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Hudson, H.

Publications and source records attributed to Hudson, H..

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Destruction of Sun-Grazing Comet C-2011 N3 (SOHO) Within the Low Solar Corona

Observations of comets in Sun-grazing orbits that survive solar insolation long enough to penetrate into the Suns inner corona provide information on the solar atmosphere and magnetic field as well as on the makeup of the comet. On 6 July 2011, the Solar Dynamics Observatory (SDO) observed the demise of comet C2011 N3 (SOHO) within the low solar corona in five wavelength bands in the extreme ultraviolet (EUV). The comet penetrated to within 0.146 solarradius (100,000 kilometers) of the solar surface before its EUV signal disappeared.

ultraviolet emissions↗
NASA NTRS2000

Onset of the Magnetic Explosion in Solar Flares and Coronal Mass Ejections

We present observations of the magnetic field configuration and its transformation in six solar eruptive events that show good agreement with the Hirayama-Shibata model for eruptive flares. The observations arc X-ray images from the Yohkoh Soft X-ray Telescope (SXT) and magnetograms from Kitt Peak National Solar Observatory, interpreted together with the 1-8 Angstrom X-ray flux observed by GOES. The observations show: 1. Each event is a magnetic explosion that occurs in an initially closed magnetic bipole in which the core field is sheared and twisted in the shape of a sigmoid, having an oppositely curved elbow on each end. The arms of the opposite elbows are sheared past each other so that they overlap and are crossed low above the neutral line in the middle of the bipole. 2. Although four of the explosions arc ejective (blow open the bipole) and two are confined (arc arrested within the closed bipole), all six begin the same way. In the SXT iniages, the explosion begins with brightening and expansion of the two elbows together with the appearance of short bright sheared loops low over the neutral line under the crossed arms and, rising up from the crossed arms, long strands connecting the far ends of the elbows. 3. All six events arc single-bipole events in that during the onset and early development of the explosion they show no evidence for reconnection between the exploding bipole and any surrounding magnetic fields. We conclude that in each of our events the magnetic explosion was unleashed by runaway tether-cutting via implosive/explosive rcconnection in the middle of the sigmoid, as in the Hirayama-Shibata model. The similarity of the onsets of the two confined explosions to the onsets of the four ejective explosions and their agreement with the model indicate that runaway reconnection inside a sheared core field can begin whether or not the overlying fields (the envelope field and contiguous fields that press down on the envelope) allow the explosion to be ejective. We consider the implications ofthis for the unleashing of magnetic explosions in field configurations composed of to or more impacted bipoles.

Moore, R. L.↗
NASA NTRS1995

Comparison of Yohkoh x-ray coronal events with Ulysses interplanetary events

The Yohkoh soft X-ray telescope (SXT) has observed several largescale eruptive events per year for the first three years of observations (Aug. 1991 - Nov. 1994) Such events are most prominent at high latitudes, but resemble long-duration flare events seen in active regions. Some of the high-latitude events have now been identified in the Ulysses/SWICS data base during the Ulysses south polar passage. There are puzzling examples of solar events with no interplanetary counterparts. A comparison of coronal and interplanetary events can lead to better models for mapping interplanetary disturbances back to their source location, especially by combining Yohkoh morphology with three-dimensional representations of the coronal magnetic field. In this paper we describe the parameters of the hot plasma seen by SXT. There is clear evidence for non radial motion in specific events. We present comparisons between the ionization temperature of the interplanetary plasma with that observed at the Sun in cases where this is possible.

Lemen, J. R.↗
NASA NTRS1994

A gigantic coronal jet ejected from a compact active region in a coronal hole

A gigantic coronal jet greater than 3 x 10(exp 5) km long (nearly half the solar radius) has been found with the soft X-ray telescope (SXT) on board the solar X-ray satellite, Yohkoh. The jet was ejected on 1992 January 11 from an 'anemone-type' active region (AR) appearing in a coronal hole and is one of the largest coronal X-ray jets observed so far by SXT. This gigantic jet is the best observed example of many other smaller X-ray jets, because the spatial structures of both the jet and the AR located at its base are more easily resolved. The range of apparent translational velocities of the bulk of the jet was between 90 and 240 km s(exp -1), with the corresponding kinetic energy estimated to be of order of 10(exp 28) ergs. A detailed analysis reveals that the jet was associated with a loop brightening (a small flare) that occurred in the active region. Several features of this observation suggest and are consistent with a magnetic reconnection mechanism for the production of such a 'jet-loop-brightening' event.

Shibata, K.↗
NASA NTRS1984

The inconstant solar constant

The Active Cavity Radiometer Irradiance Monitor (ACRIM) of the Solar Maximum Mission satellite measures the radiant power emitted by the sun in the direction of the earth and has worked flawlessly since 1980. The main motivation for ACRIM's use to measure the solar constant is the determination of the extent to which this quantity's variations affect earth weather and climate. Data from the solar minimum of 1986-1987 is eagerly anticipated, with a view to the possible presence of a solar cycle variation in addition to that caused directly by sunspots.

Willson, R. C.↗
NASA NTRS1983

Studies with the Pinhole/Occulter Facility

The scientific justifications for high-resolution hard X-ray astronomy are reviewed, and a scheme for making such observations from the Space Shuttle payload bay is presented. High-resolution X-ray observations at photon energies above 10 keV are important for the understanding of the physics of solar flares, coronal disturbances related to flares, and corona fine structure, as well as nonsolar X-ray sources. In order to study these phenomena, concepts have been developed for the Shuttle Pinhole/Occulter Facility (P/OF), an instrument based on the principles of the pinhole camera which will have an angular resolution of 0.2 arc sec. The proposed P/OF configuration consists of four separate telescopes or position-sensitive counters mounted on a detector plane and looking toward the target through separate portions of an aperture mask (occulter plane). The two planes are separated by a self-deployable 50-m boom, which is to be made essentially rigid by direct control of its lowest normal modes.

Tandberg-Hanssen, E.↗
NASA NTRS1983

Solar oscillations observed in the total irradiance

An analysis of the total solar irradiance measurements made by the Solar Maximum Mission's active cavity radiometer, for evidence of global oscillations, has indicated that the most energetic low degree p-mode oscillations in the five-minute band have amplitudes of a few parts per million of the total irradiance. A positive detection is made of modes with l values of zero, 1 and 2. The distribution differs from that of the velocity spectrum, with relatively more power at the lower values of l. The 160-min oscillation is not detected in the power spectrum, and an upper limit of 5 parts per million is placed with 99% confidence on its amplitude.

Woodard, M.↗
NASA NTRS1979

Infrared continuum observations of the solar atmosphere

The far-infrared wavelengths (10 microns to 1 mm) were used to study the spatial and temporal structure of the solar atmosphere. Observational results were obtained on flares, faculae, sunspots, and on the center-to-limb intensity distribution, as well as on time variability within these regions. A program of precise monitoring of slow variations in the integrated solar luminosity was shown to be feasible, and initial steps to implement observations were completed.

Hudson, H.↗