P15

The Relationship between Nonthermal Velocities inDiãerent Temperature Regions of the Solar Lower Transition Region
S. Akiyama1;2 , G.A. Doschek1 , and J.T. Mariska1(1) E.O. Hulburt Center for Space Research, Naval Research Laboratory(2) Institute for Computational Sciences and Informatics, George Mason University, Fairfax, VA
We analyze the relationship between nonthermal velocities derived from spectral lines of ions formed atdiãerent temperatures in the solar lower transition region. The lines formed at diãerent temperatures
are observed simultaneously and at the same locations on the solar disk by the Solar Ultraviolet
Measurements of Emitted Radiation (SUMER) spectrometer on board the Solar and Heliospheric
Observatory (SOHO). In order to improve the accuracy of the nonthermal velocities determined fromthe full width at half maximum (FWHM) intensities of the lines, we select data with suécient counting
statistics such that the uncertainty of the nonthermal velocity is less than 10 % of its value derived fromthe FWHMs. Even without this restriction, we ånd a high degree of correlation between nonthermal
motions arising at temperatures ranging between about 3 Ç 104 K to about 2:5 Ç 105 K over 100 spatial

scales in quiet sun regions. We discuss the implications of these results in terms of the physical natureof the transition region.

P28

Downçow as a Reconnection Outçow
Ayumi Asai
Kwasan and Hida Observatories, Kyoto University
We present a detailed examination about the evolution of TRACE downçow motions (sunward motions) seen above post-çare loops. We found that they are seen not only in the decay phase but also
in the impulsive and main phases of çares. Moreover, we found that the times when the downçow
motions are seen correspond to those of the bursts of nonthermal emissions in hard X-rays and microwave. These results mean that the downçows occurred when strong magnetic energy was released,
and that they are, or are correlated with, the reconnection outçows. We also propose an observationof downçows as the reconnection outçows by Solar-B.

9

P33

The Relationship between Prominence Eruptions and Global Coronal Waves
G. Attrill, L.K. Harra, S.A. Matthews, C.A. Foley, and A.C. Sterling
Mullard Space Science Laboratory, University College London
There has been much debate over the physical mechanism for producing global coronal waves (`EIT
waves'). These waves are seen as a bright wave front followed by a region of dimming, and have speedsof approximately several hundred km/s. When they were årst discovered (Thompson et al. 1999) it
was thought that they may well be the coronal MHD waves that Uchida had described in 1968. Heproposed that the well observed Moreton waves observed in Hã are the footprints of a fast-mode wave
in the corona. However there are not many observations of both coronal waves and Moreton waves
simultaneously. Other authors have suggested that coronal waves are not related to Moreton waves,
but are coronal mass ejections lifting oã the disk (e.g. Delannee and Aulanier 1999).
Harra and Sterling (2003) showed an example of a coronal wave that occurred in association witha ålament eruption. Biesecker et al. (2002) showed that there is a very strong relationship between
the formation of a coronal wave, and the appearance of a coronal mass ejection. In this work, weinvestigate whether ålament eruptions are directly associated with coronal waves. We analyse 45
coronal waves and search for evidence of ålament eruptions. We used SOHO-EIT data, and any
available ground-based Hã data to search for ålament eruptions, and found that more than 50 % ofcoronal waves are clearly associated with eruptions. The speeds of the coronal waves, and the ålament
eruptions are similar. We discuss the implications of these results.

Oral

Observing the Reconnection Outçow Termination Shock during Solar Flares
Henry Aurass
Astrophysikalisches Institut Potsdam
Believing models of magnetic reconnection during solar çares, and knowing cusp structures in YOHKOHSXT, and also SOHO-EIT and TRACE images, stimulate the search for observations of the standingor slowly moving fast mode shock below resp. above the diãusion region. We report on radio çarespectra with non-drifting high-frequency type II burst-reminiscent sources in the late stage of someçares. Further, we recognized already in the impulsive çare phase the same non-drifting resp. slowly
drifting spectral patterns, in some cases with alternating çux densities at (roughly) 350 and 60 MHz.
This corresponds with an alternating upward- and downward-streaming supermagnetosonic outçow.
We compare the analysis of the radio spectra with simultaneously visible cusp features in SOHO-EIT
images. The superposition of Nancay Multifrequency Radioheliograph images supports our interpretation of the spectra. Thus, radio spectra together with imaging data in diãerent spectral rangesconårm a further observable ingredient of magnetic reconnection during solar çares.

10

Oral

Recent Progress in High Resolution Observations
Tom Berger
Lockheed Martin Solar and Astrophysics Lab
I review recent progress in high-resolution observations of the solar photosphere and chromosphere. In
this context, all observations are from ground-based instruments achieving 0:300 resolution or better.
We will focus on four recent eãorts:
1. Adaptive optics at the Swedish 1-meter Solar Telescope (SST) on La Palma
2. Speckle imaging at the VTT on Tenerife
3. Adaptive optics at the Dunn Solar Telescope (DST) at Sac Peak
4. High resolution spectropolarimetry with the DST/DLSP
We conclude with a list of science topics derived from the recent observations that are well suited forinvestigation by Solar-B.

P29

Spectroscopic Detection of Magnetic Reconnection Evidence
in the Solar Atmosphere with Solar-B/EISDavid H. Brooks
Kwasan Observatory, Kyoto University
2.5D MHD simulations of CMEs and çares are combined with improved accuracy density sensitive line
emission contribution functions from the ADAS database to study proåles of spectral lines which will
fall within the wavelength range of the Solar-B Extreme ultraviolet Imaging Spectrometer (EIS). The
objective is to study the signatures of magnetic reconnection associated çow phenomena in the lineproåles. 90 spectral lines of diãerent transition types from ions of several elements are considered. We
assess which of the lines are best suited for detecting/analysing the considered plasma motions anddetermine the optimal lines of sight for mass çow detection. We also conduct a survey of the inçuenceof simulation parameters such as electron temperature and density and the eãects of heat conduction.
Illustrative results are presented for the reconnection jet, reconnection inçows, the coronal counterpartof the Moreton wave and the slow shock attached to the reconnection jet (or outçow).

11

P1

The Decay of a Simulated Pore
R. Cameron, A. V°
ogler, S. Shelyag, and M. Sch°
usslerMax-Planck-Instut f°
ur Aeronomie
Using MURAM { (the Max-Planck Institute for Aeronomy, University of Chicago, RAdiative Magnetohydrodynamics code), an MHD code which includes both radiative transfer and partial ionization, we
have studied the decay phase of a pore.
The simulations are suéciently realistic in their treatment of the photosphere to allow a directcomparison with current observations and are of suéciently high spatial and temporal resolutions toallow comparisons with upcoming observing missions.
We shall speciåcally discuss the nature and consequences of shallow åeld aligned convective rolls
which are an important feature of our solutions.

Oral

Chromospheric Heating and Dynamics
Mats Carlsson
Institute of Theoretical Astrophysics, University of OsloThe existence of a wide variety of wave-like phenomena are inferred from observations of the solar
upper atmosphere. Acoustic waves play an important role for the dynamics and energetics of thechromosphere but additional heating seems necessary even for the internetwork regions.
Table of contents:(1) Observational evidence(2) Generation of waves(3) Acoustic waves and shocks in the solar chromosphere(4) Mode conversion, refraction and reçection

12

P5

Asymmetric Stokes-V Proåles at the Penumbral Boundary of a Sunspot
Debi Prasad Choudhary1 , K.S. Balasubramaniam2 , and Yoshinori Suematsu3(1) Solar Physics Division, Marshall Space Flight Center/NASA(2) National Solar Observatory, Sunspot, NM(3) National Astronomical Observatory of Japan
We present the spectropolarimetric measurements of a sunspot in the active region NOAA 6958
(15S03W), situated near the central meridian disk passage. The follower polarity sunspot was somewhat symmetrically round shaped with an elongated penumbra. There were several opposite polarity
magnetic elements at, and beyond, the penumbral boundary. The Hã images of the sunspot show thebright emission regions near the penumbral boundary towards the sun-center, which was of opposite
polarity with respect to the main spot. The net-circular polarization (NCP) map shows that NCP isnegative in the inner part of the spot and positive at the penumbral boundary and near the Hã plage.
The Doppler velocities were determined by measuring the center-of-gravity (COG) of the Stokes-Iproåle and zero-crossing (ZC) wavelength of the Stokes-V proåles. The COG velocity map in generalagrees with the Evershed çow. In addition, it shows the up çow in the penumbral region. The ZC
velocities show the strong down çow at the penumbral boundary. Double-lobed Stokes-V proåles areobserved at the locations where the penumbral åbrils terminate, coinciding the Hã plage. The Double
lobed proåles had an unshifted component similar to the Stokes-V proåles of the sunspot penumbra
and a shifted component with a velocity of about 5 km/s. The amplitude of the second component
increases along the penumbral åbril as a function of the distance from the center of the sunspot.
In this paper we discuss the role of emerging çux in generating the observed double lobed proåles.
Based on our present observations, we propose to observe with the Solar-B Spectropolarimeter forunderstanding the nature of emerging çux near the sunspots.

