Publications (50)
Origins of Very Low Helium Abundance Streams Detected in the Solar Wind Plasma
Yogesh, N. Gopalswamy, D. Chakrabarty +4
The abundance of helium () in the solar wind exhibits variations typically in the range from 2-5% with respect to solar cycle activity and solar wind velocity. However, the…
Nonlinear MHD waves in a Prominence Foot
Leon Ofman, Kalman Knizhnik, Therese Kucera +1
We study nonlinear waves in a prominence foot using 2.5D MHD model motivated by recent high-resolution observations with Hinode/SOT in Ca~II emission of a prominence on October 10,…
Evidence of thermal conduction suppression in a solar flaring loop by coronal seismology of slow-mode waves
Tongjiang Wang, Leon Ofman, Xudong Sun +2
Analysis of a longitudinal wave event observed by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) is presented. A time sequence of 131 A images…
Effect of transport coefficients on excitation of flare-induced standing slow-mode waves in coronal loops
Tongjiang Wang, Leon Ofman, Xudong Sun +2
Standing slow-mode waves have been recently observed in flaring loops by the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO). By means of the coronal sei…
Modeling ion beams, kinetic instabilities, and waves observed by the Parker Solar Probe near perihelia
Leon Ofman, Scott A Boardsen, Lan K Jian +2
Recent in-situ observations from the Parker Solar Probe (PSP) mission in the inner heliosphere near perihelia show evidence of ion beams, temperature anisotropies, and kinetic wave…
Excitation of flare-induced waves in coronal loops and the effects of radiative cooling
Elena Provornikova, Leon Ofman, Tongjiang Wang
EUV imaging observations from several space missions (SOHO/EIT, TRACE, and SDO/AIA) have revealed a presence of propagating intensity disturbances in solar coronal loops. These dis…
Modeling hot, anisotropic ion beams in the solar wind motivated by the Parker Solar Probe observations near perihelia
Leon Ofman, Yogesh, Scott A Boardsen +5
Recent observations of the solar wind ions by the SPAN-I instruments on board the Parker Solar Probe (PSP) spacecraft at solar perihelia (Encounters) 4 and closer find ample eviden…
Identification of Ion-Kinetic Instabilities in Hybrid-PIC Simulations of Solar Wind Plasma with Machine Learning
Viacheslav M Sadykov, Leon Ofman, Scott A Boardsen +5
Analysis of ion-kinetic instabilities in solar wind plasmas is crucial for understanding energetics and dynamics throughout the heliosphere, as evident from spacecraft observations…
Nonlinear Evolution of Ion Kinetic Instabilities in the Solar Wind
Leon Ofman
In-situ observations of the solar wind (SW) plasma from 0.29 to 1AU show that the protons and alpha particles are often non-Maxwellian, with evidence of kinetic instabilities, temp…
Measuring temperature - dependent propagating disturbances in coronal fan loops using multiple SDO/AIA channels and surfing transform technique
Vadim M. Uritsky, Joseph M. Davila, Nicholeen M. Viall +1
A set of co-aligned high resolution images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) is used to investigate propagating disturbances…
Winds from Luminous Late-Type Stars: II. Broadband Frequency Distribution of Alfvén Waves
Vladimir Airapetian, Kenneth G. Carpenter, Leon Ofman
We present the numerical simulations of winds from evolved giant stars using a fully non-linear, time dependent 2.5-dimensional magnetohydrodynamic (MHD) code. This study extends o…
Solar Wind Heating Near the Sun: A Radial Evolution Approach
Yogesh, Leon Ofman, Kristopher Klein +19
Characterizing the plasma state in the near-Sun environment is essential to constrain the mechanisms that heat and accelerate the solar wind. In this study, we use Parker Solar Pro…
Reconnection generated plasma flows in the quasi-separatrix layer in localised solar corona
Sripan Mondal, A. K. Srivastava, Sudheer K. Mishra +8
Multiwavelength observations of the propagating disturbances (PDs), discovered by Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO), are analyzed to deter…
Advances in Observing Various Coronal EUV Waves in the SDO Era and Their Seismological Applications (Invited Review)
Wei Liu, Leon Ofman
