scholarly journals Interplanetary scintillation observations of interaction regions in the solar wind

1998 ◽  
Vol 16 (10) ◽  
pp. 1265-1282 ◽  
Author(s):  
A. R. Breen ◽  
P. J. Moran ◽  
C. A. Varley ◽  
W. P. Wilkinson ◽  
P. J. S. Williams ◽  
...  
Keyword(s):  
Solar Wind ◽  
Key Words ◽  
Theoretical Modelling ◽  
The Sun ◽  
Interplanetary Scintillation ◽  
Prominent Feature ◽  
Wind Measurements ◽  
Leading Edges ◽  
Interaction Regions

Abstract. Co-rotating interaction regions (CIRs) between fast and slow streams of plasma are a prominent feature of the solar wind. Measurements of interplanetary scintillation (IPS) using the three widely separated antennas of the EISCAT facility have been used to detect the compression regions at the leading edges of interaction regions and to determine the location and velocity of the structure. Observations show that interaction regions have developed as close to the Sun as 25–30 solar radii, a result supported by theoretical modelling which shows that the conditions needed for CIRs to develop exist inside 30 solar radii. Key words. EISCAT · Interplanetary scintillation · Solar Wind

scholarly journals EISCAT measurements of the solar wind

1996 ◽  
Vol 14 (12) ◽  
pp. 1235-1245 ◽  
Author(s):  
A. R. Breen ◽  
W. A. Coles ◽  
R. R. Grall ◽  
M. T. Klinglesmith ◽  
J. Markkanen ◽  
...  
Keyword(s):  
Solar Wind ◽  
Slow Solar Wind ◽  
The Sun ◽  
Interplanetary Scintillation ◽  
Final Velocity ◽  
Flow Vector ◽  
Fast Wind ◽  
Interaction Regions ◽  
Slow Wind ◽  
Eiscat Measurements

Abstract. EISCAT observations of interplanetary scintillation have been used to measure the velocity of the solar wind at distances between 15 and 130 R⊙ (solar radii) from the Sun. The results show that the solar wind consists of two distinct components, a fast stream with a velocity of ~800 km s–1 and a slow stream at ~400 km s–1. The fast stream appears to reach its final velocity much closer to the Sun than expected. The results presented here suggest that this is also true for the slow solar wind. Away from interaction regions the flow vector of the solar wind is purely radial to the Sun. Observations have been made of fast wind/slow wind interactions which show enhanced levels of scintillation in compression regions.

Formation of current sheets and plasmoids within corotating/stream interaction regions

2020 ◽  
Author(s):  
Timofey Sagitov ◽  
Roman Kislov
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Coronal Hole ◽  
High Speed ◽  
Solar Rotation ◽  
Coronal Holes ◽  
Rotation Period ◽  
The Sun ◽  
Current Sheets ◽  
Interaction Regions

<p>High speed streams originating from coronal holes are long-lived plasma structures that form corotating interaction regions (CIRs) or stream interface regions (SIRs) in the solar wind. The term CIR is used for streams existing for at least one solar rotation period, and the SIR stands for streams with a shorter lifetime. Since the plasma flows from coronal holes quasi-continuously, CIRs/SIRs simultaneously expand and rotate around the Sun, approximately following the Parker spiral shape up to the Earth’s orbit.</p><p>Coronal hole streams rotate not only around the Sun but also around their own axis of simmetry, resembling a screw. This effect may occur because of the following mechanisms: (1) the existence of a difference between the solar wind speed at different sides of the stream, (2) twisting of the magnetic field frozen into the plasma, and  (3) a vortex-like motion of the edge of the mothering coronal hole at the Sun. The screw type of the rotation of a CIR/SIR can lead to centrifugal instability if CIR/SIR inner layers have a larger angular velocity than the outer. Furthermore, the rotational plasma movement and the stream distortion can twist magnetic field lines. The latter contributes to the pinch effect in accordance with a well-known criterion of Suydam instability (Newcomb, 1960, doi: 10.1016/0003-4916(60)90023-3). Owing to the presence of a cylindrical current sheet at the boundary of a coronal hole, conditions for tearing instability can also appear at the CIR/SIR boundary. Regardless of their geometry, large scale current sheets are subject to various instabilities generating plasmoids. Altogether, these effects can lead to the formation of a turbulent region within CIRs/SIRs, making them filled with current sheets and plasmoids. </p><p>We study a substructure of CIRs/SIRs, characteristics of their rotation in the solar wind, and give qualitative estimations of possible mechanisms which lead to splitting of the leading edge a coronal hole flow and consequent formation of current sheets within CIRs/SIRs.</p>

