Dr. ALEXA (She/Her) J HALFORD

Dr. ALEXA (She/Her) J HALFORD

  • Rsch AST, Atmospheres and Ionospheres
  • 301.286.7794
  • NASA/GSFC
  • Mail Code: 675
  • Greenbelt , MD 20771
  • Employer: NASA
  • Brief Bio

    I am currently a space physics researcher at NASA Goddard Space Flight Center working with the petitSat mission. I started researching waves in Earth's magnetosphere as an undergraduate at Augsburg College with Mark Engebretson using ground based magnetometers in the Arctic and Antarctic. I moved away from waves to focus on geomagnetic storms and substorms during my masters at the University of Colorado Boulder with Dan Baker but returned once more to waves with my PhD at University of Newcastle NSW Australia working under Brian Fraser. My PhD thesis was on Electromagnetic Ion Cyclotron (EMIC) waves during the CRRES mission and their relationship to the plasmasphere and radiation belts. During my postdoc at Dartmouth college I worked on  the BARREL mission I have moved down the field line (from a space perspective) and now look at the population of particles lost due to these interactions and their impact on the ionosphere and upper atmosphere.

    Research Interests

    Particle dynamics, their drivers, and their impacts

    Much of my research has focused on the drivers (e.g. waves) of particle dynamics and their impact through loss of the particles to the ionosphere and upper atmosphere, as well as their direct impact on technology. 

    The Balloon Array for Relativistic Radiation Belt Electron Loss (BARREL)

    During my postdoc I worked with the Balloon Array for Relativistic Radiation belt Electron Losses (BARREL) mission. While the mission has ended, the research has not. We continue to use this unique data set to continue to explore the spatial and temporal dynamics of particle loss from the Sun and Magnetosphere into the ionosphere and upper atmosphere.

    Papers from this work: 


     

    Current Projects

    petitSat

    petitSat is a 6U CubeSat designed to look at plasmaspheric bubbles and blobs. We are hoping to launch in 2021 from the international space station. 


    Selected Publications:


    J. Klenzing, R.L. Davidson, S.L. Jones, C. Martinis, K.A. Zawdie, G.D. Earle, J.M. Smith, A.J. Halford, S. Noel, N. Paschalidis, R.F. Pfaff, E. Robertson, The petitSat mission – Science goals and instrumentation, Advances in Space Research, Volume 66, Issue 1, 2020, Pages 107-115, ISSN 0273-1177, https://doi.org/10.1016/j.asr.2019.12.013.

    Positions/Employment

    7/2012 - 10/2017

    PostDoc/Space Grant Visiting Scientist

    Dartmouth College, Hanover NH

    During my postdoc I worked with the BARREL mission.

     

    Papers from this work: 

     

     

     

    11/2017 - 10/2019

    Research Staff Member

    The Aerospace Corporation, Chantilly VA

    I worked on space weather impacts from magnetospheric radiation populations with the REACH satellite constellation. 


    Selected Publications:


    Burrell, A. G., Halford, A., Klenzing, J., Stoneback, R. A., Morley, S. K., Annex, A. M., et al. (2018). Snakes on a spaceship—An overview of Python in heliophysics. Journal of Geophysical Research: Space Physics, 123, 10,384– 10,402. https://doi.org/10.1029/2018JA025877


    Rae, I. J., Murphy, K. R., Watt, C. E. J., Halford, A. J., Mann, I. R., Ozeke, L. G., … Singer, H. J. (2018). The role of localized compressional ultra‐low frequency waves in energetic electron precipitation. Journal of Geophysical Research: Space Physics, 123, 1900– 1914. https://doi.org/10.1002/2017JA024674


    J.T. Rudd, D.M. Oliveira, A. Bhaskar, A.J. Halford, How do interplanetary shock impact angles control the size of the geoeffective magnetosphere?, Advances in Space Research, Volume 63, Issue 1, 2019, Pages 317-326, ISSN 0273-1177, https://doi.org/10.1016/j.asr.2018.09.013.


    Chaston, C. C., Bonnell, J. W., Halford, A. J., Reeves, G. D., Baker, D. N., Kletzing, C. A., & Wygant, J. R. (2018). Pitch angle scattering and loss of radiation belt electrons in broadband electromagnetic waves. Geophysical Research Letters, 45, 9344– 9352. https://doi.org/10.1029/2018GL079527


    Bingley, L., Angelopoulos, V., Sibeck, D., Zhang, X., & Halford, A. (2019). The evolution of a pitch‐angle “bite‐out” scattering signature caused by EMIC wave activity: A case study. Journal of Geophysical Research: Space Physics, 124, 5042– 5055. https://doi.org/10.1029/2018JA026292


    Alexa J. Halford, Adam C. Kellerman, Katherine Garcia-Sage, Jeffrey Klenzing, Brett A. Carter, Ryan M. McGranaghan, Timothy Guild, Consuelo Cid, Carl J. Henney, Natalia Yu. Ganushkina, Angeline G. Burrell, Mike Terkildsen, Daniel T. Welling, Sophie A. Murray, K. D. Leka, James P. McCollough, Barbara J. Thompson, Antti Pulkkinen, Shing F. Fung, Suzy Bingham, Mario M. Bisi, Michael W. Liemohn, Brian M. Walsh, Steven K. Morley, Application usability levels: a framework for tracking project product progress, J. Space Weather Space Clim. 9 A34 (2019) DOI: 10.1051/swsc/2019030


    Claudia Medeiros and V. M. Souza and L. E. A. Vieira and D. G. Sibeck and A. J. Halford and S.-B. Kang and L. A. Da Silva and L. R. Alves and J. P. Marchezi and R. S. Dallaqua and P. R. Jauer and M. Rockenbach and O. Mendes and M. V. Alves and A. Dal Lago and M.-C. Fok and S. G. Kanekal and D. N. Baker and C. A. Kletzing, On the Contribution of EMIC Waves to the Reconfiguration of the Relativistic Electron Butterfly Pitch Angle Distribution Shape on 2014 September 12: A Case Study, The Astrophysical Journal, vol 872, p. 36, American Astronomical Society, Feb. 2019

    11/2019 - Present

    Research Scientist

    Goddard Space Flight Center NASA Code 675, Greenbelt

    I am within the Ionosphere-Thermosphere-Mesosphere lab. I am currently the deputy PI of petitSat which will launch hopefully in 2021 from the international space station. 