Global extreme ultraviolet (EUV) waves are spectacular traveling disturbances in the solar corona associated with energetic eruptions such as coronal mass ejections (CMEs) and flar…
Evidence of Interaction between Ion-Scale Waves and Ion Velocity Distributions in the Solar Wind
Yogesh, Leon Ofman, Scott A Boardsen +9
Recent in situ observations from Parker Solar Probe (PSP) near perihelia reveal ion beams, temperature anisotropies, and kinetic wave activity. These features are likely linked to…
Automated identification of transiting exoplanet candidates in NASA Transiting Exoplanets Survey Satellite (TESS) data with machine learning methods
Leon Ofman, Amir Averbuch, Adi Shliselberg +3
A novel artificial intelligence (AI) technique that uses machine learning (ML) methodologies combines several algorithms, which were developed by ThetaRay, Inc., is applied to NASA…
SDO/AIA Observation of Kelvin-Helmholtz Instability in the Solar Corona
Leon Ofman, Barbara J. Thompson
We present observations of the formation, propagation and decay of vortex- shaped features in coronal images from the Solar Dynamics Observatory (SDO) associated with an eruption s…
Observations and Modeling of Unstable Proton and Alpha Particle Velocity Distributions in Sub-Alfvenic Solar Wind at PSP Perihelia
Leon Ofman, Scott A Boardsen, Lan K Jian +7
Past observations show that solar wind (SW) acceleration occurs inside the sub-Alfvenic region, reaching the local Alfven speed at typical distances ~ 10 - 20 Rs (solar radii). Rec…
Propagating Intensity Disturbances in Fan-like Coronal Loops: Flows or Waves?
Tongjiang Wang, Leon Ofman, Joseph M. Davila
Quasi-periodic intensity disturbances propagating upward along the coronal structure have been extensively studied using EUV imaging observations from SOHO/EIT and TRACE. They were…
Observation of Large-Scale Kelvin-Helmholtz Instability Wave Driven by a Coronal Mass Ejection
Leon Ofman, Olga Khabarova, Ryun-Yong Kwon +3
The Kelvin-Helmholtz instability (KHI) can occur when there is a relative motion between two adjacent fluids. In the case of magnetized plasma, the shear velocity must exceed the l…
Three dimensional MHD Modeling of Vertical Kink Oscillations in an Active Region Plasma Curtain
Leon Ofman, Marzia Parisi, Abhishek K. Srivastava
Observations on 2011 August 9 of an X6.9-class flare in active region (AR) 11263 by the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory (SDO), were follo…
Slow-Mode Oscillations of Hot Loops Excited at Flaring Footpoints
Tongjiang Wang, Wei Liu, Leon Ofman +1
The analysis of a hot loop oscillation event using SOHO/SUMER, GOES/SXI, and RHESSI observations is presented. Damped Doppler shift oscillations were detected in the Fe XIX line by…
Inference of Magnetic Field in the Coronal Streamer Invoking Kink Wave Motions generated by Multiple EUV Waves
A. K. Srivastava, Talwinder Singh, Leon Ofman +1
Using MHD seismology by observed kink waves, the magnetic field profile of a coronal streamer has been investigated. STEREO-B/EUVI temporal image data on 7 March 2012 shows an evol…
Modeling the Excitation, Propagation and Damping of Quasi-Periodic Fast Magnetosonic Waves in Realistic Coronal Active Region Magnetic Field Structures
Leon Ofman, Tongjiang Wang, Xudon Sun +1
Quasi-periodic fast propagating magnetosonic waves (QFPs) were discovered in the solar corona in EUV since the launch of SDO spacecraft more than a decade ago. The QFP waves are as…
Excitation and Damping of Slow Magnetosonic Waves in Flaring Hot Coronal Loops: Effects of Compressive Viscosity
Leon Ofman, Tongjiang Wang
Slow magnetosonic waves associated with flares were observed in coronal loops by SOHO/SUMER, SDO/AIA in various EUV bandpasses, and other instruments. The excitation and damping of…
Three-dimensional MHD modeling of propagating disturbances in fan-like coronal loops
Tongjiang Wang, Leon Ofman, Joseph M. Davila
Quasi-periodic propagating intensity disturbances (PDs) have been observed in large coronal loops in EUV images over a decade, and are widely accepted to be slow magnetosonic waves…
How the Oblique Drift Instability Alters Solar Wind Heating and Constrains the Distribution of Solar Wind Observations
Mihailo M. Martinovic, Kristopher G. Klein, Leon Ofman +6
