K. G. Ivanov

Generation of the Katrine hurricane during the geomagnetic extrastrom at crossing of the heliospheric current sheet: Is it an accidental coincidence or physical essence?

Attention is paid to the generation of the Katrine hurricane with destructive consequences during the geomagnetic extrastorm of August 24, 2005, at a repeated crossing of the strongly disturbed IMF sector boundary. This fact is discussed in the light of the Eigenson-Usmanov hypothesis that solar activity can affect generation of hurricanes. According to the law of enhancement, solar activity and corresponding geomagnetic disturbances increase baric contrasts in the lower atmosphere over oceans on the Earth’s dayside hemisphere and decrease background pressure at tropical latitudes. It has been assumed that this can be one of the factors facilitating triggering of the positive feedback mechanisms necessary for generation and maintenance of hurricanes according to the Golitsyn [1999] model.

Solar-terrestrial storms of October 2003. 2. Five-phase dynamics of the substorm of October 28–30

The assumption that a solar-heliospheric storm has five phases is formulated based on the storm that occurred in October 2003. The first phase: slow (between solar rotations) convergent motions of photospheric sources of large-scale open solar fields (LOFs) with generation of active regions (ARs) between these fields. The second phase: magnetic energy pumping with adjustment of zero lines of the photospheric magnetic field in AR to the configuration of the LOF sector (subsector) boundaries. The third phase: AR destabilization with ordering of the complex of sporadic phenomena near ARs parallel to the zero line and fragments of the nearest LOF boundary. The fourth phase: propagation of disturbances in the near-Sun space with ordering relative to the LOF boundaries. The fifth phase: propagation of a coronal mass ejection (CME) in the inner heliosphere in the case when the axial axis of a magnetic cloud in CME is parallel to the LOF boundary and to the zero line in AR. Original results of LOF modeling and a number of substantial results of the known advanced studies of individual aspects of this storm are used to justify this dynamics as applied to the storm of October 28–30. Specific contents and features of each storm phases are presented. The specific feature of the first phase, responsible for the storm space-time scales and intensity, consisted in the displacement of the entire LOF negative magnetic flux (∼5 × 1022 μs) from the north pole to the south with flowing around a midlatitude obstacle and with zonal convergent motions of LOF. The assumption of the AR configuration adjustment (the second phase) and ordering of disturbances (the third–five phases) during this storm near the subsector boundary between LOFs of identical polarity has been confirmed. It is noted that the pulse phase of the AR 0486 flare, coronal waves, and dimmings along the subsector boundary and the southwestern LOF “dam” joining ARs 0486 and 0484 (superposition of the third and fourth phases) originated almost simultaneously. The two-component disturbance structure is confirmed: halo-type CME with the axis along the LOF subsector boundary and a bright local ejection of magnetic plasma from the region above the southwestern LOF dam.

Controlled injection of high-power radio pulses into the ionosphere-magnetosphere system and appearance of microsubstorms on October 2, 2007

Insignificant geomagnetic disturbances, which originated during the experimental injection of high-power radio pulses into the magnetosphere-ionosphere system with the help of an HF transmitter of the Sura heating facility, are considered. The experiment was performed at 1840–1900 UT on October 2, 2007 (∼2100 MLT) at geomagnetic latitudes close to the zone of generation of the current wedge westward branch, responsible for geomagnetic substorms. The series of two magnetic microsubstorms, with a sudden initial pulse and an insignificant delay relative to the facility switching, was observed at 1840–2000 UT. A disturbance was registered at many stations in the Northern Hemisphere as a global event. The equivalent ionospheric current system of an initial pulse was similar to such a system of the westward auroral surge and had an intensity maximum at Karpogory magnetic observatory, which is the closest station to the Sura facility. Under the conditions of a quiet solar wind and low planetary geomagnetic activity, the AE auroral index correlated with the interplanetary medium parameters (the correlation coefficient reached 0.65) at 1710–2000 UT. It has been confirmed that an initial geomagnetic pulse is generated as a result of radiowave injection. The arguments for and against the generation of microsubstorms due to stimulated precipitation of magnetospheric electrons, as well as the assumption that the geoeffective impact of the interplanetary medium is intensified during the injection of high-power radiowaves near the zone where the westward branch of the current wedge of magnetospheric substorms is generated, are considered.

Dynamics of Solar Activity and Anomalous Weather in Summer 2010: 1. Sector Boundaries: Anticyclone Formation and Destruction

A close synoptic relationship has been found, on the one hand, between the sector structure of the solar and interplanetary magnetic fields and, on the other hand, the structure of tropospheric parameters (the near-Earth pressure and temperature) in Central Russia during an anomalously hot anticyclonic weather in June–August 2010. It has been stated that the Earth crossed the magnetic sector boundaries in full agreement with the boundaries of meteorological parameters, structuring the formation, stabilization, and decay dynamics of anticyclones according to observations performed at IZMIRAN (Troitsk, φ = 55°, λ = 37°).

