scholarly journals The role of aerodynamic drag in dynamics of coronal mass ejections

2008 ◽  
Vol 4 (S257) ◽  
pp. 271-277
Author(s):  
Bojan Vršnak ◽  
Dijana Vrbanec ◽  
Jaša Čalogović ◽  
Tomislav Žic
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Coronal Mass Ejections ◽  
Weather Forecasting ◽  
Aerodynamic Drag ◽  
Interplanetary Space ◽  
Solar Wind Speed ◽  
Standard Form ◽  
The Sun

AbstractDynamics of coronal mass ejections (CMEs) is strongly affected by the interaction of the erupting structure with the ambient magnetoplasma: eruptions that are faster than solar wind transfer the momentum and energy to the wind and generally decelerate, whereas slower ones gain the momentum and accelerate. Such a behavior can be expressed in terms of “aerodynamic” drag. We employ a large sample of CMEs to analyze the relationship between kinematics of CMEs and drag-related parameters, such as ambient solar wind speed and the CME mass. Employing coronagraphic observations it is demonstrated that massive CMEs are less affected by the aerodynamic drag than light ones. On the other hand, in situ measurements are used to inspect the role of the solar wind speed and it is shown that the Sun-Earth transit time is more closely related to the wind speed than to take-off speed of CMEs. These findings are interpreted by analyzing solutions of a simple equation of motion based on the standard form for the drag acceleration. The results show that most of the acceleration/deceleration of CMEs on their way through the interplanetary space takes place close to the Sun, where the ambient plasma density is still high. Implications for the space weather forecasting of CME arrival-times are discussed.

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.

Study of alpha particle properties across rarefaction regions

2021 ◽  
Author(s):  
Tereza Durovcova ◽  
Jana Šafránková ◽  
Zdeněk Němeček
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Alpha Particle ◽  
Solar Wind Speed ◽  
Coronal Holes ◽  
Distribution Functions ◽  
Alpha Particles ◽  
Slow Solar Wind ◽  
The Sun ◽  
Wind Source

<p>Two large-scale interaction regions between the fast solar wind emanating from coronal holes and the slow solar wind coming from streamer belt are usually distinguished. When the fast stream pushes up against the slow solar wind ahead of it, a compressed interaction region that co-rotates with the Sun (CIR) is created. It was already shown that the relative abundance of alpha particles, which usually serve as one of solar wind source identifiers can change within this region. By symmetry, when the fast stream outruns the slow stream, a corotating rarefaction region (CRR) is formed. CRRs are characterized by a monotonic decrease of the solar wind speed, and they are associated with the regions of small longitudinal extent on the Sun. In our study, we use near-Earth measurements complemented by observations at different heliocentric distances, and focus on the behavior of alpha particles in the CRRs because we found that the large variations of the relative helium abundance (AHe) can also be observed there. Unlike in the CIRs, these variations are usually not connected with the solar wind speed and alpha-proton relative drift changes. We thus apply a superposed-epoch analysis of identified CRRs with a motivation to determine the global profile of alpha particle parameters through these regions. Next, we concentrate on the cases with largest AHe variations and investigate whether they can be associated with the changes of the solar wind source region or whether there is a relation between the AHe variations and the non-thermal features in the proton velocity distribution functions like the temperature anisotropy and/or presence of the proton beam.</p>

Numerical Simulation on the Propagation and Deflection of Fast Coronal Mass Ejections (CMEs) Interacting with a Corotating Interaction Region in Interplanetary Space

2020 ◽  
Author(s):  
Fang Shen ◽  
Yousheng Liu ◽  
Yi Yang
Keyword(s):  
Solar Wind ◽  
Coronal Mass Ejections ◽  
Interplanetary Space ◽  
Three Dimensional ◽  
Flux Rope ◽  
Interaction Region ◽  
The Sun ◽  
Corotating Interaction Region ◽  
The Common ◽  
Wind Flows

