Author name code: mohler
ADS astronomy entries on 2022-09-14
author:"Mohler, Orren C."
------------------------------------------------------------------------
Title: A New Fit Line to Homogeneous Freezing Onsets of Aqueous
H2SO4 Aerosol Particles at Cirrus Conditions
Authors: Schneider, J.; Höhler, K.; Wagner, R.; Schorr, T.; Mohler,
O.; Leisner, T.
Bibcode: 2020AGUFMA140...08S
Altcode:
Cirrus and mixed phase clouds strongly influence the weather and
climate on our planet. Due to their microphysical and optical
properties, they contribute to the global energy budget of the
Earth's atmosphere and impact the hydrological cycle. In the lower
troposphere, the formation of the ice phase is only triggered by
solid aerosol particles, whereas in the colder upper troposphere
and lower stratosphere, homogeneous nucleation of supercooled liquid
aerosol particles is also of importance. Therefore, the knowledge about
homogeneous freezing processes are essential to understand and formulate
cirrus cloud processes. During several laboratory measurement
campaigns in the past years, the homogeneous freezing of sulphuric
acid solution droplets has been investigated in the cloud and aerosol
chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere)
at the Karlsruhe Institute of Technology. Inside the AIDA chamber,
conditions of atmospheric cirrus with temperatures down to 190 K and
high ice supersaturations can be realized. The instrumentation at
the AIDA provides continuous records of thermodynamic quantities and
aerosol properties and allows for a sensitive detection of ice crystal
formation and growth. We summarize a comprehensive collection of AIDA
experiments with aqueous sulphuric acid aerosols to review homogeneous
freezing processes at cirrus formation conditions simulated in the cloud
chamber. At temperatures below about 210 K, we observe homogeneous
nucleation to occur at higher supersaturations than predicted by
the water-activity-based parameterization suggested by Koop et al.,
2000. The systematic discrepancy increases with decreasing temperature,
and is observed in the more recent data sets of AIDA homogeneous
freezing experiments as well as in the older measurements. Based
on these observations, we review the description of homogeneous ice
nucleation in the cirrus temperature regime and discuss a new fit line
to the onset of homogeneous freezing to be applied in atmospheric
models. Koop, T., Luo, B. P., Tsias, A., and Peter, T.: Water
activity as the determinant for homogeneous ice nucleation in aqueous
solutions, Nature, 406, 611-614, 2000.
Title: Study of the Post-Flare Loops on 1973JUL29 - Part Four -
Revision of T and NE Values and Comparison with the Flare of 1980MAY21
Authors: Švestka, Z.; Dodson-Prince, H. W.; Martin, S. F.; Mohler,
O. C.; Moore, R. L.; Nolte, J. T.; Petrasso, R. D.
Bibcode: 1982SoPh...78..271S
Altcode:
We present revised values of temperature and density for the flare
loops of 29 July 1973 and compare the revised parameters with those
obtained aboard the SMM for the two-ribbon flare of 21 May 1980. The 21
May flare occurred in a developed sunspot group; the 29 July event was a
spotless two-ribbon flare. We find that the loops in the spotless flare
extended higher (by a factor of 1.4-2.2), were less dense (by a factor
of 5 or more in the first hour of development), were generally hotter,
and the whole loop system decayed much slower than in the spotted flare
(i.e. staying at higher temperature for a longer time). We also align
the hot X-ray loops of the 29 July flare with the bright Hα ribbons
and show that the Hα emission is brightest at the places where the
spatial density of the hot elementary loops is enhanced.
Title: X-Ray Observations of Two Different Systems of "Post Flare"
Loops
Authors: Svestka, Z.; Dodson-Prince, H. W.; Mohler, O. C.; Martin,
S. F.; Moore, R. L.; Nolte, J. T.; Petrasso, R. D.
Bibcode: 1981BAAS...13R.542S
Altcode:
No abstract at ADS
Title: Examples of problem flares or situations in past
solar-terrestrial observations
Authors: Dodson, H. W.; Hedeman, E. R.; Mohler, O. C.
Bibcode: 1979stp.....1..385D
Altcode:
Instances of solar activity are discussed in terms of their relative
interference with making solar terrestrial observations. Unexpected
flares of significance are reported and the geophysical effects of
these flares are noted.
Title: Study of geomagnetic storms and solar in the years of
increasing solar activity, cycles 19 and 20, 1955-1957, 1965-1968
Authors: Dodson-Prince, H. W.; Hedeman, E. R.; Mohler, O. C.
Bibcode: 1978STIN...7923874D
Altcode:
Solar circumstances prior to the 245 geomagnetic storms with maximum
values of 3-hourly Kp greater than or equal to 5 in
the years 1955-1957 and 1965-1968 have been evaluated. The years
studied were those of increasing activity in solar cycles 19 and
20. To assist in this study, a Comprehensive Flare Index based on
the flare's H-alpha, ionizing, and radio frequency radiation has
been used. Of the 245 storms in the seven years studied 62% were
considered to be flare-associated, 30% were primarily sequential,
and only 8% remained as problem cases. Most of the severe storms were
associated with flares. Sequential storms were primarily of moderate
severity. The most important flares tended to be associated with the
most severe storms. Flare criteria that include ionizing and radio
frequency emissions as well as optical data apparently assist in the
recognition of flares associated with subsequent geomagnetic storms.
Title: Energetic solar particle and geomagnetic storm study
Authors: Mohler, O. C.; Dodson-Prince, H. W.; Hedeman, E. R.
Bibcode: 1978STIN...7923875M
Altcode:
This final report consists of a brief administrative statement
describing the purpose and progress of the research, the funding
of the research, the personnel who participated in the program,
and brief description of the scientific reports prepared under this
contract. Three scientific reports have been completed: Survey and
Comparison of Solar Activity and Energetic Particle Emission in 1970;
Solar and Geophysical Associations with the Principal Energetic Particle
Events in 1971 and 1972; and Study of Geomagnetic Storms and Solar
Flares in the Years of Increasing Solar Activity in Cycles 19 and 20
(1955-1957; 1965-1968).
Title: Survey and comparison of solar activity and energetic particle
emission in 1970
Authors: Dodson-Prince, H. W.; Hedeman, E. R.; Mohler, O. C.
Bibcode: 1977STIN...7822013D
Altcode:
Solar activity in 1970 was at a relatively high level with the number
of major flares and important centers of activity reaching maximum
numbers for all of cycle 20. Satellite data, primarily from Explorer
41, provided evidence for at least 152 distinct energetic particle
enhancements during the year. These events have been compared with
concurrent solar activity. All but one of the 13 particle events
associated with Polar Cap Absorption in 1970 have been identified
with specific solar flares. For the 50 proton events with energies
19-80 or =60 MEV, 72 percent have reasonably sure solar or geophysical
sources. Of the 59 purely low energy particle events (1-10 MEV) only
39% could be assigned probable solar associations. For the numerous
low-energy particle events without confident solar associations, there
were assorted time coincidences with geomagnetic storms, sector boundary
passages, the development of new regions on the disk, and the central
meridian passage of significant centers of activity. At the present
time, the significance of these solar and geophysical phenomena for
particle enhancement is not known.
Title: Comparison of activity in solar cycles 18, 19, and 20.
Authors: Dodson, H. W.; Hedeman, E. R.; Mohler, O. C.
