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Author name code: cook
ADS astronomy entries on 2022-09-14
author:"Cook, John W."
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Title: Latest Results from NASA Ames' COSmIC and Optical Constants
Facility: Determining Optical Constants for Titan, Pluto and
Protoplanetary Disks Applications
Authors: Sciamma-O'Brien, E.; Roush, T.; Salama, F.; Bertrand, T.;
Cook, J.; Dalle Ore, C.; Cruikshank, D.; Grundy, W.; Mastrapa, R.
2021AAS...23821201S Altcode:
The NASA Ames COsmic SImulation Chamber (COSmIC) is a unique
experimental facility that can be used, among many applications,
to produce solid particles from gas phase molecular precursors at
low temperature (150 K) using a plasma discharge to induce the
chemistry in the stream of a free jet expansion. The choice of
the initial gas mixture used to produce the solid sample allows
the simulation of either cold planetary atmospheres like Titan or
Pluto (with N<SUB>2</SUB>/CH<SUB>4</SUB>-based initial mixtures), or
circumstellar environments (with Ar/C<SUB>x</SUB>H<SUB>y</SUB>-based
initial mixtures). <P />The Ames Optical Constants Facility (OCF) allows
the determination of optical constants covering a broad wavelength
range with high spectral resolution for solid materials, analogs of
organic refractory materials formed in planetary and astrophysical
environments. The core of the OCF is a Fourier transform infrared
(FTIR) spectrometer that allows the continuous characterization of
solid samples in the visible to far-infrared (FIR) range (0.59-200
μm, 16,950-50 cm<SUP>−1</SUP>). Modeling of the laboratory
measurements conducted with the OCF allows the determination of
accurate optical constants, n and k, over the full vis-FIR range. <P
/>Here we present the latest results of two studies that combined
(1) experiments performed with COSmIC to produce analogs of aerosols
forming in Titan's atmosphere and analogs of cosmic grains forming in
circumstellar envelops, and (2) the characterization of these analogs
with the OCF to provide the real and imaginary parts of their refractive
indices, n + ik, to the community, from the visible to the FIR. These
optical constants can be used as critical input parameters in radiative
transfer, atmospheric and reflectance models to interpret observational
data of, e.g., Titan's atmosphere and protoplanetary disks. Providing
optical constants for various materials of different compositions
allows to explore a broad range of composition by simulating mixtures
of materials. We also present a new project to produce analogs of
Pluto's atmospheric aerosols with COSmIC and determine their optical
constants with OCF, to be used in reflectance spectra models for the
interpretation of New Horizons observations of Lowell Regio, Sputnik
Planitia and Cthulhu.
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Title: A comparison of BAA Solar Section white-light measurements
Authors: Meadows, P.; Smith, L.; Cook, J.
2021JBAA..131...22M Altcode:
This paper compares the BAA white-light measurements made during
Solar Cycle 24. The main purpose is to assess whether there are any
differences in the recorded long-term characteristics of solar activity
for observers who determine the number of groups, the sunspot number
and/or the BAA quality number (based on type of group). A comparison
is also performed between the International Sunspot Number and the
BAA sunspot number.
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Title: Notes and News: The Radio Astronomy Section in 2019
Authors: Cook, J.
2020JBAA..130...74C Altcode:
No abstract at ADS
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Title: Titan tholin like materials across the surface of Pluto
Authors: Protopapa, S.; Olkin, C.; Grundy, W.; Li, J.; Verbiscer, A.;
Gautier, T.; Cook, J.; Reuter, D.; Howett, C.; Stern, A.; Beyer, R.;
Porter, S.; Young, L.; Weaver, H.; Ennico, K.; Dalle Ore, C.; Quirico,
E.; Scipioni, F.; Singer, K.
2020AAS...23543803P Altcode:
Pluto presents in enhanced visible color images acquired with the
New Horizons' Multi-spectral Visible Imaging Camera (MVIC, Reuter
et al. 2008) a wide range of colors from vivid red, brown, to yellow
colors, highly correlated with Pluto's varied underlying geological
structures (Stern et al. 2015; Olkin et al. 2017). The color contrast
is less obvious in natural-color images. Tholins, which are the
refractory residues obtained from the irradiation of gases and ices
containing hydrocarbons (Cruikshank 2005), are thought to be present
on the surface of Pluto, serving as coloring agents (e.g., Stern et
al. 2018). However, the number of distinct types of tholins on the
surface of Pluto, and the processes responsible for their formation
and distribution remains subject of investigation. We investigate
this problem by means of 1) a multi-wavelength, regionally dependent
photometric analysis of Pluto's encounter hemisphere using the color
images collected by the Ralph/MVIC instrument on board of New Horizons
at four visible wavelengths from 400 nm to 910 nm and 2) analysis,
using a multiple-scattering radiative transfer model (Hapke, 2012), of
combined MVIC and LEISA (a mapping infrared composition spectrometer
covering the wavelength range 1.25-2.50 µm) spectra of eastern
Cthulhu and Lowell Regio. Cthulhu and Krun Maculae are significantly
darker and redder than the rest of the surface. Regions dominated by
volatile ices such as the yellow material across Pluto's north pole
observed in enhanced color images present single scattering albedos of
∼ 0.98 or higher, and almost neutral across the visible wavelength
range. This result indicates a very limited contribution of tholin
materials on the optically active surfaces in these regions. We use a
tholin material with optical constants very similar to that of Titan
tholin by Khare et al. (1984) to reproduce the spectral properties
of these two regions with such diverse coloration, compositions,
morphologies, and ages. Because a single pigment can be used to account
for all of Pluto's colors and this is consistent with a Titan tholin
like material, we concur with the idea suggested first by Grundy et
al. (2018) that Pluto's coloration is the result of photochemical
products mostly produced in the atmosphere. Although cosmic rays and
ultraviolet photons at wavelengths longer than 145 nm do reach Pluto's
surface, and can be expected to drive chemical processing there,
the observations of diverse colors do not require different chemical
products to be responsible for the colors in different environments.
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Title: The larger sunspot groups of Cycle 24
Authors: Meadows, P.; Smith, L.; Cook, J.
2019JBAA..129..222M Altcode:
Using observations submitted to the BAA Solar Section, the largest
sunspot groups of Solar Cycle 24 are discussed and example images
shown. The characteristics of the cycle are also described and a
comparison is made between the sizes of its larger sunspot groups and
those of previous cycles, stretching back over 100 years.
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Title: Traverses for the ISECG-GER design reference mission for
humans on the lunar surface
Authors: Allender, Elyse J.; Orgel, Csilla; Almeida, Natasha V.;
Cook, John; Ende, Jessica J.; Kamps, Oscar; Mazrouei, Sara; Slezak,
Thomas J.; Soini, Assi-Johanna; Kring, David A.
2019AdSpR..63..692A Altcode:
This study explores the Design Reference Mission (DRM) architecture
developed by Hufenbach et al. (2015) as a prelude to the release of the
2018 Global Exploration Roadmap (GER) developed by the International
Space Exploration Coordination Group (ISECG). The focus of this
study is the exploration of the south polar region of the Moon, a
region that has not been visited by any human missions, yet exhibits
a multitude of scientifically important locations - the investigation
of which will address long standing questions in lunar research. This
DRM architecture involves five landing sites (Malapert massif,
South Pole/Shackleton crater, Schrödinger basin, Antoniadi crater,
and the South Pole-Aitken basin center), to be visited in sequential
years by crew, beginning in 2028. Two Lunar Electric Rovers (LER) are
proposed to be tele-robotically operated between sites to rendez-vous
with crew at the time of the next landing. With engineering parameters
in mind we explore the feasibility of tele-robotic operation of these
LERs between lunar landing sites, and identify potential high interest
sampling locations en-route. Additionally, in-depth sample collection
and return traverses are identified for each individual landing site
across key geologic terrains that also detail crew Extra-Vehicular
Activity (EVA). Exploration at and between landing sites is designed to
address a suite of National Research Council (2007) scientific concepts.
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Title: The Radio Astronomy Group in 2017
Authors: Cook, J.
2018JBAA..128..116C Altcode:
No abstract at ADS
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Title: LIGO/Virgo G298048: Zadko Telescope 7 day observations of
the OT candidate SSS17a/DLT17ck
Authors: Coward, D.; Howell, E.; Laugier, R.; Klotz, A.; Boer, M.;
Andreoni, I.; Cook, J.; Macpherson, D.; Moore, J.; Burrell, A.;
OzGrav; TZAC
2017GCN.21744....1C Altcode:
We report 7 days of Zadko Telescope imaging of the transient
SSS17a/DLT17ck in NGC4339 started on 2017-08-19 10:57 UT (t0+2 days). We
use the stacked image of the night 201-08-26 (t0+9 days) as a mask to
substract the light contribution from the galaxy NGC 4993 and synthesise
one residual image for each nights observation. Photometry is performed
using the star NOMAD-1 0666-0296321 for PSF fitting. The complete log of
Zadko image analysis from t0+2 - t0+9 is: Tstart Tend r(AB) 1sigma 1.928
1.930 18.46 0.17 2.929 2.950 19.18 0.12 3.941 3.974 19.86 0.21 4.955
4.964 20.20 0.23 5.953 5.973 >20.6 6.958 6.978 >20.6 7.955 7.976
>20.6 Observations are compatible with a power law decay (alpha=-2)
or with a exponential decay with a half time of 1.25 days. The Zadko
Telescope is operated by the University of Western Australia (UWA),
and was made possible by a philanthropic donation by James Zadko, to
UWA. Zadko Telescope receives support from the ARC Centre of Excellence
"OzGrav" for gravitational wave follow-up and discovery. The facility
is managed by D.Coward (Director-UWA), E. Howell (UWA), J. Moore
(UWA), A. Burrel (UWA), A. Greensky, J. Kennewell with collaborators
I. Andreoni and J. Cook (Swinburne) This observation report was done
in partnership with the LIGO follow-up collaboration TZAC, which is
supported by M. Boer, A. Klotz, R. Laugier, K. Noysena
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Title: The Radio Astronomy Group in 2016
Authors: Cook, J.
2017JBAA..127...73C Altcode:
No abstract at ADS
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Title: Landing Site Assessment for Phase Two of eDSH-Enabled Lunar
Missions Being Examined as an ISECG-GER Mission Scenario
Authors: Ende, J. J.; Allender, E. J.; Almeida, N. V.; Cook, J.; Kamps,
O.; Mazrouei, S.; Orgel, C.; Slezak, T. J.; Soini, A. J.; Kring, D. A.
2017LPI....48.1880E Altcode:
Evaluation of five-year, five-landing site humans to the lunar surface
campaign.
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Title: Desert Rats as a Space Camp Funded Activity
Authors: Cook, J.
2017LPI....48.1041C Altcode:
Desert Rats has not been funded for years; instead of asking NASA for
funding, it is proposed to fund Desert Rats by making it an extension
of a Space Camp.
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Title: Exploration of South Polar Region of the Moon: Tele-Operated
Traverses
Authors: Kamps, O. M.; Allender, E. J.; Almeida, N. V.; Cook, J.; Ende,
J. J.; Mazrouei, S.; Orgel, C.; Slezak, T.; Soini, A. J.; Kring, D. A.
2017LPI....48.1909K Altcode:
Comparison of efficient and science, tele-operated traverses between
five human landing sites for exploration of the south pole of the Moon.
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Title: CERN@school: bringing CERN into the classroom
Authors: Whyntie, T.; Cook, J.; Coupe, A.; Fickling, R. L.; Parker,
B.; Shearer, N.
2016NPPP..273.1265W Altcode:
CERN@school brings technology from CERN into the classroom to aid
with the teaching of particle physics. It also aims to inspire the
next generation of physicists and engineers by giving participants
the opportunity to be part of a national collaboration of students,
teachers and academics, analysing data obtained from detectors based
on the ground and in space to make new, curiosity-driven discoveries
at school. CERN@school is based around the Timepix hybrid silicon
pixel detector developed by the Medipix 2 Collaboration, which
features a 300 μm thick silicon sensor bump-bonded to a Timepix
readout ASIC. This defines a 256-by-256 grid of pixels with a pitch
of 55 μm, the data from which can be used to visualise ionising
radiation in a very accessible way. Broadly speaking, CERN@school
consists of a web portal that allows access to data collected by the
Langton Ultimate Cosmic ray Intensity Detector (LUCID) experiment
in space and the student-operated Timepix detectors on the ground;
a number of Timepix detector kits for ground-based experiments, to be
made available to schools for both teaching and research purposes;
and educational resources for teachers to use with LUCID data and
detector kits in the classroom. By providing access to cutting-edge
research equipment, raw data from ground and space-based experiments,
CERN@school hopes to provide the foundation for a programme that meets
the many of the aims and objectives of CERN and the project's supporting
academic and industrial partners. The work presented here provides an
update on the status of the programme as supported by the UK Science
and Technology Facilities Council (STFC) and the Royal Commission for
the Exhibition of 1851. This includes recent results from work with
the GridPP Collaboration on using grid resources with schools to run
GEANT4 simulations of CERN@school experiments.
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Title: The Radio Astronomy Group in 2015
Authors: Cook, J.
2016JBAA..126...73C Altcode:
No abstract at ADS
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Title: A Low Noise, High QE, Large Format CCD Camera System for the
NASA MIGHTI Instrument
Authors: Hancock, J. J.; Cardon, J.; Watson, M.; Cook, J.; Whiteley,
M.; Beukers, J.; Englert, C. R.; Brown, C. M.; Harlander, J.
2015AGUFMSA51C2414H Altcode:
The Michelson Interferometer for Global High-resolution Thermospheric
Imaging (MIGHTI) instrument is part of the NASA Ionspheric Connection
Explorer (ICON) mission designed to uncover the mysteries of the extreme
variability of the Earth's ionosphere. MIGHTI consists of two identical
units positioned to observe the Earth's low latitude thermosphere from
perpendicular viewing directions. The MIGHTI instrument is a spatial
heterodyne spectrometer and requires a low noise, high QE, large format
camera system to detect slight phase changes in the fringe patterns
which reveal the neutral wind velocity. The MIGHTI camera system uses
a single control electronics box to operate two identical CCD camera
heads and communicate with the ICON payload electronics. The control
electronics are carefully designed for a low noise implementation of
CCD biases, clocking, and CCD output digitization. The camera heads
consist of a 2k by 2K, back-illuminated, frame transfer CCD provided
by e2v. The CCD's are both TEC cooled and have butcher-block filters
mounted in close proximity of the active area. The CCDs are nominally
operated in binned mode, the control electronics register settings
provide flexibility for binning and gain control. An engineering model
of the camera system has been assembled and tested. The EM camera
system characterization meets all performance requirements. Performance
highlights include a measured read noise of 5.7 electrons and dark
current of 0.01 electronics/pixel/second. The camera system design
and characterization results will be presented.
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Title: First extreme and far ultraviolet spectrum of a Comet Nucleus:
Results from 67P/Churyumov-Gerasimenko
Authors: Stern, S. A.; Feaga, L. M.; Schindhelm, R.; Steffl, A.;
Parker, J. Wm.; Feldman, P. D.; Weaver, H. A.; A'Hearn, M. F.; Cook,
J.; Bertaux, J. -L.
2015Icar..256..117S Altcode:
We used the Alice spectrograph onboard the Rosetta comet orbiter
spacecraft to observe the surface of Comet 67P/Churyumov-Gerasimenko
in the extreme and far ultraviolet (EUV/FUV) from 700 to 2050 Å in
mid-August 2014. These observations were before significant EUV/FUV coma
signatures were observed by Alice. The resulting coadded spectrum has
high signal to noise and reveals: (1) a very FUV-dark surface with (2)
a blue spectral slope and (3) no evidence of significant H<SUB>2</SUB>O
ice absorption in the FUV. We fit the measured reflectance spectrum
with a model including 99.5% tholins, 0.5% H<SUB>2</SUB>O-ice, and a
neutral darkening agent. Since we could not find any natural material
with sufficiently low EUV/FUV reflectance, we interpret the low I/F
as evidence of a fluffy, light-trapping surface. We interpret the
blue spectral slope as consistent with a surface consisting primarily
of tholins, though it may alternatively be the result of Rayleigh
scattering by fine particles in the regolith.
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Title: The Radio Astronomy Group in 2014
Authors: Cook, J.
2015JBAA..125R.137C Altcode:
No abstract at ADS
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Title: Design, Development, Implementation, and On-orbit Performance
of the Dynamic Ionosphere CubeSat Experiment Mission
Authors: Fish, C. S.; Swenson, C. M.; Crowley, G.; Barjatya, A.;
Neilsen, T.; Gunther, J.; Azeem, I.; Pilinski, M.; Wilder, R.; Allen,
D.; Anderson, M.; Bingham, B.; Bradford, K.; Burr, S.; Burt, R.;
Byers, B.; Cook, J.; Davis, K.; Frazier, C.; Grover, S.; Hansen, G.;
Jensen, S.; LeBaron, R.; Martineau, J.; Miller, J.; Nelsen, J.; Nelson,
W.; Patterson, P.; Stromberg, E.; Tran, J.; Wassom, S.; Weston, C.;
Whiteley, M.; Young, Q.; Petersen, J.; Schaire, S.; Davis, C. R.;
Bokaie, M.; Fullmer, R.; Baktur, R.; Sojka, J.; Cousins, M.
2014SSRv..181...61F Altcode: 2014SSRv..tmp....2F
Funded by the NSF CubeSat and NASA ELaNa programs, the Dynamic
Ionosphere CubeSat Experiment (DICE) mission consists of two 1.5U
CubeSats which were launched into an eccentric low Earth orbit on
October 28, 2011. Each identical spacecraft carries two Langmuir
probes to measure ionospheric in-situ plasma densities, electric
field probes to measure in-situ DC and AC electric fields, and a
science grade magnetometer to measure in-situ DC and AC magnetic
fields. Given the tight integration of these multiple sensors with
the CubeSat platforms, each of the DICE spacecraft is effectively a
"sensor-sat" capable of comprehensive ionospheric diagnostics. The use
of two identical sensor-sats at slightly different orbiting velocities
in nearly identical orbits permits the de-convolution of spatial and
temporal ambiguities in the observations of the ionosphere from a moving
platform. In addition to demonstrating nanosat-based constellation
science, the DICE mission is advancing a number of groundbreaking
CubeSat technologies including miniaturized mechanisms and high-speed
downlink communications.
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Title: The Radio Astronomy Group, 2013
Authors: Cook, J.
2014JBAA..124...66C Altcode:
No abstract at ADS
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Title: The Radio Astronomy Group in 2012
Authors: Cook, J.
2013JBAA..123..133C Altcode:
Solar activity detected during 2012 by the Radio Astronomy Group
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Title: Meeting contribution: SIDs, SFEs and CMEs in 2012
Authors: Cook, J.
2013JBAA..123..167C Altcode:
No abstract at ADS
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Title: U.S. government export control reform initiative - what's
going on?
Authors: Cook, J.; Cook, K.
2013aero.confE..47C Altcode:
While there is still more work to be done, taken together, these
reforms will focus our resources on the threats that matter most, and
help us work more effectively with our allies in the field. They'll
bring transparency and coherence to a field of regulation which
has long been lacking both. And by enhancing the competitiveness
of our manufacturing and technology sectors, they'll help us not
just increase exports and create jobs, but strengthen our national
security as well.” - President Obama, Department of Commerce Annual
Export Controls Update Conference, August 30, 2010. This paper will
provide background information and discuss the need for export control
reform. It will lay out the schedule for the Export Control Reform
Initiative as well as provide an update on the current status of the
ECR Initiative, including advances made in Phases I and II. It will
provide insight into the proposed changes to the USML and the CCL
and will discuss the proposed IT system modernization and the Export
Enforcement Coordination Center (E2C2).
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Title: Modeling Insights into the Lunar Exosphere
Authors: Hurley, D.; Feldman, P. D.; Retherford, K. D.; Cook, J.;
Stern, S. A.
2012AGUFM.P42B..06H Altcode:
In addition to Apollo data from the 1970s and ground-based observations,
recent data from the Lyman Alpha Mapping Project (LAMP) onboard the
Lunar Reconnaissance Orbiter (LRO) are revealing the structure and
variability of the lunar exosphere. LAMP has detected helium in the
lunar exosphere having many sources of variability. We use a Monte
Carlo model to interpret variability in the observations of helium
in the lunar exosphere from LAMP. Some of the variability stems from
a time-varying source rate. Because the helium in the lunar exosphere
predominately derives from the solar wind, we investigate the timescale
of transport from release on the dayside to the nightside where it is
observed. The model computes transport times for various assumptions
about the energy distribution during the initial release and the effects
of subsequent surface interactions on the ballistic transport. Owing to
the changing geometry of the LRO orbit, spatial gradients also factor
into the variability of the observations. We study the expected column
density of helium as a function of latitude and longitude using surface
temperatures measured by Diviner. The spatial distribution resulting
from model runs is strongly influenced by the surface temperature and
the assumed thermalization parameter. These dependencies can be used to
extract information about the surface interactions. We compare model
latitude and longitude dependences to LAMP and Apollo data. Finally,
using upstream solar wind measurements and the position of LRO,
we calculate the model time-varying helium exosphere of the Moon for
comparison with LAMP data obtained in January, June, and July of 2012,
including three passages of the Moon through Earth's magnetotail.
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Title: Lunar Atmospheric Helium Detections By the LAMP UV Spectrograph
On the NASA Lunar Reconnaissance Orbiter
Authors: Stern, S. Alan; Retherford, K.; Cook, J.; Tsang, C.; Feldman,
P.; Pryor, W.; Gladstone, R.
2012DPS....4440109S Altcode:
The LAMP far ultraviolet spectrograph aboard the NASA Lunar
Reconnaissance Orbiter (LRO) was used in 2011 to search for the lightest
noble gas, helium, in the tenuous lunar atmosphere. Based on that
search, we report here the first detection of lunar atmospheric He
by remote sensing, and point to future observations that can address
questions about its source. We also report the discovery of lunar He
atmospheric abundance variations detected by LAMP, including what appear
to be several short-lived, extreme abundance increase events. If these
are confirmed, the logical next question will be to determine whether
they are of indigenous or exogenous origin. If they are of indigenous
origin, they may offer a way to measure some kinds of lunar internal
activity or seismicity from orbit.
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Title: The Radio Astronomy Group in 2011
Authors: Cook, J.
2012JBAA..122..145C Altcode:
No abstract at ADS
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Title: The X-Shooter spectrum of (136199) Eris
Authors: Alvarez-Candal, A.; Pinilla-Alonso, N.; Licandro, J.; Cook,
J.; Mason, E.; Roush, T.; Cruikshank, D.; Gourgeot, F.; Dotto, E.;
Perna, D.
2011epsc.conf..524A Altcode: 2011DPS....43..524A
We observe Eris, one of the largest trans-Neptunian objects, in
the 300 - 2480 nm range with X-Shooter, the first second-generation
instrument for the ESOVery Large Telescope, and compare the newly
obtained spectra with those available in the literature. The large
spectra coverage and high resolving power (?/?? ' 5000) of X-Shooter
allow us to study absorption features due to CH4 and search for other
ices' absorptions. We measure the positions and depth of CH4 absorption
features and compare them with those of reflectance of pure methane ice
obtained from the optical constants of this ice at 30 K to study shifts
in their positions. We do not directly detect absorption bands due to
N2 or CO ices in the spectra. Nevertheless, the measured wavelength
shifts of the CH4 absorption features points to a dilution of this
ice in another one on the surface of Eris and the presence of pure CH4
spatially segregated. The comparison of the centers and shapes of these
bands with previous works suggest that the surface is heterogeneous.
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Title: Analysis of High Resolution Spectra of Eris: Possible Evidence
for Cold Phase CH4 Ice
Authors: Cook, J.; Mastrapa, R. M.; Cruikshank, D. P.; Alvarez-Candal,
A.; Pinilla-Alonso, N.
