arXiv subjects

Wageesh Mishra

Publications and source records attributed to Wageesh Mishra.

35 records · Page 2Linked to original sources

arXiv2023

Observation of Alfven wave in ICME-HSS interaction region

The Alfvén wave (AW) is the most common fluctuation present within the emitted solar wind from the Sun. Moreover, the interaction between interplanetary coronal mass ejection (ICME) and high-speed stream (HSS) has been observed on several occasions. However, can such interaction generate an AW? What will be the nature of AW in such a scenario remains an open question. To answer it, we have investigated an ICME-HSS interaction event observed on 21st October 1999 at 1 AU by Wind spacecraft. We have used the Walén test to identify AW and estimated Elsasser variables to find the characteristics of the AWs. We explicitly find that ICME were dominant with Sunward AWs, whereas the trailing HSS has strong anti-Sunward AW. We suggest that the ICME-HSS interaction deforms the MC of the ICME, resulting in the AWs inside the MC. In addition, the existence of reconnection within the ICME early stage can also be the leading cause of the origin of AW within it.

astro-ph.SR↗

arXiv2022

Propagation of Coronal Mass Ejections from the Sun to Earth

Coronal Mass Ejections (CMEs), as they can inject a large amounts of mass and magnetic flux into the interplanetary space, are the primary source of space weather phenomena on the Earth. The present review first briefly introduces the solar surface signatures of the origins of CMEs and then focuses on the attempts to understand the kinematic evolution of CMEs from the Sun to the Earth. CMEs have been observed in the solar corona in white-light from a series of space missions over the last five decades. In particular, LASCO/SOHO has provided almost continuous coverage of CMEs for more than two solar cycles until today. However, the observations from LASCO suffered from projection effects and limited field of view (within 30 Rs from the Sun). The launch in 2006 of the twin STEREO spacecraft made possible multiple viewpoints imaging observations, which enabled us to assess the projection effects on CMEs. Moreover, heliospheric imagers (HIs) onboard STEREO continuously observed the large and unexplored distance gap between the Sun and Earth. Finally, the Earth-directed CMEs that before have been routinely identified only near the Earth at 1 AU in in situ observations from ACE and WIND, could also be identified at longitudes away from the Sun-Earth line using the in situ instruments onboard STEREO. Our review presents the frequently used methods for estimation of the kinematics of CMEs and their arrival time at 1 AU using primarily SOHO and STEREO observations. We emphasize the need of deriving the three-dimensional (3D) properties of Earth-directed CMEs from the locations away from the Sun-Earth line. The results improving the CME arrival time prediction at Earth and the open issues holding back progress are also discussed. Finally, we summarize the importance of heliospheric imaging and discuss the path forward to achieve improved space weather forecasting.

astro-ph.SR↗

arXiv2022

Evolution and Consequences of Coronal Mass Ejections in the Heliosphere

Investigating the heliospheric evolution and consequences of Coronal mass ejections (CMEs) is critical to understanding the solar-terrestrial relationship. For the first time, Heliospheric Imagers (HIs) onboard STEREO, providing multiple views of CMEs in the heliosphere, observed the vast and crucial observational gap between the Sun and the Earth. Using J-maps constructed from coronagraphs (CORs) and HIs observations, we continuously tracked different density enhanced features of CMEs. We implemented several reconstruction methods to estimate the three-dimensional (3D) kinematics of CMEs during their evolution from the Sun to Earth. Our study provides evidence that the 3D speeds of CMEs near the Sun are not reasonably sufficient for understanding the propagation and accurate forecasting of the arrival time at the Earth of a majority of CMEs. This finding can be due to many factors that significantly change the CME kinematics beyond the COR field of view, such as the interaction/collision of two or more CMEs or the interaction of CMEs with the ambient solar wind medium. We attempted to understand the evolution and consequences of the interacting/colliding CMEs in the heliosphere using STEREO/HI, WIND, and ACE observations. The study found a significant change in the dynamics of the CMEs after their collision and interaction. The in situ observations show the signatures of CME-CME interaction as heating and compression, formation of magnetic holes (MHs), and interaction region (IR). We also noticed that long-lasting IR, formed at the rear edge of preceding CME, is responsible for large geomagnetic perturbations. Our study highlights the significance of using HIs observations in studying heliospheric evolution of CMEs, CME-CME collision, identifying and associating the three-part structure of CMEs in their remote and in situ observations, and hence for improved space weather forecasting.

