We report progress on the ongoing recalibration of the Wolf sunspot number (SN) and group-sunspot number (GN) following the release of version 2.0 of SN in 2015. This report constitutes both an ...update of the efforts reported in the 2016 Topical Issue of Solar Physics and a summary of work by the International Space Science Institute (ISSI) International Team formed in 2017 to develop optimal SN and GN reconstruction methods while continuing to expand the historical sunspot-number database. Significant progress has been made on the database side while more work is needed to bring the various proposed SN and (primarily) GN reconstruction methods closer to maturity, after which the new reconstructions (or combinations thereof) can be compared with (a) “benchmark” expectations for any normalization scheme (e.g., a general increase in observer normalization factors going back in time), and (b) independent proxy data series such as F10.7 and the daily range of variations of Earth’s undisturbed magnetic field. New versions of the underlying databases for SN and GN will shortly become available for years through 2022 and we anticipate the release of the next versions of these two time series in 2024.
Our investigation has been carried using the instruments onboard the Solar Dynamics Observatory (SDO) providing a high resolution of images (AIA photographs and HMI magnetograms). We have ...investigated the structure and magnetic evolution of several coronal bright points and small scale N-S polarity magnetic fluxes closely associated with them. We also compare the evolution of the magnetic polarities of elementary isolated sources of positive and negative fluxes (magnetic bipoles) and coronal bright points. Tiny (“elementary”) coronal bright points have been detected. A standard coronal bright point is shown to be a group of “elementary” coronal bright points that flare up sequentially. Our investigation shows that a change in the magnetic fluxes of opposite polarities is observed before the flare of a coronal bright point. We show that not all cases of the formation of coronal bright points are described by the magnetic reconnection model. This result has not been considered previously and has not been pointed out by other authors.
The paper presents an analytical model of a magnetic tube, which is described as a cylindrically symmetric equilibrium state of two-component plasma. The plasma flow is represented as a superposition ...of two charged, compressible plasma components that only interact via their common electromagnetic field. The total electric charge density is assumed to be equal to zero. The system is in equilibrium under the influence of three forces: magnetic, centrifugal, and pressure gradient. The presented model is idealized and limited by the condition that the surrounding plasma is homogeneous and motionless. Despite this, the presented model, with the given parameters, makes it possible to calculate the main parameters of the magnetic flux tube.
An automated procedure for identification of coronal bright points is applied to selected EIT images observed at various phases of the solar cycle. The procedure finds about 400 bright points on a ...single EIT image observed at 195 AA. The positions of the bright points are tracked to study the profile of solar rotation in the solar corona. It is shown that the rotation of coronal bright points closely follows the latitudinal rotation profile of the underlying photospheric magnetic field. It is also demonstrated that coronal features situated at the same heliographic coordinates but different heights in the corona may exhibit different rotation rates.
Using full disk SOHO/EIT data from 1996 to 2006, we study latitudinal distribution of coronal bright points over a period of one solar cycle. We confirm the presence of two distinct types of coronal ...bright points, and find that the number of “quiet corona” bright points in high latitudes anticorrelate with solar activity as defined by the sunspot numbers.
We report progress on the ongoing recalibration of the Wolf sunspot number (SN) and Group sunspot number (GN) following the release of version 2.0 of SN in 2015. This report constitutes both an ...update of the efforts reported in the 2016 Topical Issue of Solar Physics and a summary of work by the International Space Science Institute (ISSI) International Team formed in 2017 to develop optimal SN and GN re-construction methods while continuing to expand the historical sunspot number database. Significant progress has been made on the database side while more work is needed to bring the various proposed SN and (primarily) GN reconstruction methods closer to maturity, after which the new reconstructions (or combinations thereof) can be compared with (a) ``benchmark'' expectations for any normalization scheme (e.g., a general increase in observer normalization factors going back in time), and (b) independent proxy data series such as F10.7 and the daily range of variations of Earth's undisturbed magnetic field. New versions of the underlying databases for SN and GN will shortly become available for years through 2022 and we anticipate the release of next versions of these two time series in 2024.
We find a polynomial solution of the Dirichlet problem for the inhomogeneous biharmonic equation with polynomial right-hand side and polynomial boundary data in the unit ball. To this end, we use the ...closed-form representation of harmonic functions in the Almansi formula.
Based on the properties of the Almansi representation, we obtain a representation for the polynomial solution to the Dirichlet problem. The formula obtained is convenient for computing the solution. ...Bibliography: 4 titles.
We present formulas that simplify finding the solutions of the Poisson equation, the inhomogeneous polyharmonic equation, and the inhomogeneous Helmholtz equation in the case of a polynomial ...right-hand side. They are based on the representation of an analytic function by harmonic functions. The resulting formulas remain valid for some analytic right-hand sides for which the corresponding operator series converge.