    Selected publications:

    Remya, B., Sibeck, D. G., Ruohoniemi, J. M., Kunduri, B., Halford, A. J., Reeves, G. D., & Reddy, V. (2020). Association between EMIC wave occurrence and enhanced convection periods during ion injections. Geophysical Research Letters, 47, e2019GL085676. https://doi.org/10.1029/2019GL085676


    Cid, C., Guerrero, A., Saiz, E., Halford, A. J., & Kellerman, A. C. (2020). Developing the LDi and LCi geomagnetic indices, an example of application of the AULs framework. Space Weather, 18, e2019SW002171. https://doi.org/10.1029/2019SW002171


    Shumko, Mykhaylo and Johnson, Arlo and O’Brien, Thomas Paul and Turner, Drew L. and Greeley, Ashley D and Sample, John and Blake, J Bernard and Blum, Lauren W and Halford, Alexa J., Statistical Properties of Electron Curtain Precipitation Estimated with AeroCube-6, Earth and Space Science Open Archive, 17, 2020, 10.1002/essoar.10503661.1


    Thiago V. Brito, Alexa J. Halford, Scot R. Elkington, Chapter 2 - Ultralow frequency-wave induced losses, Editor(s): Allison N. Jaynes, Maria E. Usanova, The Dynamic Loss of Earth's Radiation Belts, Elsevier, 2020, Pages 29-48, ISBN 9780128133712, https://doi.org/10.1016/B978-0-12-813371-2.00002-0.


    J. Klenzing, R.L. Davidson, S.L. Jones, C. Martinis, K.A. Zawdie, G.D. Earle, J.M. Smith, A.J. Halford, S. Noel, N. Paschalidis, R.F. Pfaff, E. Robertson, The petitSat mission – Science goals and instrumentation, Advances in Space Research, Volume 66, Issue 1, 2020, Pages 107-115, ISSN 0273-1177, https://doi.org/10.1016/j.asr.2019.12.013.



    Education

    PhD 2012, The University of Newcastle Australia

    Masters 2007 CU Boulder 

    BA double major Math/Physics graduated from honors & McNair program Augsburg University

    Professional Societies

    The American Geophysical Union, 2002 - Present
    The American Meteorological Society, 2019 - Present

    Professional Service

    My service to the larger scientific community has come primarily in four parts:
    1) Service to mission coordination and mission leadership which include planing and coordinating projects with other agencies and scientists to conduct pioneering projects, developing experimental investigations, and planning the appropriate approach for data acquisition to ensure the right types of data where collected to help resolve outstanding critical scientific problems.
    2) Organizing conferences, workshops, sessions, and seminars for the dissemination of presentable results, and to encourage new collaborative research.

    3) Service on professional committees which have allowed me the opportunity to help guide the field through recommending future proposal calls, encourage engagement of the scientific community with their political representatives in the hopes of increased funding for the field, and through recognizing some of our outstanding scientific peers.
    4) Service to the science community at large and service to my current place of employment through serving as a reviewer for papers and reviewer and panelist for grant opportunities as well as an advocate for the wonderful science completed at my place of employment.

     

    Service to Mission coordination and Mission leadership

    • Led BARREL collaborations and contact to multiple missions (both US based and interna- tional) including NASA’s Van Allen Probes (US-NASA), Cluster (EU), LOMONOSOV (Russia), ABOVE2 (CA), Firebird (US-UNH and MSU ), AC6 (US-Aerospace Corporation), and CSSWE (US-LASP CU Boulder) as well as with the larger scientific community. I was the BARREL lead for the daily meetings between BARREL and the Van Allen Probe’s instru- ments teams to determine data collection and retrieval during the BARREL campaigns. Other satellite, ground, and CubeSat missions also attended these meetings to determine when they should collect and download data to ensure the correct data type for answering critical science questions for the 2012-2013, 2013-2014, and the August 2015 and 2016 campaigns.
    • Helped organize and plan the EFW/BARREL workshop and follow up science meetings, 2013- 2014
    • Successfully conceived, planed, and developed experimental investigations and proposed for EISCAT radar time with strong international collaborations for experimental investigations taking advantage of conjugate observations with FIREBIRD, Van Allen Probes, and BARREL for both the 2015 and 2016 campaigns. This work addressed and attempted to resolve scientific problems with identifying the in situ source and scale size of microbursts and other radiation belt electron precipitation events.
    • Advocated for the BARREL mission to the larger scientific community and public through near real time dissemination of BARREL progress, observations, and results through the BARREL blog (both one for the public and one for the scientific community), Facebook page, and twitter accounts. December 2012 - present
    • Advocated for the BARREL mission to the larger scientific community by presenting and running informal sessions at GEM and AGU on how to use the BARREL data analysis software, how to interpret the BARREL data, and how to identify events vs contamination/noise in the novel BARREL data set.
    • Advocated for the BARREL mission to the public through multiple public lectures, a temporary exhibit at a museum, and the creation of a mission short film which was uploaded to the NASA YouTube channel.

