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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
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NASA NTRS1980

Solar activity prediction of sunspot numbers (verification). Predicted solar radio flux; predicted geomagnetic indices Ap and Kp

Efforts to further verify a previously reported technique for predicting monthly sunspot numbers over a period of years (1979 to 1989) involved the application of the technique over the period for the maximum epoch of solar cycle 19. Results obtained are presented. Methods and results for predicting solar flux (F10.7 cm) based on flux/sunspot number models, ascent and descent, and geomagnetic activity indices as a function of sunspot number and solar cycle phase classes are included.

Newman, S. R.↗
NASA NTRS1981

Additional measurements of the high-latitude sunspot rotation rate /Research note/

Sunspot rotation rate measurements at high sunspot latitudes are reported for the period 1966-68, based on ten spots at latitudes greater than about 28 deg from H-alpha patrol records for this period. A sidereal rotation rate of 13.70 + or - 0.07 deg/day was found on the average, at 31.05 + or - 0.01 deg. Taken together, the full set of measurements in this latitude regime yield a rotation rate that is in excellent agreement with the result derived by Newton and Nunn (1951) from recurrent spots at lower latitudes throughout the six cycles from 1878 to 1944.

Landman, D. A.↗
NASA NTRS1982

Sunspot variation and selected associated phenomena: A look at solar cycle 21 and beyond

Solar sunspot cycles 8 through 21 are reviewed. Mean time intervals are calculated for maximum to maximum, minimum to minimum, minimum to maximum, and maximum to minimum phases for cycles 8 through 20 and 8 through 21. Simple cosine functions with a period of 132 years are compared to, and found to be representative of, the variation of smoothed sunspot numbers at solar maximum and minimum. A comparison of cycles 20 and 21 is given, leading to a projection for activity levels during the Spacelab 2 era (tentatively, November 1984). A prediction is made for cycle 22. Major flares are observed to peak several months subsequent to the solar maximum during cycle 21 and to be at minimum level several months after the solar minimum. Additional remarks are given for flares, gradual rise and fall radio events and 2800 MHz radio emission. Certain solar activity parameters, especially as they relate to the near term Spacelab 2 time frame are estimated.

Wilson, R. M.↗
NASA NTRS1981

Development of a diode laser heterodyne spectrometer and observations of silicon monoxide in sunspots

A state of the art, tunable diode laser infrared heterodyne spectrometer was designed and constructed for ground based observations throughout the 8 to 12 micron atmospheric window. The instrument was optimized for use with presently available tunable diode lasers, and was designed as a flexible field system for use with large reflecting telescopes. The instrument was aligned and calibrated using laboratory and astronomical sources. Observations of SiO fundamental (v = 1-0) and hot band (v = 2-1) absorption features were made in sunspots near 8 microns using the spectrometer. The data permit an unambiguous determination of the temperature pressure relation in the upper layers of the umbral atmosphere, and support the sunspot model suggested by Stellmacher and Wiehr.

Glenar, D. A.↗
NASA NTRS1982

A model of a sunspot chromosphere based on OSO 8 observations

OSO 8 spectrometer observations of the H I, Mg II, and Ca II resonance lines of a large quiet sunspot during November 16-17, 1975, along with a C IV line of that event obtained by a ground-based spectrometer, are analyzed together with near-simultaneous ground-based Stokes measurements to yield an umbral chromosphere and transition region model. Features of this model include a chromosphere that is effectively thin in the resonance lines of H I and Mg II, while being saturated in Ca II, and an upper chromospheric structure similar to that of quiet-sun models. The similarity of the upper chromosphere of the sunspot umbra to the quiet-sun chromosphere suggests that the intense magnetic field plays only a passive role in the chromospheric heating mechanism, and the observations cited indicate that solar-type stars with large areas of ordered magnetic flux would not necessarily exhibit extremely active chromosphere.

Lites, B. W.↗
NASA NTRS1982

On the disappearance of a small sunspot group

The small sunspot group associated with Hale active region 17694 was observed jointly by the Mount Wilson and the Big Bear Solar Observatories, through the time of sunspot disappearance. The magnetic flux from the region was seen to decrease by about 10% per day during the observing interval. This was accompanied by fragmentation of the dominant spot as a supergranule network formed. No evidence for spreading or diffusion of the active region field was found.

