Head, Radio & Space Plasma Physics Group

Dear Dr Hoeksema:

In response to the message concerning the WSO data just received as part of the AGU SPA Newsletter, I am attaching for your reference a paper that acknowledges scientific use of the WSO data, as emphasised in your message. The data were used to provide background material that underpinned the interpretation of Cassini IMF data obtained during the approach to Saturn, as is indicated in the paper. We would wish to make similar use of the data in future as the Cassini mission unfolds into the rising phase of the next solar cycle.
May I take the opportunity of thanking you once again for the help you gave in providing these data to us.
Regards, Stan Cowley
------
Prof Stanley W H Cowley

Head, Radio & Space Plasma Physics Group

Department of Physics & Astronomy Tel: +44-116-223-1331
University of Leicester, Leicester LE1 7RH Fax: +44-116-252-3555
United Kingdom Sec: +44-116-252-3563

To Whom It May Concern:

I frequently use the data products of the Wilcox Solar Observatory in my research and strongly urge that the program continue. The coronal magnetic field maps at the source surface are particularly useful for relating solar wind features to the heliospheric current sheet, and several have appeared in my publications, most recently in Crooker and Webb (2006). This publication also features a section from one of the large-scale photospheric field maps.

Sincerely,
Nancy Crooker

Crooker, N. U., and D. F. Webb (2006), Remote sensing of the solar site of interchange reconnection associated with the May 1997 magnetic cloud, J. Geophys. Res., in press.

The data from WSO are the "gold" standard
for the long-term assessment of the large-scale
solar magnetic field. The accurate determination of
the zero-level is unique to WSO. WSO polar fields
have been (and will be for cycle 24) important for
the prediction of solar cycle strength [e.g. Svalgaard
et al. (2004) Geophysical Research Letters, Volume 32,
Issue 1, CiteID L01104]. The mean field signal is
still not well understood, but its long-term behavior is
probably important for the understanding of the sources
of the IMF [e.g. Kotov et al. Solar Physics, v. 209, Issue 2,
p. 233-245 (2002)]. The "saturation" factor problem is
also unresolved: The magnetic fields measured at each
observatory are all different, but for each observatory
a factor (or function) exists to make all measurements
agree. The cause of this is unknown. It is important to
let WSO operate at least until the end of cycle 24. At
that time, we may have enough data overlapping with
SOLIS that we can properly interprete the legacy of
WSO data back to 1976. The value of long-term
data is often degraded by termination of the observations
without sufficient overlap with newer data. The Greenwich
sunspot areas come to mind. ACRIM solar irradiance is
another example.

--
Leif Svalgaard

Date: Tue, 30 May 2006 11:39:34 -0700 (PDT)

From: Janet Luhmann <>

Reply-To: Janet Luhmann <>

Subject: CISM use of WSO

To:

Cc: , , ,

, , ,

Re: Response to SPA news item on uses of WSO

WSO is one of the primary solar magnetogram providers for

our solar/heliosphere modeling activities within CISM (the

Center for Integrated Space Weather Modeling)- an NSF Science

and Technology Center led by Jeff Hughes at Boston U.

MHD models of the solar corona, including those of CISM, are

just coming of age in terms of regular use and practical

applications. Simulations of the solar wind are coupled to

these coronal models, and depend on their accuracy. Full-disk

solar magnetograms from WSO have been one of the main sources

of the critical synoptic map boundary conditions used in CISM

models. In particular, they are an option in the CORHEL

community user-oriented version of the CISM corona and solar

wind model which is archived and provided for general users

at the CCMC (Community Coordinated Modeling Center) at

Goddard Space Flight Center. The NOAA SEC (Space Environment

Center) also uses CISM models for assessing upgrades to their

space weather prediction capabilities. STEREO mission, to launch

this year, will make heavy use of the magnetograph-based models

for its multipoint data interpretation.