Ion-driven plasma instability thresholds, derived from linear theory, constrain the distribution of solar observations in parameter space, defining boundaries of stable plasma para…
Quasi-Periodic Fast-Mode Wave Trains Associated with the 2015-Jun-22 M6.5 Flare in AR~12371: Observations and 3D MHD Modeling
Tongjiang Wang, Wei Liu, Leon Ofman +2
Quasi-periodic fast-propagating (QFP) wave trains are a distinctive form of magnetohydrodynamic disturbance frequently observed in the solar corona. Yet their excitation mechanism…
Coronal heating by MHD waves
Tom Van Doorsselaere, Abhishek K. Srivastava, Patrick Antolin +9
The heating of the solar chromosphere and corona to the observed high temperatures, imply the presence of ongoing heating that balances the strong radiative and thermal conduction…
Modeling the slow solar wind during the solar minimum
Leon Ofman, Maxim Kramar
During the solar minimum STEREO observations show that the three-dimensional structure of the solar corona can be described well by a tilted bi-polar magnetic configuration. The sl…
Observations and models of slow solar wind with Mg9+ ions in quiescent streamers
Leon Ofman, Lucia Abbo, Silvio Giordano
Quiescent streamers are characterized by a peculiar UV signature as pointed out by the results from the observations of the Ultraviolet and Coronograph Spectrometer (UVCS) on board…
Understanding the variability of helium abundance in the solar corona using three-fluid modeling and UV observations
Leon Ofman, Yogesh, Silvio Giordano
The variability of helium abundance in the solar corona and the solar wind is an important signature of solar activity, solar cycle, solar wind sources, as well as coronal heating…
Energy release in the solar atmosphere from a stream of infalling prominence debris
Andrew R. Inglis, Holly R. Gilbert, Leon Ofman
Recent high-resolution and high-cadence EUV imaging has revealed a new phenomenon, impacting prominence debris, where prominence material from failed or partial eruptions can impac…
Growing transverse oscillations of a multistranded loop observed by SDO/AIA
Tongjiang Wang, Leon Ofman, Joseph M. Davila +1
The first evidence of transverse oscillations of a multistranded loop with growing amplitudes and internal coupling observed by the Atomspheric Imaging Assembly (AIA) onboard the S…
Determination of transport coefficients by coronal seismology of flare-induced slow-mode waves: Numerical parametric study of 1D loop model
Tongjiang Wang, Leon Ofman
Recent studies of a flaring loop oscillation event on 2013 December 28 observed by the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO) have revealed the…
Slow magnetosonic waves and fast flows in active region loops
Leon Ofman, Tongjiang Wang, Joseph M. Davila
Recent EUV spectroscopic observations indicate that slow magnetosonic waves are present in active region (AR) loops. Some of the spectral data were also interpreted as evidence of…
Quasi-periodic Fast-mode Wave Trains Within a Global EUV Wave and Sequential Transverse Oscillations Detected by SDO/AIA
Wei Liu, Leon Ofman, Nariaki V. Nitta +4
We present the first unambiguous detection of quasi-periodic wave trains within the broad pulse of a global EUV wave (so-called "EIT wave") occurring on the limb. These wave trains…
Evidence of thermal conduction suppression in hot coronal loops: Supplementary results
Tongjiang Wang, Leon Ofman, Xudong Sun +2
Slow magnetoacoustic waves were first detected in hot (6 MK) flare loops by the SOHO/SUMER spectrometer as Doppler shift oscillations in Fe XIX and Fe XXI lines. Recently, such…
Quasi-periodic Fast-mode Magnetosonic Wave Trains Within Coronal Waveguides Associated with Flares and CMEs
Wei Liu, Leon Ofman, Brittany Broder +2
Quasi-periodic, fast-mode, propagating wave trains (QFPs) are a new observational phenomenon recently discovered in the solar corona by the Solar Dynamics Observatory with extreme…
A Truly Global Extreme Ultraviolet Wave from the SOL2017-09-10 X8.2+ Solar Flare-Coronal Mass Ejection
Wei Liu, Meng Jin, Cooper Downs +3
We report SDO/AIA observations of an extraordinary global extreme ultraviolet (EUV) wave triggered by the X8.2+ flare-CME eruption on 2017 September 10. This was one of the best EU…
Spectroscopic Diagnosis of Propagating disturbances in coronal loops: Waves or flows?