astro-ph.SR↗

arXiv2019

Mass Loss via Solar Wind and Coronal Mass Ejections During Solar Cycle 23 and 24

Similar to the Sun, other stars shed mass and magnetic flux via ubiquitous quasi-steady wind and episodic stellar coronal mass ejections (CMEs). We investigate the mass loss rate via solar wind and CMEs as a function of solar magnetic variability represented in terms of sunspot number and solar X-ray background luminosity. We estimate the contribution of CMEs to the total solar wind mass flux in the ecliptic and beyond, and its variation over different phases of the solar activity cycles. The study exploits the number of sunspots observed, coronagraphic observations of CMEs near the Sun by SOHO/LASCO, in situ observations of the solar wind at 1 AU by WIND, and GOES X-ray flux during solar cycle 23 and 24. We note that the X-ray background luminosity, occurrence rate of CMEs and ICMEs, solar wind mass flux, and associated mass loss rates from the Sun do not decrease as strongly as the sunspot number from the maximum of solar cycle 23 to the next maximum. Our study confirms a true physical increase in CME activity relative to the sunspot number in cycle 24. We show that the CME occurrence rate and associated mass loss rate can be better predicted by X-ray background luminosity than the sunspot number. The solar wind mass loss rate which is an order of magnitude more than the CME mass loss rate shows no obvious dependency on cyclic variation in sunspot number and solar X-ray background luminosity. These results have implications to the study of solar-type stars.

astro-ph.SR↗

arXiv2018

Torsional Alfven wave embedded ICME magnetic cloud and corresponding geomagnetic storm

The energy transfer during the interaction of large-scale solar wind structure and the Earth's magnetosphere is the chronic issue in space-weather studies. To understand this, researchers widely studied the geomagnetic storms and sub-storms phenomena. The present understanding suggests that long duration of southward interplanetary magnetic field component is the most important parameter for the geomagnetic storm. Such long duration strong southward magnetic field is often associated with ICMEs, torsional Alfven fluctuations superposed co-rotating interacting regions (CIRs) and fast solar wind streams. Torsional Alfven fluctuations embedded CIRs have been known for a long, however magnetic cloud embedded with such fluctuations are rarely observed. The presence of Alfven waves in the ICME/MC and influence of these waves on the storm evolution remains an interesting topic of study. The present work confirms the torsional Alfven waves in a magnetic cloud associated with a CME launched on 15th February which impacted the Earth's magnetosphere on February 18, 2011. Further, observations indicate that these waves inject energy into the magnetosphere during the storm and contribute to the long recovery time of geomagnetic storms. Our study suggests that presence of torsional Alfven waves significantly controls the storm dynamics.

physics.space-ph↗

arXiv2018

Modeling the thermodynamic evolution of Coronal Mass Ejections (CMEs) using their kinematics

Earlier studies on Coronal Mass Ejections (CMEs), using remote sensing and in situ observations, have attempted to determine some of the internal properties of CMEs, which were limited to a certain position or a certain time. For understanding the evolution of the internal thermodynamic state of CMEs during their heliospheric propagation, we improve the self-similar flux rope internal state (FRIS) model, which is constrained by measured propagation and expansion speed profiles of a CME. We implement the model to a CME erupted on 2008 December 12 and probe the internal state of the CME. It is found that the polytropic index of the CME plasma decreased continuously from 1.8 to 1.35 as the CME moved away from the Sun, implying that the CME released heat before it reached adiabatic state and then absorbed heat. We further estimate the entropy changing and heating rate of the CME. We also find that the thermal force inside the CME is the internal driver of CME expansion while Lorentz force prevented the CME from expanding. It is noted that centrifugal force due to poloidal motion decreased with the fastest rate and Lorentz force decreased slightly faster than thermal pressure force as CME moved away from the Sun. We also discuss the limitations of the model and approximations made in the study.

astro-ph.SR↗

arXiv2018

Study of Interplanetary and Geomagnetic Response of Filament Associated CMEs

It has been established that Coronal Mass Ejections (CMEs) may have significant impact on terrestrial magnetic field and lead to space weather events. In the present study, we selected several CMEs which are associated with filament eruptions on the Sun. We attempt to identify the presence of filament material within ICME at 1AU. We discuss how different ICMEs associated with filaments lead to moderate or major geomagnetic activity on their arrival at the Earth. Our study also highlights the difficulties in identifying the filament material at 1AU within isolated and in interacting CMEs.

