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Solar flare phenomena are examined in an introduction for advanced undergraduate and graduate physics students. Chapters are devoted to the history of observations, flare spectroscopy, flare magnetohydrodynamics, flare plasma physics, radiative processes in the solar plasma, preflare conditions, the impulsive phase, the gradual phase, and coronal mass ejections. Diagrams, graphs, and photographs are provided.
This paper describes mainly the 1997 version of the Solar EUV Rocket Telescope and Spectrograph (SERTS-97), a scientific experiment that operated on NASA's suborbital rocket flight 36.167-GS. Its function was to study activity on the Sun and to provide a cross calibration for the CDS instrument on the SOHO satellite. The experiment was designed, built, and tested by the Solar Physics Branch of the Laboratory for Astronomy and Solar Physics at the Goddard Space Flight Center (GSFC). Other essential sections of the rocket were built under the management of the Sounding Rockets Program Office. These sections include the electronics, timers, IGN despin, the SPARCS pointing controls, the S-19 flight course correction section, the rocket motors, the telemetry, ORSA, and OGIVE.
This ad hoc panel met in February 1977 to consider the needs of solar physics for space missions after the scheduled flight of Solar Maximum Mission in 1979. We were concerned only with scientific needs and opportunities. Neither budgetary implications nor payload feasibility were considered. This report on the panel deliberations therefore makes suggestions only. We hope it will be a useful input to the more extensive and careful analysis of the appropriate committees, such as the Solar Physics Working Group. We have made no attempt to prioritize our proposed mission. The following possible missions are describes briefly: A Solar Terrestrial Environment Mission; two versions of a Stereo Mission; a Large Scale Solar Structure Mission; a Solar Atmosphere Mission; a Solar Particle Acceleration Mission; and a Solar Pinhole Mission. We also append a brief account of the proposed Solar Probe Mission.
Solar neutrinos coming from different nuclear reactions are now detected with high statistics. Consequently, an accurate spectroscopic analysis of the neutrino fluxes arriving on Earth's detectors becomes available, in the context of neutrino oscillations. In this work, we explore the possibility of using this information to infer the radial profile of the electronic density in the solar core. So, we discuss the constraints on the Sun's density and chemical composition that can be determined from solar neutrino observations. This approach constitutes an independent and alternative diagnostic to the helioseismic investigations already done. The direct inversion method, which we propose to obtain the radial solar electronic density profile, is almost independent of the solar model.
The development of the Zeeman–Doppler Imaging (ZDI) technique has provided synoptic observations of surface magnetic fields of low-mass stars. This led the stellar astrophysics community to adopt modeling techniques that have been used in solar physics using solar magnetograms. However, many of these techniques have been neglected by the solar community due to their failure to reproduce solar observations. Nevertheless, some of these techniques are still used to simulate the coronae and winds of solar analogs. Here we present a comparative study between two MHD models for the solar corona and solar wind. The first type of model is a polytropic wind model, and the second is the physics-based AWSOM model. We show that while the AWSOM model consistently reproduces many solar observations, the polytropic model fails to reproduce many of them, and in the cases where it does, its solutions are unphysical. Our recommendation is that polytropic models, which are used to estimate mass-loss rates and other parameters of solar analogs, must first be calibrated with solar observations. Alternatively, these models can be calibrated with models that capture more detailed physics of the solar corona (such as the AWSOM model) and that can reproduce solar observations in a consistent manner. Without such a calibration, the results of the polytropic models cannot be validated, but they can be wrongly used by others.
The basic subject of this volume is the solar astronomy program conducted on Skylab. In addition to descriptions of the individual experiments and the principles involved in their performance, a brief description is included of the sun and the energy characteristics associated with each zone. Wherever possible, related classroom activities have been identified and discussed in some detail. It will be apparent that the relationships rest not only in the field of solar astronomy, but also in the following subjects: (1) physics - optics, electromagnetic spectrum, atomic structure, etc.; (2) chemistry - emission spectra, kinetic theory, X-ray absorption, etc.; (3) biology - radiation and dependence on the sun; (4) electronics - cathode ray tubes, detectors, photomultipliers, etc.; (5) photography; (6) astronomy; and (7) industrial arts.