    Organizing conference/workshops and sessions/seminars

    • Program Committee for AGU Chapman conference on ”Scientific Challenges Pertaining to Space Weather Forecasting Including Extremes”
    • Chair of an AGU Fall 2018 Session titled ”Quantitative Understanding of Particle Dynamics in Earth’s Radiation Belts”
    • Co - convener and chair of an Fall 2018 AGU session titled ”The Application Usability Level (AUL) framework: a standard measure of progress to benefit heliophysics research, and the needs of our society.” with Adam Kellerman, and Jeffery Klenzing.
    • Co - convener of an AGU Fall 2018 Session titled ”Challenges in Extreme Space Weather Research: Science, Applications, and Policies” with Denny Oliveira, Noe Lugaz, and Sophie Murray
    • Co - convener of an AGU Fall 2018 Session titled ”Application Development in Python for Solar and Space Physics” with Alex DeWolfe and D Aaron Roberts
    • Co - convener and chair of an AGU Fall 2018 Union Session titled ”The Challenges of Recog- nizing Implicit Bias in Earth and Space Sciences and Strategies for Minimizing its Impact in the Coming Decades of the AGU” with Hazel Bain and Blair Schneider
    • On the Program Committee for the Chapman Conference on Scientific Challenges Pertaining to Space Weather Forecasting including Extremes
    • Co-Convener and Chair of a plenary at the TESS meeting in VA, 2018 titled ”Unconscious bias in Space Physics: what is it and what are the solutions?” with K Garcia Sage, N. Vail, Y. Collado-Vega
    • • Co - convener and chair of an Fall 2017 AGU session titled ”Assessment of Space Environment Models and Data: Validation Metrics, Frameworks, and Applications” with Adam Kellerman, Katherine Garcia-Sage, and Jeffery Klenzing.
    • Organizer for a mini workshop on Assessment of Understanding and Quantifying Progress Toward Science Understanding and Operational Readiness group at the International Forum for Space Weather Capabilities Assessment working group the Sunday before AGU
    • Co-lead with Adam Kellerman the Assessment of Understanding and Quantifying Progress Toward Science Understanding and Operational Readiness group at the International Forum for Space Weather Capabilities Assessment Workshop run by the CCMC and LWS. 2016 - present. This includes leading and conducting studies on tracking the progress of our field, development of application usability levels, and development of a framework for dissemination of information including metric and validation techniques and progress.
    • On the organizing committee for the Inner Magnetosphere Coupling III meeting held March 2015 at University of California Los Angeles
    • Co-lead with Adam Kellerman a special GEM 2017 session on Assessment of Understanding and Quantifying Progress Toward Science Understanding and Operational Readiness
    • AGU Fall 2016 session ”Understanding the scale and significance of ULF modulation of higher frequency wave power and energetic particle loss rates” with Aaron Breneman and Chris Colpitts
    • • Co-Convener and chair of a joint CEDAR GEM 2016 focus group ”Particle Precipitation and the Effects on Earth’s Atmosphere” with Kyle Murphy, Roger Varney, Stephen Kaeppler, and Allison Jaynes.
    • Co-Convener and chair of the Comparative studies of the storm-time inner magnetosphere for the Fall 2015 AGU conference. with Matina Gkioulidou, Drew Turner, and Philip Valek.
    • • Co-Convener and chair of the Multi-point Observations in the Inner Magnetosphere: System- wide Understanding of Particle Transport, Energization, and Loss at the Fall 2014 AGU con- ference with Matina Gkioulidou and Drew Turner.
    • Ran the Dartmouth Spring Plasma Physics Seminar series, 2013, 2014, 2015
    • Chaired session for Fall AGU 2013 Buildup and Dynamics of Ring Current and Radiation Belts at Earth II session.
    • Space Physics & Aeronomy Program Committee session liaison for the Outstanding Student Paper Award for sections SM23C, SM24B, SM33A for the Fall AGU 2013 meeting

    Professional Organization Membership and Committees

    • Serving on the GEM Metrics and Validation Standing Resource Group 2020
    • Served on NASA LWS TR&T steering committee 2016
    • Member of the American Geophysical Union 2002 - present
      • Serving on the AGU SPA Fellows Committee 2017, 2018, Chair 2019, 2020
      • Serving on the AGU SPA Advocacy committee. 2017 - 2019


    Service to Community/institute

    • Presented to the AGU Fellows nomination task force on implicit bias and how to write a non-gendered nomination packages. 2017, 2018
    • Panelist on the GEM student night panel about Ethics 2017
    • Goddard point of contact/organizer for the United States Naval Academy- Goddard summer student research program 2017
    • Code 674 point of contact for nugget slides for codes 600, 100, and headquarters, working with Dr. Alex Young 2016 - 2017
    • Co-guest Editor of the JGR Energetic Electron Loss and its Impacts on the Atmosphere special issue
    • Served on NASA and NSF grant review panels as a write in reviewer, panelist and as chair.
    • Active referee for a number of journals including Geophysical Reviews, the Journal of Geophysical Research, Geophysical Research Letters, Annales Geophysicae, Physics of Plasmas, EOS, and Nature Communications.

    Awards

    • NASA Peer Award for setting up Science Fridays, a new networking event to enable cross pollination of ideas and innovative thinking throughout Goddard, September 2020
    • NASA Special Act Award For serving in a critical leadership role as the ARTEMIS Point of Contact in 670, and connecting Heliophysics to the larger efforts at the Center in support of human exploration of the Moon and Moon to Mars.August 2020
    • 2018 Editor’s Citation for Excellence in Refereeing for Reviews of Geophysics
    • The Aerospace Corporation ”Strategic Imperative Hero pin” for growth 2018
    • Goddard Heliophysics Science Division Peer award 2017
    • Augsburg First Decade Award 2013 “The First Decade Award is presented to Augsburg graduates of the past 10 years who have made significant progress in their professional achievements and contributions to the community, and in so doing exemplify the mission of the College: to prepare future leaders in service to the world.” - Augsburg College (now Augsburg University)
    • Dartmouth Young Visiting Scientist 2012 - 2013.
    • Best Science Story at the 10th annual New Year’s Poster Party at NASA Goddard 2017
    • Finalist in the Three min. thesis competition, Newcastle University, Callaghan Australia June 2010
    • Winner of the Three min. thesis competition in the College round Newcastle University, Callaghan Australia, June 2010
    • Voted Best Poster by participating students at Science Research Expo, Newcastle University, Callaghan Australia June 2008
    • BA Graduation with honors and from the McNair program, Augsburg College Minneapolis MN May 2003
    • Received Outstanding student paper award for poster at Spring 2002 AGU conference
    • Student in the McNair Program. A program to prepare minority, underrepresented, and first generation low income students for post graduate studies through research opportunities and other academic activities. Admission is based on academic standing. 2001-2003
    • Augsburg Tuition Grant 2002-2003
    • President of SPS and President of Unbounded (math club) 2002-2003
    • Honorable mention in MCM Mathematical Modeling Contest
    • Bev Durkee Mathematics Scholarship 2001-2003
    • Leif Sverdrup Physics Scholarship 2000-2003
    • Early Advantage Regents’ Scholarship1999-2003
    • Augsburg Faculty Leadership Scholarship 1999-2003
    • T. Hanwick Science Scholarship 1999-2003
    • Prime Church Scholarship 1999-2003
    • Prime Augsburg match 1999-2003

    Publications

    Refereed

    Klenzing, J., R. Davidson, S. Jones, et al. C. Martinis, K. Zawdie, G. Earle, J. Smith, A. Halford, S. Noel, N. Paschalidis, R. Pfaff, and E. Robertson. 2020. "The petitSat Mission – Science Goals and Instrumentation." Advances in Space Research, 66 (1): 107-115 [10.1016/j.asr.2019.12.013]

