Annual Report:  Understanding Magnetic Eruptions on the Sun and their Interplanetary Consequences:  August 1 2001 – June 30 2002[1]

 

PI:  George H. Fisher

AFOSR Grant F49620-01-1-0360

 

Overview

 

Notable accomplishments of our MURI award over the past year include these major developments:

 

This annual report is organized as follows:  We first provide a brief exposition of several of the major accomplishments identified above, followed by 4 detailed, chronological quarterly reports that were provided by all 9 University Teams over the course of the year.  Finally, at the end of the report, we provide a list of publications funded in part or in full by the Solar MURI project.

 

New Personnel

 

Efforts like the MURIs are important in that they provide a rare opportunity to get new talent into targeted fields, such as the solar origins of Space Weather.  The Solar MURI grant has resulted in these new hires:

 

Brian Welsch, a recent PhD graduate of the Physics Department at Montana State University, was hired as a new postdoc at UC Berkeley to work on scientific topics related to Solar MURI.  He is also collaborating closely with Spiro Antiochos, Rick Devore, and Mark Linton at the Naval Research Laboratory in Washington DC, and spends significant time each year at NRL.  Brian is pursuing a project aimed at understanding whether shearing and reconnection of a simple bipolar active region can lead to an erupting flux-rope configuration.  This project is an outgrowth of the “Numerical Experiments” MURI workshop that was held at UNH earlier this year (and described further below).

 

Andrew Phillips is a new postdoc at Drexel University working for Peter MacNeice. He began work in mid February, after finishing a PhD degree in the UK. He has been developing a Sedov test of the hydrodynamics of a High Order Godunov code using the Paramesh adaptive mesh refinement algorithm. 

 

Jimin Gao is a graduate student interested in computational physics that is working with MacNeice on the Solar MURI project.

 

Stephane Regnier is a new postdoc at Montana State University, working with Dick Canfield and Dana Longcope.  He received his PhD recently in France, and is now working with Canfield & Longcope on the reduction of vector magnetograms, the development of coronal force-free-field models based on the magnetogram data, and comparison of the theoretical models with solar coronal observations.  He is playing a key role in the use of observed data in NOAA region 8210 to drive MHD simulations of magnetic eruptions.

 

Yong-Jae Moon is a new postdoc at BBSO/NJIT.  He has expertise in the analysis of data from solar flares and CMEs, and the use of vector magnetograph data.  He has been an especially prolific contributor to MURI funded publications over the past year.

 

Improved Numerical Capabilities

 

Adaptive mesh refinement (AMR) is essential if one wishes to simultaneously resolve small scale structures on the Sun and large scale structures in the outer corona and the heliosphere.  Therefore one of the goals we set for ourselves at the beginning of the Solar MURI project was to use the expertise of Peter MacNeice, one of the originators of the Paramesh AMR and domain decomposition software, to help integrate Paramesh into our already existent numerical MHD codes, Zeus-3D (corona) and ENLIL (heliosphere).  This process was begun during a 1 week mini-workshop at GSFC during July of 2001, attended by Odstrcil, Abbett, Ledvina, & MacNeice, and was successfully completed this year.  In addition to the inclusion of Paramesh, Abbett & Ledvina incorporated other improvements into Zeus-3D, such as the elimination of operator splitting in the transport step (an improvement originally implemented by Yuhong Fan of HAO), which improved the code’s efficiency and accuracy.  Abbett & Ledvina have dubbed their new version of ZEUS  ``ZeusAMR”.

 

Abbett also worked to include a much more physically consistent coupling between our interior MHD code, ANMHD, which is used for simulations of the solar interior, and Zeus-3D and ZeusAMR.   An example of the computed evolution of the emergence of an active region, performed with ANMHD and Zeus-3D is shown in Figures 1.  The left hand side of Figure 1 shows how the 2 codes are coupled together in space, while the right hand side shows a comparison between the MHD solution and a potential field solution with increasing time for an emerging, twisted active region flux with different levels of twist within each tube.

Figure 1 – Bottom red box on left shows the volume encompassed by the ANMHD simulation of an emerging, twisted active region flux tube rising though the solar interior toward the solar surface.  The grey plane and the field lines above it show the Zeus-3D simulation of the response of the solar corona to the emerging flux.  The 6 images on the right hand side show comparisons between the MHD simulations of coronal evolution and a potential field extrapolation.  The left hand column shows the MHD results, and the right hand column the potential field extrapolation.  Each row shows a different amount of twist in the emerging active region flux tube, with the top row corresponding to no initial twist, and the bottom row to substantial twist.  These results are presented in a paper by Abbett & Fisher to be published in ApJ on January 1 2003.