We present updated constraints on dark matter models with momentum-dependent or velocity-dependent interactions with nuclei, based on direct detection and solar physics. We improve our previous treatment of energy transport in the solar interior by dark matter scattering, leading to significant changes in fits to many observables. Based on solar physics alone, DM with a spin-independent q{sup 4} coupling provides the best fit to data, and a statistically satisfactory solution to the solar abundance problem. Once direct detection limits are accounted for however, the best solution is spin-dependent v{sup 2} scattering with a reference cross-section of 10{sup −35} cm{sup 2} (at a reference velocity of v{sub 0}=220 km s{sup −1}), and a dark matter mass of about 5 GeV.
Ion chemistry of D and E regions to be studied during years of solar maximum in framework of IQSY/IUCSTP
A double-chambered gas proportional counter was constructed to detect and identify solar wind ions after acceleration by a high voltage power supply. It was determined that the best method of detecting deuterium in the solar wind is to use a tritium target as proposed for IMP H and J. The feasibility of detecting H(+) and He(+) ions of interstellar origin is considered. A program is described to carry out ground-based astronomical observations of faint, diffuse optical emission lines from interstellar gas. Hydrogen and oxygen emission lines from galactic sources were detected and the galactic and geocoronal H alpha and beta lines were clearly resolved.
During the past year we have been working with the HESSI (High Energy Solar Spectroscopic Imager) team in preparation for launch in early 2001. HESSI has as its primary scientific goal photometric imaging and spectroscopy of solar flares in hard X-rays and gamma-rays with an approx. 2 sec angular resolution, approx. keV energy resolution and approx. 2 s time resolution over the 6 keV to 15 MeV energy range. We have performed tests of the imager using a specially designed experiment which exploits the second-harmonic response of HESSI's sub-collimators to an artificial X-ray source at a distance of 1550 cm from its front grids. Figures show the response to X-rays at energies in the range where HESSI is expected to image solar flares. To prepare the team and the solar user community for imaging flares with HESSI, we have written a description of the major imaging concepts. This paper will be submitted for publication in a referred journal.
An important question in solar physics is whether solar microflares, the smallest currently observable flare events in X-rays, possess the same energetic properties as large flares. Recent surveys have suggested that microflares may be less efficient particle accelerators than large flares, and hence contribute less non-thermal energy, which may have implications for coronal heating mechanisms. We therefore explore the energetic properties of microflares by combining EUV and X-ray measurements. We present forward-fitting differential emission measure (DEM) analysis of 10 microflares. The fitting is constrained by combining, for the first time, high-temperature Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observations and flux data from the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA). Two fitting models are tested for the DEM; a Gaussian distribution and a uniform DEM profile. A Gaussian fit proved unable to explain the observations for any of the studied microflares. However, 8 of 10 events studied were reasonably fit by a uniform DEM profile. Hence microflare plasma can be considered to be significantly multi-thermal, and may not be significantly peaked or contain resolvable fine structure, within the uncertainties of the observational instruments. The thermal and non-thermal energy is estimated for each microflare, comparing the energy budget with an isothermal plasma assumption. From the multi-thermal fits the minimum non-thermal energy content was found to average approximately 30% of the estimated thermal energy. By comparison, under an isothermal model the non-thermal and thermal energy estimates were generally comparable. Hence, multi-thermal plasma is an important consideration for solar microflares that substantially alters their thermal and non-thermal energy content.
The various payloads planned for Spacelab are discussed with emphasis on the experimental objectives of the payload, the state of planning or development, and the planned flight schedule. Attention is given to payloads involving life sciences, atmospheric and space physics, infrared astronomy, solar physics, ultraviolet/optical astronomy, and high energy astrophysics.
