Motions and magnetic fields in filaments

Based on the developed method of jointly using data on the magnetic fields and brightness of filaments and coronal holes (CHs) at various heights in the solar atmosphere as well as on the velocities in the photosphere, we have obtained the following results:

The upward motion of matter is typical of filament channels in the form of bright stripes that often surround the filaments when observed in the HeI 1083 nm line.

The filament channels observed simultaneously in Hα and HeI 1083 nm differ in size, emission characteristics, and other parameters. We conclude that by simultaneously investigating the filament channels in two spectral ranges, we can make progress in understanding the physics of their formation and evolution.

Most of the filaments observed in the HeI 1083 nm line consist of dark knots with different velocity distributions in them. A possible interpretation of these knots is offered.

The height of the small-scale magnetic field distribution near the individual dark knots of filaments in the solar atmosphere varies between 3000 and 20000 km.

The zero surface separating the large-scale magnetic field structures in the corona and calculated in the potential approximation changes the inclination to the solar surface with height and is displaced in one or two days.

The observed formation of a filament in a CH was accompanied by a significant magnetic field variation in the CH region at heights from 0 to 30000 km up to the change of the predominant field sign over the entire CH area. We assume that this occurs at the stage of CH disappearance.

     

Relationship between the motion of matter in coronal holes and their evolution

We consider the evolution of a long-lived coronal hole (CH) from February to August 2002 in the zone φ = ?20°…+15°, L = 30°–35°. Active structures emerged in it several times over its lifetime. After their disappearance, the CH was restored to its original form. The Carrington rotation R1989 from May 12 to May 26, 2002, is considered in detail. The relative CH areas have been determined for this rotation from observations in the HeI 1083 nm line. Based on observations in the NiI 676.8 nm line (SOHO, MDI), we have found the periods of the line-of-sight velocity variations. The variations of these periods in CHs are qualitatively compared with those of the CH areas. The oscillation periods in photospheric CH layers have been found to correlate linearly with the CH areas in the chromosphere. For the interval of observations May 12–26, 2002, we have identified 52 sites in CHs for which the area variations in the HeI 1083 nm line were estimated. For times close to the observations in the HeI 1083 nm line, we have determined the average velocities of vertical motion of matter from MDI data. The CH growth and decay have been found to be accompanied, respectively, by upward and downward motions of matter at the photospheric level.     

Relationship between the coronal holes and high-speed streams of solar wind

The relationship between two classes of coronal holes and high-speed quasi-stationary streams of solar wind at the Earth’s orbit is investigated. “Open” coronal holes, whose area is invariable or increases with the height over the solar surface, are rated in the first class, and “closed” coronal holes with areas decreasing with the height are referred to as second-class holes. The parameters of the coronal holes are determined from IR and EUV images and spectroheliograms. It is shown that most open coronal holes can be associated with high-speed solar-wind streams, while most closed coronal holes exhibit a much lower correlation with such streams.     

Study of Variations of Some Characteristics of the Giant Coronal Hole of 2015–2017

Geomagnetism and Aeronomy - Analysis of images of the full solar disk obtained by ground-based (BST-2, CrAO RAS) and space-based (SDO/AIA, SDO/HMI) instruments and the potential approximation...