Bibcode: 1974RvGSP..12..329D
Altcode: 1974RvGeo..12..329D
No abstract at ADS
Title: The New Michigan 52-inch Reflector
Authors: Wehinger, Peter A.; Mohler, Orren C.
Bibcode: 1971S&T....41...72W
Altcode:
No abstract at ADS
Title: Observatories of the University of Michigan, Ann Arbor,
Michigan. Report 1969-1970.
Authors: Mohler, O. C.
Bibcode: 1971BAAS....3..131M
Altcode:
No abstract at ADS
Title: University of Michigan Observatories, Ann Arbor,
Michigan. Report 1968-1969.
Authors: Mohler, O.
Bibcode: 1970BAAS....2...78M
Altcode:
No abstract at ADS
Title: Revision of the Ultraviolet Solar Spectrum in the Range
3650-3000 a
Authors: Mitchell, Walter E., Jr.; Mohler, Orren C.
Bibcode: 1969ApJS...18..379M
Altcode:
This paper tabulates the wavelengths of 1987 features in the range
6f the solar spectrum A. These features come out of the detailed
examination and intercomparison of several sets of high-dispersion
photoelectric records and the Second Revised Rowland. Most of the listed
features (a) are new (551), (b) agree sufficiently well in wavelength to
be considered to confirm features of the Second Revised Rowland (557),
or (c) are features of the Second Revised Rowland whose existence
is called into question (237). Small relocations of wavelength are
indicated for 172 features of the Second Revised Rowland. Of the new
lines, equivalent widths have been measured for 198 which suffer the
least blending. Their strengths range from 16.6 down to 0.2 mA and
average 3.2 mA. A total of 726 identifications are proposed for 476
of the new or relocated lines. A total of 1911 comments are given
as to their visibility and appearance on the photoelectric records
of these lines and a number of the weakest features of the Second
Revised Rowland.
Title: The Observatories of the University of Michigan, Ann Arbor,
Michigan. Report 1967-1968.
Authors: Mohler, O. C.
Bibcode: 1969BAAS....1...65M
Altcode:
No abstract at ADS
Title: McMath-Hulbert Observatory of the University of Michigan
Authors: Mohler, Orren C.; Dodson, Helen W.
Bibcode: 1968SoPh....5..417M
Altcode:
No abstract at ADS
Title: The Abundance of Lead in the Sun
Authors: Ross, John; Aller, Lawrence H.; Mohler, Orren C.
Bibcode: 1968PNAS...59....1R
Altcode:
No abstract at ADS
Title: CA i Lines in Auto-Ionization in the Solar Spectrum.
Authors: Mitchell, Walter E., Jr.; Mohler, Orren C.
Bibcode: 1965ApJ...141.1126M
Altcode:
It is proposed that (1) the three broad, weak depressions at XX 6362,
6344, and 6319 in the solar spectrum correspond to the transitions in
a multiplet of the Ca I atom and (2) their diffuse character results
from the fact that the atom is subject to auto-ionization when it is
in the upper state of the transition.
Title: The Observatories of the University of Michigan.
Authors: Mohler, O. C.
Bibcode: 1963AJ.....68..646M
Altcode:
No abstract at ADS
Title: Robert Raynolds McMath, 1891-1962.
Authors: Mohler, Orren C.
Bibcode: 1962PASP...74..282M
Altcode:
No abstract at ADS
Title: Solar Instruments.
Authors: McMath, R. R.; Mohler, O. C.
Bibcode: 1962HDP....54....1M
Altcode:
Instruments for the measurement of the total solar radiation
Radio telescopes The image-forming instruments of solar astronomy
Construction and housing of solar telescopes Auxiliary instruments
for solar telescopes Instruments for the observation of solar eclipses
Some instrumental problems of solar observation Bibliography
Title: Telescope Driving Mechanisms
Authors: McMath, R. R.; Mohler, O. C.
Bibcode: 1961tele.book...62M
Altcode: 1961S&SS....1...62M
No abstract at ADS
Title: Fraunhofer Lines and Heights in the Sun's Atmosphere
Authors: Mohler, Orren C.
Bibcode: 1960S&T....20..124M
Altcode:
No abstract at ADS
Title: The Measutement of the Local Doppler Shift of Fraunhofer Lines.
Authors: Goldberg, Leo; Mohler, Orren C.; Unno, Wasaburo; Brown,
Jacqueline
Bibcode: 1960ApJ...132..184G
Altcode:
Well-defined spectra showing the Doppler shift arising from
small-scale motions in the solar atmosphere were obtained with the
vacuum spectrograph of the McMath-Hulbert Observatory during August
and September, 1955. These spectra have been measured, and the local
Doppler shifts of several solar absorption lines have been determined
at various positions on the disk of the sun. The average value of the
random turbulent velocity is found to be 0.33 km/sec for elements with
an average diameter of 5.5 seconds of arc (4000 km). However, the values
of the random turbulent velocity, as well as other characteristics,
show systematic differences between weak and strong lines. Metallic
lines formed at average effective optical depths, r(SO0O) larger than
0.2, show smaller velocities than the average. Their r.m.s. velocities
monotonically increase toward the limb of the sun (1.0> >
0.6). Stronger lines (roooo <0.2) show systematically larger
values of the r.m.s. velocities with no appreciable center-to-limb
variation. Near the limb of the sun ( = 0.35) all the measured lines
show smaller r.m.s. velocities than at j# = 0.58. This may be caused
by the lack of resolution of small elements in the neighborhood of the
solar limb. These results suggest that the large-scale motion in the
upper photosphere decreases as the limb of the sun is approached. They
also suggest that a rising element of the atmosphere is statistically
followed by a falling element in the same region.
Title: The Growth of Solar Spectroscopy
Authors: Mohler, Orren C.
Bibcode: 1960SouSt..18..129M
Altcode:
No abstract at ADS
Title: Solar Features Associated with Ellerman's "Solar Hydrogen
Bombs"
Authors: McMath, Robert R.; Mohler, Orren C.; Dodson, Helen W.
Bibcode: 1960PNAS...46..165M
Altcode:
No abstract at ADS
Title: Measurements of the K-Line in Spectra of Sunspots.
Authors: Mohler, Orren C.
Bibcode: 1960AJ.....65Q..55M
Altcode:
Line in Spectra of Sunspots. ORREN C. MoBLER, McMath-Hulbert
Obseo'vatory. The structure of the center of the K4ine in spectra of
sunspots has been observed on a number of occasions. The structure
of the K-line exactly over the umbra most frequently shows a double
reversal much like that present in the normal solar disk with the
difference that the reversal in the umbra of a sunspot consists of
two narrow components separated by about 4 to 61 the separation of the
emission components that appear in normal disk spectra. The next most
frequent structure visible in sunspots is a featureless line with a
width approximately double that of the reversed emission components. In
a small number of spots the structure is so completely disorganized that
no general features have been found. In a normal plage region near the
center of the disk the separation of the brightly reversed components
of the K4ine averages less than 0.75A. The separation varies linearly
from its value in the adjacent plage to the narrow separation (about
0.090A) observed in the umbra of the sunspot. These values should be
compared with the separation for the normal disk of about 0.600A. The
intensities of the emission components in the sunspot spectra are very
low, approximately 4 the intensity of the K3 emission components in
the undisturbed center of the solar disk. Often the emission seems
to be completely absent unless special care is used in making the
photographic observations.