2011epsc.conf.1279C Altcode: 2011DPS....43.1279C
We examined the spectrum of Eris by isolating the 1.67 and 1.72
μm CH4 bands and comparing these to Hapke models. These bands are
chosen because (i) CH4(II) is more distinguished from CH4(I) at these
wavelengths and (ii) the SNR of the observationswere higher than the
bands longward of 1.8 μm. At the time of writing this abstract, the
analysis was performed using optical constants for pure CH4 because
of the lack of optical constants for CH4 diluted in N2 between 15
and 30 K.We assume the spectrum of Eris is a spectral blend of both
CH4 phases. To model the spectrum, we used the CH4 optical constants
from (11). CH4(II) ice is represented by their 20 K measurements,
while optical constants for the CH4(I) ice is estimated from a
linear interpolation between measurements at T > 30 K, or a second
order extrapolation of the data at T > 30 to estimate the optical
constants at 20.4 < T < 30 K. Each component is allowed to shift
in wavelength.
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Title: The spectrum of (136199) Eris between 350 and 2350 nm:
results with X-Shooter
Authors: Alvarez-Candal, A.; Pinilla-Alonso, N.; Licandro, J.; Cook,
J.; Mason, E.; Roush, T.; Cruikshank, D.; Gourgeot, F.; Dotto, E.;
Perna, D.
2011A&A...532A.130A Altcode: 2011arXiv1107.1708A
Context. X-Shooter is the first second-generation instrument for the
ESO-Very Large Telescope. It is a spectrograph covering the entire
300-2480 nm spectral range at once with a high resolving power. These
properties enticed us to observe the well-known trans-Neptunian
object (136199) Eris during the science verification of the
instrument. The target has numerous absorption features in the optical
and near-infrared domain that have been observed by different authors,
showing differences in these features' positions and strengths. <BR />
Aims: Besides testing the capabilities of X-Shooter to observe minor
bodies, we attempt to constrain the existence of super-volatiles,
e.g., CH<SUB>4</SUB>, CO and N<SUB>2</SUB>, and in particular we
try to understand the physical-chemical state of the ices on Eris'
surface. <BR /> Methods: We observed Eris in the 300 - 2480 nm range
and compared the newly obtained spectra with those available in the
literature. We identified several absorption features, measured their
positions and depth, and compare them with those of the reflectance
of pure methane ice obtained from the optical constants of this ice at
30 K to study shifts in these features' positions and find a possible
explanation for their origin. <BR /> Results: We identify several
absorption bands in the spectrum that are all consistent with the
presence of CH<SUB>4</SUB> ice. We do not identify bands related to
N<SUB>2</SUB> or CO. We measured the central wavelengths of the bands
and compared to those measured in the spectrum of pure CH<SUB>4</SUB>
at 30 K finding variable spectral shifts. <BR /> Conclusions: Based
on these wavelength shifts, we confirm the presence of a dilution of
CH<SUB>4</SUB> in other ice on the surface of Eris and the presence
of pure CH<SUB>4</SUB> that is spatially segregated. The comparison
of the centers and shapes of these bands with previous works suggests
that the surface is heterogeneous. The absence of the 2160 nm band
of N<SUB>2</SUB> can be explained if the surface temperature is below
35.6 K, the transition temperature between the alpha and beta phases
of this ice. Our results, including the reanalysis of data published
elsewhere, point to a heterogeneous surface on Eris. <P />Observations
made during X-Shooter Science Verification, program 60.A-9400(A), PIs:
Alvarez-Candal and Mason.
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Title: An introduction to solar radio astronomy
Authors: Cook, J.
2011JBAA..121..241C Altcode:
No abstract at ADS
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Title: The Radio Astronomy Group in 2010
Authors: Cook, J.
2011JBAA..121..133C Altcode:
No abstract at ADS
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Title: Micrometeorite Annealing of Solar System Icy Objects
Authors: Porter, Simon; Desch, S.; Cook, J.
2009DPS....41.6508P Altcode:
Near-IR spectral observations appear to show that crystalline water ice
is common in the outer solar system. This is unexpected, as amorphous
solid water (ASW) is also stable beyond the orbit of Jupiter, and
produced when crystalline ice is exposed to radiation. The annealing of
surface ASW to crystalline ice through the impact heat of interplanetary
micrometeorites may be sufficient to explain the observed crystalline
spectra of many icy satellites. Through numerical modeling of both
impact thermal diffusion and gravitational focusing, we have found
that interplanetary dust particle impacts may provide a sufficient
kinetic energy flux to effectively anneal ASW on geologically fast
timescales. We estimated that this rate is sufficient to compete with
ice amorphization by ultraviolet and ion irradiation for most of the
saturnian and uranian satellites. This effect is strongly amplified by
the proximity of the satellite to its planet, due to both gravitational
focusing and the satellite's planetocentric velocity. Though these
calculations were made for pure ice and assume spherical diffusion,
we further show that icy-rocky mixtures and cylindrical diffusion both
result in higher annealing rates. Impact annealing due to planetary
dust (i.e. the E ring) was not effective. In addition, this model can
be applied to explaining the crystallinity of Kuiper Belt object (KBO)
surfaces. Though they have lower heliocentric velocities and no giant
planet to gravitationally focus dust, the dust fluxes in the Kuiper
Belt may be large enough to anneal ASW. Micrometeorite annealing could
therefore explain that unexpectedly high crystallinity of objects not
expected to have active surface cryovolcanism, like Haumea. If the
method is effective on KBOs, it may in turn be used to as a probe of
Kuiper Belt dust as function of distance from the Sun.
---------------------------------------------------------
Title: Solar EUV Spectral Irradiance Throughout The 3-Dimensional
Heliosphere
Authors: McMullin, D. R.; Auchere, F.; Cook, J. W.; Newmark, J. S.;
Quemerais, E.; von Steiger, R.; Witte, M.
2008AGUFMSH13B1522M Altcode:
When Ulysses moved from 30 to 80 degrees in solar latitude (July
2001), the Ulysses GAS instrument measured an apparent increase
in the neutral He density. This is more naturally interpreted as
a latitudinal dependence (decrease) of the loss rate due to solar
photoionization rather than a true increase of the neutral He
density. This concept has been tested through the development of a
3-Dimensional solar EUV model for the Heliosphere. The model concept
has been presented earlier, and we are now presenting results and
applications of the new model. Using daily SOHO EIT observations,
over successive Carrington rotations, we have developed a three-
dimensional model for solar EUV fluxes observed at any heliospheric
position, projected to any heliospheric position. The combined
effects of solar rotational and latitude-dependent flux variability
are explicitly treated in this model. The flux model will be compared
with other direct spectral irradiance observations in the ecliptic
plane, such as those available from the TIMED SEE instrument as well
as broadband measurements available from the SOHO/SEM irradiance time
series. These comparisons will be used in part to validate the current
results. We then use this flux to compute the photoionization rate of
the in-flowing neutral Helium, and compare the modeled change with that
observed along the spacecraft trajectory with the direct measurements
from the out-of-ecliptic Ulysses GAS observations. The unique GAS
comparisons will provide validation of the original hypothesis as to
the latitudinal dependence (decrease) of the loss rate due to solar
photoionization rather than an increase of the neutral He density.
---------------------------------------------------------
Title: Inverse Whitelight Reconstruction of STEREO-observed CMEs
Authors: Antunes, A.; Cook, J. W.; Newmark, J. S.; Ontiveros, V.;
Thernisien, A.
2008AGUSMSH21A..07A Altcode:
With STEREO spacecraft separation now at greater than 40 degrees, we
can examine 3D reconstructions using white light coronagraph data to
constrain the observed CME underlying morphology and kinematics. We
reconstruct the electron densities for the December 31, 2007 CME and
associated streamer using individual pairs of STEREO observations
from the COR 2 coronagraph, and then add a third viewpoint with LASCO
coronagraph observations from SOHO. We also examine kinematics for the
December 31 CME from successive reconstructions of the event during its
development. Our tomographic technique uses the PIXON algorithm for our
reconstructions. We overlay these results with forward reconstruction of
a model flux rope and with geometric line-of-sight mass integrations. We
also compare these results with other 2008 CMEs, and finally, illustrate
how the community can use our publicly available reconstruction toolkit.
---------------------------------------------------------
Title: Theoretical modeling for the stereo mission
Authors: Aschwanden, Markus J.; Burlaga, L. F.; Kaiser, M. L.; Ng,
C. K.; Reames, D. V.; Reiner, M. J.; Gombosi, T. I.; Lugaz, N.;
Manchester, W.; Roussev, I. I.; Zurbuchen, T. H.; Farrugia, C. J.;
Galvin, A. B.; Lee, M. A.; Linker, J. A.; Mikić, Z.; Riley, P.;
Alexander, D.; Sandman, A. W.; Cook, J. W.; Howard, R. A.; Odstrčil,
D.; Pizzo, V. J.; Kóta, J.; Liewer, P. C.; Luhmann, J. G.; Inhester,
B.; Schwenn, R. W.; Solanki, S. K.; Vasyliunas, V. M.; Wiegelmann, T.;
Blush, L.; Bochsler, P.; Cairns, I. H.; Robinson, P. A.; Bothmer,
V.; Kecskemety, K.; Llebaria, A.; Maksimovic, M.; Scholer, M.;
Wimmer-Schweingruber, R. F.
2008SSRv..136..565A Altcode: 2006SSRv..tmp...75A
We summarize the theory and modeling efforts for the STEREO mission,
which will be used to interpret the data of both the remote-sensing
(SECCHI, SWAVES) and in-situ instruments (IMPACT, PLASTIC). The
modeling includes the coronal plasma, in both open and closed magnetic
structures, and the solar wind and its expansion outwards from the Sun,
which defines the heliosphere. Particular emphasis is given to modeling
of dynamic phenomena associated with the initiation and propagation
of coronal mass ejections (CMEs). The modeling of the CME initiation
includes magnetic shearing, kink instability, filament eruption, and
magnetic reconnection in the flaring lower corona. The modeling of CME
propagation entails interplanetary shocks, interplanetary particle
beams, solar energetic particles (SEPs), geoeffective connections,
and space weather. This review describes mostly existing models of
groups that have committed their work to the STEREO mission, but is by
no means exhaustive or comprehensive regarding alternative theoretical
approaches.
---------------------------------------------------------
Title: Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI)
Authors: Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.;
Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Cook, J. W.; Hurley,
A.; Davila, J. M.; Thompson, W. T.; St Cyr, O. C.; Mentzell, E.;
Mehalick, K.; Lemen, J. R.; Wuelser, J. P.; Duncan, D. W.; Tarbell,
T. D.; Wolfson, C. J.; Moore, A.; Harrison, R. A.; Waltham, N. R.;
Lang, J.; Davis, C. J.; Eyles, C. J.; Mapson-Menard, H.; Simnett,
G. M.; Halain, J. P.; Defise, J. M.; Mazy, E.; Rochus, P.; Mercier,
R.; Ravet, M. F.; Delmotte, F.; Auchere, F.; Delaboudiniere, J. P.;
Bothmer, V.; Deutsch, W.; Wang, D.; Rich, N.; Cooper, S.; Stephens,
V.; Maahs, G.; Baugh, R.; McMullin, D.; Carter, T.
2008SSRv..136...67H Altcode: 2008SSRv..tmp...64H
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) is a five telescope package, which has been developed for
the Solar Terrestrial Relation Observatory (STEREO) mission by the
Naval Research Laboratory (USA), the Lockheed Solar and Astrophysics
Laboratory (USA), the Goddard Space Flight Center (USA), the University
of Birmingham (UK), the Rutherford Appleton Laboratory (UK), the
Max Planck Institute for Solar System Research (Germany), the Centre
Spatiale de Leige (Belgium), the Institut d’Optique (France) and the
Institut d’Astrophysique Spatiale (France). SECCHI comprises five
telescopes, which together image the solar corona from the solar disk to
beyond 1 AU. These telescopes are: an extreme ultraviolet imager (EUVI:
1 1.7 R<SUB>⊙</SUB>), two traditional Lyot coronagraphs (COR1: 1.5 4
R<SUB>⊙</SUB> and COR2: 2.5 15 R<SUB>⊙</SUB>) and two new designs
of heliospheric imagers (HI-1: 15 84 R<SUB>⊙</SUB> and HI-2: 66 318
R<SUB>⊙</SUB>). All the instruments use 2048×2048 pixel CCD arrays
in a backside-in mode. The EUVI backside surface has been specially
processed for EUV sensitivity, while the others have an anti-reflection
coating applied. A multi-tasking operating system, running on a PowerPC
CPU, receives commands from the spacecraft, controls the instrument
operations, acquires the images and compresses them for downlink
through the main science channel (at compression factors typically
up to 20×) and also through a low bandwidth channel to be used for
space weather forecasting (at compression factors up to 200×). An
image compression factor of about 10× enable the collection of images
at the rate of about one every 2 3 minutes. Identical instruments,
except for different sizes of occulters, are included on the STEREO-A
and STEREO-B spacecraft.
---------------------------------------------------------
Title: Slow Monopole Signals in Water and Ice Detectors
Authors: Cook, J.; Paul, T.; Reucroft, S.; Swain, J.
2008ICRC....4..825C Altcode: 2008ICRC...30d.825C
We consider the possible use of water and ice detectors designed for
other purposes as detectors for slow magnetic monopoles. The mechanism
we assume to dominate is monopole catalyzed baryon decay which can
very efficiently turn protons into electromagnetic energy. Estimates
of sensitivity for existing detectors are given.
---------------------------------------------------------
Title: SCROD: An Update
Authors: Cook, J.; Musienko, Y.; McCauley, T.; Paul, T.; Reucroft,
S.; Swain, J.
2008ICRC....2..465C Altcode: 2008ICRC...30b.465C
We give an update on the most recent design of the "School Cosmic Ray
Outreach Detector” (SCROD) using pixellated Geiger-mode avalanche
photodiodes and scintillating tiles with wavelength shifting fibers
as detectors. This technology offers very high levels of robustness
at low cost. Voltages and currents are also so low as to reduce shock
hazard to zero, and there are no fragile glass or vacuum-containing
components. Plans are underway to make a very large-scale deployment
of such detectors as part of a major outreach project.
---------------------------------------------------------
Title: The SECCHI experiment on STEREO
Authors: Newmark, J. S.; Cook, J. W.; Moses, J. D.
2007SPIE.6689E..02N Altcode: 2007SPIE.6689E...2N
The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI)
developed for the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of optical telescopes that will, for the first time,
observe the entire inner heliosphere from the solar surface out to
the vicinity of Earth from twin spacecraft. SECCHI was developed by an
international consortium led by the Naval Research Laboratory (NRL). The
primary objective of the STEREO mission is to understand the Coronal
Mass Ejection (CME) phenomenon, discovered in 1971, and most recently
extensively observed by the NASA/ESA Solar and Heliospheric Observatory
(SOHO). The SECCHI telescope suite is returning unprecedented views of
the Sun and inner heliosphere. The SECCHI instruments on each of the
two STEREO spacecraft observe CMEs from their initiation, through the
corona, and into interplanetary space beyond the Earth's orbit. We
present an overview of the development and early operations of the
SECCHI experiment.
---------------------------------------------------------
Title: NRL EUV Imager: The Solar EUV Atmospheric Research Of The
Corona And Heliosphere (SEARCH) Experiment
Authors: Newmark, J. S.; Doschek, G. A.; Brown, C. M.; Cook, J. W.;
Kilmchuk, J. A.; Korendyke, C. M.; Moses, J. D.; Myers, S. H.; Seely,
J. F.
2007ESASP.641E..74N Altcode:
Achieving the Solar Orbiter primary science goals requires knowledge
of the fine structure of the solar atmosphere from chromospheric
to coronal temperatures, and the structural links between these
different temperature regions. An EUV imager is an ideal instrument
for providing this crucial information, and the Solar Orbiter mission
gives a unique opportunity to investigate the fine structure of the
chromosphere, transition region, and corona at unprecedented high
spatial resolution. We present a concept from the US Naval Research
Laboratory (NRL) for providing an Extreme Ultraviolet (EUV) Imager for
the Solar Orbiter mission, the "Solar EUV Atmospheric Research of the
Corona and Heliosphere" (SEARCH) experiment.
---------------------------------------------------------
Title: Recent Cluster wideband studies of auroral kilometric radiation
Authors: Mutel, R.; Menietti, D.; Christopher, I.; Gurnett, D.; Cook,
J.; Frey, H.
2006ESASP.598E..79M Altcode: 2006cds..sympE..79M
No abstract at ADS
---------------------------------------------------------
Title: Comparison of the Sacramento Peak Fe XIV Index with a Model
Index Computed from Differential Emission Measure Maps
Authors: Cook, J. W.; Newmark, J. S.; Altrock, R. C.
2005ApJ...633..518C Altcode:
We compare the Sacramento Peak Fe XIV 5303 Å green line index with a
model index time series for the period of operations of the EUV Imaging
Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO),
covering the years 1996-2002, from cycle minimum past the peak of the
current activity cycle 23. We compute a differential emission measure
(DEM) map for each day using images from the four channels of EIT at
171, 195, 284, and 304 Å. From the daily DEM map we then calculate
a daily synthetic Fe XIV 5303 Å intensity image. The Sacramento Peak
index is an average intensity, measured using a circular aperture 1.1
arcmin in diameter, sampling the off-limb corona in 3° steps around
disk center. It is taken at several different heights beyond the daily
white light limb. We modeled the daily index values, for the aperture
center at 1.15 and 1.25 R<SUB>solar</SUB> from disk center, as the
weighted average intensity within an annulus covering 1.11-1.19 and
1.21-1.29 R<SUB>solar</SUB> superposed on the daily synthetic intensity
image. We compare the observed index with our model results and find a
high correlation of the short-term values but a long-term systematic
difference in the absolute values. We examine the accuracy of the
respective calibrations and argue that the model results, based on
the calibration of the EIT images used to produce the daily DEM maps,
are more plausible in absolute value.
---------------------------------------------------------
Title: A Model for Solar EUV Flux Helium Photoionization Throughout
the 3-Dimensional Heliosphere
Authors: Auchère, F.; McMullin, D. R.; Cook, J. W.; Newmark, J. S.;
von Steiger, R.; Witte, M.
2005ESASP.592..327A Altcode: 2005soho...16E..49A; 2005ESASP.592E..49A
No abstract at ADS
---------------------------------------------------------
Title: The Heliospheric He II 30.4 nm Solar Flux During Cycle 23
Authors: Auchère, F.; Cook, J. W.; Newmark, J. S.; McMullin, D. R.;
von Steiger, R.; Witte, M.
2005ApJ...625.1036A Altcode:
Because of the orbit characteristics of the vast majority of
spacecraft, the solar flux has predominantly been measured at Earth
or at least in the plane of the ecliptic. Therefore, the existing
data do not directly demonstrate the fact that the latitudinal
distribution of the extreme-ultraviolet (EUV) solar flux is largely
anisotropic. Indeed, in the EUV the nonuniform distribution of very
contrasted bright features (i.e., active regions) and dark features
(i.e., coronal holes) at the surface of the Sun produces both the
obvious rotational (or longitudinal) modulation of the flux and also
a strong latitudinal anisotropy. Although largely ignored up to now,
the latitudinal anisotropy affects the physical conditions in the
corona and heliosphere and should therefore be taken into account in
several solar and heliospheric physics applications. We describe in this
paper a technique for computing the He II 30.4 nm flux at an arbitrary
position in the heliosphere from Solar and Heliospheric Observatory
(SOHO) EUV Imaging Telescope (EIT) images. This procedure was used to
produce daily all-sky maps of the 30.4 nm flux from 1996 January to 2003
August, covering the first 8 yr of solar cycle 23. As could be expected
from the examination of the EIT images, the 30.4 nm flux was found to
be strongly anisotropic. The anisotropy I<SUB>pol</SUB>/I<SUB>eq</SUB>
between the fluxes computed for viewpoints located above the solar
poles and within the solar equatorial plane ranges from 0.9 at solar
minimum to 0.6 at solar maximum. A 20% difference was also discovered
between the north and south polar fluxes. The generalization of this
technique to other lines of the EUV and far-ultraviolet (FUV) spectrum
is discussed.
---------------------------------------------------------
Title: Morphological Classes and Stellar Populations of Galaxies in
Introductory Astronomy Labs at Arizona State University
Authors: Will, L. M.; Cook, J.; Scowen, P.
2005AAS...206.0208W Altcode: 2005BAAS...37..431W
At Arizona State University, introductory astronomy lab students
made observations of several galaxies visible in the spring sky. The
students used the Hubble classification system introduced in the lab
to assign morphological types to these galaxies. From creating color
images and using their knowledge of stellar populations from previous
lab exercises, the students were able to draw conclusions about the
relative ages of galaxies and likelihood of ongoing star formation,
This lab exercise involved remote observing with ASU's Braeside
Observatory, located in Flagstaff, AZ. This poster will outline the
laboratory exercise and student responses to this new addition to our
astronomy lab curriculum.
---------------------------------------------------------
Title: Forward Modeling of CMEs Using LASCO Data and for the STEREO
Mission
Authors: Thernisien, A. F.; Howard, R. A.; Cook, J. W.
2005AGUSMSH52A..05T Altcode:
The future STEREO mission, due to launch in early 2006, will have
two twin satellites that will observe the Sun and its corona from
two different points of view. The main goal of the mission is to
understand how the CMEs are initiated and how they evolve during
time. Using the two points of view will permit a reconstruction of the
electron density and morphology of coronal structures such as CMEs. Two
approaches are possible to reach that goal: an inversion technique,
assuming no or little a priori assumptions of the structure, and a
forward modeling technique, for which a morphology and location of
the studied structure is assumed. In this poster we present a forward
modeling method used to determined the electron density of different
CMEs from SOHO-LASCO data. We used the graduated cylindrical shell
(GCS) model, an empirical simulation of a flux-rope CME. We used time
sequences and assumption of self similarity to have many views of the
same CME for a best fit. We used also minimization techniques to find
the best fit of the different model parameters.
---------------------------------------------------------
Title: Solar EUV and UV spectral irradiances and solar indices
Authors: Floyd, Linton; Newmark, Jeff; Cook, John; Herring, Lynn;
McMullin, Don
2005JASTP..67....3F Altcode: 2005JATP...67....3F
Several experiments have measured solar EUV/UV flux in the last 10
15 years including SUSIM UARS, SOHO CELIAS SEM, and SOHO EIT and
have generated multi-year spectral irradiance time series. Empirical
models of these important sources of radiant energy are often based
on solar activity proxies, most often, the solar 10.7 cm radio flux
(F<SUB>10.7</SUB>). The short- and long-term correspondence of four
solar activity index time series International Sunspot Number, the He
1083 Equivalent Width, F10.7<SUB>, and the Mg II core-to-wing ratio
are analyzed. All of these show well-correlated long-term behavior
with F10.7</SUB> and Mg II showing the greatest long-term agreement
among all of the index pairs. However, during the recent maximum
period of solar cycle 23, both the ISN and He 1083 have diverged
significantly from the others. Recent UV and EUV measurements are
compared with Mg II and F10.7<SUB> to assess their value as solar
activity proxies. In every case, Mg II was found to correlate more
strongly than F10.7</SUB> with the UV and EUV time series which
correspond to a range of solar atmospheric temperatures of 4000K
2 MK. This correspondence indicates that the mechanisms underlying
irradiances changes from upper photospheric chromospheric, transition
region, and lower coronal solar atmospheric layers are closely linked.
---------------------------------------------------------
Title: SCROD: A new approach to large school based cosmic ray
experiments
Authors: Swain, J.; Cook, J.; Gouchtchine, E.; Musienko, Y.; Paul,
T.; Reucroft, S.
2005ICRC....9..323S Altcode: 2005ICRC...29i.323S
No abstract at ADS
---------------------------------------------------------
Title: Model of the all-sky He II 30.4 nm solar flux
Authors: Auchère, F.; Cook, J. W.; Newmark, J. S.; McMullin, D. R.;
von Steiger, R.; Witte, M.
2005AdSpR..35..388A Altcode:
Because of the orbit characteristics of the vast majority of spacecraft,
the solar flux has been generally measured at Earth or in the plane
of the ecliptic. So far, most published studies did not consider
the fact that the extreme ultraviolet (EUV) solar flux is largely
anisotropic. Indeed, in the EUV, the distribution of very contrasted
bright and dark features at the surface of the Sun produces both the
obvious rotational (longitudinal) modulation of the flux, but also a
strong latitudinal anisotropy. Although largely ignored up to now, the
latitudinal anisotropy affects the physical conditions in the corona
and heliosphere. We describe an empirical model of the all-sky He II
30.4 nm flux based on EIT/ SOHO data. The 30.4 nm flux was found to be
strongly anisotropic. The anisotropy I<SUB>pol</SUB>/ I<SUB>eq</SUB>
between the fluxes computed for viewpoints located above the solar
poles and within the solar equatorial plane ranges from 0.9 at solar
minimum to 0.6 at solar maximum. A 20% asymmetry was also discovered
between the north and south polar fluxes.
