E-Print Archive

There are 3775 abstracts currently viewable.


Search:

Advanced Search
Options
Main Page Add New E-Print Submitter
Information
Feedback
News Help/FAQ About Preferences
Manage Key Phrase
Notification
Electric-Current Neutralization, Magnetic Shear, and Eruptive Activity in Solar Active Regions  

Yang Liu   Submitted: 2017-08-14 18:43

The physical conditions that determine whether or not solar active regions (ARs) produce strong flares and coronal mass ejections (CMEs) are not yet well understood. Here we investigate the association between electric-current neutralization, magnetic shear along polarity inversion lines (PILs), and eruptive activity in four ARs; two emerging and two well-developed ones. We find that the CME-producing ARs are characterized by a strongly non-neutralized total current, while the total current in the ARs that did not produce CMEs is almost perfectly neutralized. The difference in the PIL-shear between these two groups is much less pronounced, which suggests that the degree of current-neutralization may serve as a better proxy for assessing the ability of ARs to produce CMEs.

Authors: Yang Liu, Xudong Sun, Tibor Török, Viacheslav S. Titov, James E. Leake
Projects: SDO-HMI

Publication Status: ApJL accepted
Last Modified: 2017-08-15 17:09
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Vector Magnetic Field Synoptic Charts from the Helioseismic and Magnetic Imager (HMI)  

Yang Liu   Submitted: 2017-01-17 11:24

Vector magnetic field synoptic charts from the Helioseismic and Magnetic Imager (HMI) are now available for each Carrington Rotation (CR) starting from CR 2097 in May 2010. Synoptic charts are produced using 720-second cadence full-disk vector magnetograms remapped to Carrington coordinates. The vector field is derived from the Stokes parameters (I, Q, U, V) using a Milne-Eddington based inversion model. The 180° azimuth ambiguity is resolved using the Minimum Energy algorithm for pixels in active regions and for strong-field pixels (the field is greater than about 150 G) in quiet Sun regions. Three other methods are used for the rest of the pixels: the potential-field method, the radial-acute angle method, and the random method. The vector field synoptic charts computed using these three disambiguation methods are evaluated. The noise in the three components of vector magnetic field is generally much higher in the potential-field method charts. The component noise levels are significantly different in the radial-acute charts. However, the noise levels in the random-method charts are lower and comparable. The assumptions used in the potential-field and radial-acute methods to disambiguate the weak transverse field introduce bias that propagates differently into the three vector-field components, leading to unreasonable pattern and artifacts, whereas the random method appears not to introduce any systematic bias. The computed current sheet on the source surface, computed using the potential-field source-surface model applied to random-method charts, agrees with the best solution (the result computed from the synoptic charts with the minimum energy algorithm applied to each and every pixel in the vector magnetograms) much better than the other two. Differences in the synoptic charts determined with the best method and the random method are much smaller than those from the best method and the other two. This comparison indicates that the random method is better for vector field synoptic maps computed from near-central meridian data. Thus, the vector field synoptic charts provided by the Joint Science Operations Center (JSOC) are produced with the random method.

Authors: Yang Liu, J. T. Hoeksema, Xudong Sun, Keiji Hayashi
Projects: SDO-HMI

Publication Status: Solar Physics, accepted.
Last Modified: 2017-01-18 11:12
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Sunspot Rotation and the M-class Flare in Solar Active Region NOAA 11158  

Yang Liu   Submitted: 2015-08-08 09:31

In this paper, we measure the rotation of a sunspot in solar active region NOAA 11158 (Solar Target Identifier SOL2011-02-15) that was associated with anM-class flare. The flare occurred when the rotation rate of the sunspot reached its maximum. We further calculate the energy in the corona produced by the sunspot rotation. The energy accumulated in the corona before the flare reached 5.5? 1032 erg, sufficient for energy requirements for a moderately big solar eruption. This suggests that sunspot rotation, which is often observed in solar active regions, is an effective mechanism for building up magnetic energy in the corona.

