E. Romashets - Academia.edu (original) (raw)

Papers by E. Romashets

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

Geomagnetism and Aeronomy, 2006

Research paper thumbnail of January 5-12, 1997 Heliospheric Substorm: Morphology and Interpretation

The solar sources, dynamics, MHD-structure and geometry of the January, 9-12 1997 near-Earth inte... more The solar sources, dynamics, MHD-structure and geometry of the January, 9-12 1997 near-Earth interplanetary disturbances were con sidered in the lights of SOHO, WIND, and INTERBALL plasma and IMF data. The solar magnetic field data (T.Hoeksema, Internet) and preliminary analises of the disturbances given by D.F.Webb and L.F.Burlaga (Internet) were taken into account. The brief summary of our findings is here outlined. The solar sources. The two coronal mass ejections (filament- associated) and the heliospheric current sheet (HCS) were strongly involved into a scenario of the event. Dynamics. It was a typical (as in Ivanov et al., 1995, Solar Wind Eight, p.575) heliospheric substorm (HS) with three- phase IMF and plasma dynamics. The onset of the growth phase of the HS at 1 AU was on Jan. 9 at 0930 UT, long before the forward shock wave arrival to the WIND location. MHD-structure. Preliminary, at least seven specific bounda- ries were identified. Some of them were shock waves and rot...

Research paper thumbnail of Heliospheric current sheet effect on propagation of type II interplanetary radio bursts from coronal mass ejections

Research paper thumbnail of New Force-Free Models of Magnetic Clouds

Highlights of Astronomy, 2005

Research paper thumbnail of Toroidal linear force-free magnetic fields with axial symmetry

Astronomy & Astrophysics, 2016

Research paper thumbnail of Propagation of a Toroidal Magnetic Cloud through the Inner Heliosphere

AIP Conference Proceedings, 2003

Research paper thumbnail of Interaction Of Magnetic Clouds In The Inner Heliosphere

AIP Conference Proceedings, 2003

Research paper thumbnail of Comparative study of a constant-alpha force-free field and its approximations in an ideal toroid

Astronomy & Astrophysics, 2015

ABSTRACT Aims. Magnetic clouds in the solar wind are large loop-like interplanetary flux ropes an... more ABSTRACT Aims. Magnetic clouds in the solar wind are large loop-like interplanetary flux ropes and may be locally approximated by a toroidal flux rope. We compare approximate constant-alpha force-free fields in an ideal toroid, used in magnetic cloud analysis, with the exact solution and examine their validity for low aspect ratios, which may be found in magnetic clouds. The approximate toroidal solutions were originally derived under assumption of large aspect ratios. Methods. Three analytic simple approximate constant-alpha force-free solutions and the exact analytic solution are compared with respect to magnetic field profiles, magnetic field magnitude distributions, and magnetic helicity, with moderate (2–3) and very low (< 2) aspect ratios. Results. The Miller & Turner (1981) field and its modification (to satisfy exact solenoidality) match the position of the magnetic axis in the toroidal flux rope well even for very low aspect ratios. The same can be said for the modified field and the position of the magnetic field maximum. When calculating helicity of the toroidal flux rope, the Miller & Turner field yields better results. A simple formula for magnetic helicity derived from the Miller & Turner solution is valid with a good accuracy even for very low aspect ratios. Conclusions. The Miller & Turner solution is a reasonable substitute for the exact solution even for low aspect ratios (≈ 2).

Research paper thumbnail of Modeling of Magnetic Field Disturbances in Sheath Region of Interplanetary Magnetic Clouds of Elliptical Shapes

Research paper thumbnail of Magnetic Field Configuration Around Large Flux Ropes

Proceedings of the International Astronomical Union, 2004

Research paper thumbnail of Toroidal flux ropes

Proceedings of the International Astronomical Union, 2004

Research paper thumbnail of Modeling of magnetic cloud expansion

Astronomy & Astrophysics, 2015

ABSTRACT A model of an expanding elliptic cylindrical force-free flux rope is used to interpret i... more ABSTRACT A model of an expanding elliptic cylindrical force-free flux rope is used to interpret in-situ magnetic cloud observations by spacecraft. Input quantities are measurements of magnetic field components and velocity magnitudes along a spacecraft trajectory inside a magnetic cloud. During the fitting procedure flux-rope geometric parameters and cloud expansion velocity are determined. Observed separate velocity components are not used in the fitting procedure, but in radial (expansion) velocity construction which is compared to model one to test our model more strictly. 24 magnetic clouds with clearly expressed expansion were fitted by the model. Radial velocity profiles qualitatively correspond to model ones in majority of cases (83%), in more than half of them (58%) quantitatively.