 

Improvements to the ANMHD code were made as a collaboration between team member Abbett and Yuhong Fan of HAO, while they were both participants in the “Origins of Solar Magnetism” program at the Institute for Theoretical Physics at UCSB.  The ANMHD source code is publicly available on our Solar MURI website as the file Anmhd.tar.gz in the directory http://solarmuri.ssl.berkeley.edu/~abbett/public/software/ .

An illustration of a similar calculation performed with ZeusAMR, exhibiting the use of a block adaptive mesh, is shown in Figure 2.  Frame 001 Created with Tecplot 9.0-2-3

Figure 2 – Emerging flux simulation showing field lines (white) and vertical velocity contours in a single vertical plane (blue).  Mesh size is shown as the checkerboard patterns.  The adaptive mesh allows for a large dynamic range in size scales.

Simulations such as these can also be incorporated in a fairly straightforward way into simple source surface models of the large-scale corona.  Figure 3 shows how one of Abbett’s emerging active regions affects an initially dipolar magnetic field on the Sun and how the active region changes the location of the coronal hole boundaries.

Figure 3 – illustration of how an emerging active region simulation can be used to study its effects on an initially simple dipolar solar magnetic field.  Note the distortion of the northward coronal hole toward the active region.  A similar configuration resulted in the famous “elephant trunk” coronal hole in 1996 when a large active region formed at low latitudes near solar minimum.

 

During a 1 week visit by Dusan Odstrcil to Berkeley in August of 2002, Ledvina & Odstrcil settled on a code-coupling framework for connecting ZeusAMR simulations of the outer corona with ENLIL simulations of the heliosphere.  To facilitate this coupling, a spherical version of ZeusAMR is being developed and tested.

 

The MURI Workshops

 

It was clear early on that many of the problems that must be solved to achieve a solar and heliospheric numerical modeling system are too complex to be tackled by individual researchers working alone.  We therefore decided to organize a series of focused workshops to tackle what we regarded as the most pressing problems in modeling the solar origins of space weather.  At this point, we have held 4 of these workshops, and plan to hold 2 more:  UH team members are hosting a workshop in Honolulu Nov. 18-20 on the use of the new coronal IR / magnetic field measurements to be made on Haleakala, and how to make best use of this new data in our theoretical and numerical modeling efforts.  Jozsef Kota, Janet Luhmann, and Marty Lee are organizing one on SEP acceleration to be held at the University of Arizona March 17-18 of 2003.

 

The first of the workshops held this past year was on the Paramesh adaptive mesh and domain decomposition tool, which has now been successfully incorporated in both ZeusAMR and ENLIL.  It was the success of that workshop that led us to organize 3 more – one on the construction of synoptic magnetic maps, one on the use of vector magnetograms to drive numerical models of the corona, and a workshop on numerical experiments for CME initiation. 

 

Summary of Synoptic Magnetic Map Workshop (April 15, 2002)

 

This one-day workshop was held in Boulder, CO just before Space Weather Week.  The workshop was organized by team member Bernie Jackson, and was attended by scientists from both MURI teams, as well as participants from SEC/NOAA.

 

Synoptic maps of the photospheric field distribution remain the sole quantitative observational input for coronal and solar wind models and thus are key to the success of Sun-Earth modeling efforts.

 

 

Although digital synoptic maps of the photospheric field distribution are now routinely available from a number of solar observatories (e.g., Mount Wilson, Wilcox, and National (on Kitt Peak), the methods and processing used to construct them differ considerably, as do their archive file formats, spatial resolutions, and physical data units. This general lack of uniformity makes it very tedious and cumbersome for users to switch back and forth between synoptic maps generated by different facilities (data gaps being a prime example as to why such a switch might be necessary).

 

As more groups coordinate their research efforts by studying specific events and as more models are run in a (near) real-time mode, the ability to use uniformly assembled synoptic maps from multiple observatories is becoming increasingly critical. The solar and heliospheric communities would benefit from a reliable, centrally located public site providing synoptic maps (from multiple observatories) which have a uniform file format and which have been constructed using an established and documented assembly technique.

 

Over the last few years, through support from ONR, NSF, and NASA, a generalized synoptic map assembly code has been developed by Nick Arge at NOAA/SEC. This code can merge line-of-sight magnetograms from virtually any solar observatory into daily updated and full Carrington synoptic maps, as well as other types. It is versatile in that it provides greater control over how the maps are constructed and as to what corrections (unique to each observatory) need to be applied to the magnetic field data. It is thus ideally suited to provide the solar community with a standardized set of synoptic maps. In addition, the model is housed at a facility (NOAA/SEC) that is both reliable and readily accessible to the public. The ready availability of regularly updated, uniformly constructed synoptic maps from several observational sources will significantly facilitate the development of Sun-Earth propagation modeling capabilities.