Authors: Alexander Li, Yang Liu
Projects: SDO-HMI

Publication Status: Solar Physics Accepted
Last Modified: 2015-08-10 11:13
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Magnetic Helicity in Emerging Solar Active Regions  

Yang Liu   Submitted: 2014-02-21 15:41

Using vector magnetic field data from the Helioseismic and MagneticImager (HMI) instrument aboard the Solar Dynamics Observatory (SDO),we study magnetic helicity injection into the corona in emergingactive regions and examine the hemispheric helicity rule. In everyregion studied, photospheric shearing motion contributes most of thehelicity accumulated in the corona. In a sample of 28 emerging activeregions, 17 active regions follow the hemisphere rule (61% ± 18% at a95% confidence interval). Magnetic helicity and twist in 25 activeregions (89% ± 11%) have the same sign. The maximum magnetic twist,which depends on the size of an active region, is inferred in a sampleof 23 emerging active regions with a bipolar magnetic fieldconfiguration.Coronal holes are regions on the Sun's surface that mapthe footprints of open magnetic field lines. We have developed anautomated routine to detect and track boundaries of long-lived coronalholes using full-disk extreme-ultraviolet (EUV) images obtained bySOHO

Authors: Y. Liu, J. T. Hoeksema, M. Bobra, K. Hayashi, P. W. Schuck, X. Sun
Projects: SDO-HMI

Publication Status: ApJ., accepted.
Last Modified: 2014-02-24 13:04
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Test of the Hemisphere Rule of Magnetic Twist in Solar Active Regions Using the Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Data  

Yang Liu   Submitted: 2014-01-25 12:01

Magnetic twist in solar active regions has been found to have a hemispheric preference in sign (hemisphere rule): negative in the northern hemisphere and positive in the southern. The preference reported in previous studies ranges greatly, from sim 58% to 82%. In this study, we examine this hemispheric preference using vector magnetic field data taken by HMI and find that 75% pm 7% of 151 active regions studied obey the hemisphere rule, well within the preference range in previous studies. If the sample is divided into two groups,-,active regions having magnetic twist and writhe of the same sign and having opposite signs,-,the strength of the hemispheric preference differs substantially: ( 64% pm 11% ) for the former group and ( 87% pm 8% ) for the latter. This difference becomes even more significant in a sub-sample of 82 active regions having a simple bipole magnetic configuration: ( 56% pm 16% ) for the active regions having the same signs of twist and writhe, and 93% with lower and upper confidence bounds of 80% and 98% for the active regions having the opposite signs. The error reported here is a 95% confidence interval. This may suggest that, prior to emergence of magnetic tubes, either the sign of twist does not have a hemispheric preference or the twist is relatively weak.

Authors: Y. Liu, J. T. Hoeksema, X. Sun
Projects: SDO-HMI

Publication Status: ApJL accepted
Last Modified: 2014-01-28 12:39
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

A Note on Computation of Relative Magnetic Helicity Flux Across the Photosphere  

Yang Liu   Submitted: 2012-12-19 09:07

A number of investigations of the rate of relative magnetic helicity transport across the photosphere [ dH/dt|S ] have reported differences in the estimates computed from two different formulations of the relative-helicity flux density proxy [ GA ] and [ G_theta ]. There have been suggestions that [ G_theta ] is a more robust helicity-flux density proxy and that the differences in the estimates of [dH/dt|S ] are caused by biases in [ GA ], noise, and/or the boundary conditions. In this note, we prove that the differences are caused by the inconsistent choice of boundary conditions in the explicit or implicit Green?s function [ G (x, x′) ] used for computing [ GA ] and [ G_theta ] when comparing the helicity flux estimates based on [ GA ] and [ G_theta ]. When the boundary conditions in [ G ] are chosen consistetently, the two helicity-flux density proxies, [ GA ] and [ G_theta ], produce essentially identical results for the rate of helicity transport across the photosphere. They also yield essentially identical results for the rate of helicity transport of the shearing and advection terms separately. Using MHD simulation, HMI observational data, and Monte Carlo simulations of noise we show that this result is robust. Neither the shape of the active region, nor the shape of the boundary, nor data noise causes any difference in the rate of helicity transport computed via [ GA ] and [ G_theta ].