<p>Previous research has shown that the deflection of coronal mass ejections (CMEs) in interplanetary space, especially fast CMEs, is a common phenomenon. The deflection caused by the interaction with background solar wind is an important factor to determine whether CMEs could hit Earth or not. As the Sun rotates, there will be interactions between solar wind flows with different speeds. When faster solar wind runs into slower solar wind<br>ahead, it will form a compressive area corotating with the Sun, which is called a corotating interaction region (CIR). These compression regions always have a higher density than the common background solar wind. When interacting with CME, will this make a difference in the deflection process of CME? In this research, first, a three-dimensional (3D) flux-rope CME initialization model is established based on the graduated cylindrical shell (GCS)<br>model. Then this CME model is introduced into the background solar wind, which is obtained using a 3D IN (INterplanetary) -TVD-MHD model. The Carrington Rotation (CR) 2154 is selected as an example to simulate the propagation and deflection of fast CME when it interacts with background solar wind, especially with the CIR structure.</p><p>The simulation results show that: (1) the fast CME will deflect eastward when it propagates into the background solar wind without the CIR; (2) when the fast CME hits the CIR on its west side, it will also deflect eastward, and the deflection angle will increase compared with the situation without CIR.</p>

scholarly journals Forecasting the Ambient Solar Wind with Numerical Models. II. An Adaptive Prediction System for Specifying Solar Wind Speed near the Sun

2020 ◽  
Vol 891 (2) ◽  
pp. 165 ◽  
Author(s):  
Martin A. Reiss ◽  
Peter J. MacNeice ◽  
Karin Muglach ◽  
Charles N. Arge ◽  
Christian Möstl ◽  
...  
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Numerical Models ◽  
Solar Wind Speed ◽  
The Sun ◽  
Prediction System ◽  
Adaptive Prediction ◽  
Ambient Solar Wind

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

Study of solar flares associated with Geoeffective CMEs

2018 ◽  
Vol 13 (S340) ◽  
pp. 163-164
Author(s):  
Veena Choithani ◽  
Rajmal Jain ◽  
Duggirala Pallamraju
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Solar Flare ◽  
Coronal Mass Ejections ◽  
Solar Flares ◽  
Geomagnetic Storms ◽  
Solar Wind Speed ◽  
Dst Index ◽  
In The Beginning ◽  
The Imf

AbstractWe study 30 solar flare events associated with coronal mass ejections (CMEs) that produced geomagnetic storms as measured in Dst index. Our study reveals that the magnitude of Dst index is significantly associated with maximum solar wind speed, peak of Bz component of the IMF and the product of peak Bz and solar wind speed (minimum and maximum). From our investigations, it can be inferred that CMEs travel with higher speed in the beginning and their speed reduces as they reach L1 location.

Structure in the Solar Corona from Radio Scintillation Measurements

1996 ◽  
Vol 154 ◽  
pp. 97-104
Author(s):  
Richard Woo
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Recent Progress ◽  
Solar Wind Speed ◽  
Source Region ◽  
Density Fluctuations ◽  
The Sun ◽  
Fine Scale ◽  
Radio Scintillation ◽  
Electron Density Fluctuations

AbstractSince the 1950s, a wide variety of radio observations based on scattering by electron density fluctuations in the solar wind has provided much of our information on density fluctuations and solar wind speed near the source region of the solar wind. This paper reviews recent progress in the understanding of the nature of these density fluctuations and their relationship to features on the Sun. The results include the first measurements of fine-scale structure within coronal streamers and evidence for structure in solar wind speed in the inner corona.

scholarly journals A Bimodal Model of the Solar Wind Speed

1996 ◽  
Vol 154 ◽  
pp. 87-96
Author(s):  
W.A. Coles
Keyword(s):  
Remote Sensing ◽  
Solar Wind ◽  
Wind Speed ◽  
Solar Wind Velocity ◽  
Solar Wind Speed ◽  
Line Of Sight ◽  
Polar Regions ◽  
The Sun ◽  
High Latitudes ◽  
Bimodal Structure

AbstractUntil the ULYSSES spacecraft reached high latitude, the only means for measuring the solar wind velocity in the polar regions was from radio scattering observations (IPS), and these remain the only way to measure the velocity near the sun. However, IPS, like many remote sensing observations, is a “line-of-sight” integrated measurement. This integration is particularly troublesome when the line-of-sight passes through a fast stream but that stream does not occupy the entire scattering region. Observations from the HELIOS spacecraft have shown that the solar wind has a bimodal character which becomes more pronounced near the sun. Recent observations from ULYSSES have confirmed that this structure is clear at high latitudes even at relatively large solar distances. We have developed a method of separating the fast and slow contributions to an IPS observation which takes advantage of this bimodal structure. In this paper I will describe the technique and its application to IPS observations made using the receiving antennas of the EISCAT incoherent backscatter radar observatory in northern Scandinavia.

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