 

Vector Magnetogram Workshop (April 29-May 1 2002)

 

The workshop was held at SSL/UC Berkeley, and was organized by Dick Canfield and George Fisher.  It was attended by MURI team members, and by other experts on vector magnetogram data (Tom Metcalf [LMSAL] and KD Leka [CoRA], as well as Zoran Mikic [SAIC]).  Here is the resulting “plan of action”:

 

Plan of Action:

 

 

Phase I

 

  1. Analyze available data for 1998 May 1 event

 

  1. Construct coronal magnetic equilibria

.

 

  1. Develop velocity inversion methods

 

  1. Test velocity inversion methods
  2. Study a second (simpler) event – May 12, 1997

Figure 4 – vertical magnetic field map of AR 8210 with all magnetic flux concentrations labeled (courtesy Dana Longcope).

Phase II.  Carry out MHD simulations

 

1.      Do Zeus AMR simulations using real magnetic field data near time of CME using synoptic magnetic field solutions as boundary condition. (Berkeley team members)

2.      Couple coronal and interplanetary codes (Abbett, Ledvina, Odstrcil)

 

Phase III.  Validation of modelling using available solar and IP data (team)

 

Numerical experiments to understand CME initiation:

(Workshop held May 14-16 at UNH in Durham)

 

This workshop was organized by Terry Forbes, and was attended by many members of both the Michigan and Berkeley MURI teams, as well as scientists from AFRL and NRL.

The objective of the workshop was to define the most urgent numerical MHD simulations needed to understand the physics of magnetic field eruption on the Sun (ie CME initiation).  What emerged were 3 different classes of investigation that the participants felt were necessary.  These are outlined below in a very skeletal form.

 

I.  The emerged bipole

 

 

There is clearly much more detail given for Phase I than for Phases II and III, but this is natural since Phase I must be carried out first in the near term.

 

The Numerical Experiments Workshop at UNH (May 14-16)

 

I.        The Emerged Bipole

o        3-d Emerged Bipole: Form a flux-rope in a simulated corona by converging footpoints of coronal fields (analogous to “flux cancellation” seen near neutral lines in filament channels)

o        the computational domain is 3-d non-periodic box with high b  = 10?) on bottom boundary, with stratification such that  b << 1 within lower part of simulation volume.

o        initial condition (IC) has volume-filling dipole field.

o        impose incompressible converging flows on bottom boundary (if initial configuration is slightly twisted) or converging flows with shear (if initial configuration is untwisted).

 

II.  The emerging, twisted bipole

 

II.       The Emerging Bipole

o       Flux rope in coronal volume is formed via the emergence of a pre-existing twisted flux tube from a region of high b to low b

o       Initial conditions: buoyantly unstable horizontal twisted flux tube immersed in high-b plasma at base of gravitationally stratified 3-d box.

o       Follow rise of twisted flux tube from deep in convection zone through photosphere into corona. Critical issue: initial position of tube cannot be too near surface, as flux tube curvature matters.

o       Unspecified parameter: degree of twist in emerging tube. Twist too high perhaps prevents mass drainage, hampering emergence; twist too low does not give true flux rope in corona.

o       Unspecified parameter: Magnetic field configuration in corona prior to flux rope emergence. Initial runs w/field-free corona envisioned.

o       As above, primary goal is to get flux rope in corona; subsequent efforts to attain eruption envisioned after attainment of primary.

o       As above, some modification of existing codes necessary.

 

III. Emergence Within a Multi-Polar Configuration

 

o         Multipolar Evolution

§         Emerge one flux tube into into a background magnetic field; the sheared arcade/flux rope formation is by reconnection between emerging flux and pre-existing flux.

§        Initial conditions: buoyantly unstable flux tube immersed in high-b plasma at base of gravitationally stratified 3-d box with background magnetic field configuration composed of a pre-emerged flux tube and large scale “restraining field”, and form sheared arcade/flux rope by reconnection between the two flux tubes.  The critical issue: without restraining field, reconnected flux expected to rise to top of computational volume in non-explosive manner.

§         Primary goal is attainment of sheared arcade/flux rope in corona; subsequent effort to attain eruption envisioned.

§         In one effort to attain eruption, additional polarity will be added to restraining field to make it quadrupolar.

§         Unspecified parameter: twist in either pre-emerged or newly-emerging flux ropes. Presence of twist might either enhance or diminish storage of energy in the field, and hence likelihood of eruption.