Wallenhorst, S. G.↗
NASA NTRS1981

The sunspot chromosphere-corona transition region

Data from simultaneous readings of the line intensities, Doppler shifts, and line widths of a sunspot ion emission lines between 1170-1700 A are reported. Subsonic and supersonic flows were observed in the same line of sight above the umbra. A reduction of coronal plasma over sunspots with an electron temperature exceeding 1,000,000 K was confirmed, concurrent with enhanced emission from the transition region plasma in the temperature range 200,000-1,000,000 K. The differential emission measure is noted to have been caused to shift because of the enhancement of the transition region plasma emission, where radiative losses dominated the energy balance. Calculations of the energy balance also indicated that a detected divergence in the enthalpy flux for the umbral downflows could balance the radiative losses in the electron temperature range 30,000-200,000 K.

Nicolas, K. R.↗
NASA NTRS1981

Observations of dynamical phenomena in sunspots

A preliminary report of the results of one observing run based on data from one spectral line, the photospheric magnetic line Fe 6303, is presented as part of a series of observations of dynamical phenomena in sunspots using photographic spectra with the SPO vacuum tower telescope and echelle spectrograph. The ejection of a magnetic feature from the outer edge of the penumbra was observed. The initial total field strength of the feature was about 1000 gauss, which appeared to decrease as the feature moved away from the sunspot. The proper motion was about 2 km/s, and the velocity field measured in the V profile showed a downflow of 400 m/s on the spotward side of the moving magnetic feature. Umbral oscillations at the photospheric level with a herringbone structure characteristic of horizontally propagating waves, suggesting some overtone mode of membrane oscillation in the umbra, were seen. The peak amplitude of the oscillation was about 200 m/s, and the mean power spectrum had several clear peaks.

Nye, A. H.↗
NASA NTRS1981

UVSP/SMM observations of transition region oscillations in sunspots

Using Ultraviolet Spectrometer and Polarimeter data obtained in emission lines formed at temperatures of 70,000 K to 130,000 K, transition region oscillations in sunspots have been observed. The frequency of these oscillations lies in the range 5.8 mHz to 7.8 mHz. Their regular appearance in line-of-sight velocity and their frequent occurrence in intensity in phase with maximum blue shift leads to the interpretation of the oscillations as upward-propagating acoustic waves. The presence in two of the C IV wavelength 1548.19 time series of a phase-shifted oscillation in the line width may be caused by the presence of unidentified blends in the line wings. The energy flux carried by the umbral acoustic waves is less than 2000 erg/sq cm/s, some seven orders of magnitude smaller than the missing radiative flux of sunspots.

Gurman, J. B.↗
NASA NTRS1981

Sunspots and solar variability

The analyses of Willson et al. (1981) and Hudson et al. (1981) are extended in correlating the total solar irradiance monitor (ACRIM) data with the routine synoptic sunspot data. At the simplest level, this correlation reveals clearly that the so-called 'missing flux' is truly missing in the sense that large young active regions do produce at net diminution of the irradiance when their spots cross the central meridian. It is pointed out that the irradiance deficit must of course be made up, either promptly or on intermediate time scales; this is because the surface effects cannot perturb the energy generation processes in the interior. In the approach taken here, simple models of the reemission are constructed, the total reemission is scaled to the estimated sunspot deficit, and an attempt is made to measure the parameters of the models by a statistical comparison with ACRIM data.

Hudson, H. S.↗
NASA NTRS1982

Observations of the longitudinal magnetic field in the transition region and photosphere of a sunspot

The Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission spacraft has observed for the first time the longitudinal component of the magnetic field by means of the Zeeman effect in the transition region above a sunspot. The data presented here were obtained on three days in one sunspot, have spatial resolutions of 10 arcsec and 3 arcsec, and yield maximum field strengths greater than 1000 G above the umbrae in the spot. The method of analysis, including a line-width calibration feature used during some of the observations, is described in some detail in an appendix; the line width is required for the determination of the longitudinal magnetic field from the observed circular polarization. The transition region data for one day are compared with photospheric magnetograms from the Marshall Space Flight Center. Vertical gradients of the magnetic field are compared from the two sets of data; the maximum gradients of 0.41 to 0.62 G/km occur above the umbra and agree with or are smaller than values observed previously in the photosphere and low chromosphere.

Henze, W., Jr.↗
NASA NTRS1982

Sunspot time series - Spectrum from square law modulation of the Hale cycle

The spectrum of the sunspot index can be qualitatively accounted for by a very simple time series model which the Hale 22 year cycle dominates; the series is amplitude modulated at the 90 year Gleissberg period with an index of 25%. The square of the modulated Hale cycle reproduces all of the spectral lines of the Zurich sunspot index spectrum, provided that a small offset is included in the Hale carrier. Without this, evidence of the 22 year periodicity disappears. The squaring explains the dominance of the 11 year cycle which is an artifact of the modulation as is the 45 year line. The offset suggests a small relict magnetic field in the sun's core. Lastly Gilliland (1981) finds a radial eigenmode in the sun with period of 76 + or - 8 years suggestive of a physical basis for the Gleissberg modulation.