    Remya, B., D. Sibeck, J. Ruohoniemi, et al. B. Kunduri, A. Halford, G. Reeves, and R. Reddy. 2020. "Association between EMIC wave occurrence and enhanced convection periods during ion injections." Geophysical Research Letters, 2019GL085676 (In Press) [10.1029/2019gl085676]

    Brito, T. V., A. J. Halford, and S. R. Elkington. 2020. "Ultralow frequency-wave induced losses." The Dynamic Loss of Earth's Radiation Belts, 29-48 [10.1016/b978-0-12-813371-2.00002-0]

    Cid, C., A. Guerrero, E. Saiz, A. Halford, and A. Kellerman. 2019. "Developing the LDi and LCi geomagnetic indices, an example of application of the AULs framework." Space Weather, 2019SW002171 [10.1029/2019sw002171]

    Halford, A. J., A. C. Kellerman, K. Garcia-Sage, et al. J. Klenzing, B. A. Carter, R. M. McGranaghan, T. Guild, C. Cid, C. J. Henney, N. Y. Ganushkina, A. G. Burrell, M. Terkildsen, D. T. Welling, S. A. Murray, K. Leka, J. P. McCollough, B. J. Thompson, A. Pulkkinen, S. F. Fung, S. Bingham, M. M. Bisi, M. W. Liemohn, B. M. Walsh, and S. K. Morley. 2019. "Application Usability Levels: A Framework for Tracking Project Product Progress." J. Space Weather Space Clim. , 9: A34 [https://doi.org/10.1051/swsc/2019030 ]

    Bingley, L., V. Angelopoulos, D. Sibeck, X. Zhang, and A. Halford. 2019. "The Evolution of a Pitch‐Angle “Bite‐Out” Scattering Signature Caused by EMIC Wave Activity: A Case Study." Journal of Geophysical Research: Space Physics, 124 (7): 5042-5055 [10.1029/2018ja026292]

    Lessard, M. R., K. Paulson, H. E. Spence, et al. C. Weaver, M. J. Engebretson, R. Millan, L. Woodger, A. Halford, R. Horne, C. J. Rodger, and A. Hendry. 2019. "Generation of EMIC Waves and Effects on Particle Precipitation During a Solar Wind Pressure Intensification with B z > 0." Journal of Geophysical Research: Space Physics, 2019JA026477 [10.1029/2019ja026477]

    Medeiros, C., V. M. Souza, L. E. Vieira, et al. D. G. Sibeck, A. J. Halford, S.-B. Kang, L. A. Silva, L. R. Alves, J. P. Marchezi, R. S. Dallaqua, P. R. Jauer, M. Rockenbach, O. Mendes, M. V. Alves, A. D. Lago, M.-C. Fok, S. G. Kanekal, D. N. Baker, and C. A. Kletzing. 2019. "On the Contribution of EMIC Waves to the Reconfiguration of the Relativistic Electron Butterfly Pitch Angle Distribution Shape on 2014 September 12—A Case Study." The Astrophysical Journal, 872 (1): 36 [10.3847/1538-4357/aaf970]

    Angelopoulos, V., P. Cruce, A. Drozdov, et al. E. W. Grimes, N. Hatzigeorgiu, D. A. King, D. Larson, J. W. Lewis, J. M. McTiernan, D. A. Roberts, C. L. Russell, T. Hori, Y. Kasahara, A. Kumamoto, A. Matsuoka, Y. Miyashita, Y. Miyoshi, I. Shinohara, M. Teramoto, J. B. Faden, A. J. Halford, M. McCarthy, R. M. Millan, J. G. Sample, D. M. Smith, L. A. Woodger, A. Masson, A. A. Narock, K. Asamura, T. F. Chang, C.-Y. Chiang, Y. Kazama, K. Keika, S. Matsuda, T. Segawa, K. Seki, M. Shoji, S. W. Tam, N. Umemura, B.-J. Wang, S.-Y. Wang, R. Redmon, J. V. Rodriguez, H. J. Singer, J. Vandegriff, S. Abe, M. Nose, A. Shinbori, Y.-M. Tanaka, S. UeNo, L. Andersson, P. Dunn, C. Fowler, J. S. Halekas, T. Hara, Y. Harada, C. O. Lee, R. Lillis, D. L. Mitchell, M. R. Argall, K. Bromund, J. L. Burch, I. J. Cohen, M. Galloy, B. Giles, A. N. Jaynes, O. Le Contel, M. Oka, T. D. Phan, B. M. Walsh, J. Westlake, F. D. Wilder, S. D. Bale, R. Livi, M. Pulupa, P. Whittlesey, A. DeWolfe, B. Harter, E. Lucas, U. Auster, J. W. Bonnell, C. M. Cully, E. Donovan, R. E. Ergun, H. U. Frey, B. Jackel, A. Keiling, H. Korth, J. P. McFadden, Y. Nishimura, F. Plaschke, P. Robert, D. L. Turner, J. M. Weygand, R. M. Candey, R. C. Johnson, T. Kovalick, M. H. Liu, R. E. McGuire, A. Breneman, K. Kersten, and P. Schroeder. 2019. "The Space Physics Environment Data Analysis System (SPEDAS)." Space Science Reviews, 215 (1): 9 [10.1007/s11214-018-0576-4]

    Rudd, J., D. Oliveira, A. Bhaskar, and A. Halford. 2019. "How do interplanetary shock impact angles control the size of the geoeffective magnetosphere?" Advances in Space Research, 61 (1): 317-326 [10.1016/j.asr.2018.09.013]

    Burrell, A. G., A. Halford, J. Klenzing, et al. R. A. Stoneback, S. K. Morley, A. M. Annex, K. M. Laundal, A. C. Kellerman, D. Stansby, and J. Ma. 2018. "Snakes on a Spaceship—An Overview of Python in Heliophysics." Journal of Geophysical Research: Space Physics, 123 (12): 2018JA025877 [10.1029/2018ja025877]

    Chaston, C. C., J. W. Bonnell, A. J. Halford, et al. G. D. Reeves, D. N. Baker, C. A. Kletzing, and J. R. Wygant. 2018. "Pitch Angle Scattering and Loss of Radiation Belt Electrons in Broadband Electromagnetic Waves." Geophysical Research Letters, 45 (18): 9344-9352 [10.1029/2018gl079527]