 

§         The full specification of all the necessary magnetic elements for this class of simulations is illustrated with the simple diagram below:

 

 

Figure 5 – an illustration of the full multi-polar configuration for the 3rd class of  numerical experiments.  Initially, only the interaction between the two central bipoles (one pre-existing, the other emerging) will be considered.  The magnetic neutral line between them is shown as the dashed curve.  An additional overlying,  constraining bipole field will then be considered; finally, a very large-scale bipole with the opposite polarity will be added.  The last bipole can be considered as a schematic representation of the overall solar dipole field.  This last level of complexity is necessary to create magnetic null points in the corona and hence achieve a “breakout” topology.

 

Deriving Self-Consistent Velocities from Sequential Vector Magnetograms

 

One of the major technical obstacles identified at the vector magnetogram workshop was determining the physically self-consistent vector velocity field at the surface where vector magnetic fields are measured.  Dana Longcope (MSU) has achieved a major breakthrough on this problem, and has created a mathematical framework to describe the problem and has proposed a solution, and written an “alpha” version of an IDL procedure to implement the solution.  The details of Dana’s formalism can be found on the Solar MURI website at http://solarmuri.ssl.berkeley.edu/~dana/public/presentations/  as SHINE02.ps .  Current versions of the IDL software can be found in the “team” part of the website as http://solarmuri.ssl.berkeley.edu/~dana/team/software/ .  Shown below is a comparison of the velocity field from a real MHD simulation of flux emergence, and that derived using Dana’s inversion technique.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 6 – Comparison between velocity field from an MHD simulation (left) and the reconstructed velocity field using Longcope’s inversion technique (right)

 

The Quarterly Reports:

 

Work Performed from August 1 2001 – September 30, 2001

 

OVERVIEW OF ACCOMPLISHMENTS FOR PAST 2 MONTHS

 

Major progress was made in numerical modeling capabilities over the past 2 months, with both the solar coronal (ZeusAMR) and heliospheric MHD codes (ENLIL) being upgraded to include adaptive mesh refinement.  These efforts are not complete, but the codes are running and are currently being debugged and tested.

 

Observational efforts continued at BBSO, UH, MSU, and UCB, with Yan Li and Dick Canfield continuing their efforts to construct a database of well-observed CMEs for in depth studies, and BBSO conducting a coordinated flare campaign.

 

Instrument construction, repair, and upgrades continue at BBSO and UH.

 

New papers were reported by Jing et al. (UH), Wang et al. (BBSO).

 

The Solar MURI website and data sharing server was set up and is now operational; the URL is http://solarmuri.ssl.berkeley.edu . All Solar MURI team members should have received email about how to use the data sharing aspects of the website, as well as how to log in and what the passwords are.  If a login account for new MURI team members is necessary, please contact George Fisher (fisher@ssl.berkeley.edu) or Bill Abbett (abbett@ssl.berkeley.edu).

 

Detailed descriptions of work accomplished at each institution now follow.  In the plain text, emailed version of this report, the Figures will be included as attachments (.jpg or .gif images), while the web-page version, which should appear within the next few days, will have the figures incorporated into the report itself.  You should find 3 Figures attached to this email message, in addition to the text itself.

 

UC Berkeley Report compiled by George H. Fisher

 

Steve Ledvina and Bill Abbett have worked on combining  the PARAMESH adaptive mesh algorithm with the ZEUS 3D MHD  code after attending our ``Paramesh'' mini-workshop with  MacNeice and Odstrcil at GSFC in July.  They have succeeded  in getting the combined new code (dubbed ``ZeusAMR'') to run, and are performing a series of test simulations.   This effort involved a significant re-write of the underlying

ZEUS code.  The ZeusAMR code will eventually be  used for both large and small scale coronal simulations. Abbett, Ledvina, Fisher, and MacNeice have submitted an AGU abstract describing this work for the Fall 2001.

 

Yan Li worked with Dick Canfield at Montana State University on the continuing construction of the MURI case studies data access website. She has also started to make the MDI magnetogram data sets to be linked to this table. These data are also available as movies made to show the time evolution of the active regions in the full-disk field context, see http://sprg.ssl.berkeley.edu/~yanli/mdicrmovs.html . An abstract has been submitted to the Fall AGU meeting on the work described in the previous monthly report, involving the response of global potential field models to Bill Abbett's modeled emergence of active region fields.

 

Janet Luhmann is examining the helmet streamer belt configuration at times of CMEs and the location of the involved active region with respect to the helmet streamer belt. This work relates to understanding both global coronal context of CMEs and CME initiation in future global MHD models. An abstract on this has also been submitted for the Fall AGU meeting.

 

George Fisher and Neil Griffiths have mostly completed the Solar MURI web site,  http://solarmuri.ssl.berkeley.edu , and have set up a new server to host the web page, as well as to serve as a centralized exchange for data and other information pertinent to the Solar MURI project.

