Found 14 entries in the Bibliography.

Showing entries from 1 through 14


The Evolution of a Pitch-Angle \textquotedblleftBite-Out\textquotedblright Scattering Signature Caused by EMIC Wave Activity: A Case Study

Electromagnetic ion cyclotron (EMIC) waves are understood to be one of the dominant drivers of relativistic electron loss from Earth\textquoterights radiation belts. Theory predicts that the associated gyroresonant wave-particle interaction results in a distinct energy-dependent \textquotedblleftbite-out\textquotedblright signature in the normalized flux distribution of electrons as they are scattered into the loss cone. We identify such signatures along with the responsible EMIC waves captured in situ by the Van Allen Probe ...

Bingley, L.; Angelopoulos, V.; Sibeck, D.; Zhang, X.; Halford, A.;

YEAR: 2019     DOI: 10.1029/2018JA026292

Van Allen Probes

Generation of EMIC Waves and Effects on Particle Precipitation During a Solar Wind Pressure Intensification with B z >

During geomagnetic storms, some fraction of the solar wind energy is coupled via reconnection at the dayside magnetopause, a process that requires a southward interplanetary magnetic field Bz. Through a complex sequence of events, some of this energy ultimately drives the generation of electromagnetic ion cyclotron (EMIC) waves, which can then scatter energetic electrons and ions from the radiation belts. In the event described in this paper, the interplanetary magnetic field remained northward throughout the event, a condit ...

Lessard, Marc; Paulson, Kristoff; Spence, Harlan; Weaver, Carol; Engebretson, Mark; Millan, Robyn; Woodger, Leslie; Halford, Alexa; Horne, Richard; Rodger, Craig; Hendry, Aaron;

YEAR: 2019     DOI: 10.1029/2019JA026477

Van Allen Probes


Pitch Angle Scattering and Loss of Radiation Belt Electrons in Broadband Electromagnetic Waves

A magnetic conjunction between Van Allen Probes spacecraft and the Balloon Array for Radiation-belt Relativistic Electron Losses (BARREL) reveals the simultaneous occurrence of broadband Alfv\ enic fluctuations and multi-timescale modulation of enhanced atmospheric X-ray bremsstrahlung emission. The properties of the Alfv\ enic fluctuations are used to build a model for pitch angle scattering in the outer radiation belt on electron gyro-radii scale field structures. It is shown that this scattering may lead to the transport ...

Chaston, C.; Bonnell, J.; Halford, A.; Reeves, G.; Baker, D.; Kletzing, C.; Wygant, J.;

YEAR: 2018     DOI: 10.1029/2018GL079527

Alfven waves; drift-bounce resonance; energetic particles; Geomagnetic storms; pitch-angle scattering; Radiation belts; Van Allen Probes

Ion Injection Triggered EMIC Waves in the Earth\textquoterights Magnetosphere

We present Van Allen Probe observations of electromagnetic ion cyclotron (EMIC) waves triggered solely due to individual substorm-injected ions in the absence of storms or compressions of the magnetosphere during 9 August 2015. The time at which the injected ions are observed directly corresponds to the onset of EMIC waves at the location of Van Allen Probe A (L = 5.5 and 18:06 magnetic local time). The injection was also seen at geosynchronous orbit by the Geostationary Operational Environmental Satellite and Los Alamos Nat ...

Remya, B.; Sibeck, D.; Halford, A.; Murphy, K.; Reeves, G.; Singer, H.; Wygant, J.; Perez, Farinas; Thaller, S.;

YEAR: 2018     DOI: 10.1029/2018JA025354

EMIC waves; Ion injections; magnetic dip; substorm; Van Allen Probes


EMIC waves and associated relativistic electron precipitation on 25-26 January 2013

Using measurements from the Van Allen Probes and the Balloon Array for RBSP Relativistic Electron Losses (BARREL), we perform a case study of electromagnetic ion cyclotron (EMIC) waves and associated relativistic electron precipitation (REP) observed on 25\textendash26 January 2013. Among all the EMIC wave and REP events from the two missions, the pair of the events is the closest both in space and time. The Van Allen Probe-B detected significant EMIC waves at L = 2.1\textendash3.9 and magnetic local time (MLT) = 21.0\texten ...