Title: The Double Reversal in the Cores of the Fraunhofer H and
K Lines.
Authors: Goldberg, Leo; Mohler, O. C.; Müller, Edith A.
Bibcode: 1959ApJ...129..119G
Altcode:
Observations are presented of the profiles of the central doubly
reversed cores of the H and K lines of Ca ii in the Fraunhofer
spectrum. The profiles were obtained photoelectrically with the
vacuum spectograph of the McMath-Hulbert Observatory at five different
points on the solar disk from M = 1.0 to = 0.2. At the center of the
disk the central intensities of H and K are 2.95 and 2.36 per cent,
respectively, in terms of the neighboring continuous spectrum near
X 4000. At = 0.2 the central intensities are 2.41 and 2.01 per cent
for H and K, respectively, also with reference to the continuum at
X 4000 at the center of the disk. The relative intensity ratio H:
K is found to be constant in the inner absorption core and nearly
the same for all values of . This suggests that the logarithm of
the source function varies linearly with the logarithm of Nh, the
number of Ca ii atoms per square centimeter above height, h, in the
chromosphere. The Doppler widths were derived by two methods, namely,
(1) by an intercomparison method which is independent of the source
functiop and (2) by using the depth-dependence of the source function
and the shapes of the profiles. The Doppler widths thus found increase
from 0.063 A at = 1.0 to 0.110 A at = 0.2. The derived Doppler widths
and source function are employed to calculate the profiles of the
inner cores of H and K. Extremely good agreement is found between the
calculated and the observed central cores at all five values of . The
variation in the Doppler widths from center to limb is discussed,
and it is concluded that the widening of the profiles to the limb
is caused by an increase in turbulence with height, combined with
anisotropy. The comparison of the Doppler widths derived for Ca ii with
results previously obtained for the X 10830 line of He I supports the
hypothesis that the chromosphere is heterogeneous and is composed of
regions of quite different physical properties.
Title: Solar Research Reported at Moscow
Authors: Mohler, Orren C.
Bibcode: 1958S&T....18...77M
Altcode:
No abstract at ADS
Title: The Profile of Hα during the Limb Flare of February 10, 1956.
Authors: Goldberg, Leo; Mohler, Orren C.; Muller, Edith A.
Bibcode: 1958ApJ...127..302G
Altcode:
Profiles of the Ha line in a very bright loop prominence associated
with the great limb flare of February 10, 1956, show pronounced violet
asymmetries. Despite the fact that the centers of different profiles,
made at several points in the line on two different exposures, exhibit
relative Doppler displacements as high as 0.8 A, the shapes of all
the profiles can be accounted for by the superposition on the main Ha
profile of an additional component centered between 1.5 and 2.0 A to
the violet. The possibility is discussed that the asymmetry may have
been caused by the presence of abnormal amounts of deuterium, presumably
generated by nuclear reactions during the flare event. It is concluded
that, although the evidence for deuterium is not conclusive, it would be
extremely important to observe other similar flareassociated prominences
in the future, with modern high-dispersion spectrographs. Observations
should also be made simultaneously on at least one additional line of
an element other than hydrogen, in order to eliminate velocity effects.
Title: Observation of solar "points".
Authors: Mohler, Orren C.; Dodson, Helen W.
Bibcode: 1958AJ.....63R.309M
Altcode:
There is a type of object on the sun visible through a Lyot Ha filter
and photographed on hydrogen and calcium spectroheliograms that is the
source of the spectroscopic feature called "hydrogen bombs" by Ellerman
(1917) and "moustaches" by Severny (1956). These objects were observed
through the filter by Lyot (I 944) and called by him "points." We
shall adopt his nomenclature because it indicates the small size and
usually circular shape of the phenomenon. Points are identified by their
characteristic spectrum, viz., brilliant emission streaks extending
several angstroms on either or both sides of Ha but not crossing
it. Emission on the violet side is generally more intense than that on
the red. At the McMath-Hulbert Observatory points are observed by two
methods. (I) They are seen visually in a Lyot-Ha filter and then placed
on the slit of the vacuum spectrograph for definitive identification
and spectrographic study. (2) The points are recorded on series of 15
spectroheliograms made at different wave lengths, systematically spaced
within 3A on either side of the center of Ha or the K-line. Points are
photographed with especial ease on K spectroheliograms. Our observations
show that points occur generally on the outer edge of the penumbra of
spots. They are very small, only fractions of seconds of arc. They are
numerous three or four per spot. Average life times are of the order of
nine minutes, but may be as short as two. They are recurrent. Points
frequently have been observed to be at the base of small active dark
flocculi. Our observations to date indicate little or no positional
relationship between points and major flares, even though the latter
have broken out in the field during well controlled observations of
points. The generality of points in the neighborhood of inactive as
well as active spots suggests that they should be considered as part
of normal spot development. Ellerman, F. 1917, Ap. J. 46, 298. Lyot,
B. 1944, Ann. Astroph. 7, 31. Severny, A. B. 1956, Observatory, 76,
241. McMath-Hulbert Observatory, University of Michigan, Pontiac, Mich.
Title: A Connexion Between the Granulation and the Structure of the
Low Chromosphere
Authors: Goldberg, Leo; Mohler, Orren C.; Brown, Jacqueline D.
Bibcode: 1957Natur.179..369G
Altcode:
PHOTOGRAPHS of the solar spectrum made with the vacuum spectrograph
of the McMath-Hulbert Observatory have revealed a variety of
interesting and complex features in the structures of the Fraunhofer
lines1. The appearance of the hydrogen line cores suggests
an underlying, diffuse component that evidently originates in the
photosphere, upon which are superposed a series of streaks that must
be of chromospheric origin. The weaker metallic lines (of Rowland
intensity less than about 10) also fluctuate in width and intensity
and have a characteristic zig-zag appearance caused by the Doppler
shifts of ascending and descending gas columns which are associated
with the granulation in the photosphere.
Title: A High-Resolution Isophotometer.
Authors: Mohler, O. C.; Pierce, A. K.
Bibcode: 1957ApJ...125..285M
Altcode:
A modification of a microdensitometer that converts the instrument
into an isophotometer is described. There are two advantages of the
modified instrument. First, it is completely automatic in operation;
second, the accuracy of the intensity levels can be made very high
Title: A connection between the granulation and the structure of
the low chromosphere.
Authors: Goldberg, Leo; Mohler, Orren C.; Brown, Jacqueline D.