 

BBSO/NJIT Contributions - Report received from Peter T. Gallagher

 

(1) Coordinated Flare Observations: During August, we coordinated a week-long campaign to search for impulsive chromospheric Doppler shifts associated with large  solar flares. Two simultaneously clocked 50 Hz CCD cameras were set up on two orthogonal benches of the 65-cm telescope at BBSO. Light from the telescope was directed to each bench by a 50:50 beamsplitter, and then to two H-alpha Lyot filters tunned to H-alpha line center +/- 0.3 A. In conjunction with these data, high-sensitivity vector magnetograms were simultaneously obtained using the Digital Vector Magnetograph (DVMG). We are currently in the process of reducing and analysing the data.

 

(2) Max Millennium Flare Catalogue: Software was completed to format the observing logs from the  Owen's Valley Solar Array (OVSA) and the BBSO lead Global  H-alpha Network for the Max Millennium Flare Catalog.

 

(3) Visible-Light Fabry-Perot: Control software is now being developed to synchronize the Queensgate ET-50 Fabry-Perot with an SMD 1M60 camera. The system will be moved to the dome for testing in October or November.

 

(4) Publications: Wang et al. published a paper entitled "Inter-Active Region  Connection of Sympathetic Flaring on 2000 February 17". The paper appeared in the 2001 October 1 issue of ApJ.

 

Drexel University - Report received from Peter MacNeice.

 

We continued development work on our existing CME  `breakout' model code, continued development work on a High Order Godonov version, and interviewed candidates for a post-doctoral position in support of this project.

 

Previously we implemented a number of fixes to handle a numerical cavitation problem which had appeared in high resolution runs of the ARC_FCT2.5D_AMR  code. These fixes seem to be a source of instability, which we have been attempting to characterize.

Mr. Jimin Gao has been working to generate a more general initial field configuration for the numerical model. Specifically, we have generated a multipole field which will enable us to test the breakout model in 2.5D by applying shear away from the equator.

 

Mr. Jimin Gao has designed a test problem for the high order Godonov code under development, using the Sedov-Taylor analytic solution for a large point explosion in 3D.

 

We conducted phone interviews with four candidates for a post-doctoral position that will support this project.

 

Montana State University - Report received from Dana W. Longcope.

 

To choose appropriate case studies for the observational part of our project, it is necessary to gather information -- which regions are well observed from the point of view of modeling?  For this purpose, Canfield worked with Yan Li (UCB) to add Robert Leamon's extensive list of eruptions from sigmoids to her Solar MURI event list. Although the two lists have not yet been integrated, Yan Li has now put Leamon's list on the web: http://sprg.ssl.berkeley.edu/~yanli/muri/sigmoid.table.html .

 

Canfield and MSU undergraduate Zachary Holder started a web page that documents the availability of Hawaii vector magnetograms for events in Yan Li's event list:  http://solar.physics.montana.edu/muri/vec/ .  Our next job is to identify vector magnetograms that are relevant to events in Leamon's list and add them to this web page.

 

Piet Martens submitted an abstract and prepared a paper for the Yohkoh 10 meeting, but its delivery has been postponed to January.  He has been reading up on recent Big Bear papers on onset and triggers of filament eruptions.

 

Dana Longcope began work with Stephan Regnier, who will begin Post Doctoral research under MURI funding in November.  The two set about comparing topologies found using full MHD extrapolation to those found using Magnetic Charge Topology models.  Active region 8151 was selected since Regnier had previously performed extrapolations of this region.  The comparisons will later be perfomed on regions selected from MURI event list.

 

The following paper, which was reported as ``in press'' at the last bi-monthly report, has now been published:

 

"Origin and Evolution of Filament-Prominence Systems", P.C.H. Martens and C. Zwaan 2001, Astrophys. J., 558, 872-887

 

Stanford Contributions - Report received from Yang Liu.

 

In the past two months from August 1 to September 30, we have tested our method to generate the Carrington synoptic maps using vector photospheric magnetic field in place of the light-of-sight photospheric magnetic field, and developed our extrapolation code so that this code can be used to calculate non-linear force free field in heliospheric coordinate system.

 

To generate vector magnetic field synoptic charts, we firstly calculate potential field from synoptic charts. So, we obtain potential field in the photosphere.

Secondly, we remap the photospheric vector magnetograms taken by the magnetographs. Generally such observations are available in active regions. Finally, we replace those remapped vector magnetograms to the potential field synoptic chart. We use Gaussian function to smooth the vector magnetic field synoptic chart in order to reduce the 'seam' effect (see attached figures).

 

Figure 7 - left panels -- the potential field synoptic chart; right panels -- the vector magnetic field synoptic chart.

The extrapolation code based on Boundary Element Method has been developed to be able to calculate non-linear force free field in the heliospheric coordinate system. Thus the global non-linear force free field can be reproduced from the vector magnetic field synoptic chart. We have calculated the potential field using this code, and will compare it with other methods.