---------------------------------------------------------
Title: A Model For EUV Flux Throughout The 3-Dimensional Heliosphere
Authors: McMullin, D. R.; Auchere, F.; Cook, J.; Newmark, J. S.;
Quemerais, E.; von Steiger, R.; Witte, M.
2004AGUFMSH21B0423M Altcode:
After July 2001, when Ulysses moved from 30 to 80 degrees in solar
latitude, the Ulysses GAS instrument measured an apparent increase
in the neutral He density. This is more naturally interpreted as
a latitudinal dependence (decrease) of the loss rate due to solar
photoionization rather than a true increase of the neutral He
density. We have developed a three-dimensional model for solar EUV
fluxes observed at any heliospheric position, using daily SOHO EIT
observations, over successive Carrington rotations, projected to
any heliospheric position. The combined effects of solar rotational
and latitude-dependent flux variability are explicitly treated in
this model. The flux model has been directly compared with other
direct irradiance observations in the ecliptic plane with the SOHO/SEM
irradiance time series for validation. We then use this flux to compute
the photoionization rate of the in-flowing neutral He, and compare the
modeled change with time along the spacecraft trajectory with the direct
measurements from the out -of -ecliptic Ulysses GAS observations. The
3-D model developed will be directly applicable to STEREO EUV images
from the SECCHI instrument suite. As the two spacecraft separate, the
amount of the solar surface observed will increase through the mission,
providing more accurate solar inputs.
---------------------------------------------------------
Title: Comparison of Tomographic and Forward Modeling 3D
Reconstructions of a Coronal Streamer
Authors: Newmark, J. S.; Cook, J.; Reiser, P.; Thernisien, A.
2004AGUFMSH21B0421N Altcode:
We compare 3D reconstructions of a coronal streamer using two different
techniques. Thernisien employs images from the LASCO coronagraph on
board SOHO and determines the optimal parameter values of a general
slab model (with folds) for electron density yielding a synthetic white
light image that best matches the starting LASCO data (Thernisien et
al. 2004, B.A.A.S., 36, 797). This forward modeling approach forces
the solution to be of a pre-determined functional form. We compare
this reconstruction with a true tomographic reconstruction using input
images from multiple viewpoints, with no predetermined constraint on
the geometry of the electron density distribution found. As an initial
test of the tomographic reconstruction, we start with input synthetic
coronagraph data rendered from the Thernisien model electron density
reconstruction, and first compare the tomographic reconstruction to
this known starting distribution. We next use true LASCO data from
different days (rotational tomography) for a tomographic reconstruction,
and compare the reconstructed electron density distribution and its
rendered synthetic coronagraph data with the Thernisien electron
densities and rendered coronagraph data. In general, with real
data the tomographic reconstruction produces synthetic coronagraph
images rendered from its electron density determination that are more
similar to the input LASCO data, while the Thernisien electron density
determination is more tightly structured, from its prior constraints,
than the tomographic reconstruction from a very limited number of
viewpoints. The two techniques are complementary, and both will provide
useful reconstruction tools for use in the upcoming STEREO mission,
due for launch in early 2006. JWC and JSN are supported on this work
by NASA under W10135, and by the Office of Naval Research.
---------------------------------------------------------
Title: Solar UV Irradiance Measurements from SUSIM UARS
Authors: Floyd, L. E.; Cook, J. W.; Herring, L. C.
2004AGUFMSH53B0309F Altcode:
The Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) aboard the
Upper Atmosphere Research Satellite (UARS) has measured the solar UV
irradiance since October 1991. This 13 year time period includes a
secondary maximum of solar cycle 22, the ensuing solar minimum, the
maximum of solar cycle 23, and its declining phase. SUSIM maintains
the calibration of its changing responsivity through a combination
of measurements of four stable onboard deuterium calibration lamps
and measurements of infrequently exposed reference channels. The
wavelength-dependent UV irradiance time series exhibit two dominant
periodicities, that of solar rotation (27~days) and solar cycle
(11~years). The solar cycle variation of the UV irradiance was similar
for solar cycles~22 and 23: about 55% at Ly-α , about 7% at 205~nm,
and less than 1% above 300~nm. The SUSIM measurements are compared with
other coincident measurements including those of SOLSTICE over a similar
time period and with the Mg~II core-to-wing ratio index. Prospects
and requirements for continued and possibly improved monitoring of
the solar UV irradiance are discussed.
---------------------------------------------------------
Title: The center-to-limb behavior of solar active regions at
ultraviolet wavelengths
Authors: Crane, P. C.; Floyd, L. E.; Cook, J. W.; Herring, L. C.;
Avrett, E. H.; Prinz, D. K.
2004A&A...419..735C Altcode:
The time series of solar ultraviolet irradiances measured by the
Solar Ultraviolet Spectral Irradiance Monitor on the Upper Atmosphere
Research Satellite have been analyzed to describe the center-to-limb
behavior of the excess surface brightness of solar active regions
over the wavelength range 142-265 nm. Comparison of these results
with the analysis by Worden, Woods, and Bowman (2001, ApJ, 560, 1020)
of the time series produced by the Solar-Stellar Irradiance Comparison
Experiment on the same spacecraft over the wavelength range 120-170 nm
shows excellent agreement. For 170-265 nm, we present new results on
the center-to-limb behavior of the surface brightness of solar active
regions. Comparisons with previous results for the quiet disk show
roughly similar behaviors at wavelengths below 168 nm and above 210 nm,
where both exhibit weak limb brightening and darkening, respectively. At
intermediate wavelengths, 168-210 nm, active regions exhibit much
stronger limb darkening than does the quiet disk. Our Fourier analysis
and the multi-component modeling of Worden et al. (2001, ApJ, 560, 1020)
are found to be complementary and could be productively combined in
future work. We also compare our results with a similar analysis based
upon the semi-empirical model atmospheres of Fontenla et al. (1999,
ApJ, 518, 480), further improved by Avrett. We compare the measurement-
and model-based analyses and suggest the direction of improvements
needed in the model atmospheres.
---------------------------------------------------------
Title: The Secchi Experiment on the Stereo Mission
Authors: Howard, R.; Moses, D.; Socker, D.; Cook, J.; Davila, J.;
Lemen, J.; Harrison, R.; Eyles, C.; Waltham, N.; Defise, J. -M.
2004cosp...35.3893H Altcode: 2004cosp.meet.3893H
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of remote sensing instruments consisting of two
white light coronagraphs, an extreme ultraviolet (EUV) imager, and
a heliospheric imager. SECCHI will observe coronal mass ejections
(CMEs) from their birth at the sun, through the corona and into the
heliosphere. A complete instrument suite is being carried on each
of the two STEREO spacecraft, which will provide the first sampling
of a CME from two vantage points. The spacecraft will orbit the Sun,
one ahead of the Earth and the other behind, separating from Earth at
about 22 degrees per year. The varying separation means that we will
have different observational capabilities as the spacecraft separate
and therefore differing science goals. The primary science objectives
all are focused on understanding the physics of the CME process -
their initiation, 3D morphology, propagation, interaction with the
interplanetary medium and space weather effects. By observing the CME
from multiple viewpoints with UV and coronagraphic telescopes and by
combining these observations with radio and in-situ observations from
the other instruments on STEREO as well as from other satellites and
ground based observatories operating at the same time, answers to some
of the outstanding questions will be obtained.
---------------------------------------------------------
Title: Model for 3-D Heliospheric EUV Irradiance and Photoionization
Authors: Auchère, F.; McMullin, D.; Cook, J.; Newmark, J.; Vonsteiger,
R.; Witte, M.; Quémerais, E.
2004cosp...35.2558A Altcode: 2004cosp.meet.2558A
For 8 years now, the EIT instrument on board SOHO continuously monitored
the solar activity in four passbands of the EUV spectrum. With the
SOHO mission extended, it is likely that the final EIT data set will
cover one complete solar cycle. This exceptional data set offers an
unprecedented opportunity to investigate the long-term variations of
the solar EUV irradiance. Furthermore, with the spatial resolution of
the EIT/SOHO instrument, the data can also be used to study variations
of the solar irradiance with heliocentric latitude. It is indeed
clear that the wide intensity range of the various emitting regions
(polar coronal holes, equatorial active regions, etc.) produces
a latitude-dependant irradiance. To date, due to the small number
of off-ecliptic measurements, very few attempts have been made to
investigate these variations. We present here an empirical model of the
EUV solar flux at any point in the heliosphere derived from EIT/SOHO
data. At 30.4 nm, the anisotropy I_⊥ / I_∥ between the irradiance
above (⊥) and within (∥) the ecliptic plane is found to range
from about 0.8 at solar minimum to about 0.6 at solar maximum. Our
anisotropic EUV fluxes are used to improve the present estimates of
the photoionization rate of in-flowing neutral helium. These new rates
are compared to the relative changes of neutral helium density measured
by the GAS/Ulysses instrument.
---------------------------------------------------------
Title: Solar UV and EUV Irradiance and Solar Indices
Authors: Floyd, L.; Newmark, J.; Herring, L.; Cook, J.; McMullin, D.
2003AGUFMSH12A1162F Altcode:
Studies of the solar UV (120--290~nm) spectral irradiance have shown
that its variation correlates well with that of the core-to-wing
ratio of the Mg~II compound absorption feature near 280~nm. The two
chromospheric emission lines in the feature's core cause nearly
all of the Mg~II index variation. The Mg~II index has also been
shown to correlate with solar He~II emerging from the transition
region. Although earlier studies appeared to show that an accurate
representation of the solar Ly-α irradiance required the separation
of the long- and short-term components of the Mg~II index, recently
recalibrated measurements show that Ly-α also has a linear relationship
with Mg~II. We analyze the solar spectral irradiance derived from
SOHO EIT images roughly corresponding to coronal line emissions of
Fe~IX/X, Fe~XII, and Fe~XV and find that the Mg~II index represents
their variation more effectively than the more commonly used F10.7~cm
flux. The long-term behavior of F10.7, Mg~II, and sunspot number are
compared showing a strong divergence of the latter during the latter
stages of the solar cycle~23 maximum.
---------------------------------------------------------
Title: Obituary: Dianne K. Prinz, 1938-2002
Authors: Cook, John William; Howard, Russell Alfred
2003BAAS...35.1469C Altcode:
Dr. Dianne Kasnic Prinz died 12 October 2002 at the Hospice of Northern
Virginia after a long struggle with lymphatic cancer. She worked
for over 29 years until retirement at the Naval Research Laboratory
in Washington, DC on sounding rocket, space shuttle, and satellite
experiments to observe the Sun at ultraviolet wavelengths from space. <P
/>Dianne Prinz was born 29 September 1938. She received her BS degree
from the University of Pittsburgh in 1960, and a PhD in Physics from
Johns Hopkins University in 1967, where she was a University Fellow
1960--1964 and a Gilman Fellow 1960--1963. She was a Research Associate
in the Physics Department of the University of Maryland 1967--1971 and,
from 1971 until her retirement in February 2001, she was a Research
Physicist at the Naval Research Laboratory (NRL). At the time of her
retirement she was Head of the Solar Radiation Section, Solar Physics
Branch, Space Science Division of the Naval Research Laboratory and
was supervising the work of a team of scientists that was operating
the SUSIM (Solar Ultraviolet Irradiance Monitor) experiment on the UARS
(Upper Atmosphere Research Satellite) spacecraft as well as reducing and
analyzing the observations. <P />Dianne was a member of the Washington
Academy of Science (elected 1976 and Fellow 1987), served as Vice
President of the National Capital Section of the Optical Society
of America (1976), and received the Navy Award of Merit for Group
Achievement (1985), the NASA Public Service Group Achievement Award
(1987), and the Navy Meritorious Civilian Service Award (2001). Her
professional memberships included the American Astronomical Society and
its Solar Physics Division, the American Geophysical Union, and Sigma
Xi. She had over 60 publications in her scientific bibliography. <P
/>Early in her career at NRL, Dianne developed a Lyman alpha
spectroheliograph sounding rocket payload. Launching at White Sands
Missile Range in 1972, she obtained high spatial resolution (for that
day) full disk solar images. Her published analysis was pioneering
for the study of the Lyman alpha irradiance and established the range
of brightness of solar active regions relative to the quiet disk. <P
/>Dianne also had a keen interest in understanding how the upper
atmosphere responds to changing solar conditions, a field of research
now called “space weather." Early in her career she collaborated with
NRL scientists Robert Meier and Phillip Mange on the analysis of some
of the first satellite remote sensing observations of the atmosphere
and ionosphere. That work laid the foundation for many future NASA and
DoD space weather programs, and throughout the years she continued to
participate in the design of atmospheric remote sensing instruments
that are flying in space today. <P />In 1978 Dianne was selected by
NASA to train as a Payload Specialist astronaut to operate the solar
instruments that were to fly on the Spacelab 2 mission aboard the
Space Shuttle. From a group of four in training (the others were
Drs. J.D.-F. Bartoe, Loren Acton, and George Simon), Bartoe and
Acton were finally selected and flew on the Spacelab 2 mission in
1985, when Dianne served as mission communicator with the Payload
Specialists. She and Simon were due to fly on a planned follow-up
second flight but the aftermath of the explosion of the Challenger
Space Shuttle shortly afterward led to cancellation and the end of
this phase of her career. In addition to the scientific aspects of her
work, she made a substantial effort to communicate her enthusiasm to
the public. After the Spacelab 2 mission she often gave presentations
to adult and student audiences on her experiences, sometimes bringing
along her flight suit. She received letters from all over the world from
correspondents who had read of her role. <P />Dianne was a member of
the team at NRL that developed the requirements for a new instrument to
accurately monitor, over many years, the solar ultraviolet irradiance,
which was known to vary considerably and is a crucial input to many
processes in the Earth's upper atmosphere. It was critical to overcome
the challenge of maintaining the absolute calibration of an ultraviolet
spectrometer. The new instrument, called the Solar Ultraviolet Spectral
Irradiance Monitor (SUSIM), was flown first on an early Space Shuttle
flight (STS-3) and next on the NASA Spacelab 2 mission, for which she
had trained as an astronaut payload specialist. The SUSIM design was
then revised for a long-term flight aboard the Upper Atmosphere Research
Satellite (UARS). After the launch in 1991 of the UARS SUSIM, she led
the NRL team that ran the UARS SUSIM flight operations and developed
the data analysis software. After the death of Guenter Brueckner,
she became the Principal Investigator of UARS SUSIM and continued the
operation, analysis, and publication of these critical scientific
observations. To determine the SUSIM absolute calibration, careful
studies were performed to separate the degradation of the instrument
response from the true solar variability. Extensive work was necessary
to model the degradation of the instrumental sensitivity with time,
the stray light correction, the field-of-view correction, and the
wavelength scale. Dianne managed these tasks and produced a long term,
well-calibrated history of solar ultraviolet irradiances over the full
activity levels of a solar cycle. <P />Dianne grew up on a farm in
southwestern Pennsylvania, the daughter of Joseph J. Kasnic, a steel
worker and part-time farmer, and Anna M. Kosyrich Kasnic, a homemaker,
part-time teacher and accomplished artist and musician. Diane will
be remembered for her deep love of animals, whether her beloved horse
Chesterfield or stray or hungry cats in her neighborhood. Her marriage
to Dr. Gary Prinz ended in divorce. She is survived by her sister and
brother. Diane had an early interest in science and, throughout her
career, worked as an experimental physicist and designer of optical
instrumentation. She was a pioneer in her interests in space science,
and usually overcame the obstacles she encountered in her field and at
a time when she was often the first woman in authority encountered by
male co-workers. She had a no-nonsense attitude in her work relations,
but inspired the friendship of colleagues through her genuine good will,
competence, and utter lack of pretension.
---------------------------------------------------------
Title: Investigations on the behaviour of Re on the site of Maqarin
(Jordan)
Authors: Trotignon, L.; Khoury, H.; Bienvenu, P.; Cook, J.; Mercier,
F.; Trocellier, P.; Provitina, L. Raimbault O.; Arnal, N.; Adam, F.
2003GeCAS..67R.492T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: SUSIM'S 11-year observational record of the solar UV irradiance
Authors: Floyd, L. E.; Cook, J. W.; Herring, L. C.; Crane, P. C.
2003AdSpR..31.2111F Altcode:
The Solar Ultraviolet Spectral Irradiance Monitor (SUSIM), a
wavelength-scanning, dual-dispersion, dual-spectrometer instrument
aboard the Upper Atmosphere Research Satellite (UARS), has measured
the solar ultraviolet (UV) spectral irradiance (115-410 nm) since
October 1991. This 11-year period, the duration of a solar activity
cycle, extends from a late secondary maximum of solar cycle 22
through the intervening solar minimum and the maximum of solar cycle
23. Accordingly, SUSIM observed nearly the entire maximum-to-minimum
variation of the solar UV irradiance of both solar cycles. The UV
irradiance variations during the two solar cycles are compared. Apart
from solar rotation effects and to within experimental accuracy,
they show similar variation in the UV spectral irradiance. Solar cycle
amplitudes calculated after removing solar rotation effects were ∼50%
for the strong O I, C II, and Si IV emission features below 145 run,
∼8-18% between the A1 edge and 145 nm, respectively, and ∼4%
between the Al edge and 263 nm. The amplitude of the solar cycle
periodicity was not detected above ∼300 nm.
---------------------------------------------------------
Title: 3D Electron Density Reconstruction from the SECCHI White
Light Coronagraphs Onboard Stereo
Authors: Newmark, J. S.; Cook, J. W.; Reiser, P. A.; Yahil, A.
2003SPD....34.0202N Altcode: 2003BAAS...35..807N
The twin STEREO spacecraft will carry onboard the SECCHI (Sun-Earth
Connection Coronal and Heliospheric Investigation) experiment,
consisting of an EUVI disk imager and three white light coronagraphs on
each spacecraft. At NRL we are investigating the tomographic electron
density reconstructions, and their limitations, that are achievable
from just two viewpoints using the coronagraph observations. We discuss
our reconstruction technique and show results from our current work. We
started with geometrically simple constant density objects (cylinders,
half-shells), and have proceeded on to several CME numerical models we
have obtained from cooperating colleagues. We render from the starting
known electron density distribution a perfect white light image, in
radial and tangential polarizations, typically from two viewpoints in
the elliptic plane, and then add noise. Using these input synthetic
observations, we employ our PIXON reconstruction technique to produce
a best (using fewest PIXON elements) electron density reconstruction
that reproduces the input images. We discuss the agreement of the
PIXON reconstructions with the known starting model electron density
distributions which produced the input images. We are particularly
interested in the limitations present when only two viewpoints are
available. The reconstructions are significantly improved with the
addition of a third viewpoint to the reconstruction, such as could be
provided during the STEREO mission by an operating LASCO coronagraph
on the SOHO spacecraft. Information on our project can be found from
the web site http://stereo.nrl.navy.mil. This work is supported by
NASA under S-13631-Y, and by the Office of Naval Research. The SECCHI
experiment is an international collaboration led by the Naval Research
Laboratory.
---------------------------------------------------------
Title: Solar EUV Variability as Measured by SOHO EIT and Future
Application to SDO SHARPP
Authors: Newmark, J.; Cook, J.; McMullin, D.
2003EAEJA....13798N Altcode:
The SOHO EIT instrument obtains full disk images of the Sun through four
channels; Fe IX,X (17.1nm), Fe XII (19.5nm), Fe XV (28.4nm), and He II
(30.4nm). We construct a model differential emission measure (DEM) map,
using the EIT images from the four channels, which accurately covers
the temperature range 80,000 - 2.2 MK. Using our DEM modeling tool we
calculate full disk EUV irradiances over the SOHO mission lifetime. The
accuracy of our model is demonstrated with a long term comparison to
the SOHO SEM instrument full disk irradiances. We provide a public
database (SOHO EIT website) of daily, full disk, full resolution
DEM maps from the SOHO EIT data as well as the software to create
these maps. Software tools are made available in order to extract
the irradiance for any EUV line, or defined passband, or calibrated
spectra (using the CHIANTI atomic physics package) for full disk, or
smaller regional average, over the entire field of view. The solar EUV
variability is an important driver to geospace. Model irradiances from
the DEM tools we have developed can be directly applied to thermospheric
and ionospheric models, and as input into empirical models such as
SOLAR2000 (Tobiska 2000), or used as an effective activity index for
such modeling. As part of the public database, we provide a daily EUV
irradiance spectrum (covering from 17-35 nm, 1 nm bins) covering the
SOHO mission. Lastly, we have begun preliminary work in applying our
DEM technique to the upcoming SDO SHARPP instrument. The increased
temperature (emission line) coverage for this instrument, especially
for the transition region, greatly enhances the fidelity of our models.
---------------------------------------------------------
Title: Measurements of Three-dimensional Coronal Magnetic Fields
from Coordinated Extreme-Ultraviolet and Radio Observations of a
Solar Active Region Sunspot
Authors: Brosius, Jeffrey W.; Landi, Enrico; Cook, John W.; Newmark,
Jeffrey S.; Gopalswamy, N.; Lara, Alejandro
2002ApJ...574..453B Altcode:
We observed NOAA Active Region 8108 around 1940 UT on 1997 November 18
with the Very Large Array and with three instruments aboard the NASA/ESA
Solar and Heliospheric Observatory satellite, including the Coronal
Diagnostic Spectrometer, the EUV Imaging Telescope, and the Michelson
Doppler Imager. We used the right-hand and left-hand circularly
polarized components of the radio observing frequencies, along with
the coordinated EUV observations, to derive the three-dimensional
coronal magnetic field above the region's sunspot and its immediate
surroundings. This was done by placing the largest possible harmonic
(which corresponds to the smallest possible magnetic field strength)
for each component of each radio frequency into appropriate atmospheric
temperature intervals such that the calculated radio brightness
temperatures at each spatial location match the corresponding
observed values. The temperature dependence of the derived coronal
magnetic field, B(x,y,T), is insensitive to uncertainties on the
observed parameters and yields field strengths in excess of 580 G
at 2×10<SUP>6</SUP> K and in excess of 1500 G at 1×10<SUP>6</SUP>
K. The height dependence of the derived coronal magnetic field,
B(x,y,h), varies significantly with our choice of magnetic scale height
L<SUB>B</SUB>. Based on L<SUB>B</SUB>=3.8×10<SUP>9</SUP> cm derived
from the relative displacements of the observed radio centroids, we
find magnetic field strengths in excess of 1500 G at heights of 15,000
km and as great as 1000 G at 25,000 km. By observing a given target
region on several successive days, we would obtain observations at a
variety of projection angles, thus enabling a better determination of
L<SUB>B</SUB> and, ultimately, B(x,y,h). We compare coronal magnetic
fields derived from our method with those derived from a potential
extrapolation and find that the magnitudes of the potential field
strengths are factors of 2 or more smaller than those derived from our
method. This indicates that the sunspot field is not potential and that
currents must be present in the corona. Alfvén speeds between 25,000
and 57,000 km s<SUP>-1</SUP> are derived for the 1×10<SUP>6</SUP>
K plasma at the centroids of the radio observing frequencies. Filling
factors between 0.003 and 0.1 are derived for the 1×10<SUP>6</SUP>
K plasma at the centroids of the radio observing frequencies.
