scholarly journals The behaviour of the cosmic-ray equatorial anisotropy inside fast solar-wind streams ejected by coronal holes

1983 ◽  
Vol 6 (5) ◽  
pp. 566-566
Author(s):  
N. Iucci ◽  
M. Parisi ◽  
M. Storini ◽  
G. Villoresi
Keyword(s):  
Solar Wind ◽  
Coronal Holes ◽  
Cosmic Ray ◽  
Fast Solar Wind

The behaviour of the cosmic-ray equatorial anisotropy inside fast solar-wind streams ejected by coronal holes

1983 ◽  
Vol 6 (2) ◽  
pp. 145-158 ◽  
Author(s):  
N. Iucci ◽  
M. Parisi ◽  
M. Storini ◽  
G. Villoresi
Keyword(s):  
Solar Wind ◽  
Coronal Holes ◽  
Cosmic Ray ◽  
Fast Solar Wind

Solar wind temperature–velocity relationship over the last five solar cycles and Forbush decreases associated with different types of interplanetary disturbance

2020 ◽  
Vol 500 (3) ◽  
pp. 2786-2797
Author(s):  
A A Melkumyan ◽  
A V Belov ◽  
M A Abunina ◽  
A A Abunin ◽  
E A Eroshenko ◽  
...  
Keyword(s):  
Solar Wind ◽  
High Speed ◽  
Coronal Holes ◽  
Cosmic Ray ◽  
Magnetic Clouds ◽  
Solar Cycles ◽  
Forbush Decreases ◽  
Proton Temperature ◽  
Interaction Regions ◽  
Interplanetary Disturbance

ABSTRACT The behaviour of the solar wind (SW) proton temperature and velocity and their relationship during Forbush decreases (FDs) associated with various types of solar source – coronal mass ejections (CMEs) and coronal holes (CHs) – have been studied. Analysis of cosmic ray variations, SW temperature, velocity, density, plasma beta, and magnetic field (from 1965–2019) is carried out using three databases: the OMNI database, Variations of Cosmic Rays database (IZMIRAN) and Forbush Effects & Interplanetary Disturbances database (IZMIRAN). Comparison of the observed SW temperature (T) and velocity (V) for the undisturbed SW allows us to derive a formula for the expected SW temperature (Texp, the temperature given by a T–V formula, if V is the observed SW speed). The results reveal a power-law T–V dependence with a steeper slope for low speeds (V < 425 km s−1, exponent = 3.29 ± 0.02) and flatter slope for high speeds (V > 425 km s−1, exponent = 2.25 ± 0.02). A study of changes in the T–V dependence over the last five solar cycles finds that this dependence varies with solar activity. The calculated temperature index KT = T/Texp can be used as an indicator of interplanetary and solar sources of FDs. It usually has abnormally large values in interaction regions of different-speed SW streams and abnormally low values inside magnetic clouds (MCs). The results obtained help us to identify the different kinds of interplanetary disturbance: interplanetary CMEs, sheaths, MCs, corotating interaction regions, high-speed streams from CHs, and mixed events.

scholarly journals Cosmic Ray Signatures of Different Types of Solar Wind Streams

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).

scholarly journals Polar magnetic fields and coronal holes during the recent solar minima

2011 ◽  
Vol 7 (S286) ◽  
pp. 101-112 ◽  
Author(s):  
Giuliana de Toma
Keyword(s):  
Solar Wind ◽  
Magnetic Fields ◽  
Coronal Holes ◽  
Magnetic Activity ◽  
Fast Solar Wind ◽  
The Earth ◽  
Slow Decline ◽  
Polar Magnetic Fields ◽  
Cycle 24 ◽  
The One

AbstractThe slow decline of solar Cycle 23 combined with the slow rise of Cycle 24 resulted in a very long period of low magnetic activity during the years 2007–2009 with sunspot number reaching the lowest level since 1913. This long solar minimum was characterized by weak polar magnetic fields, smaller polar coronal holes, and a relatively complex coronal morphology with multiple streamers extending to mid latitudes. At the same time, low latitude coronal holes remained present on the Sun until the end of 2008 modulating the solar wind at the Earth in co-rotating, fast solar wind streams. This magnetic configuration was remarkably different from the one observed during the previous two solar minima when coronal streamers were confined near the equator and the fast solar wind was mainly originating from the large coronal holes around the Sun's poles. This paper presents the evolution of the polar magnetic fields and coronal holes during the past minimum, compare it with the previous minima, and discuss the implications for the solar wind near the Earth. It also considers the minimum of Cycle 23 in an historical perspective and, in particular, compares it to the long minima at the turn of the 19th century.

scholarly journals The origin of slow Alfvénic solar wind at solar minimum

2019 ◽  
Vol 492 (1) ◽  
pp. 39-44 ◽  
Author(s):  
D Stansby ◽  
L Matteini ◽  
T S Horbury ◽  
D Perrone ◽  
R D’Amicis ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Alpha Particle ◽  
Coronal Holes ◽  
Slow Solar Wind ◽  
Kinetic Properties ◽  
Fast Solar Wind ◽  
Lower Corona ◽  
Field Lines ◽  
Slow Wind

ABSTRACT Although the origins of slow solar wind are unclear, there is increasing evidence that at least some of it is released in a steady state on overexpanded coronal hole magnetic field lines. This type of slow wind has similar properties to the fast solar wind, including strongly Alfvénic fluctuations. In this study, a combination of proton, alpha particle, and electron measurements are used to investigate the kinetic properties of a single interval of slow Alfvénic wind at 0.35 au. It is shown that this slow Alfvénic interval is characterized by high alpha particle abundances, pronounced alpha–proton differential streaming, strong proton beams, and large alpha-to-proton temperature ratios. These are all features observed consistently in the fast solar wind, adding evidence that at least some Alfvénic slow solar wind also originates in coronal holes. Observed differences between speed, mass flux, and electron temperature between slow Alfvénic and fast winds are explained by differing magnetic field geometry in the lower corona.

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