Variations of flow direction in solar wind streams of different types

Studying the direction of the solar wind flow is a topical problem of space weather forecasting. As a rule, the quiet and uniform solar wind propagates radially, but significant changes in the solar wind flow direction can be observed, for example, in compression regions before the interplanetary coronal mass ejections (Sheath) and Corotating Interaction Regions (CIR) that precede high-speed streams from coronal holes. In this study, we perform a statistical analysis of the longitude (φ) and latitude (θ) flow direction angles and their variations on different time scales (30 s and 3600 s) in solar wind large-scale streams of different types, using WIND spacecraft data. We also examine the relationships of the value and standard deviations SD of the flow direction angles with various solar wind parameters, regardless of the solar wind type. We have established that maximum values of longitude and latitude angle modulus, as well as their variations, are observed for Sheath, CIR, and Rare, with the probability of large deviations from the radial direction (>5°) increasing. The dependence on the solar wind type is shown to decrease with scale. We have also found that the probability of large values of SD(θ) and SD(φ) increases with increasing proton temperature (Tp) in the range 5–10 eV and with increasing proton velocity (Vp) in the range 400–500 km/s.

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Statistical analysis of flow direction and its variations in different types of solar wind streams

10.5194/egusphere-egu21-13829 ◽

2021 ◽

Author(s):

Anastasiia Moskaleva ◽

Maria Riazantseva ◽

Yuri Yermolaev ◽

Irina Lodkina

Keyword(s):

Solar Wind ◽

High Speed ◽

Large Scale ◽

Flow Direction ◽

Solar Physics ◽

Coronal Holes ◽

Statistical Distributions ◽

Interplanetary Coronal Mass Ejections ◽

Solar Wind Interaction ◽

Plasma Parameters

The efficiency of the solar wind interaction with the Earth's magnetosphere is determined not only by the values of solar wind parameters, but also by the direction of its flow. &#160;As a rule, the slow quiet and uniform solar wind extends radially, but at the same time there are different large-scale solar wind streams, that differ in the values of the plasma parameters and in the flow direction. The most significant changes of solar wind flow direction can be observed in areas of stream interaction, for example Sheath (compression regions before the fast interplanetary coronal mass ejections) and CIR (corotating interaction regions, that are predate high-speed flows from coronal holes) [1]. In the present study, using plasma measurements on the WIND spacecraft, the statistical distributions of the values and fluctuations of flow direction angles in the solar wind were analyzed.&#160; The angles variations were considered on temporal scales from several ten seconds to an hour. The statistical distributions in the quiet solar wind and in various large-scale solar wind streams using the catalog of large-scale solar wind phenomena from the ftp://ftp.iki.rssi.ru/pub/omni/catalog were compared [2].At the result of this work, it was shown , that maximum values of modules longitude (&#966;) and latitude (&#952;) angles, and of their variations are observed for Sheath and CIR regions, the probability of large deviations from the radial direction (>5 degrees)&#160; also increases. Meanwhile the dependence on the solar wind type reduces with decreasing scale. The relation of the values and fluctuations of the direction angles on the values of the plasma parameters in the solar wind were also analyzed. The work was supported by the RFBR, grant &#8470; 19-02-00177&#1072;.1.Yermolaev Y. I., Lodkina I. G., Nikolaeva N. S., Yermolaev M. Y. 2017, Solar Physics, 292 (12),193, https://doi.org/10.1007/s11207-017-1205-1 2. Yermolaev, Yu.I., Nikolaeva, N.S., Lodkina, I.G., Yermolaev, M.Yu.: 2009, Catalog of large-scale solar wind phenomena during 1976 &#8211; 2000. Cosm. Res. 47(2),81;Eng.transl.Kosm.Issled.47(2),99, https://doi.org/10.1134/S0010952509020014

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Interplanetary Response to Solar Long Time-Scale Phenomena

Symposium - International Astronomical Union ◽

10.1017/s0074180900067413 ◽

1980 ◽

Vol 91 ◽

pp. 105-125

Author(s):

C. D'Uston ◽

J. M. Bosqued

Keyword(s):

Solar Wind ◽

Time Scale ◽

High Speed ◽

Coronal Holes ◽

Observational Evidence ◽

Solar Wind Flow ◽

Speed Solar Wind ◽

Long Time ◽

Outer Corona ◽

High Speed Solar Wind

In this paper, we briefly review the experimental knowledge gained in the recent years on the interplanetary response to solar long-time scale phenomena such as the coronal magnetic structure and its evolution. Observational evidence that solar wind flow in the outer corona comes from the unipolar diverging magnetic regions of the photosphere is discussed along with relations to coronal holes. High-speed solar wind streams observed within the boundary of interplanetary magnetic sectors are associated with these structures. Their boundaries appear as very narrow velocity shears.

