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1.
V. M. Grigorjev 《Solar physics》1969,6(1):67-71
Observations of longitudinal and transversal fields and of radial velocities in the magnetic ‘knots’ close to a sunspot were made with the help of Sayan Observatory magnetograph with spatial resolution 1″.2 x 1″.8. The analysis led to following conclusions:
- The magnetic field in the knots is mainly vertical. The mean inclination of the magnetic-field vector to the vertical direction is equal to 26°.
- The phenomenon of darkening is connected with essentially vertical fields and brightening in the faculae with the horizontal fields on the sun.
- An inverse relation between the value of darkening and the inclination of the field vector to the vertical direction and a direct relation on the longitudinal magnetic-field strength exist for the magnetic knots.
- The magnetic knots in the active region are located in the Hα flocculi near the line where the radial velocity is changing sign in the photosphere.
2.
We define for observational study two subsets of all polar zone filaments, which we call polemost filaments and polar filament bands. The behavior of the mean latitude of both the polemost filaments and the polar filament bands is examined and compared with the evolution of the polar magnetic field over an activity cycle as recently distilled by Howard and LaBonte (1981) from the past 13 years of Mt. Wilson full-disk magnetograms. The magnetic data reveal that the polar magnetic fields are built up and maintained by the episodic arrival of discrete f-polarity regions that originate in active region latitudes and subsequently drift to the poles. After leaving the active-region latitudes, these unipolar f-polarity regions do not spread equatorward even though there is less net flux equatorward; this indicates that the f-polarity regions are carried poleward by a meridional flow, rather than by diffusion. The polar zone filaments are an independent tracer which confirms both the episodic polar field formation and the meridional flow. We find:
- The mean latitude of the polemost filaments tracks the boundary of the polar field cap and undergoes an equatorward dip during each arrival of additional polar field.
- Polar filament bands track the boundary latitudes of the unipolar regions, drifting poleward with the regions at about 10 m s-1.
- The Mt. Wilson magnetic data, combined with a simple model calculation, show that the filament drift expected from diffusion alone would be slower than observed, and in some cases would be equatorward rather than poleward.
- The observation that filaments drift poleward along with the magnetic regions shows that fields of both polarities are carried by the meridional flow, as would be expected, rather than only the f-polarity flux which dominates the strength. This leads to the prediction that in the mid-latitudes during intervals between the passage of f-polarity regions, both polarities are present in nearly equal amounts. This prediction is confirmed by the magnetic data.
3.
At the Swedish Solar Observatory in Anacapri we have simultaneously used the following combination of instruments in our investigation of active regions:
- A spectrograph with an image rotator placed in front of the slit.
- A subtractive double dispersive spectrograph (solar Chromatograph).
- A Hα+0.5 Å patrol instrument. Scans over the 3b flare of August 4th 1972 are used to illustrate the method. The illustrations clearly show downflowing matter connected with bright knots and filaments in the emitting area, possibly in accordance with Hyder's infall-impact mechanism.
4.
Markus J. Aschwanden 《Journal of Astrophysics and Astronomy》2008,29(1-2):3-16
Celebrating the diamond jubilee of the Physics Research Laboratory (PRL) in Ahmedabad, India, we look back over the last six decades in solar physics and contemplate on the ten outstanding problems (or research foci) in solar physics:
- The solar neutrino problem
- Structure of the solar interior (helioseismology)
- The solar magnetic field (dynamo, solar cycle, corona)
- Hydrodynamics of coronal loops
- MHD oscillations and waves (coronal seismology)
- The coronal heating problem
- Self-organized criticality (from nanoflares to giant flares)
- Magnetic reconnection processes
- Particle acceleration processes
- Coronal mass ejections and coronal dimming
5.
