the Madison AAS/SPD Meeting last June is being prepared for submission to ApJ. The central result of this paper is displayed on the 1996 Huntsville Solar Group Christmas Card.

Title: Microflaring in Sheared Core Magnetic Fields and Episodic Heating in Large Coronal Loops

Authors: J. G. Porter, D. A. Falconer, R. L. Moore, K. L. Harvey, D. M. Rabin, T. Shimizu

Abstract:

We have previously reported that large outstandingly bright coronal loops within an active region or stemming from an active region have one end rooted around a magnetic island of included polarity that is itself a site of locally enhanced coronal heating (X-ray bright point) [Porter et al 1996, in Magnetohydrodynamic Phenomena in the Solar Atmosphere - Prototypes of Stellar Magnetic Activity, ed. Y. Uchida, T. Kosugi, and H. S. Hudson (Kluwer: Dordrecht), p. 429]. This suggests that exceptional magnetic structure in and around the magnetic island fosters magnetic activity, such as microflaring, that results in the enhanced coronal heating in both the compact core field around the island and in the body of large loops that extend from this site. We have also reported that enhanced coronal heating in active regions goes hand-in-hand with strong shear in the core magnetic fields along polarity inversion lines [Falconer et al 1995, BAAS, 27(2), 976]. Here, by combining MSFC vector magnetograms with an NSO full-disk magnetogram and Yohkoh SXT coronal images, we examine the incidence of sheared core field, enhanced coronal heating, and microflaring in two active regions having several good examples of enhanced extended loops. It appears that the localized microflaring activity in sheared core fields is basically similar whether the core field is on the neutral line around an island of included polartiy or on the main neutral line of an entire bipolar active region. This suggests that the enhanced coronal heating in an extended loop stemming from near a polarity inversion line requires a special field configuration at its foot to plug it into the activity at the neutral line, rather than a different kind of activity in the core field on the neutral line. We also examine whether the waxing and waning of the coronal brightness of extended loops shows any correlation with the vigor or frequency of microflaring at the feet.

3. The Falconer et al oral paper presented at the Madison AAS/SPD Meeting last June is being prepared for submission to Solar Physics.

Title: 3D Magnetic Fields and Coronal Heating in Active Regions

Authors: D. A. Falconer, G. A. Gary, R. L. Moore, J. G. Porter

Abstract:

A major limitation in the analysis of solar coronal images is that only 2D information is observed. 3D coronal magnetic structures can be modeled by comparing coronal images and field extrapolations. If a good correspondence is found between the loops in the X-ray image and those derived from the extrapolation, then the extrapolated 3D coronal magnetic structure can be used, for example, for information about the height of the X-ray features. We show that even the simplest 3D field extrapolation, the potential extrapolation, can be useful for the analysis of observed X-ray loops.

For this analysis of 5 different active regions, we use magnetograms from MSFC and/or from Kitt Peak and use Sakurai's potential field extrapolation code to determine the 3D potential model of the coronal magnetic structure. The 3D model magnetic field is compared to images of persistent X-ray brightness derived from Yohkoh SXT coronal images. Only some of the X-ray loops in some active regions fit well with 3D coronal potential magnetic structures. Large differenced between the potential loops and observed loops that have one foot in the same place show that the observed loop traces nonpotential field. For many of the cases where there is no good fit, at least one footpoint of the observed loop is in a sizeable region of strong magnetic shear, so that potential coronal field is not expected.

Many of the extrapolated 3D magnetic field lines are far from any bright X-ray loop. That is, the active region is filled with magnetic loops, but only a fraction of these strongly emit X-rays. Since not all of the coronal structures experience strong heating, there is some factor that controls which structure do. We have also found from these same 5 active regions thaat the presence of a neutral line with strong magnetic shear is a favorable condition for strong heating. Large loops in the high coronal envelope of an active region are apparently selected for enhanced heating by the presence of such magnetic shear near a footpoint of the large loop, independently of whether the envelope field is itself strongly nonpotential.

4. We are developing a method for quantifying the degree to which strong coronal heating in active regions is restricted to the small fraction of the magnetic field that is rooted in strong neutral-line magnetic shear. Preliminary results are being presented at the winter AGU Meeting in San Francisco.

