High-velocity Solar Wind Streams Research Articles

Influence of helio-geophysical activity on reliability of short-wave communication in transport

The results of studies of the influence of coronal mass ejections and high-velocity solar wind streams on the characteristics of the ionosphere are presented. The analysis uses ionospheric data from the CADI vertical sounding station (Vasilsursk, Nizhny Novgorod region) and data from chirp stations for oblique ionospheric sounding on different paths of the Eurasian region of Russia: three subauroral (Lovozero-Vasilsursk, Sodankyulya-Vasilsursk and Salekhard-Vasilsursk) and one mid-latitude (Gorky, Leningrad region-Vasilsursk). A set of space weather parameters (type and speed of coronal mass ejections, high-speed solar wind speed) is considered, which made it possible to reveal the dominant physical relationships between the ionospheric dynamics and these two solar phenomena, which determine the reliability of short-wave radio communication between ships and the coast, especially in the area of the northern sea way.

Precipitation of energetic magnetospheric electrons and accompanying solar wind characteristics

From 1957 up to the present time, the Lebedev Physical Institute (LPI) has performed regular monitoring of ionizing radiation in the Earth’s atmosphere. There are cases when the X-ray radiation generated by energetic magnetospheric electrons penetrates the atmosphere and is observed at polar latitudes. The vast majority of these events occurs against the background of high-velocity solar wind streams, while magnetospheric perturbations related to interplanetary coronal mass ejections (ICMEs) are noneffective for precipitation. It is shown in the paper that ICMEs do not cause acceleration of a sufficient amount of electrons in the magnetosphere. Favorable conditions for acceleration and subsequent scattering of electrons into the loss cone are created by magnetic storms with an extended recovery phase and with sufficiently frequent periods of negative Bz component of the interplanetary magnetic field (IMF). Such geomagnetic perturbations are typical for storms associated with high-velocity solar wind streams.

Precipitation of magnetospheric electrons into the Earth’s atmosphere and the electrons of the outer radiation belt

More than 500 X-ray emission events generated by precipitating electrons from the outer radiation belt have been recorded in the Earth’s atmosphere over the many years of the Lebedev Physical Institute observing fluxes of ionized radiation. This precipitation is closely related to high-velocity solar wind streams, whose rate of occurrence, like that of precipitation events, is greatest during the decline phase of the 11-year solar activity cycle. This work considers the relationship between the high-velocity solar wind, the relativistic electron fluxes in the outer radiation belt, and the electron precipitation observed in the polar atmosphere.

Variations in the ULF index of daytime geomagnetic pulsations during recurrent magnetic storms

A new index of wave activity (ULF index) is applied to analyze daytime magnetic pulsations in the Pc5 range (f = 2–7 mHz) during ten successive recurrent magnetic storms (CIR (corotating interaction region) storms) of 2006. The most intense daytime geomagnetic Pc5 pulsations on the Earth’s surface in all phases of CIR storms are predominantly observed in the pre-noon sector at latitudes higher than 70°, while those in CME storms (storms initiated by coronal mass ejection (CME)) are observed at latitudes lower than 70°. A comparison of wave activity during CIR and CME storms has shown that the amplitude of Pc5 pulsations in CIR storms is much smaller than that in CME storms and the spectrum maximum is observed at lower frequencies and higher latitudes. At the same time, the mechanism of ULF wave generation during both types of magnetic storms seems to be similar, namely, resonance of magnetic field lines due to the development of the Kelvin-Helmholtz instability caused by an approach of a high-velocity solar wind stream to the Earth’s magnetosphere. Since resonance oscillations are excited only in the closed magnetosphere, the higher-latitude position of the Pc5 pulsation intensity maximum in CIR storms points to larger dimensions of the daytime magnetosphere during CIR storms as compared to CME storms.

Pc3 pulsations during variable IMF conditions

Abstract. Pc3 geomagnetic field fluctuations detected at low latitude (L'Aquila, Italy) during the passage of a high velocity solar wind stream, characterized by variable interplanetary magnetic field conditions, are analyzed. Higher frequency resonant fluctuations and lower frequency phenomena are simultaneously observed; the intermittent appearance and the variable frequency of the longer period modes can be well interpreted in terms of the variable IMF elements; moreover their polarization characteristics are consistent with an origin related to external waves propagating in antisunward direction. A comparison with simultaneous observations performed at Terra Nova Bay (Antarctica) provides additional evidence for a clear relationship between the IMF and Pc3 pulsations also at very high latitudes.Key words. Magnetospheric physics (MHD waves and instabilities; solar wind · magnetosphere interactions)