astro-ph.SR↗

arXiv2018

Solar cycle variation of coronal mass ejections contribution to solar wind mass flux

Coronal Mass Ejections (CMEs) contributes to the perturbation of solar wind in the heliosphere. Thus, depending on the different phases of the solar cycle and the rate of CME occurrence, contribution of CMEs to solar wind parameters near the Earth changes. In the present study, we examine the long term occurrence rate of CMEs, their speeds, angular widths and masses. We attempt to find correlation between near sun parameters, determined using white light images from coronagraphs, with solar wind measurements near the Earth from in-situ instruments. Importantly, we attempt to find what fraction of the averaged solar wind mass near the Earth is provided by the CMEs during different phases of the solar cycles.

astro-ph.SR↗

arXiv2017

Interplanetary and Geomagnetic Consequences of Interacting CMEs of 13-14 June 2012

We report on the kinematics of two interacting CMEs observed on 13 and 14 June 2012. Both CMEs originated from the same active region NOAA 11504. After their launches which were separated by several hours, they were observed to interact at a distance of 100 Rs from the Sun. The interaction led to a moderate geomagnetic storm at the Earth with Dst index of approximately, -86 nT. The kinematics of the two CMEs is estimated using data from the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) onboard the Solar Terrestrial Relations Observatory (STEREO). Assuming a head-on collision scenario, we find that the collision is inelastic in nature. Further, the signatures of their interaction are examined using the in situ observations obtained by Wind and the Advance Composition Explorer (ACE) spacecraft. It is also found that this interaction event led to the strongest sudden storm commencement (SSC) (approximately 150 nT) of the present Solar Cycle 24. The SSC was of long duration, approximately 20 hours. The role of interacting CMEs in enhancing the geoeffectiveness is examined.

astro-ph.SR↗

arXiv2017

Assessing the collision nature of coronal mass ejections in the inner heliosphere

There have been few attempts in the past to understand the collision of individual cases of interacting Coronal Mass Ejections (CMEs). We selected 8 cases of interacting CMEs and estimated their propagation and expansion speeds, direction of impact and masses exploiting coronagraphic and heliospheric imaging observations. Using these estimates with ignoring the errors therein, we find that the nature of collision is perfectly inelastic for 2 cases (e.g., 2012 March and November), inelastic for 2 cases (e.g., 2012 June and 2011 August), elastic for 1 case (e.g., 2013 October) and super-elastic for 3 cases (e.g., 2011 February, 2010 May and 2012 September). Admitting large uncertainties in the estimated directions, angular widths and pre-collision speeds; the probability of perfectly inelastic collision for 2012 March and November cases diverge from 98%-60% and 100%-40%, respectively, reserving some probability for other nature of collision. Similarly, the probability of inelastic collision diverge from 95%-50% for 2012 June case, 85%-50% for 2011 August case, and 75%-15% for 2013 October case. We note that probability of super-elastic collision for 2011 February, 2010 May and 2012 September CMEs diverge from 90%-75%, 60%-45% and 90%-50%, respectively. Although the sample size is small, we find a good dependence of nature of collision on CMEs parameters. The crucial pre-collision parameters of the CMEs responsible for increasing the probability of super-elastic collision, in descending order of priority, are their lower approaching speed, higher expansion speed of the following CME over the preceding one, and longer duration of collision phase.

astro-ph.SR↗

arXiv2016

On Understanding the Nature of Collision of Coronal Mass Ejections Observed by \textit{STEREO}

Our study attempts to understand the collision characteristics of two coronal mass ejections (CMEs) launched successively from the Sun on 2013 October 25. The estimated kinematics, from three-dimensional (3D) reconstruction techniques applied to observations of CMEs by SECCHI/Coronagraphic (COR) and Heliospheric Imagers (HIs), reveal their collision around 37 $R_\sun$ from the Sun. In the analysis, we take into account the propagation and expansion speeds, impact direction, angular size as well as the masses of the CMEs. These parameters are derived from imaging observations, but may suffer from large uncertainties. Therefore, by adopting head-on as well as oblique collision scenarios, we have quantified the range of uncertainties involved in the calculation of the coefficient of restitution for expanding magnetized plasmoids. Our study shows that the comparatively large expansion speed of the following CME than that of the preceding CME, results in a higher probability of super-elastic collision. We also infer that a relative approaching speed of the CMEs lower than the sum of their expansion speeds increases the chance of super-elastic collision. The analysis under a reasonable errors in observed parameters of the CME, reveals the larger probability of occurrence of an inelastic collision for the selected CMEs. We suggest that the collision nature of two CMEs should be discussed in 3D, and the calculated value of the coefficient of restitution may suffer from a large uncertainty.