Mission configurations, instrumentation, and objectives for Spacelab sorties on board the Shuttle beginning in Sept. 1983 are reviewed. The first two flights will serve to verify the Spacelab systems and will be followed by operational status, including the fifth flight, which will be a reimbursible venture. Scientific investigations in the fields of atmospheric physics and environmental observation, space plasma physics, astronomy and solar physics, materials processing, and life sciences will be performed using the habitable long module, instrument pallets, and/or an instrument igloo mounted in the payload bay. Instrumentation, such as the imaging spectrometric observatory, which was developed in the U.S., will originate in either the U.S. or Europe. Details of the first four Spacelab flights are presented, noting that the OSS-3 through -7 missions will feature the first time that entire NASA payloads have returned to space.
Experiments and facilities selected for flight on the first Spacelab mission are described. Chosen from responses to the Announcement of Opportunity for the Spacelab 1 mission, the experiments cover five broad areas of investigation: atmospheric physics and Earth observations; space plasma physics; astronomy and solar physics; material sciences and technology; and life sciences. The name of the principal investigator and country is listed for each experiment.
The payload ground processing of experiments which flew on the Shuttle is examined, including studies of atmosphere and earth observation, life science, advance technology, materials science, plasma physics, astrophysics and solar physics, astronomy, navigation and communication, and fluid mechanics. The process of designing and development payloads, the integration of instruments, carrier interface verification, and late servicing at the launch pad are discussed. The problems of cost, red tape, contamination, safety, and propriety protection are considered.
An important question in solar physics is whether solar microflares, the smallest currently observable flare events in X-rays, possess the same energetic properties as large flares. Recent surveys have suggested that microflares may be less efficient particle accelerators than large flares, and hence contribute less non-thermal energy, which may have implications for coronal heating mechanisms. We therefore explore the energetic properties of microflares by combining EUV and X-ray measurements. We present forward-fitting differential emission measure (DEM) analysis of 10 microflares. The fitting is constrained by combining, for the first time, high-temperature Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observations and flux data from the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA). Two fitting models are tested for the DEM; a Gaussian distribution and a uniform DEM profile. A Gaussian fit proved unable to explain the observations for any of the studied microflares. However, 8 of 10 events studied were reasonably fit by a uniform DEM profile. Hence microflare plasma can be considered to be significantly multi-thermal, and may not be significantly peaked or contain resolvable fine structure, within the uncertainties of the observational instruments. The thermal and non-thermal energy is estimated for each microflare, comparing the energy budget with an isothermal plasma assumption. From the multi-thermal fits the minimum non-thermal energy content was found to average approximately 30% of the estimated thermal energy. By comparison, under an isothermal model the non-thermal and thermal energy estimates were generally comparable. Hence, multi-thermal plasma is an important consideration for solar microflares that substantially alters their thermal and non-thermal energy content.
The scientific objectives and implementation plans and priorities of the Space Science Board in areas of solar physics, heliospheric physics, magnetospheric physics, upper atmosphere physics, solar-terrestrial coupling, and comparative planetary studies are discussed and recommended programs are summarized. Accomplishments of Skylab, Solar Maximum Mission, Nimbus-7, and 11 other programs are highlighted. Detailed mission plans in areas of solar and heliospheric physics, plasma physics, and upper atmospheric physics are also described.
The main physical mechanisms responsible for the generation and transfer of polarized radiation in the solar atmosphere can be classified in a suitable bidimensional diagram with an indicator of the magnetic field strength on its vertical axis and an indicator of the radiation field anisotropy on its horizontal axis. The various polarimetric observations performed on solar spectral lines are interpreted with different theoretical schemes according to their classification in the diagram and to the optical depths involved. These theoretical schemes, and the associated diagnostic tools for inferring the magnetic field vector from observations are reviewed. In particular, the role of magneto-optical effects in determining the direction of the observed linear polarization in active regions is discussed in some detail.