Pc3 pulsations during variable IMF conditions

Pc3 geomagnetic field fluctuations detected at low latitude (L'Aquila, Italy) during the passage of a high velocity solar wind stream, characterized by variable interplanetary magnetic field conditions, are analyzed. Higher frequency resonant fluctuations and lower frequency phenomena are simultaneously observed; the intermittent appearance and the variable frequency of the longer period modes can be well interpreted in terms of the variable IMF elements; moreover their polarization characteristics are consistent with an origin related to external waves propagating in antisunward direction. A comparison with simultaneous observations performed at Terra Nova Bay (Antarctica) provides additional evidence for a clear relationship between the IMF and Pc3 pulsations also at very high latitudes.Key words. Magnetospheric physics (MHD waves and instabilities; solar wind · magnetosphere interactions)

Amplitude modulation of the equatorial electrojet (EEJ) during a magnetospheric storm

Abstract An encounter of the Earth with a high velocity solar wind stream triggered the magnetic storm of 29 January 1995. The storm lasted for the following seven days, keeping the level of the Dst index in the range of −25–−50 nT. At the dip-equator, a regular enhancement of the magnetic H component during daytime, referred to as the Equatorial Electrojet (EEJ), was seen to be suppressed and modified during this storm interval. We attempted to classify the type of the EEJ modification by analyzing magnetometer data from two stations at the dip-equator but located in the opposite hemisphere, and energetic particle data from two geosynchronous satellites located close to the ground magnetometer meridian. As a result, three different types of modulation of EEJ amplitudes, with time scales of 15 min to 1 day, were found to appear during the periods when the flux level of low energy charged particles (>30 keV) in the midnight magnetosphere was increased above the quiet level. These modulations were characterized by referring to the nightside particle signatures. We argue that, although the EEJ is a local enhancement of the ionospheric currents at the dayside dip-equator, the EEJ is definitely affected by changes of the magnetosphere, probably in various ways arising from the complexities of the storm effects.

Comment on “The solar flare myth” by J. T. Gosling

Journal of Geophysical Research: Space PhysicsVolume 100, Issue A5 p. 7917-7919 Papers on Solar and Heliospheric Physics CommentariesFree Access Comment on “The solar flare myth” by J. T. Gosling M. I. Pudovkin, M. I. PudovkinSearch for more papers by this author M. I. Pudovkin, M. I. PudovkinSearch for more papers by this author First published: 1 May 1995 https://doi.org/10.1029/94JA03033Citations: 7AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. References Akasofu, S.-I., S. Yoshida, The structure of the solar plasma flow generated by solar flares, Planet. Space Sci., 15, 39, 1967. Cane, H. V., The evolution of interplanetary shocks, J. Geophys. Res., 90, 191, 1985. Gold, T., Plasma and magnetic fields in the solar system, J. Geophys. Res., 64, 1665, 1959. Gosling, J. T., The solar flare myth, J. Geophys. Res., 98, 18,937, 1993. Harrison, R. A., E. Hildner, A. J. Hundhausen, D. G. Sime, G. M. Simnett, The launch of solar coronal mass ejection: Results from the coronal mass ejection onset program, J. Geophys. Res., 95, 917, 1990. Ivanov, K. G., N. V. Mikerina, Ground level geomagnetic effects of interplanetary shocks fronts from powerful isolated flares of the nearby zone (in Russian), Geomagn. Aeron., 20, 508– 514, 1980. Ivanov, K. G., N. V. Mikerina, Powerful isolated flares of the near zone and the connection of the magnetic field of bipolar groups with the field of interplanetary flare throws and with geomagnetic disturbances (in Russian), Geomagn. Aeron., 21, 34– 38, 1981. King, J. H., The Interplanetary Medium Data Book, National Space Science Data Center, Greenbelt, Md., 1977. Piddington, J. H., Cosmic electrodynamics, 87, John Willey, New York, 1969. Pudovkin, M. I., A. D. Chertkov, Magnetic field of the solar wind, Sol. Phys., 50, 213– 229, 1976. Pudovkin, M. I., S. A. Zaitseva, I. P. Oleferenko, Magnetic field of the flare stream, in Russian, Izv. Acad. Nauk SSSR Ser. phys., 41, 242– 251, 1977. Pudovkin, M. I., S. A. Zaitseva, A. D. Chertkov, E. M. Fomina, The structure and geoefficiency of high velocity solar wind streams, Solar-Terrestrial Predictions Proceedings, , 3 F. Donnelly, B56– 65, U.S. Department of Commerce, Washington, 1980. Sheeley, N. R., R. A. Howard, M. J. Koomen, D. J. Michels, R. Schwenn, K. H. Mühlhäuser, H. Rosenbauer, Coronal mass ejections and interplanetary shocks, J. Geophys. Res., 90, 163, 1985. Citing Literature Volume100, IssueA51 May 1995Pages 7917-7919 ReferencesRelatedInformation