Bibcode: 1957AJ.....62Q..92G
Altcode:
Isophotometer tracings of a plate of the Fraunhofer spectrum in the
region of H~ show an interesting connection between the structures of
the H~ line and of the Fei line N4859.747 (Rowland intensity 4). The
Hfl line is resolved into structures as small as 3" or less, and the
detail in the neighboring metallic lines is equally good. Over an
interval of about 6' on the disc, 41 features in the H~ line were
measured for radial velocity with respect to the underlying photo-
spheric component of the line core. Similarly, velocity shifts
were measured in the neighboring Fei line at points in the line
corresponding to the positions of the 41 H~ structures. The results
obtained are as follows: i) There is a remarkable association of the H~
structures with violet shifts in the Fei line. Of the 41 measured H~
structures, 30 are associated with violet shifts in the Fei line,
7 with red shifts, and 4 with zero shifts; 2) The H~ structures are
themselves predominantly shifted to the violet. The statistics show
26 violet shifts, I I red shifts, and 4 zero shifts; 3) The velocity
spread in the Hfl line is about three times as great as that in the
Fei line, the rms values being 0.64 and 0.24 km/sec, respectively. It
is tentatively suggested that the violet- shifted structures observed
in the hydrogen lines represent extensions of the granular columns
into the low chromosphere. The inequality between the negative and
positive shifts in the H~ line may be attributed to the fact that on
the average the ascending columns are at a somewhat higher temperature
than the descending columns. Since a difference of only a few hundred
degrees in temperature causes an enormous difference in the population
of the two-quantum level of hydrogen, the relative absence of structures
with descending velocities could be due to vanishingly small optical
depth in the cooler columns. Further clarification may be expected
from studies now being carried on with lines covering a large range
of optical depth and excitation characteristics, including Ha, the K
line of Ca+, the D lines of sodium, and the Mg b lines. University of
Michigan Observatory, Ann Arbor, Mich.
Title: Preliminary Results with a Vacuum Solar Spectrograph.
Authors: McMath, Robert R.; Mohler, Orren C.; Pierce, A. Keith;
Goldberg, Leo
Bibcode: 1956ApJ...124....1M
Altcode:
New observations of the solar spectrum with a high-resolution vacuum
spectrograph reveal a wealth of detail in the cores of all Fraunhofer
lines observed both in the normal disk and in areas exhibiting
various kinds of solar activity. The lines show fluctuations in width,
intensity, and position over intervals as small as 2 seconds of arc. A
representative collection of photographs is presented, together
with tentative conclusions derived from inspection and preliminary
measurement. Measurements of Doppler shifts have been carried out in
considerable detail for the two lines Cr X 4626 and Ba+ X 5853. The
random turbulent velocity at the center of the disk is 0 70 km/sec
for the chromium line and O. km/sec for the ionized barium line. For
both lines the random turbulent velocity appears to increase toward
the limb. The velocity shifts observed for the Ha and sodium D lines
are of the same order of magnitude as those of the weaker metallic
lines. The disk observations of the Fraunhofer lines of hydrogen and
ionized calcium seem to he consistent with a qualitative model of the
low chromosphere, consisting of relatively hot clouds of gas and with
cooler regions both above and between the hot regions. Both the K2
emission in ionized calcium and the wide absorption features in Ha
seem to originate in the hot regions; from the appearance of these
line features near the limb it seems that the hot regions contribute
a substantial fraction of the hydrogen and ionized calcium emission
in the very low chromosphere. The profiles of Ha at the extreme limb
and of the K line and other strong metallic lines on the disk favor
the conclusion of Adams and Burwell that central self-reversal is a
general characteristic of most strong chromospheric profiles. The
similarity between the intensity and velocity fluctuations in the
core of the strong magnesium line X 5167 and in those of neighboring
weaker lines implies either a chromospheric origin for the centers of
these weaker lines or the extension of the photospheric granules into
the low chromosphere. The preliminary nature of the foregoing results
is emphasized.
Title: The Width of the Infrared Helium Line in the Solar Spectrum.
Authors: Mohler, Orren C.; Goldberg, Leo
Bibcode: 1956ApJ...124...13M
Altcode:
Measurements of intensity and half-width are reported for the Fraunhofer
line He I 10830 After correction for instrumental broadening and
blending, the width at half4ntensity, averaged over the center of the
disk and the four limbs, is 0.91 A. Within the error of measurement,
the line widths show no center-to4imb variation The line appears
to be broadened entirely by the Doppler effect, with AND = 0.55
A, corresponding to an r.m.s. velocity of about 15 km/sec. If the
broadening is entirely thermal, the kinetic temperature is about 50000
K. Although the line is probably formed in localized hot regions of the
chromosphere, it is not yet clear whether or not the derived velocity
contains a turbulent, as well as a thermal, component.
Title: Doppler Shifts in Solar Granules.
Authors: McMath, Robert R.; Mohler, Orren C.; Pierce, A. Keith
Bibcode: 1955ApJ...122..565M
Altcode:
No abstract at ADS
Title: Observations of the K line in the solar spectrum.
Authors: Mohler, O.
Bibcode: 1955AJ.....60S.173M
Altcode:
Direct photoelectric observations of the K line in the solar spectrum
demonstrate that considerable precision in wave-length measurement
can be attained on the same tracings that are used for photometric
purposes. First results of wave-length measurement of the VK2, K3,
and RK2 components of the K line agree in general with the results
of St. John for the center of the disk, but do not confirm the
center-to-limb variation in wave length. Although the components of
the K line are highly variable in intensity, for all points observed
the VK2 component is always the stronger. VK2 and RK2 approach equality
near the sun's limb, and in plage regions. McMath-Hulbert Observatory,
Univ. of Michigan, Ann Arbor, Mich.
Title: The 50-foot focal length vacuum spectrograph for solar
research.
Authors: McMath, R. R.; Mohler, O. C.; Pierce, A. K.
Bibcode: 1954AJ.....59R.328M
Altcode:
It is plain that an adequate study of the profiles of a large number
of Fraunhofer lines demands a spectrograph of high resolving power
and great linear dispersion. Through the kindness of Drs. I. S. Bowen
and H. W. Babcock we have been able to use one of their fine gratings,
6X8 inches, in our Pfund system.' With this arrangement we immediately
found an asymmetry and variable features in the center of Ha.2 However,
further work on faint solar lines and on the absorption spectrum of
iodine indicated a resolving power lower than anticipated with this
particular grating. Photoelectric traces made by placing the steep
portion of an absorption line or the very steep intensity change at
the zero order on the exit slit of the spectrometer indicated from the
strong random fluctuations of the signal that spectrographic seeing
was the undoubted cause of lowered resolution. For photographic work
the criteria for the design of large stellar spectrographs, as given
by I. S. Bowen,3 require that the resolving power of the photographic
plate be matched to the linear resolving power of the grating at the
focal plane. A photograph taken with a spectrograph approximating this
condition will show considerable graininess if a narrow slit of width
equal to the resolving power is used in the photometer. Where there is
ample light the use of a longer focal length and a larger scale permits
the use of wider microphotometer slits with a gain in smoothness of the
recording with no loss in resolving power. In addition, with the larger
scale spectrograph the slits are mechanically easier to construct and
the effects of dust, defects and non- parallelism of the slit jaws are