13

Oral

X-ray and EUV Observations of Large-Scale Coronal Structures
J.L. Culhane
Mullard Space Science Laboratory, University College London
Large-scale coronal streamers, årst recognized in solar eclipse images and in white-light coronagraphdata, are now more frequently observed with space-borne coronagraphs e.g. LASCO on SOHO, to a
distance of ò30 Rå . Observations of emission from the corona by Yohkoh SXT and SOHO EIT at soft

X-ray and EUV wavelengths have revealed the nature of diãuse coronal structures to heights of ò 1.5{ 2.0 Rå above the limb. The SOHO spectrometers, CDS and SUMER, have been used for emission
line intensity studies of these structures with increasing Rå . The SOHO UVCS has undertaken UV
spectroscopy and visible polarimetry studies of the corona to a height of ò 12 Rå . Items of interestin the study of these large structures include i) shape and evolution, ii) values of temperature, densityand element abundance, iii) solar cycle variation, iv) origin of the slow solar wind, and v) energy

supply and the role of the magnetic åeld. Yohkoh SXT observations of large coronal structures,
made in the period before December 1992, will be discussed. Subsequent observations by the SOHO
instruments relevant to these systems will be reviewed along with further Yohkoh results from joint
Yohkoh/SOHO campaigns. In relation to energy supply, recent work on the relationship between
coronal X-ray radiance and emerging magnetic çux, using data from Yohkoh/SXT and SOHO/EIT
along with magnetic åeld observations with SOHO/MDI and ground-based observatories (Pevtsov etal. 2003, in press), will be presented. Finally the properties of large transequatorial loop systems
will be reviewed. Although simpler than streamers, these structures have their origin in similarly
widely separated activity centres. While their behaviour is often more dynamic in terms of therelated occurrence of çare-like activity and CMEs, sharply cusped streamers are also often associatedwith CME launches and have associated underlying prominence material. Thus the existence oftransequatorial loops may also be related to the global magnetic åeld of the sun.

14

Oral

Dynamo Models
Mausumi Dikpati
High Altitude Observatory, NCAR
Cyclic evolution of solar magnetic features is believed to be due to a dynamo operating in the Sun.
Solar dynamo mechanisms in the past involved two basic processes: (i) generation of toroidal åelds
by shearing pre-existing poloidal åelds by diãerential rotation (the omega-eãect), (ii) re-generationof poloidal åelds by lifting and twisting of toroidal çuxtubes (the alpha-eãect). According to recent
concepts, it also involves an essential third process { çux transport by meridional circulation. Fluxtransport type solar dynamos have been very successful in explaining many large-scale solar cyclefeatures, including the phase relationship between the equatorward migrating sunspot belt and thepoleward drifting large-scale, diãuse åelds. This has been a particularly diécult feature to reproduce.
The dynamo cycle period in such models is primarily governed by the meridional çow speed. After
giving a historical background on classical dynamo models, we review the successes of various recent
çux-transport dynamos. We will then demonstrate how the meridional circulation plays a key role ingoverning the Sun's memory about its own magnetic åeld. Therefore, a çux-transport dynamo-based
scheme can be built and that can be used as a tool for predicting future solar cycles. We will close byshowing how this predictive tool can explain the cause of the very slow polar reversal in the so-called\peculiar" cycle 23 (compared to that in cycles 20, 21 and 22).
We acknowledge support from NASA through awards W-19752, W-10107 and W-10175.

Oral

Dynamics of Emerging Flux Tubes
Yuhong FanHigh Altitude Observatory, NCAR
Bipolar magnetic regions on the solar surface are believed to correspond to the topmost portions of äshaped arching çux tubes that have risen buoyantly from the base of the solar convection zone, wherestrong toroidal magnetic åelds are being generated by the dynamo process. The dynamic evolution ofsuch rising çux tubes in the solar convection zone has been studied extensively using a simpliåed thinçux tube model, and more recently with direct multi-dimensional MHD simulations. In this talk I
will give an overview of some recent results of MHD simulations of the formation and dynamic rise of
buoyant ä loops in the solar convection zone. I will discuss the question about the necessary twist for
maintaining cohesion of the rising çux tubes and how 3D stratiåed convection can aãect the rise andthe structure of buoyant çux tubes. Finally I will also show simulations of the emergence of twisted
magnetic çux tubes into the solar atmosphere.

15

Oral

Large-Scale Coronal Dynamics
Peter T. Gallagher
NASA Goddard Space Flight Center
Modern ground- and space-based observatories such as TRACE, RHESSI, SOHO, Yohkoh, and BBSO
have provided new insights into the large-scale dynamics of the solar atmosphere. As new details are
revealed, theorists are challenged to provide quantitative explanations of the observed structures andtheir evolution. In this review, I will discuss our current theoretical and observational understandingof: pre-eruption structures (loops, ålaments, active regions) seen at Hã, EUV, and X-ray wavelengths;
the initiation and acceleration of CMEs in the low corona with particular regard to recent åndings
from RHESSI and TRACE; and the subsequent expansion and propagation of CMEs into interplanetary space visible with the LASCO instrument onboard SOHO. Additional large-scale dynamical
phenomena such as coronal dimmings, streamer blow-outs, and recent evidence for current-sheet formation will also be discussed.
Table of contents:{ Introduction{ Active Region and Filament Evolution{ Magnetic åeld topology from the photosphere to the corona{ The complexity of magnetic åelds
{ Energy build-up via çux emergence/motion{ Trigger Mechanisms{ Interacting magnetic åelds
{ Magnetic reconnection{ MHD instabilities{ Compact and Eruptive Events{ The relationship between çares, ålaments, and CMEs
{ Driving eruptive events: Current sheet formation{ Recent advances in CME modeling (Break-out, çux rope, etc)

16

P22

Relating Magnetic Field Strengths to Hard X-ray Emission in Solar Flares
C.P. Goã, S.A. Matthews, and L.K. Harra
Mullard Space Science Laboratory, University College London
The observation of hard X-ray emission in solar çares provides important diagnostic information
about the acceleration and subsequent transport of energetic electrons in the çare process. While
hard X-rays are thought to be emitted from çare footpoints through thick-target Bremsstrahlunginteractions, the details of the transport of accelerated electrons through the solar atmosphere still
remains unclear. Trapping of the electrons is one particular eãect that is expected to occur as a resultof the convergence of the magnetic åeld between the corona and the chromosphere. In this case thebrightness of the HXR footpoints should be related to the strength of the magnetic åeld present and wewould expect greater precipitation and higher HXR intensities at footpoints with lower magnetic åeldstrengths. Using data from Yohkoh's Hard X-ray Telescope (HXT) and SOHO's Michelson Doppler
Imager (MDI) we have studied the magnetic åeld strengths at the footpoints of a sample of over 40çares and have compared them to the hard X-ray brightness. We present results on a number of
events where brighter hard X-ray sources lay in regions of higher magnetic åeld strength in contrast
to those which follow the Sakao (1994) relation of the brightest source forming in the weaker magnetic
åeld, as would be expected through the argument of magnetic trapping. The implications of theseresults in terms of standard çare models are discussed.
Solar-B's Focal Plane Package (FPP) vector magnetograph will provide us with much better estimates of the magnetic åeld strength at the footpoints. In addition, measurements of plasma çow
velocity from Solar-B EIS will allow us to determine more fully the mechanisms involved.

Oral

XRT DEM Diagnostics
Leon Golub
Smithsonian Astrophysical Observatory
The X-ray Telescope (XRT) çown on the Solar-B mission will be the highest spatial resolution Xray telescope ever çown for solar studies, with performance at wavelengths > 60 ó
A limited only bydiãraction. The XRT also has an exceptionally broad temperature response and highly versatile focal
plane analysis ålters, with thicknesses ranging from 0.16 ñm to 1 mm. Combined with the shutter
speeds of 1 ms to > 1 s and the large dynamic range of the CCD camera, the XRT is sensitive toa range of > 1010 in coronal X-ray brightness. In this paper we examine the ability of the XRT toaccurately reproduce the diãerential emission measure (DEM) of a coronal emission source. We havedeveloped a DEM analysis tool (which will be made available to the public as part of the Solar-B
analysis software) that uses a forward-feedback method to perform spline åts and ü2 -minimization to
produce a DEM distribution from a set of observations. We ånd that the XRT produces accurate åts,and we note that a) a large enough set of ålters must be used if accurate DEMs are to be obtained,
and b) the åts must be carried out over a range of coronal temperatures consistent with the ålters
being used.

17

P11

Phase Relationship between the Activity Cycles of Sunspots and Polar Faculae
Masaoki Hagino1 , Takashi Sakurai1 , and Ayako Miyazawa2(1) National Astronomical Observatory of Japan(2) Department of Aeronautics and Astronautics, Tokai University
The number of polar faculae shows an eleven-year cyclic variation, but its phase is shifted by half acycle with respect to the sunspot activity cycle. Namely, polar faculae are most numerous at sunspot
minimum, and vice versa. Polar faculae represent poloidal magnetic åelds in polar regions, while
sunspots represent toroidal magnetic åelds. Therefore, the phase relationship among the two will be
important in studying the basic driving mechanism of solar activity. Speciåcally, we are interested
in whether sunspots are better correlated with polar faculae of the previous cycle or of the following
cycle.
We analyzed the counts of sunspots and polar faculae recorded on sunspot drawings obtained at
Mitaka over four activity cycles. These counts were separately obtained for northern and southernhemispheres. We adopted two methods to study the phase relationship between sunspot and facularcounts. The årst method is the usual cross-correlation analysis. The second method uses a wavelet
transform and the progression of the phase of the wavelet transform is studied. Both methods givethe same trend in that the polar faculae are better correlated with the sunspots of the previous cycle.
Compared to this trend, the correlation of the sunspot counts with the polar faculae of the previous
cycle is weaker.