Title: Magnetic Field Conditions that Produce Strong Coronal Heating in Active Regions: Ranking by Magnetic Volume Ratio

Authors: D. A. Falconer, R. L. Moore, G. A. Gary, and J. G. Porter

Abstract:

We have been investigating the causes of persistent enhanced coronal heating in solar active regions by comparing Yohkoh X-ray images and Marshall Space Flight Center vector magnetograms. In a previous study, we showed that persistent enhanced coronal heating is more likely to occur in loops that have at least one footpoint within 12 arcsec of a neutral line. This probablity is increased if the magnetic field along the neutral line is strongly sheared. In all cases one footpoint was rooted in magnetic field stronger that 150 G. So, a relationship exists between the magnetic conditions at the feet of the loops and the heating in the loop. In another study, we showed that large-scale nonpotentiality of the loop is not a necessary condition for persistent enhanced coronal heating. Studies by Metcalf et al (1994, ApJ 428, 860) and by Fisher et al (1996, BAAS 188, 868) have also shown that large-scale currents and coronal brightness are not closely connected. Large-scale currents are also a signature of large-scale nonpotentiality.

In this study, we examine an active region on multiple days on which the active region is nearly potential on large scales, but has small areas of nonpotential magnetic field aroung an island of included polarity. We use the Sakurai potential code to extrapolate potential field lines in this active region. Using these field lines, we estimate the volume which is strongly heated. We then compare this volume to the volume occupied by the field lines rooted in three progressively more exclusive magnetic conditions: strong field (>150 G), strong field near a neutral line, and strong field near strong neutral-line magnetic shear. Each volume ratio [(strongly heated coronal magnetic volutme)/(coronal magnetic volume selected by the magnetic condition)] is a measure of the sufficiency of that magnetic condition for causing strong coronal heating. Our initial results indicate that the volume ratio is a few percent for coronal magnetic loops rooted in strong field or in strong field near a neutral line, but 70% or greater for loops rooted in strong field near strong neutral-line magnetic shear. This quantitively shows that only a very small fraction (a few percent) of the coronal loops rooted in strong field in active regions are subjected to strong coronal heating, and that most of these are rooted near neutral lines with strongly sheared magnetic fields.

Update 7-May-96

Present Collaborators: R. Moore, J. Porter, D. Falconer, A. Gary/MSFC; T. Shimizu/U. Tokyo; K. Harvey, D. Rabin/NSO

Recent Work:

1. The paper, for which preliminary results were reported at last year's AAS/SPD Meeting in Memphis and winter AGU Meeting in San Francisco, is nearly ready for submission to ApJ. Some final results from this paper will be presented at the AAS/SPD Meeting in Madison in June.

Title: Neutral-Line Magnetic Shear and Enhanced Coronal Heating in Solar Active Regions

Authors: D. A. Falconer, R. L. Moore, J. G. Porter, G. A. Gary, T. Shimizu

Abstract:

By examining the magnetic structure at sites of non-flare persistent strong coronal heating in the bright coronal interiors of active regions, we establish some new characteristics of the magnetic origins of this heating. We have examined the magnetic structure of these sites in 5 active regions, each of which (1) was well observed by both the Yohkoh SXT and the Marshall Space Flight Center Vector Magnetograph, and (2) showed strong shear in its magnetic field along part of at least one neutral line (polarity inversion). Thus, we can assess whether this typical form of nonpotential field structure in active regions is a characteristic of the enhanced coronal heating and vice versa. From 27 orbits of Yohkoh SXT images of the 5 active regions we have obtained a sample of 94 persistent bright coronal features (bright in all images from one orbit), 36 long (> 20,000 km) neutral-line segments having strong magnetic shear throughout (shear angle > 45 deg), and 38 long neutral-line segments having weak magnetic shear throughout (shear

angle < 45 deg).  From this sample, we find: (1) nearly all (95%) of the
persistent bright coronal features are rooted near (closer than 10,000 km)
to neutral lines; (2) a great majority (80%) of the bright persistent
coronal features are rooted near strong-shear portions of neutral lines; (3)

2. We are continuing to study the relation between microflaring in sheared core magnetic fields in active regions and brightness changes in extended coronal loops stemming from near these sites. A poster paper on this work will be presented at the Madison AAS/SPD Meeting in June.