astro-ph.SR↗

arXiv2015

Kinematics of Interacting CMEs of September 25 and 28, 2012

We have studied two Coronal Mass Ejections (CMEs) that occurred on September 25 and 28, 2012 and interacted near the Earth. By fitting the Graduated Cylindrical Shell (GCS) model on the SECCHI/COR2 images and applying the Stereoscopic Self-Similar Expansion (SSSE) method on the SECCHI/HI images, the initial direction of both the CMEs is estimated to be west of the Sun-Earth line. Further, the three-dimensional (3D) heliospheric kinematics of these CMEs have been estimated using Self-Similar Expansion (SSE) reconstruction method. We show that use of SSE method with different values of angular extent of the CMEs, leads to significantly different kinematics estimates for the CMEs propagating away from the observer. Using the estimated kinematics and true masses of the CMEs, we have derived the coefficient of restitution for the collision which is found to be close to elastic. The in situ measurements at 1 AU show two distinct structures of interplanetary CMEs, heating of the following CME, as well as ongoing interaction between the preceding and the following CME. We highlight the signatures of interaction in remote and in situ observations of these CMEs and the role of interaction in producing a major geomagnetic storm.

astro-ph.SR↗

arXiv2015

Heliospheric tracking of enhanced density structures of the 6 October 2010 CME

A Coronal Mass Ejection (CME) is an inhomogeneous structure consisting of different features which evolve differently with the propagation of the CME. Simultaneous heliospheric tracking of different observed features of a CME can improve our understanding about relative forces acting on them. It also helps to estimate accurately their arrival times at the Earth and identify them in in- situ data. This also enables to find association between remotely observed features and in-situ observations near the Earth. In this paper, we attempt to continuously track two density enhanced features, one at the front and another at the rear edge of the 6 October 2010 CME. This is achieved by using time-elongation maps constructed from STEREO/SECCHI observations. We derive the kinematics of the tracked features using various reconstruction methods. The estimated kinematics are used as inputs in the Drag Based Model (DBM) to estimate the arrival time of the tracked features of the CME at L1. On comparing the estimated kinematics as well as the arrival times of the remotely observed features with in-situ observations by ACE and Wind, we find that the tracked bright feature in the J-map at the rear edge of 6 October 2010 CME corresponds most probably to the enhanced density structure after the magnetic cloud detected by ACE and Wind. In-situ plasma and compositional parameters provide evidence that the rear edge density structure may correspond to a filament associated with the CME while the density enhancement at the front corresponds to the leading edge of the CME. Based on this single event study, we discuss the relevance and significance of heliospheric imager (HI) observations in identification of the three-part structure of the CME.

astro-ph.SR↗

arXiv2014

Morphological and Kinematic Evolution of Three Interacting Coronal Mass Ejections of 2011 February 13-15

During 2011 February 13 to 15, three Earth-directed CMEs launched in successively were recorded as limb CMEs by coronagraphs (COR) of STEREO. These CMEs provided an opportunity to study their geometrical and kinematic evolution from multiple vantage points. In this paper, we examine the differences in geometrical evolution of slow and fast speed CMEs during their propagation in the heliosphere. We also study their interaction and collision using STEREO/SECCHI COR and Heliospheric Imager (HI) observations. We have found evidence of interaction and collision between the CMEs of February 15 and 14 in COR2 and HI1 FOV, respectively, while the CME of February 14 caught the CME of February 13 in HI2 FOV. By estimating the true mass of these CMEs and using their pre and post-collision dynamics, the momentum and energy exchange between them during collision phase are studied. We classify the nature of observed collision between CME of February 14 and 15 as inelastic, reaching close to elastic regime. Relating imaging observations with the in situ measurements, we find that the CMEs move adjacent to each other after their collision in the heliosphere and are recognized as distinct structures in in situ observations by WIND spacecraft at L1. Our results highlight the significance of HI observations in studying CME-CME collision for the purpose of improved space weather forecasting.