P23

Hã Impact Polarization Observed in a Gradual Flare
Yoichiro Hanaoka
National Astronomical Observatory of Japan
Linear polarization of chromospheric lines including the Hã line observed in solar çares is interpreted as impact polarization produced by accelerated high-energy particles precipitating into thechromosphere. We started a regular observation of linear polarization in the Hã line in 2002 July at
NAOJ/Mitaka, and we detected linear polarization in the çare kernels of a gradual çare, which was
accompanied by a ålament eruption. The maximum degree of polarization of this çare exceeds 1 %,and the orientation of the polarization is approximately perpendicular to the çare ribbons. These
results can be explained with the assumption that the observed polarization is impact polarization
produced by accelerated protons. The hard X-rays observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) show a thermal component, but there is no detectable power-law
component due to accelerated electrons. Therefore, protons are presumed to be not only the cause of
the polarization, but also a possible candidate of the principal heating agent in this çare, which lacks
high-energy electrons.
Although the linear polarization was detected in the above çare, most of the observed çares show no
detectable (>1 %) polarization. Therefore, more precise polarimetry is required to study the impact
polarization further. We are planning to start the polarimetry with a new polarimeter equipped withferroelectric liquid crystals, and on the other hand, we are expecting Solar-B, because the SOT has
a high polarimetric performance in some chromospheric lines as well as in the photospheric lines forthe magnetic measurements.

18

P14

Variation of the X-ray Bright Point Number over the Solar Activity Cycle
Hirohisa Hara1 and Kayoko Nakakubo2(1) National Astronomical Observatory of Japan(2) Suginami Science Center, Suginami-ku, Tokyo
We have counted the number of X-ray bright points (XBPs) in the quiet-Sun region from Yohkoh soft
X-ray images during a period of 1993{2000. Since we deåne XBPs as a small region that is less than
60 arcsec with a signiåcantly enhanced emission in soft X-ray intensity compared with the adjacent
background corona, the number of XBP in the whole Sun area is aãected by the soft X-ray intensityof the background corona and the presence of the solar active regions. Under these conditions, thenumber of XBPs in the whole Sun area is anti-correlated with the sunspot number owing to thechange of background X-ray intensity and the occultation by active regions during the 11-year solar
activity cycle. In order to estimate the real number variation with little artifact, we have calculated
the number of XBPs in a unit area by limiting the X-ray intensity range of the background coronaand by removing a bias eãect of a selected intensity threshold for the XBP counting. The evaluatedchange of the XBP number density in the quiet Sun is less than a factor of two over the period in
the present study, and there is no clear enhancement in XBP number near the solar minimum. We
conclude that the number density of XBPs is nearly independent of the 11-year solar activity cycle.
Since an XBP found in the quiet Sun is recognized to be an event which is produced through aninteracting process of opposite-polarity magnetic åelds in the quiet Sun, the low-amplitude variationof the XBP number density suggests that there is a mechanism to create solar magnetic åelds, which
are diãerent from those associated with active regions, irrespective of the 11-year solar activity cycle.

19

P34

Flare-Induced Coronal Disturbances Observed with
Norikura `NOGIS' Coronagraph : A CME Onset
Kuniko Hori1 , Kiyoshi Ichimoto2 , Takashi Sakurai2 , Yohei Nishino2 , and NOGIS Team(1) Hiraiso Solar Observatory, Communications Research Laboratory(2) National Astronomical Observatory of Japan
We present the årst detection of a CME onset in the coronal green line emission (Fe xiv 5303 óA,
2 MK) by a 2D Doppler coronagraph `NOGIS' at the Norikura Solar Observatory, NAOJ. The NOGIS
instrument can measure the line-of-sight velocity of a 2 MK plasma up to 25km/s with a sensitivityof about 1 km/s.
The event we report was associated with an M6.5 çare on June 2, 2003 that occurred in the
AR #10365 located at the west limb. The NOGIS observed the çare region (S06) together withan aggregate of face-on loops lying above a quiescent ålament (N15) within a FOV of 67700 Ç 89800(1:8400 /pixel). The observation continued over 10 hours with a 43 s cadence. As the solar disk
was occulted up to the height of 3000 in the NOGIS images, we examined the evolution of the çareó (1.6 MK) images and microwave (17 GHz) images from the Nobeyama
region using SOHO EIT 195 A
Radioheliograph. We also examined the white-light images from the SOHO LASCO/C2 coronagraphto grasp a CME and surrounding streamers during the event.
The årst precursor of the çare-CME event was a gradual enhancement in the intensity of the green
line in tall edge-on loops that occupied the space between the AR #10365 and the loop system centeredat N15. After 30 minutes from the start of this intensity enhancement, the ejection of a blue-shifted
collimated jet was observed between the feet of the intensity-enhanced loops (S05), together witha çare expansion in the neighboring AR #10365. These expansions produced a blue-shifted blast
wave, or an expanding low-density bubble, that propagated toward the outer corona with an initial
velocity of 400 km/s. A signiåcant dimming region appeared after the passage of the blast wave inthe coronal green line and in the EUV emission. The blast wave pushed the southern side of the loop
system at N15 and triggered a damped oscillation in Doppler shifts that apparently propagated fromthe inner toward the outer loops within the loop system over 100 minutes. After 44 minutes fromthe start of the çare expansion, the LASCO/C2 observed a partial halo CME that had an angularextension corresponding to the northern end of the loop system and the southern end of the AR#10365, respectively.
On the basis of the coronal disturbances described above, we will discuss how and where the CME
plasma was supplied and what triggered the massive ejection. An application to the EIS observation
will be proposed considering the ability of the temperature diagnosis of the EIS.

20

P19

Studies on the Flare Energy Build-up Process Using
Solar-B/Solar Optical Telescope (SOT) and
Solar Magnetic Activity Research Telescope (SMART) at Hida Observatory
T.T. Ishii, S. Nagata, S. Ueno, R. Kitai, and H. Kurokawa with SMART TeamKwasan and Hida Observatories, Kyoto University
Evolution of active regions is one of the key topics for understanding the energy storage and triggering
mechanisms of çares. In our previous studies, we found that the twisted structure of emerging magnetic
çux bundles is the essential feature of çare-productive active regions (Ishii et al. 2000; Kurokawa
et al. 2002). Vector magnetic åeld data sets are necessary to examine the twisted magnetic åeldstructures (e.g. shear and helicity). The Solar-B/Solar Optical Telescope (SOT) enables us to study
the detailed magnetic åeld conåguration with a high spatial resolution. Recently we have constructed
our new telescope, Solar Magnetic Activity Research Telescope (SMART) at Hida Observatory. Vector
magnetic åeld telescope of SMART has a much wider åeld of view (FOV) than that of SOT. In thispresentation, we propose an observational plan of the active region evolution and çare energy build-up
process using SOT and SMART.

P2

Three-Dimensional MHD Simulation of Convection and Emerging Flux
Hiroaki Isobe
Kwasan and Hida Observatories, Kyoto University
We report the results of a three-dimensional MHD simulation of convection and çux emergence into
the upper atmosphere. Our primary goal is to investigate the interaction of convection and magnetic
åeld, particularly the eãect of convection on the emerging çux. The simulation domain includes theupper convection zone, photosphere, chromosphere and corona. Initially, statistically steady and åeldfree convection is developed in the model convection zone, then magnetic åeld, either horizontal sheetor twisted tube, is injected in the convection zone. Our preliminary results show that the emerging
çux is broken by the convective çow and cannot keep coherence even when the åeld strength is asstrong as the equipartition value with the kinetic energy of convective çow.

21

Oral

Properties of Photospheric Magnetic Fields at Footpoints of Hot and Cool Loops
Yukio Katsukawa1 and Saku Tsuneta2(1) Department of Astronomy, University of Tokyo(2) National Astronomical Observatory of Japan
Coronal loops are not represented by single temperature, but cover wide temperature ranges. Cool(Tò 1 MK) and hot (T>2 MK) loops are not spatially coincident. The heating rate has to diãer by one
order of magnitude to produce such diãerent temperatures. Properties of magnetic åelds at footpointsof the hot and cool loops are investigated with Advanced Stokes Polarimeter (ASP) coordinated with
SXT and TRACE to understand what makes the large diãerence in the heating rate.
Footpoints of the hot loops are diãuse when observed with SXT, and the identiåcation of footpoint
locations is ambiguous. We instead use the moss observed with TRACE, which is low-lying EUV
emission at footpoints of hot loops, to identify the footpoint locations of the hot loops. Properties ofphotospheric magnetic åelds observed with ASP are compared between moss regions and footpointsof the cool loops. Both regions have magnetic åelds whose strength is 1.2 kG and the orientationis vertical to the surface. A signiåcant diãerence between the moss and the cool loops is found in
the magnetic ålling factor, which is deåned by the fraction of the resolution element ålled with amagnetized atmosphere. Moss regions, i.e. the footpoints of the hot loops, have lower ålling factor
than the footpoints of the cool loops. This result suggests that dispersed magnetic elements at thephotosphere are more eécient to provide the heating energies to the corona, thus leading to the hotloops.

P24

Hard X-ray Spectral Observation of a High-Temperature Thermal Flare
K. Kobayashi1 , S. Tsuneta2 , T. Tamura2 , K. Kumagai2 , Y. Katsukawa1 , M. Kubo1 ,Y. Sakamoto1 , N. Kohara1 , T. Yamagami3 , Y. Saito3 , K. Mori4 , and G. Kato5(1) Department of Astronomy, University of Tokyo(2) National Astronomical Observatory of Japan(3) Institute of Space and Astronautical Science(4) ClearPulse, Co. (5) Mitsubishi Heavy Industries
We discuss the design and observational results of a balloon-borne hard X-ray spectrometer developed
at the National Astronomical Observatory of Japan. The instrument uses sixteen 10 Ç 10 Ç 0:5
mm CdTe detectors, and achieves 3 keV energy resolution over an energy range of 15{120 keV. The
instrument is designed for a 1-day balloon çight at an altitude of 42 km. Two çights were conducted
in 2001 and 2002. The second çight, on May 24, 2002, succeeded in observing a class M1.1 çare.
Our data indicate that this is an unusual çare, having an extremely hot 47 MK thermal component
and no detectable non-thermal component. The RHESSI satellite observed the årst part of the çare,and our analysis shows that the RHESSI data are consistent with ours. Simultaneous data from theNobeyama Radio Polarimeter can also be explained by thermal processes alone.