percentagewise less. The latter points are of considerable importance in
problems which involve photometry of details of the solar surface that
the slit intersects along its length. However, a longer focal length
aggravates the seeing problem. Following the high resolution work on
Ha and an experimental investigation of our spectrographic seeing,
both at Lake Angelus and at the Snow telescope at Mount Wilson,
Dr. McMath started in January 1954 the design and construction of
a large vacuum spectrograph which would completely eliminate the
spectrograph seeing problem, and which would give adequate scale and
vacuum wave lengths. The design utilizes the 50-foot focal length
off-axis mirror system of the existing McGregor Tower to form an image
of the sun at the first slit of a predisperser before the grating
spectrograph. The optical arrangement of the spectrograph follows
the design described by M. Czerny and A. F. Turner,4 but the mirrors
and grating are now placed in a vacuum tube 52 feet long and 4 feet
internal diameter. Other tube specifications are: Rolled and welded
plate, thickness ~` inch, reinforced with rings every four feet. The
end plates are 14' inches thick and are heavily reinforced with 6-inch
deep ribs of i-inch plate welded to the inside faces. Light from the
entrance slit located behind a quartz field lens which also acts as a
window to the vacuum tank is collimated by a i~-inch spherical mirror
and returned to the grating located several feet inside the head of
the tube. The dispersed beam is focused on the second slit by a second
i~-inch spherical mirror and after passing through a quartz window is
received by a photomultiplier. A third concave i~-inch mirror at the
far end of the tube is arranged so that a short region of the spectrum
can be returned to a photographic plate. All mirrors, and the grating
table, are provided with complete motions in all degrees of freedom
through the use of electrical motors. The final adjustments can be
made by push buttons after the tank has been pumped down and assumed
its slightly altered shape under the atmosphere pressure load of 700
tons. The head of the spectrograph is to be provided with air locks
at every point. The adjustment and repair of the slits,: or of the
photocell, are thus facilitated without destroying the vacuum of the
main tank. A special cassette and air lock will permit a quick plate
change to be made. The tank, constructed by Whitehead and Kales of
Detroit, proved to be vacuum-tight on erection. The first pump-down with
a Kinney vacuum pump, Model VSD-88i I, of 45 cubic feet displacement per
minute, required one hour to reach I cm pressure I mm after two hours. A
pressure of 70 microns has been obtained and it is expected that still
lower values will be achieved after the inside surfaces, painted with
red lead, have occluded their more volatile constituents. Tests have
shown that the rate of pressure rise on the tank is so small, 0.1 mm
rise per 24 hours, that it will be possible to pump out the tank at
night and then to shut off the pump during the operating day. This is
a necessary requirement as the pump, though on an isolated pier with
flexible connection to the tank, carries a perceptible vibration to the
optics. This spectrograph will allow the use of one of Babcock's superb
gratings in the fifth order, and should allow the grating to develop
its full resolving power of about 600,000. The linear dispersion in
the fifth order will be 6.92 mm per angstrom at 5000 A. This dispersion
should make3]possible faint line profile work containing a relatively
small instrumental contribution. The scattered light is to be evaluated
by interferometric and other methods. Precision measurements of profiles
of the stronger lines by photoelectric methods requires an exceptional
sky. Our experience has been that sky transparency over long intervals
of time is so rarely obtained that means of monitoring the background
intensity is very desirable. For this purpose we are planning to use a
modification of the system employed by Hiltner and Code.5 One photocell
will monitor a 200 A interval as passed by the predisperser through
the first slit, and the other will record the spectrum through the
second slit. Reflecting slits of stellite will allow one to guide
accurately on details seen through a Lyot filter which will present
a field bisected by the slit. 5.R. R. McMath and 0. C. Mohler,
J. Opt. Soc. Amer. 39, 903, `949. 2.Ap. J. in press. 3.Ap. J. is6,
5, 5952. 4.Zs. Phys. 6i, 792, 5930. 5.J. Opt. Soc. Amer. 40, `49,
5950. McMath-Hulbert Observatory, University of Michigan, Pontiac, Mich.
Title: Spectroheliographic observations, 1952 February 25
Authors: Dodson, H. W.; Mohler, O. C.
Bibcode: 1953Obs....73..116D
Altcode:
No abstract at ADS
Title: Table of Infrared Solar Lines, 1.4-2.5 μ.
Authors: Mohler, Orren C.; Pierce, A. Keith; McMath, Robert R.;
Goldberg, Leo
Bibcode: 1953ApJ...117...41M
Altcode:
Accurate wave lengths and measurements of equivalent width are given
for 888 solar lines in the spectral region 1. 2.5 . The number of
solar lines has been more than doubled, as compared with previous
preliminary studies in this spectral region. The wave lengths of
the solar lines are referred to those of the Fraunhofer lines in the
visible and very near infrared spectrum by the method of overlapping
orders. The root-mean-square errors of the infrared standard wave
lengths, as derived from repeated measurements of individual lines,
are +0.13 A for the l.6 region and +0.17 A for the 2.3 region. The
equivalent widths are preliminary. The estimated errors are between
10 and 100 per cent, depending upon the degree of blending. About 470
infrared solar lines have been tentatively identified with atoms of H,
K, C, At, Na, Si, Mg, Ca, Ni, and Fe and with first overtone lines
of CO. Comparisons between solar wave lengths and those measured in
the laboratory or predicted from term values reveal somewhat closer
agreement, on the average, between the solar and the predicted values
than between the solar and the laboratory values.
Title: Some Recent Observations of Helium Lines in the Infrared
Solar Spectrum.
Authors: Mohler, Orren C.
Bibcode: 1952ApJ...115..323M
Altcode:
No abstract at ADS
Title: The Abundance of CO in the Sun and in the Earth's Atmosphere
Authors: Goldberg, Leo; McMath, Robert R.; Mohler, Orren C.; Pierce,
A. Keith
Bibcode: 1952PhRv...85..481G
Altcode:
No abstract at ADS
Title: Identification of CO in the Solar Atmosphere
Authors: Pierce, A. K.; Goldberg, L.; McMath, R. R.; Mohler, O. C.
Bibcode: 1952PhRv...85..140P
Altcode:
No abstract at ADS
Title: The Abundance of CO in the Sun and in the Earth's Atmosphere
Authors: Pierce, A. K.; Goldberg, L.; McMath, R. R.; Mohler, O. C.
Bibcode: 1952PhRv...85..418P
Altcode:
No abstract at ADS
Title: Eclipse observations of the structure of the chromosphere
Authors: Mohler, Orren C.
Bibcode: 1951MNRAS.111..630M
Altcode:
Small chromospheric structures that appear in large-scale photographs
of the solar eclipse 1930 October I have been counted. An attempt,
based on the counts, to relate the small chromospheric -structures
to the rice grains of the solar photosphere indicates a connection
between the two classes of observations.
Title: Solar spectroscopy with echelles.
Authors: Pierce, A. Keith; McMath, Robert R.; Mohler, Orren
Bibcode: 1951AJ.....56R.137P
Altcode:
The echelle grating has the advantage of compressing a large spectral
range into a small angle about the blaze direction. A 150 X 75
mm echelle has been installed at the McMath-Hulbert Observatory
in an optical system using 14-foot focal length concave mirrors
for collimator and camera. The observed resolving power at N5000 is
about 250,000 with plate dispersion 2.9 mm/A. The instrumental profile
shows a narrow central peak with a strong satellite line at about .o5A
from the central peak. Photographs of the solar spectrum, prominence
spectra, and of a Zeeman triplet in a sunspot magnetic field have been
made. McMath-Hulbert Observatory, University of Michigan, Pontiac, Mich.
Title: Observations of Solar Limb Darkening Between 0.5 and
10.2&mu
Authors: Pierce, A. K.; McMath, R. R.; Goldberg, Leo; Mohler, O. C.