scholarly journals Observations of interplanetary scintillation in China

2012 ◽  
Vol 8 (S294) ◽  
pp. 487-488
Author(s):  
Li-Jia Liu ◽  
Bo Peng
Keyword(s):  
Solar Wind ◽  
Interplanetary Medium ◽  
Interplanetary Space ◽  
Solar Wind Speed ◽  
Small Diameter ◽  
Primary Source ◽  
Radio Sources ◽  
The Sun ◽  
Interplanetary Scintillation ◽  
The Earth

AbstractThe Sun affects the Earth in multiple ways. In particular, the material in interplanetary space comes from coronal expansion in the form of solar wind, which is the primary source of the interplanetary medium. Ground-based Interplanetary Scintillation (IPS) observations are an important and effective method for measuring solar wind speed and the structures of small diameter radio sources. In this paper we will discuss the IPS observations in China.

scholarly journals IPS Observations at STELAB for the Fruitful Coming Decade

1996 ◽  
Vol 154 ◽  
pp. 247-250
Author(s):  
K. Asai ◽  
Y. Ishida ◽  
M. Kojima ◽  
K. Maruyama ◽  
H. Misawa ◽  
...  
Keyword(s):  
Solar Wind ◽  
Temporal Resolution ◽  
Observation System ◽  
Present System ◽  
Radio Sources ◽  
Interplanetary Scintillation ◽  
Wind Measurements ◽  
Insufficient Sensitivity

AbstractWe have been carrying out solar wind measurements using the interplanetary scintillation (IPS) method. Our IPS observation system is operated at a frequency of 327MHz and consists of four stations located at Toyokawa, Fuji, Sugadaira and Kiso. The present system, however, has insufficient sensitivity to measure enough IPS sources for observing the solar wind with adequate spatial and temporal resolution. Therefore we have been excuting the upgrade project since 1994 in order to observe a larger number of compact radio sources. The Fuji system has been improved successfully and has achieved sensitivity by a factor over five compared with the previous system. The upgrade project is now in progress for the Toyokawa and Sugadaira station.

Preliminary results of Space Weather conditions encountered by BepiColombo during the first phase of its cruise

2020 ◽  
Author(s):  
Beatriz Sanchez-Cano ◽  
Richard Moissl ◽  
Daniel Heyner ◽  
Juhani Huovelin ◽  
M. Leila Mays ◽  
...  
Keyword(s):  
Solar Wind ◽  
Space Weather ◽  
High Speed ◽  
Weather Conditions ◽  
Slow Solar Wind ◽  
Astronomical Unit ◽  
The Sun ◽  
Preliminary Results ◽  
Outer Planets ◽  
Interaction Regions

<p>Planetary Space Weather is the discipline that studies the state of the Sun and how it interacts with the interplanetary and planetary environments. It is driven by the Sun’s activity, particularly through large eruptions of plasma (known as coronal mass ejections, CMEs), solar wind stream interaction regions (SIR) formed by the interaction of high-speed solar wind streams with the preceding slower solar wind, and bursts of solar energetic particles (SEPs) that form radiation storms. This is an emerging topic, whose real-time forecast is very challenging because among other factors, it needs a continuous coverage of its variability within the whole heliosphere as well as of the Sun’s activity to improve forecasting. <br />The long cruise of BepiColombo constitutes an exceptional opportunity for studying the Space Weather evolution within half-astronomical unit (AU), as well as in certain parts of its journey, can be used as an upstream solar wind monitor for Venus, Mars and even the outer planets. This work will present preliminary results of the Space Weather conditions encountered by BepiColombo since its launch until mid-2020, which includes data from the solar minimum of activity and few slow solar wind structures. Data come from three of its instruments that are operational for most of the cruise phase, i.e., the BepiColombo Radiation Monitor (BERM), the Mercury Planetary Orbiter Magnetometer (MPO-MAG), and the Solar Intensity X-ray and particle Spectrometer (SIXS). Modelling support for the data observations will be also presented with the so-called solar wind ENLIL simulations.</p>

