V. N. Ishkov

Solar and Heliospheric Phenomena in October-November 2003: Causes and Effects

We present new observational data on the phenomena of extremely high activity on the Sun and in the heliosphere that took place in October–November 2003. A large variety of solar and heliospheric parameters give evidence that the interval under consideration is unique over the entire observation time. Based on these data, comparing them with similar situations in the past and using available theoretical concepts, we discuss possible cause-and-effect connections between the processes observed. The paper includes the first results and conclusions derived by the collaboration “Solar Extreme Events-2003” organized in Russia for detailed investigations of these events. As a result of our consideration, it is beyond question that the physical causes of solar and heliospheric phenomena in October–November 2003 are not exclusively local and do not belong only to the active regions and solar atmosphere above them. The energy reservoirs and driving forces of these processes have a more global nature. In general, they are hidden from an observer, since ultimately their sources lie in the subphotospheric layers of the Sun, where changes that are fast and difficult to predict can sometimes take place (and indeed they do). Solar flares can serve as sufficiently good tracers of these sudden changes and reconstructions on the Sun, although one can still find other diagnostic indicators among the parameters of magnetic fields, motions of matter, and emission characteristics.

Solar Proton Events in Solar Activity Cycles 21–24

It is shown that the number of solar proton events (SPEs) with proton energies (E) higher than 10 and 100 MeV in the current solar cycle (cycle 24) differs slightly from the number of the same events in earlier cycles (cycles 21–23), even though solar activity was low during the growth and maximum phase in cycle 24. A deficit was in this case observed for the most powerful GLE events, which are characterized by high proton fluxes with E > 100 MeV. The ratio of the number of SPEs with E > 10 and 100 MeV to the number of sunspots in cycle 24 doubled, compared to the same ratio in cycles 21–23, and the relative number of GLEs fell by more than half. The characteristics of flares and coronal mass ejections associated with proton events with E > 100 MeV in cycle 24 were virtually the same as the analogous parameters in cycle 23.

Complex active regions as the main source of extreme and large solar proton events

A study of solar proton sources indicated that solar flare events responsible for ≥2000 pfu proton fluxes mostly occur in complex active regions (CARs), i.e., in transition structures between active regions and activity complexes. Different classes of similar structures and their relation to solar proton events (SPEs) and evolution, depending on the origination conditions, are considered. Arguments in favor of the fact that sunspot groups with extreme dimensions are CARs are presented. An analysis of the flare activity in a CAR resulted in the detection of “physical” boundaries, which separate magnetic structures of the same polarity and are responsible for the independent development of each structure.

New Parameter in the Description of Solar Cosmic Ray Events—Energy of Balance between Solar and Galactic Protons

Solar proton events possess a wide variety of features that reflect the conditions of solar proton acceleration and propagation. Relevant investigations rely on statistical methods that make it possible to classify events with the aim of obtaining deeper insight into physical processes leading to the generation of solar cosmic rays. In classifying events in power, the intensity of particles with energy above 10MeV at the maximum of the event time profile or the fluence of particles throughout the event time is usually used. A new parameter, Eqm, that characterizes the proton event power and which is some kind of approximation of the maximum energy of accelerated particles is analyzed in the present study. Correlations of Eqm with properties of x-ray flares on the Sun and with the velocity of coronal mass ejections are examined.

Modern representation of databases on the example of the Catalog of Solar Proton Events in the 23rd Cycle of Solar Activity

The development of studies of solar sources and their effects on the state of the near-Earth space required systematization of the corresponding information in the form of databases and catalogs for the entire time of observation of any geoeffective phenomenon that includes, if possible at the time of creation, all of the characteristics of the phenomena themselves and the sources of these phenomena on the Sun. A uniform presentation of information in the form of a series of similar catalogs that cover long time intervals is of particular importance. The large amount of information collected in such catalogs makes it necessary to use modern methods of its organization and presentation that allow a transition between individual parts of the catalog and a quick search for necessary events and their characteristics, which is implemented in the presented Catalog of Solar Proton Events in the 23rd Cycle of Solar Activity of the sequence of catalogs (six separate issues) that cover the period from 1970 to 2009 (20th–23rd solar cycles).

A comparison of proton activity in cycles 20–23

The solar proton singularities in cycles 20–23 were compared. For such a comparison, it is of special importance to present information about solar proton events (SPEs) uniformly. The Katalog working group, including representatives of different institutions, created SPE catalogs for 1970–2010. These catalogs include solar events with E ≥ 10 MeV proton fluxes exceeding 1 cm−2 s−1 sr−1 near the Earth. The various conditions that accompany SPEs result in a considerable scatter of the flux parameters and energy spectra and in a difference in time profiles. Regularities in the distribution of these parameters during four solar activity cycles can be specifically revealed only based on a statistical approach that is used in this work. In this case a comparison can be successful only when the analyzed data series are homogeneous. Solar activity singularities during the entire period of SPE measurements (from cycle 19 to the end of cycle 23) are described. The methods for adjusting solar events in particles that are registered near the Earth to solar sources are of special importance. These statistical data suggest that the number of SPEs in the cycles and the event distribution within a solar cycle may indicate that the SPE generation character is different in cycles 20–21 and 22–23.