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Cosmic Ray Signatures of Different Types of Solar Wind Streams

Symposium - International Astronomical Union ◽

10.1017/s0074180900088070 ◽

1990 ◽

Vol 142 ◽

pp. 259-260

Author(s):

P.K. Shrivastava ◽

S.P. Agrawal

Keyword(s):

Solar Wind ◽

High Speed ◽

Solar Wind Speed ◽

Coronal Holes ◽

Cosmic Ray ◽

Cosmic Ray Intensity ◽

Wind Speeds ◽

Different Types ◽

Speed Solar Wind ◽

High Speed Solar Wind

The earlier concept of average solar wind speed has changed with time. Besides quiet periods of low/average solar wind speeds, two different kinds of solar sources (solar flares and coronal holes) have been identified to produce high speed solar wind streams. In an earlier investigation, it was reported that the high speed streams associated to these sources produce distinctly different effects on the cosmic ray intensity (Venkatesan, et. al., 1982).

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Mesoscale Structure in the Solar Wind

Frontiers in Astronomy and Space Sciences ◽

10.3389/fspas.2021.735034 ◽

2021 ◽

Vol 8 ◽

Author(s):

N. M. Viall ◽

C. E. DeForest ◽

L. Kepko

Keyword(s):

Solar Wind ◽

High Speed ◽

Large Scale ◽

Coronal Holes ◽

Solar Wind Plasma ◽

Research Progress ◽

The Sun ◽

Remote Imaging ◽

Mesoscale Structures ◽

Kinetic Effects

Structures in the solar wind result from two basic mechanisms: structures injected or imposed directly by the Sun, and structures formed through processing en route as the solar wind advects outward and fills the heliosphere. On the largest scales, solar structures directly impose heliospheric structures, such as coronal holes imposing high speed streams of solar wind. Transient solar processes can inject large-scale structure directly into the heliosphere as well, such as coronal mass ejections. At the smallest, kinetic scales, the solar wind plasma continually evolves, converting energy into heat, and all structure at these scales is formed en route. “Mesoscale” structures, with scales at 1 AU in the approximate spatial range of 5–10,000 Mm and temporal range of 10 s–7 h, lie in the orders of magnitude gap between the two size-scale extremes. Structures of this size regime are created through both mechanisms. Competition between the imposed and injected structures with turbulent and other evolution leads to complex structuring and dynamics. The goal is to understand this interplay and to determine which type of mesoscale structures dominate the solar wind under which conditions. However, the mesoscale regime is also the region of observation space that is grossly under-sampled. The sparse in situ measurements that currently exist are only able to measure individual instances of discrete structures, and are not capable of following their evolution or spatial extent. Remote imaging has captured global and large scale features and their evolution, but does not yet have the sensitivity to measure most mesoscale structures and their evolution. Similarly, simulations cannot model the global system while simultaneously resolving kinetic effects. It is important to understand the source and evolution of solar wind mesoscale structures because they contain information on how the Sun forms the solar wind, and constrains the physics of turbulent processes. Mesoscale structures also comprise the ground state of space weather, continually buffeting planetary magnetospheres. In this paper we describe the current understanding of the formation and evolution mechanisms of mesoscale structures in the solar wind, their characteristics, implications, and future steps for research progress on this topic.

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Highlight Results from Ulysses

Symposium - International Astronomical Union ◽

10.1017/s0074180900219931 ◽

2001 ◽

Vol 203 ◽

pp. 525-532

Author(s):

R. G. Marsden

Keyword(s):

Solar Wind ◽

Solar Minimum ◽

High Speed ◽

Full Range ◽

Coronal Holes ◽

Radial Component ◽

Slow Solar Wind ◽

Solar Wind Flow ◽

Low Energy Ions ◽

Inner Heliosphere

Launched in October 1990, the ESA-NASA Ulysses mission has conducted the very first survey of the heliosphere within 5 AU of the Sun over the full range of heliolatitudes. The first polar passes took place in 1994 and 1995, enabling Ulysses to characterise the global structure of the heliosphere at solar minimum, when the corona adopts its simplest configuration. The most important findings to date include a confirmation of the uniform nature of the high-speed (~ 750 km s−1) solar wind flow from the polar coronal holes, filling two-thirds of the volume of the inner heliosphere; the sharp boundary, existing from the chromosphere through the corona, between fast and slow solar wind streams; the latitude independence of the radial component of the heliospheric magnetic field; the lower-than-expected latitude gradient of galactic and anomalous cosmic rays; the continued existence of recurrent increases in the flux of low-energy ions and electrons up to the highest latitudes.

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