Brigitte Schmieder 《Journal of Astrophysics and Astronomy》2006,27(2-3):139-149
The majority of flare activity arises in active regions which contain sunspots, while Coronal Mass Ejection (CME) activity can also originate from decaying active regions and even so-called quiet solar regions which contain a filament. Two classes of CME, namely flare-related CME events and CMEs associated with filament eruption are well reflected in the evolution of active regions. The presence of significant magnetic stresses in the source region is a necessary condition for CME. In young active regions magnetic stresses are increased mainly by twisted magnetic flux emergence and the resulting magnetic footpoint motions. In old, decayed active regions twist can be redistributed through cancellation events. All the CMEs are, nevertheless, caused by loss of equilibrium of the magnetic structure. With observational examples we show that the association of CME, flare and filament eruption depends on the characteristics of the source regions: ?the strength of the magnetic field, the amount of possible free energy storage, ?the small- and large-scale magnetic topology of the source region as well as its evolution (new flux emergence, photospheric motions, cancelling flux), and ?the mass loading of the configuration (effect of gravity). These examples are discussed in the framework of theoretical models. 相似文献
6.
Coordinates of polar faculae have been measured and processed using daily photoheliograms of the Kislovodsk Station of the Pulkovo observatory with the final goal of studying their latitude distribution during the solar cycles 20–21. The results obtained are as follows:
- The first polar faculae emerge immediately after the polarity inversion of the solar magnetic field at the latitudes from 40° to 70° with the average ?-55°.
- The zone of the emergence of polar faculae migrates poleward during the period between the neighbouring polarity inversions of the solar magnetic field. This migration is about 20° for 8 years, which corresponds to a velocity of 0.5 m s-1.
- The maximum number of polar faculae was reached at the activity minimum (1975–1976).
- The last polar faculae were observed in the second half of 1978 at the latitudes from 70° to 80°.
7.
Yu. A. Nagovitsyn 《Astrophysical Bulletin》2008,63(1):43-55
We report the results of the application of our approach to study the behavior of solar activity in the past, where: When reconstructing the variations of solar activity, geomagnetic parameters, and the interplanetary magnetic field in the past we select a sequence of increasing time scales, which can be naturally represented by the potentials of available observational data. We select a total of four time scales: 150–200 years, 400 years, 1000 years, and 10000 years. When constructing the series of each successive (in terms of length) time scale we use the data of the previous time scale as reference data. We abandon, where possible, the series of traditional statistical parameters in favor of the series of physical parameters. When deriving the relations between any parameters of solar activity, geomagnetic disturbance, and the interplanetary magnetic field, we take into account the differential nature of relations on different time scales. To this end, we use the earlier proposed MSR and DPS methods. To verify the resulting reconstructions, we use the “principle of witnesses”, which uses independent (in some cases, indirect) information as initial data. 相似文献
8.
9.
J. René Roy 《Solar physics》1973,28(1):95-114
High resolution on- and off-band Hα filtergrams of disk solar surges obtained with the Vacuum Tower Telescope of the Sacramento Peak Observatory have been compared to magnetic data.
- Surges constitute clusters of very fine dark (sometimes bright) filaments where each thread connects to an Ellerman bomb brightening. If the magnetic map reveals the existence of a satellite polarity as defined by Rust (1968), the bomb(s) lies over it.
- Although a large fraction of surges is not associated with clearly detectable satellite polarities, events are strongly favored in regions of evolving magnetic features, characterized by dimensions of about 10 000 km and significant flux change over a period of less than a day. A flux change rate of 3 × 1015 Mx s?1 has been measured along at least three homologous bomb-surge events in a satellite of region MW 18594. Surges appear to be related to rising flux of one polarity into a region of stronger opposite flux.
- The trajectories of surges are matched by magnetic lines of force computed in the current-free approximation.
10.
The properties of small (< 2″) moving magnetic features near certain sunspots are studied with several time series of longitudinal magnetograms and Hα filtergrams. We find that the moving magnetic features:
- Are associated only with decaying sunspots surrounded entirely or in part by a zone without a permanent vertical magnetic field.
- Appear first at or slightly beyond the outer edge of the parent sunspot regardless of the presence or absence of a penumbra.
- Move approximately radially outward from sunspots at about 1 km s?1 until they vanish or reach the network.
- Appear with both magnetic polarities from sunspots of single polarities but appear with a net flux of the same sign as the parent sunspot.