    Gunawan, B., E. A. Bering, R. Talbot, et al. C. Glennie, D. Rodrigues, J. Chen, M. Alozie, C. Behrend, C. Bias, A. Ehteshami, A. Fenton, M. L. Greer, J. Lehnen, A. Martinez, S. Mathur, M. Medellin, T. Nguyen, M. Nowling, D. Perez, M. Pham, M. Pina, I. Porat, J. Prince, G. Thomas, B. Velasquez, L. Victor, R. Gamblin, J. Subhlok, W. Harrison, A. Hamza, B. J. Dunbar, N. Moelders, D. Hampton, R. Millan, and A. J. Halford. 2018. "NASA and University of Houston’s Approach in Engaging and Developing Undergraduate Students’ Skills Through Undergraduate Student Instrumentation Project." 2018 AIAA SPACE and Astronautics Forum and Exposition, [10.2514/6.2018-5139]

    Remya, B., D. G. Sibeck, A. J. Halford, et al. K. R. Murphy, G. D. Reeves, H. J. Singer, J. R. Wygant, G. Farinas Perez, and S. A. Thaller. 2018. "Ion Injection Triggered EMIC Waves in the Earth's Magnetosphere." Journal of Geophysical Research: Space Physics, 123 (6): 4921-4938 [10.1029/2018ja025354]

    Oliveira, D. M., D. Arel, J. Raeder, et al. E. Zesta, C. M. Ngwira, B. A. Carter, E. Yizengaw, A. J. Halford, B. T. Tsurutani, and J. W. Gjerloev. 2018. "Geomagnetically induced currents caused by interplanetary shocks with different impact angles and speeds." Space Weather, 16 (6): 636-647 [10.1029/2018sw001880]

    Jonathan Rae, I., K. R. Murphy, C. E. Watt, et al. A. J. Halford, I. R. Mann, L. G. Ozeke, D. G. Sibeck, M. A. Clilverd, C. J. Rodger, A. W. Degeling, C. Forsyth, and H. J. Singer. 2018. "The Role of Localized Compressional Ultra-low Frequency Waves in Energetic Electron Precipitation." Journal of Geophysical Research: Space Physics, [10.1002/2017ja024674]

    Greer, M. L., E. A. Bering, R. Talbot, et al. B. Dunbar, C. Glennie, D. Rodrigues, J. Chen, M. Alozie, C. Behrend, C. Bias, A. Ehteshami, A. Fenton, B. Gunawan, J. Lehnen, A. Martinez, S. Mathur, M. Medellin, T. Nguyen, T. V. Nguyen, M. Nowling, D. Perez, M. Pham, M. Pina, I. Porat, J. Prince, G. Thomas, B. Velasquez, L. Victor, R. Gamblin, N. Moelders, D. Hampton, R. Millan, and A. Halford. 2017. "The Undergraduate Student Instrumentation Project: A Foray into Instrument Design, Payload Fabrication, and Project Management." AIAA SPACE and Astronautics Forum and Exposition, [10.2514/6.2017-5136]

    Clilverd, M. A., C. J. Rodger, M. McCarthy, et al. R. Millan, L. W. Blum, N. Cobbett, J. B. Brundell, D. Danskin, and A. J. Halford. 2017. "Investigating energetic electron precipitation through combining ground‐based and balloon observations." Journal of Geophysical Research: Space Physics, 122 (1): 534-546 [10.1002/2016ja022812]

    Zhang, J., A. J. Halford, A. A. Saikin, et al. C.-L. Huang, H. E. Spence, B. A. Larsen, G. D. Reeves, R. M. Millan, C. W. Smith, R. B. Torbert, W. S. Kurth, C. A. Kletzing, J. B. Blake, J. F. Fennel, and D. N. Baker. 2016. "EMIC waves and associated relativistic electron precipitation on 25-26 January 2013." Journal of Geophysical Research: Space Physics, 121 (11): 11,086-11,100 [10.1002/2016ja022918]

    Halford, A. J., B. J. Fraser, S. K. Morley, S. R. Elkington, and A. A. Chan. 2016. "Dependence of EMIC wave parameters during quiet, geomagnetic storm, and geomagnetic storm phase times." Journal of Geophysical Research: Space Physics, 121 (7): 6277–6291 [10.1002/2016ja022694]

    Halford, A. J., S. L. McGregor, M. K. Hudson, R. M. Millan, and B. T. Kress. 2016. "BARREL observations of a solar energetic electron and solar energetic proton event." Journal of Geophysical Research: Space Physics, 121 (5): 4205-4216 [10.1002/2016ja022462]

    Carter, B. A., E. Yizengaw, R. Pradipta, et al. A. J. Halford, R. Norman, and K. Zhang. 2015. "Interplanetary shocks and the resulting geomagnetically induced currents at the equator." Geophysical Research Letters, 42 (16): 6554-6559 [10.1002/2015gl065060]

    Blum, L. W., A. Halford, R. Millan, et al. J. W. Bonnell, J. Goldstein, M. Usanova, M. Engebretson, M. Ohnsted, G. Reeves, H. Singer, M. Clilverd, and X. Li. 2015. "Observations of coincident EMIC wave activity and duskside energetic electron precipitation on 18-19 January 2013." Geophysical Research Letters, 42 (14): 5727-5735 [10.1002/2015gl065245]

    Breneman, A. W., A. Halford, R. Millan, et al. M. McCarthy, J. Fennell, J. Sample, L. Woodger, G. Hospodarsky, J. R. Wygant, C. A. Cattell, J. Goldstein, D. Malaspina, and C. A. Kletzing. 2015. "Global-scale coherence modulation of radiation-belt electron loss from plasmaspheric hiss." Nature, 523 (7559): 193-195 [10.1038/nature14515]

    Woodger, L. A., A. J. Halford, R. M. Millan, et al. M. P. McCarthy, D. M. Smith, G. S. Bowers, J. G. Sample, B. R. Anderson, and X. Liang. 2015. "A summary of the BARREL campaigns: Technique for studying electron precipitation." Journal of Geophysical Research: Space Physics, 120 (6): 4922-4935 [10.1002/2014ja020874]

    Brito, T., M. K. Hudson, B. Kress, et al. J. Paral, A. Halford, R. Millan, and M. Usanova. 2015. "Simulation of ULF wave-modulated radiation belt electron precipitation during the 17 March 2013 storm." Journal of Geophysical Research: Space Physics, 120 (5): 3444-3461 [10.1002/2014ja020838]

