151 citations · 467 across the 17 of their papers we have counts for
19 papers
Unusual Circumstances of the 2024 June 8 GLE
Nat Gopalswamy, Pertti Makela, Hong Xie +3
Ground Level Enhancement (GLE) in large solar energetic particle (SEP) events is indicative of protons accelerated to GeV energies. Almost all GLE events are associated with sustai…
Solar Cycle Variation of Sustained Gamma Ray Emission from the Sun
Nat Gopalswamy, Pertti Mäkelä, Seiji Yashiro +3
We investigated the occurrence rate of the sustained gamma ray emission (SGRE) events from the Sun using data obtained by Fermi Large Area Telescope (LAT) since its launch in 2008.…
Third Harmonic Structure in an Interplanetary Type II Radio Burst and Other Energetic Phenomena During the 2024 September 14 Solar Eruption
Nat Gopalswamy, Pertti Makela, Hong Xie +2
We report on the observation of first, second, and third harmonic components during an interplanetary (IP) type II solar radio burst observed on 2024 September 14 by the radio inst…
The Longest Duration SGRE Event in Solar Cycle 25
Nat Gopalswamy, Pertti Makela, Hong Xie +2
Solar Cycle (SC) 24 was the weakest in the space age, yet it produced many sustained gamma ray emission (SGRE) events from the Sun. Solar cycle (SC) 25, which is a bit stronger tha…
Multispacecraft Observations of the 2024 September 9 Backside Solar Eruption that Resulted in a Sustained Gamma Ray Emission Event
Nat Gopalswamy, Pertti Mäkelä, Sachiko Akiyama +6
We report on the 2024 September 9 sustained gamma ray emission (SGRE) event observed by the Large Area Telescope (LAT) onboard the Fermi satellite. The event was associated with a…
Solar Cycle Variation of Axial Orientations and Favorable Locations of Eruptive MFRs
Hong Xie, Nat Gopalswamy, Sachiko Akiyama +2
Using multi-viewpoint observations from STEREO and SOHO during three solar cycles from 23 to 25, we study the magnetic flux rope (MFR) structures of coronal mass ejections (CMEs) n…
Implications of the abundance of halo coronal mass ejections for the strength of solar cycle 25
Nat Gopalswamy, Grzegorz Michalek, Seiji Yashiro +3
We assess the relative strength of solar cycle (SC) 25 with respect to SCs 23 and 24 based on the abundance of halo coronal mass ejections (CMEs). We make use of the halo CME datab…
The SOHO LASCO CME Catalog -- Version 2
Nat Gopalswamy, Grzegorz Michałek, Seiji Yashiro +4
This paper provides an update on the coronal mass ejection (CME) catalog maintained at the CDAW Data Center, NASA Goddard Space Flight Center (https://cdaw.gsfc.nasa.gov/CME_list).…
What is Unusual about the Third Largest Geomagnetic Storm of Solar Cycle 24?
N. Gopalswamy, S. Yashiro, S. Akiyama +4
We report on the solar and interplanetary (IP) causes of the third largest geomagnetic storm (2018 August 26) in solar cycle 24. The underlying coronal mass ejection (CME) originat…
Direct First PSP Observation of the Interaction of Two Successive Interplanetary Coronal Mass Ejections in November 2020
Teresa Nieves-Chinchilla, Nathalia Alzate, Hebe Cremades +18
We investigate the effects of the evolutionary processes in the internal magnetic structure of two interplanetary coronal mass ejections (ICMEs) detected in situ between 2020 Novem…
Solar Activity and Space Weather
Nat Gopalswamy, Pertti Mäkelä, Seiji Yashiro +2
After providing an overview of solar activity as measured by the sunspot number (SSN) and space weather events during solar cycles (SCs) 21-24, we focus on the weak solar activity…
The shock driving capability of a CME inferred from multiwavelength observations
Fithanegest Kassa Dagnew, Nat Gopalswamy, Solomon Belay Tessema +4
The radial speed of a coronal mass ejection (CME) determines the shock-driving capability of a CME as indicated by the presence of a type II radio burst. Here we report on the Apri…
On the properties of solar energetic particle events associated with metric type II radio bursts
Pertti Mäkelä, Nat Gopalswamy, Hong Xie +3
Metric type II solar radio bursts and solar energetic particles (SEPs) are both associated with shock fronts driven by coronal mass ejections (CMEs) in the solar corona. Recent stu…
A Sun-to-Earth analysis of magnetic helicity of the 17-18 March 2013 interplanetary coronal mass ejection
Sanchita Pal, Nat Gopalswamy, Dibyendu Nandy +4
We compare the magnetic helicity in the 17-18 March 2013 interplanetary coronal mass ejection (ICME) flux-rope at 1 AU and in its solar counterpart. The progenitor coronal mass eje…
The 2012 July 23 Backside Eruption: An Extreme Energetic Particle Event?
Nat Gopalswamy, Seiji Yashiro, Neeharika Thakur +3
The backside coronal mass ejection (CME) of 2012 July 23 had a short Sun to Earth shock transit time (18.5 hours). The associated solar energetic particle (SEP) event had a >10 MeV…
The Mild Space Weather in Solar Cycle 24
Nat Gopalswamy, Sachiko Akiyama, Seiji Yashiro +3
The space weather is extremely mild during solar cycle 24: the number of major geomagnetic storms and high-energy solar energetic particle events are at the lowest since the dawn o…
Major Solar Eruptions and High Energy Particle Events during Solar Cycle 24
N. Gopalswamy, H. Xie, S. Akiyama +2
We report on a study of all major solar eruptions that occurred on the front-side of the Sun during the rise to peak phase of cycle 24 (first 62 months) in order to understand the…
Anomalous Expansion of Coronal Mass Ejections during Solar Cycle 24 and its Space Weather Implications
Nat Gopalswamy, Sachiko Akiyama, Seiji Yashiro +3
The familiar correlation between the speed and angular width of coronal mass ejections (CMEs) is also found in solar cycle 24, but the regression line has a larger slope: for a giv…
Large Geomagnetic Storms Associated with Limb Halo Coronal Mass Ejections
Nat Gopalswamy, Seiji Yashiro, Hong Xie +2
Solar cycle 23 witnessed the observation of hundreds of halo coronal mass ejections (CMEs), thanks to the high dynamic range and extended field of view of the Large Angle and Spect…