Research paper thumbnail of Solar and heliospheric origins of geomagnetic perturbations in the rising phase of Solar Cycle 23

Research paper thumbnail of Modeling of IMF draping around a supersonic magnetic cloud

Research paper thumbnail of Heliospheric Substorm of November 26–December 5, 1977: 2. Disturbances in the Magnetosheath and Outer Magnetosphere

Geomagnetism and Aeronomy

Research paper thumbnail of The Wave Vectors of Nonlinear Alfvén Waves at the Growth Phase of a Flare–Filament–Streamer Flow of Interplanetary Magnetoplasma

Geomagnetism and Aeronomy

Research paper thumbnail of Dynamics of magnetic cloud of arbitrary shape in the solar wind

Research paper thumbnail of Field draping around an interplanetary magnetic cloud with a shock wave

Geomagnetism and Aeronomy

It is known that interplanetary magnetic clouds can cause strong geomagnetic storms, because they... more It is known that interplanetary magnetic clouds can cause strong geomagnetic storms, because they usually contain a rather large and lasting negative Bz field component. At the same time, magnetic clouds, being isolated formations, perturb the external field. In perturbed external field, a considerable southern component, which is capable of initiating a geomagnetic storm, can also be generated. Therefore, an analysis, of draping of interplanetary magnetic field is very important for an estimate of geoefficiency of the clouds. It should be noted that the effect is especially pronounced in the case of a fast cloud, i.e., when a bow shock is formed in front of the cloud. The pattern becomes asymmetric, and the most perturbed area is located in front of the cloud, behind the shock front. Analytical description of the phenomenon, using the method of potentials in cylindrical geometry, is presented.

Research paper thumbnail of Dynamics of open solar magnetic fields, active longitudes, and near earth disturbances

Open magnetic field lines in the solar corona are calculated in order to study their relationship... more Open magnetic field lines in the solar corona are calculated in order to study their relationship to solar activity and near Earth disturbances in 2000. Slow, rotation by rotation, dynamics of photospheric regions with open fields show a correlation with generating and decay of active complexes located at longitudes 280-360 degrees, and with the series of the near Earth recurrent extra storms on May 24, July 15, August 12, and October 5.

Research paper thumbnail of Modeling magnetic fields around magnetic clouds of different geometries

In-situ observations show that the maximum strength of the magnetic field draping around a magnet... more In-situ observations show that the maximum strength of the magnetic field draping around a magnetic cloud is of the order of the field inside the cloud. We investigate theoretically how this strength depends on geometrical parameters of magnetically closed bodies like cylinders, spheroids, or toroids. These bodies are inserted into an intially homogeneous ambient magnetic field and then a distortion of the external field is calculated under the assumption that the normal field component vanishes at the boundary of the body. If the external field is supposed to be potential, then the maximum increase in the magnetic field magnitude is around 2 times. Non-potential fields yield larger maxima and such increases may explain a trigger of a strong geomagnetic storm only by the Bz component of the draped field, even if there is no strong Bz component inside the cloud.

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

Geomagnetism and Aeronomy, 2006

Research paper thumbnail of January 5-12, 1997 Heliospheric Substorm: Morphology and Interpretation

The solar sources, dynamics, MHD-structure and geometry of the January, 9-12 1997 near-Earth inte... more The solar sources, dynamics, MHD-structure and geometry of the January, 9-12 1997 near-Earth interplanetary disturbances were con sidered in the lights of SOHO, WIND, and INTERBALL plasma and IMF data. The solar magnetic field data (T.Hoeksema, Internet) and preliminary analises of the disturbances given by D.F.Webb and L.F.Burlaga (Internet) were taken into account. The brief summary of our findings is here outlined. The solar sources. The two coronal mass ejections (filament- associated) and the heliospheric current sheet (HCS) were strongly involved into a scenario of the event. Dynamics. It was a typical (as in Ivanov et al., 1995, Solar Wind Eight, p.575) heliospheric substorm (HS) with three- phase IMF and plasma dynamics. The onset of the growth phase of the HS at 1 AU was on Jan. 9 at 0930 UT, long before the forward shock wave arrival to the WIND location. MHD-structure. Preliminary, at least seven specific bounda- ries were identified. Some of them were shock waves and rot...

Research paper thumbnail of Heliospheric current sheet effect on propagation of type II interplanetary radio bursts from coronal mass ejections

Research paper thumbnail of New Force-Free Models of Magnetic Clouds

Highlights of Astronomy, 2005

Research paper thumbnail of Toroidal linear force-free magnetic fields with axial symmetry

Astronomy & Astrophysics, 2016

Research paper thumbnail of Propagation of a Toroidal Magnetic Cloud through the Inner Heliosphere

AIP Conference Proceedings, 2003

Research paper thumbnail of Interaction Of Magnetic Clouds In The Inner Heliosphere

AIP Conference Proceedings, 2003

Research paper thumbnail of Comparative study of a constant-alpha force-free field and its approximations in an ideal toroid