Authors: Yang Liu, Peter W. Schuck
Projects: SDO-HMI

Publication Status: Solar Physics, Accepted.
Last Modified: 2012-12-19 12:09
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Magnetic Energy and Helicity in Two Emerging Active Regions in the Sun  

Yang Liu   Submitted: 2012-10-31 11:33

The magnetic energy and relative magnetic helicity in two solar active regions AR 11072 and AR 11158 during their emergence are studied. They are computed by integrating over time, the energy- and relative helicity-fluxes across the photosphere. The fluxes consist of two components: one from photospheric tangential flows that shear and braid field lines (shear-term); the other from normal flows that advect magnetic flux into the corona (emergence-term). For these active regions (1) relative magnetic helicity in the active-region corona is mainly contributed by the shear-term; (2) helicity fluxes from emergence-term and shear-term have the same sign; (3) magnetic energy in the corona (including both potential energy and free energy) is mainly contributed by emergence-term; and (4) energy fluxes from emergence-term and shear-term evolved consistently in phase during the entire flux emergence course. We also examine the apparent tangential velocity derived by tracking field-line footpoints using a simple tracking method. It is found that this velocity is more consistent with tangential plasma velocity than with the flux transport velocity, which agrees with the conclusion in Schuck (2008).

Authors: Yang Liu, Peter W. Schuck
Projects: SDO-HMI

Publication Status: ApJ accepted
Last Modified: 2012-10-31 12:13
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Horizontal Flows in the Photosphere and Subphotosphere of Two Active Regions  

Yang Liu   Submitted: 2012-07-23 11:57

We compare horizontal flow fields in the photosphere and subphotosphere a layer of 0.5 Mm below the photosphere in two solar active regions: AR11084 and AR11158. AR11084 is a mature, simple active region without significant flaring activities, and AR11158 is a multipolar, complex active region with magnetic flux emerging during the period studied. Flows in the photosphere are derived by applying the method of Differential Affine Velocity Estimator for Vector Magnetograms (DAVE4VM) on HMI observed vector magnetic fields, and the subphotospheric flows are inferred by time ? distance helioseismology using HMI observed Doppergrams. Similar flow patterns are found for both layers for AR11084: inward flows in sunspot umbra and outward flows surrounding the sunspot. The boundary between the inward and outward flows, which is slightly different in the photosphere and the subphotosphere, is within the sunspot penumbra. The area having inward flows in the subphotosphere is larger than that in the photosphere. For AR11158, flows in these two layers show great similarities in some areas and significant differences in other areas. Both layers exhibit consistent outward flows in the areas surrounding sunspots. On the other hand, most well-documented flux-emergence-related flow features seen in the photosphere do not have their counterparts in the subphotosphere. This implies that the horizontal flows caused by flux emergence do not extend deeply into the subsurface.

Authors: Yang Liu, Junwei Zhao, Peter W. Schuck
Projects: SDO-HMI

Publication Status: Accepted by Solar Physics
Last Modified: 2012-07-24 11:02
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Comparison of Line-of-Sight Magnetograms Taken by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager and Solar and Heliospheric Observatory/Michelson Doppler Imager  

