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NASA NTRS2022

Study of the Mass-loss Rate from the Sun

We investigate the temporal evolution of the yearly total mass-loss rate (YTMLR) from the Sun through coronal mass ejections (CMEs) over solar cycles 23 and 24. The mass determination of CMEs can be subject to significant uncertainty. To minimize this problem, we have used extensive statistical analysis. For this purpose, we employed data included in the Coordinated Data Analysis Workshop (CDAW) catalog. We estimated the contributions to mass loss from the Sun from different subsamples of CMEs (selected on the basis of their masses, angular widths, and position angles). The temporal variations of the YTMLR were compared to those of the sunspot number (SSN), X-ray flare flux, and the Disturbance Storm Time (Dst) index. We show that the CME mass included in the CDAW catalog reflects with high accuracy the actual mass-loss rate from the Sun through CMEs. Additionally, it is shown that the CME mass distribution in the log-lin representation reflects the Gaussian distribution very well. This means that the CMEs included in the CDAW catalog form one coherent population of ejections that have been correctly identified. Unlike the CME occurrence rate, it turns out that the YTMLR is a very good indicator of solar activity (e.g., SSN) and space weather (e.g., Dst index) consequences. These results are very important, since the YTMLR, unlike the mass loss through solar wind, significantly depends on solar cycles.

the sun↗

NASA NTRS2014

Obtaining Stokes Parameters from the SUMI Experiment

A sounding rocket experiment designed at the Marshall Space Flight Center, named the Solar Ultraviolet Magnetograph Investigation, had its second launch in July of 2012 to test the feasibility of measuring polarization signals of the ionized magnesium resonance doublet near 280 nm, originating from the transition region. The rocket housed a telescope at the front end and an imaging system at the rear end. Placed at the focal point of the self‐filtering telescope, a wave plate rotated through 12 predefined angular orientations to restrict the measurements to specific combinations of circular and linear polarization. Coupled with a double Wollaston analyzer, the linearly polarized ordinary and extraordinary beams were measured for the 12 combinations, each containing different fractions of the Stokes parameters (I, Q, U, V). A thorough analysis of the data has allowed us to come to several conclusions regarding the design of the experiment. 1) We are confident that polarization can be measured. A sunspot region was determined to exhibit similar results over multiple pixels. 2) Measurements are limited by resolution, i.e. regions smaller than the angular resolution per pixel cannot be resolved with any certainty. 3) Temporal evolution of magnetic features must be considered in future experimental designs. Measurements need to be taken in repeated cycles as opposed to a single cycle over the duration of the experiment. In our presentation, we will provide a summary of the observations along with the methods of our analysis, including the limitations that we've encountered.

Fayock, Brian↗

NASA NTRS1995

Hot spots and active longitudes: Organization of solar activity as a probe of the interior

In order to investigate how solar activity is organized in longitude, major solar flares, large sunspot groups, and large scale photospheric magnetic field strengths were analyzed. The results of these analyses are reported. The following results are discussed: hot spots, initially recognized as areas of high concentration of major flares, are the preferred locations for the emergence of big sunspot groups; double hot spots appear in pairs that rotate at the same rate separated by about 180 deg in longitude, whereas, single hot spots have no such companions; the northern and southern hemispheres behave differently in organizing solar activity in longitude; the lifetime of hot spots range from one to several solar cycles; a hot spot is not always active throughout its lifetime, but goes through dormant periods; and hot spots with different rotational periods coexist in the same hemisphere during the same solar cycle.

