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We present the results of the study of the magnetic field in the active prominence on July 24, 1999 at 07:00 UT, using the observational material obtained on the Echelle spectrograph of the horizontal solar telescope of the Astronomical Observatory of Taras Shevchenko Kyiv National University. Our analysis is based on the study of I ± V profiles of the Hα line, which were related to heights in the range of 11–20 Mm. It was found that the bisectors of the I ± V profiles are non-parallel to each other in majority of places of this prominence. This indicates the inhomogeneity of the magnetic field: with a uniform magnetic field, the named bisectors should be parallel. Moreover, the maximum splitting of bisectors is observed not only in the core of the line (which was found earlier by other authors), but also in its far wings, at distances of 1.5–2.5 Å from the line center. The specified maximum of splitting corresponds to magnetic field of about 3000 G, but this value should be considered only as a lower estimate of the true local magnetic fields. In particular, the second maximum of bisector splitting may indicate that the actual value of Zeeman splitting in small-scale structures with a small filling factor reaches the above value of 1.5–2.5 Å which corresponds to the field strength of almost 100 kG. From our study it follows that evidences on such extremely magnetic fields may not actually be a rare phenomenon, but a rather common one, which, however, can be recorded only under certain favorable observational conditions. [ABSTRACT FROM AUTHOR]

The Sun is replete with magnetic fields, with sunspots, pores and plage regions being their most prominent representatives on the solar surface. But even far away from these active regions, magnetic fields are ubiquitous. To a large extent, their importance for the thermodynamics in the solar photosphere is determined by the total magnetic flux. Whereas in low-flux quiet Sun regions, magnetic structures are shuffled around by the motion of granules, the high-flux areas like sunspots or pores effectively suppress convection, leading to a temperature decrease of up to 3000 K. The importance of magnetic fields to the conditions in higher atmospheric layers, the chromosphere and corona, is indisputable. Magnetic fields in both active and quiet regions are the main coupling agent between the outer layers of the solar atmosphere, and are therefore not only involved in the structuring of these layers, but also for the transport of energy from the solar surface through the corona to the interplanetary space. Consequently, inference of magnetic fields in the photosphere, and especially in the chromosphere, is crucial to deepen our understanding not only for solar phenomena such as chromospheric and coronal heating, flares or coronal mass ejections, but also for fundamental physical topics like dynamo theory or atomic physics. In this review, we present an overview of significant advances during the last decades in measurement techniques, analysis methods, and the availability of observatories, together with some selected results. We discuss the problems of determining magnetic fields at smallest spatial scales, connected with increasing demands on polarimetric sensitivity and temporal resolution, and highlight some promising future developments for their solution. [ABSTRACT FROM AUTHOR]

Measuring the coronal vector magnetic field is still a major challenge in solar physics. This is due to the intrinsic weakness of the field (e.g. ~4G at a height of 0.1Rsun above an active region) and the large thermal broadening of coronal emission lines. We propose using concurrent linear polarization measurements of near-infrared forbidden and permitted lines together with Hanle effect models to calculate the coronal vector magnetic field. In the unsaturated Hanle regime both the direction and strength of the magnetic field affect the linear polarization, while in the saturated regime the polarization is insensitive to the strength of the field. The relatively long radiative lifetimes of coronal forbidden atomic transitions implies that the emission lines are formed in the saturated Hanle regime and the linear polarization is insensitive to the strength of the field. By combining measurements of both forbidden and permitted lines, the direction and strength of the field can be obtained. For example, the SiX 1.4301 um line shows strong linear polarization and has been observed in emission over a large field-of-view (out to elongations of 0.5 Rsun. Here we describe an algorithm that combines linear polarization measurements of the SiX 1.4301 um forbidden line with linear polarization observations of the HeI 1.0830 um permitted coronal line to obtain the vector magnetic field. To illustrate the concept we assume the emitting gas for both atomic transitions is located in the plane of the sky. The further development of this method and associated tools will be a critical step towards interpreting the high spectral, spatial and temporal infrared spectro-polarimetric measurements that will be possible when the Daniel K. Inouye Solar Telescope (DKIST) is completed in 2019.

High resolution spectro-polarimetric observations of a sunspot light bridge by Hinode , reveal small-scale inhomogeneities in the magnetic field and velocity. These inhomogeneities arise as a consequence of a weak, secondary lobe in the Stokes V profile which have a polarity opposite that of the sunspot and very large (>5 km s −1 ) Doppler velocities of both signs, suggesting two distinct types of magnetic anomalies. These two sets of inhomogeneities are highly time-dependent and appear exclusively in the upper half of the light bridge and only after the light bridge is completely formed. Both sets of inhomogeneities appear as patches and can be present independent of the other, next to one another, or spatially separated in a single scan. A two-component inversion of the corresponding spectral profiles indicates that the inhomogeneities occupy a very small fraction, amounting to less than 10%, of the resolution element. These structures are likely driven by small-scale magneto-convection where they could further interact with the overlying sunspot magnetic field to produce reconnection jets in the chromosphere. [ABSTRACT FROM AUTHOR]

Abstract: Large current uncertainties in the characteristics of aerosols in the Earth''s atmosphere preclude meaningful climate model evaluation. The FAST mission will contribute to the characterization of aerosols and their relation to climate change through a synoptic evaluation of local, regional and global aerosol data and altitude profiles of the cryosphere. The Dutch–Chinese mission will implement this objective through a unique combination of payloads onboard of two cooperating micro-satellites flying in formation in a Low-Earth Orbit. The FAST payload suite is unique in that it allows an unprecedented characterization of aerosols through a spectro-polarimeter instrument, which, in combination with radar and laser altimeter data, contributes to the characterization of the indirect climate forcing due to aerosols. Finally, flying instruments on two satellites in formation allows an exceptional flexibility to study the temporal and spatial distribution and evolution of aerosols in the Earth''s atmosphere. [Copyright &y& Elsevier]