Figure 8 - top panel-- the vector magnetic field synoptic chart; low panel-- the potential field synoptic chart

 

UCSD Contributions - Report received from Bernard V. Jackson

 

During these months of the MURI project Tamsen Dunn's work has allowed an accurate incorporation of magnetic field into our time-dependent tomographic model.  With the help of the UCSD MURI Co-Is and Todd Hoeksema and Xuepu Zhao, Tamsen has successfully incorporated the Zhao and Hoeksema (1995) magnetic field model into our solar wind analysis for eventual use in real-time magnetic field forecasting.   Tamsen has also included the conversion of coordinates at Earth from our model into GSM coordinates for comparison with ACE and other data sets. These data comparisons are now underway, and will be presented at the fall AGU (Dunn et al., 2001).  With the help of other students we have made these magnetic field data available for viewing in three-dimensions and will also present these visualizations at the AGU (Hick et al., 2001).

 

Further MURI work was also continued on the incorporation of a 3D MHD model into our computer code with the help of the group at  NOAA's Space Environment Center. A version of Tom Detman's 3D MHD code to compiles and runs here on our UCSD computers.  We have explored some aspects of the way to place this program into our time-dependent tomography.

 

References:

 

Dunn, T, B.V. Jackson, P.P. Hick and A. Buffington, 2001,  "Introduction of the CSSS magnetic field model into the UCSD tomographic solar wind model", to the fall 2001 AGU (submitted).

 

Hick, P.P., B.V. Jackson, A. Buffington and M.J. Bailey, 2001,  "Visualization of remotely-sensed heliospheric plasmas",  to the fall 2001 AGU (submitted).

 

Zhao, X, and Hoeksema, J.T., "Prediction of the interplanetary magnetic field strength", J. Geophys. Res, 100, 19, 1995.

 

Colorado/CIRES Report received from Dusan Odstrcil

 

We continued incorporation of the Paramesh package into the 3-D interplanetary solar wind code ENLIL. The hydrodynamic part of the code was successfully tested on various test problems. An example (interaction of shocks, origin of new contact discontinuity, and formation of a jet due to Rayleigh-Taylor instability) can be seen as an animated gif at this URL: http://solarmuri.ssl.berkeley.edu/~odstrcil/public/images/r468.gif  . We spent some time investigating various criteria and conditions for refinement and derefinement of the numerical grid. The magnetic part of the code has been modified as well and its verification is in progress; together with development of IDL procedures for visualization of the magnetic field on block-structured data.

 

Odstrcil was invited to present a talk on "Numerical Simulations of Interplanetary Disturbances" at the SOLSPA (Solar Cycle and Space Weather) conference in Vico Equense, Italy, September 24-29, 2001.

 

University of Hawaii - received from Jeff Kuhn.

 

We continue to support the on-line vector magnetic field measurements obtained from the IVM. An intermittent electronic steering-mirror servo gain problem was identified and tentatively solved. A replacement servo control module for the IVM mechanisms was identified and has been procured.  The filter wheel required for rapid line selection (between photospheric and chromospheric lines) has been fabricated.

 

The SOLARC instrument declination drive and clutch assembly were fabricated and installed in the telescope in order to improve its pointing stability.

 

The paper "Persistent Coronal Streamers and Identification of Sunspot Clusters" by Jing et al. has been accepted for publication in ApJ. This paper shows how large scale coronal streamers can be sustained by the global field contribution from long-lived sunspot clusters.

 

University of New Hampshire - received from Terry Forbes.

 

Terry Forbes has been working with Dave Webb on a comparison of CME observations from SMM and SOHO with predictions of a previously published model by Lin and Forbes (2000) for the growth of the current sheet which forms in the aftermath of a CME.  One of the key factors which affects how the position of the lower and upper tips of the current sheet evolve with time is the variation of the coronal density with height.  This variation affects the rate of reconnection in the sheet, and thus, the rate at which the current sheet is eroded by reconnection.

 

After comparison of the SMM observations with the published model it has become apparent that the exponential density model previously used is not adequate.  However, by replacing the exponential density model with a much more realistic one published by Sittler and Guhatahkurta (1999), we have now been able to obtain as reasonable agreement as can be expected for the Lin and Forbes model which is not really valid at large distances (> 3 Rsolar) away from the Sun.

 

Two aspects of this work which may be of interest to other team members are:  (1) the Sittler and Guhatahkurta model provides a fairly realistic density model of the inner corona while at the same time being relatively easy to implement in a theoretical analysis.  (2)  Although the Lin and Forbes model provides the essential ingredients to account for the onset and initial propagation of CMEs it is severely limited by being a planar, two-dimensional model.  In its present form in can only provide qualitative results, but it has the potential to serve as a guide to the behavior expected to occur in more realistic, three-dimensional models.