Bai, Taeil↗

NASA NTRS1989

Rotation of the photospheric magnetic fields: A north-south asymmetry

During most of solar cycle 21 the large-scale photospheric field rotated more rapidly in the Northern Hemisphere than in the southern. The large-scale northern field rotated with a 26.9 day period (synodic), was centered at 15 degress N, and covered a latitude zone about 24 degrees wide. The large-scale southern field rotated with a periodicity of 28.1 days, was centered at 26 degrees S, and covered a latitude zone about 32 degrees wide. Our analysis showed rotational power at only a few discrete latitudes and frequencies in each hemisphere. The center of each peak lies near the sunspot differential rotation curve. The largest scale field contributes to the configuration of the coronal and interplanetary magnetic field (IMF). The strength of the first harmonic of the northern field suggests that this structure may be related to the 4-sector pattern observed in the IMF polarity. The southern field had much lower power at the first harmonic of the solar rotation rate and so would contribute only to a 2-sector structure in the IMF. These results were discovered in Fourier analysis of photospheric synoptic charts obtained at the Wilcox Solar Observatory from 1976 to 1986 and confirmed in higher resolution maps from the National Solar Observatory. Mt. Wilson magnetic field measurements from solar cycle 20 show a similar north-south asymmetry.

Antonucci, E.↗

NASA NTRS1990

Rotation of the photospheric magnetic fields - A north-south asymmetry

During most of solar cycle 21 the large-scale photospheric field rotated more rapidly in the Northern Hemisphere than in the southern. The large-scale northern field rotated with a 26.9 day period (synodic), was centered at 15 degrees N, and covered a latitude zone about 24 degrees wide. The large-scale southern field rotated with a periodicity of 28.1 days, was centered at 26 degrees S, and covered a latitude zone about 32 degrees wide. Our analysis showed rotational power at only a few discrete latitudes and frequencies in each hemisphere. The center of each peak lies near to the sunspot differential rotation curve. The largest scale field contributes to the configuration of the coronal and interplanetary magnetic field (IMF). The strength of the first harmonic of the northern field suggests that this structure may be related to the 4-sector pattern observed in the IMF polarity. The southern field had much lower power at the first harmonic of the solar rotation rate and so would contribute only to a 2-sector structure in the IMF. These results were discovered in Fourier analysis of photospheric synoptic charts obtained at the Wilcox Solar Observatory from 1976 to 1986 and confirmed in higher resolution maps from the National Solar Observatory. Mt. Wilson magnetic field measurements from solar cycle 20 show a similar north-south asymmetry.

Antonucci, E.↗

NASA NTRS1988

Frequencies of low-degree solar acoustic oscillations and the phase of the solar cycle

A study of the solar total irradiance data of the Active Cavity Radiometer Irradiance Monitor on the SMM satellite shows a small but formally significant shift in the frequencies of solar acoustic (p-mode) oscillations between the epochs of maximum and minimum solar activity. Specifically, the mean frequency of the strongest p-mode resonances of low spherical-harmonic degree (l = 0-2) is approximately 1.3 parts in 10,000 higher in 1980, near the time of sunspot maximum, than at around 1985, near sunspot minimum. The observed frequency shift may be an 11-yr effect but the precise mechanism is not clear.

Woodard, Martin F.↗

NASA NTRS1978

Meteoritic evidence for the Maunder minimum in solar activity

Concentrations of argon-39 produced by cosmic rays in the metal in 30 meteorites are remarkably similar, but they are slightly higher than expected for the present solar-cycle-averaged flux of cosmic rays. This supports the idea suggested by Eddy (1976) that there were prolonged minima in solar activity before 1715 which caused the deVries maximum in carbon-14 in earth's atmosphere by reducing the amount of cosmic-ray modulation in interplanetary space. The observations are easily consistent with 180 years of 'sunspot minimum' modulation during the Maunder and Spoerer minima, and possibly with virtually no solar modulation at all during that time. This would indicate that the solar wind then contained very little magnetic turbulence or whatever it is in the solar wind that causes the modulation of galactic cosmic rays.

Forman, M. A.↗

NASA NTRS1988

Distribution of flares on the sun during 1955-1985 - 'Hot spots' (active zones) lasting for 30 years

The coordinates of 'major solar flares' observed during the period from January 1955 through August 1985 are analyzed. About 100 'superactive' regions (large, complex, active regions containing large sunspots) produced 46 percent of the major flares during the period. Superactive regions appeared more frequently in certain areas of the sun called 'hot spots' or 'active zones'. The synodic rotation periods of the northern and southern hemisphere hot spots were 26.72 d and 26.61 d, respectively. One of the two hot spots persisted through three solar cycles, and the other was active during cycles 19 and 21 but was dormant during cycle 20. These findings suggest that the mechanism producing hot spots must be stable for two or three solar cycles or longer.

