Engineering topics

T S Horbury

Publications and source records attributed to T S Horbury.

3 records

NASA NTRS2024

A Rapid Sequence of Solar Energetic Particle Events Associated with a Series of Extreme-ultraviolet Jets: Solar Orbiter, STEREO-A, and Near-Earth Spacecraft Observations

A series of solar energetic electron (SEE) events was observed from 2022 November 9 to November 15 by Solar Orbiter, STEREO-A, and near-Earth spacecraft. At least 32 SEE intensity enhancements at energies >10 keV were clearly distinguishable in Solar Orbiter particle data, with 13 of them occurring on November 11. Several of these events were accompanied by 10 MeV proton and 2MeV nucleon−1 heavy-ion intensity enhancements. By combining remote-sensing and in situ data from the three viewpoints (Solar Orbiter and STEREO-A were ∼20° and ∼15° east of Earth, respectively), we determine that the origin of this rapid succession of events was a series of brightenings and jetlike eruptions detected in extreme ultraviolet (EUV) observations from the vicinity of two active regions. We find a close association between these EUV phenomena, the occurrence of hard X-ray flares, type III radio bursts, and the release of SEEs. For the most intense events, usually associated with extended EUV jets, the distance between the site of these solar eruptions and the estimated magnetic connectivity regions of each spacecraft with the Sun did not prevent the arrival of electrons at the three locations. The capability of jets to drive coronal fronts does not necessarily imply the observation of an SEE event. Two peculiar SEE events on November 9 and 14, observed only at electron energies 50 keV but rich in 1MeV nucleon−1 heavy ions, originated from slow-rising confined EUV emissions, for which the process resulting in energetic particle release to interplanetary space is unclear.

D Lario↗

NASA NTRS2019

Highly Structured Slow Solar Wind Emerging From an Equatorial Coronal Hole

At solar minimum, the solar wind is observed at high solar latitudes as a predominantly fast (> 500 km/s), highly Alfvenic, rarefied stream of plasma originating deep within coronal holes, while near the ecliptic plane it is interspersed with a more variable slow (< 500 kms) wind. The precise origins of the slow wind streams are less certain, with theories and observations supporting sources from the tips of helmet streamers, interchange reconnection near coronal hole boundaries, and origins within coronal holes with highly diverging magnetic fields. The heating mechanism required to drive the solar wind is also an open question and candidate mechanisms include Alfven wave turbulence, heating by reconnection in nanoflares, ion cyclotron wave heating and acceleration by thermal gradients1. At 1 au, the wind is mixed and evolved and much of the diagnostic structure of these sources and processes has been lost. Here we present new measurements from Parker Solar Probe at 36 to 54 solar radii that show clear evidence of slow, Alfvenic solar wind emerging from a small equatorial coronal hole. The measured magnetic field exhibits patches of large, intermittent reversals associated with jets of plasma and enhanced Poynting flux and interspersed in a smoother and less turbulent flow with near-radial magnetic field. Furthermore, plasma wave measurements suggest electron and ion velocity-space micro-instabilities that have been identified with plasma heating and thermalization processes. Our measurements suggest an impulsive mechanism associated with solar wind energization and a heating role for micro-instabilities and provide strong evidence for low latitude coronal holes as a significant contribution to the source of the slow solar wind.

Solar physics↗

NASA NTRSDate not supplied

Rapid Succession of Sep Events Associated With A Series of Euv Jets: Solar Orbiter, Stereo-A and Near-Earth Spacecraft Observations

A series of near-relativistic solar electron events was observed on November 9 to 15, 2022 by STEREO-A at 0.96 au, by near-Earth spacecraft such as ACE, Wind and SOHO at ⇠0.99 au, and by Solar Orbiter at heliocentric distances ranging from 0.59 to 0.66 au. At least 22 electron intensity enhancements at energies >10 keV were clearly distinguishable in the particle data collected by the Energetic Particle Detector (EPD) suite of instruments on board Solar Orbiter, with 12 of these events occurring on 11 November 2022. Several of these electron events were accompanied by <10 MeV proton and <⇠2 MeV/n heavy ion intensity enhancements. The origin of this rapid succession of particle events is a series of jet-like eruptions detected in extreme ultraviolet (EUV) observations from the vicinity of active region AR 13141 that were closely associated with type III bursts in the decametric-hectometric range. We find a close association between the EUV jets, type III radio bursts and the release of near relativistic electrons. The events on 9 November and late on 14 November are particularly interesting in that they were just evident at electron energies below ⇠30 keV, were rich in heavy ions with energies below ⇠1 MeV/n, associated with type III radio bursts at frequencies below ⇠1.0 MHz, and originated at EUV solar eruptions lacking a clear jet. By combining remote and in-situ data from the three viewpoints (Solar Orbiter and STEREO-A were ⇠20 degrees and ⇠15 degrees east of Earth, respectively), we analyze the origin of this sequence of events, determine the interplanetary context where they were observed, and investigate the interplanetary transport of electrons to the different spacecraft.

D Loyo↗