---------------------------------------------------------
Title: New Measurements of 3-D Sunspot Coronal Magnetic Fields From
Coordinated SOHO EUV and VLA Radio Observations
Authors: Brosius, J. W.; White, S. M.; Landi, E.; Cook, J. W.; Newmark,
J. S.; Gopalswamy, N.; Lara, A.
2002AAS...200.0307B Altcode: 2002BAAS...34..642B
Three-dimensional sunspot coronal magnetograms were derived from
coordinated extreme-ultraviolet (EUV) and radio observations of NOAA
regions 8108 (N21E18 on 1997 November 18) and 8539 (N20W12 on 1999 May
13). The EUV spectra and images, obtained with the Coronal Diagnostic
Spectrometer (CDS) and the Extreme-ultraviolet Imaging Telescope (EIT)
aboard the Solar and Heliospheric Observatory (SOHO) satellite, were
used to derive the differential emission measure (DEM) and the plasma
electron density for each spatial pixel (along each line of sight)
within both regions. These were subsequently used to calculate maps
of the expected thermal bremsstrahlung brightness temperature at the
Very Large Array (VLA) radio observing frequencies of 1.4, 4.9, 8.4,
and 15 GHz. The thermal bremsstrahlung maps reproduce neither the
structure nor the intensity of the observed maps, and indicate that
thermal gyroemission must dominate the observed radio emission. The
radio observations were used to constrain the magnetic scale height and
the gross temperature structure of the atmosphere. These, along with
the DEM, electron density, and observed radio brightness temperature
maps, were used to derive the temperature distribution of the coronal
magnetic field strength B(T) that reproduced simultaneously the observed
right-hand and left-hand circularly polarized emission at the radio
observing frequencies for each spatial pixel in the images. Magnetic
field strengths corresponding to 3rd harmonic gyroemission at 4.9 GHz
(580 Gauss) are found in coronal plasmas at temperatures as high as
3.2 MK, while magnetic field strengths corresponding to 3rd harmonic
gyroemission at 15 GHz (1800 Gauss) are found in coronal plasmas at
temperatures as high as 1.6 MK. B(T) was ultimately converted to B(h)
and compared with extrapolations from photospheric magnetograms.
---------------------------------------------------------
Title: Sun earth connection coronal and heliospheric investigation
(SECCHI)
Authors: Howard, R. A.; Moses, J. D.; Socker, D. G.; Dere, K. P.;
Cook, J. W.; Secchi Consortium
2002AdSpR..29.2017H Altcode:
The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI)
on the NASA Solar Terrestrial Relations Observatory ( STEREO) mission
is a suite of remote sensing instruments consisting of an extreme
ultraviolet imager, two white light coronagraphs, and a heliospheric
imager. Two spacecraft with identical instrumentation will obtain
simultaneous observations from viewpoints of increasing separation
in the ecliptic plane. In support of the STEREO mission objectives,
SECCHI will observe coronal mass ejections from their birth at the Sun,
through the outer corona, to their impact at Earth. The SECCHI program
includes a coordinated effort to develope magneto-hydrodynamic models
and visualization tools to interpret the images that will be obtained
from the two spacecraft viewpoints. The resulting three-dimensional
analysis of CMEs will help to resolve some of the fundamental
outstanding questions in solar physics.
---------------------------------------------------------
Title: SUSIM s 11-year Observational Record of the Solar UV Irradiance
Authors: Floyd, L.; Cook, J.; Herring, L.; Crane, P.
2002cosp...34E.687F Altcode: 2002cosp.meetE.687F
The Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) aboard the
Upper Atmosphere Research Satellite (UARS) has measured the solar
UV spectral irradiance since October 1991. This 11-year solar cycle
length period extends from a late secondary maximum of solar cycle~22
through the intervening solar minimum and ensuing maximum of solar
cycle~23. Accordingly, SUSIM observed nearly the entire UV variation
of both solar cycles. As is common for UV irradiance measurements,
continuous instrumental responsivity changes during the experiment
complicate irradiance determinations. SUSIM uses deuterium lamps
and redundant optical channels to determine the changes in its
responsivity since its last calibration before flight. The Mg~II
coreto-wing ratio index, less resistant to these responsivity changes,
is also measured. Accordingly, it has become a well used proxy for UV
and even EUV variations at other wavelengths. Cyclic variations are
mainly observed having periods corresponding to solar rotation and the
solar cycle. The amplitude of these variations tend to be greater for
shorter wavelengths and for emission lines. We explore the level of
correspondence between the Mg~II index time series and those of the UV
spectral irradiances. The wavelengthdependent variation of each of the
two solar cycles is also are derived and compared. Intercomparisons
with UV measurements from other experiments are presented, aiding in
our understanding of both solar and instrumental effects.
---------------------------------------------------------
Title: Solar UV Spectral Irradiance Variation During Solar Cycle 23
Authors: Floyd, L. E.; Cook, J. W.; Crane, P. C.; Herring, L. C.
2001AGUFM.A51E0087F Altcode:
The Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) aboard the
UARS has measured the solar spectral irradiance at UV wavelengths in
the 115-410 nm range since October 1991. This period extends from
a secondary maximum of solar activity before the decline of solar
cycle~22, through the intervening solar minimum, and through the
solar cycle~23 maximum. Accordingly, SUSIM has observed nearly the
entire UV variation of both solar cycles. SUSIM uses deuterium
lamps and redundant optical channels to determine changes in
its responsivity since its final ground calibration more than
ten years before the latest measurements. The new results for the
wavelength-dependent variation of the solar UV spectral irradiance
during solar cycle~23 will be presented. Trends in solar irradiance
and in possible error sources are identified and analyzed. Emphasis
will be placed on comparisons with variations observed during solar
cycle~22 and on their relationship with solar indices (such as the
MgII core-to-wing ratio). The rationale for continuing redundant
and overlapping measurements of the solar UV irradiance will be
provided. >http://wwwsolar.nrl.navy.mil/susim_uars.html</a>
---------------------------------------------------------
Title: Particles on Titan from the Stratopause to the Troposphere
Authors: Griffith, C. A.; Hall, J. L.; Young, E. F.; Cook, J.;
Rannou, P.
2001DPS....33.5301G Altcode: 2001BAAS...33.1135G
We investigate Hubble Space Telescope images of three separate sources
of particulates that vary temporally and spatially across Titan's
disk. (1) North-south variations of Titan's albedo occur at visible
wavelengths that result from seasonal changes in the number density
of haze at Titan's stratopause (roughly 250 km altitude). The phase
lag in these periodic variations match that of Titan's temperature
field and support the hypothesis that the thermal profile reacts in
concert with the wind field through the wind gradient equation. This
coupling causes the thermal field to adjust to seasonal changes at a
dynamical time scale of approximately 5 years, much longer than the
radiative time scale. (2) Images at longer wavelengths (0.7-1 um)
indicate the presence of particles near Titan's tropopause and lower
stratosphere at high southern latitudes. The nature of these particles
is unclear. Their absence at northern latitudes precludes a purely
circulation origin. Their lack of measurable change from 1994 to
2000, precludes convective origins. (3) We detect one occurrence of a
brightening at Titan's equator, unrelated to the stratosphere and the
surface. Judging by its temporal nature and altitude of 20-40 km, this
may an image of methane condensation clouds in Titan's atmosphere. This
research is supported by the NASA Planetary Astronomy Program and the
Hubble Space Telescope Program.
---------------------------------------------------------
Title: High-resolution Imaging of the Upper Solar Chromosphere:
First Light Performance of the Very-high-Resolution Advanced
ULtraviolet Telescope
Authors: Korendyke, C. M.; Vourlidas, A.; Cook, J. W.; Dere, K. P.;
Howard, R. A.; Morrill, J. S.; Moses, J. D.; Moulton, N. E.; Socker,
D. G.
2001SoPh..200...63K Altcode:
The Very-high-resolution Advanced ULtraviolet Telescope (VAULT)
experiment was successfully launched on 7 May 1999 on a Black Brant
sounding rocket vehicle from White Sands Missile Range. The instrument
consists of a 30 cm UV diffraction limited telescope followed by a
two-grating, zero-dispersion spectroheliograph tuned to isolate the
solar Lα emission line. During the flight, the instrument successfully
obtained a series of images of the upper chromosphere with a limiting
resolution of ∼ 0.33 arc sec. The resulting observations are the
highest-resolution images of the solar atmosphere obtained from space
to date. The flight demonstrated that sub-arc second ultraviolet
images of the solar atmosphere are achievable with a high-quality,
moderate-aperture space telescope and associated optics. Herein,
we describe the payload and its in-flight performance.
---------------------------------------------------------
Title: Solar EUV Variability as Measured by SOHO/EIT: Comparison to
SOHO SEM and He II 304, Case Studies
Authors: Newmark, J. S.; Cook, J. W.; McMullin, D. R.
2001AGUSM..SP32B06N Altcode:
The specification of soft X-ray and EUV solar flux is important because
it is the main ionizing source for the ionosphere and the EUV energy
deposit is primarily responsible for the structure and dynamics of the
thermosphere. The EIT instrument aboard SOHO obtains full disk images
of the Sun through four channels at Fe IX,X (171 A), Fe XII (195 A),
Fe XV (284 A), and He II (304 A). We construct a model differential
emission measure (DEM) map, using calibrated SOHO EIT images from the
four channels which accurately covers the temperature range 80,000
- 2.2 MK. We use the DEM map to calculate absolutely calibrated
images of individual lines or passbands in addition to the four EIT
channels. As a case study of the power of this technique we present
a long term comparision (1996-2000) to the SOHO SEM instrument full
disk irradiances. Additionally we produce a pure He II (304 A) solar
irradiance for the entire SOHO EIT mission. This irradiance, covering
a large part of a solar cycle can provide a fundamental parameter to
compare with Earth's atmospheric variations.
---------------------------------------------------------
Title: In-flight Calibration of SOHO EIT
Authors: Newmark, J. S.; Cook, J. W.; Auchere, F.; Moses, J. D.;
Clette, F.
2001AGUSM..SP21B06N Altcode:
The SOHO EIT response has varied both temporally and spatially
throughout the mission. A large effort has been put forth into
understanding instrument responsivity changes, the spectral response
and absolute calibration. The latter two have been completed (Dere et
al. 2000, Newmark 2000). The response degradation process consists of
several components which are difficult to separate in detail. The two
basic processes contributing to the degradation are 1) the absorption
of EUV before it interacts with the CCD by a surface contaminant plus
possible blackening of the entrance filter and 2) the reduction of
charge collection efficiency (CCE) in the CCD due to EUV induced device
damage. A method utilizing the in-flight calibration lamps has been
developed which accurately characterizes the sensitivity changes. We
present absolutely calibrated SOHO EIT data from 1996 - 2000.
---------------------------------------------------------
Title: Limb Brightening and Darkening of Solar Active Regions at
Ultraviolet Wavelengths Determined from UARS/SUSIM Ultraviolet
Irradiance Measurements
Authors: Crane, P. C.; Floyd, L. E.; Herring, L. C.; Cook, J. W.;
Prinz, D. K.
2001AGUSM..SP32B04C Altcode:
We report the first quantitative measurements of the limb brightening
and darkening of solar active regions at ultraviolet wavelengths, based
upon Fourier analysis of the rotationally modulated mid-resolution
(1.1- nm) ultraviolet irradiances measured by the Solar Ultraviolet
Spectral Irradiance Monitor (SUSIM) on the Upper Atmospheric Research
Satellite (UARS). Significant results have been obtained for the
wavelength range 142-265 nm. We find weak limb brightening at short
wavelengths and weak, perhaps insignificant, limb darkening at long
wavelengths. Sharp transitions occur at the Si I and Al I edges at
168.2 nm and 207.6 nm, respectively, which bound a region of strong
limb darkening. The quiet disk also exhibits weak limb brightening
at short wavelengths, but has transitions to weak/medium and medium
limb darkening at the Si I and Al I edges at 152.1 nm and 207.6 nm,
respectively. Analysis of the Ly- (121.6 nm) index illustrates how
the field-of-view response can introduce a significant instrumental
effect to such measurements. This work was supported by NASA-Defense
Purchase Requests S14798D and S10108X.
---------------------------------------------------------
Title: Measurements of 3-D Sunspot Coronal Magnetic Fields From
Coordinated SOHO EUV and VLA Radio Observations
Authors: Brosius, J. W.; Landi, E.; Cook, J. W.; Newmark, J.;
Gopalswamy, N.; Lara, A.
2001AGUSM..SH32C02B Altcode:
Three-dimensional sunspot coronal magnetograms were derived from
coordinated extreme-ultraviolet (EUV) and radio observations of
NOAA region 8108 (N21 E18) on 1997 November 18. The EUV spectra
and images, obtained with the Coronal Diagnostic Spectrometer (CDS)
and the Extreme-ultraviolet Imaging Telescope (EIT) aboard the Solar
and Heliospheric Observatory (SOHO) satellite, were used to derive
differential emission measure (DEM) distributions for each spatial
pixel (i.e., along each line of sight) of the region's images. These
were subsequently used to calculate maps of the expected thermal
bremsstrahlung brightness temperature at the Very Large Array
(VLA) radio observing frequencies of 4.9 and 8.4 GHz. The thermal
bremsstrahlung maps reproduce neither the structure nor the intensity
of the observed maps, and indicate that thermal gyroemission must
also contribute to the observed radio emission. Under the assumptions
of a monotonic increase in temperature and a monotonic decrease in
magnetic field strength with height above the sunspot, we derived
the temperature distribution of the coronal magnetic field strength
that reproduced simultaneously the observed right-hand and left-hand
circularly polarized radio emission at 4.9 and 8.4 GHz for each
spatial pixel in the sunspot maps. This was done by placing harmonics
of the radio observing frequencies in appropriate plasma temperature
intervals, integrating along the line of sight, and iterating until
a solution was obtained. Magnetic field strengths corresponding to
3rd harmonic gyroemission at 4.9 GHz (580 Gauss) are found in coronal
plasmas at temperatures as high as 2.2*E<SUP>6</SUP> K, while magnetic
field strengths corresponding to 2nd harmonic gyroemission at 8.4 GHz
(1500 Gauss) are found in coronal plasmas at temperatures as high as
1.1*E<SUP>6</SUP> K.
---------------------------------------------------------
Title: Comparison of Sac Peak Fe XIV Index with Model Index Computed
from EIT Differential Emission Measure Maps
Authors: Cook, J. W.; Newmark, J. S.; Altrock, R. C.
2001AGUSM..SP32B05C Altcode:
We compare the Sac Peak Fe XIV green line index with a model index time
series for the period of operations of the Extreme-ultraviolet Imaging
Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO),
covering the years 1996-2000, from cycle minimum to the peak of the
current activity cycle 23. We compute a differential emission measure
(DEM) map for each day using images from the four channels of EIT at
171 Å, 195 Å, 284 Å, and 304 Å. From the daily DEM map we then
calculate a daily Fe XIV 5304 Å intensity image (see Cook et al. 1999,
Proceedings of the 8th SOHO Workshop, ESA SP-446, pp. 241-246). The
Sac Peak index is an average intensity, measured using a circular
aperture 1 arcmin in diameter sampling the corona in 1 degree steps
around disk center. It is taken at several different heights beyond
the daily limb. We modeled the index values, for the aperture center
at 1.15 R<SUB>odot</SUB> from disk center, as the average intensity
within a daily annulus covering 1.12 - 1.18 R<SUB>odot</SUB> imposed on
the model intensity image. We compare the observed index with our model
results, and discuss in terms of the accuracy of the model intensities
which can be determined from our EIT-based DEM curves. We actually
produce a daily Fe XIV image for the entire EIT field-of-view. The
Sac Peak index provides one well calibrated, long term check on the
reliability of the DEM model calculation. This work has been supported
by NASA under W-19,348, and by the Office of Naval Research.
---------------------------------------------------------
Title: Book Review: Observing the moon / Springer, 2000
Authors: Cook, J.
2001JBAA..111Q.110C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: School Cosmic Ray Outreach Detector (SCROD)
Authors: Anchordoqui, L.; Cook, J.; MacLeod, J.; McCauley, T.;
Moussienko, I.; Paul, T.; Reucroft, S.; Swain, J.; Terry, R.
2001ICRC....2..788A Altcode: 2001ICRC...27..788A; 2001hep.ex....6002A
We report on our studies of applying novel detector technologies
developed for LHC-era experiments to cosmic ray detection. In
particular, we are investigating usage of scintillating tiles with
embedded wavelength-shifting fibers and avalanche photodiode readout
as part of a robust, inexpensive cosmic air shower detector. In the
near future, we are planning to deploy detector stations based on this
technology at area high schools and colleges as part of an outreach
and education effort, known as SCROD.
---------------------------------------------------------
Title: Calibration and flight of the NRL EIT CalRoc
Authors: Newmark, Jeffrey S.; Moses, J. Daniel; Cook, John W.;
Delaboudiniere, Jean-Pierre; Song, Xueyan; Carabetian, Charles;
Bougnet, Marie; Brunaud, Jacqueline; Defise, Jean-Marc; Clette,
Frederic; Hochedez, Jean-Francois E.
2000SPIE.4139..328N Altcode:
The ability to derive physical parameters of the Sun from observations
by the Solar and Heliospheric Observatory (SOHO) Extreme Ultraviolet
Imaging Telescope (EIT) greatly increases the scientific return of the
mission. The absolute and time variable calibration of EIT therefore is
of extreme interest. The NRL EIT Calibration Sounding Rocket (CalRoc)
program was initiated to provide well calibrated, contemporaneous
observations in support of SOHO EIT. These observations provide
three benefits to the SOHO EIT data, absolute calibration points,
temporal and spatial information of the EIT EUV response variability
in flight via flat field information and clues to the physics of the
degradation. Details of the bandpasses of the multilayered optics and
the total telescope photometry are presented. Comparisons are shown
with the contemporaneous images from SOHO EIT. Plans for the second
CalRoc flight are discussed. Loss of reflectivity in the multilayer
mirrors has been identified as a new component to the SOHO EIT and
CalRoc degradation.
---------------------------------------------------------
Title: In-flight performance of the Very high Angular resolution
ULtraviolet Telescope sounding rocket payload
Authors: Korendyke, Clarence M.; Vourlidas, A.; Cook, John W.; Dere,
Kenneth P.; Feldman, R.; Howard, Russell A.; Lilley, D. N.; Morrill,
Jeff S.; Moses, J. Daniel; Moulton, Norman E.; Moye, Robert W.;
Roberts, D. E.; Shepler, E. L.; Smith, J. K.; Socker, Dennis G.;
Spears, T. R.; Waymire, R. S.; Brown, Wayne E.; Tarbell, Theodore D.;
Berger, Tom; Handy, Brian N.
2000SPIE.4139..340K Altcode:
The Very high Angular Resolution ULtraviolet Telescope experiment was
successfully launched on May 7, 1999 on a Black Brant sounding rocket
vehicle from White Sands Missile Range. The instrument consists of a
30 cm UV diffraction limited telescope followed by a double grating
spectroheliograph tuned to isolate the solar Lyman (alpha) emission
line. During the flight, the instrument successfully obtained a series
of images of the upper chromosphere with a limiting resolution of
approximately 0.33 arc-seconds. The resulting observations are the
highest resolution images of the solar atmosphere obtained from space
to date. The flight demonstrated that subarc-second ultraviolet images
of the solar atmosphere are achievable with a high quality, moderate
aperture space telescope and associated optics. Herein, we describe
the payload and its in- flight performance.
---------------------------------------------------------
Title: High Angular Resolution Studies of Coronal Structures with SOHO
Authors: Karovska, Margarita; Wood, Brian; Cook, John W.; Chen, James;
Howard, Russ
2000Ap&SS.273....7K Altcode:
Since January 1996, the Solar and Heliospheric Observatory (SOHO)
has been providing unprecedented views of the extended solar corona
to heliocentric distances of up to 32 solar radii. During the past
three years we carried out studies of the morphology and dynamical
evolution of various structures in the solar corona using two
instruments on board SOHO: the Large Angle Spectrometric Coronagraph
(LASCO) and the Extreme Ultraviolet Imaging Telescope (EIT). We have
applied advanced image resolution enhancement techniques to explore
in detail the characteristics of the small-scale structures and/or
the low contrast structures in the solar corona. We describe here the
results from these high-angular resolution studies, including of the
kinematics of several Coronal Mass Ejections and polar jets.
---------------------------------------------------------
Title: Exploring Coronal Structures with SOHO
Authors: Karovska, M.; Wood, B.; Chen, J.; Cook, J.; Howard, R.
2000JApA...21..403K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar EUV Variability as Measured by SOHO/EIT
Authors: Newmark, J. S.; Cook, J. W.; Moses, J. D.; Floyd, L. E.
2000SPD....31.0222N Altcode: 2000BAAS...32..814N
The EIT instrument aboard SOHO obtains full disk images of the Sun
through four channels at Fe IX,X (171 A), Fe XII (195 A), Fe XV (284
A), and He II (304 A). We construct a model differential emission
measure (DEM) map, using the EIT images from the four channels which
accurately covers the temperature range 80,000 - 2.2 MK. We use
the DEM map to calculate absolutely calibrated images of individual
lines or passbands in addition to the four EIT channels. The validity
of our model is shown with a long term comparision to the SOHO SEM
instrument full disk irradiances. An important application presented
here is the time history from 1996-2000 of the pure He II (304 A)
solar irradiance. Additional spatial and spectral comparisons can be
done using the SOHO CDS instrument and the SERTS rocket flight.
---------------------------------------------------------
Title: Model for Radio Thermal Emission at 328 and 1446 MHz from
EUV Observations
Authors: Cook, J. W.; Newmark, J. S.; Vourlidas, A.
2000SPD....31.0221C Altcode: 2000BAAS...32..814C
We have modeled the contribution to solar radio emission at 328 and
1446 MHz from free-free thermal bremsstrahlung emission, using a full
disk differential emission measure (DEM) map of the Sun. The DEM map
is produced from four EUV images (171 A, 195 A, 284 A, and 304 A)
for a selected day from the EIT instrument on the SOHO satellite,
using a method developed previously by Cook, Newmark, and Moses. The
EIT instrument images the Sun out to 1.4 R, with a pixel size of 2.6
arc sec and spatial resolution of 2 pixels. We perform the radiative
transfer calculation, determining the optical depth scale for free-free
emission and the emergent absolute intensity for each pixel in the
field-of-view using the individual DEM of that pixel, and transforming
integrals over the line-of-sight into integrals over temperature
via the DEM. We can compare our model calculation with the VLA radio
observations of Vourlidas from 1998 January 31. Our model is in good
agreement outside of active regions, where free-free emission should
truly be the dominant emission mechanism. In areas such as sunspots,
where the strong magnetic field leads to additional gyro resonance
radiation, the difference between the observed total intensity and our
calculated thermal component should be a good estimate of the nonthermal
gyro radiation. This work is supported by NASA under W-19,348 and by
the Office of Naval Research.
---------------------------------------------------------
Title: Search for Velocity Variations in Fe XIV 5304 A&ring
Coronagraph Observations Near Activity Minimum
Authors: Cook, J. W.; Socker, D. G.; Korendyke, C. M.; Howard, R. A.;
Brueckner, G. E.; Karovska, M.; Wood, B. E.
2000AdSpR..25.1883C Altcode:
The LASCO C1 coronagraph on the SOHO satellite observes the solar
corona from 1.1 to 3.0 Ro, and contains a Fabry-Perot interferometer
which can image the corona in the 1.8 million K Fe XIV green line. We
designed an observing program with reduced spatial coverage and reduced
profile coverage at only three wavelengths to study coronal heating
in off-limb structures at high temporal resolution. We illustrate the
observations from 31 March 1997 of a bright loop system above an active
region off the northeast limb
---------------------------------------------------------
Title: Coronal Thermal Structure from a Differential Emission Measure
Map of the Sun
Authors: Cook, J. W.; Newmark, J. S.; Moses, J. D.
1999ESASP.446..241C Altcode: 1999soho....8..241C
We have developed a procedure to produce a differential emission measure
(DEM) map of the Sun using images from the four channels of the EIT
instrument at 171 (Fe IX/X), 195 (Fe XII), 284 (Fe XV), and 304 A (He
II). We use images from the EIT CalRoc sounding rocket flight on 16
October 1997. Our DEM procedure could also be applied to calibrated SOHO
EIT images and to TRACE observations. We find a statistical relation
between brightness of solar features (for example in the 171 A image)
and increasing slope of the DEM in the temperature range log T =
5.5 to 6.0. In their thermal structure active regions are not just
areas brighter than quiet areas whose DEM distributions continue to
rise to even hotter temperatures, but have greater relative amounts of
hotter material to cooler material toward 1 M K and above than do quiet
areas. The DEM should not be modeled in terms of an average structure,
either plane parallel or with loop geometry. Since at least the time
of the SO82A spectroheliograph observations from Skylab it has been
clear that structures observed in the temperature range of any one
line differ from structures observed in a hotter or cooler line. Any
DEM distribution is obtained from intensity observations through all
structures in the line of sight, and is composed from the combined
individual DEM distributions of these structures. We interpret the DEM
map in terms of ensembles of individual loops of differing temperatures,
where the ensembles are characteristically different in quiet and
active areas of the Sun. This work is supported by NASA under DPR
S-92385-D and by the Office of Naval Research.