Yang Liu   Submitted: 2012-03-19 19:06

We compare line-of-sight magnetograms from the {it Helioseismic and Magnetic Imager} (HMI) onboard the {it Solar Dynamics Observatory} (SDO) and the {it Michelson Doppler Imager} (MDI) onboard the {it Solar and Heliospheric Observatory} (SOHO). The line-of-sight magnetic signal inferred from the calibrated MDI data is greater than that derived from the HMI data by a factor of 1.40. This factor varies somewhat with center-to-limb distance. An upper bound to the random noise for the 1primeprime resolution HMI 720-second magnetograms is 6.3 Mx cm-2, and 10.2 Mx cm-2 for the 45-second magnetograms. Virtually no {it p}-mode leakage is seen in the HMI magnetograms, but it is significant in the MDI magnetograms. 12-hour and 24-hour periodicities are detected in strong fields in the HMI magnetograms. The newly calibrated MDI full-disk magnetograms have been corrected for the zero-point offset and underestimation of the flux density. The noise is 26.4 Mx cm-2 for the MDI one-minute full-disk magnetograms and 16.2 Mx cm-2 for the five-minute full-disk magnetograms observed with four-arcsecond resolution. The variation of the noise over the Sun's disk found in MDI magnetograms is likely due to the different optical distortions in the left- and right-circular analyzers, which allows the granulation and {it p}-mode to leak in as noise. Saturation sometimes seen in sunspot umbrae in MDI magnetograms is caused by the low intensity and the limitation of the onboard computation. The noise in the HMI and MDI line-of-sight magnetic-field synoptic charts appears to be fairly uniform over the entire map. The noise is 2.3 Mx cm-2 for HMI charts and 5.0 Mx cm-2 for MDI charts. No evident periodicity is found in the HMI synoptic charts.

Authors: Y. Liu, J.T. Hoeksema, P.H. Scherrer, J. Schou, S. Couvidat, R.I. Bush, T.L.Duvall Jr, K. Hayashi, X. Sun, X. Zhao
Projects: None

Publication Status: Solar Physics, Accepted
Last Modified: 2012-03-20 10:33
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Magnetic Field Elements at High Latitude: Lifetime and Rotation Rate  

Yang Liu   Submitted: 2009-12-17 15:50

Using 1-minute cadence time-series full disk magnetograms taken by the SOHO/MDI, we have studied the magnetic field elements at high latitude (poleward of 65circ in latitude). It is found that an average lifetime of the magnetic field elements is 16.5 hours during solar minimum, much longer than that during solar maximum (7.3 hours). During solar minimum, number of the magnetic field elements with the dominant polarity is about 3 times as that of the opposite polarity elements. Their lifetime is 21.0 hours on average, longer than that of the opposite polarity elements (2.3 hours). It is also found that the lifetime of the magnetic field elements is related with their size, consistent with the magnetic field elements in the quiet sun at low latitude found by Hagenaar (1999). During solar maximum, the polar regions are equally occupied by magnetic field elements with both polarities, and their lifetimes are roughly the same on average. No evidence shows there is a correlation between the lifetime and size of the magnetic field elements. Using an image cross-correlation method, we also measure the solar rotation rate at high latitude, up to 85 degree in latitude. The rate is ( omega = 2.914 - 0.342 imes sin^2phi - 0.482 imes sin^4phi ) murad s-1 sidereal. It agrees with previous studies using the spectroscopic and image cross-correlation methods, and also agrees with the results using the element tracking method when the sample of the tracked magnetic field elements is large. The consistency of those results strongly suggests that this rate at high latitude is reliable.

Authors: Yang Liu, Junwei Zhao
Projects: None

Publication Status: Published in Solar Physics
Last Modified: 2009-12-21 12:28
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Subject will be restored when possible  

Yang Liu   Submitted: 2008-04-14 11:09

Using a Potential Field Source Surface model (PFSS), we study magnetic field overlying erupted filaments in solar active regions. The filaments studied here were reported to experience a kink instability or a torus instability. The torus instability leads to a full eruption, while the kink instability leads to a full eruption or a failed eruption. It is found that for full eruption the field decreases with height more quickly than that for failed eruption. A dividing line between full eruption and failed eruption is also found to be likely connected with the decay index {it n} of the horizontal potential field due to sources external of the filament ( (n=-d~log(Bex)/d~log(h) ), where h is height): the decay index of failed eruption tends to be smaller than that of full eruption. The difference of the decay indexes between full eruption and failed eruption is statistically significant. These are supportive of previous theoretical and numerical simulation results. Another significant difference is the field strength at low altitude: for failed eruption, the field strength is about a factor of 3 stronger than that for the full eruption. It suggests that the field strength at low altitude may be another factor in deciding whether or not a full eruption can take place. On the other hand, the decay index for the torus-instability full eruption events exhibits no trend to exceed the decay index for the kink-instability full eruption events on average, different from a suggestion derived from some MHD simulations. We discuss possible reasons that may cause this discrepancy.