Astronomy & Astrophysics, 2015

ABSTRACT Aims. Magnetic clouds in the solar wind are large loop-like interplanetary flux ropes an... more ABSTRACT Aims. Magnetic clouds in the solar wind are large loop-like interplanetary flux ropes and may be locally approximated by a toroidal flux rope. We compare approximate constant-alpha force-free fields in an ideal toroid, used in magnetic cloud analysis, with the exact solution and examine their validity for low aspect ratios, which may be found in magnetic clouds. The approximate toroidal solutions were originally derived under assumption of large aspect ratios. Methods. Three analytic simple approximate constant-alpha force-free solutions and the exact analytic solution are compared with respect to magnetic field profiles, magnetic field magnitude distributions, and magnetic helicity, with moderate (2–3) and very low (< 2) aspect ratios. Results. The Miller & Turner (1981) field and its modification (to satisfy exact solenoidality) match the position of the magnetic axis in the toroidal flux rope well even for very low aspect ratios. The same can be said for the modified field and the position of the magnetic field maximum. When calculating helicity of the toroidal flux rope, the Miller & Turner field yields better results. A simple formula for magnetic helicity derived from the Miller & Turner solution is valid with a good accuracy even for very low aspect ratios. Conclusions. The Miller & Turner solution is a reasonable substitute for the exact solution even for low aspect ratios (≈ 2).

Research paper thumbnail of Modeling of Magnetic Field Disturbances in Sheath Region of Interplanetary Magnetic Clouds of Elliptical Shapes

Research paper thumbnail of Magnetic Field Configuration Around Large Flux Ropes

Proceedings of the International Astronomical Union, 2004

Research paper thumbnail of Toroidal flux ropes

Proceedings of the International Astronomical Union, 2004

Research paper thumbnail of Modeling of magnetic cloud expansion

Astronomy & Astrophysics, 2015

ABSTRACT A model of an expanding elliptic cylindrical force-free flux rope is used to interpret i... more ABSTRACT A model of an expanding elliptic cylindrical force-free flux rope is used to interpret in-situ magnetic cloud observations by spacecraft. Input quantities are measurements of magnetic field components and velocity magnitudes along a spacecraft trajectory inside a magnetic cloud. During the fitting procedure flux-rope geometric parameters and cloud expansion velocity are determined. Observed separate velocity components are not used in the fitting procedure, but in radial (expansion) velocity construction which is compared to model one to test our model more strictly. 24 magnetic clouds with clearly expressed expansion were fitted by the model. Radial velocity profiles qualitatively correspond to model ones in majority of cases (83%), in more than half of them (58%) quantitatively.

Research paper thumbnail of Solar and heliospheric origins of geomagnetic perturbations in the rising phase of Solar Cycle 23

Research paper thumbnail of Modeling of IMF draping around a supersonic magnetic cloud

Research paper thumbnail of Heliospheric Substorm of November 26–December 5, 1977: 2. Disturbances in the Magnetosheath and Outer Magnetosphere

Geomagnetism and Aeronomy

Research paper thumbnail of The Wave Vectors of Nonlinear Alfvén Waves at the Growth Phase of a Flare–Filament–Streamer Flow of Interplanetary Magnetoplasma

Geomagnetism and Aeronomy

Research paper thumbnail of Dynamics of magnetic cloud of arbitrary shape in the solar wind

Research paper thumbnail of Field draping around an interplanetary magnetic cloud with a shock wave

Geomagnetism and Aeronomy

It is known that interplanetary magnetic clouds can cause strong geomagnetic storms, because they... more It is known that interplanetary magnetic clouds can cause strong geomagnetic storms, because they usually contain a rather large and lasting negative Bz field component. At the same time, magnetic clouds, being isolated formations, perturb the external field. In perturbed external field, a considerable southern component, which is capable of initiating a geomagnetic storm, can also be generated. Therefore, an analysis, of draping of interplanetary magnetic field is very important for an estimate of geoefficiency of the clouds. It should be noted that the effect is especially pronounced in the case of a fast cloud, i.e., when a bow shock is formed in front of the cloud. The pattern becomes asymmetric, and the most perturbed area is located in front of the cloud, behind the shock front. Analytical description of the phenomenon, using the method of potentials in cylindrical geometry, is presented.

Research paper thumbnail of Dynamics of open solar magnetic fields, active longitudes, and near earth disturbances

Open magnetic field lines in the solar corona are calculated in order to study their relationship... more Open magnetic field lines in the solar corona are calculated in order to study their relationship to solar activity and near Earth disturbances in 2000. Slow, rotation by rotation, dynamics of photospheric regions with open fields show a correlation with generating and decay of active complexes located at longitudes 280-360 degrees, and with the series of the near Earth recurrent extra storms on May 24, July 15, August 12, and October 5.

Research paper thumbnail of Modeling magnetic fields around magnetic clouds of different geometries

In-situ observations show that the maximum strength of the magnetic field draping around a magnet... more In-situ observations show that the maximum strength of the magnetic field draping around a magnetic cloud is of the order of the field inside the cloud. We investigate theoretically how this strength depends on geometrical parameters of magnetically closed bodies like cylinders, spheroids, or toroids. These bodies are inserted into an intially homogeneous ambient magnetic field and then a distortion of the external field is calculated under the assumption that the normal field component vanishes at the boundary of the body. If the external field is supposed to be potential, then the maximum increase in the magnetic field magnitude is around 2 times. Non-potential fields yield larger maxima and such increases may explain a trigger of a strong geomagnetic storm only by the Bz component of the draped field, even if there is no strong Bz component inside the cloud.