22

Oral

Helioseismology for Solar-B and Joint Investigations with SDO/HMI Project
Alexander Kosovichev
Stanford University
New methods of local helioseismology provide information about subsurface convective and shear çows,thermal and magnetic structures, which is critical for accomplishing the Solar-B scientiåc objectives.
I review the current status of acoustic tomography, observational requirements and limitations, anddiscuss observations of supergranular convection and helical motions, subsurface transport and çux
emergence, formation and decay of sunspots and active regions, and links between subphotospheric
dynamics, magnetic topology and coronal activity.

P7

Vector Magnetic Field of Moving Magnetic Features
around a Well-Developed Sunspot
Masahito Kubo1 and Toshifumi Shimizu2(1) Department of Astronomy, University of Tokyo(2) National Astronomical Observatory of Japan
We identify about 30 moving magnetic features (MMFs) to investigate their magnetic åeld structuresand horizontal motions. Stokes proåles obtained with Advanced Stokes Polarimeter are examined withthe magnetogram movie of SoHO/MDI. MMFs are small magnetic features, which move outward fromthe penumbral edge of sunspots.
It is found from viewpoint of vector magnetic åeld and its motion that MMFs can be classiåed into
three types. The årst type of MMFs has magnetic åelds nearly parallel to the solar surface (< 10é)with the horizontal velocity of 400{700 m/sec. The second type of MMFs has magnetic åelds with
40{60 degrees to the surface and rather slow horizontal velocity (< 400 m/sec). The third type isbetween the årst and second types. This presentation will discuss the magnetic åeld properties of
MMFs in terms of the three types including their spatial distribution in radial and azimuth direction,
which may help us to understand the decaying process of sunspots.

23

Oral

Study of Magnetic Helicity in the Solar Corona
Kanya Kusano
Graduate School of Advanced Sciences of Matter, Hiroshima University
Magnetic helicity, which is a measure of magnetic çux linkage, is widely believed as an important
quantity for the understanding of stability and equilibrium of the magnetohydrodynamic plasmas inseveral systems. Although a great attention has been paid to the role of magnetic helicity in the solar
corona, the physical relationship between magnetic helicity and the coronal activity, for instance solarçares, is not yet well understood. In this talk, we will årst review the recent progress in the magnetic
helicity physics of the solar corona about the following three topics,(1) the methodology of helicity measurement,(2) the correlation with coronal heating, and(3) the trigger mechanism of solar çares.
In particular, we will present a new model that solar çares can be triggered by the annihilation ofmagnetic helicity, based on the observational and numerical studies carried out in our group recently.
Secondly, we will discuss about what we can do and what we should do about the study of magnetic
helicity with Solar-B program.

P36

Investigation of Loop-Type CMEs with 3D MHD Simulations
Joji Kuwabara1 and Yutaka Uchida2;y(1) Graduate University for Advanced Studies, National Astronomical Observatory of Japan(2) Science University of Tokyo
The loop-type CMEs, which are one of the two types of CMEs we found (Uchida et al. 2001), havea characteristic structure suggestive of helical instability in a magnetic loop, namely, both footpoints
being åxed on the solar surface during the time evolution. We also found that, before the occurrenceof some CMEs, there are already magnetic åeld lines linking the footpoints of the loop-type CME
and the region where the associated arcade çare is to take place. We here propose a scenario for the
loop-type CMEs based on these observations as follows.
Before a loop-type CME to occur, the large-scale magnetic åeld of the relevant region is composedof (1) a separated pair of magnetic sources located at the footpoints of the subsequent loop-type CME,
and (2) another, smaller pair of poles located somewhere between the footpoints where the associatedarcade çare is to take place. The torsional Alfvì
en wave packets (TAWPs) may escape from the arcadeçare region and propagate to the footpoints of the loop-type CME. The TAWPs are then reçected at
the footpoints and propagate upward along the large loop newly formed by the magnetic reconnection.
The packets may eventually collide at the loop top.
We treat such a situation with 3-dimensional MHD simulations, in order to understand the physicalmechanisms involved in the process of the deformation and acceleration of the loop-type CMEs.
ydeceased 2002 August 17

24

P8

Measuring Magnetic Helicity Transport in Solar Active Regions:
The Need for Vector Magnetic Fields
B.J. LaBonte, M. Georgoulis, and D.M. Rust
Johns Hopkins University, Applied Physics Laboratory
The emergence and accumulation of twisted (helical) magnetic åelds in the solar atmosphere are essential in the process which powers solar çares and eruptions. Berger and Field (J. Fluid Mech., 147,
144, 1984) showed that the çow of helicity into a volume comprises two terms. Advection twists preexisting åelds. Emergence carries pre-twisted åelds into the volume directly. On the Sun, the emergenceterm is not measurable from line-of-sight magnetic observations; it requires vector åeld observations.
We have derived a set of analyses that permit a full characterization of helicity transport from vectoråeld observations using data from the Mees Solar Observatory Imaging Vector Magnetograph. These
include the rate of helicity transport, as well as the time series of the actual helicity content. We anticipate better physical understanding of helicity transport from the improvements in spatial resolution
using Solar-B, and in global perspective using Solar Dynamics Observatory.

P6

Three-Dimensional Structure of the Active Region Photosphereas Revealed by High Angular Resolution
B.W. Lites1 , G.B. Scharmer2 , T.E. Berger3 , and A.M. Title3(1) High Altitude Observatory, NCAR
(2) Institute for Solar Physics, Royal Swedish Academy of Sciences(3) Lockheed Martin Solar and Astrophysics Lab
Blue continuum images of active regions at ò 60é from the center of the solar disk obtained with

the new Swedish 1-m Solar Telescope reveal heretofore unreported structure of the magnetized solar
atmosphere. Perhaps the most striking aspect of these images is that, at an angular resolutionof 0:1200 , they show clearly the three-dimensional structure of the photosphere. In particular, theWilson depression of the dark çoors of pores is readily apparent. Conversely, the segmented structureof light bridges running through sunspots and pores reveal that light bridges are raised above thedark surroundings. The geometry of light bridges permits estimates of the height of their central(slightly darker) ridge: typically in the range 200 { 450 km. These images also clearly show thatfacular brightenings outside of sunspots and pores occur on the disk-center side of those granules justlimbward of intergranular lanes that presumably harbor the associated plage magnetic çux. In manycases the brightening extends 0:500 or more over those granules. Furthermore, a very thin, darker
lane is often found just centerward of the facular brightening. We speculate that this feature is thesignature of cool down çows that surround çux tubes in dynamical models. These newly recognizedobservational aspects of photospheric magnetic åelds should provide valuable constraints for MHD
models of the magnetized photosphere, and examination of those models as viewed from obliqueangles is encouraged.

25

P25

Particle Acceleration Associated withThree-Dimensional Fan Magnetic Reconnection
Yuri Litvinenko
University of New Hampshire
Particle acceleration associated with three-dimensional magnetic reconnection is analyzed. Orbitsof charged particles in the current sheet located in the fan of a magnetic null point are describedanalytically in both nonrelativistic and ultra-relativistic limits. An orbit instability eãect is described,
which limits the acceleration times and kinetic energy gains in the reconnection-related electric åeld.
The results are discussed using exact MHD solutions for fan reconnection, discovered by I.J.D. Craig
and co-workers. The use of an analytical self-consistent MHD solution to derive the magnetic åeldconåguration near the null point leads to constraints on local parameters in the magnetic reconnection
region. As a consequence, simple conditions can be identiåed for eãective particle acceleration inrealistic reconnecting geometries. Applications to particle acceleration in solar çares are discussed.

Oral

Injection of Magnetic Energy and Magnetic Helicity into the Solar Atmosphereby an Emerging Magnetic Flux Tube
Tetsuya Magara
Naval Research Laboratory and University of California, Berkeley
We present a detailed investigation of the dynamical behavior of emerging magnetic çux using 3dimensional MHD numerical simulation. A magnetic çux tube with a left-handed twist, initiallyplaced below the photosphere, emerges into the solar atmosphere. This leads to a dynamical expansionof emerging åeld lines as well as an injection of magnetic energy and magnetic helicity into theatmosphere. The åeld-aligned distributions of forces and plasma çows show that emerging åeld lines
can be classiåed as either expanding åeld lines or undulating åeld lines. A key parameter determining
the type of emerging åeld line is an aspect ratio of its shape (the ratio of height to footpoint distance).
The emergence generates not only vertical çows but also horizontal çows in the photosphere, bothof which contribute to injecting magnetic energy and magnetic helicity. The contributions of verticalçows are dominant at the early phase of çux emergence, while horizontal çows become a dominant
contributor later. The emergence starts with a simple dipole structure formed in the photosphere,
which is subsequently deformed and fragmented, leading to a quadrupolar magnetic structure.