Zhang, Jichun; Halford, Alexa; Saikin, Anthony; Huang, Chia-Lin; Spence, Harlan; Larsen, Brian; Reeves, Geoffrey; Millan, Robyn; Smith, Charles; Torbert, Roy; Kurth, William; Kletzing, Craig; Blake, Bernard; Fennel, Joseph; Baker, Daniel;

YEAR: 2016     DOI: 10.1002/2016JA022918

BARREL; EMIC waves; FFT; Geomagnetic storm; relativistic electron precipitation (REP); Van Allen Probes

BARREL observations of a Solar Energetic Electron and Solar Energetic Proton event

During the second Balloon Array for Radiation Belt Relativistic Electron Losses (BARREL) campaign two solar energetic proton (SEP) events were observed. Although BARREL was designed to observe X-rays created during electron precipitation events, it is sensitive to X-rays from other sources. The gamma lines produced when energetic protons hit the upper atmosphere are used in this paper to study SEP events. During the second SEP event starting on 7 January 2014 and lasting \~ 3 days, which also had a solar energetic electron ( ...

Halford, A.; McGregor, S.; Hudson, M.; Millan, R.; Kress, B.;

YEAR: 2016     DOI: 10.1002/2016JA022462

BARREL; electron precipitation; proton precipitation; Solar Energetic Electrons; Solar Energetic Protons; Solar storm; Van Allen Probes


Observations of coincident EMIC wave activity and duskside energetic electron precipitation on 18-19 January 2013

Electromagnetic ion cyclotron (EMIC) waves have been suggested to be a cause of radiation belt electron loss to the atmosphere. Here simultaneous, magnetically conjugate measurements are presented of EMIC wave activity, measured at geosynchronous orbit and on the ground, and energetic electron precipitation, seen by the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) campaign, on two consecutive days in January 2013. Multiple bursts of precipitation were observed on the duskside of the magnetosphere at ...

Blum, L.; Halford, A.; Millan, R.; Bonnell, J.; Goldstein, J.; Usanova, M.; Engebretson, M.; Ohnsted, M.; Reeves, G.; Singer, H.; Clilverd, M.; Li, X.;

YEAR: 2015     DOI: 10.1002/2015GL065245

electron precipitation; EMIC waves; Radiation belts; Van Allen Probes

Global-scale coherence modulation of radiation-belt electron loss from plasmaspheric hiss

Over 40 years ago it was suggested that electron loss in the region of the radiation belts that overlaps with the region of high plasma density called the plasmasphere, within four to five Earth radii1, 2, arises largely from interaction with an electromagnetic plasma wave called plasmaspheric hiss3, 4, 5. This interaction strongly influences the evolution of the radiation belts during a geomagnetic storm, and over the course of many hours to days helps to return the radiation-belt structure to its \textquoteleftquiet\textqu ...

Breneman, A.; Halford, A.; Millan, R.; McCarthy, M.; Fennell, J.; Sample, J.; Woodger, L.; Hospodarsky, G.; Wygant, J.; Cattell, C.; Goldstein, J.; Malaspina, D.; Kletzing, C.;

YEAR: 2015     DOI: 10.1038/nature14515

Magnetospheric physics; Van Allen Probes

A Summary of the BARREL Campaigns: Technique for studying electron precipitation

The Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) studies the loss of energetic electrons from Earth\textquoterights radiation belts. BARREL\textquoterights array of slowly drifting balloon payloads was designed to capitalize on magnetic conjunctions with NASA\textquoterights Van Allen Probes. Two campaigns were conducted from Antarctica in 2013 and 2014. During the first campaign in January and February of 2013, there were three moderate geomagnetic storms with Sym-Hmin < -40 nT. Similarly, two mino ...