Quasiperiodic Jovian Radio bursts: observations from the Ulysses Radio and Plasma Wave Experiment

The Ulysses flyby of Jupiter has permitted the detection of a variety of quasiperiodic magnetospheric phenomena. In this paper, Unified Radio and Plasma Wave Experiment (URAP) observations of quasiperiodic radio bursts are presented. There appear to be two preferred periods of short-term variability in the Jovian magnetosphere, as indicated by two classes of bursts, one with ∼ 40 min periodicity, the other with ∼ 15 min periodicity. The URAP radio direction determination capability provides clear evidence that the 40 min bursts originate near the southern Jovian magnetic pole, whereas the source location of the 15 min bursts remains uncertain. These bursts may be the signatures of quasiperiodic electron acceleration in the Jovian magnetosphere; however, only the 40 min bursts occur in association with observed electron bursts of similar periodicity. Both classes of bursts show some evidence of solar wind control. In particular, the onset of enhanced 40 min burst activity is well correlated with the arrival of high-velocity solar wind streams at Jupiter, thereby providing a remote monitor of solar wind conditions at Jupiter.

Relationship between field line resonance at low geomagnetic latitudes and solar wind structures

The link between the pulsation activity in the local resonant band at a low latitude station and the macroscale structure of the interplanetary medium has been investigated. The experimental results show a clear dependence of the amplitude of the local resonant events on the interplanetary magnetic field magnitude and a preferable occurrence in correspondence of the compression regions preceding the high velocity solar wind streams. These features appear consistent with an upstream wave source for these events.

A study of the relationship between micropulsations and solar wind properties

A year‐long comparison between daily averages of solar wind parameters obtained from the Massachusetts Institute of Technology experiment on IMP‐8 and micropulsation measurements made by the Universita dell'Aquila has shown a correlation between solar wind speed and micropulsation power with peaks of the correlation coefficient greater than 0.8 in the period range from 20 to 40 s. Different behavior observed for different period bands suggests that the shorter period activity tends to precede the highest values of the solar wind speed while the longer period activity tends to persist for longer intervals within high velocity solar wind streams. A comparison with simultaneous interplanetary magnetic field measurements supports the upstream origin of the observed ground pulsations.

Long-Term Energy and Momentum Flux Fluctuations of the Solar Wind at 1AU

The paper is concerned with the variations of solar wind kinetic energy, ion thermal energy, ion flux and momentum as observed by near-Earth spacecraft over time scales from seconds to several days. The mean values of these fluxes and characteristics of their variability are discussed. The average variations of kinetic energy and momentum flux are about 10% of the mean values over a one-hour interval. Consideration is given to the differences in the energy and momentum flux for low-velocity and high-velocity solar wind streams. The discussion is extended with an analysis of very intense disturbances of energy and momentum due to the arrival of an interplanetary shock wave at Earth.

A third catalogue of high-speed plasma streams in the solar wind - data for 1978?1982

Interplanetary magnetic field data obtained from near-Earth spacecraft are used to compile a catalogue of high-velocity solar wind streams for the period June 1978 through October 1982 (Bartels rotations 1980–2039). The compilation of high-velocity streams is a continuation of two previous lists which covered the periods 1964–1975 and 1975–1978, respectively. The total number of high-speed solar wind streams listed in the catalogues is 637 of which 520 are corotating streams and 117 are classified as flare-associated streams.

A catalogue of high-speed plasma streams in the solar wind 1975?78

Interplanetary magnetic field data compiled by King (1977, 1979) are used to obtain a list of high velocity solar wind streams for the period January 1975 through June 1978. The catalogue is a continuation of a previous list which covered 1964–75. The total number of high-speed solar wind streams listed in the catalogues is 455.

The radial evolution of the IMF fluctuations: A comparison with theoretical models

We conducted an analysis of the radial evolution of the wave phenomena observed in the inner solar system and associated with the high velocity solar wind stream pattern. The combined interplanetary magnetic field observations performed by Helios-1 and Helios-2 spacecraft allow to draw the following conclusions: (a) The compressive contribution to field fluctuations with periods less than 6 hr is observed to increase with the increasing heliocentric distance and the total variance of the field components decreases appreciably faster than r−3. (b) When compared with theoretical models, Helios observations confirm a better agreement with wave modes which saturate at a constant value of the ratio between the wave energy density and the ambient field energy density.