Bibcode: 1950ApJ...112..289P
Altcode:
Measurements of solar limb darkening are tabulated for thirteen
wave lengths between 0.5 and 10.2 . Observations in the wave-length
region 0.5-2.2 were carried out with the McGregor Tower telescope and
spectrometer for the interval cos 0 = 1.0 to cos 0 = 0.16. Measurements
at three longer wave lengths were made with a Perkin-Elmer spectrometer
attached to the 24inch reflector and covered the interval cos 0 = 1.0
to cos 0 = 0.2. At certain wave lengths the near infrared measurements
agree with those of Abbot's to within 0.1 per cent; at other wave
lengths the systematic differences are as large as 1 per cent. It is
found that the degree of limb darkening decreases in the infrared
from 3.5 to 10.2 . This result is qualitatively consistent with a
systematic increase of the solar continuous opacity toward longer wave
lengths in the infrared, as predicted by theoretical calculations of
the absorption coefficient of the negative hydrogen ion.
Title: New Solar Lines in the Spectral Region 1.97-2.49 μ.
Authors: Goldberg, Leo; Mohler, Orren C.; Pierce, A. Keith; McMath,
Robert R.
Bibcode: 1950ApJ...111..565G
Altcode:
Measurements of wave length and of percentage central absorption are
given for 109 solar lines in the region 1.97-2.49 of the infrared
solar spectrum. The lines were found on tracings obtained with
the high-dispersion spectrometers and Cashman PbS cells of the
McMath-Hulbert Observatory at Lake Angelus and at the Mount Wilson
Observatory. Forty-seven lines have been identified as arising from
neutral atoms of H, Na, Si, Mg, Al, Ca, and Fe. The relative scarcity
of solar lines in the 2.2 IL region is discussed, and a qualitative
explanation is given in terms of the variation with wave length of
the continuous absorption coefficient of H- combined with the solar
temperature gradient.
Title: Photometric atlas of the near infra-red solar spectrum,
[Lambda]8465 to [Lambda] 25,242
Authors: Mohler, Orren
Bibcode: 1950pani.book.....M
Altcode: 1950QB551.M65......
No abstract at ADS
Title: The 3n3 Band of Telluric CO2 in the Solar Spectrum
Authors: Pierce, A. K.; Goldberg, L.; Mohler, O. C.; McMath, R. R.
Bibcode: 1950PhRv...78...74P
Altcode:
No abstract at ADS
Title: N2O Bands in the Solar Spectrum
Authors: Pierce, A. K.; McMath, R. R.; Mohler, O. C.; Goldberg, L.;
Donovan, R. A.
Bibcode: 1950PhRv...78...65P
Altcode:
No abstract at ADS
Title: An Improved Tracing of the Solar Spectrum Between 2. 9 and
3. 6 Microns
Authors: Mohler, Orren; Pierce, A. Keith
Bibcode: 1949PASP...61..221M
Altcode:
No abstract at ADS
Title: Telluric Bands of CH_{4} in the Solar Spectrum.
Authors: McMath, Robert R.; Mohler, Orren C.; Goldberg, Leo
Bibcode: 1949ApJ...109...17M
Altcode:
An all-reflecting telescope and spectrometer have been employed in
conjunction with a Cashman PbS cell to secure a direct-intensity map
of the solar spectrum in the region of 0.8-2.5 ~i with a resolution
of about 50,000. Four molecular-band systems at 1.66, 2.20, 2.32,
and 2.37 ~ have been identified as the P1 + V4~ V3 + P4 and ~2 + P3
transitions of CH4 in the earth's atmosphere. A preliminary analysis
of the wave numbers of the 2P3 rotational components indicates
second-order deviations from theory. The average half-spacing B0 is
found to be 5.163, as compared with the value B0 = 5.252 obtained by
Childs. A comparison of the 2P3 telluric line intensities with those
produced by a measured quantity of methane at room temperature leads
to a calculated methane abundance in the earth's atmosphere of 1.2
parts in a million by mass, and a temperature of -37° C
Title: New Solar Lines in the Spectral Region 1.52-1.75 μ.
Authors: Goldberg, Leo; Mohler, Orren C.; McMath, Robert R.
Bibcode: 1949ApJ...109...28G
Altcode:
Accurate wave lengths and measurements of percentage central absorption
are given for nearly three hundred new solar lines discovered in the
region 1.52-1.75 ~ of the infrared solar spectrum. The lines were found
on high-resolution, direct-intensity tracings of the spectrum obtained
at the McMath- Hulbert Observatory with the McGregor spectrometer
and a Cashman cell. Ninety-three of the lines have been identified as
belonging to neutral atoms of C, Mg, Al, Si, Fe, Mn, and Ni, mainly
on the basis of wave lengths computed from term values. In addition,
the third, seventh, and eighth members of the Brackett series of
hydrogen have been identified, together with the Na I 4s-4p doublet
at XX 22,054 and 22,081. INTRODUCTIO
Title: Note on Methane in the Infra-Red Solar Spectrum
Authors: Pierce, A. K.; McMath, R. R.; Mohler, O. C.; Goldberg, L.
Bibcode: 1949PhRv...76.1533P
Altcode:
No abstract at ADS
Title: Carbon Dioxide in the Infra-Red Solar Spectrum
Authors: Pierce, A. K.; Goldberg, L.; Mohler, O. C.; McMath, R. R.
Bibcode: 1949PhRv...76.1848P
Altcode:
No abstract at ADS
Title: Simultaneous observations of solar flares, surges, and
high-speed dark flocculi
Authors: McMath, R. R.; Mohler, O.
Bibcode: 1948Obs....68..110M
Altcode:
No abstract at ADS
Title: A Solar Infrared Reflecting Spectrometer
Authors: McMath, Robert R.; Mohler, Orren C.
Bibcode: 1948S&T.....7..143M
Altcode:
No abstract at ADS
Title: New Bands in the Telluric Spectrum
Authors: McMath, Robert R.; Mohler, Orren
Bibcode: 1948PASP...60..119M
Altcode:
No abstract at ADS
Title: Resolution of the carbon dioxide bands at 1.6 microns.
Authors: Mohler, Orren C.; Adel, Arthur
Bibcode: 1948AJ.....53..115M
Altcode:
The quantity of CO2 in the earth's atmosphere permits a band development
extending from 15,000A to 200,000A in the solar spectrum. The near
infra-red members (in the neighborhood and short of 20,000A) result
from transitions to highly excited vibrational levels, and are less
intense than the longer wave-length bands. The four bands of CO2
near i6,oooA were first identified in the prismatic solar spectrum
some ten years ago.' The resolution of their rotational structures
has recently been achieved for the first time in the McMath-Hulbert
Observatory's examination of the infra-red solar spectrum with a PbS
cell detector. The customary quadratic expressions have been obtained
and serve to correlate the lines. Departures are of the order' of
hundredths of a wave number, in some instances, a tenth. The precision
of the observations may be expected to sharpen the expression for the
potential energy of the molecule. I.Arthur Adel and C. 0. Lampland,
Ap. J. 87, 202, 1938. McMath-Hulbert Observatory, University of
Michigan, Lake Angelus, Pontiac, Mich.
Title: Recent developments in infra-red solar spectroscopy.
Authors: McMath, R. R.; Mohler, O. C.; Goldberg, L.