Figure 9 - This diagram shows the emergence from the Sun of a CME/flux-rope (blue shaded region) which drives a shock (thick red arc) into the ambient solar wind.  Ions (dots) are accelerated by the process of diffusive shock acceleration and excite hydromagnetic waves in front of the shock (denoted by wiggles in the spiral magnetic field).  The excited waves, which greatly enhance the rate of ion acceleration, are transmitted through the shock and trap accelerated ions downstream where they are cooled in the expanding solar wind.  At the outer extent of the excited-wave sheath some precursor ions escape the shock by magnetic focusing and propagate nearly scatter-free to Earth orbit (denoted by a schematic Earth with bow shock).  

 

References:

 

Lin, J., and T. G. Forbes, Effects of reconnection on the coronal mass

ejection process, J. Geophys. Res., 105, 2375-2392, (2000).

 

Sittler, E. C. J., and M. Guhathakurta, Semiempirical two-dimensional

magnetohydrodynamics model of the solar corona and interplanetary medium,

Astrophys. J., 523, 812-826, (1999).

 

Work Performed From October 1 2001 – December 31 2001

 

Progress toward our MURI goals is described in detail in the sections as  organized by sub-award institution.  During the next 10 weeks, George Fisher and Dana Longcope (member of the Solar MURI team) will be at the Institute for Theoretical Physics in Santa Barbara, participating as ``program coordinators'' for a special program on Solar Magnetic Fields.  Many other members of our team will also be participating in this program, and our next quarterly report will describe research done at the ITP that is supportive of our project.

 

UC Berkeley Report  (assembled by George Fisher)

 

Fisher organized the December 9 2001 MURI team meeting which was held at

the Space Sciences Lab.  The focus of that meeting was the organization of several "mini-workshops" over the coming year.  The minutes of the meeting will be posted on the "solarmuri" website separately.  Briefly, the mini-workshops will address these topics:  (1)  Well defined numerical  experiments exploring CME eruption mechanisms (hosted by Terry Forbes at UNH from May 14-16), (2) How to use vector magnetogram observing sequences to drive MHD codes (hosted by George Fisher at UCB around the 1st week of May), and (3) a workshop on contructing global magnetic maps of the Sun, to be held in Boulder on April 15.  Bernie Jackson is organizing this workshop.

 

Abbett and Ledvina demonstrated the new code ZeusAMR, a merge between PARAMESH and Zeus3D, at the Fall AGU by performing simulations of magnetic flux emergence into the low corona.  The 3D MHD code ANMHD was used to drive the photospheric boundary with the top of a rising, moderately twisted Omega loop, and ZeusAMR was able to refine the mesh where the bipole emerged through the photosphere and corona, allowing the simulation box to span a large portion of the low corona while simultaneously resolving the region of interest. 

 

Ledvina has continued work with the non-AMR version of ZEUS-3D in spherical coordinates.  The current challenges in that area are the proper description of the inner boundary conditions, and the need for implementation of the Boris correction scheme in order to reduce the time step size.

 

This spring, Ledvina will take the lead role in developing a spherical version of ZEUS-AMR that will be applied to the global corona.

 

Yan Li has made major progress working with Dick Canfield on the MURI case studies data collection and website. The event list is becoming quite large since different groups are studying different types of phenomena (e.g., the Montana focus on sigmoids, her own focus on CMEs). The progress on this can be seen at the website

http://sprg.ssl.berkeley.edu/~yanli/muri/events.html . Yan Li also presented a poster at the Fall AGU meeting showing the response of global potential field models, based on a large-scale photospheric dipole field, to Bill Abbett's model of emerging active region fields. The poster included a first attempt to model the same event in a time-dependent global MHD simulation, carried out by Jon Linker at SAIC, who collaborates with us through a related NSF Space Weather project. The work shows the evolution of coronal hole extensions in response to the active region emergence, similar to the "Whole Sun Month" study period scenario. The helmet streamer above the active region has the appearance of splitting when it is on the limb, as is sometimes observed in coronagraph images. No major transient loop eruption was produced in this preliminary study using the MHD model, but the emergence was slow enough to allow almost quasistatic adjustment of the corona, and there was no twist in the emerging active region fields or shear in the initial helmet streamer belt. Future work along these lines is planned to consider the impact of all of these factors.

