Search Publications
Propagating Conditions and the Time of ICME Arrival: A Comparison of the Effective Acceleration Model with ENLIL and DBEM Models
Vourlidas, Angelos; Dumbović, Mateja; Papaioannou, Athanasios +5 more
The Effective Acceleration Model (EAM) predicts the Time-of-Arrival (ToA) of the Coronal Mass Ejection (CME) driven shock and the average speed within the sheath at 1 AU. The model is based on the assumption that the ambient solar wind interacts with the interplanetary CME (ICME) resulting in constant acceleration or deceleration. The upgraded ver…
Transiting Exoplanet Survey Satellite (TESS) Observations of Flares and Quasi-Periodic Pulsations from Low-Mass Stars and Potential Impact on Exoplanets
Ramsay, Gavin; Doyle, Lauren; Doyle, J. Gerry +1 more
We have performed a search for flares and quasi-periodic pulsations (QPPs) from low-mass M-dwarf stars using Transient Exoplanet Survey Satellite (TESS) two-minute cadence data. We find seven stars that show evidence of QPPs. Using Fourier and empirical mode decomposition techniques, we confirm the presence of 11 QPPs in these seven stars with a p…
Deciphering Solar Magnetic Activity: 140 Years of the `Extended Solar Cycle' - Mapping the Hale Cycle
Velli, Marco; McIntosh, Scott W.; Srivastava, Abhishek K. +6 more
We investigate the occurrence of the "extended solar cycle" (ESC) as it occurs in a host of observational data spanning 140 years. Investigating coronal, chromospheric, photospheric, and interior diagnostics, we develop a consistent picture of solar activity migration linked to the 22-year Hale (magnetic) cycle using superposed epoch analysis (SEA…
Solar Wind Helium Abundance Heralds Solar Cycle Onset
McIntosh, Scott W.; Kasper, Justin C.; Leamon, Robert J. +1 more
We study the solar wind helium-to-hydrogen abundance's (AHe) relationship to solar cycle onset. Using OMNI/Lo data, we show that AHe increases prior to sunspot number (SSN) minima. We also identify a rapid depletion and recovery in AHe that occurs directly prior to cycle onset. This AHe shutoff happens a…
Overview of the Solar Radiation and Climate Experiment (SORCE) Seventeen-Year Mission
Woods, Thomas N.; Kopp, Greg; Harder, Jerald W. +4 more
The Solar Radiation and Climate Experiment (SORCE) was a NASA mission that operated from 2003 to 2020 to provide key climate-monitoring measurements of total solar irradiance (TSI) and solar spectral irradiance (SSI). Three important accomplishments of the SORCE mission are i) the continuation of the 42-year-long TSI climate data record, ii) the c…
Active Region Contributions to the Solar Wind over Multiple Solar Cycles
van Driel-Gesztelyi, Lidia; Green, Lucie M.; Horbury, Timothy S. +1 more
Both coronal holes and active regions are source regions of the solar wind. The distribution of these coronal structures across both space and time is well known, but it is unclear how much each source contributes to the solar wind. In this study we use photospheric magnetic field maps observed over the past four solar cycles to estimate what frac…
Simulating the Coronal Evolution of Bipolar Active Regions to Investigate the Formation of Flux Ropes
Green, L. M.; Yardley, S. L.; Mackay, D. H.
The coronal magnetic field evolution of 20 bipolar active regions (ARs) is simulated from their emergence to decay using the time-dependent nonlinear force-free field method of Mackay, Green, and van Ballegooijen (Astrophys. J. 729, 97, 2011). A time sequence of cleaned photospheric line-of-sight magnetograms, which covers the entire evolution of …
Properties of High-Frequency Type II Radio Bursts and Their Relation to the Associated Coronal Mass Ejections
Gopalswamy, N.; Yashiro, S.; Mäkelä, P. +3 more
Solar radio bursts are often early indicators of space weather events such as coronal mass ejections (CMEs). In this study, we determined the properties of a sample of 40 high-starting-frequency (≥ 150 MHz) type II radio bursts and the characteristics of the associated CMEs such as width, location and speed during 2010-2016. The high starting freq…
DH Type II Radio Bursts During Solar Cycles 23 and 24: Frequency-Dependent Classification and Their Flare-CME Associations
Joshi, Bhuwan; Cho, Kyung-Suk; Patel, Binal D. +1 more
We present the characteristics of DH type II bursts for the Solar Cycles 23 and 24. The bursts are classified according to their end frequencies into three categories: Low-Frequency Group (LFG; 20 kHz ≤ f ≤ 200 kHz), Medium-Frequency Group (MFG; 200 kHz <f ≤1 MHz), and High-Frequency Group (HFG; 1 MHz <f ≤16 MHz). We find that the sources fo…
Irradiance Variations of the Sun and Sun-Like Stars - Overview of Topical Collection
Kopp, Greg; Shapiro, Alexander
This topical collection summarizes recent advances in observing and modeling irradiance variations of the Sun and Sun-like stars, emphasizing the links between surface magnetic fields and the resulting solar and stellar variability. In particular, the articles composing this collection summarize recent progress in i) solar-irradiance measurements;…