Bai, Taeil↗

NASA NTRS1987

Ground-based photometric measurements

Resolution in space, time, magnetic field strength, intensity variance, and wavelength all are used to isolate the signals from sunspots, plage, network, and nonmagnetic areas. Ground data has demonstrated the dominance of sunspots in causing irradiance variance on time scales of hours to months, the near balance of spot deficit and facular excess emission, and the low level of irradiance variation caused by nonmagnetic regions. Present techniques limit the accuracy of comparison with direct irradiance measures, and improvements should be made. Goals for ground-based photometry for the next cycle are suggested.

Labonte, Barry J.↗

NASA NTRS2007

Variability of Solar Irradiances Using Wavelet Analysis

We have used wavelets to analyze the sunspot number, F10.7 (the solar irradiance at a wavelength of approx.10.7 cm), and Ap (a geomagnetic activity index). Three different wavelets are compared, showing how each selects either temporal or scale resolution. Our goal is an envelope of solar activity that better bounds the large amplitude fluctuations form solar minimum to maximum. We show how the 11-year cycle does not disappear at solar minimum, that minimum is only the other part of the solar cycle. Power in the fluctuations of solar-activity-related indices may peak during solar maximum but the solar cycle itself is always present. The Ap index has a peak after solar maximum that appears to be better correlated with the current solar cycle than with the following cycle.

Pesnell, William D.↗

NASA NTRS1990

Distant solar wind plasma - View from the Pioneers

Temporal variation and spatial gradients over nearly 50 AU in heliocentric distance and about 17 deg of latitude are investigated on the basis of observations from Pioneer 10-11, Voyager 2, IMP 8, and the Pioneer Venus Orbiter. The average solar wind velocity was found to vary somewhat over the solar cycle, but at any given epoch the average velocity is essentially independent of heliocentric distance. No indication of a terminal shock or signature of interaction with the interstellar medium was found. The stream structure commonly observed in the inner heliosphere diminishes with increasing heliocentric distance, reflecting the processing of material in the stream-stream heliosphere, both at times of high sunspot activity and disturbed solar conditions, and near the solar minimum when the interplanetary current sheet is flattened.

Barnes, Aaron↗

NASA NTRS2001

A Time-Frequency Analysis of the Effects of Solar Activities on Tropospheric Thermodynamics

Whether the Sun has significantly influenced the climate during the last century has been under extensive debates for almost two decades. Since the solar irradiance varies very little in a solar cycle, it is puzzling that some geophysical parameters show proportionally large variations which appear to be responding to the solar cycles. For example, variation in low altitude clouds is shown correlated with solar cycle, and the onset of Forbush decrease is shown correlated with the reduction of the vorticity area index. A possible sun-climate connection is that galactic cosmic rays modulated by solar activities influence cloud formation. In this paper, we apply wavelet transform to satellite and surface data to examine this hypothesis. Data analyzed include the time series for solar irradiance, sunspots, UV index, temperature, cloud coverage, and neutron counter measurements. The interactions among the elements in the Earth System under the external and internal forcings give out very complex signals.The periodicity of the forcings or signals could range widely. Since wavelet transforms can analyze multi-scale phenomena that are both localized in frequency and time, it is a very useful technique for detecting, understanding and monitoring climate changes.

Kiang, Richard K.↗

NASA NTRS1984

Interplanetary radio storms. I - Extension of solar active regions through the interplanetary medium

About 100 storms of type-III solar radio bursts have been identified in the ISEE-3 radio-experiment data during the 4-yr period around the maximum of the 21st solar cycle. They demonstrate the very frequent presence of streams of suprathermal electrons. Their durations range from 1 to 10 d or more. They are observed up to 100-170 solar radii. Their rate of occurrence is 2 to 3 per solar rotation near solar maximum. It is shown that the time variations of the daily radio-emission intensities correlate with the sunspot-number variations and with the solar activity in general. More specifically, a very good correlation is found with the meter-wave type-III and type-I storms, which demonstrates that the suprathermal electrons responsible for the radio emission have been accelerated below 2 solar radii heliocentric. The different lags observed between the sunspot-number variations, the S-component, and the type-I and type-III storms are discussed.