 

Janet Luhmann presented a Fall AGU poster focused on examining the relative locations of helmet streamer belt and the involved active regions at times of CMEs. In the low solar activity cases examined, the involved active regions were often located in closed field regions outside of the main helmet streamer belt determined from potential field source surface models. Occasionally, the active regions lay beneath the helmet streamer belt. The interplanetary consequences for these scenarios seem to differ, with the former producing ICMEs in low speed wind at ACE and the latter producing ICMEs on the leading edge of high speed streams. However, tooo few cases have been examine thus far to conclude that this occurs as a rule. It also appears that the active region fields become engaged in the helmet streamer belt following eruptions in the cases where they are initially isolated. However, this interpretation is greatly limited by the use of potential field models to describe the active region fields. Work along these lines will continue in an effort to help define realistic CME simulation scenarios.

 

We have made an offer of a postdoctoral appointment to Brian Welsch, who is completing his PhD in Physics at Montana State University under Prof. Dana Longcope.  Welsch plans to join our group in February or March, and will work on projects in collaboration with MURI team members and with our solar colleagues at the Naval Research Laboratory.

 

BBSO Report (sent by Yong-Jae Moon)

        

(1) Visible-Light Fabry-Perot for Imaging Vector Magnetograph: After successful testing a Queensgate ET-50 Fabry-Perot in our laboratory, we are preparing for testing it on our 65 cm telescope. We expect camera control software to be ready soon.

 

(2) Global H-alpha Network: Now we are providing recent solar flare movies and daily full disk movies from global H-alpha network (http://www.bbso.njit.edu/ Research/Halpha/). Their observing logs and charts are also available.

 

(3) Field orientation in the interplanetary flux ropes and filaments: Using ACE measurements of the interplanetary magnetic fields, we define the orientation of magnetic flux ropes in magnetic clouds and compare them to the orientation of the solar magnetic fields and disappearing filaments.  We have found that the direction of the axial field in the flux ropes and their helicity are consistent with the direction of the axial field and helicity of the erupted filaments. Thus, the geoeffectiveness of a CME is defined by the orientation and structure of the erupted filament, and by its magnetic helicity, as well. We now use this technique to forecast geoeffectiveness of CMEs using full disk H-alpha images from the Global H-alpha Network, full disk SOHO/MDI and high resolution BBSO DMG magnetograms (Yurchyshyn al., ApJ, in press).

 

(4) Magnetic field changes associated with a X20 flare: Big Bear Solar Observatory observed the X20 flare that occurred at approximately 21:50 UT on 2001 April 2 with its standard complement of instruments. We have studied the evolution of high resolution and high cadence longitudinal magnetograph observations in the region of the flare. The data reveal that there was a significant increase in the magnetic field on the limbward side of the neutral line of the active region at the location of the flare, while the magnetic field on the side of the neutral line closer to the disk center remained constant (Spirock et al. submitted to ApJ).

 

(5) Relationship between magnetic helicity and flaring flux: Using a set of 6.5 hour 1 minute cadence MDI magnetograms of NOAA 8100, we have obtained the magnetic helicity transport rate via photospheric  footpoint shuffling motions. As a result, we have found a very close correlation between the integrated X-ray fluxes of homologous flares and the corresponding magnetic helicity accumulated during the flaring time  interval. We also note  an abrupt increase of photospheric shuffling  motion around the flaring time of M4.1 flare.  (Moon et al. in preparation)

 

(6) Statistical evidence of sympathetic flares We collected 48 sets of  sympathetic flare candidates, a pair of consecutive flares in which the second flare starts before the first one ends. To separate highly probable sympathetic flares from them, we estimated the ratio of actual flaring overlap time divided by random- coincidence time.  We have found a noticeable overabundance at short time intervals in the waiting time distribution of highly probable data, implying that sympathetic flares really exist.  It is also noted that transequatorial loops are more intimately associated with them than longitudinal loops are. (Moon et al. in preparation)

 

(7) Publications:

 

Yurchyshyn al.'s paper  entitled with "Orientation of magnetic field in the interplanetary flux ropes and solar filaments" is accepted for the publication in the ApJ.

 

Moon et al's paper  entitled with "Force-freeness of  solar magnetic fields in the photosphere" is accepted for the publication in the ApJ.

 

Moon et al's paper  entitled with "Flaring time interval distribution and spatial correlation of major X-ray solar flares"  is  published in the A12, 2001 issue of JGR-space physics.

 

Drexel University Report received from Peter MacNeice

 

In summary, we continued development work on our existing CME  `breakout' model code, continued development work on a High Order Godonov version, and  we filled a post-doctoral position.

 

We have implemented a revision of the Boris correction, in combination with a Lorentz factor, in an attempt to control spurious velocities associated with the cavitation phenomenon. We are currently testing this design.

 

We have begun building support for non-cartesian coordinates into the development version of Paramesh, in preparation for its use with the high order Godonov code under development.

 

We made an offer of a post-doctoral research position to Mr. Andrew Phillips from the University of Manchester, UK, contingent upon his successful completion of his PhD, which he has accept