Title: Microflaring in Sheared Core Magnetic Fields and Episodic Heating in Large Coronal Loops

Authors: J. G. Porter, D. A. Falconer, R. L. Moore, K. L. Harvey, D. M. Rabin, T. Shimizu

Abstract:

We have previously reported that large, outstandingly bright coronal loops within an active region or stemming from an active region have one end rooted around a magnetic island of included polarity that is itself a site of locally enhanced coronal heating (X-ray bright point) [Porter et al 1996, in Proceedings of the Yohkoh Solar/Stellar IAU Symposium, ed. Y. Uchida, T. Kosugi, H. S. Hudson (Kluwer: Dordrecht), in press]. This suggests that exceptional magnetic structure in and around the magnetic island fosters magnetic activity, such as microflaring, that results in the enhanced coronal heating in both the compact core field around the island and in the body of large loops that extend from this site. We have also reported that enhanced coronal heating in active regions goes hand-in-hand wilth strong shear in the core magnetic fields along polarity inversion lines (Falconer et al 1995, BAAS, 27(2), 976). Here, by combining MSFC vector magnetograms with an NSO full-disk magnetogram and Yohkoh SXT coronal images, we examine incidence of sheared core field, enhanced coronal heating, and microflaring in two active regions having several good examples of enhanced extended loops. It appears that the localized microflaring activity in sheared core fields is basically similar whether the core field is on the neutral line around an island of included polarity or on the main neutral line of an entire bipolar active region. This suggests that the enhanced coronal heating in an extended loop stemming from near a polarity inversion line requires a special field configuration at its foot to plug it into the activity at the neutral line, rather than a different kind of activity in the core field on the neutral line. We also examine whether the waxing and waning of the coronal brightness of extended loops shows any correlation with the vigor or frequency of microflaring at the feet.

3. We are also working on comparison of active-region coronal X-ray loops with potential magnetic field lines computed from the line-of-sight component of the MSFC vector magnetogram of the region. Preliminary results were reported in April at the Huntsville Workshop on 3D Solar Magnetic Fields and will be presented at the Madison AAS/SPD Meeting.

Title: 3D Magnetic Fields and Coronal Heating in Active Regions

Authors: D. A. Falconer, G. A. Gary, R. L. Moore, J. G. Porter.

Abstract:

A major limitation in the analysis of solar coronal X-ray images is that only 2D information is observed. 3D coronal magnetic structures can be modeled by comparing coronal images and field extapolations. If a good correspondence is found between loops in the X-ray image and those derived from the extrapolation, then the extrapotated 3D coronal magnetic structure can be used for information about the height of the X-ray features. We show that even the simplest 3D field exrapolation, the potential extrapolation, can be useful for the analysis of observed X-ray loops.

For this analysis of 5 different active regions, we use magnetograms from MSFC and/or from Kitt Peak and Sakurai's potential field extrapolation code to determine the 3D potential model of the coronal magnetic structure. The 3D model magnetic field is compared to images of persistent X-ray brightness derived from Yohkoh SXT coronal images. Only some of the X-ray loops in some active regions fit well with 3D coronal potential magnetic structures. Large differences between the potential loops and observed loops that have one foot in the same place show that the observed loop traces nonpotential field. For many of the cases where there is no good fit, at least one footpoint of the observed loop is in a sizeable region of strong magnetic shear, so that potential coronal field is not expected.

Many of the extrapolated 3D magnetic field lines are far from any bright X-ray loop. That is, the active region is filled with magnetic loops, but only a fraction of these strongly emit X-rays. Since not all of the coronal structures experience strong heating, there is some factor that controls which structures do. We have also found from these same 5 active regions that the presence of a neutral line with strong magnetic shear is a favorable condition for strong heating. Large loops in the high coronal envelope of an active region are apparently selected for enhanced heating by the presence of such magnetic shear near a footpoint of the large loop, independently of whether the envelope field is strongly nonpotential.

Update 3-Sep-95

Present Collaborators: R. Moore, J. Porter, D. Falconer, A. Gary/MSFC; T. Shimizu/U. Tokyo; K. Harvey, D. Rabin/NSO

Recent Work:

1. A paper was presented at the Yohkoh Solar/Stellar IAU Colloquium in Makuhari and at the AAS/SPD Meeting in Memphis, and is being prepared for publication in the Proceedings of the IAU Colloquium.