26

P20

Coronal Hard X-ray Source Accompanying a Plasma Ejection
Satoshi Masuda
Solar-Terrestrial Environment Laboratory, Nagoya University
In many of çares occurring near the solar limb, a hot-plasma ejection is observed in soft X-rays during
the impulsive phase. This is one of evidence to support the çare models which are based on the cusptype magnetic reconnection high in the corona. Sometimes a compact hard X-ray source is observed
above the soft X-ray çaring loop at the same time. This clearly indicates that the çare-energy release,probably magnetic reconnection, occurs above the soft X-ray loop. Fast-reconnection downward çow
impinges on the closed magnetic loops and high-energy electrons are produced there. In this scenario,
the above-the-looptop hard X-ray source is directly related to the reconnection downward çow.
How is the reconnection upward çow observed? Recently it is found in the impulsive phase of an
M-class çare that a hard X-ray (above 20 keV) source exists slightly below a soft X-ray ejected feature
which is located far above the soft X-ray çaring loop. This hard X-ray source might be a counterpartof the hard X-ray source related to the downçow. This might be caused by interaction between thereconnection upward çow and the ejected hot-plasma. We discuss how such high-energy electrons areproduced there.

Oral

Conservation of Both Current and Helicity in Solar Flares
Don Melrose
School of Physics, University of Sydney
A model for magnetic reconnection transferring magnetic çux and current between two pairs of footpoints (Melrose 1998) is modiåed to take account of conservation of magnetic helicity. The helicity
is expressed in terms of a double integral over the current, analogous to the double integral for themagnetic energy, which is approximated by a sum of a discrete set of currents and their self andmutual helicities. It is argued that the double integral for the helicity may be approximated in an
analogous way by using the force-free condition. The conditions under which magnetic reconnection
is energetically favorable, conserving both the net current and the net helicity, are explored.

27

P3

Jet Phenomena in the Solar Atmosphere Caused by Interaction
between Emerging Flux and Pre-Existing Coronal Magnetic Fields
Takehiro Miyagoshi1 , Hiroaki Isobe1 , Takaaki Yokoyama2 , and Kazunari Shibata1(1) Kwasan and Hida Observatories, Kyoto University(2) Department of Earth and Planetary Science, University of Tokyo
We have studied solar coronal jet phenomena theoretically with MHD numerical simulations. Emerging çux interacts with pre-existing magnetic åelds in the upper atmosphere through magnetic reconnection process. Then, enormous magnetic energy is released and magnetic topology drasticallychanges. Jet phenomena are caused through this process by released thermal energy and/or magnetic pressure, and so on. We introduce our theoretical results with MHD numerical simulations, andsuggest the targets for Solar-B mission.

Oral

Coronal Heating, Spicules, and Solar-B
Ron Moore, David Falconer, Jason Porter, David Hathaway1 , and Yohei Yamauchi2(1) NASA/MSFC/NSSTC (2) NRC/MSFC/NSSTC
Falconer et al (ApJ, 593, 549, 2003) investigated the heating of the quiet corona by measuring theincrease of coronal luminosity with the amount of the magnetic çux in the underlying network at
solar minimum when there were no active regions on the face of the Sun. The coronal luminosity
was measured from Fe ix/x{Fe xii pairs of coronal images from SOHO/EIT, under the assumptionthat practically all of the coronal luminosity in these very quiet regions came from plasma in thetemperature range 0:9 Ç 106 K < T < 1:3 Ç 106 K. The network magnetic çux content was measured

from SOHO/MDI magnetograms. It was found that luminosity of the corona in these quiet regions
increased roughly in proportion to the square root of the magnetic çux content of the network androughly in proportion to the length of the perimeter of the network çux clumps. From (1) this result,(2) the observed occurrence of many åne-scale explosive events (e.g., spicules) at the edges of networkçux clumps, and (3) a demonstration that it is energetically feasible for the heating of the corona inquiet regions to be driven by explosions of granule-sized sheared-core magnetic bipoles embedded in
the edges of the network çux clumps, Falconer et al. (2003) infer that in quiet regions that are notinçuenced by active regions the corona is mainly heated by such magnetic activity in the edges of the
network çux clumps. From their observational results together with their feasibility analysis, Falconer
et al. (2003) predict that (1) at the edges of the network çux clumps there are many transient shearedcore bipoles of the size and lifetime of granules and having transverse åeld strengths greater than ò
100 G, (2) ò 30 of these bipoles are present per supergranule, and (3) most spicules are produced by
explosions of these bipoles. The photospheric vector magnetograms, chromospheric åltergrams, andEUV spectra from Solar-B are expected to have suécient sensitivity, spatial resolution, and cadence
to test these predictions. The mixed-polarity magnetic çux at the base of spicules which Falconer etal. (2003) inferred is compatible with the observed magnetic structure of Hã macrospicules recently
found by Yamauchi et al. (Y. Yamauchi, R.L. Moore, S.T. Suess, H. Wang, and T. Sakurai, The
Magnetic Structure of Hã macrospicules in Solar Coronal Holes, submitted to ApJ, September 2003,
and presented as a poster paper here at the Fifth Solar-B Science Meeting).

28

P18

Coordinated Observation by Solar-B andSolar Magnetic Activity Research Telescope (SMART)for Probing the Coronal Loop Heating Mechanism
S. Nagata and SMART TeamKwasan and Hida Observatories, Kyoto University
Multi-temperature nature of the solar corona has been extensively studied by the recent X-ray and
EUV observations. In terms of temporal behavior the corona is composed of a high temperature(T > 5 MK) transient component and a low temperature (T < 5 MK) persistent component (Yoshida
and Tsuneta 1996). It is revealed that loops consisting the persistent component are not isothermal
and the peak temperatures of their diãerential emission measure distributions are diãerent with eachother (Nagata et al. 2003; Schmelz et al. 2001). These observations imply that the inhomogeneityof the coronal heating rate is distributed in a scale of loop size (100 {500 ) at the photosphere. In
this paper, we discuss the coordinated observation plan for the coronal loop heating study by Xray/EUV instrument aboard Solar-B and ground based wide åeld of view magnetograph on Solar
Magnetic Activity Research Telescope (SMART). The SMART is a new ground based solar telescope
constructed at Hida Observatory of Kyoto University and has two ålter vector magnetographs withwide åled of view (200000 Ç200000 {40000 Ç40000 ). We also report the results from recent joint observation
with Advanced Stokes Polarimeter at Sac Peak and SoHO CDS carried out as a preview science with
Solar-B and SMART.

Oral

Coronal Waves: Coronal Heating and Coronal Seismology
Valery M. Nakariakov
Physics Department, University of Warwick
SOHO and TRACE missions have demonstrated that wave phenomena are abundant in the coronaand provided us with an observational basis for MHD coronal seismology. This review covers therecent observational åndings of coronal wave phenomena and their theoretical models. The relevanceof these observational and theoretical eãorts to the coronal heating is discussed. An emphasis is put on
the observational strategies for the study of the coronal wave activity with EIS and XRT instruments.
The talk contents are:
1. Introduction: why waves are crucial for our understanding of coronal dynamics
2. The method of MHD coronal seismology
3. Direct observational evidence for coronal waves and observability of these phenomena with
Solar-B
3.1 Flare-generated kink oscillations of coronal loops
3.2 Propagating slow waves
3.3 Standing slow waves
3.4 Sausage modes
3.5 Propagating fast wave trains
4. Indirect observations of coronal waves: Observational strategies with Solar-B
5. Coronal heating by waves and how Solar-B can test it
6. Conclusions

29

P12

Kink Oscillations in the Solar Corona
A. Satya Narayanan, R. Ramesh, C. Kathiravan, and E. Ebenezer
Indian Institute of Astrophysics, Bangalore
The solar coronal plasma is highly structured in the magnetic åeld, density and temperature. This
plays a crucial role in the theory of MHD oscillations. These oscillations have been known to play animportant role in the heating of the corona. The presence of inhomogeneities in the corona makes it
diécult to have a global picture of the dynamics involved in understanding phenomena such as loop
structures, coronal holes, solar wind etc. In this study we model a coronal loop to be made up ofa cylindrical tube of constant cross-section. However, the magnetic åeld, the pressure and density
are assumed to be diãerent both inside and outside the tube (though uniform). The tube admits
oscillations such as sausage (symmetric), kink (asymmetric), surface and body modes. The dispersion
relation of the modes for a cylindrical tube which is compressible, inånitely conducting with uniformçows inside the tube is derived. Limiting cases such as no çows, incompressible çows, short andlong wavelength are discussed brieçy. The phase speed of the kink mode can be used as a diagnostic
for determining the magnetic åeld of the corona. It is clear from this study that the magnetic åelddepends on the distance between the foot points of the coronal loop, the period of oscillation andthe ratio of the plasma density both inside and outside the loop. For diãerent values of the coronalplasma parameters, the magnetic åeld varies from a few Gauss to 40 Gauss.

Oral

Observations of Flare-Associated Waves with Solar-B
Noriyuki Narukage
Kwasan and Hida Observatories, Kyoto University
In Hã, a çare-associated chromospheric wave (called Moreton waves) was discovered in 1960, andafter that such waves are sometimes observed. Uchida (1968, 1973, 1974) identiåed the Moreton wave
as the intersection of a coronal MHD fast-mode shock and the chromosphere. Recently, Yohkoh/SXT
observed coronal wave-like disturbances (X-ray waves). Narukage et al. (2002) showed that an X-ray
wave is an MHD fast-mode shock, i.e., a coronal counterpart of the Moreton wave. The Solar-B has
SOT, XRT and EIS on board and will be launched in 2006. We expect SOT, XRT and EIS will detect
chromospheric Moreton waves, coronal X-ray waves and line-of-sight velocity of waves, respectively.
In preparation for Solar-B, we examine the detection possibility of waves with these telescopes andsuggest the observational methods.

30

Oral

Magnetohydrodynamics of the Solar Atmosphereó
Ake Nordlund
Niels Bohr Institute, University of Copenhagen
I will review recent progress in the understanding of solar atmospheric magnetohydrodynamics, triggered by new high resolution observations and by recent advances in 3-D numerical modeling. I will
discuss particular requirements for realistic numerical modeling of solar magnetohydrodynamics andoutline the primary requirements for further progress, in particular in the direction of chromosphericmodeling.