    Halford, A. J., S. L. McGregor, K. R. Murphy, et al. R. M. Millan, M. K. Hudson, L. A. Woodger, C. A. Cattel, A. W. Breneman, I. R. Mann, W. S. Kurth, G. B. Hospodarsky, M. Gkioulidou, and J. F. Fennell. 2015. "BARREL observations of an ICME-shock impact with the magnetosphere and the resultant radiation belt electron loss." Journal of Geophysical Research: Space Physics, 120 (4): 2557-2570 [10.1002/2014ja020873]

    Halford, A. J., B. J. Fraser, and S. K. Morley. 2015. "EMIC waves and plasmaspheric and plume density: CRRES results." Journal of Geophysical Research: Space Physics, 120 (3): 1974-1992 [10.1002/2014ja020338]

    Blum, L. W., Q. Schiller, X. Li, et al. R. Millan, A. Halford, and L. Woodger. 2013. "New conjunctive CubeSat and balloon measurements to quantify rapid energetic electron precipitation." Geophysical Research Letters, 40 (22): 5833-5837 [10.1002/2013gl058546]

    Millan, R. M., M. P. McCarthy, J. G. Sample, et al. D. M. Smith, L. D. Thompson, D. G. McGaw, L. A. Woodger, J. G. Hewitt, M. D. Comess, K. B. Yando, A. X. Liang, B. A. Anderson, N. R. Knezek, W. Z. Rexroad, J. M. Scheiman, G. S. Bowers, A. J. Halford, A. B. Collier, M. A. Clilverd, R. P. Lin, and M. K. Hudson. 2013. "The Balloon Array for RBSP Relativistic Electron Losses (BARREL)." Space Science Reviews, 179 (1-4): 503-530 [10.1007/s11214-013-9971-z]

    Halford, A. J., B. J. Fraser, and S. K. Morley. 2010. "EMIC wave activity during geomagnetic storm and nonstorm periods: CRRES results." Journal of Geophysical Research: Space Physics, 115 (A12): [10.1029/2010ja015716]

    Engebretson, M. J., J. L. Posch, A. J. Halford, et al. G. A. Shelburne, A. J. Smith, M. Spasojević, U. S. Inan, and R. L. Arnoldy. 2004. "Latitudinal and seasonal variations of quasiperiodic and periodic VLF emissions in the outer magnetosphere." Journal of Geophysical Research, 109 (A5): A05216 [10.1029/2003ja010335]

    Talks, Presentations and Posters

    Invited

    The Effect of Compression Induced Chorus Waves on 10s eV to 100s keV Electron Precipitation

    7 / 2020

    CU Boulder LASP FoM Seminar series

    Space Weather: Killer Electron Edition, USIP: Balloon-borne System Data Sensors Seminar Class

    4 / 2020

    University Houston

    The Assessment of Understanding and Quantifying Progress Working Group, Tracking Space Weather Application Progress Towards Usability: Application Usability Levels

    5 / 2019

    A.J. Halford A. Kellerman,B. Thompson, A. Pulkkinen, K. Garcia-Sage, B. Carter, S. A. Murray, S. Bingham, D. Welling, The Assessment of Understanding and Quantifying Progress Working Group, Tracking Space Weather Application Progress Towards Usability: Application Usability Levels, JPGU, May 2019, Chiba, Japan

    The panel was recorded can be watched at http://www.ustream.tv/recorded/120752782

     Application Usability Levels, European Space Weather Week, Nov. 2018

    11 / 2018

    European Space Weather Week

    The storm that wasn't: A look at multiple loss processes occurring simultaneously and how they interact with each other

    7 / 2018

    Exploring Systems-Science Techniques for the Earth's Magnetosphere-Ionosphere-Thermosphere, Los Alamos NM

    Coincident Compression Generated EMIC Chorus and Hiss waves

    5 / 2017

    JpGU-AUG Joint meeting May 2017, Chiba, Japan

    Taking up Space

    3 / 2017

    Maryland Institute College of Art, March 2017

    Observations of a solar storm from the stratosphere: The BARREL Mission

    12 / 2016

    Dec. 2016, Google Hangout University of Houston Physics Seminar series

    A Sun to mud view of a heliospheric storm: The little mission that could

    1 / 2016

    Plasma Physics seminar, January 2016 Dartmouth College Hanover NH

    Precipitation events as observed with BARREL

    3 / 2015

    the BARREL team, Precipitation events as observed with BARREL, Inner Magnetosphere Coupling III, March 2015, UCLA

    Space Balloons and Killer Electrons

    10 / 2014

    Space Balloons and Killer Electrons, Google Hangout about Space physics directed for STEM majors at Alabama universities. I was asked to give this talk based on my twitter activities and participation through EPSCORE workshops. October 21 2014

    Early Results from the BARREL 2013 Balloon Campaign and a look to the 2014 Campaign

    9 / 2013

    A.J. Halford, R. Millan, BARREL Team, Early Results from the BARREL 2013 Balloon Campaign and a look to the 2014 Campaign, Cluster workshop, Tromso, Norway, September 2013

    Early Results from the BARREL 2013 Balloon Campaign

    8 / 2013

    A.J. Halford, R. Millan, BARREL Team, Early Results from the BARREL 2013 Balloon Campaign, IAGA, Merida, Mexico, August 2013

    EMIC waves and the radiation belts

    6 / 2012

    EMIC waves and the radiation belts, Dartmouth, New Hampshire, invited talk 2012

    EMIC waves and the plasmasphere

    2011

    EMIC waves and the plasmasphere, UNH, New Hampshire, invited talk 2011

    Selected Public Outreach

    Panelist on Astrobiology, at Awesome Con Washington DC 4 / 2019 - Present
    Massive sunspots and huge solar flares mean unexpected space weather for Earth, originally posted in TheConversation.com 9 / 2017 - Present
    https://theconversation.com/massive-sunspots-and-huge-solar-flares-mean-unexpected-space-weather-for-earth-83677

    Halford, A. J., B. A. Carter, J. Currie, editor Maggie Villiger, Massive sunspots and huge solar flares mean unexpected space weather for Earth, originally posted in TheConversation.com at https://theconversation.com/massive-sunspots-and-huge-solar-flares-mean-unexpected-space-weather-for-earth-83677, picked up by other newsoutlets e.g. NewsWeek