MHD nature of the origination, dynamics, geoeffectiveness, and disappearance of the four-sector structure of the solar magnetic field during the cycle 23 decline phase

The MHD nature of the origination, dynamics, geoeffectiveness, and disappearance of the four-sector structure of the solar magnetic field during the cycle 23 decline phase has been established. A prolonged ordered MHD process including the chain of the interrelated phenomena (unknown before this study), which begin and end in one of the main zones of active longitudes and are responsible for the above nature of the four-sector structure, has been detected as a result of the simulation of the large-scale open solar magnetic field and an analysis of the dynamics of this field fluxes. These phenomena are as follows: the extreme concentration of the photospheric field sources of the same sign in the zone of active longitudes; blocking of regular differential rotation by these sources; origination of a nonstationary MHD disturbance in the form of a four-sector structure, traveling in the direction of solar rotation at a nearly Alfvén velocity; upset of blocking, displacement of blocking sources from the zone, and their shearing motion relative to a traveling MHD disturbance; deceleration and dissipation of a four-sector MHD disturbance; and reconstruction of a bisector structure. The interactions during this process, which lasted from May 2004 to December 2005, were accompanied by the generation of an ordered succession of heliospheric and solar-terrestrial disturbances including the series of nine extrastorms that were observed from July 2004 to September 2005 and were the last storms in the finished cycle 23 of solar activity.

Correlation between tropical cyclones and magnetic storms during cycle 23 of solar activity

The correlation between cyclic (11-year) variations in geomagnetic activity and tropical cyclogenesis during the completed solar activity cycle (cycle 23, 1996–2006) is studied. The total number of the semidiurnal intervals, with the mean values of the planetary ap index not less than 40, for each year and the annual number of cyclones, regardless of their intensity, are used as the characteristics. The correlation coefficients r are calculated for each of the following four cyclogenesis regions: the Atlantic, northeastern and central Pacific, northwestern Pacific, and water areas of oceans and seas in the Southern Hemisphere. The conclusion that the correlation exists between magnetic storms and tropical cyclones in the Atlantic, obtained earlier by Ivanov [2006] on the basis of the data for 1996–2005, is confirmed. It has been found that the linear correlation coefficient r changed in different regions from positive to negative values: 0.55, 0, −0.50, and −0.50, respectively.

Solar-terrestrial storm of November 18–20, 2003. 1. Near-Earth disturbances in the solar wind

The structure, configuration, dynamics, and solar sources of the near-Earth MHD disturbance of the solar wind on November 20, 2003, is considered. The disturbances of October 24 and November 22 after flares from the same AR 10484 (10501) are compared. The velocity field in the leading part of the sporadic disturbance is for the first time studied in the coordinate system stationary relative to the bow shock. A possible scenario of the physical processes in the course of this solar-terrestrial storm is discussed in comparison with the previously developed scenario for the storm of July 15, 2000. It has been indicated that (1) the near-Earth disturbance was observed at the sector boundary (HCS) and in its vicinities and (2) the disturbance MHD structure included: the complicated bow shock, wide boundary layer with reconnecting fields at a transition from the shock to the magnetic cloud, magnetic cloud with a magnetic cavity including packed substance of an active filament, and return shock layer (supposedly). It has been found out that the shock front configuration and the velocity field are reproduced at an identical position of AR and HCS relative to the Earth on November 20 and 24. It has been indicated that the maximal magnetic induction in the cloud satisfied the condition Bm = (8πn1mp)1/2(D − NV1), i.e., depended on the dynamic impact on the cloud during all three storms [Ivanov et al., 1974]. When the disturbance was related to solar sources, the attention has been paid to the parallelism of the axes of symmetry of the active filament, transient coronal hole, coronal mass ejection, zero line of the open coronal field (HCS), and the axis of the near-Earth magnetic cloud: the regularity previously established in the scenario of the storm of July 15, 2000 [Ivanov et al., 2005]. It has been indicated that the extremely large Bm value in the cloud of October 20 was caused by a strong suppression of the series of postflare shocks reflected from the heliospheric streamer.

Intersector disbalance of the large-scale open solar magnetic field fluxes, active and passive boundaries, and solar-terrestrial extrastorms

The dynamics (from rotation to rotation) of the absolute values of the large-scale open solar magnetic field fluxes in the four-sector field structure has been considered for the first time, using CRs 2032–2035 in July–October 2005 as examples. An important role of the ratio of the fluxes at the eastern and western sector boundaries (ΦE/ΦW) is confirmed. As in the cases of the two-sector structure, ΦE/ΦW > 1 is typical of active rigidly corotating boundaries with intense sunspot formation, flares, and interplanetary and geomagnetic disturbances. A remarkable property of the considered structure was the presence of a rapidly increasing flux in an initially narrow sector and the flux interaction with a stable rigidly corotating sector in the zone of the main active longitudes, which caused an unexpectedly strong geoeffective long-range action of flares near the corresponding active boundary.

Solar-terrestrial extrastorm of August 22–25, 2005. I. Solar sources

The solar-terrestrial extrastorm of August 22–25, 2005, has been considered in the context of the cyclic dynamics and structure of the large-scale open solar magnetic field and has been rated among the other extrastorms of cycle 23. It has been established that the storm under discussion was one of the last six extrastorms in the cycle that occurred during the specific third interval of the declining phase—the period of quasirigidly corotating four-sector structure. Inside this structure, we have revealed convergent motions of the photospheric sources of open fields, the active sector boundary, and the formation of a narrow longitudinal sector with the activity complex responsible for the set of four extrastorms of January–September 2005. It is shown that all extrastorms were accompanied by significant variations (up to 1021 μs) of the open field flux Φ. The storm of August 22–25 was accompanied by an increase in the magnetic flux Φ in the corresponding sector (with a doublet of solar flares) and a fast expansion of the sector to the dimensions at the beginning of this interval (September 2004).

Sector Spherical Harmonic Analysis of the Solar Magnetic Field

The theory of sector harmonic analysis has been developed as applied to the specific conditions of the solar magnetic field. A computer program has been developed. The possibilities of the program are illustrated in an analysis of a large-scale open solar field “singularity” observed on August 11, 2004, using MDI magnetometer data.