Sonett, C. P.↗
NASA NTRS1983

Vertical gradients of sunspot magnetic fields

The results of a Solar Maximum Mission (SMM) guest investigation to determine the vertical gradients of sunspot magnetic fields for the first time from coordinated observations of photospheric and transition-region fields are described. Descriptions are given of both the photospheric vector field of a sunspot, derived from observations using the NASA Marshall Space Flight Center vector magnetograph, and of the line-of-sight component in the transition region, obtained from the SMM Ultraviolet Spectrometer and Polarimeter instrument. On the basis of these data, vertical gradients of the line-of-sight magnetic field component are calculated using three methods. It is found that the vertical gradient of Bz is lower than values from previous studies and that the transition-region field occurs at a height of approximately 4000-6000 km above the photosphere.

Hagyard, M. J.↗
NASA NTRS1983

Is the sunspot spectrum really so complicated?

The spectrum of the sunspot index can be qualitatively accounted for by a very simple model which the Hale 22-yr cycle dominates. The Hale cycle is amplitude modulated at the 90-yr Gleissberg period with an index of 25 percent. The square of the modulated Hale cycle reproduces all of the spectral lines of the Zurich-sunspot-index spectrum, between 90- and 8.9-yr periods, provided that a small offset is included in the Hale carrier. Without this, evidence of the 22-yr periodicity disappears because of the squaring, thus explaining the very strong 11-yr cycle which is an artifact of the modulation, as is the 45-yr line. The offset suggests a small relict magnetic field in the sun's core.

Sonett, C. P.↗
NASA NTRS1983

X-ray bright points and the sunspot cycle - Further results and predictions

X-ray images obtained during two rocket flights near the maximum of sunspot cycle 21 now allow the study of the variation of X-ray bright point number over an eleven-year period covering the maxima of the last two cycles. The new data are consistent with the earlier conclusion that the temporal variation of bright point and sunspot number are out of phase. The quantities are related through a power law with a negative exponent of 2/3.

Davis, J. M.↗
NASA NTRS1983

Sunspot index infers a small relict magnetic field in the sun's core

Inferences from the asymmetry in time of the solar sunspot number, taken over many cycles, yields evidence for the relict magnetic field in the solar core which Cowling (1945) suggested would not decay, over the solar system's lifetime, given sufficiently high bulk electrical conductivity. Whether such a relict field is present can be ascertained either by searching for the presence of a 22-year line quintet in the Fourier spectrum of the sunspot index or by processing the time sequence in order to highlight an offset. Since the solar cycle is unstable to frequency drifts, the presence of frequency modulation can lead to a spurious relict field signal.

Sonett, C. P.↗
NASA NTRS1984

Dynamical phenomena in sunspots. I - Observing procedures and oscillatory phenomena. II - A moving magnetic feature

High resolution spectra consisting of at least 1 hr periods were obtained of the sunpost atmosphere. The Ca II H and K lines were scanned to characterize umbral oscillations and flashes. The former displayed peaks lasting 150-197 sec, while penumbral oscillations peaked in the 197-300 sec range. Quiet sun oscillations exhibited no peaks under 300 sec. The Ca II K line umbral flashes were ubiquitous for all observational periods and were associated with light bridges in the umbra. Magnetic field, vertical velocity, and chromospheric intensity measurements taken during the 1 hr scans covered moving magnetic features (MMF), which traversed the moats around sunspots. MMF areas increased while the magnetic field intensity decreased with MMF movement away from a sunspot. Bright Ca II K line wings were apparent in the MMFs, but cores of the lines were not observed, suggesting that flux loops generating the line are low in the photosphere.

Thomas, J. H.↗
NASA NTRS1984

Solar total irradiance and sunspot area in 1981

Precise observations of the total solar irradiance in 1980 from the solar-maximum mission, showed a strong correlation with the projected total sunspot area. This correlation explained about half of the variance (r of about 0.75) in the total-irradiance data, leaving the other half for other solar phenomena and errors in the data. The analysis of the intervening three years of spin-mode data, which have reduced coverage, has begun. It is found that the correlation persists at about the same qualitative level, but with increased scatter that can be attributed to the smaller amount of data. The flatness of the distribution of areas of sunspot groups makes it possible to estimate PSI approximately from only the large groups.

Hudson, H. S.↗