    Participated in the June 22nd and August 20th 2017 Reddit Ask Me Anything through NASA about the August 21st 2017 Solar Eclipse 8 / 2017 - Present
    https://www.reddit.com/r/IAmA/comments/6uvtsl/were_nasa_scientists_ask_us_anything_about/
    Damaging electric currents in space affect Earth’s equatorial region, not just the pole 8 / 2015 - Present
    https://theconversation.com/damaging-electric-currents-in-space-affect-earths-equatorial-region-not-just-the-poles-45073
    Scientists at work: space balloons and charged particles above the Arctic Circle 9 / 2015 - Present
    https://theconversation.com/scientists-at-work-space-balloons-and-charged-particles-above-the-arctic-circle-46240
    We are scientists from NASA and The Washington Post talking about today's eclipse. AMA! 8 / 2017 - Present
    https://www.reddit.com/r/science/comments/6v2ju6/we_are_scientists_from_nasa_and_the_washington/
    What's the science behind the eclipse? 8 / 2017 - Present
    https://www.wbaltv.com/article/whats-the-science-behind-the-eclipse/12008806
    Ask the Expert: How to Savour the Heavens 9 / 2016 - Present
    https://dartmouthalumnimagazine.com/articles/ask-expert-14
    FaceBook Live event with the SciTech Discovery Center. 7 / 2020 - Present
    https://www.facebook.com/SciTechDiscoveryCenter/videos/727564438059634/

    Brief Bio

    I am currently a space physics researcher at NASA Goddard Space Flight Center working with the petitSat mission. I started researching waves in Earth's magnetosphere as an undergraduate at Augsburg College with Mark Engebretson using ground based magnetometers in the Arctic and Antarctic. I moved away from waves to focus on geomagnetic storms and substorms during my masters at the University of Colorado Boulder with Dan Baker but returned once more to waves with my PhD at University of Newcastle NSW Australia working under Brian Fraser. My PhD thesis was on Electromagnetic Ion Cyclotron (EMIC) waves during the CRRES mission and their relationship to the plasmasphere and radiation belts. During my postdoc at Dartmouth college I worked on  the BARREL mission I have moved down the field line (from a space perspective) and now look at the population of particles lost due to these interactions and their impact on the ionosphere and upper atmosphere.

    Publications

    Refereed

    Klenzing, J., R. Davidson, S. Jones, et al. C. Martinis, K. Zawdie, G. Earle, J. Smith, A. Halford, S. Noel, N. Paschalidis, R. Pfaff, and E. Robertson. 2020. "The petitSat Mission – Science Goals and Instrumentation." Advances in Space Research 66 (1): 107-115 [10.1016/j.asr.2019.12.013]

    Remya, B., D. Sibeck, J. Ruohoniemi, et al. B. Kunduri, A. Halford, G. Reeves, and R. Reddy. 2020. "Association between EMIC wave occurrence and enhanced convection periods during ion injections." Geophysical Research Letters (In Press) 2019GL085676 [10.1029/2019gl085676]

    Brito, T. V., A. J. Halford, and S. R. Elkington. 2020. "Ultralow frequency-wave induced losses." The Dynamic Loss of Earth's Radiation Belts 29-48 [10.1016/b978-0-12-813371-2.00002-0]

    Cid, C., A. Guerrero, E. Saiz, A. Halford, and A. Kellerman. 2019. "Developing the LDi and LCi geomagnetic indices, an example of application of the AULs framework." Space Weather 2019SW002171 [10.1029/2019sw002171]

    Halford, A. J., A. C. Kellerman, K. Garcia-Sage, et al. J. Klenzing, B. A. Carter, R. M. McGranaghan, T. Guild, C. Cid, C. J. Henney, N. Y. Ganushkina, A. G. Burrell, M. Terkildsen, D. T. Welling, S. A. Murray, K. Leka, J. P. McCollough, B. J. Thompson, A. Pulkkinen, S. F. Fung, S. Bingham, M. M. Bisi, M. W. Liemohn, B. M. Walsh, and S. K. Morley. 2019. "Application Usability Levels: A Framework for Tracking Project Product Progress." J. Space Weather Space Clim. 9 A34 [https://doi.org/10.1051/swsc/2019030 ]

    Bingley, L., V. Angelopoulos, D. Sibeck, X. Zhang, and A. Halford. 2019. "The Evolution of a Pitch‐Angle “Bite‐Out” Scattering Signature Caused by EMIC Wave Activity: A Case Study." Journal of Geophysical Research: Space Physics 124 (7): 5042-5055 [10.1029/2018ja026292]

    Lessard, M. R., K. Paulson, H. E. Spence, et al. C. Weaver, M. J. Engebretson, R. Millan, L. Woodger, A. Halford, R. Horne, C. J. Rodger, and A. Hendry. 2019. "Generation of EMIC Waves and Effects on Particle Precipitation During a Solar Wind Pressure Intensification with B z > 0." Journal of Geophysical Research: Space Physics 2019JA026477 [10.1029/2019ja026477]

    Medeiros, C., V. M. Souza, L. E. Vieira, et al. D. G. Sibeck, A. J. Halford, S.-B. Kang, L. A. Silva, L. R. Alves, J. P. Marchezi, R. S. Dallaqua, P. R. Jauer, M. Rockenbach, O. Mendes, M. V. Alves, A. D. Lago, M.-C. Fok, S. G. Kanekal, D. N. Baker, and C. A. Kletzing. 2019. "On the Contribution of EMIC Waves to the Reconfiguration of the Relativistic Electron Butterfly Pitch Angle Distribution Shape on 2014 September 12—A Case Study." The Astrophysical Journal 872 (1): 36 [10.3847/1538-4357/aaf970]