Title: Magnetic Roots of Enhanced High Coronal Loops

Authors: J. Porter, D. Falconer, R. Moore, K. Harvey, D. Rabin

Abstract:

We report results from an extension of a previous investigation of the magnetic roots of high-arching bright coronal loops (Porter et al 1994, in Proceedings of Kofu Symposium "New Look at the Sun," ed. S. Enome & T. Hirayama, NRO Report No. 360, p. 65). In the previous work, the magnetic locations and magnetic structure of the brightest coronal features in a selected active region were determined by registering Yohkoh SXT images with an MSFC vector magnetogram via registration of the sunspots. The active region (AR 6982 on 26 Dec 91) was selected for study because it had a large delta sunspot with a core of strong magnetic shear along the polarity inversion; it was expected that such extremely nonpotential magnetic fields would foster exceptionally strong coronal heating and hence be exceptionally bright in coronal images. It was found that the coronal heating in this active region indeed was markedly more intense in the low-lying sheared core field than in the bulk of the field that arched over the sheared core and spanned the whole bipolar region. In addition, the coronal images showed something that was not anticipated in the selection of this region: a section of the high-arching envelope field was much brighter than the rest, showing that it received much more coronal heating than the rest of the envelope field. These enhanced high coronal loops stemmed from around an embedded island of opposite-polarity flux that was the site of microflaring and enhanced coronal heating. It was therefore surmised that the high bright loops somehow received their enhanced coronal heating from this foot-point activity. In the present work, by registering a full-disk Kitt Peak magnetogram with full-disk Yohkoh SXT images from this same day (26 Dec 91), we have found many more examples of large enhanced coronal loops that had one foot point rooted in a site of mixed polarity within an active region. Several of these loops connected to distant quiet regions; others connected to remote parts of the same active region. Several of the mixed-polarity anchor points were sites of localized enhanced coronal heating as in the case of the previous study. Thus, we have found futher evidence that the coronal heating in enhanced large coronal loops is a consequence of microflaring and/or related activity in mixed-polarity fields at one end.

2. Another paper was presented at the AAS/SPD Meeting in Memphis, will be presented at the winter AGU Meeting in San Fancisco, and is being prepared for submission to ApJ.

Title: Neutral-Line Magnetic Shear and Enhanced Coronal Heating in Solar Active Regions

Authors: D. Falconer, R. Moore, J. Porter, A. Gary, T. Shimizu

Abstract:

By examining the magnetic structure at sites of strong persistent (non-flare) coronal heating, we establish some new characteristics of the magnetic orgins of coronal heating. Sites of strong coronal heating are seen as bright features in coronal images such as those from the Yohkoh SXT. As known since Skylab, the brightest persistent coronal features are located within the strong-field (>~ 100 gauss) domains of active regions. The Yohkoh SXT images show that the corona in active regions is highly nonuniform: the brightest features accupy only certain places within active regions. We have examined the magnetic structure of these places in 5 active regions, each of which (1) was well observed by both the Yohkoh SXT and the Marshall Space Flight Center vector magnetograph, and (2) showed (in the vector magnetograms) strong shear in its magnetic field along part of at least one neutral line (polarity inversion). This allows us to examine in particular whether this typical form of nonpotential field structure in active regions is a characteristic of the enhanced coronal heating and vice versa. From 27 orbits of Yohkoh SXT images of our 5 active regions we have obtained a sample of 93 bright persistent coronal features (bright in all images from one orbit), 32 long (>~ 20,000 km) neutral-line segments having strong magnetic shear throughout (shear angle > 45 deg), and 34 long neutral-line segments having weak magnetic shear throughout (shear angle< 45 deg). From this sample, we find:

(1) Nearly all (~ 95%) of the bright persistent coronal features are rooted near neutral lines.

(2) A great majority (~ 80%) of the bright persistent coronal features are rooted near strong-shear portions of neutral lines.

(3) A great majority (~ 80%) of strong-shear long segments of neutral lines are roots of bright persistent coronal features.

(4) A minority (<~ 40%) of weak-shear long segments of neutral lines are roots of bright persistent coronal features.

(5) The brightness of a bright persistent coronal feature often changes greatly over a few hours.

>From these results, we conclude that most persistent enhanced coronal heating in active regions (1) requires the local presence of a polarity inversion in the magnetic field, (2) is greatly aided by the presence of strong shear in the core magnetic field along the neutral line, and (3) is controlled by some variable process that acts in this magnetic environment.