Woodger, L.; Halford, A.; Millan, R.; McCarthy, M.; Smith, D.; Bowers, G.; Sample, J.; Anderson, B.; Liang, X.;

YEAR: 2015     DOI: 10.1002/2014JA020874

electron precipitation; event timing; gamma ray burst; multi-point observation; Radiation belts; Van Allen Probes; x-ray spectroscopy

Simulation of ULF wave modulated radiation belt electron precipitation during the 17 March 2013 storm

Balloon-borne instruments detecting radiation belt precipitation frequently observe oscillations in the mHz frequency range. Balloons measuring electron precipitation near the poles in the 100 keV to 2.5 MeV energy range, including the MAXIS, MINIS, and most recently the BARREL balloon experiments, have observed this modulation at ULF wave frequencies [e.g. Foat et al., 1998; Millan et al., 2002; Millan, 2011]. Although ULF waves in the magnetosphere are seldom directly linked to increases in electron precipitation since the ...

Brito, T.; Hudson, M.; Kress, B.; Paral, J.; Halford, A.; Millan, R.; Usanova, M.;

YEAR: 2015     DOI: 10.1002/2014JA020838

precipitation; Radiation belts; Ulf; ULF modulation

BARREL observations of an ICME-Shock impact with the magnetosphere and the resultant radiation belt electron loss.

The Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) mission of opportunity working in tandem with the Van Allen Probes was designed to study the loss of radiation belt electrons to the ionosphere and upper atmosphere. BARREL is also sensitive to X-rays from other sources. During the second BARREL campaign the Sun produced an X-class flare followed by a solar energetic particle event (SEP) associated with the same active region. Two days later on 9 January 2014 the shock generated by the coronal mass ej ...

Halford, A.; McGregor, S.; Murphy, K.; Millan, R.; Hudson, M.; Woodger, L.; Cattel, C.; Breneman, A.; Mann, I.; Kurth, W.; Hospodarsky, G.; Gkioulidou, M.; Fennell, J.;

YEAR: 2015     DOI: 10.1002/2014JA020873

BARREL; Van Allen Probes

EMIC waves and plasmaspheric and plume density: CRRES results

Electromagnetic ion cyclotron (EMIC) waves frequently occur during geomagnetic storms, specifically during the main phase and 3\textendash6 days following the minimum Sym - H value. EMIC waves contribute to the loss of ring current ions and radiation belt MeV electrons. Recent studies have suggested that cold plasma density structures found inside the plasmasphere and plasmaspheric plumes are important for the generation and propagation of EMIC waves. During the CRRES mission, 913 EMIC wave events and 124 geomagnetic storms ...

Halford, A.; Fraser, B.; Morley, S.;

YEAR: 2015     DOI: 10.1002/2014JA020338

EMIC waves; Geomagnetic storms; plasmasphere; plasmaspheric plumes


The Balloon Array for RBSP Relativistic Electron Losses (BARREL)

BARREL is a multiple-balloon investigation designed to study electron losses from Earth\textquoterights Radiation Belts. Selected as a NASA Living with a Star Mission of Opportunity, BARREL augments the Radiation Belt Storm Probes mission by providing measurements of relativistic electron precipitation with a pair of Antarctic balloon campaigns that will be conducted during the Austral summers (January-February) of 2013 and 2014. During each campaign, a total of 20 small (\~20 kg) stratospheric balloons will be successively ...

Millan, R.; McCarthy, M.; Sample, J.; Smith, D.; Thompson, L.; McGaw, D.; Woodger, L.; Hewitt, J.; Comess, M.; Yando, K.; Liang, A.; Anderson, B.; Knezek, N.; Rexroad, W.; Scheiman, J.; Bowers, G.; Halford, A.; Collier, A.; Clilverd, M.; Lin, R.; Hudson, M.;

YEAR: 2013     DOI: 10.1007/s11214-013-9971-z

RBSP; Van Allen Probes

New conjunctive CubeSat and balloon measurements to quantify rapid energetic electron precipitation

Relativistic electron precipitation into the atmosphere can contribute significant losses to the outer radiation belt. In particular, rapid narrow precipitation features termed precipitation bands have been hypothesized to be an integral contributor to relativistic electron precipitation loss, but quantification of their net effect is still needed. Here we investigate precipitation bands as measured at low earth orbit by the Colorado Student Space Weather Experiment (CSSWE) CubeSat. Two precipitation bands of MeV electrons w ...

Blum, L.; Schiller, Q.; Li, X.; Millan, R.; Halford, A.; Woodger, L.;

YEAR: 2013     DOI: 10.1002/2013GL058546

CubeSats; precipitation; Radiation belts; Van Allen Probes