Authors: Yang Liu
Projects: None

Publication Status: ApJL, accepted
Last Modified: 2008-09-23 21:10
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

A NOTE ON SATURATION SEEN IN THE MDI/SOHO MAGNETOGRAMS  

Yang Liu   Submitted: 2007-02-08 12:16

A type of saturation is sometimes seen in sunspot umbrae in SOHO/MDI magnetograms. In this paper, we present the underlying cause of such saturation. By using a set of MDI circular polarization filtergrams taken during an MDI line profile campaign observation, we derive the MDI magnetograms using two different approaches: the {it on-board data processing} and the {it ground data processing}, respectively. The algorithms for processing the data are the same, but the former is limited by a 15-bit lookup table. Saturation is clearly seen in the magnetogram from the {it on-board processing} simulation, which is comparable to an observed MDI magnetogram taken one and a half hours before the campaign data. We analyze the saturated pixels and examine the on-board numerical calculation method. We conclude that very low intensity in sunspot umbrae leads to a very low depth of the spectral line that becomes problematic when limited to the 15-bit on-board numerical treatment. This 15-bit on-board treatment of the values is the reason for the saturation seen in sunspot umbrae in MDI magnetogram. Although it is possible for a different type of saturation to occur when the combination of a strong magnetic field and high velocity moves the spectral line out of the effective sampling range, this saturation is not observed.

Authors: Y. Liu, A.A. Norton, P.H. Scherrer
Projects: None

Publication Status: Solar Physics, in press
Last Modified: 2007-02-09 12:04
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Halo Coronal Mass Ejections and Configuration of the Ambient Magnetic Fields  

Yang Liu   Submitted: 2006-12-06 10:29

In this study, we seek correlation between speed of the active region-related halo Coronal Mass Ejections (CMEs) and configuration of the ambient magnetic fields. Having studied 99 halo CMEs in the period from 2000 to 2004, we find that CMEs under the heliospheric current sheet are significantly slower than CMEs situated under unidirectional open field structures. The average speed of the former is 883 km s-1, while the latter is 1388 km s-1. The effect is not biased by the flare importance. This implies that the ambient magnetic field structure plays a role in determining speed of the halo CMEs.

Authors: Y. Liu
Projects: None

Publication Status: ApJL accepted
Last Modified: 2006-12-06 11:24
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Magnetic Structures of Solar Active Regions, Full Halo Coronal Mass Ejections, and Geomagnetic Storms  

Yang Liu   Submitted: 2006-06-16 10:44

We have analyzed 3 active regions to investigate the relationship between magnetic configurations of active regions and geomagnetic storms. Each active region was associated with multiple full halo coronal mass ejections (CMEs). This study demonstrates that, although full halo CMEs may originate from the same active region, it is not necessary for them to have similar geoeffectiveness, depending on the magnetic configurations actually involved in the corresponding flare activities. This implies that (1) the flares, CMEs and geomagnetic storms are closely related magnetically, as already suggested by many others, and (2) the occurrence of solar active region-related geomagnetic storms may be determined by the magnetic fields which are involved in the corresponding solar flares. These associations suggest ways to improve geomagnetic storm prediction.