---------------------------------------------------------
Title: Kinematic Measurements of Polar Jets Observed by the
Large-Angle Spectrometric Coronagraph
Authors: Wood, B. E.; Karovska, M.; Cook, J. W.; Howard, R. A.;
Brueckner, G. E.
1999ApJ...523..444W Altcode:
We analyze polar jets observed by the Large-Angle Spectrometric
Coronagraph (LASCO) instrument aboard the Solar and Heliospheric
Observatory. The events studied here are from 1997 March 24 and
August 5. The main objective of our analysis is to determine whether
the jets' motions are consistent with ballistic behavior. Although
ballistic trajectories have some success in fitting the observed
kinematic motions, there is substantial evidence that gravity alone
is not regulating the movement of the jets. First of all, the August 5
events appear to exhibit slight accelerations rather than decelerations
above 3 R<SUB>solar</SUB>. Second, all the events studied here have
very similar velocities, suggesting that by the time the jets reach
the LASCO field of view, the jets have been incorporated into the
ambient solar wind. If this is the case, the jets could be very useful
as tracers of the solar wind at low heights in the Sun's polar regions.
---------------------------------------------------------
Title: Comparing the kinematic properties of CMEs observed by LASCO
and EIT with models of erupting flux ropes
Authors: Wood, B. E.; Karovska, M.; Chen, J.; Brueckner, G. E.; Cook,
J. W.; Howard, R. A.
1999AIPC..471..633W Altcode: 1999sowi.conf..633W
We present observations of three coronal mass ejections (CMEs) observed
by the LASCO and EIT instruments aboard the Solar and Heliospheric
Observatory. The three CMEs are from 1997 February 23, 1997 April 30,
and 1998 March 6. The February 23 CME is accompanied by a spectacular
prominence eruption and its leading edge reaches velocities of about
900 km s-1. The April 30 and March 6 CMEs have no apparent accompanying
prominence eruptions and attain more modest velocities of about 300
and 600 km s-1, respectively. Despite their kinematic differences, all
three CMEs have bright, roughly circular rims which can be interpreted
as marking the apexes of expanding magnetic flux ropes, and all three
can be tracked from their origins near the surface of the Sun out to
great distances. We compare the kinematic and morphological properties
of these CMEs with an MHD model of an erupting flux rope, and we find
that the CMEs can be successfully modeled in this manner.
---------------------------------------------------------
Title: LASCO observations of the solar polar regions
Authors: Karovska, M.; Wood, B. E.; Brueckner, G. E.; Cook, J. W.;
Howard, R. A.
1999AIPC..471..309K Altcode: 1999sowi.conf..309K
We describe our study of the dynamical properties of coronal structures
in the polar regions of the Sun using a sequence of 200 LASCO/C2
images. This sequence was designed to study polar outflows in general,
in both polar plumes and in interplume regions. The results of our
analyses show that such studies are complicated by the existence of
foreground material, especially when high latitude streamer material
rotates into the field of view. We also describe our analysis of the
kinematic properties of several polar jets. The results suggest that
polar jets might be used for studies of the outflow wind velocities
in coronal holes at heights above several solar radii.
---------------------------------------------------------
Title: Coronal Thermal Structure from a Differential Emission Measure
Map of the Sun
Authors: Cook, J. W.; Newmark, J. S.; Moses, J. D.
1999AAS...19410003C Altcode: 1999BAAS...31..996C
We have developed a procedure to produce a differential emission measure
(DEM) map of the Sun using images from the four channels of the EIT
instrument at 171 (Fe IX/X), 195 (Fe XII), 284 (Fe XV), and 304 A
(He II). We use images from the EIT CalRoc sounding rocket flight on
16 October 1997. Our DEM procedure could also be applied to calibrated
SOHO EIT images and to TRACE observations. We find that the slope of
the DEM distribution over the temperature range log T = 5.5 to 6.0 is
typically near +1 for quiet areas, but is +3/2 for active regions. In
their thermal structure active regions are not just areas brighter than
quiet areas whose DEM distributions continue to rise to even hotter
temperatures, but have greater relative amounts of hotter material
to cooler material toward 1M K and above than do quiet areas. The
DEM should not be modeled in terms of an average structure, either
plane parallel or with loop geometry. Since at least the time of the
SO82A spectroheliograph observations from Skylab it has been clear that
structures observed in the temperature range of any one line differ from
structures observed in a hotter or cooler line. Any DEM distribution
is obtained from intensity observations through all structures in
the line-of-sight, and is composed from the combined individual DEM
distributions of these structures. We interpret the DEM map in terms
of ensembles of individual loops of differing temperatures, where the
ensembles are characteristically different in quiet and active areas
of the Sun. This work is supported by NASA under DPR S-92385-D and by
the Office of Naval Research.
---------------------------------------------------------
Title: Comparison of Two Coronal Mass Ejections Observed by EIT and
LASCO with a Model of an Erupting Magnetic Flux Rope
Authors: Wood, B. E.; Karovska, M.; Chen, J.; Brueckner, G. E.; Cook,
J. W.; Howard, R. A.
1999ApJ...512..484W Altcode:
We present observations of two coronal mass ejections (CMEs) observed
by the LASCO and EIT instruments on board the Solar and Heliospheric
Observatory. One was observed on 1997 April 30 and the other on 1997
February 23. The latter CME is accompanied by a spectacular prominence
eruption and reaches velocities of about 900 km s<SUP>-1</SUP>, while
the former has no apparent accompanying prominence eruption and attains
velocities of only about 300 km s<SUP>-1</SUP>. However, the two CMEs
are similar in appearance, having bright circular rims that can be
interpreted as marking the apexes of expanding magnetic flux ropes,
and both can be tracked from their origins near the surface of the Sun
out to great distances. We compare the kinematic and morphological
properties of these CMEs with an MHD model of an erupting flux rope
and find that the CMEs can be successfully modeled in this manner.
---------------------------------------------------------
Title: Study of Dynamical Properties of Coronal Structures in the
Polar Regions
Authors: Karovska, Margarita; Wood, Brian E.; Cook, John W.; Howard,
Russell A.; Brueckner, Guenter E.
1999SSRv...87..219K Altcode:
We present the results from a study of the dynamical properties of
polar jets in the Sun's polar regions using LASCO C2 coronagraph and
EIT observations. In the simplest impulsive acceleration scenarios for
jets, gravity is expected to be the dominant force on the jet following
the initial acceleration, especially in the Sun's polar regions where
the open magnetic fields should not significantly impede the jet's
motion. Our analysis shows that although at low heights the kinematics
of the jets could be consistent with a gravitational deceleration of
the ejected plasma, at higher heights their motions may simply follow
the ambient solar wind outflow. If so, the polar jets can be used as
tracers of the solar wind in coronal holes.
---------------------------------------------------------
Title: Search for Brightness Variations in Fe XIV Coronagraph
Observations of the Quiescent Solar Corona
Authors: Wood, B. E.; Karovska, M.; Cook, J. W.; Brueckner, G. E.;
Howard, R. A.; Korendyke, C. M.; Socker, D. G.
1998ApJ...505..432W Altcode:
We use Fe XIV 5303 Å green line images obtained by the Large
Angle Spectrometric Coronagraph (LASCO) on board SOHO to search for
variability in the quiescent solar corona in the shortest observable
timescales. The observing program obtained Fe XIV images of a small
area of the inner corona every 2 minutes over a period of 1 hr. We
present results from two executions of this program taken several months
apart. The most obvious variability observed in the two sequences is
in the form of quasi-steady brightening on timescales of at least an
hour. Of particular interest are two compact loops that are observed to
vary significantly during the course of the observations. Superposed on
the long-term brightening in these loops are statistically significant
variations on timescales of about 30 minutes. In both loops, the overall
brightening is greatest at the apparent loop tops, where the intensity
increases by at least 25%. In one loop there appears to be a flow up
one of the legs of the loop. We place these observations in context with
earlier observations of coronal variability, and we discuss the energy
requirements for the observed brightening. Emission measures computed
from Fe XIV intensities measured within the two brightening loops are
over an order of magnitude lower than those typically found for active
regions on the solar disk, which suggests significantly lower average
densities. For one of the loops, we measure densities in the range
n<SUB>e</SUB> = (5.0-7.4) × 10<SUP>8</SUP> cm<SUP>-3</SUP>. Lower
than average densities are expected for the two loops, given that they
reach more than 1 pressure scale height above the solar limb.
---------------------------------------------------------
Title: Magnetic Sources of the Solar Irradiance Cycle
Authors: Lean, J. L.; Cook, J.; Marquette, W.; Johannesson, A.
1998ApJ...492..390L Altcode:
Using recently processed Ca K filtergrams, recorded with a 1 Å
filter at the Big Bear Solar Observatory (BBSO), we quantitatively
assess the component of solar irradiance variability attributable to
bright magnetic features on the Sun's disk. The Ca K filtergrams,
“flattened” by removing instrumental effects and center-to-limb
variations, provide information about bright sources of irradiance
variability associated with magnetic activity in both active regions and
dispersed active region remnants broadly distributed in the supergranule
network (termed collectively “faculae”). Procedures are developed
to construct both total and UV spectral solar irradiance variations
explicitly from the processed Ca K filtergrams, independently of
direct irradiance observations. The disk-integrated bolometric and
UV facular brightness signals determined from the filtergrams between
late 1991 and mid-1995 are compared with concurrent solar irradiance
measurements made by high-precision solar radiometers on the Upper
Atmosphere Research Satellite (UARS). The comparisons suggest that
active-region and active-network changes can account for the measured
variations. This good agreement during a period covering most of the
decline in solar activity from the cycle 22 maximum to the impending
solar minimum directly implicates magnetic features as the sources
of the 11 yr irradiance cycle, apparently obviating the need for an
additional component other than spots or faculae.
---------------------------------------------------------
Title: White-Light Coronal Mass Ejections: A New Perspective from
LASCO
Authors: St. Cyr, O. C.; Howard, R. A.; Simnett, G. M.; Gurman, J. B.;
Plunkett, S. P.; Sheeley, N. R.; Schwenn, R.; Koomen, M. J.; Brueckner,
G. E.; Michels, D. J.; Andrews, M.; Biesecker, D. A.; Cook, J.; Dere,
K. P.; Duffin, R.; Einfalt, E.; Korendyke, C. M.; Lamy, P. L.; Lewis,
D.; Llebaria, A.; Lyons, M.; Moses, J. D.; Moulton, N. E.; Newmark,
J.; Paswaters, S. E.; Podlipnik, B.; Rich, N.; Schenk, K. M.; Socker,
D. G.; Stezelberger, S. T.; Tappin, S. J.; Thompson, B.; Wang, D.
1997ESASP.415..103S Altcode: 1997cpsh.conf..103S
No abstract at ADS
---------------------------------------------------------
Title: LASCO Observations of Variability in the Quiescent Solar Corona
Authors: Wood, B. E.; Karovska, M.; Cook, J. W.; Brueckner, G. E.;
Howard, R. A.
1997AAS...191.7303W Altcode: 1997BAAS...29Q1321W
We discuss the localized small scale coronal variability detected
in observations made by the Large Angle Spectrometric Coronagraph
(LASCO) onboard SOHO. The LASCO C1 coronagraph was used to take images
of small portions of the solar corona located in the streamer belt
between roughly 1.1 and 2.0 R<SUB>sun</SUB>. Two sets of images were
obtained several months apart. Each set contains images taken with
LASCO's Fabry-Perot interferometer centered on the Fe XIV lambda 5303
line, and in the nearby continuum. The images were obtained about once
every minute. Significant variability was detected in two compact loops,
one in each sequence, which brighten at their tops by about 10% in one
hour. In one of the loops, there appears to be a flow up one leg of
the loop with a velocity of 100--200 km s(-1) . The quiescent loop-top
brightenings are reminiscent of transient loop-top brightenings seen in
Yohkoh soft X-ray observations of the quiescent Sun and during flares.
---------------------------------------------------------
Title: Ultraviolet Irradiance at Solar Minimum
Authors: Floyd, L. E.; Crane, P. C.; Herring, L. C.; Cook, J. W.;
Prinz, D. K.; Brueckner, G. E.
1997AAS...191.7409F Altcode: 1997BAAS...29.1325F
The Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) aboard the
Upper Atmosphere Research Satellite has been measuring the sun's UV
spectral irradiance for wavelengths from 115 to 410 nm since October
1991. We describe the behavior of the solar UV spectral irradiance
during the decline of solar cycle 22 with special emphasis on the
recent solar minimum period. Although the time series of the spectral
irradiances have behavior similar to that of the Mg II core-to-wing
ratio, there are differences among them. We describe the behavior
near solar minimum of both the irradiance in selected UV wavelength
intervals, the the Mg II core-to-wing ratio, and the integrated Ly-alpha
line irradiance. Overall, each of these time series follows a similar
pattern: a broad and flat minimum, with some 27-day solar rotation
modulation still evident at nearly all times. The date found for
solar minimum is often used as an input parameter used in predicting
the timing of the following solar cycle maximum. The minimum strongly
depends on both the algorithm and the averaging time period used. For
sunspot number, the generally accepted minimum is defined as the
lowest value of a 12-month running average of monthly averages of daily
values. We analyze various methods for finding the solar minimum in the
UV including that used for sunspot number. For wavelengths longer than
the Al edge at 208 nm, systematic errors due to instrument responsivity
degradation ( ~ +/-1%) become a significant fraction of the long-term
variation during the minimum, making determination of the date of the
minimum increasingly uncertain. We find that the minimum for Mg II
occurs during April 1996 while that for Ly-alpha occurs later, during
October 1996. These results are compared with solar minimum behavior
of other solar indices to better understand the relationship among
the regions of the solar atmosphere where each emission originates.
---------------------------------------------------------
Title: Image Processing of December 23 1997 LASCO CME Observations
Authors: Karovska, M.; Wood, B. E.; Brueckner, G. E.; Cook, J. W.;
Howard, R. A.; Andrews, M. D.
1997SPD....28.0126K Altcode: 1997BAAS...29..884K
The Large Angle Spectrometric Coronagraph (LASCO) onboard SOHO contains
three individual coronagraphs, C1, C2, and C3, that image the solar
corona from 1.1 R_sun to 32 R_sun. Since January 1996, LASCO has
detected a number of CMEs. Starting on December 23 1996 several
spectacular CME events were observed with all LASCO coronagraphs. The
onset was detected with both EIT and LASCO/C1 instruments. The images
of the developing CMEs contain many complex components with different
spatial scales and a wide range of contrast levels. Spatial and
temporal characterization of these structures is extremely important
for understanding the origin and the early evolution of CMEs. To
extract information on the low contrast small-scale structures in the
CMEs we applied image processing techniques to several time sequences
of images. Our study of the movies made from these contrast and/or
resolution enhanced images leads to a better knowledge of the morphology
and temporal evolution of the small scale structures, especially at the
onset of the CME as observed with the C1 and EIT. LASCO is a cooperative
project of an international group of scientists at the Naval Research
Laboratory, Washington, DC, the Max-Planck Institut fur Aeronomie,
Germany, the Laboratoire d'Astronomie Spatiale, France, and the Space
Research Group at the University of Birmingham, Great Britain.
---------------------------------------------------------
Title: Search for Velocity Signatures of Energy Release in Fine
Scale Coronal Features
Authors: Cook, J. W.; Socker, D. G.; Korendyke, C. M.; Howard, R. A.;
Karovska, M.
1997SPD....28.0119C Altcode: 1997BAAS...29..882C
The Large Angle Spectrometric Coronagraph (LASCO) on the SOHO satellite
consists of three individual coronagraphs with nested fields of
view. The innermost C1 coronagraph observes the solar corona from 1.1
to 3.0 R_⊙, and contains a Fabry Perot interferometer which can image
the corona in the 1.8 million K Fe XIV emission line at 5303 Angstroms
with 0.7 Angstroms resolution. We designed an observing program with
reduced spatial coverage and reduced profile coverage at only three
wavelengths (line center and the half power points of the thermal plus
instrumental profile) in order to increase the observing cadence. From
these observations we can construct maps of the observed field in
integrated line intensity, doppler velocity shift, and nonthermal
broadening. We can thus search for signatures of coronal heating such
as transient brightenings, bulk velocity flows, or nonthermal turbulent
line broadening at spatial scales down to 11 arc sec (two CCD pixels),
with temporal resolution of 4 minutes. We have run this program several
times so far, and will report on early results.
---------------------------------------------------------
Title: Ultraviolet Jets and Bright Points in the Solar
Chromosphere. II. Statistical Correlations
Authors: Hoekzema, N. M.; Rutten, R. J.; Cook, J. W.
1997ApJ...474..518H Altcode:
We use HRTS-VI rocket observations of the solar chromosphere to search
for relationships between high-Dopplershift “jets” observed in the C
I lines near λ = 156 nm and internetwork “bright points” observed
in the λ = 160 nm continuum, in sequel to the analysis by Cook et
al. which failed to find a direct connection between these phenomena. We
now use the same data to establish statistical correlations between
C I Dopplershift and 160 nm brightness modulation in internetwork
areas. These mean relations emerge only after extensive spatial
averaging and have small amplitude, but are definitely significant. They
show that both C I Dopplershift and 160 nm brightness participate
in oscillatory behavior with 3 minute periodicity and mesoscale (8
Mm wavelength) as well as small-scale (1.4 Mm wavelength) spatial
patterning. We find spatial and temporal phase relations between
Dopplershift and brightness that confirm that jets and bright points
should not be interpreted as isolated entities. Rather, they are
chromospheric manifestations, with much pattern interference, of the
oscillatory acoustic shock dynamics in the internetwork which also
cause Ca II K<SUB>2V</SUB> grains. Additional small-scale modulation
is present which we attribute to waves with f-mode character.
---------------------------------------------------------
Title: Enhancing the Spatial Resolution of Solar Coronagraph
Observations Using Dynamic Imaging
Authors: Zaccheo, T. S.; Karovska, M.; Cook, J. W.; Howard, R. A.;
Brueckner, G. E.; Korendyke, C. M.; Schwenn, R.
1996ApJ...471.1058Z Altcode:
The Large Angle Spectrometric Coronagraph (LASCO) Cl coronagraph on
board the Solar and Heliospheric Observatory (SOHO) is designed to
image the corona from 1.1 to 3.0 R<SUB>sun</SUB>. The resolution of
C1 is defined by the size of its CCD pixels, which correspond to 5".6,
and not by the diffraction limit of the optical system, which may be as
small as 3". The resolution of Cl can be improved using the technique of
"dynamic imaging" the process of acquiring successive images of the same
scene using sub- pixel displacements of the steerable primary mirror. We
developed a technique we call the fractional pixel restoration (F PR)
algorithm that utilizes these observations to construct an image with
improved resolution. Simulations were used to test this algorithm and
to explore its limitations. We also applied the direct co-addition
and FPR algorithms to laboratory preffight images of a wire mesh
grid. These results show that the resolution of the C1 coronagraph can
be significantly enhanced, even in the presence of noise and modest
differences between successive images. In some cases, the results can
even reach the diffraction limit of the telescope.
---------------------------------------------------------
Title: STEREO: a solar terrestrial event observer mission concept
Authors: Socker, Dennis G.; Antiochos, S. K.; Brueckner, Guenter E.;
Cook, John W.; Dere, Kenneth P.; Howard, Russell A.; Karpen, J. T.;
Klimchuk, J. A.; Korendyke, Clarence M.; Michels, Donald J.; Moses,
J. Daniel; Prinz, Dianne K.; Sheely, N. R.; Wu, Shi T.; Buffington,
Andrew; Jackson, Bernard V.; Labonte, Barry; Lamy, Philippe L.;
Rosenbauer, H.; Schwenn, Rainer; Burlaga, L.; Davila, Joseph M.; Davis,
John M.; Goldstein, Barry; Harris, H.; Liewer, Paulett C.; Neugebauer,
Marcia; Hildner, E.; Pizzo, Victor J.; Moulton, Norman E.; Linker,
J. A.; Mikic, Z.
1996SPIE.2804...50S Altcode:
A STEREO mission concept requiring only a single new spacecraft has been
proposed. The mission would place the new spacecraft in a heliocentric
orbit and well off the Sun- Earth line, where it can simultaneously view
both the solar source of heliospheric disturbances and their propagation
through the heliosphere all the way to the earth. Joint observations,
utilizing the new spacecraft and existing solar spacecraft in earth
orbit or L1 orbit would provide a stereographic data set. The new
and unique aspect of this mission lies in the vantage point of the
new spacecraft, which is far enough from Sun-Earth line to allow an
entirely new way of studying the structure of the solar corona, the
heliosphere and solar-terrestrial interactions. The mission science
objectives have been selected to take maximum advantage of this new
vantage point. They fall into two classes: those possible with the
new spacecraft alone and those possible with joint measurements using
the new and existing spacecraft. The instrument complement on the new
spacecraft supporting the mission science objectives includes a soft
x-ray imager, a coronagraph and a sun-earth imager. Telemetry rate
appears to be the main performance determinant. The spacecraft could
be launched with the new Med-Lite system.
---------------------------------------------------------
Title: Enhancing the spatial resolution of solar coronagraph images
using dynamic imaging
Authors: Karovska, M.; Zaccheo, T. S.; Cook, John W.; Brueckner,
Guenter E.; Howard, Russell A.
1996SPIE.2804..175K Altcode:
The LASCO C1 mirror coronagraph onboard the SOHO satellite (launched
on 2 December 1995) was designed to observe the fine structure of the
solar corona from 1.1 to 3.0 R. Even though the optical resolution
is approximately 3 arc sec, the nominal achieved resolution is set
by the CCD pixel size of 5.6 arc sec. A pixel size of 1.5 arc sec or
less is needed to obtain diffraction limited observations according
to the Nyquist criteria, and therefore the actual coronagraph images
are under sampled by a factor of 4. We have explored improving
the spatial resolution of the LASCO C1 images using the technique
of dynamic imaging. Successive images are obtained with sub-pixel
displacements of the steerable primary mirror. Typically a set of
4 images is obtained with 1/2 pixel displacements in the x and y
axes. Using simulated data we have studied the improvement resulting
both from simple co-addition of the multiple observations, and from
a deconvolution algorithm we call Fractional Pixel Restorations
(FPR). We studied the effects in numerical simulations of noise,
contrast variations, modest differences in the scene observed in the
multiple images, etc. WE have also applied co-addition and the FPR
algorithm to laboratory pre-flight images of a wire mesh target, which
significantly improved the resolution. Using dynamic imaging with 16
images and 1/4 pixel steps, it would in principle be possible to reach
the diffraction limit of the telescope in some circumstances (low noise,
sufficient image contrast, no temporal changes in the observed scene,
a well characterized instrumental point response function). By the
time of this meeting we hope to have high resolution solar images from
the LASCO C1 telescope to show. LASCO is a cooperative project of an
international group of scientists at the Naval Research Laboratory,
Washington, DC, the Max- Planck Institute fur Aeronomie, Germany,
the Laboratoire d'Astronomie Spatiale, France, and the Space Research
Group at the University of Birmingham, Great Britain.
---------------------------------------------------------
Title: Ultraviolet Jets and Bright Points in the Solar
Chromosphere. I. Search for One-to-One Relationships
Authors: Cook, J. W.; Rutten, R. J.; Hoekzema, N. M.