While there are a few other sources of magnetograph-derived

synoptic maps, WSO is one of the longest-lived and most consistent

providers. These data can be used for a host of solar cycle studies

of the corona and solar wind, as well as providing the basis for

calibrating newer magnetographs, such as the SOLIS instruments at

NSO and the upgraded GONG instruments. The WSO staff does an

exceptional job of generating and providing, via website, useful

products relating to everything from the latest heliospheric

current sheet geometry to the ongoing solar cycle changes in

the solar polar fields. To lose this stable and reliable solar

magnetograph resource would be akin to losing something like the GOES

spacecraft series- it is something we have all grown to use and

depend on, and is irreplaceable in terms of its benefit to current

modeling efforts.

We hope that you will find a way to maintain the WSO magnetograph

facility and continue support for its operation and data provisions.

It would be a shame to lose its benefits at a time when it is becoming

more and more widely used and exploited given the high level of activity

in the solar and heliosphere modeling and space weather communities,

including CISM.

Sincerely,

Janet Luhmann, on behalf of CISM solar modeling members

Yes, we do use WSO observations in our work. We use them to

compare with MWO and NSO observations. Over the years, one

of the observatories occasionally has a problem. We use them

for long-term consistency. Here, spatial resolution is not

a factor. The important quantity is consistency for comparing

the fields of one cycle with another. We also use the mean

field observations, again looking for the long-term variation.

As we get into more sunspot cycle studies and studies of the

dynamo, the WSO observations will be increasingly important.

I could go on, but I will let my colleague Yi-Ming continue...

Sincerely,

Neil Sheeley

Hi -- I am writing in support of continuing the Wilcox Solar Observatory synoptic program. WSO observations were integral to my thesis work, and the citations listed below directly or indirectly depended on these data. Despite the fact that there are current and pending magnetic field observations available which have higher spatial resolution and better time coverage, there remains a set of important scientific questions regarding the large-scale, slowly-changing Sun for which WSO data are ideal. WSO provides a continuity of data which is essential to understanding solar changes on time scales on the order of solar cycles. Having used WSO data while just starting out as a graduate student, I can also testify to the ease of use of the data: the spherical harmonic coefficients were particularly useful data products for me.
So, please don't turn it off!
cheers,
Sarah
S. E. Gibson, Global solar wind structure from solar minimum to solar maximum: Sources and evolution , invited review paper for Proc. of the 34th ESLAB symposium, ESA publications (refereed), 2000.
S. E. Gibson, D. Biesecker, M. Guhathakurta, J. T. Hoeksema, A. J. Lazarus, J. Linker, Z. Mikic, Y. Pisanko, P. Riley, J. Steinberg, L. Strachan, A. Szabo, and B. J. Thompson, The Three-Dimensional Coronal Magnetic Field During Whole Sun Month, ApJ, 520, 871, 1999.
S. E. Gibson and P. Charbonneau, Empirical modeling of the solar corona using genetic algorithms, JGR, 103, 14511, 1998.
S. Gibson and P. Scherrer, Supergranule power leakage through an observing mask, in IAU Symp. 181: Sounding solar and stellar interiors (Poster volume, eds. J. Provost & F.-X. Schmider, 1998).
S. E. Gibson , F. Bagenal, D. Biesecker, M. Guhathakurta, J. T. Hoeksema, and B. J. Thompson, Modeling a simple coronal streamer during Whole Sun Month, Proc. of the Fifth SOHO WORKSHOP, ESA SP-404, 319, 1997.
S. E. Gibson, F. Bagenal, and B. C. Low, Current sheets in the solar minimum corona, JGR, 101, 4813, 1996.
S. E. Gibson and F. Bagenal, Large-scale magnetic field and density distribution in the solar minimum corona, JGR, 100, 198651, 1995.
F. Bagenal and S. Gibson, Modeling the large-scale structure of the solar corona, JGR, 96, 17663, 1991.