Update 27-Dec-94

Moore and Porter continued work with Kathy Shearer (graduate student of Gordon Emslie at the University of Alabama in Huntsville) on their study of the relation between magnetic shear and coronal heating in active regions. A set of 8 active regions is being analyzed. These active regions were selected because they show a large range of magnetic shear and its evolution over several days. Our preliminary findings confirm our previous study of 2 active regions (reported by Moore et al in the Kofu Proceedings): sites of strong magnetic shear are sites of enhanced heating in the overlying low corona.

Moore and Porter are also extending their study of the connection of coronal heating with magnetic islands of included opposite polarity, an example of which was reported by Porter et al in the Kofu Proceedings. In the extended study, with help from Doug Rabin and Karen Harvey, the MSFC vector magnetograms are being supplemented by cotemporal full-disk Kitt Peak magnetograms. We plan to report results from this study at IAU Colloquium No. 153 in Japan next May.

Update 06-Apr-94

Recent work:

Jason Porter and Ron Moore completed and submitted the following two papers for the proceedings of the September 1993 meeting in Kofu:

1. Title: Microflaring at the Feet of Large Active Region Loops

Authors: J. Porter, R. Moore, G. Roumeliotis, T. Shimizu, S. Tsuneta, P. Sturrock, L. Acton

   Abstract: By superposing Yohkoh SXT images on an MSFC magnetogram of an
             active region, we find that the brightest loops in the bipolar
             magnetic envelope spanning the active region are rooted near a
             compact site of mixed polarity and microflaring.  Apparently, the
             enhanced coronal heating in these high loops is a consequence of
             the microflaring and/or related magnetic activity at this end
             site.

Authors: R. Moore, J. Porter, G. Roumeliotis, S. Tsuenta, T. Shimizu, P. Sturrock, L. Acton

   Abstract: From superposition of Yohkoh SXT images on MSFC vector
             magnetograms of two active regions, we find: (1) coronal heating
             is enhanced at sites of strong magnetic shear, and (2) this
             heating is produced by microflares.

Update 04-Oct-93

Project Title: Comparison of Yohkoh Soft X-Ray Images and MSFC Vector Magnetograms of Solar Active Regions

Collaborators: R. Moore and Jason Porter/MSFC, S. Tsuneta and T. Shimizu/ ISAS, P. Sturrock and G. Roumeliotis/Stanford U., and L. Acton/Montana State U.

Recent work:

Jason Porter and Ron Moore visited Peter Sturrock's group at Stanford and Saku Tsuenta at Lockheed in Palo Alto in July the week after the SPD Meeting. Porter and Moore worked with George Roumeliotis in selecting and analyzing Yohkoh SXT images for their Kofu papers. Porter and Moore visited ISAS and attended the Kofu Meeting in Japan the first three weeks of September. They presented the following two papers at the Kofu Meeting:

1. Title: Observations of Enhanced Coronal Heating in Sheared Magnetic Fields

Authors: R. Moore, J. Porter, G. Roumeliotis, S. Tsuneta, P. Sturrock, L. Acton

2. Title: Observations of Coronal Heat Injection from Low-Lying Microflares

Authors: J. Porter, R. Moore, G. Roumeliotis, T. Shimizu, S. Tsuneta, P. Sturrock, L. Acton

Porter, Shimizu, and Moore had extensive discussions at ISAS; they selected several additional active regions for joint study of microflaring in connection with coronal heating.

Update 10-Nov-92

Jason Porter and Ron Moore visited Peter Sturrock's group at Stanford the last week of September. Working with George Roumeliotis, and with additional hospitality from Jim Klimchuk and Peter Sturrock, they were able to make preliminary comparisons of MSFC vector magnetograms with sequences of Yohkoh SXT images for several active regions. These first looks were very encouraging. It appears that sites of strong magnetic shear in the photosphere are also often marked by obvious shear and frequent microflaring in the overlying magnetic loops in the low corona. However, these sites can also have quiet intervals of hours to days during which the SXT images show neither obvious shear nor obvious microflaring. We suspect that magnetic flux cancellation along the inversion line is the basic cause of the microflaring and enhanced X-ray brightness of the sheared field in the low corona. To follow up on these first impressions, we have transferred a few frames of Yohkoh photospheric and coronal images to MSFC so that we can do exact overlays of the X-ray images on the vector magnetograms by matching (on the work station screen) the sunspots on the Yohkoh photospheric images to the same sunspots on the photospheric brightness maps from the vector magnetograph. We are presently concentrating on AR 6982 on 26 December 1991. Porter and Moore hope to attend the Yohkoh Science Meeting next February and give two papers on results from this project.