P10

Magnetic Helicity, Magnetic Energy, and EUV Variability
Yasushi Sakamoto
Department of Astronomy, University of Tokyo
It is essential to accurately measure three-dimensional magnetic åeld and three-dimensional velocityåeld on the photosphere in order to estimate energy and helicity çux to the corona. We employ thevector magnetograms of Advanced Stokes Polarimeter (ASP) for three-dimensional magnetic åelds.
Velocity tangential to the solar surface is extracted from the magnetograms of SOHO/MDI by local
correlation tracking technique for longitudinal magnetic images. In order to obtain the velocity normal
to the solar surface we must select the most suitable methodology from three diãerent procedures,
namely, Dopplergram of SOHO/MDI, Dopplergram of ASP, and the inversion of induction equation
method developed by Kusano et al. We select the inversion method in our study but we will also
discuss the discrepancies found in the comparison of these procedures. With these data of magneticåelds and velocity åelds we estimate the rate of magnetic helicity/energy injection rate due to shear
motion eãect and due to çux emergence eãect separately for several active regions.
We calculate a degree of variability of EUV emission observed by SOHO/EIT. First we make thetime dependent proåle of EUV intensity averaged over the spatial domain of an active region. Thenthe standard deviation of this proåle divided by the mean is calculated as the degree of variability.
We compare the magnetic helicity and energy injected into the corona above active regions with thedegree of variability of EUV and ånd out that the magnetic helicity supplied by the photosphericshear motion has a correlation with the degree of variability of EUV.

31

Oral

The Magnetism of the Very Quiet Sun
J. Sanchez Almeida
Instituto de Astroåsica de Canarias
Most of the solar surface appears non-magnetic when it is observed in routine synoptic magnetograms.
However, magnetic åelds are detected almost everywhere, also in internetwork (IN) regions, when thepolarimetric sensitivity and the angular resolution exceed a threshold. These magnetic åelds are now
accessible to many existing spectro-polarimeters, and they will be easy to observe with Solar-B. They
cover much of the solar surface and, therefore, they may be carrying most of the unsigned magnetic çuxand energy existing on the solar surface at any given time. This makes the IN potentially important tounderstand the global magnetic properties of the Sun (solar dynamo, coronal heating, sources of thesolar wind, ...). I will review the main observational properties of these åelds, as deduced from recent
measurements (magnetic åeld strength and inclination, magnetic çux content, etc.). In addition, I
will mention the physical mechanisms put forward to explain their origins, with pros and cons.

P21

Statistical Study of Hard X-ray Footpoint Region Observed with YOHKOH
Jun Sato
Solar-Terrestrial Environment Laboratory, Nagoya University
We show some characteristics of hard X-ray footpoints derived from The YOHKOH Flare Image
Catalogue covering the whole YOHKOH mission period (1991/08{2001/12). We mainly revealed thatA) the hard X-ray emission comes from above the Hã emitting region and accelerated electrons lose
their energy (10{100 keV) within about 1000 km length, and that B) the most of hard X-ray footpoint
sources show a broken power-law spectrum with very hard spectrum in the low energy range (20{30keV), suggesting the existence of cut oã energy of accelerated electrons around 20{30 keV.

32

Oral

SOT Local-Helioseismology Programme
Takashi Sekii
National Astronomical Observatory of Japan
Local helioseismology is proving to be a powerful tool in revealing small-scale çow and inhomogeneity
in subsurface layers. The Solar Optical Telescope (SOT) is capable of producing very high-resolution
Dopplergrams that can be used for this new method of helioseismology. I will review what little weknow about small-scale waveåeld and discuss what can be learned with SOT local helioseismology, as
well as what should be done for a successful programme.

Oral

A Pumping-Up Mechanism of Mass and Energy
from the Photosphere into the Upper Atmosphere
Kiyoto Shibasaki
Nobeyama Radio Observatory, National Astronomical Observatory of JapanA new mechanism is proposed to pump up mass and energy from the photosphere into the upper
atmosphere; the chromosphere, the transition region and the corona. Recent high spatial resolution
and high cadence observations at various temperature ranges revealed extremely dynamical features in
the atmosphere such as ejections, çows and heating. Most of these activities have been attributed tomagnetic reconnection of various scales. Dynamical features of plasmas have been interpreted as jets
caused by reconnected magnetic tension force and evaporation or ablation due to high temperatureas the result of magnetic reconnection. However, most of the observational evidences of magnetic
reconnection are indirect. In this work, we propose to apply high-beta disruption as the cause of these
activities. Curved magnetic loops with high-beta plasma inside and/or high velocity çow are unstable
at their outer boundary surface. Localized interchange instability called \ballooning instability" candevelop into non-linear phase and eventually disrupt the loop and fed the plasma into the surrounding
magnetic structures. Starting from the photospheric granulation size up to Coronal Mass Ejection
size, this mechanism can act as the converter of thermal and kinetic free energy, in the form of plasmaconånement and çow, into other forms such as plasma ejection, particle acceleration, and eventually
heating. Curved magnetic loops with enough plasma inside can pump up energy and mass into theupper atmosphere.

33

Oral

MHD Shock Waves in the Corona
Kazunari Shibata
Kwasan Observatory, Kyoto University
We review the recent research of MHD shock waves and related phenomena in the corona, withemphasis on the progress in the understanding of Moreton waves, for which late Professor Uchidaestablished in early 1970's that they are chromospheric manifestations of coronal MHD shock waves.
Table of Contents:
1. Introduction
2. Early Observations
3. Uchida Theory
4. New Observations(a) EIT waves(b) X-ray waves(c) Moreton waves(d) Radio observations
5. Theory and Simulations
6. Summary

P26

Slow Shock Formation and Plasmoid Structure in Fast Magnetic Reconnection
Tohru Shimizu
Department of Computer Science, Ehime University
Fluid element trajectories based on magnetohydrodynamic (MHD) simulations are studied to analyze
the relation between slow shock formation and plasmoid structure in the fast magnetic reconnection,
including supersonic or subsonic expansion/acceleration process in the plasma. When the fast magnetic reconnection is well developed, either supersonic or subsonic expansion/acceleration process ofthe plasma occurs in front of the plasmoid, which additionally accelerates the reconnection jets generated by slow shocks. In particular, when the jet is supersonic, strong plasma heating and compression
are observed in the plasmoid. According to the study of the çuid element trajectories, another pair ofslow shocks is formed around the plasmoid, which is separated from a pair of slow shocks located in
the upstream of the fast reconnection jet. In addition, thin high speed jet layers are observed insideof the plasmoid.

34

P16

Derivation of DEM Distribution Using YOHKOH/Soft X-ray Telescope
Masumi Shimojo
Nobeyama Radio Observatory, National Astronomical Observatory of Japan
It is very important for understanding of coronal heating to derive the Diãerential Emission Measure(DEM) distribution. However, it is diécult to know DEM distribution using X-ray images sincemost X-ray images are taken using some broad-band X-ray ålters, like YOHKOH/SXT and SOLARB/XRT. We try to derive the DEM distribution using YOHKOH/SXT images and the WithbroeSylwester method (Withbroe 1975; Sylwester et al. 1980). In this paper, we present the preliminary
results of the DEM analysis for an active region which was observed by SXT using åve diãerent X-ray
ålters. The temperature range of the DEMs is from 2 MK to 20 MK. The DEMs of the quiet loops
in the center of the active region show the power-law distribution with an index of 4{5. We also
examine the time evolutions of DEMs at the brightening loops and found that the index of the DEM
distributions slightly decreases during the loop brightening.

P30

XRT and EIS Observations of Evidence of Magnetic Reconnection
D. Shiota, H. Isobe, D.H. Brooks, P.F. Chen, and K. Shibata
Kwasan and Hida Observatories, Kyoto University
Magnetic reconnection is widely believed to play an important role in various solar activities suchas solar çares. However, we could ånd only indirect evidence of reconnection, such as cusp-shaped
loop, the motion of çare ribbons, and so on. Also, the theory of magnetic reconnection has not been
established. Imaging and spectroscopic observations of reconnection-associated çows by Solar-B will
improve our understanding of the basic process of magnetic reconnection in the solar atmosphere.
We performed 2.5-dimensional magnetohydrodynamic simulations of a coronal mass ejection (CME)associated with a giant arcade with a model of magnetic reconnection coupled with heat conduction.
Based on the numerical results, we calculate the theoretical images taken by X-Ray Telescope and
EUV Imaging Spectrometer, and predict the observation of evidence of magnetic reconnection suchas inçow, outçow and shock structures. Furthermore, we discuss `dimming' mechanism at CME site.

35

Oral

Spectroscopic Study of Steady Coronal Structures| Line Width Variations with Height of Fe x{xiv Lines |Jagdev Singh1;2 , Takashi Sakurai1 , and Kiyoshi Ichimoto1(1) National Astronomical Observatory of Japan(2) Indian Institute of Astrophysics, Bangalore
We have obtained spectrographic observations of several steady coronal structures at the limb overlying
the sunspot regions on several days, simultaneously in the following combinations of emission lines:(1) Fe xiv (5303 óA) and Fe x (6374 óA), (2) Fe x (6374 óA) and Fe xiii (10747 ó
A and 10798 óA),óó
and (3) Fe x (6374 A) and Fe xi (7892 A). The line-width, intensity and line-of-sight velocity for all
the lines were computed using Gaussian åts to the observed line proåles at each location of 4 Ç 4arcsec of the observed coronal regions. The line-width measurements indicate that in steady coronal
structures the FWHM of the 6374 ó
A line increases with height above the limb with an average valueóof 1.02 mA per arcsec. Whereas the FWHM of the 5303 ó
A line decreases with the most frequent valueof Ä0:66 mó
A per arcsec. The FWHM of the 7892 ó
A and 10747 ó
A lines increases at a rate of 0.55
ó per arcsec respectively. These values are inversely correlated with the corresponding
and 0.29 mA
values of ionization temperature for these emission lines. We ånd that FWHM of emission lines incoronal structures increases with height if the associated ionization temperature is less than 1.7 MK,
with gradient depending upon the ionization temperature of the line, while the FWHM decreases withheight for lines whose ionization temperature is greater than 1.7 MK. It implies that it may not always
be possible to interpret the observed increase in FWHM with height in terms of an increase in the
non-thermal velocity.