Authors: Y. Liu, D. F. Webb, X. P. Zhao
Projects: None

Publication Status: ApJ in press 2006
Last Modified: 2006-06-16 11:07
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

The 2003 October-November Fast Halo Coronal Mass Ejections and the Large-Scale Magnetic Field Structures  

Yang Liu   Submitted: 2006-06-16 10:40

The coronal magnetic field, computed from synoptic maps of the magnetic field and a potential field source surface (PFSS) model, reveals special configurations related to the active regions that were associated with most, if not all, fast halo coronal mass ejections (CMEs) in 2003 October-November. It was shown that these active regions emerged in an open field area, produced a large open field area after emerging, or sat on a boundary of two open field areas with the same polarity. This type of boundary is also known as a ``plasma sheet.'' Such magnetic structures appear to be favorable for the propagation of the disturbance. MHD simulations were performed here to explore the behavior of the propagation of the disturbance against these special configurations of the background magnetic field. It is demonstrated that without the presence of open flux, the speed of the CMEs would have been only 78% of that with open flux present. It is also found that the CMEs from a heliospheric current sheet have a speed only 67% of the CMEs' speed from a plasma sheet, the source boundary with the same polarity.

Authors: Y. Liu, K. Hayashi
Projects: None

Publication Status: ApJ Volume 640, Issue 2, pp. 1135-1141.
Last Modified: 2006-06-16 10:40
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Tilt and α _best of major flare-producing active regions  

Yang Liu   Submitted: 2003-07-18 10:16

We surveyed 86 active regions in the years from 1996 to 2002 in the 23rd solar cycle that produced more than three major flares. We studied the systematic tilt angle with respect to the solar equator and the force-free parameter α m best of the magnetic field of the active regions, and we obtained the following results. (1) Only 46 (54%) of the active regions follow Joy's law. (2) 43 (50%) active regions obey the hemispheric helicity rule. (3) 56 (65%) have the same sign for the tilt and the α m best, and the tilt and the α m best of all 86 regions are positively correlated. (4) 33 (60%) of the 55 active regions which have an etagammadelta magnetic configuration show the same sign for the tilt and α m best. It is commonly believed that the sign of the tilt and α m best obtained in the photosphere can describe the sign of the twist and writhe of the flux tube rising from the convection zone. Therefore, the results above appear to support the kink hypothesis for active regions that the sign of the twist and writhe should be the same where a kink instability has developed (Linton, et al. 1999).

Authors: Lirong Tian, Y. Liu
Projects: None,Soho-MDI

Publication Status: A&Ap. Lett. (accepted)
Last Modified: 2003-07-18 10:16
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 


Key
Go to main E-Print pageGo to main E-Print page.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
Delete AbstractDelete abstract.

Abstracts by Author
Electric-Current Neutralization, Magnetic Shear, and Eruptive Activity in Solar Active Regions
Vector Magnetic Field Synoptic Charts from the Helioseismic and Magnetic Imager (HMI)
Sunspot Rotation and the M-class Flare in Solar Active Region NOAA 11158
Magnetic Helicity in Emerging Solar Active Regions
Test of the Hemisphere Rule of Magnetic Twist in Solar Active Regions Using the Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Data
A Note on Computation of Relative Magnetic Helicity Flux Across the Photosphere
Magnetic Energy and Helicity in Two Emerging Active Regions in the Sun
Horizontal Flows in the Photosphere and Subphotosphere of Two Active Regions
Comparison of Line-of-Sight Magnetograms Taken by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager and Solar and Heliospheric Observatory/Michelson Doppler Imager
Magnetic Field Elements at High Latitude: Lifetime and Rotation Rate
Subject will be restored when possible
A NOTE ON SATURATION SEEN IN THE MDI/SOHO MAGNETOGRAMS
Halo Coronal Mass Ejections and Configuration of the Ambient Magnetic Fields
Magnetic Structures of Solar Active Regions, Full Halo Coronal Mass Ejections, and Geomagnetic Storms
The 2003 October-November Fast Halo Coronal Mass Ejections and the Large-Scale Magnetic Field Structures
Tilt and alpha_best of major flare-producing active regions

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey



© 2003 Solar Physics Group - Montana State University