astro-ph.SR↗

arXiv2014

Evolution and Consequences of Interacting CMEs of 2012 November 9-10 using STEREO/SECCHI and In Situ Observations

Understanding of the kinematic evolution of Coronal Mass Ejections (CMEs) in the heliosphere is important to estimate their arrival time at the Earth. It is found that kinematics of CMEs can change when they interact or collide with each other as they propagate in the heliosphere. In this paper, we analyze the collision and post-interaction characteristics of two Earth-directed CMEs, launched successively on 2012 November 9 and 10, using white light imaging observations from STEREO/SECCHI and in situ observations taken from WIND spacecraft. We tracked two density enhanced features associated with leading and trailing edge of November 9 CME and one density enhanced feature associated with leading edge of November 10 CME by constructing J-maps. We found that the leading edge of November 10 CME interacted with the trailing edge of November 9 CME. We also estimated the kinematics of these features of the CMEs and found a significant change in their dynamics after interaction. In in situ observations, we identified distinct structures associated with interacted CMEs and also noticed their heating and compression as signatures of CME-CME interaction. Our analysis shows an improvement in arrival time prediction of CMEs using their post-collision dynamics than using pre-collision dynamics. Estimating the true masses and speeds of these colliding CMEs, we investigated the nature of observed collision which is found to be close to perfectly inelastic. The investigation also places in perspective the geomagnetic consequences of the two CMEs and their interaction in terms of occurrence of geomagnetic storm and triggering of magnetospheric substorms.

astro-ph.SR↗

arXiv2014

A comparison of reconstruction methods for the estimation of CME kinematics based on SECCHI/HI observations

A study of the kinematics and arrival times of CMEs at Earth, derived from time-elongation maps (J-maps) constructed from STEREO/Heliospheric Imager (HI) observations, provides an opportunity to understand the heliospheric evolution of CMEs in general. We implement various reconstruction techniques, based on the use of time-elongation profiles of propagating CMEs viewed from single or multiple vantage points, to estimate the dynamics of three geo-effective CMEs. We use the kinematic properties, derived from analysis of the elongation profiles, as inputs to the Drag Based Model for the distance beyond which the CMEs cannot be tracked unambiguously in the J-maps. The ambient solar wind into which these CMEs, which travel with different speeds, are launched, is different. Therefore, these CMEs will evolve differently throughout their journey from the Sun to 1 AU. We associate the CMEs, identified and tracked in the J-maps, with signatures observed in situ near 1 AU by the WIND spacecraft. By deriving the kinematic properties of each CME, using a variety of existing methods, we assess the relative performance of each method for the purpose of space weather forecasting. We discuss the limitations of each method, and identify the major constraints in predicting the arrival time of CMEs near 1 AU using heliospheric imager observations.

astro-ph.SR↗

arXiv2013

Estimating arrival time of Earth-directed CMEs at \textit{in-situ} spacecraft using COR & HI observations from STEREO

The prediction of the arrival time and transit speed of CMEs near the Earth is one of the key problems in understanding the solar terrestrial relationship. Although, STEREO observations now provide a multiple view of CMEs in the heliosphere, the true speeds derived from stereoscopic reconstruction of SECCHI coronagraph data are not quite sufficient in accurate forecasting of arrival time of a majority of CMEs at the Earth. This is due to many factors which change the CME kinematics, like interaction of two or more CMEs or the interaction of CMEs with the pervading solar wind. In order to understand the propagation of CMEs, we have used the 3D triangulation method on SECCHI coronagraph (COR2) images, and geometric triangulation on the J-maps constructed from Heliospheric Imagers HI1 and HI2 images for eight Earth-directed CMEs observed during 2008-2010. Based on the reconstruction, and implementing the Drag Based Model for the distance where the CMEs could not be tracked unambiguously in the interplanetary medium, the arrival time of these CMEs have been estimated. These arrival times have also been compared with the actual arrival time as observed by \textit{in-situ} instruments. The analysis reveals the importance of heliospheric imaging for improved forecasting of the arrival time and direction of propagation of CMEs in the interplanetary medium.

astro-ph.SR↗