- Transport net flux away from the parent sunspots at the same rates as the flux decay of the sunspots.
- Tend to appear in opposite polarity pairs.
- Appear to carry a total flux away from sunspots several times larger than the total flux of the sunspots.
- Produce only a very faint emmission in the core of Hα.
11.
The properties of rapidly changing inhomogeneities visible in the H and K lines above sunspot umbrae are described. We find as properties for these ‘Umbral Flashes’:
- A lifetime of 50 sec. The light curve is asymmetrical, the increase is faster than the decrease in brightness.
- A diameter ranging from the resolution limit up to 2000 km.
- A tendency to repeat every 145 sec.
- A ‘proper motion’ of 40 km/sec generally directed towards the penumbra.
- A Doppler shift of 6 km/sec.
- A magnetic field of 2100 G.
- A decrease in this field of 12 G/sec. This decrease is probably related to the flash motion.
- At any instant an average of 3–5 flashes in a medium-sized umbra. A weak feature often persists in the umbra after the flash. This post-flash structure initially shows a blue shift, but 100–120 sec after the flash, it shows a rapid red shift just before the flash repeats.
12.
Markus J. Aschwanden 《Journal of Astrophysics and Astronomy》2008,29(1-2):115-124
The Transition Region and Coronal Explorer (TRACE) gave us the highest EUV spatial resolution and the Ramaty High Energy Solar Spectrometric Imager (RHESSI) gave us the highest hard X-ray and gammaray spectral resolution to study solar flares. We review a number of recent highlights obtained from both missions that either enhance or challenge our physical understanding of solar flares, such as:
- Multi-thermal Diagnostic of 6.7 and 8.0 keV Fe and Ni lines
- Multi-thermal Conduction Cooling Delays
- Chromospheric Altitude of Hard X-Ray Emission
- Evidence for Dipolar Reconnection Current Sheets
- Footpoint Motion and Reconnection Rate
- Evidence for Tripolar Magnetic Reconnection
- Displaced Electron and Ion Acceleration Sources.
13.
Correlation and spectral analysis of solar radio flux density and sunspot number near the maximum of the sunspot cycle has indicated the existence of
- long period amplitude modulation of the slowly varying component (SVC) of radio emission
- coronal storage over a period of the order of three solar rotations
- fast decay (one solar rotation period or less) of gyromagnetic emissions from radio sources
- shift in location of chromospheric sources compared to those of either the upper corona or the photosphere.
14.
David M. Rust 《Solar physics》1972,25(1):141-157
An observational study of maps of the longitudinal component of the photospheric fields in flaring active regions leads to the following conclusions:
- The broad-wing Hα kernels characteristic of the impulsive phase of flares occur within 10″ of neutral lines encircling features of isolated magnetic polarity (‘satellite sunspots’).
- Photospheric field changes intimately associated with several importance 1 flares and one importance 2B flare are confined to satellite sunspots, which are small (10″ diam). They often correspond to spot pores in white-light photographs.
- The field at these features appears to strengthen in the half hour just before the flares. During the flares the growth is reversed, the field drops and then recovers to its previous level.
- The magnetic flux through flare-associated features changes by about 4 × 1019 Mx in a day. The features are the same as the ‘Structures Magnétiques Evolutives’ of Martres et al. (1968a).
- An upper limit of 1021 Mx is set for the total flux change through McMath Regions 10381 and 10385 as the result of the 2B flare of 24 October, 1969.
- Large spots in the regions investigated did not evince flux changes or large proper motions at flare time.
- The results are taken to imply that the initial instability of a flare occurs at a neutral point, but the magnetic energy lost cannot yet be related to the total energy of the subsequent flare.
- No unusual velocities are observed in the photosphere at flare time.
15.
A clarification and discussion of the energy changes experienced by cosmic rays in the interplanetary region is presented. It is shown that the mean time rate of change of momentum of cosmic rays reckoned for a fixed volume in a reference frame fixed in the solar system is 〈p〉 =p V·G/3 (p=momentum,V is the solar wind velocity andG=cosmic-ray density gradient). This result is obtained in three ways:
- by a rearrangement and reinterpretation of the cosmic-ray continuity equation;
- by using a scattering analysis based on that of Gleeson and Axford (1967);
- by using a special scattering model in which cosmic-rays are trapped in ‘magnetic boxes’ moving with the solar wind.