Tongjiang Wang, Leon Ofman, Joseph M. Davila
The analysis of multiwavelength properties of propagating disturbances (PDs) using Hinode/EIS observations is presented. Quasi-periodic PDs were mostly interpreted as slow magnetoa…
Eagle Pass, TX: The First American City on the Path of Totality: Organizing Eclipse Party on the Stadium
Maria D. Kazachenko, Jorge Perez-Gallego, Jennifer Miller +13
In this paper we share the experience of the U.S. National Science Foundation (NSF) National Solar Observatory (NSO) scientists, educators and public outreach officers organizing a…
Persistent Doppler shift oscillations observed with HINODE/EIS in the solar corona: spectroscopic signatures of Alfvenic waves and recurring upflows
Hui Tian, Scott W. McIntosh, Tongjiang Wang +4
Using data obtained by the EUV Imaging Spectrometer (EIS) onboard Hinode, we have per- formed a survey of obvious and persistent (without significant damping) Doppler shift oscilla…
Slow-Mode Magnetoacoustic Waves in Coronal Loops
Tongjiang Wang, Leon Ofman, Ding Yuan +3
Rapidly decaying long-period oscillations often occur in hot coronal loops of active regions associated with small (or micro-) flares. This kind of wave activity was first discover…
Exploring Standing and Reflected Slow-mode Waves in Flaring Coronal Loops: A Parametric Study Using 2.5D MHD Modeling
Tongjiang Wang, Leon Ofman, Stephen J. Bradshaw
Recent observations of reflected propagating and standing slow-mode waves in hot flaring coronal loops have spurred our investigation into their underlying excitation and damping m…
Stochastic coupling of solar photosphere and corona
Vadim M. Uritsky, Joseph M. Davila, Leon Ofman +1
The observed solar activity is believed to be driven by the dissipation of nonpotential magnetic energy injected into the corona by dynamic processes in the photosphere. The enormo…
Direct Imaging by SDO AIA of Quasi-periodic Fast Propagating Waves of ~2000 km/s in the Low Solar Corona
Wei Liu, Alan M. Title, Junwei Zhao +5
Quasi-periodic, propagating fast mode magnetosonic waves in the corona were difficult to observe in the past due to relatively low instrument cadences. We report here evidence of s…
Quasi-periodic Counter-propagating Fast Magnetosonic Wave Trains from Neighboring Flares: SDO/AIA Observations and 3D MHD Modeling
Leon Ofman, Wei Liu
Since their discovery by SDO/AIA in EUV, rapid (phase speeds of 1000 km/s), quasi-periodic, fast-mode propagating wave trains (QFPs) have been observed accompanying many solar flar…
Nonlinear Fast Magnetosonic Waves in Solar Prominence Pillars
Leon Ofman, Therese A. Kucera, C. Richard DeVore
We investigate the properties of nonlinear fast magnetosonic (NFM) waves in a solar prominence, motivated by recent high-resolution and high-cadence Hinode/SOT observations of smal…
Fast Magnetosonic Waves and Flows in a Solar Prominence Foot: Observations and Modeling
Leon Ofman, Therese A. Kucera
We study recent observations of propagating fluctuations in a prominence foot with Hinode Solar Optical Telescope (SOT) high-resolution observations in Ca~II and H alpha emission w…