The flute instability as the trigger mechanism for disruption of cometary plasma tails

The sporadic disruption of the plasma tails of some comets has recently been explained to be caused by magnetic-field-line reconnection in the cometary ionospheres due to magnetic-sector-boundary traversals. An alternative model is proposed in which the tail disruption is the end result of compression of the cometary ionosphere by high-velocity solar-wind streams, triggering the flute instability in the marginally stable tangential-discontinuity surface which separates the cometary ionosphere from the solar-wind plasma. According to the proposed model, the tail-disruption events could occur at all heliographic latitudes, whereas the Niedner-Brandt (1978) model should predict that these events are restricted to low heliographic latitudes in view of the present understanding of the sector structure of the heliosphere. Consequently, the high-latitude disruption events observed seem to present a difficulty for the latter model.

Interplanetary gas. XXII - Interaction of comet Kohoutek's ion tail with the compression region of a solar-wind corotating stream

An apparently successful identification of a comet-tail feature with a solar-wind event is presented. Photographs of comet Kohoutek 1973f show a large-scale disturbance in the middle and outer regions of the ion tail early on January 20 of 1974. On the previous and succeeding days the comet had, however, a 'normal' and less active appearance. The peculiar tail structure is linked to an encounter with rapidly changing solar-wind conditions on the forward edge of the high-velocity solar-wind stream which encountered the earth late on January 24. The stream produced a geomagnetic storm of the recurrent type. The high-speed stream appears to have been associated with a large near-equatorial coronal hole which underwent central meridian passage on January 22. It is proposed that the comet was in the compression region on the stream forward edge at the time of formation of the tail disturbance. The accuracy of the time delays is actually tested by an application of the wind shock theory of ionic tail orientations.

High coronal structure of high velocity solar wind stream sources

When solar wind plasma in the trailing (eastern) edge of a high-speed stream is mapped back to its estimated source in the high corona using the constant radial velocity (EQRH) approximation, a large range of velocities appears to come from a restricted range in longitude, often only a few degrees. This actually constitutes a sharp eastern coronal boundary for the solar wind stream source, and demands that the boundary have a three-dimensional structure. Using interplanetary data, we infer a systematic variation in ‘source altitude’ (identified approximately with the Alfven point), with faster solar wind attaining its interplanetary characteristics at lower altitudes. This also affects the accuracy of the source longitude estimates, so that we infer a width in the high corona of 4–6° for the source of the trailing edges of streams which appear to originate from a single longitude. We demonstrate that the possible systematic interplanetary effects (in at least some cases) are not large (≲ 2° in heliocentric longitude). The relatively sharp boundaries imply that high-speed streams are well-defined structures all the way down to their low coronal sources, and that the magnetic field structure controls the propagation of the plasma through the corona out to the vicinity of the Alfven point (≳ 20 R⊙).

A Discussion on the physics of the solar atmosphere - The x-ray corona from Skylab

An overview of the images obtained with the A.S. & E. X-ray telescope on Skylab shows the low corona to be highly structured. The plasma is distributed in closed loops shaped by the magnetic field with sizes ranging from the smallest resolvable structures of a few thousand kilometres to loops that reach halfway across the solar disk. Relatively high-temperature and dense plasma loops overlay active regions; large-scale interconnections link active regions to their surrounding fields and in some cases to other active regions. The large-scale loops, which cover most of the Sun outside of active regions, appear to be related to old active regions whose magnetic fields have spread out over the course of several solar rotations. Often at the poles and occasionally on the disk, large regions display radial field configurations (coronal holes) from which the plasma preferentially escapes into high-velocity solar wind streams. A comprehensive view of the structure and evolution of the X-ray corona is given in terms of the physical conditions existing in the various coronal loops, and the importance of active regions is emphasized by examining their structure and time development over a wide range of scales.

Coronal holes as sources of solar wind

We investigate the association of high-speed solar wind with coronal holes during the Skylab mission by: (1) direct comparison of solar wind and coronal X-ray data; (2) comparison of near-equatorial coronal hole area with maximum solar wind velocity in the associated streams; and (3) examination of the correlation between solar and interplanetary magnetic polarities. We find that all large near-equatorial coronal holes seen during the Skylab period were associated with high-velocity solar wind streams observed at 1 AU.