1996ApJ...470..647C Altcode:
Ultraviolet spectrograms and spectroheliograms of the solar chromosphere
are used to test the suggestion of Dere, Bartoe, & Brueckner
and Rutten & Uitenbroek that bright points in quiet Sun cell
interiors observed at = 1600 A, chromospheric jets observed in C I
lines near λ = 1560 Å, and Ca II K<SUB>2v</SUB> bright points are
associated with each other and that they are all manifestations of the
same wave interaction in the nonmagnetic chromosphere. We search for
spatio-temporal connections between 1600 Å bright points and C I blue
jets using data from the High Resolution Telescope and Spectrograph
VI rocket flight, comparing 1600 A spectrohellograms and a cospatial
C I Doppler shift map on a pixel-by-pixel basis. We find no direct
evidence for spatial colocation of bright points and jets, not for
instantaneous correspondence and also not when allowing for phase
delays as long as 3 minutes. Also, the average brightness evolution
and its rms fluctuation are not obviously different between sites of
large C I blueshift and the remaining surface.
---------------------------------------------------------
Title: LASCO Observations of the 03Feb96 Streamer Blow-out
Authors: Andrews, M. D.; Korendyke, C. M.; Koomen, M. J.; Brueckner,
G. E.; Cook, J. W.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Moses,
J. D.; Morrill, J. S.; Moulton, N. E.; Paswaters, S. E.; Socker, D. G.;
St. Cyr, O. C. St.; Wang, D.; Lamy, P. L.; Llebaria, A.; Bout, M. V.;
Schwenn, R.; Podlipnik, B.; Bedford, D. K.; Biesecker, D. A.; Eyles,
C. J.; Plunkett, S.; Simnett, G. M.
1996AAS...188.3716A Altcode: 1996BAAS...28..880A
The C2 and C3 telescopes on the Large Angle Spectrometric Coronograph
(LASCO) have recorded images of a Streamer Blow-out which occured
on 03Feb96. We will present a series of images produces by combining
data from the 2 coronographs. These images show a rapid evolution of
the coronal streamer belt over projected distances of 2 to 20 solar
radii. The streamer belt shows a dramatic brightening, which is seen to
propagate outward. A bubble-like structure is seen to move away from
the Sun and expand. At the end of this event, the equatorial corona
is significantly less bright than prior to the event.
---------------------------------------------------------
Title: LASCO Observations of the Solar Corona to 32 R<SUB>sun</SUB>
Authors: Cook, J. W.; Koomen, M. J.; Korendyke, C. M.; Brueckner,
G. E.; Dere, K. P.; Howard, R. A.; Michels, D. J.; Morrill, J. S.;
Moses, J. D.; Socker, D. G.; Paswaters, S. E.; Wang, D.; Moulton,
N. E.; Cyr, O. C. St.; Andrews, M. D.; Schwenn, R.; Podlipnik, B.;
Lamy, P. L.; Llebaria, A.; Bout, M. V.; Simnett, G. M.; Bedford,
D. K.; Eyles, C. J.; Plunkett, S.; Biesecker, D. A.
1996AAS...188.3717C Altcode: 1996BAAS...28..880C
The Large Angle Spectrometric Coronagraph (LASCO) was launched on
board the SOHO satellite on 2 December 1995. The C3 externally-occulted
coronagraph of LASCO observes the solar corona over a field from 3.7-32
R_ ⊙, using a 1024x1024 CCD detector with a pixel size corresponding
to 56 arc sec. Observations can be made using color filters ranging
from the blue (420-520 nm) to the near-IR (860-1050 nm), and through
polarizing filters. We report on early observations of the solar corona
out to 32 R<SUB>sun</SUB>.
---------------------------------------------------------
Title: Facular Origin of the Sun's 11-year Total Radiation Cycle
Authors: Lean, J.; Cook, J.; Marquette, W.; Johannesson, A.;
Willson, R.
1996AAS...188.7901L Altcode: 1996BAAS...28Q.955L
While the amplitude and temporal structure of the 11-year cycle in the
Sun's total radiation is relatively well established from spacebased
radiometry, the origins of the variations are not. Rotational modulation
on shorter time scales is attributable to the changing presence on the
Sun's Earth-facing disk of dark sunspots and bright faculae, both of
which occur frequently during times of high solar activity but may be
absent for days during solar minimum conditions. However, calculations
of the energy changes in sunspots and active region faculae over the
longer time scale of the 11-year cycle underestimate the observed solar
cycle irradiance modulation by about a factor of two. This apparent lack
of facular brightness has lead to speculation of a missing irradiance
brightness component, and the possibility that a non facular -- perhaps
global -- mechanism may be responsible for the observed total radiation
energy changes. Recent analysis of Ca K filtergrams, recorded with a 1
Angstrom Daystar filter at the BBSO, suggest a methodology with which to
quantitatively assess the contribution of facular brightness to total
solar irradiance variations. Following removal of instrumental effects
and limb variations from the Ca K images, the resultant "flattened"
spectroheliograms provide a surrogate for facular brightness in both
active regions and in the surrounding chromospheric network. Evolution
of the globally integrated signal from enhanced Ca K emission on the
full solar disk is compared with concurrent total solar irradiance
measurements made by the ACRIM II radiometer on the Upper Atmosphere
Research Stellite from 1992 to 1994. This period covers most of the
decline in solar activity from the cycle 22 maximum to the impending
solar minimum, and suggest that facular changes can account for
essentially all the measured variations.
---------------------------------------------------------
Title: Preliminary Photometric Calibration of LASCO C3 Coronagraph
Images using Pre-Flight Laboratory Images of Standard Sources and
In-Flight Images of Standard Stars
Authors: Korendyke, C. M.; Koomen, M. J.; Andrews, M. D.; Brueckner,
G. E.; Cook, J. W.; Dere, K. P.; Howard, R. A.; Michels, D. J.;
Moses, J. D.; Morrill, J. S.; Moulton, N. E.; Paswaters, S. E.;
Socker, D. G.; St. Cyr, O. C.; Wang, D.; Lamy, P. L.; Llebaria, A.;
Bout, M. V.; Schwenn, R.; Podlipnik, B.; Bedford, D. K.; Biesecker,
D. A.; Eyles, C. J.; Plunkett, S.; Simnett, G. M.
1996AAS...188.3621K Altcode: 1996BAAS...28..876K
The C3 coronagraph is a wide field (+/-8.0 degrees), externally
occulted, white light coronagraph. The instrument is one of three
coronagraphs comprising the Large Angle Spectrometric COronagraph
(LASCO) experiment mounted on the Solar Heliospheric Observatory
satellite. The satellite was launched on Dec. 2, 1996; C3 observations
began in early Jan. 1997. The coronagraph optical train includes a set
of five broadband color filters mounted in a wheel. Prior to flight,
an image was obtained through each color filter of a well characterized,
rear-illuminated, opal glass diffusing screen. The C3 in-flight images,
in addition to the coronal structures, also contain several hundred
bright stars. We present a comparison of the photometric calibration
derived from standard stars with the laboratory measurements. The
resulting calibration is then used to examine color variations in the
white light corona over the field of view. The LASCO experiment was
developed by a scientific consortium of members from NRL (USA), MPAe
(Germany), LAS (France) and U. Birmingham (United Kingdom).
---------------------------------------------------------
Title: Comparison of solar flare emission measures from broadband
soft X-ray and ultraviolet spectrograph observations
Authors: Cook, J. W.; Waljeski, K.; Moses, D.; Bruechner, G. E.
1996AdSpR..17d.101C Altcode: 1996AdSpR..17..101C
Joint observations of a solar flare were obtained by the AS&E
Imaging X-ray Telescope and the NRL High Resolution Telescope and
Spectrograph (HRTS). We compare emission measures from soft X-ray and
HRTS data. A small isolated X-ray loop close to the HRTS slit position
has an emission measure n_e^2DeltaL of 3.5x10^29 cm^-5, compared to
an emission measure of 2.7x10^29 cm^-5 obtained from the intensity of
flaring Fe XXI 1354 Angstroms plasma along the HRTS slit.
---------------------------------------------------------
Title: Enhancing the Spatial Resolution of LASCO/C1 Observations
Authors: Zaccheo, T. S.; Karovska, M.; Brueckner, G.; Cook, J. W.;
Howard, R.
1995AAS...18712208Z Altcode: 1995BAAS...27.1454Z
The LASCO C1 coronagraph was designed to examine the fine structure of
the solar corona in the region from 1.1R_sun to 3R_sun. Even though the
diffraction limit of the telescope is ~ 3\arcsec, the nominal resolution
is set by the CCD pixels (5.6”/). A pixel size of 1.5”/ or smaller is
needed in order to obtain diffraction limited observations (according to
the Nyquist criterium). Therefore, the resulting images are undersampled
by a factor of approximately 4. Some of this lost resolution can
be recovered by acquiring successive observations using sub-pixel
displacements of the steerable primary mirror incorporated into the
LASCO/C1 design (“Dynamic Imaging”). The spatial resolution of the
LASCO/C1 coronagraph can be enhanced by combining or co-adding multiple
observations separated by fractions of a pixel. We have identified
several methods for constructing sub-pixel estimates, evaluated the
performance of simple co-addition techniques, and developed an improved
algorithm for obtaining fractional pixel restorations. Simulations
were used to test this algorithm and to explore its limitations. In
this presentation, we describe the algorithm and the results of these
simulations. The results show that the resolution of the C1 coronagraph
can be enhanced, even in the presence of significant noise and modest
differences between successive observations.
---------------------------------------------------------
Title: The O IV and S IV Intercombination Lines in Solar and Stellar
Ultraviolet Spectra
Authors: Cook, J. W.; Keenan, F. P.; Dufton, P. L.; Kingston, A. E.;
Pradhan, A. K.; Zhang, H. L.; Doyle, J. G.; Hayes, M. A.
1995ApJ...444..936C Altcode:
New calculations of O IV electron density diagnostic emission-line
ratios involving the 1399.8, 1401.2, 1404.8, and 14076.4 A transitions
are presented. A comparison of these calculations with observational
data from a quiet solar region, a sunspot, and an active region obtained
with the High Resolution Telescope and Spectrograph (HRTS), two flares
observed with the SO82B spectrograph on board Skylab, and Hubble Space
Telescope (HST) observations by the Goddard High Resolution Spectrograph
(GHRS) of Capella, gives good results using the ratio R<SUB>1</SUB> =
I(1407.4 A)/I(1401.2 A). However, the electron density obtained using
the ratio R<SUB>2</SUB> = I(1407.4 A)/I(1404.8 A) is often an order
of magnitude smaller. The O IV 1404.8 A line is blended with the S
IV 1404.8 A line, and we investigate whether this ratio may still be
used as a density diagnostic if the S IV 1406.1 A line intensity is
used to correct for the presence of S IV 1404.8 A, using previous S
IV calculations by Dufton et al. We still find systematic differences
compared to density determinations from line ratios that do not involve
the O IV 1404.8 A line, which we suggest are due to errors in earlier
theoretical calculations of the S IV atomic data, and also possibly
to previously unconsidered fluorescent pumping of the upper level of
the S IV 1404.8 A transition.
---------------------------------------------------------
Title: The Moon.
Authors: Cook, J.
1995oaa..conf...45C Altcode:
Instruments, the observation, occultations, recording the observation
are discussed.
---------------------------------------------------------
Title: Model For Variability of the Solar Far Ultraviolet Flux Using
Full Disk Magnetograms
Authors: Cook, J. W.; Brueckner, G. E.; Prinz, D. K.; Floyd, L. E.;
Lund, P. A.
1994AAS...18512307C Altcode: 1994BAAS...26R1523C
The variability of the solar full disk flux in the 1175-2100 Angstroms
wavelength range is largely determined from the surface distribution on
the Sun of active regions, whose increase and decrease over the solar
cycle, and passage across the disk, is the main source of long term,
and 27 day, variability. Variations in the distribution of brightness in
quiet areas, perhaps from decay of active regions causing an enhanced
network (“third component"), could also affect variability. While
earlier models of the full disk variability have relied on proxy
activity indicators, such as the Ca II plage area, a more direct
indicator of activity may be full disk photospheric magnetograms. We
have recast our earlier model (1980, J.G.R., 85, 2257) of ultraviolet
variability to base it upon Kitt Peak full disk magnetograms, using
the work of Cook and Ewing (1990, Ap. J., 355, 719) on the observed
relationship of brightness at 1600 Angstroms with magnetic field
strength. We compare our model results with observations of the solar
irradiance from the SUSIM experiment flown on the UARS satellite.
---------------------------------------------------------
Title: The coronal context of transition region explosive events
Authors: Moses, D.; Cook, J. W.
1994SSRv...70...81M Altcode:
Transition region explosive events are observed throughout the quiet
Sun and represent an interesting local heating phenomenon. The coronal
counterparts of these events, if they exist, were not observed in
a sounding rocket campaign dedicated to this objective. The coronal
instrument complement on the SOHO spacecraft provides an opportunity
to extend this search for the coronal counterparts of the transition
region explosive events, as well as to explore the correspondence of
explosive events with large scale coronal structures, such as with
coronal dark lanes.
---------------------------------------------------------
Title: The Determination of Electron Densities in the Solar Atmosphere
from the 1718.56 Angstrom /1486.51 Angstrom Emission-Line Ratio in
N IV
Authors: Keenan, F. P.; Harra, L. K.; Doschek, G. A.; Cook, J. W.
1994ApJ...432..806K Altcode:
The theoretical electron density sensitive emission-line ratio
R = I(1718.56 a)/I(1486.51 A) in N IV is presented for a range of
N<SUB>e</SUB>(approximately equals 10<SUP>10</SUP> - 10<SUP>12</SUP>/cu
cm) applicable to higher density solar plasmas, such as active
regions. A comparison of these calculations with the observed values
of R of several solar features obtained with the Naval Research
Laboratory's S082B spectrograph on board Skylab reveals general
agreement between theory and observation at pointings just above the
limb, where line blends with N IV 1718.56 A should be insignificant,
which provides experimental support for the accuracy of the line
ratio calculations.
---------------------------------------------------------
Title: Solar Fine-Scale Structures in the Corona, Transition Region,
and Lower Atmosphere
Authors: Moses, Dan; Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.;
Dere, K. P.; Webb, D. F.; Davis, J. M.; Harvey, J. W.; Recely, F.;
Martin, S. F.; Zirin, H.
1994ApJ...430..913M Altcode:
The American Science and Engineering Soft X-ray Imaging Payload and the
Naval Research Laboratory High Resolution Telescope and Spectrograph
(HRTS) were launched from White Sands on 1987 December 11 in coordinated
sounding rocket flights. The goal was to investigate the correspondence
of fine-scale structures from different temperature regimes in the
solar atmosphere, and particularly the relationship between X-ray bright
points (XBPs) and transition region explosive events. We present results
of the analysis of co-aligned X-ray images, maps of sites of transition
region explosive events observed in C IV 10<SUP>5</SUP>, HRTS 1600
A spectroheliograms of the T<SUB>min</SUB> region, and ground-based
magnetogram and He I 10830 A images. We examined the relationship
of He I 10830 A dark features and evolving magnetic features which
correspond to XBPs. We note a frequent double ribbon pattern of the
He I dark feature counterparts to XBPs. We discuss an analysis of the
relationship of XBPs to evolving magnetic features by Webb et al.,
which shows that converging magnetic features of opposite polarity are
the most significant magnetic field counterparts to XBPs. The magnetic
bipolar features associated with XBPs appear as prominent network
elements in chromospheric and transition region images. The features
in C IV observations corresponding to XBP sites are in general bright,
larger scale (approximately 10 arcsec) regions of complex velocity
fields of order 40 km/s, which is typical of brighter C IV network
elements. These C IV features do not reach the approximately 100 km/s
velocities seen in the C IV explosive events. Also, there are many
similar C IV bright network features without a corresponding XBP in the
X-ray image. The transition region explosive events do not correspond
directly to XBPs. The explosive events appear to be concentrated in
the quiet Sun at the edges of strong network, or within weaker field
strength network regions. We find a greater number of C IV events than
expected from the results of a previous Spacelab 2 HRTS disk survey. We
attribute this at least partly to better spatial resolution with the
newer HRTS data. The full-disk X-ray image shows a pattern of dark
lanes in quiet Sun areas. The number density of C IV events is twice
as large inside as outside a dark lane (4.6 x 10<SUP>-3</SUP> vs. 2.3
x 10<SUP>-3</SUP> explosive events per arcsec <SUP>2</SUP>). The dark
lane corresponds to an old decaying magnetic neutral line. We suggest
that this provides an increased opportunity for small-scale convergence
and reconnection of opposite polarity magnetic field features, in
analogy with the results of Webb et al. for XBPs but at a reduced
scale of reconnection.
---------------------------------------------------------
Title: Coronal Electron Density Diagnostic from Fe XII
Authors: Cook, J. W.; Keenan, F. P.; Harra, L. K.; Tayal, S. S.
1994ApJ...429..924C Altcode:
We present observations of the forbidden coronal lines Fe XII 1242 A and
1349 A from active regions and from two flares, obtained by the SO82B
slit spectrograph onboard Skylab. The line intensity ratio R = I(1242
A)/I(1349 A) is sensitive to electron density. We have calculated this
ratio using recent atomic data, and obtained coronal electron densities
at T = 1.5 x 10<SUP>6</SUP> K for our observations. We find a range
in N<SUB>e</SUB> of (0.5 to 7.2) x 10<SUP>9</SUP>/cm<SUP>-3</SUP> for
active regions, which is in good agreement with previous results from
other diagnostic ratios in this temperature range, and of approximately
(0.9 to 12) x 10<SUP>9</SUP>/cm<SUP>-3</SUP> (or higher) for flares,
which is generally low compared to previous flare results. The flare
values employ particularly weak 1349 A observations and may not be
reliable. From an observation of an active region just inside the solar
limb, giving the best coverage in our data of both line profiles, we
find a line width (FWHM) for both lines of 0.20 A, which corresponds
to a nonthermal velocity of 18 km/sec.
---------------------------------------------------------
Title: The Allowed Lines of O IV near 1340 Angstrom in High Electron
Density Solar Flares
Authors: Cook, J. W.; Keenan, F. P.; Bhatia, A. K.
1994ApJ...425..861C Altcode:
Intersystem lines of O IV near 1400 A have long been used as electron
density diagnostics for solar plasmas at temperatures of around 160,000
K. In addition, however, several allowed lines of O IV near 1340 A
should become visible in conditions of high plasma electron number
density (greater than 10<SUP>12</SUP>/cu cm), such as during a solar
flare. We present observations of the 1340 A and 1400 A regions of the
solar spectrum for two solar flares, obtained by the SO82B spectrograph
on board Skylab. We examine three candidate lines for allowed O IV
in the flare spectra which occur at the correct wavelengths, but show
that two of these are actually blends dominated by resonantly excited
molecular lines of H2. The third candidate line, at 1343.51 A, we
identify as the O IV allowd line. We present the density and temperature
sensitivity of the ratio of allowed and intersystem O IV lines R =
I(1343.51 A)/I(1407.39 A). The 1343.51 A line is clearly present in
the first solar flare spectrum, and the ratio value implies an electron
density of log N<SUB>e</SUB> = 12.6. The second flare has a much weaker
1343.51 A profile, but again the ratio value implies a high electron
density. Both these electron density values are in good agreement
with estimates for each flare from independent diagnostic ratios. The
simple presence alone of a clearly observed O IV 1343.51 A emission
line implies an electron density greater than 10<SUP>12</SUP>/cu cm.
---------------------------------------------------------
Title: Magnetic Fields; Oscillations; and Heating in the Quiet
Sun Temperature Minimum Region from Ultraviolet Observations at
1600 Angstroms
Authors: Cook, J. W.
1994IAUS..154..287C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Allowed Lines of O IV Near 1340 Angstroms in High Electron
Density Solar Flares
Authors: Cook, J. W.; Keenan, F. P.; Bhatia, A. K.
1993AAS...183.6805C Altcode: 1993BAAS...25.1396C
Intersystem lines of O IV near 1400 Angstroms have long been used as
electron density diagnostics for solar plasmas at temperatures of
around 160,000 K. In addition, however, several allowed lines of O
IV near 1340 Angstroms should become visible in conditions of high
plasma electron number density (N<SUB>e</SUB> > 10(12) cm(-3) ),
such as during a solar flare. We present observations of the 1340
Angstroms and 1400 Angstroms regions of the solar spectrum for two
solar flares, obtained by the S082B spectrograph on board Skylab. We
examine three candidate lines for allowed O IV in the flare spectra
which occur at the correct wavelengths, but show that two of these
are actually blends dominated by resonantly excited molecular lines
of H<SUB>2</SUB>. The third candidate line, at 1343.51 Angstroms,
we identify as the O IV allowed line. We present the density and
temperature sensitivity of the ratio of allowed and intersystem O
IV lines R = I(1343.51 Angstroms)/I(1407.39 Angstroms). The 1343.51
Angstroms line is clearly present in the first solar flare spectrum,
and the ratio value implies an electron density of log N<SUB>e</SUB>
= 12.6. The second flare has a much weaker 1343.51 Angstroms profile,
but again the ratio value implies a high electron density. Both these
electron density values are in good agreement with estimates for each
flare from independent diagnostic ratios. The simple presence alone
of a clearly observed O IV 1343.51 Angstroms emission line implies an
electron density greater than 10(12) cm(-3) .
---------------------------------------------------------
Title: Transition Region Explosive Events in an X-Ray Dark Lane
Region of the Quiet Sun
Authors: Cook, J. W.; Moses, D.; Brueckner, G. E.; Dere, K. P.;
Bartoe, J. -D. F.; Webb, D.; Davis, J. M.; Harvey, J. W.; Recely,
F.; Martin, S. F.; Zirin, H.
1993BAAS...25.1181C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: First Lunar Outpost support study
Authors: Bartz, Christopher; Cook, John; Rusingizandekwe, Jean-Luc
1993STIN...9323054B Altcode:
The First Lunar Outpost (FLO) is the first manned step in the
accomplishment of the Space Exploration Initiative, the Vice
President's directive to NASA on the 20th anniversary of the Apollo
moon landing. FLO's broad objectives are the establishment of a
permanent human presence on the moon, supporting the utilization of
extraterrestrial resources in a long-term, sustained program. The
primary objective is to emplace and validate the first elements of a
man tended outpost on the lunar surface to provide the basis for: (1)
establishing, maintaining and expanding human activities and influence
across the surface; (2) establishing, maintaining and enhancing
human safety and productivity; (3) accommodating space transportation
operations to and from the surface; (4) accommodating production of
scientific information; (5) exploiting in-situ resources. Secondary
objectives are: (1) to conduct local, small scale science (including
life science); (2) In-situ resource utilization (ISRU) demonstrations;
(3) engineering and operations tests; (4) to characterize the local
environment; and (5) to explore locally. The current work is part
of ongoing research at the Sasakawa International Center for Space
Architecture supporting NASA's First Lunar Outpost initiative. Research
at SICSA supporting the First Lunar Outpost initiative has been funded
through the Space Exploration Initiatives office at Johnson Space
Center. The objectives of the current study are to further develop
a module concept from an evaluation of volumetric and programmatic
requirements, and pursue a high fidelity design of this concept, with
the intention of providing a high fidelity design mockup to research
planetary design issues and evaluate future design concepts.
---------------------------------------------------------
Title: Book reviews
Authors: van Driel-Gesztelyi, L.; Meynet, G.; Gaizauskas, V.; Cook,
J. W.; McKenna-Lawlor, S. M. P.; Garmany, C. D.; Jugaku, Jun; Lamers,
Henny J. G. L. M.; Achterberg, A.; De Greve, J. P.; Dommanget, J.;
van der Kruit, P. C.
1993SSRv...64..165V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Book Review: Mechanisms of chromospheric and coronal heating /
Springer, 1991
Authors: Cook, J. W.
1993SSRv...64..168C Altcode: 1993SSRv...64..168U
No abstract at ADS
---------------------------------------------------------
Title: Solar O IV and S IV lines from the High Resolution Telescope
and Spectrograph (HRTS) and the S082B spectrograph on board Skylab.
Authors: Keenan, F. P.; Cook, J. W.; Doyle, J. G.; Dufton, P. L.;
Hayes, M. A.; Kingston, A. E.
1993uxrs.conf..345K Altcode: 1993uxsa.conf..345K
A comparison of theoretical O IV electron density diagnostics with
observational data from a quiet solar region, a sunspot and an active
region obtained with the High Resolution Telescope and Spectrograph
(HRTS), and a flare observed with the S082B instrument on board Skylab,
reveals that the O IV 1404.8 Å line is not only blended with the S IV
1404.8 Å transition, but also with an unknown feature that contributes
a significant amount to the blend. It is therefore suggested that
line ratios which include the O IV 1404.8 Å transition should not be
employed as density diagnostics.