16.
B. Lehnert 《Astrophysics and Space Science》1976,40(1):225-229
A one-dimensional model is being considered where a fully ionized plasma is separated from a neutral gas by a homogeneous magnetic field directed along the plasma boundary. The plasma and the neutral gas consist of two different types of ions and neutral particles. In a stationary state the outflux of plasma by diffusion across the magnetic field is compensated by an influx of neutrals which are ionized in a partially ionized boundary region. It is found that the ratio between the ion densities in the fully ionized region will in general differ from the density ratio of the two types of neutrals being present in the gas region. This provides a separation mechanism with applications both to cosmical and laboratory plasmas, such as in the following cases:
- The abundance anomalies in magnetic variable stars and in the solar wind.
- Separation processes of non-identical ions and neutral atoms in gas blanket systems.
17.
Spectroheliograms, obtained in certain Fraunhofer lines with the 82-cm solar image at the Kitt Peak National Observatory, show a bright photospheric network having the following properties:
- It resembles, but does not coincide with, the chromospheric network, the structure of the photospheric network being finer and more delicate than the relatively coarse structure of the chromospheric network.
- It is exactly cospatial with the network of non-sunspot photospheric magnetic fields.
- Its visibility in a given photospheric Fraunhofer line is primarily dependent on the states of ionization and excitation from which the line is formed and secondarily dependent on the Zeemansensitivity of the line-being most visible in low-excitation lines of neutral atoms and least visible in high-excitation lines of singly ionized atoms.
18.
After adding the data observed in the years from 1979 to 1982 to those obtained earlier (Ding et al., 1981), we re-examine the previous results and conclude:
- The longitudinal distribution of spiral spots on the solar disc is generally the same as that of sunspot groups with areas of S p ≥ 400, but their active longitudes seem to be more concentrated.
- The distribution of spiral patterns in the southern and northern hemispheres shows that the differential rotation may be a fundamental solar dynamo for the formation of the spiral spots.
- The statistical directions of the emerging twisted magnetic vectors in the active regions in the southern and northern hemispheres are synchronously inverse with a period of about two years. This period seems to be detected in other solar observations.
19.
N. M. Firstova 《Solar physics》1984,90(2):269-279
Using the Baranger-Mozer method, we explore the possibility of diagnosing the flare plasma of forbidden Hei lines, that permits the determination of the plasma oscillation frequency and noise level. Examination of the Hei lines observed in solar flare has led us to conclude that:
- the appearance of satellites of forbidden components in the flares spectrum, due to turbulent electric fields, is the most probable for Hei 3819.606 Å lines;
- the Baranger-Mozer method is more sensitive to the high-frequency component of turbulent fields than to the low-frequency ones;
- the upper limit of the turbulent oscillation level in flares is evaluated.
20.
Franz-Ludwig Deubner 《Solar physics》1971,17(1):6-20
Photoelectric measurements of Doppler shifts of various Fraunhofer lines obtained with the Capri magnetograph were analysed. The height dependence of the supergranular and oscillatory motions, as well as the two dimensional structure of these velocity fields is investigated. The most interesting results are the following:
- The oscillatory and supergranular motions are still clearly present in very deep photospheric layers as detected e.g. by means of the Ci line at 5380.3 Å.
- Whereas the vertical motions (both of oscillation and supergranulation) increase with height, the horizontal component of the supergranular flow is found to be decreasing slightly.
- Aperiodic horizontal motions are observed in the photospheric layers, which are probably connected with the process of excitation of the oscillatory field.
- There is no simple way of describing the oscillatory field in terms of independently oscillating ‘cells’, since the two-dimensional pattern changes its appearance drastically already in a fraction of one oscillation period.
- The correlation obtained by previous observers between vertical stationary motions, the chromospheric network and magnetic fields in particular is confirmed.