Bibcode: 1948AJ.....54Q..44M
Altcode:
Since the late fall of 1947, the ~cGregor tower of the McMath-Hulbert
Observatory has been used for study of the infra-red solar spectrum
beyond the photographic limit. A specially designed, all-mirror optical
system and Pfund-type grating spectrometer, with monochromator,
have been used in conjunction with a Cashman leadsulphide cell to
obtain direct-intensity tracings of the solar spectrum over the
entire region between 8ooo and 25000 A. The spectrum is re corded on
a scale of about five millimeters per angstrom. In the 15000 X region,
lines with separation of 0.3 angstroms are just resolved. Water vapor
absorption almost completely obliterates the spectrum in the regions I
.3-1.5 microns and 1.75-1.95 microns. The intervening portions of the
spectrum, however, are relatively clear and contain a wealth of solar
atomic lines, as well as telluric molecular lines and bands. Progress in
identification has been slow, largely because of the complete absence
of high-resolution laboratory studies in this region of the infra-red
spectrum. Approximately 200 solar atomic lines have been identified
in the infra-red spectrum on the basis of wave lengths computed from
known atomic energy levels. The elements for which lines have been
found include Fe, Si, Na, AIg, Al, C, Ca, as well as the third and
seventh members of the Brackett series of hydrogen. The vast majority
of these lines have excitation potentials higher than five volts. Band
systems of molecules originating in the earth's atmosphere constitute
some of the most interesting features of the infra-red spectrum. Among
these are four CO1 bands in the 1.6 micron region, which have been
resolved for the first time, and three strong bands of CO1 at 2.1
microns. Among the identified molecular bands, those of ammonia and
methane are particularly noteworthy. The evidence for ammonia as
a constituent of the earth's atmosphere is very strong, while the
evidence for methane is conclusive. Mc Math- Hulbert Observatory,
Pontiac, Mich. and University of Michigan Observatory, Ann Arbor, Mich.
Title: The use of a high dispersion spectrograph in the wave-length
region 1.0 to 2.0 microns.
Authors: McMath, Robert R.; Mohler, Orren
Bibcode: 1948AJ.....53R.114M
Altcode:
The recent development of photoconductive cells, sensitive in the near
infra-red, has made possible the observation of the solar spectrum with
a dispersion not previously possible. The McGregor tower telescope of
the McMathHulbert Observatory and the McGregor Littrowtype spectrograph
have been provided with a lead-sulfide, photoconductive cell, and means
for recording the cell output. With this equipment we have produced a
complete map of the infra-red solar spectrum on a scale of 1.6 mm/A,
ending at 2o,6ooA. The wave-length limit of the map is set by the
strong absorption of the telescope objective and the spectrograph
collimator-camera lens. The measured resolving power on tracings
obtained with this equipment is 32,000 at i6,oooA. Observations at
large and small zenith distances from the sun have been made to aid
in separating solar lines from the general background of terrestrial
lines in this region of the solar spectrum. Many atomic lines have been
identified on the first tracings obtained. Mc Math-Hulbert Observatory,
University of Michigan, Lake Angelus, Pontiac, Mich.
Title: A reflecting spectrometer for the solar infra-red.
Authors: McMath, Robert R.; Mohler, Orren C.
Bibcode: 1948AJ.....53R.200M
Altcode:
In order fully to utilize the possibilities of the new photoconductive
infra-red detectors, such as the lead-sulfide cells now constructed
by R. J. Cash man at the Northwestern Technological Institute, a
reflecting optical system must be employed. Experiments during the
past year (1947) at the McMath-Hulbert Observatory have revealed so
many new and important features of the solar infra-red spectrum under
high dispersion, that we have designed and constructed a reflecting
spectrometer for use wi th the McGregor tower telescope. One of the
original telescopes of the McMath-Hulbert Observatory, a ~o-21-inch
Cassegrainian telescope of equivalent focal length 45 feet, and a
calcium fluoride prism monochromator constitute the image-forming and
predispersing system that precede the main spectrograph. Since our
interest is primarily in highly dispersed solar spectra, we have used
an aluminized speculum metal diffraction grating as the dispersing
element. The grating we are now using has been very kindly loaned to
us by the Mount Wilson Observatory. It is ruled with 600 lines per
millimeter and is very bright in the first order infra-red at about
20,OOOA wave length. The chief problem encountered in the design of
any spectrometer is the provision of an absolutely smooth rotation
of the grating about an axis parallel to its rulings. This problem
is comparable to that of producing an errorless drive for a large
telescope, and the long experience of Dr. McMath in the construction
of telescope drives led to the following solution. The grating table
is mounted on a specially selected precision grinder spindle, which
acts as the axis of rotation for the grating. The grating table is
rotated by steel belts attached under tension to a lapped nut that is
driven by a precision ground lead screw. Both the lead screw and the
spindle were obtained through the courtesy of the Ex-Cell-O Corporation
of Detroit, Michigan. They have proved to be entirely satisfactory
under all tests that we have applied. Especial care was necessary to
eliminate vibration set up by the grating drive motor, and to prevent
transmission of minute stresses to the grating table as it rotated. The
drive motor is mounted on a lead pad on the concrete floor of the
McGregor spectrograph, while the grating table is carried on the
isolated pier that supports the grating and collimating lens of the
McGregor Littrow spectrograph. As further precautions, the drive motor
is connected to the first reduction gears by a soft rubber belt, and
the drive shafts connecting the several reducing units are constrained
to transmit only rotation, while remaining free to move over short
distances in a longitudinal direction. No errors are detectable in
the drive when the spectrum is examined visually with a twenty power
microscope. As already mentioned, the grating drive is carried on the
collimator pier of the McGregor Littrow spectrograph. Also on this
pier are the 6-inch aperture, ~77-inch focal length, collimating and
image-forming mirrors. The mirrors and grating drive are attached to
the pier in such a way that only a few minutes are required to place
either the reflecting spectrometer or the refracting McGregor Littrow
system into use. The same entrance slit serves for both instruments. We
have adopted the Pfund optical system because it keeps aberrations at a
minimum, and visual examination of the higher order spectra shows that
the definition of the spectrum lines is very good indeed. The spectrum
is finally focused on a second, exit, slit which selects the narrow
region of the spectrum that falls on the lead- sulfide cell to produce
the photoelectric signal. As the grating is rotated by the drive motor,
the spectrum sweeps slowly across the second slit, and in this way,
scanning of any wave length region can be effected. Variations in
intensity occurring in the spectrum are recorded, after appropriate
amplification of the photoconductive signal, on a Leeds and Northrup
Speedomax Recorder. Two scanning speeds are provided, 0.10 and 0.05
mm/sec. At IO,500A, these linear speeds correspond to o.2~A/sec
and 0.1 2A/sec, since the linear dispersion at this wave length is
2.~~A/mm; but in the region of 22,OOOA the dispersion has increased to
I .87A/n~m with correspondingly slower rate of scan in wave length. The
recording paper is driven at 0.644 mm/sec, or 6.44 times the fastest
(o. 10 mm/sec) scanning speed, hence the resulting dispersions on the
recording paper are 2.65 mm/A at 10,500A and ~3.43 mm/A at 22,OOOA. The
measured resolving power on the recording paper is 22,000 at IO,500A and
44,000 at 22 ,000A. This resolving power is determined entirely by the
slit width, which is 0.20 mm for both entrance and exit slits. There
are almost no laboratory standards for aiding the identification of
atomic lines with wave length longer than 20,OOOA but we have observed
the third member of the Brackett series of hydrogen at 21 ,655.7A,
and the two sodium lines 4S 15 - 4p 2P~~, 22,052.7A (predicted); and
45 25 - 4p 2P~, 22,079.4A (predicted). This pair of lines has been
observed in emission in the laboratory. Measurements of wave lengths
and identifications of solar atomic lines are being made, and we hope
to complete a list of solar lines extending to 25,OOOA. McMath-Hulbert
Observatory, Lake Angelus, Pontiac, Mich.