---------------------------------------------------------
Title: The Sun as a Star: High Spectral Resolution Solar Data Degraded
to Low-Dispersion IUE Resolution
Authors: Doyle, J. G.; Cook, J. W.
1992ApJ...391..393D Altcode:
High spectral resolution (about 0.06 A) solar data for an active region
and a large two-ribbon flare degraded to the typical resolution
of low-dispersion (about 5 A) spectra of the IUE satellite are
presented. This clearly shows the amount of detail yet to be acquired
in stellar spectra and indicates the main spectral regions where line
blending is a problem.
---------------------------------------------------------
Title: Solar SI II Line Ratios from the High-Resolution Telescope
and Spectrograph
Authors: Keenan, F. P.; Cook, J. W.; Dufton, P. L.; Kingston, A. E.
1992ApJ...387..726K Altcode:
Theoretical emission-line ratios involving multiplets near 1262,
1306, and 1530 A are derived on the basis of new calculations of
electron-impact excitation rates for allowed transition in Si II. A
comparison of these line ratios with observational data from a quiet
solar region, a sunspot, and an active region, obtained with the HIRTS
on board a sounding rocket flight reveals that the 1530-A multiplet
is optically thick, which is consistent with a calculation of the
optical depth of these lines through a model atmosphere. The 1262-
and 1306-A multiplets appear to be effectively optically thin. The
average discrepancy between the theoretical and observed ratios is
about 40 percent, which may not be significant, since the estimated
uncertainties in both the calculated and experimental data are
approximately 30 percent.
---------------------------------------------------------
Title: High Spectral Resolution Solar Data Degraded to Low Dispersion
lUE Resolution
Authors: Doyle, J. G.; Cook, J. W.
1992ASPC...26...49D Altcode: 1992csss....7...49D
No abstract at ADS
---------------------------------------------------------
Title: Magnetic fields, oscillations, and heating in the quiet sun
temperature minimum region
Authors: Cook, John W.
1992AIPC..267...55C Altcode: 1992ecsa.work...55C
The High Resolution Telescope and Spectrograph (HRTS) instrument
contains a broadband spectroheliograph which has been tuned on sounding
rocket flights to cover a passband centered on 1600 A˚, where the
predominant flux contributor is continuum emission from the temperature
minimum region (approximately 70% of the integrated intensity in
quiet regions). I discuss the HRTS observations of the temperature
minimum region in quiet areas and their relation with magnetic field,
5 minute oscillations, and heating. The brightness temperature of
solar fine structure elements composing the supergranular network
is found to be linearly proportional to the local absolute value of
magnetic field strength. In cell centers, there is evidence for a 250
s period oscillation occurring in 10 arc sec scale patches, which,
however, is energetically unimportant to the local heating budget. I
discuss an interpretation in which a basal heating and 5 minute type
oscillations occur globally, while the network bright points occur in
magnetic regions, heated perhaps from partial dissipation of Alfven
waves (whose energy flux is linearly proportional to B) in individual
elemental 1500 G (at the photosphere) flux tubes which expand to form
the temperature minimum fine structure bright points.
---------------------------------------------------------
Title: Magnetic fields, oscillations, and heating in the quiet sun
temperature minimum region
Authors: Cook, J. W.
1992ecsa..267...55C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The chromospheric and transition region manifestations of an
Ellerman bomb.
Authors: Cook, J. W.; Brueckner, G. E.; Dere, K. P.; Martin, S. F.;
Gayley, K. G.
1992BAAS...24.1074C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Sun as a Star: High Spectral Resolution Solar Data Degraded
to Low Dispersion IUE Resolution
Authors: Cook, J. W.; Doyle, J. G.
1991BAAS...23.1384C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comparision of Solar Flare Emission Measures from Broadband
Soft X-Ray and Ultraviolet Spectrograph Observations
Authors: Waljeski, K.; Cook, J. W.; Moses, D.; Brueckner, G. E.
1991BAAS...23.1468W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Evidence for a 250 Second Brightness Oscillation at 1600
Angstrom in the Solar Temperature Minimum Region
Authors: Cook, J. W.; Ewing, J. A.
1991ApJ...371..804C Altcode:
A 330 s sequence of solar images at 1600 A, where the solar flux arises
predominantly from the temperature minimum continuum, obtained from a
sounding rocket flight, has been studied. The statistical distributions
of the periods and amplitudes which result from fitting a sine wave to
each individual 5 arcsec square box within a 350 x 350 arcsec quiet-sun
field were obtained. Evidence is found for 250 s oscillations in the
quiet-sun brightness temperature in about 10 arcsec coherent patches,
with an average amplitude of 50 K. The amplitude corresponds to
an energy flux of 180,000 ergs/sq cm/s for undamped, adiabatic,
propagating sound waves, which is small compared to the heating
requirement in the temperature minimum region.
---------------------------------------------------------
Title: Cell Center Bright Points as Dynamic Phenomena: Search for
a Chromospheric Velocity Signature
Authors: Cook, J. W.
1991BAAS...23.1028C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Prime Energy Release of a Solar Flare
Authors: Brueckner, G. E.; Moses, D.; Cook, J. W.; Dere, K. P.;
Korendyke, C. M.; Socker, D. G.; Bartoe, J. -D. F.
1991BAAS...23.1026B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Flaring Active Region Structures in the Corona, Transition
Region, and Lower Atmosphere Observed in the SAROC
Authors: Moses, D.; Brueckner, G. E.; Cook, J. W.; Dere, K. P.;
Korendyke, C. M.; Socker, D. G.; Bartoe, J. -D. F.
1991BAAS...23.1026M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Fine structure of the solar transition region: observations
and interpretation.
Authors: Cook, J. W.; Brueckner, G. E.
1991sia..book..996C Altcode:
The authors review recent observations of the solar transition region
and the temperature minimum obtained with high spatial resolution,
primarily ultraviolet spectra and spectroheliograms from sounding
rocket and Spacelab 2 flights of the High Resolution Telescope and
Spectrograph. Information on intensities, velocities, emission
measures and electron densities can be determined. The authors
discuss observational results and the implications of observed
fine structure for our ideas of the structure and physics of the
solar atmosphere. Inclusion of fine structure in our ideas about the
transition region affects the plausibility of one-dimensional average
models of the atmosphere, the determination of temperature gradients,
possible mechanisms for nonradiative heating, and the comparison
of transition region structures with corresponding high-resolution
observations from the photosphere and corona.
---------------------------------------------------------
Title: High Spatial Resolution Observations of the Solar Transition
Region: Spicules and Microflares (With 6 Figures)
Authors: Cook, J. W.
1991mcch.conf...83C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Relationship of Magnetic Field Strength and Brightness of
Fine-Structure Elements in the Solar Temperature Minimum Region
Authors: Cook, J. W.; Ewing, J. A.
1990ApJ...355..719C Altcode:
A quantitative relationship was determined between magnetic field
strength (or magnetic flux) from photospheric magnetograph observations
and the brightness temperature of solar fine-structure elements observed
at 1600 A, where the predominant flux source is continuum emission
from the solar temperature minimum region. A Kitt Peak magnetogram
and spectroheliograph observations at 1600 A taken during a sounding
rocket flight of the High Resolution Telescope and Spectrograph
from December 11, 1987 were used. The statistical distributions of
brightness temperature in the quiet sun at 1600 A, and absolute value
of magnetic field strength in the same area were determined from these
observations. Using a technique which obtains the best-fit relationship
of a given functional form between these two histogram distributions,
a quantitative relationship was determined between absolute value
of magnetic field strength B and brightness temperature which is
essentially linear from 10 to 150 G. An interpretation is suggested,
in which a basal heating occurs generally, while brighter elements are
produced in magnetic regions with temperature enhancements proportional
to B.
---------------------------------------------------------
Title: Coronal Dark Lanes and the Location of Transition Region
Explosive Events
Authors: Moses, D.; Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.;
Dere, K. P.; Davis, J. M.
1990BAAS...22..899M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Return of the Hard Solar Flares' 154 Day Periodicity in Solar
Cycle 22 and Evidence for a Phase Relationship of This Periodicity
between Cycles 21 and 22
Authors: Brueckner, G. E.; Cook, J. W.
1990ApJ...350L..21B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Heating by 300 s Waves in Nonmagnetic Areas of the Quiet Sun
Temperature Minimum
Authors: Cook, J. W.; Ewing, J. A.
1989BAAS...21.1180C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Correspondence between solar fine-scale structures in the
corona, transition region, and lower atmosphere from collaborative
observations
Authors: Moses, J. Daniel; Cook, J. W.; Bartoe, J. -D. F.; Brueckner,
G. E.; Dere, K. P.; Webb, D. F.; Davis, John M.; Recely, F.; Martin,
S. F.; Zirin, H.
1989sxsr.reptR....M Altcode:
The Soft X-Ray Imaging Payload and the High Resolution Telescope and
Spectrograph (HRTS) instrument were launched from White Sands on 11
December 1987 in coordinated sounding rocket flights to investigate the
correspondence of coronal and transition region structures, especially
the relationship between X-ray bright points (XBPs) and transition
region small spatial scale energetic events. The coaligned data from
X-ray images are presented along with maps of sites of transition
region energetic events observed in C IV (100,000 K), HRTS 1600 A
spectroheliograms of the T<SUB>min</SUB> region and ground based
magnetogram and He I 10830 A images.
---------------------------------------------------------
Title: Solar SI III Line Ratios from the High-Resolution Telescope
and Spectrograph on Board Spacelab 2: The Effects of Non-Maxwellian
Electron Distribution Function
Authors: Keenan, F. P.; Cook, J. W.; Dufton, P. L.; Kingston, A. E.
1989ApJ...340.1135K Altcode:
Electron impact excitation rates for transitions in Si III,
incorporating the effects of non-Maxwellian electron velocity
distribution functions (EVDFs), are presented for a range of
electron temperatures appropriate to the solar transition region. A
comparison of theoretical line ratios with observational data for a
quiet solar region, a sunspot, and an active region obtained with the
high-resolution telescope and spectrograph (HRTS) on board Spacelab
2 indicates that non-Maxwellian EVDFs may exist in the transition
region. Non-Maxwellian effects appear to be larger for the sunspot
than for the quiet sun, implying that the temperature gradient may be
greater in the former.
---------------------------------------------------------
Title: Effect of Coronal Elemental Abundances on the Radiative
Loss Function
Authors: Cook, J. W.; Cheng, C. -C.; Jacobs, V. L.; Antiochos, S. K.
1989ApJ...338.1176C Altcode:
The solar photosphere and corona abundances tabulated by Meyer
(1985) and the chromospheric abundances given by Murphy (1985) are
used here to recalculate radiative loss functions for equilibrium,
low-density, optically thin plasmas. Results from a representative
standard photospheric abundance set and from coronal and chromospheric
abundance sets showing depletions of up to a factor of four in
certain elemental abundances are compared. A significant difference
is found for both the coronal and chromospheric abundance sets, with
the peak of the radiative loss curve shifted closer to 10 to the 6th
K than to the standard 2 x 10 to the 5th K found from photospheric
abundances. Consequences of these new calculations, in particular for
the cool loop model of Antiochos and Noci (1986), are discussed.
---------------------------------------------------------
Title: The HRTS Guest Investigator Program
Authors: Lund, P.; Ewing, J.; Cook, J.; Dere, K.; Brueckner, G.
1989BAAS...21..841L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comparison of HRTS Sounding Rocket Observations at 1600 Å
and Hα with Groundbased Magnetograms and He I 10830 Å Images
Authors: Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere, K. P.
1989BAAS...21..840C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ultraviolet Observations of Macrospicules at the Solar Limb
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook,
J. W.; Socker, D. G.; Ewing, J. W.
1989SoPh..119...55D Altcode:
During the Spacelab 2 mission, the NRL High Resolution Telescope and
Spectrograph (HRTS) obtained a time-series of broad-band ultraviolet
images of macrospicules at the solar limb inside a polar coronal
hole with a temporal resolution of 20 and 60 s. The properties of the
macrospicules observed in the Spacelab data are measured and compared
with the properties reported for EUV macrospicules observed during
Skylab (Bohlin et al., 1975; Withbroe et al., 1976). There is a general
agreement between the data sets but several differences. Because of
the higher temporal resolution of the Spacelab data, it is possible
to see macrospicules with shorter lifetimes than seen during Skylab,
as well as variations on faster timescales. The largest (30-60') and
fastest (150 km s <SUP>-1</SUP>) macrospicules seen during Skylab were
not found in the Spacelab observations. The Spacelab data support the
conclusion that many macrospicules decay by simply fading away.
---------------------------------------------------------
Title: Plasma Motions in an Emerging Flux Region
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Dere,
K. P.; Socker, D.; Kurokawa, H.; McCabe, M.
1988ApJ...335..986B Altcode:
Ultraviolet spectra of C IV show large nonthermal broadening in an
area of emerging flux. These nonthermal motions are observed at a very
early stage of reconnecting field lines. The spectra can be traced
to small, rapidly changing surge or filament-like features which
are seen in the center, blue, and red wing of H-alpha. They seem to
have the characteristics of macrospicules or explosive events. They
are precursors of the reconnection process. Plasma turbulence and/or
plasma waves in the reconnecting plasma may cause the broad C IV line
profiles. The activity in the transition zone precedes the formation
of a bright chromospheric loop system.
---------------------------------------------------------
Title: Gas Flows in the Transition Region above Sunspots
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Engvold, O.;
Maltby, P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Dere,
K. P.; Socker, D. G.
1988ApJ...334.1066K Altcode:
Strong downflows and moderate upflows in the transition region over
a sunspot have been observed with the HRTS on Spacelab 2 in 1985. The
flows are persistent in the sense that they are seen in the same spot
for 5 days. The downflows are prominent in regions of limited extent
(4arcsec - 6arcsec), and flow velocities are in the range 40 - 80 km
s<SUP>-1</SUP> and are thus supersonic. Upward flows have smaller
velocities, 5 - 20 km s<SUP>-1</SUP>, but may extend over a larger
area. In the downflowing regions there is always an appreciable amount
of gas at rest in the line of sight. Flow speeds derived from the
profiles of different lines formed in the transition region between
30,000 and 230,000K are very similar implying constant downflow in
this temperature range.
---------------------------------------------------------
Title: Magnetic Field Strength and Brightness of Fine Structure
Elements in the Solar T<SUB>min</SUB> Region
Authors: Cook, J. W.; Ewing, J. A.
1988BAAS...20R.989C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Determination of Film Characteristic Curves from Density
Histograms
Authors: Cook, J. W.; Ewing, J. A.; Sutton, C. S.
1988PASP..100..402C Altcode:
A method for producing the film characteristic curve from exposures
of the same image field with varying exposure times is developed,
using the film density histogram distributions of the individual
exposures. This method is appropriate for cases where a standard step
wedge or other sensitometric calibration is not available, and where
film reciprocity can be assumed for the exposure times used. The
method is very general and incorporates as much of the film density
information as the user desires.
---------------------------------------------------------
Title: The Correspondence Between Fine-Scale Structures in the Solar
Corona and Transition Region
Authors: Moses, J. D.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook,
J. W.; Dere, K. P.; Davis, J. M.; Webb, D.
1988BAAS...20..722M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Correlation of Transition Region C IV High-Velocity Events
With Magnetogram and He I 10830 Å Data
Authors: Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere,
K. P.; Recely, F.; Martin, S.; Zirin, H.
1988BAAS...20..722C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Results from the High Resolution Telescope and Spectrograph
(HRTS) Experiment on Board Spacelab 2
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Dere,
K. P.; Socker, D. G.
1988ApL&C..27..151B Altcode:
Several papers including reviews have been published during different
stages of the data analysis after the SL-2 flight. In order to avoid
repetition, this article lists all publications and briefly mentions
some of the highlights.
---------------------------------------------------------
Title: Ultraviolet Observations of Solar Fine Structure
Authors: Dere, Kenneth P.; Bartoe, John-David F.; Brueckner, Guenter
E.; Cook, John W.; Socker, Dennis G.
1987Sci...238.1267D Altcode:
The High Resolution Telescope and Spectrograph was flown on the
Spacelab-2 shuttle mission to perform extended observations of the
solar chromosphere and transition zone at high spatial and temporal
resolution. Ultraviolet spectroheliograms show the temporal development
of macrospicules at the solar limb. The C IV transition zone emission
is produced in discrete emission elements that must be composed of
exceedingly fine (less than 70 kilometers) subresolution structures.
---------------------------------------------------------
Title: Microscopic potentials for polarized triton elastic scattering
Authors: Cook, J.
1987NuPhA.473..458C Altcode:
The double folding model is used to calculate real central and
spin-orbit potentials for triton elastic scattering. These potentials
are used to fit cross sections and analysing powers at 17 MeV for
targets ranging from <SUP>26</SUP>Mg to <SUP>208</SUP>Pb. For most
targets the data are described as well as with phenomenological
potentials. The real central potential can be used without any
substantial renormalisation, but the spin-orbit potential needs to be
increased in strength by a factor between 2 and 6. Comparisons are made
with phenomenological studies of triton and <SUP>3</SUP>He elastic
scattering and with similar microscopic studies of <SUP>3</SUP>He
scattering.
---------------------------------------------------------
Title: Discrete Subresolution Structures in the Solar Transition Zone
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook,
J. W.; Socker, D. G.
1987SoPh..114..223D Altcode:
During operations on the Spacelab-2 Shuttle mission, the NRL High
Resolution Telescope and Spectrograph (HRTS) recorded spectra of a
variety of solar features in the 1200-1700 Å wavelength region which
contains spectral lines and continua well suited for investigating
the temperature minimum, the chromosphere and transition zone. These
data show that, at the highest spatial resolution, the transition zone
spectra are broken up from a continuous intensity distribution along
the slit into discrete emission elements. The average dimensions
of these discrete transition zone structures is 2400 km along the
slit, but an analysis of their emission measures and densities shows
that the dimensions of the actual emitting volume is conciderably
less. If these structures are modelled as an ensemble of subresolution
filaments, we find that these filaments have typical radii of from
3 to 30 km and that the cross-sectional fill factor is in the range
from 10<SUP>−5</SUP> to 10<SUP>−2</SUP>. The transport of mass
and energy through these transition zone structures is reduced by
this same factor of 10<SUP>−5</SUP> to 10<SUP>−2</SUP> which has
significant consequences for our understanding of the dynamics of the
solar atmosphere. Because the HRTS transition zone line profiles are
not broadened by resolved large-spatial-scale solar velocity fields,
the line widths of the CIV lines have been analyzed. The average line
width is 0.195 Å (FWHM) and requires an average nonthermal velocity
of 16 km s<SUP>−1</SUP> (most-probable) or 19 km s<SUP>−1</SUP>
(root-mean-square) which is lower than previously observed values.
---------------------------------------------------------
Title: SKYLAB XUV Observations of Densities, Thermal Structure,
and Mass Motions in a Compact Flare
Authors: Widing, Kenneth G.; Cook, J. W.
1987ApJ...320..913W Altcode:
The energetic limb flare of 1973 December 17 was one of the best
Skylab examples of a class characterized by small volume, high energy
density, and short lifetime. In the present paper the authors have
studied the extensive series of slit spectra of this flare obtained
with the NRL slit spectrograph on Skylab operating in the 1000 -
1945 Å range. An overview of the flare development and exposure
chronology is given. Examples of the flare morphology observed in He
II, Ne IV, and Mg VII are contrasted with the morphology observed in
Fe XVII. Slit profiles of Fe XXI 1354 Å, O V 1371 Å, and Si IV 1403
Å are presented. The electron density is derived at selected phases
from diagnostic line ratios of O IV, O V, S IV, and S V observed in
the slit spectra. In the decay phase these densities are combined
with the densities derived from high-temperature lines to obtain
the density distribution in the flare between 10<SUP>5</SUP>K and
6×10<SUP>6</SUP>K. The arch structure within the 5arcsec×5arcsec
kernel is resolved and an improved picture of the density spatial
structure of the flare kernel is derived.
---------------------------------------------------------
Title: Effect on the Radiative Loss Function of Coronal Elemental
Abundances
Authors: Cook, J. W.; Cheng, C. -C.; Antiochos, S. K.
1987BAAS...19..931C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Reconnection in the Solar Transition Zone
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Dare,
K. P.; Socker, D. G.
1987BAAS...19..942B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: SKYLAB XUV Observations of Densities and Thermal Structure
in a Compact Flare
Authors: Widing, K. G.; Cook, J. W.
1987BAAS...19Q.753W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Transition Zone Flow Patterns in Sunspots
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook,
J. W.; Socker, D. G.
1987BAAS...19..639D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Statistical Properties of Small High-Velocity Events in the
Solar Transition Region
Authors: Cook, J. W.; Lund, P. A.; Bartoe, J. -D. F.; Brueckner,
G. E.; Dere, K. P.; Socker, D. G.
1987LNP...291..150C Altcode: 1987csss....5..150C
We discuss the energy contribution of small high-velocity events
observed in the solar transition region to atmospheric heating. These
events do not directly provide enough energy to heat the atmosphere,
but are instead after-products of turbulent energy dissipation at the
sites of the actual primary nonthermal heating process.
---------------------------------------------------------
Title: Observation of the Density Sensitive Line Mg V 1324 Å in a
Solar Sunspot
Authors: Cook, J. W.; Socker, D. G.; Bartoe, J. -D. F.; Brueckner,
G. E.; Dere, K. P.
1986BAAS...18R.991C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Discrete Components of Solar Transition Zone Emission
Authors: Dere, K. P.; Brueckner, G. E.; Bartoe, J. -D. F.; Cook,
J. W.; Socker, D. G.
1986BAAS...18Q.662D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Statistical Properties of Small High-Velocity Transition
Region Events on the Sun Observed by HRTS on Spacelab 2
Authors: Cook, J. W.; Lund, P. A.; Brueckner, G. E.; Bartoe, J. -D. F.;
Dere, K. P.; Socker, D. G.
1986BAAS...18..662C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Results from the High Resolution Telescope and Spectrograph
(HRTS) Experiment
Authors: Brueckner, G. E.; Cook, J. W.; Dere, K. P.
1986BAAS...18..675B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: HRTS Spacelab 2 Observations of the Temporal Development of
the C IV Transition Zone
Authors: Dere, K. P.; Bartoe, J. -D. F.; Brueckner, G. E.; Cook,
J. W.; Lund, P.; Socker, D. G.
1986BAAS...18..633D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: HRTS results from spacelab 2
Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Dere,
K. P.; Socker, D. G.
1986AdSpR...6h.263B Altcode: 1986AdSpR...6..263B
The HRTS instrument flew on the Spacelab 2 mission from 29 July -
6 August 1985. HRTS consisted of a 30 cm Gregorian telescope, a slit
spectrograph covering the 1190-1680 Å region with 0.05 Å spectral
resolution, a broadband (90 Å FWHM) spectroheliograph tuned to 1550
Å, and an H-alpha filter system. The spectrograph slit was 920 arc
sec, approximately 1 R<SUB>0</SUB>, in length. Sub arc second spatial
resolution along the slit is possible, but because of jitter in the
Spacelab Instrument Pointing System (IPS) good exposures actually
achieved 1-2 arc sec resolution. We describe the scientific results
from HRTS.
---------------------------------------------------------
Title: Results from the NRL instruments on Spacelab 2
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Dere,
K. P.; Morrison, M. D.
1986aiaa.meetZ....B Altcode:
The instrumental features of the high resolution Telescope and
spectrograph (HRTS) and the solar UV spectral irradiance monitor
(SUSIM) used for solar observations on the Spacelab 1 mission are
described. The HRTS has three focal plane instruments receiving light
from a 30 cm aperture furnishing at 15 X 15 arcmin FOV which can
be modified for slit photography and raster scans. The focal plane
instruments are a spectrograph, spectroheliograph and a television
camera and photographic film fronted by a mica Fabry-Perot filter. About
13 hr of solar observations were made with the HRTS during the 8
day mission. Sample spectral and photographic data are provided and
discussed. SUSIM is an UV spectrometer with redundant optical paths for
in-flight calibration with a D2 lamp. It is sensitive in the 1200-4000
A range. Several wavelength ranges are evaluated. Particular attention
is given to multitemporal Ly-alpha recordings.