Observations of micro-turbulence in the solar wind near the sun with interplanetary scintillation

1996 ◽  
Author(s):  
Y. Yamauchi ◽  
M. Tokumaru ◽  
M. Kojima ◽  
M. Misawa ◽  
H. Mori ◽  
...  
Keyword(s):  
Solar Wind ◽  
The Sun ◽  
Interplanetary Scintillation

Two-Station Interplanetary Scintillation Measurements of Solar Wind Speed near the Sun Using the X-band Radio Signal of the Nozomi Spacecraft

Solar Physics ◽  
2011 ◽  
Vol 276 (1-2) ◽  
pp. 315-336 ◽  
Author(s):  
M. Tokumaru ◽  
S. Fujimaki ◽  
M. Higashiyama ◽  
A. Yokobe ◽  
T. Ohmi ◽  
...  
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Radio Signal ◽  
Solar Wind Speed ◽  
The Sun ◽  
Interplanetary Scintillation ◽  
X Band

scholarly journals Enhanced Radio Source Scintillation due to Comet Austin (1989c1)

1991 ◽  
Vol 44 (5) ◽  
pp. 565 ◽  
Author(s):  
P Janardhan ◽  
SK Alurkar ◽  
AD Bobra ◽  
OB Slee
Keyword(s):  
Solar Wind ◽  
Radio Source ◽  
Electron Density ◽  
Density Variation ◽  
Scintillation Index ◽  
The Sun ◽  
Interplanetary Scintillation ◽  
Electron Density Variation ◽  
Comet Halley

Enhanced scintillations in the direction of the quasar 2204+29 (3C441) were observed on 13 May 1990 when the tail of Comet Austin passed in front of it. Comparison with previous observations at 103, 327 and 408 MHz of Comet Halley and at 408 MHz of Comet Wilson show that proper occultation geometry is essential for observing enhanced scintillations. It has been shown that the solar elongation ? during such observations should be large, typically greater than 60� and in no case less than 30� at 103 MHz. At the time of the occultation the scintillation index (r.m.s./mean source flux) was greater than that expected for this source by a factor of 3. The r.m.s. electron density variation /IN, at a distance of 0�9 A.U. from the sun and 7�3� downstream of the nucleus, was found to be 6 cm-3 as compared with 1 cm-3 for the normal solar wind at 1 A.U. The corresponding scale sizes of the turbulence were found to be much finer than normally found in interplanetary scintillation (IPS) caused by the solar wind.

scholarly journals Tomography of the Solar Wind using Interplanetary Scintillation

2000 ◽  
Vol 179 ◽  
pp. 445-446 ◽  
Author(s):  
Divya Oberoi ◽  
A. Pramesh Rao
Keyword(s):  
Solar Wind ◽  
Solar Surface ◽  
Line Of Sight ◽  
Weighted Sum ◽  
The Sun ◽  
Interplanetary Scintillation ◽  
The Earth ◽  
Compact Radio Source ◽  
Different Sources ◽  
Inner Heliosphere

Extended AbstractInterplanetary scintillation (IPS) measurements are sensitive to a weighted sum of the properties of solar wind (SW) along the line-of-sight (los) to a distant compact radio source. Mapping alosback to the surface of the Sun provides information of the sites of origin of the SW sampled by thelos. By observing different sources, lines-of-sight can be so chosen that they sample overlapping regions of Solar surface. In addition, the rotation of the Sun causes the long lived features in the SW to co-rotate, much like the twirling skirt of a ballerina, presenting different perspective views to the Earth based observers. These properties raise the possibility that systematic IPS observations can be inverted to give the maps of density and the velocity of the SW in the inner heliosphere, using techniques similar to tomography.

scholarly journals Interplanetary Scintillation Observations of Stream Interaction Regions in the Solar Wind

Solar Physics ◽  
2009 ◽  
Vol 261 (1) ◽  
pp. 149-172 ◽  
Author(s):  
M. M. Bisi ◽  
R. A. Fallows ◽  
A. R. Breen ◽  
I. J. O’Neill
Keyword(s):  
Solar Wind ◽  
Interplanetary Scintillation ◽  
Interaction Regions
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