Title: Photometry of a Solar Flare
Authors: Mohler, Orren C.
Bibcode: 1947PASP...59..266M
Altcode:
No abstract at ADS
Title: High-Dispersion Solar Spectrum in the 10,000 A to 20,000
A Region
Authors: McMath, Robert R.; Mohler, Orren C.
Bibcode: 1947PASP...59..267M
Altcode:
No abstract at ADS
Title: Evidence for coronal absorption on the solar disk.
Authors: McMath, Robert R.; Goldberg, Leo; Mohler, Orren C.
Bibcode: 1947AJ.....52R.156M
Altcode:
A broad, diffuse absorption line at 637A.45 I.A. + 0.01 has been found
in the spectrum of the solar disk on plates obtained with the McGregor
sbectrograph and the 70-ft. tower telescope of the McMath-Hulbert
Observatory. Its width has been estimated at 0.3 to 0.4 A. The line
is seen very faintly at the center of the disk, becoming strongly
accentuated at the limb. It appears equally intense all around the
limb and no significant variations in intensity or in wave length
have been found. The appearance of the line and the closeness of its
position to that of the red coronal line (given by Lyot as X6374.5I +
0.03) suggest the possibility that the absorption line arises from
atoms of Fe x. The evidence for or against the identification as Fe
x is discussed, the results at present being inconclusive. If the
line is due to Fe x, its intensity and distribution around the limb
are such that a considerable abundance of Fe x must be present in the
chromosphere. In this connection attention is called to the observation
by H. D. and H. W. Babcock' of a similar diffuse absorption line
at X6374.40 in the flash spectrum outside of eclipse. The Babcocks
reported that the line was flanked by emission components on either
side. A predicted line of Fe I (ziC2o - e702) occurs at X6374.43. No
other members of this multiplet have been observed with certainty in
the solar spectrum, however, and the width of the observed absorption
line makes its identification as predicted Fe I unlikely, unless it
is closely blended with another faint line. A search has been made
for a similar absorption line at the position of the green coronal
line 5302.86, identified by Edlen as arising from Fe xiv. No such
absorption line has been found. It is pointed out that excitation
conditions in the chromosphere favorable for the presence of Fe
x would not necessarily produce Fe xiv. I.Pub. A. S. P. 46, 132,
1934. McMath-Hulbert Observatory, Lake Angelus, Pontiac, Mich.
Title: The Cook Observatory B Star Spectrographic Survey
Authors: Marshall, Roy K.; Mohler, Orren
Bibcode: 1946PAAS...10R.141M
Altcode:
No abstract at ADS
Title: The space motions of some typical prominences
Authors: Sawyer, H. E.; Mohler, O.; Brodie, J.
Bibcode: 1946PAAS...10..143S
Altcode:
No abstract at ADS
Title: A report on the solar prominence radial velocity program of
the McMath-Hulbert Observatory
Authors: McMath, R. R.; Sawyer, H. E.; Brodie, John; Mohler, Orren
Bibcode: 1946PAAS...10...59M
Altcode:
No abstract at ADS
Title: The measurement of space motions of solar prominences
Authors: McMath, Robert Raynolds; Sawyer, Harold E.; Mohler, Orren C.
Bibcode: 1943POMic...8..123M
Altcode:
No abstract at ADS
Title: A method of measuring radial velocities in solar prominences
Authors: McMath, Robert Raynolds; Sawyer, Harold E.; Mohler, Orren C.;
Brodie, John
Bibcode: 1943POMic...8...57M
Altcode:
No abstract at ADS
Title: Six New BE Stars.
Authors: Mohler, Orren
Bibcode: 1940ApJ....92..315M
Altcode:
No abstract at ADS
Title: An application of coarse gratings and wide-angle lenses to
the determination of spectral classes
Authors: Mohler, Orren
Bibcode: 1939PAAS....9R.129M
Altcode:
No abstract at ADS
Title: A new photoelectric device for stellar photometry
Authors: Mohler, Orren
Bibcode: 1939PAAS....9...14M
Altcode:
No abstract at ADS
Title: Some Changes in the Spectra of the Pleiades.
Authors: Mohler, Orren
Bibcode: 1938ApJ....88..623M
Altcode:
Hydrogen emission is again present in the spectrum of Pleione (HD 23862)
after an absence of 32 years. Sharp metaffic absorption lines are also
now present. Hydrogen emission in Electra appears to have faded
Title: Measures of Effective Wave Length with Wide Angle Lenses
Authors: Mohler, Orren C.
Bibcode: 1938PCooO...3....1M
Altcode:
Plate I: Corner images of 100 mm, Plate II: Grating in position on
telescope, Plate III: Typical grating images, Plate IV: Tracings of
grating spectra
Title: A measurement of the intensity of sunlight in the extreme
ultra-violet
Authors: Mohler, Orren
Bibcode: 1937AJ.....46...33M
Altcode:
No abstract at ADS
Title: The Spectroscopic Orbit of TX Leonis
Authors: Mohler, Orren
Bibcode: 1936PCooO...2....1M
Altcode:
No abstract at ADS
Title: An application of photoelectric Geiger-Muller counters to
the measurement of ultra-violet radiation
Authors: Mohler, Orren
Bibcode: 1936PAAS....8..250M
Altcode:
No abstract at ADS
Title: A spectroscopic orbit for 49 Leonis
Authors: Mohler, Orren
Bibcode: 1936AJ.....45...40M
Altcode:
No abstract at ADS
Title: The Spectrum of a Nova
Authors: Mohler, Orren
Bibcode: 1935PCooO...1....1M
Altcode:
Figure I: Spectra of Nova Herculis 1934, Figure 2: Microdensitometer
tracings of Hγ line in spectra of Nova Herculis 1934
Title: An account of the Roslyn House Observatory
Authors: Mohler, Orren
Bibcode: 1935PA.....43..199M
Altcode:
No abstract at ADS
Title: A determination of the temperatures of Be stars
Authors: Mohler, Orren C.
Bibcode: 1934POMic...5...43M
Altcode:
No abstract at ADS
Title: The radial velocity of the eclipsing variable 49 Leonis
Authors: Mohler, Orren
Bibcode: 1933PAAS....7R.224M
Altcode:
No abstract at ADS
Title: A Determination of the Temperatures of BE Stars.
Authors: Mohler, Orren
Bibcode: 1933PhDT.........1M
Altcode:
No abstract at ADS
Title: A note on helium lines in three Be spectra
Authors: Mohler, Orren; Dodson, Helen W.
Bibcode: 1933PAAS....7..182M
Altcode:
No abstract at ADS
Title: A determination of the temperatures of Be stars.
Authors: Mohler, Orren
Bibcode: 1933dtbs.book.....M
Altcode: 1933QB4.M6v5n5.....
No abstract at ADS
Title: A determination of the temperatures of the Be stars
Authors: Mohler, Orren
Bibcode: 1933PAAS....7Q.224M
Altcode:
No abstract at ADS
Title: A determination of the temperatures of Be stars
Authors: Mohler, Orren Cuthbert
Bibcode: 1933PhDT.........8M
Altcode:
No abstract at ADS