Dear Todd et al.:
The WSO data continue to be of great use in my research. A recent example
is the use in the paper by Bemporad et al. (2003). However, this does not
reflect our continuous use of the data on a regular basis as an aid to
interpretation of the state of the large scale corona. There is no similar
data set for us.
Our use of the data includes the source surface models and, more recently,
use of the source surface coefficients in a developing study. The utility of the
data includes:
(1) Its continuity over a very long interval.
(2) Its coverage of the entire Sun, in a synoptic data set.
(3) The ease of access, with no additional manipulation being required.
I expect to utilize the WSO data in the coming several years as an important
piece of information for developing a 'reference heliosphere' at the time of
the Voyagers' encounter with the heliosheath.
Related data sets from SOHO, the upcoming Solar-B mission, and SDO to be
launched in 2008 do not meet the same requirements. Those data are focused on
high resolution and fine scale structure studies. They do not easily address the
large-scale corona and the state of the heliosphere over multi-solar cycle
intervals.
The WSO data thus continues to be of value to a large community.
- Steve Suess
Bemporad, A., G. Poletto, S. T. Suess, Y. K. Ko, S, Parenti, P. Riley,
M. Romoli, and T. Z. Zurbuchen, Temporal evolution of a streamer complex:
coronal and in situ plasma parameters, Astrophys. J., v593, 1146-1163, 2003.

--
------
Steven T. Suess ()
NASA Marshall Space Flight Center
National Space Science & Technology Center / Solar Physics
Mail Code XD12
Huntsville, Alabama 35812-9999 USA
ph. 256-961-7611, fax 256-961-7216

Hello Todd,
I found the Wilcox solar data very useful in compiling an analysis of the effects of differential rotation on the solar magnetic field -- reference:
@Article{bergerruzmaikin00,
author = "Berger, M. A. and Ruzmaikin, A.",
title = " Magnetic helicity production by differential rotation",
journal = jgr,
year = 2000,
volume = 105,
pages = "10481--10490",
annote = " "
}
I would hope sometime in the future to extend the analysis to the most recent cycle.
Very best Wishes
Mitch
Professor Mitchell
Mathematics, University College London +44 (0) 20 7679 2835
Gower Street London WC1E 6BT
United Kingdom
+44 (0) 20 7679 2839

Hi Todd,

I don't know the cost of continuing the Stanford Wilcox observations, but I and many others regard the PFSS synoptic maps as a highly valuable asset, with the long-term continuity being an important factor here. In some ways this is like the valuable archival data base compiled by IMP-8, which was enough to find ways to keep it operating in a limited capacity long after its nominal lifetime. As you know, Nancy Crooker and I have found the Stanford SS maps very valuable in our work where we look for changes in the 1 AU inward/outward field polarities to compare with the solar-wind heat flux signatures for magnetic topologies. We hope to do more work with Nariaka Nitta to trace SS fields down to their photospheric origins for long-lived and transient structures. Then of course there are the important solar wind predictions using the nonradial expansion of open field models from the SS maps, of great value to the space weather community. I am not knowledgeable about the big question of inter-observatory field calibrations, but maybe the Wilcox observations play an important role there, as well.

Maybe the Wilcox 3-arc min data are not really needed for the SS maps, but if not, then we would want to know what new magnetograph data are replacing them and how that impacts the SS maps. The Wilcox observations will be terminated at some future time, we suppose, but it would be good to know just what data sets will replace them and what the implications are for continuing the SS maps. I am concerned, but the uncertainty of the consequences leaves me somewhat ambivalent here.

I hope this is useful for you in making the case (or not) for continued Wilcox observations.

Regards,

Steve Kahler

Dear Todd,

This e-mail is in support of the continuation of WSO observing program.

About a month ago, or so, I began to use WSO data, more specifically,

the coronal maps (WSO-R250*gif) computed from the WSO magnetic field

maps. There is no publication yet since this is a new study in progress

and about 26 WSO magnetograms-coronal images pairs (all are gifs) are

used so far to study orientations of the magnetic fields in the CME

source region, coronal and interplanetary ejecta.

I did not yet notify you about the data usage as the WSO Data Policy

requires, mainly because, again, this is a work in progress. I'll most

certainly send you a copy of a study report and include a proper credit

in a publication.