---------------------------------------------------------
Title: HRTS Spacelab 2 Observations of Spicular Emission at the
Solar Limb
Authors: Cook, J. W.; Bartoe, J. -D. F.; Brueckner, G. E.; Dere,
K. P.; Socker, D. G.
1985BAAS...17..834C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: HRTS Results from SPACELAB2
Authors: Cook, J. W.
1985tphr.conf..308C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Relative Contribution of Lines and Continus to Solar Far
Ultraviolet Variability
Authors: Cook, J. W.; Vanhoosier, M. E.
1985BAAS...17..630C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: HRTS results from Spacelab 2.
Authors: Cook, J. W.
1985MPARp.212..308C Altcode:
Three years from now it will be possible to look back on the Spacelab
2 flight and clearly pick out the most interesting new results
obtained. Today the investigators are just beginning to examine the
data, and can see a number of observations which seem exciting. A few
representative examples are given.
---------------------------------------------------------
Title: HRTS observations of spicular emission at transition region
temperatures above the solar limb
Authors: Cook, J. W.; Brueckner, G. E.; Bartoe, J. -D. F.; Socker,
D. G.
1984AdSpR...4h..59C Altcode: 1984AdSpR...4...59C
Slit spectra and spectroheliograph observations were obtained
during the fourth rocket flight of the High Resolution Telescope
and Spectrograph (HRTS) on 7 March 1983. A curved slit 900 arc sec
in length was placed at the solar limb on the western edge of the
south polar coronal hole, giving both coronal hole and quiet region
coverage. In addition, spectroheliograph images tuned to cover a
passband around 1550 Å (primarily C IV at 10<SUP>5</SUP> K) were
taken over an 8 × 15 arc min field. Simultaneous Hα images were
obtained at Sac Peak Observatory. The C IV spectroheliograms show
general spiked emission above the limb, and also several small loo-
or prominence-like events. Slit spectra along the tops of several of
these structures show tilted features which could be interpreted as
rotational velocities of approximately 50 km s<SUP>-1</SUP>.
---------------------------------------------------------
Title: HRTS Evidence for Rotation of Transition Region Temperature
Spicules
Authors: Cook, J. W.; Brueckner, G. E.; Bartoe, J. -D. F.; Socker,
D. G.
1984uxsa.coll...32C Altcode: 1984uxsa.conf...32C; 1984IAUCo..86...32C
No abstract at ADS
---------------------------------------------------------
Title: Relative Contribution of Lines and Continua to Solar Far
Ultraviolet Variability
Authors: Cook, J. W.; Vanhoosier, M. E.
1983BAAS...15..951C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Mass and energy balance in the 1973 August 9 flare
Authors: Dere, K. P.; Cook, J. W.
1983A&A...124..181D Altcode:
The mass and energy balance of the thermal plasma during the decay
phase of the solar flare of August 9, 1973, are studied. The analysis
is based on observationally determined values for the differential
emission measure, density, turbulent and bulk velocities, and
physical dimensions. The total particle content and total thermal
energy content of the flare plasmas with temperatures above 100,000 K
and their variation with time are calculated. The particle loss and
the energy losses through radiation, conduction, and convection are
evaluated. The decrease in total particle content can be accounted
for by the convective losses through the loop footprints at 100,000
K. Radiation is the dominant energy loss mechanism although convective
losses at 100,000 K can be important. Conductive losses at 100,000
K into cooler chromospheric material appear to be negligible. The
decrease in the total energy content during the decay phase is equal
to the sum of the energy losses over the period of observation. No
requirement is found for continued heating during the decay phase.
---------------------------------------------------------
Title: High resolution telescope and spectrograph observations of
solar fine structure in the 1600 A region
Authors: Cook, J. W.; Brueckner, G. E.; Bartoe, J. -D. F.
1983ApJ...270L..89C Altcode:
High spatial resolution spectroheliograms of the 1600 A region obtained
during the HRTS rocket flight of 1978 February 13 are presented. The
morphology, fine structure, and temporal behavior of emission bright
points (BPs) in active and quiet regions are illustrated. In quiet
regions, network elements persist as morphological units, although
individual BPs may vary in intensity while usually lasting the flight
duration. In cell centers, the BPs are highly variable on a 1 minute
time scale. BPs in plages remain more constant in brightness over
the observing sequence. BPs cover less than 4 percent of the quiet
surface. The lifetime and degree of packing of BPs vary with the local
strength of the magnetic field.
---------------------------------------------------------
Title: HRTS Observations of a Coronal Hole and Quiet Region at the
Solar Limb
Authors: Bartoe, J. -D. F.; Brueckner, G. E.; Cook, J. W.; Socker,
D. G.
1983BAAS...15..703B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Temporal Behavior of Quiet Sun Emission in the T<SUB>min</SUB>
Region
Authors: Cook, J. W.; Brueckner, G. E.; Bartoe, J. -D. F.
1982BAAS...14..938C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar plages and the interpretation of stellar Ca II H and
K line variations in late type dwarfs.
Authors: Cook, J. W.
1982SAOSR.392A.181C Altcode: 1982csss....2..181C
Approximately a dozen late type dwarf stars have been observed by
Wilson (1978) to undergo cyclic variability in Ca II H and K line
emission which seems analogous to the solar activity cycle. What might
be learned about these stars from solar analogies? The Ca II K index
is estimated variation of the Sun viewed as a star, and compared with
the observed range of Wilson's stellar observations. Results indicate
trends of increasing relative variation H-K(max)/H-K(min) with later
spectral type, due to decreasing dilutional contribution of residual
photospheric flux to a 1 A band at line center, and of increasing
relative variation with decreasing relative time of rise to maximum
tau rise/tau reminiscent of the observed solar correlation of a quick
rise to sunspot maximum with a strong cycle.
---------------------------------------------------------
Title: Quiet Sun observations of the Al i autoionization lines λ1932
and λ1936
Authors: Cook, J. W.; Kjeldseth Moe, O.
1982SoPh...76..109C Altcode:
We present quiet Sun observations obtained during a rocket flight of
the Al I autoionization lines λ1932 and λ1936 at solar pointings
ranging from μ = 0.73 out to the visible limb. Absolute intensities
are estimated to be accurate to approximately ±20%. These lines
progressively weaken with decreasing μ but never go into emission
before finally disappearing with the continuum just beyond the
visible solar limb. The observations are compared with LTE line
profiles computed through the quiet Sun atmosphere of Vernazza et
al. (1976). We discuss several areas of disagreement between the
synthetic and observed profiles.
---------------------------------------------------------
Title: A high precision Solar Ultraviolet Spectral Irradiance Monitor
for the wavelength region 120 400 nm
Authors: Vanhoosier, M. E.; Bartoe, J. -D. F.; Brueckner, G. E.;
Prinz, D. K.; Cook, J. W.
1981SoPh...74..521V Altcode:
There exists a growing need to improve the accuracy of measurement
of the absolute solar flux within the wavelength range 120-400
nm. Although full-disk solar fluxes and variations thereof in the
120-400 nm region are required to model the solar atmosphere, current
increased interest in the measurements arises from their importance in
modeling the terrestrial atmosphere. We describe the Solar Ultraviolet
Spectral Irradiance Monitor (SUSIM) experiment under development at the
Naval Research Laboratory (NRL) for flight aboard the Space Shuttle and
the Upper Atmospheric Research Satellite (UARS). SUSIM will monitor
the solar flux in the 120-400 nm region with high precision, using
an in-flight calibration system to reduce absolute error to < 10%,
and error relative to the 400 nm continuum to < 1%.
---------------------------------------------------------
Title: Folding model analysis of triton and <SUP>3</SUP>He elastic
scattering
Authors: Cook, J.; Griffiths, R. J.
1981NuPhA.366...27C Altcode:
A double folding model using the M3Y interaction has been successfully
applied to a wide range of triton and <SUP>3</SUP>He data. A
projectile energy and mass dependence in the exchange potential
proportional to E/A<SUB>p</SUB> is shown to be adequate between 11 and
27 MeV/nucleon. Normalization factors for triton and <SUP>3</SUP>He
real potentials of ~ 0.6 and ~ 0.8, respectively, are in accordance
with those of other light projectiles subject to break-up.
---------------------------------------------------------
Title: Latitudinal anisotropy of the solar far ultraviolet flux -
Effect on the Lyman alpha sky background
Authors: Cook, J. W.; Meier, R. R.; Brueckner, G. E.; van Hoosier,
M. E.
1981A&A....97..394C Altcode:
An estimate is given for the anisotropy of the solar full disk flux in
the far ultraviolet, as it would be observed for lines of sight within
and above the ecliptic plane through the predominant influence of plages
at low heliocentric latitudes. The flux anisotropy for Lyman alpha,
at a level of solar activity with a sunspot number of roughly 160,
is approximately 0.88 for the integrated flux over the Lyman alpha
profile and 0.83 for the flux at line center. The effect of this Lyman
alpha flux anisotropy on the Lyman alpha sky background intensity,
resonantly backscattered from the local interstellar medium that
is streaming through the solar system, is examined. It is concluded
that the solar Lyman alpha anisotropy should be included in models
of the interplanetary background during periods of moderate to high
solar activity.
---------------------------------------------------------
Title: Solar Ca II H and K Line Variations: The Sun as a Star
Authors: Cook, J. W.
1981BAAS...13..877C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Mass and Energy Balance in the 1973 August 9 Flare
Authors: Cook, J. W.; Dere, K. P.
1981BAAS...13..554C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: <SUP>6.7</SUP>Li Optical-Model Parameters
Authors: Cook, J.
1981ADNDT..26...19C Altcode:
A compilation is presented of optical-model parameters obtained
from an extensive survey of the literature from 1968 to 1981 on the
elastic-scattering cross-section distributions of <SUP>6,7</SUP>Li.
---------------------------------------------------------
Title: Comment on 'Variability of the far-infrared solar temperature
minimum with the solar cycle'
Authors: Cook, J. W.; Brueckner, G. E.; Vanhoosier, M. E.
1980A&A....92L...7C Altcode:
We compare the solar cycle variation of the full disk brightness
temperature minimum in the far-infrared reported by Müller
et al. (1980) to the variation found in the far-ultraviolet
T<SUB>min</SUB> continuum. The far-ultraviolet observations suggest
that the far-infrared variability should be nearer 9,-60 K than the
value of 200 K reported by Müller et al. (1980), whose solar cycle
variation is comparable to their measurement error.
---------------------------------------------------------
Title: HRTS Observations of Solar Fine Structure in the
T<SUB>min</SUB> Region
Authors: Cook, J. W.; Brueckner, G. E.; Bartoe, J. -D. F.
1980BAAS...12..916C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A useful function-fitting programme
Authors: Cook, J.
1980Obs...100...79C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Variability of the solar flux in the far ultraviolet
1175-2100 Å
Authors: Cook, J. W.; Brueckner, G. E.; Vanhoosier, M. E.
1980JGR....85.2257C Altcode:
We examine the expected range of variability over the solar cycle
of the far UV flux (irradiance) in selected lines and continua
within the wavelength range 1175-2100 Å which results from a simple
two-component model of the full-disk flux. We determine contrast factors
I(plage)/I(quiet region) for various lines and continua and estimate
the fraction of the disk that is covered by plages at various times in
the solar 11-year cycle. We assume (1) that enhanced far UV emission
arises from the same plage areas visible in Ca II emission, (2) that
our contrast values are typical, and (3) that both the plage and quiet
region intensities per unit surface area remain constant over the solar
cycle, so that flux variability is caused only by a greater or lesser
fraction of surface area covered by plages. We discussed available
observational evidence for these assumptions. Our results are in good
agreement with the Lα fluxes published by Vidal-Madjar [1975] and the
recent broadband observations by Hinteregger (private communication,
1979), but they are in disagreement with the flux variability reported
by Health and Thekaekara [1977] over the 1700-3000-Å range.
---------------------------------------------------------
Title: Latitudinal Anisotropy of the Solar Far Ultraviolet Flux:
Effect on the Lα Sky Background
Authors: Cook, J. W.; Meier, R. R.; Brueckner, G. E.; Vanhoosier, M. E.
1980BAAS...12..544C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Plages and the Interpretation of Stellar Ca II H and
K Line Variations in Late Type Dwarfs
Authors: Cook, J. W.
1980BAAS...12..520C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The chromosphere and transition region
Authors: Canfield, R. C.; Brown, J. C.; Craig, I. J. D.; Brueckner,
G. E.; Cook, J. W.; Doschek, G. A.; Emslie, A. G.; Machado, M. E.;
Henoux, J. -C.; Lites, B. W.
1980sfsl.work..231C Altcode: 1980sofl.symp..231C
The physical processes occurring as a result of the transfer of
energy and momentum from the primary solar flare energy release site
in the corona to the underlying chromosphere and transition region
during the course of the flare are investigated through a comparison
of theoretical models and observational data. Static, dynamic and
hydrodynamic models of the lower-temperature chromospheric flare are
reviewed. The roles of thermal conduction, radiation, fast particles
and mass motion in chromosphere-corona interactions are analyzed on
the basis of Skylab UV, EUV and X-ray data, and empirical and synthetic
models of the chromospheric and upper photospheric responses to flares
are developed. The canonical model of chromospheric heating during
flares as a result of primary energy release elsewhere is found to be
justified in the chromosphere as a whole, although not entirely as the
temperature minimum, and a simplified model of horizontal chromospheric
flare structure based on results obtained is presented.
---------------------------------------------------------
Title: Mass Flow and Energy Balance in a Solar Flare
Authors: Cook, J. W.; Dere, K. P.
1979BAAS...11..678C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Skylab observations of the Al I autoionization lines lambda
1932 and lambda 1936 during a solar flare.
Authors: Cook, J. W.
1979ApJ...234..378C Altcode:
Observations are presented of the Al I autoionization lines gamma 1932
and gamma 1936 during the H alpha class SN subflare of 1973 August 9,
obtained from the NRL slit spectrograph aboard Skylab. These profiles
are compared with observations from an active-region plage and with
the quiet-sun observations of McAllister. Line profiles through
model flare and quiet-sun atmospheres are computed assuming local
thermodynamic equilibrium. The Al I autoionization lines are sensitive
to the conditions just below the temperature-minimum region of the model
atmosphere, and the observations support evidence that increased heating
of this region occurs during flares. It shown, using observations
from three additional flares, that excess flare heating down to the
T<SUB>min</SUB> region probably occurs only near loop footpoints. The
behavior of Fe and Fe II lines in the 1920 A range is also discussed.
---------------------------------------------------------
Title: Solar C III line intensity ratios observed from Skylab.
Authors: Cook, J. W.; Nicolas, K. R.
1979ApJ...229.1163C Altcode:
Solar observations of C III line intensity ratios are analyzed which
were obtained by the Naval Research Laboratory extreme-ultraviolet
slit spectrograph on Skylab from quiet and active regions, coronal
holes, prominences, and a flare. Electron densities are determined by
comparing the observed intensity ratios to their theoretical variation
as a function of electron density and temperature. Both isothermal line
ratios that are evaluated at a characteristic emitting temperature and
ratios that are integrated through the temperature and density structure
of a model solar atmosphere are calculated. The density-sensitive
ratios R(Si IV 1402/C III 1908) and R(Si III 1892/C III 1908) are also
used to derive additional values of electron density. It is found that
the ratios R(C III 1247/C III 1908), R(Si IV 1402/C III 1908), and
R(Si III 1892/C III 1908) give consistent values of electron density
for each feature. The C III 1908-A, Si III 1892-A, and Si IV 1402-A
lines have recently been observed from the IUE satellite in spectra
of late-type stars, and can serve as practical density diagnostics
that are independent of assumptions about the stellar surface gravity.
---------------------------------------------------------
Title: The decay of the 1973 August 9 flare.
Authors: Dere, K. P.; Cook, J. W.
1979ApJ...229..772D Altcode:
The state and evolution of the decay-phase plasma from a compact solar
flare that occurred on August 9, 1973, are investigated on the basis of
XUV and X-ray observations from Skylab and Solrad 9. Density-sensitive
line ratios are used to determine the electron density over the
temperature range from 30,000 to 5 million K, and the differential
emission measure in the temperature interval from 30,000 to 20 million
K is derived for several times in the decay phase. The morphology of the
flare is discussed, including its relation to the observed photospheric
magnetic field. The sequential formation of new loops during the decay
phase is emphasized as an essential element for understanding the
decay phase of the flare. This idea is developed further by comparing
the observed differential emission measure with that predicted by
a semiempirical model which considers the sequential formation of
isothermal loops that cool by radiation and thermal conduction.
---------------------------------------------------------
Title: EUV observations of quiescent prominences from Skylab.
Authors: Moe, O. K.; Cook, J. W.; Mango, S. A.
1979SoPh...61..319M Altcode:
We report measurements of line intensities and line widths for three
quiescent prominences observed with the Naval Research Laboratory slit
spectrograph on ATM/Skylab. The wavelengths of the observed lines
cover the range 1175 Å to 1960 Å. The measured intensities have
been calibrated to within approximately a factor 2 and are average
intensities over a 2 arc sec by 60 arc sec slit. We derive nonthermal
velocities from the measured line widths. The nonthermal velocity
is found to increase with temperature in the prominence transition
zone. Electron densities and pressures are derived from density
sensitive line ratios. Electron pressures for two of the prominences are
found to lie in the range 0.04-0.08 dyn cm<SUP>−2</SUP>, while values
for the third and most intense and active of the three prominences
are in the range 0.07-0.22 dyn cm<SUP>−2</SUP>.
---------------------------------------------------------
Title: A semiempirical model of the upper flare chromosphere.
Authors: Lites, B. W.; Cook, J. W.
1979ApJ...228..598L Altcode:
Ultraviolet spectra of the August 9, 1973, flare taken with the NRL
S082B spectrograph aboard ATM/Skylab have been analyzed to derive
a semiempirical model of the flare chromosphere between 5500 and
100,000 K. The hydrogen radiative transfer is solved to obtain a
self-consistent set of physical conditions within the flare atmosphere,
from which line profiles and continua of the ions C I, C II, C III,
and C IV are synthesized and compared with the observations. The model
exhibits a rapid rise in the temperature at a column mass of 0.0003
g/sq cm. There is some evidence for much of the C III line emission's
arising from flare kernels not exceeding 3 arcsec in size, and the C
IV line profiles indicate the possibility of nonequilibrium excitation.
---------------------------------------------------------
Title: The Variability of the Solar Ultraviolet Radiation in the
Wavelength Region 1200-2100 Å
Authors: Vanhoosier, M. E.; Cook, J.; Brueckner, G. E.
1979BAAS...11..421V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Skylab Observations of the A1 I Autoionization Lines λ 1932
and λ 1936 During a Solar Flare
Authors: Cook, J. W.
1979BAAS...11Q.439C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: EUV continua of solar flares 1420 - 1960 Å.
Authors: Cook, J. W.; Brueckner, G. E.
1979ApJ...227..645C Altcode:
Measurements of absolute continuum intensities in the wavelength
range 1420-1960 A are presented for the SN subflare of 1973 August
9 and the 2B flare of 1973 September 7, observed from the NRL
spectrograph aboard Skylab. Continuum measurements are also given for
two active-region plages, which are used for background nonflaring
levels. Major enhancement of the flare continuum intensity above the
plage backgrounds occurs in the Si I 3P and 1D continua. The observed
brightness-temperature minimum of the plages is approximately 310
K above the quiet-sun minimum, and occurs at longer wavelength. The
earliest flare brightness-temperature minima are approximately 200 K
above the plage minimum, and also at longer wavelength. The observed
decay time of the flare brightness temperature, which is comparable
to the Solrad 9 X-ray decay time, is much longer than the Ulmschneider
radiative relaxation time for the 1973 September 7 flare and marginally
longer for the 1973 August 9 flare, suggesting continuous excess heating
of the plage temperature minimum region throughout the period of our
flare observations.
---------------------------------------------------------
Title: ATM evidence for a nonthermal proton/electron energy flux
ratio in solar flares.
Authors: Canfield, R. C.; Cook, J. W.
1978ApJ...225..650C Altcode:
An observational search has been carried out for asymmetry in the
wings of L-alpha during flares, produced by beams of nonthermal protons
injected into the chromosphere from the corona as suggested by Orrall
and Zirker (1976). The data base is the ATM/Skylab EUV spectrograms from
the NRL S082B spectrograph. The asymmetries expected to be present in
the normal thermal profile are discussed, and detailed consideration
is given to the flare that occurred at 1551 UT on August 9, 1973,
which was observed during the nonthermal phase. In this flare only
very small L-alpha asymmetries are observed, not large enough to be
statistically significant. It is shown that this result, combined
with microwave radio data for information on nonthermal electrons,
implies that the energy flux of nonthermal protons injected into the
chromosphere at energies above 20 keV is less than approximately 0.02
times that of electrons of the same energy range in the observed events.
---------------------------------------------------------
Title: ATM Evidence for a Low Non-Thermal Proton/Electron Energy
Flux Ratio in Solar Flares.
Authors: Canfield, R. C.; Cook, J. W.
1978BAAS...10..441C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar C III Line Ratios Observed from Skylab.
Authors: Cook, J. W.; Nicolas, K. R.
1978BAAS...10R.439C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectrophotometry of HDE 226868 (Cygnus X-1)
Authors: Cook, John William
1978shc..book.....C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectrophotometry of HDE 226868 (Cygnus X-1)
Authors: Cook, John William
1977PhDT.......244C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectrophotometry of HDE 226868
Authors: Cook, J. W.
1977PhDT.........1C Altcode:
Spectra of HDE 226868, the optical counterpart of the X-ray source
Cygnus X-1, were obtained at a dispersion of approximately 84
A/mm. Plates were scanned on a microdensitometer and the resulting
density measurements converted to relative intensities using standard
photometric calibration methods. The resulting spectra, representing
a region from redward of H alpha to blueward of H delta, were reduced
to rectified spectra in continuum units. Selected lines were examined,
and the line profiles and equivalent widths obtained. The equivalent
widths of hydrogen and helium absorption lines appear consistent
with a normal 09.7 Iab star. Parameters of the Cygnus X-1 system
are calculated and a qualitative model for the optical behavior
examined. The difficulties in determining electron temperature and
density in the region of optical emission are discussed.
---------------------------------------------------------
Title: Hughes's Induction Balance
Authors: Cook, J.
1887Natur..36R.605C Altcode:
HAVING just made a Hughes's induction balance, I have, in the course
of some experiments with it, observed what was new to me, for I
have not seen it mentioned in any account of the balance. I take
the liberty, therefore, of asking through your columns whether the
explanation resolves itself into the difference between paramagnetic
and diamagnetic substances. The apertures of my bobbins are 1½ inch
in diameter; my primary current is from three Daniell's, and the break
is a bent steel spring whose free point just grazes the surface of a
mercury cup, so that the merest touch with a finger causes a series
of regular breaks. Now, if I place an iron or steel disk, or ring,
such as a key-ring, inside the aperture, the telephone sounds loudly
if the plane of the disk or ring is at right angles to the plane of
the coils; but very very faintly if it is parallel to the plane of the
coils. On the other hand, if a disk, or ring, or coil of wire, of any
of the diamagnetic metals-copper, brass, zinc, silver, gold, aluminium,
lead-be used, the telephone sounds loudly if the plane of the disk or
ring he parallel to the plane of the coils; but very faintly, if at all,
when it is perpendicular to the plane of the coils. Further, if a short
bar of soft iron, or of nickel, be inserted so that the length of the
bar is parallel to the plane of the coils, almost no sound is heard;
but if it be turned through a right angle so as to be perpendicular
to the plane of the coils, the sound is a maximum. Have we in this
simple instrument the ready means of distinguishing paramagnetic from
diamagnetic substances?
---------------------------------------------------------
Title: An Account of the Flowing of the Tides in the South Sea, as
Observed on Board His Majesty's Bark the Endeavour, by Lieut. J. Cook,
Commander, in a Letter to Nevil Maskelyne, Astronomer Royal, and
F. R. S.
Authors: Cook, J.
1772RSPT...62..357C Altcode:
No abstract at ADS