Oral

Small Scale Solar Magnetic Fields
Sami K. Solanki and Manfred Sch°
usslerMax Planck Institut f°
ur Aeronomie
Most of the magnetic çux passing through the solar surface is concentrated into small magnetic
structures, many of them below the best current spatial resolution. The structure and physics of small
scale magnetic åelds in the solar photosphere is discussed and current knowledge of their properties
is reviewed. An overview is given on both observational results and the results of recent 3-D non-greyradiation MHD simulations.

36

P31

Tether-Cutting Energetics of a Quiet Region Prominence Eruption
Alphonse C. Sterling
UAT/NASA/MSFC/JAXA
We study the morphology and energetics of a slowly-evolving quiet region prominence eruption occurring on 1999 February 8{9 in the solar north polar crown region, using Fe xv EUV 284 ó
A data fromthe EUV Imaging Telescope (EIT) on SOHO and soft X-ray data from the soft X-ray telescope (SXT)
on Yohkoh. After rising at approximately 1 km/s for about six hours, the prominence accelerates toa velocity of approximately 10 km/s leaving behind EUV and soft X-ray loop arcades of a weak çarein its source region. Intensity dimmings occur in the eruption region cospatially in EUV and soft
X-rays, indicating that the dimmings result from a depletion of material. Over the årst two hoursof the prominence's rapid rise, çare-like brightenings occur beneath the rising prominence which may
correspond to \tether cutting" magnetic reconnection. These brightenings have heating requirementsof up to order 1028 {1029 ergs, and this is comparable to the mechanical energy required for the risingprominence over the same time period. If the ratio of mechanical energy to heating energy remains
constant through the early phase of the eruption, then we infer that coronal signatures for the tether
cutting may not be apparent at or shortly after the start of the faster-rise phase of the prominence inthis or similar low-energy eruptions, since the plasma-heating energy levels would not exceed that of
the background corona. Our åndings have strong implications for the correct use of observations intesting theoretical ideas for the onset of solar eruptions.

P35

Observation of Two Diãerent Types of CMEs
Isao Suzuki1 and Yutaka Uchida2;y(1) Graduate University for Advanced Studies, National Astronomical Observatory of Japan(2) Science University of Tokyo
Since 1980s, it has been discussed that CMEs are either planar loop-like(two-dimensional) or bubblelike (three-dimensional) structures. Although loop-like conågurations were sometimes mentioned,
many researchers seem to think that all of them are bubble-like. We claim, however, that there are atleast two diãerent types (not only one) among CMEs. One is the loop-type CME (LCME), and theother is the blast-associated CME (BCME).
An LCME has two distant foot-points åxed on the solar surface, and is associated with an arcadeçare that has occurred somewhere between these foot-points. LCME's have the following characteristics: (1) They sometimes have a frontal loop, a cavity, and a core which is the gas moving with arising dark ålament. (2) They have two åxed foot-points. (3) Some of them have been found to have
loop structures connecting the çare region and the locations of the pre-çare foot-points. (4) They
accelerate outwards: The acceleration is larger when they have a core. (5) The density enhancement
over the normal corona is 10{20 %.
A BCME, more popularly known as a halo-type CME, has a dome-like shape propagating outwards
from the çare, and we consider a BCME to be associated with the çare blast wave. BCMEs havethe following characteristics: (1) They are associated with Moreton waves and EIT waves. (2) They
propagate at a roughly constant velocity. (3) The density enhancement of this type is a few percent,much lower than that of LCMEs.
ydeceased 2002 August 17
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Coronal Heating and Acceleration of the Fast/Slow Solar Windby Fast/Slow MHD Waves
Takeru Suzuki
Department of Physics, Kyoto University
We investigate coronal heating and solar wind acceleration in the open-åeld region by dissipation of
fast and slow MHD waves through the MHD shocks, focusing on an interpretation of the diãerence
between the fast solar wind and the slow solar wind in the solar minimum activity phase.
Linearly polarized Alfvì
en (or equivalently fast-mode MHD) waves and acoustic (slow-mode MHD)
waves traveling upward along the magnetic åeld line eventually form fast switch-on shock trains andhydrodynamical shock trains (N-waves), respectively, to heat the coronal plasma. The dissipation of
the slow waves is rapid and eãective in heating of the lower corona to increase the density at thecoronal base. As a result, it plays an important role in the formation of the dense slow-solar wind.
On the other hand, the fast waves can carry a sizable energy to the higher level and play importantroles in heating of the upper corona and acceleration of the fast-solar wind. Variations of the wave
amplitude show a large diãerence in the fast wind and the slow wind even if the same wave periods
are adopted. Observation of propagating wave motions in the fast and slow solar wind region can give
constraints on our modeling.

Oral

Coronal Heating with Sweet-Parker Pico-Flares
Saku Tsuneta1 and Yukio Katsukawa2(1) National Astronomical Observatory of Japan(2) Department of Astronomy, University of Tokyo
Katsukawa and Tsuneta (ApJ, 2001) and Katsukawa (PASJ, 2003) found an excess çuctuation in soft
X-rays coming from active regions, and proposed that the çuctuation is attributed to ubiquitous tiny
bursts. They estimated the energy range of individual bursts to be 1020Ä 22 erg/event. If the energy ofan individual burst is 1020 erg, 106 events would occur in an active region per second. There appears
to be a big desert, the void in which no burst occurs for 6 orders of magnitude in energy from the picoçare range to the micro-çare range, indicating that a separate physical mechanism is responsible forthe pico-çares. We propose that pico-çares are due to Sweet-Parker reconnection, which is presumably
easier to occur than the Petschek reconnection responsible for larger çares. Because of its ubiquity,pico-çare reconnection consumes coronal magnetic energy in a time scale of a month. We point out thecritical importance of high-cadence, high throughput, and high-resolution observations with Solar-B
XRT.

38

P17

The Features of Solar Telescopes at the Hida Observatory
and the Possibilities of Coordinated Observations with Solar-B
S. UeNo, S. Nagata, R. Kitai, and H. Kurokawa
Hida Observatory, Kyoto University
At the Hida observatory, two characteristic solar telescopes, Domeless Solar Telescope (DST) and
Flare Monitoring Telescope (FMT), have been worked at multiple observations for studying on solar
active phenomena, solar fundamental structures and large scale phenomena which aãect interplanetaryenvironment. In addition, an important new telescope, Solar Magnetic Activity Researching Telescope(SMART), was built further in 2003. It is designed so that the chromosphere image of Hã, the vector
magnetogram and the photosphere image of continuum light of the whole solar disk can be acquiredwith the highest spatial resolution in the world. In this paper, we introduce features and solarphysicalpurposes of these three telescopes, focusing on SMART, and propose about possibilities of coordinatedobservations with Solar-B.

P38

Precipitation Diãusion Model of Solar Wind for Sky Brightness Variation
W. Unno1 , M. Yuasa2 , and H. Shibahashi3(1) Senjikan Institute of Future Study, Kichijoji, Tokyo(2) Institute for Science and Technology, Kinki University, Higashi-Osaka(3) Department of Astronomy, University of Tokyo
The solar-cycle sky brightness variation discovered by Sakurai is interpreted in terms of the precipitation diãusion model of solar-wind particles. Implication in the solar-cycle global warming is also
discussed.

39

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Nanoçare Heating of the Corona
G. Vekstein1;2 , Y. Katsukawa1 , and S. Tsuneta1(1) National Astronomical Observatory of Japan(2) UMIST, Manchester
If mechanism responsible for creating hot solar corona is a magnetic one, the underlying heating eventsare likely to be highly fragmented, both spatialy and temporarily. Therefore, heating by nanoçares,
where these features are naturally present, looks like an appealing scenario. Here we discuss recent
progress, both theoretical and observational, in revealing possible signatures of the nanoçare heating.
The emphasis is on probing nanoçares with variability in the coronal X-ray emission. The future
progress in this study envisaged with the Solar-B mission is also discussed.

Oral

A Weak Component of Solar Magnetism
Jingxiu Wang
National Astronomical Observatories, Chinese Academy of Sciences
Solar intranetwork (IN) magnetic elements seem to represent a weak component of solar magnetism,
which is intrinsically distinct from network (NT) magnetic åeld. They are in fast emergence, migration,interaction and disappearance. Their lifetime is approximately 2 hours. They not only contribute hugeamount of magnetic çux, but also continuously interact with stronger network åeld, resulting many
types of activity on the quiet Sun. The interaction between IN and NT åelds at strong network
boundaries appears to be the key element in coronal heating and solar wind acceleration. Solar-B
will be the ideal tool for quantitative measurements of this weak component of solar magnetism. To
spatially resolve these weak åeld elements, the sensitivity of Solar-B magnetograph becomes a decisive
factor.