Bougeret, J.-L.↗

NASA NTRS1993

Hotspots and sunspots - Surface tracers of deep mantle convection in the earth and sun

The evolution of the hot-spot distribution on earth in time and space is investigated using available age data. The statistics of continental flood basalt eruptions suggests the formation of a total of about 40 hot spots worldwide during the Cenozoic and Mesozoic, with no true antipodal pairs found. It was found that hot spots tend to concentrate mainly in mid-latitudes, but the pattern of new appearances of hot spots may migrate from high to low latitudes in both hemispheres in long cycles, and may also drift in longitude, although much more slowly prograde.

Stothers, Richard B.↗

NASA NTRS1975

H alpha oscillations in sunspot umbrae

Results are reported for direct measurement of intensity fluctuations and photographic subtractions of simultaneous Doppler filtergrams of H-alpha oscillations in sunspot umbrae. The observational techniques are described, and data are presented on the intensity variations, power spectra, and specific characteristics of the oscillations. Periods for the velocity oscillations are obtained by power spectrum analysis. It is found that the oscillations are apparently continuous, and that each umbra has its own characteristic period ranging from 145 to 180 plus or minus 10 sec and a duration of at least 8 cycles. A Doppler shift of 10 km/sec, an oscillating element size of 3 sec or less, and visibility to a radius vector of about 0.9 are also observed.

Phillis, G. L.↗

NASA NTRS1988

Solar cycle dependence of the radial gradient of cosmic ray intensity

Observation of the interplanetary intensity of cosmic rays (Ep greater than 80 MeV) by Pioneers 10 and 11 now spans a 16-year time period 1972-1988 and heliocentric radial distances, out to 43.7 AU for Pioneer 10 and 25.8 AU for Pioneer 11. Solar modulation continues to be present at the current distances of both spacecraft. The radial gradient of intensity is measured continuously over the slowly varying, outward moving radial segment r10-r11. The 50-day mean values of the gradient G vary systematically and cyclically in phase with solar activity as measured by sunspot number, with a maximum value of about 2.1 percent/AU at sunspot maximum and a minimum value of about 1.2 percent/AU at sunspot minimum.

Van Allen, James A.↗

NASA NTRS1984

Observations of the reappearance of polar coronal holes and the reversal of the polar magnetic field

Observational data relating to the evolution of the polar magnetic field around sunspot maximum is examined. Particular emphasis is given to coronal hole observations performed during the last two solar maxima. Long-term averages of the latitudinal dependence of the photospheric magnetic field and the evolutionary pattern of the polar crown filaments are used to trace the poleward motion of the reversal of the large-scale field and are compared to the redevelopment of polar holes. Within the context of phenomenological models of the solar cycle, it is concluded that: (1) the process of polarity reversal and redevelopment of polar holes is discontinuous, with surges of flux of old-cycle polarity interrupting the poleward migration of new-cycle flux; (2) contrary to the Babcock (1961) hypothesis, the polar crown disappears months after the magnetic pole reversal; and (3) the observations support suggestions of a poleward meridional flow around solar maximum that cannot be accounted for by Leighton-type (1964) diffusion.

Webb, D. F.↗

NASA NTRS1983

The great solar anomaly ca. 1780-1800 - An error in compiling the record

The view that the sunspot index time sequence is of lessened validity prior to about 1850 is shown to be consistent with an error in the 1780-1800 time period when phase, offset of the Hale carrier sinusoid from zero mean, and the amplitude modulation envelope all show a lack of conformity with respect to the remainder of the record subsequent to the Maunder minimum. This lack of conformity is consistent with an error that delays one or more of the 11-year cycle minima but recovers phase subsequently. This type of error creates a strongly coherent set of companion changes in offset of the carrier from zero mean and in the amplitude modulation envelope.

Sonett, C. P.↗