If you would like to know more details on what I do, please, let me know

I'd be happy to show you preliminary results and figures.

On June 23 I'll be visiting HEPL for one day to attend the calibration

review meeting and if it is convenient for you, I'd be happy to talk to

you about this during this visit.

Best, Vasyl

--

Vasyl Yurchyshyn

Big Bear Solar Observatory

40386 North Shore Lane

Big Bear City, CA 92314-9672

909.866.5791 x 35

909.866.4240 FAX

Hi Todd et al,
I would like to add a little weight to the argument for keeping WSO running if possible.
We have found it very valuable for comparing with interplanetary scintillation measurements
because it gives a reliable indication of the location of the neutral sheet a the source surface.
This has become more important to us as we try to compensate for the line of sight integration
in the IPS observations by modeling the full line of sight. The model requires the electron
density, not the magnetic field, but the WSO neutral sheet defines the average location of
the highest density slow wind as well as does a WLC. So we find it very valuable to have
both. The Lasco coronagraphs have greatly improved the density measurements but there
has not been a corresponding improvement in the magnetic neutral line estimate.
Although I have not been doing as much IPS recently, this work has been continued by the
group at Aberystwyth in Wales, involving Andy Breen, Richard Fallows and others. They
continue to use the modeling techniques that we developed and they find WSO data very
useful.
Bill Coles
Coles, Grall, Klinglesmith and Bourgois, JGR 100, 17069, 1995
Coles, Sp.Sc.Rev. 72, 211, 1995
Grall, Coles, Klinglesmith, Breen, Williams, Markkanen, and Esser, Nature 379, 429, 1996
Coles, Astrophys and Space Sc. 243, 87, 1996

Response to the question on continuation of WSO synoptic program.

As a user (see for example the paper Ruzmaikin, J. Feynman, M. Neugebauer and E. Smith, Preferred solar longitudes with signatures in the solar wind, J. Geophys. Res, vol 106, 8363, 2001) I vote for continuation of the WSO Program.

The availability of higher resolution solar magnetic observations, does not jeopardize the usefulness of continuing the Wilcox Solar Observatory synoptic program. First, there are applications, which do not require fine resolution but rather global averaged maps, similar to the fact that many engineering applications do well with Newton laws and do not need relativity. Second, in addition to the direct data, the WSO provides a valuable amount of processes data, such as harmonic coefficients and coronal filed extensions, which are extremely useful in doing research.

Alexander Ruzmaikin

Principal Scientist at Jet Propulsion Laboratory

California Institute of Technology.

Dear Todd and Colleagues,

I am sorry to hear that Wilcox is in danger of being shut down. There may indeed be reduced need for low spatial resolution magnetograms with new instruments coming online. However, in at least one respect Wilcox data are invaluable, namely to help determine long-term trends and to constrain models of the evolution of the magnetic field, e.g., the total magnetic flux determined at low resolution (in particular its secular evolution, which is central for producing secular trends in irradiance and other quantities that may affect our climate). Unfortunately, neither Kitt Peak nor Mt Wilson data appear to have the stability to give reliable results on their own and Wilcox data are quite indispensable. Now, the Kitt Peak SPM may be more stable than the old 512-channel magnetograph, but the large gap between the end of data taking by this instrument and the time at which SOLIS data started being regularly recorded has once again demonstrated the importance of Wilcox data. I would strongly urge you to continue gathering data at WSO until it is clear that SOLIS is providing stable results for the total magnetic flux. Maybe the maximum of the next cycle may be a better time to reconsider the future of WSO (HMI will be running and SOLIS should have provided enough data to get an idea if there are any drifts), although I would urge you to run WSO for an even longer time. There have been too many examples of long-term solar records being stopped at highly inopportune times (Greenwich observatory's end of the sunspot program in 1976 being a particularly sad example). Unfortunately, space missions cannot replace the ground-based instruments due to the limited lifetime of the former.