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P37

Interplanetary Flux Ropes and their Coronal Counterparts
T. Watanabe1 , Y. Namiki1 , H. Adachi2 , K. Marubashi3 , and S. Watari3(1) Department of Environmental Sciences, Ibaraki University(2) Department of Aeronautics and Astronautics, Tokai University(3) Communications Research Laboratory
We study coronal signatures of interplanetary çux ropes (magnetic clouds) which produce high magnetospheric activities. Our provisional study of interplanetary çux ropes observed near the Earthduring the ascending phase of the Solar Cycle 23 (1997{1998) shows a tendency that çux ropes withhigh inclination with respect to the ecliptic plane were observed during the high solar-activity phase.
Since the large-scale coronal current sheet on the source surface warps extensively during the highsolar activity phase, a close connection between the current sheet and interplanetary çux ropes issuggested. Detailed analysis of coronal images taken by Yohkoh/SXT and SOHO/EIT shows that
eruption of large-scale trans-equatorial loops connecting active regions in the opposite magnetic hemisphere initiates CME activity and that the inclination of the associated interplanetary çux rope issimilar to that of the heliospheric current sheet situated above the erupting coronal loops.

OralElectron Densities of High-Temperature Coronal Loops
Tetsuya Watanabe
National Astronomical Observatory of Japan
Yohkoh has revealed the existence of persistent high-temperature plasmas in solar active regions where
major çare activity takes place. Density at the energy release site for coronal heating determines the
eéciency of magnetic heating, and hence the heating energy çux.
Temperatures and densities of solar (and stellar) çares at the pre-çare states are compiled. Pre-çare
conditions are basically derived from the data taken with the same instruments several tens of minutes
before the onset of the impulsive phase of subsequent çares. It is found that the temperature increase
from the preçare to çare states is only Ålog T = 0.2, and that density and çux increases are roughly
independent of the çare thermal energy. Namely large çares take place at the coronal loops where
both temperatures and densities are already high.
Several line pairs exist in the EIS observing wavelengths, which are suitable for plasma density
diagnostics, covering wider temperature ranges. Combining with the emission measure information,\diãerential" ålling factors will reveal the fundamental structures of coronal loops proceeding to abrupt
magnetic activity.

41

P4

Nonlinear Force-Free Magnetic Field Conågurations
M.S. Wheatland
School of Physics, University of Sydney
A method for calculating nonlinear force-free magnetic åeld conågurations based on a Grad and Rubin
type current-åeld iteration procedure is being developed. Goals include the investigation of energies ofcoronal magnetic åelds for diãerent boundary conditions, and eventually, the reconstruction of coronalåelds based on vector magnetograph data. In this poster the methodology is presented, and initialtest cases are shown.

P9

Magnetic Helicity Injection and Sigmoidal Coronal Loops
Tetsuya Yamamoto1 , Takashi Sakurai2 , Kanya Kusano3 , and Takaaki Yokoyama4(1) Department of Astronomy, University of Tokyo(2) National Astronomical Observatory of Japan(3) Graduate School of Advanced Sciences of Matter, Hiroshima University(4) Department of Earth and Planetary Science, University of Tokyo
Sigmoidal loops are believed to be closely associated with çares, coronal dimming and coronal massejections. Sigmoidal loops look more twisted than ordinary coronal loops. Therefore, they may havemore free energy and may cause explosive phenomena. However, the sigmoidal loops are deåned
from morphology, and little is known about their physical parameters. Recently Kusano et al. (2002)
proposed how to quantitatively evaluate the magnetic helicity injection. We adopted their method
and studied the evolution of sigmoidal active regions with emphasis on the magnetic helicity injection.
Examples of sigmoidal loops were listed in Canåeld et al. (1999). We used the vector magnetograms
obtained with the Solar Flare Telescope of NAOJ and SOHO/MDI magnetograms to calculate themagnetic helicity injection. Three sigmoidal and two ordinary active regions were selected from thelist of Canåeld et al. (1999), which had good data coverage. We found larger (but not impulsive)
helicity injection in sigmoidal active regions than in ordinary active regions. This may be a feature
distinguishing the sigmoidal regions from ordinary regions. SXT images tend to show higher X-ray
intensities where the helicity injection is larger than the surroundings.

42

P13

Macrospicules, Coronal Heating, and Solar-B
Yohei Yamauchi1 , Ronald L. Moore2 , Steven T. Suess2 , Haimin Wang3 , and Takashi Sakurai4(1) NASA/MSFC/NRC(2) NASA/MSFC/NSSTC(3) NJIT/BBSO(4) National Astronomical Observatory of Japan
Measurements of the high-speed polar solar wind by Ulysses have shown the wind to carry some ånescale structures which have magnetic switchbacks caused by large-amplitude Alfvì
en waves. The lateralspan of these magnetic switchbacks, translated back to the Sun, is of the scale of the lanes and cells of
the magnetic network in which the open magnetic åeld of the polar coronal hole and polar solar wind
are rooted. This suggests that the magnetic switchbacks might be formed from network-scale magnetic
loops that erupt into the corona and then undergo reconnection with the open åeld. This possibility
motivated us to undertake the study reported here of the structure of Hã macrospicules observed at
the limb in polar coronal holes, to determine whether a signiåcant fraction of these eruptions appears
to be erupting loops. From a search of the polar coronal holes in 6 days of image-processed fulldisk Hã movies from Big Bear Solar Observatory, we found a total of 35 macrospicules. 15 out of
35 events were in the form of an erupting loop, 17 were in the form of a single-column spiked jet,and 3 events were unclassiåable. The erupting-loop macrospicules are appropriate for producing themagnetic switchbacks in the polar wind. The spiked-jet macrospicules show the appropriate structureand evolution to be driven by reconnection between network-scale closed åeld (a network bipole) andthe open åeld rooted against the closed åeld. This evidence for reconnection in a large fraction of ourmacrospicules supports models in which the coronal heating and solar wind acceleration in coronalholes are driven by explosive reconnection events seated in the network (e.g., Axford and McKenzie
1992, 1997; Fisk et al. 1999; Falconer et al. 2003). We believe that the vector magnetograph on theforthcoming Solar-B mission will provide critical clues to the mechanisms of coronal heating and solar
wind acceleration by detecting magnetic activities at the base of macrospicules in the network andspicules rooted in the edges of the network çux clumps.

43

P32

Association of Coronal Mass Ejections and Metric Type II Radio Bursts
with Impulsive Solar Energetic Particle Events
S. Yashiro1 , N. Gopalswamy2 , E.W. Cliver3 , D.V. Reames2 , M.L. Kaiser2 , and R.A. Howard4(1) The Catholic University of America, Washington, D.C.
(2) NASA Goddard Space Flight Center(3) Air Force Research Laboratory, Hanscom AFB, Massachusetts(4) Naval Research Laboratory
The impulsive solar energetic particle (SEP) events, known as 3 He-rich (Z-rich) events, are typicallyshort-lived and are small compared to the large gradual SEPs. There is a consensus that large
gradual SEPs are associated with fast coronal mass ejections (CMEs), but it was thought that the
CME association for the impulsive SEPs is not important. However, Kahler et al. (2001) foundthat an impulsive SEP event on 2000 May 1 was associated with a fast narrow CME. Additionally,
Gopalswamy et al. (2003) reported that an impulsive SEP event was associated with a fast andwide CME as in large SEP events. We identiåed 38 impulsive SEP events using the Wind/EPACT
instrument and investigated their association with coronal mass ejections (CMEs) and type II radio
bursts. We found that (1) at least 27{37 % of impulsive SEP events were associated with CMEs, (2)Only 8{13 % were associated with type II radio bursts. The statistical properties of the associatedCMEs were investigated and compared to those of all CMEs and CMEs associated with large gradual
SEP events. The CMEs associated with impulsive SEP events were signiåcantly slower (median speedof 613 km/s) and narrower (49é) than those of CMEs associated with large gradual SEP events (1336
km/s, 360é), but faster than the average CMEs (402 km/s).
References
Gopalswamy, N. et al., Adv. Space. Res., in press., 2003.
Kahler, S. W. et al., ApJ 562, 558{565, 2001.

P27

MHD Simulations of Magnetic Reconnection with Finite-Amplitude Fluctuations
Takaaki Yokoyama
Department of Earth and Planetary Science, University of Tokyo
The dissipation mechanism at the magnetic X-point of the reconnection process in solar çares isstudied. Although the Petschek model is a promising mechanism to explain the rapid energy release,
the estimated size of the diãusion region in this model would be extremely small, i.e. less thancenti-meter if we adopt the Spitzer-type resistivity. Even the scale size in which various microscopic
processes become eécient is still 10 meter or so, which is much less than the typical size of a çare. So
there must be a meso-size scale where the MHD turbulence plays a role. In order to study the eãect
of the MHD turbulence on the magnetic reconnection, we are performing a series of MHD simulationsof magnetic reconnection with ånite amplitude çuctuations. A temporal evolution of a simple current
sheet with almost uniform resistivity is investigated after imposing a ånite-amplitude çuctuations(whose strength is approximately Alfvì
en speed) all over the computation domain. Multi-dimensional
simulations showed no eãective enhancement in the energy release rate.

44

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Large-Scale Solar Coronal Dynamics Observed by SOHO/EIT
Andrei Zhukov
Royal Observatory of Belgium
A review of coronal observations made by the SOHO/EIT is presented. A particular emphasis is puton the Coronal Mass Ejections initiation process, with EUV dimmings and EIT waves being the main
CME signatures in the low corona. The observed characteristics and morphologies of EIT waves/EUV
dimmings are described and their basic properties are summarized. It appears that EIT waves canbe regarded as a bimodal phenomenon. The pure wave mode represents a wave-like propagating
disturbance; the eruptive mode is a propagation of a dimming as a result of magnetic åeld opening
during the CME lifting. It is shown that at present it is diécult to reconcile all the observational
facts into a coherent physical model. Some implications for the Solar-B mission will be discussed.

45