Transition Region and Coronal Explorer (TRACE) TRACE explores the magnetic field in the solar atmosphere by studying: The 3-dimensional field structure Its temporal evolution in response to photospheric flows The time-dependent coronal fine structure The coronal and transition region thermal topology.  

                                        

TRACE FeXII Image TRACE Fe XII Image

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TRACE MOVIES

RAMATY HIGH ENERGY SOLAR SPECTROSCOPIC IMAGER (RHESSI) Investigates physics of particle acceleration and energy release in solar flares Observes X-rays and Gamma Rays 3 Kev - 20 Mev Combines high resolution imaging and spectroscopy Hard X-ray imaging at 2”, Dt of tens of ms, 1 Kev energy resolution Launched Feb. 15, 2002 Synergistic with SOHO, TRACE, ACE etc. PI: Bob Lin, U. California, Berkeley

45 million K f “blob” in July 23, 2002 Flare Lower energy image

HESSI's new approach Researchers believe that much of the energy released during a flare is used to accelerate, to very high energies, electrons (emitting primarily X-rays) and protons and other ions (emitting primarily gamma rays). The new approach of the HESSI mission is to combine, for the first time, high-resolution imaging in hard X-rays and gamma rays with high-resolution spectroscopy, so that a detailed energy spectrum can be obtained at each point of the image. This new approach will enable researchers to find out where these particles are accelerated and to what energies. Such information will advance understanding of the fundamental high-energy processes at the core of the solar flare problem.

Primary Scientific Objective To understand the following processes that take place in the magnetized plasmas of the solar atmosphere during a flare: - Impulsive energy release, - Particle acceleration, - Particle and energy transport These high-energy processes play a major role at sites throughout the universe ranging from magnetospheres to active galaxies. Consequently, the importance of understanding these processes transcends the field of solar physics; it is one of the major goals of space physics and astrophysics.

The high energy processes of interest include the following: The rapid release of energy stored in unstable magnetic configurations, The equally rapid conversion of this energy into the kinetic energy of hot plasma and accelerated particles (primarily electrons, protons and ions), The transport of these particles through the solar atmosphere and into interplanetary space, The subsequent heating of the ambient solar atmosphere. These processes involve: Particle energies to many GeV, Temperatures of tens or even hundreds of millions of degrees, Densities as low as 100 million particles per square cm, Spatial scales of tens of thousands of kilometers, and Magnetic containment times of seconds to hours. It is impossible to duplicate these conditions in laboratories on the Earth. The acceleration of electrons is revealed by hard X-ray and gamma-ray bremsstrahlung while the acceleration of protons and ions is revealed by gamma-ray lines and continuum.

Scientific Questions The fundamental unanswered questions concerning energy release and particle acceleration in solar flares are the following: What role do high energy particles play in the energy release process? Do the high energy particles carry a significant fraction of the released energy? What mechanisms accelerate both electrons and ions to high energies so rapidly and efficiently? What is the environment in which this energy release occurs? What mechanisms transport the flare energy, the energetic particle component in particular, away from the energy release site? What are the characteristic radiation signatures of flares that have potentially hazardous effects, and how do these flares occur and evolve?

Observational Objectives Locate energy release site and determine characteristics of energy release process. Locate particle acceleration and energy deposition sites during the different flare phases and determine how particle energy is dissipated throughout the flaring region. Determine the spectra and directivity of accelerated electrons and ions and their evolution in time and space. Determine the contribution of high-energy particles to flare energetics, specifically by measuring X-rays, gamma-rays, and the major contributors to the radiation energy budget, namely the soft X-ray and optical emissions. Characterize the plasma and the magnetic field in the region where the nonthermal processes occur. Determine if all flares, large and small, have similar characteristics suggesting that they are all manifestations of the same basic processes. Determine characteristics of microflares and estimate their contribution to coronal heating. Determine the elemental composition of the accelerated particles and of the solar atmosphere with which they interact. Study long-term storage and/or acceleration of high-energy ions at the Sun by observing nuclear-line emission for extended time periods prior to and following the impulsive phase of flares.

Observational Approach With appropriate context information, imaging and spectroscopic observations of hard X rays and gamma rays serve as the best diagnostics of the underlying physics of flares. HESSI capabilities: X-ray and gamma-ray imaging spectroscopy with the finest angular and energy resolutions ever achieved and with a higher sensitivity over a broader energy range than ever before, from a few keV to hundreds of keV. X-ray and gamma-ray spectroscopy with the finest energy resolution ever achieved and with high sensitivity to energies of at least 20 MeV. In order to achieve a full understanding of the acceleration of electrons and ions, and their transport through the solar atmosphere, it is essential to obtain support observations of the plasma and the magnetic fields where the hard X-ray and gamma-ray sources are situated, i.e., the thermal, dynamic, and magnetic context of the high energy flare. The required context observations are as follows: Soft X-ray, EUV, and UV imaging and spectroscopy from space with similar spatial and temporal resolutions to the X-ray and gamma-ray measurements. Radio and optical imaging and spectroscopy, and vector magnetic field measurements from the ground.

HESSI will obtain the following images and spectra of many solar flares: Hard X-ray images Angular resolution:  2 to 7 arcseconds Temporal resolution:  tens of milliseconds Energy Range:  3 keV to 400 keV These spatial and temporal resolving powers match the spatial and temporal scales that characterize the processes of energy release, acceleration, and transport. Such images will enable us not only to locate the energy release site or sites for the first time, but also to evaluate, both qualitatively and quantitatively, the evolution of the released energy as a result of interactions with the ambient atmosphere during the impulsive and gradual phases of many solar flares of different types. High-resolution X-ray spectra Resolution:  0.5 keV to 2 keV The measurement of the precise shape of the X-ray continuum made possible with such fine energy resolution will provide unique information on the spectrum of the accelerated electrons and on the heated plasma, thus allowing the thermal and nonthermal aspects of individual flares to be clearly distinguished.

Spectrally resolved hard X-ray images Such imaging spectroscopy, by which we mean high-resolution spectroscopy at each point of the X-ray image, with subsecond time resolution, will allow spectral changes to be measured as the electrons propagate along the magnetic field in the flaring loop or loops. It will provide powerful new constraints on the mechanisms of energy gain and loss. High-resolution gamma-ray spectra Energy resolution:  2 keV to 5 keV (FWHM) Energy range:  400 keV to 20 MeV The high-resolution spectra obtained with HESSI will provide unique information on the directionality of the interacting particles, the composition of both the ambient gas and the accelerated ions, and the temperature, density, and state of ionization of the ambient gas. Gamma-ray images Angular resolution:  7 to 30 arcseconds The exploratory high-resolution gamma-ray imaging spectroscopy will allow images to be obtained in specific gamma-ray lines or energy ranges such that, for example, the proton- and alpha-induced lines around 450 keV could be imaged separately, as could the 511 keV positron annihilation line. The intercomparison of images in radiation from different types of particles including electrons, positrons, protons, and alpha particles will allow the effects of differences in charge and mass on the acceleration and propagation processes to be explored for the first time.