    Angelopoulos, V., P. Cruce, A. Drozdov, et al. E. W. Grimes, N. Hatzigeorgiu, D. A. King, D. Larson, J. W. Lewis, J. M. McTiernan, D. A. Roberts, C. L. Russell, T. Hori, Y. Kasahara, A. Kumamoto, A. Matsuoka, Y. Miyashita, Y. Miyoshi, I. Shinohara, M. Teramoto, J. B. Faden, A. J. Halford, M. McCarthy, R. M. Millan, J. G. Sample, D. M. Smith, L. A. Woodger, A. Masson, A. A. Narock, K. Asamura, T. F. Chang, C.-Y. Chiang, Y. Kazama, K. Keika, S. Matsuda, T. Segawa, K. Seki, M. Shoji, S. W. Tam, N. Umemura, B.-J. Wang, S.-Y. Wang, R. Redmon, J. V. Rodriguez, H. J. Singer, J. Vandegriff, S. Abe, M. Nose, A. Shinbori, Y.-M. Tanaka, S. UeNo, L. Andersson, P. Dunn, C. Fowler, J. S. Halekas, T. Hara, Y. Harada, C. O. Lee, R. Lillis, D. L. Mitchell, M. R. Argall, K. Bromund, J. L. Burch, I. J. Cohen, M. Galloy, B. Giles, A. N. Jaynes, O. Le Contel, M. Oka, T. D. Phan, B. M. Walsh, J. Westlake, F. D. Wilder, S. D. Bale, R. Livi, M. Pulupa, P. Whittlesey, A. DeWolfe, B. Harter, E. Lucas, U. Auster, J. W. Bonnell, C. M. Cully, E. Donovan, R. E. Ergun, H. U. Frey, B. Jackel, A. Keiling, H. Korth, J. P. McFadden, Y. Nishimura, F. Plaschke, P. Robert, D. L. Turner, J. M. Weygand, R. M. Candey, R. C. Johnson, T. Kovalick, M. H. Liu, R. E. McGuire, A. Breneman, K. Kersten, and P. Schroeder. 2019. "The Space Physics Environment Data Analysis System (SPEDAS)." Space Science Reviews 215 (1): 9 [10.1007/s11214-018-0576-4]

    Rudd, J., D. Oliveira, A. Bhaskar, and A. Halford. 2019. "How do interplanetary shock impact angles control the size of the geoeffective magnetosphere?" Advances in Space Research 61 (1): 317-326 [10.1016/j.asr.2018.09.013]

    Burrell, A. G., A. Halford, J. Klenzing, et al. R. A. Stoneback, S. K. Morley, A. M. Annex, K. M. Laundal, A. C. Kellerman, D. Stansby, and J. Ma. 2018. "Snakes on a Spaceship—An Overview of Python in Heliophysics." Journal of Geophysical Research: Space Physics 123 (12): 2018JA025877 [10.1029/2018ja025877]

    Chaston, C. C., J. W. Bonnell, A. J. Halford, et al. G. D. Reeves, D. N. Baker, C. A. Kletzing, and J. R. Wygant. 2018. "Pitch Angle Scattering and Loss of Radiation Belt Electrons in Broadband Electromagnetic Waves." Geophysical Research Letters 45 (18): 9344-9352 [10.1029/2018gl079527]

    Gunawan, B., E. A. Bering, R. Talbot, et al. C. Glennie, D. Rodrigues, J. Chen, M. Alozie, C. Behrend, C. Bias, A. Ehteshami, A. Fenton, M. L. Greer, J. Lehnen, A. Martinez, S. Mathur, M. Medellin, T. Nguyen, M. Nowling, D. Perez, M. Pham, M. Pina, I. Porat, J. Prince, G. Thomas, B. Velasquez, L. Victor, R. Gamblin, J. Subhlok, W. Harrison, A. Hamza, B. J. Dunbar, N. Moelders, D. Hampton, R. Millan, and A. J. Halford. 2018. "NASA and University of Houston’s Approach in Engaging and Developing Undergraduate Students’ Skills Through Undergraduate Student Instrumentation Project." 2018 AIAA SPACE and Astronautics Forum and Exposition [10.2514/6.2018-5139]

    Remya, B., D. G. Sibeck, A. J. Halford, et al. K. R. Murphy, G. D. Reeves, H. J. Singer, J. R. Wygant, G. Farinas Perez, and S. A. Thaller. 2018. "Ion Injection Triggered EMIC Waves in the Earth's Magnetosphere." Journal of Geophysical Research: Space Physics 123 (6): 4921-4938 [10.1029/2018ja025354]

    Oliveira, D. M., D. Arel, J. Raeder, et al. E. Zesta, C. M. Ngwira, B. A. Carter, E. Yizengaw, A. J. Halford, B. T. Tsurutani, and J. W. Gjerloev. 2018. "Geomagnetically induced currents caused by interplanetary shocks with different impact angles and speeds." Space Weather 16 (6): 636-647 [10.1029/2018sw001880]

    Jonathan Rae, I., K. R. Murphy, C. E. Watt, et al. A. J. Halford, I. R. Mann, L. G. Ozeke, D. G. Sibeck, M. A. Clilverd, C. J. Rodger, A. W. Degeling, C. Forsyth, and H. J. Singer. 2018. "The Role of Localized Compressional Ultra-low Frequency Waves in Energetic Electron Precipitation." Journal of Geophysical Research: Space Physics [10.1002/2017ja024674]

    Greer, M. L., E. A. Bering, R. Talbot, et al. B. Dunbar, C. Glennie, D. Rodrigues, J. Chen, M. Alozie, C. Behrend, C. Bias, A. Ehteshami, A. Fenton, B. Gunawan, J. Lehnen, A. Martinez, S. Mathur, M. Medellin, T. Nguyen, T. V. Nguyen, M. Nowling, D. Perez, M. Pham, M. Pina, I. Porat, J. Prince, G. Thomas, B. Velasquez, L. Victor, R. Gamblin, N. Moelders, D. Hampton, R. Millan, and A. Halford. 2017. "The Undergraduate Student Instrumentation Project: A Foray into Instrument Design, Payload Fabrication, and Project Management." AIAA SPACE and Astronautics Forum and Exposition [10.2514/6.2017-5136]

    Clilverd, M. A., C. J. Rodger, M. McCarthy, et al. R. Millan, L. W. Blum, N. Cobbett, J. B. Brundell, D. Danskin, and A. J. Halford. 2017. "Investigating energetic electron precipitation through combining ground‐based and balloon observations." Journal of Geophysical Research: Space Physics 122 (1): 534-546 [10.1002/2016ja022812]

    Zhang, J., A. J. Halford, A. A. Saikin, et al. C.-L. Huang, H. E. Spence, B. A. Larsen, G. D. Reeves, R. M. Millan, C. W. Smith, R. B. Torbert, W. S. Kurth, C. A. Kletzing, J. B. Blake, J. F. Fennel, and D. N. Baker. 2016. "EMIC waves and associated relativistic electron precipitation on 25-26 January 2013." Journal of Geophysical Research: Space Physics 121 (11): 11,086-11,100 [10.1002/2016ja022918]

    Halford, A. J., B. J. Fraser, S. K. Morley, S. R. Elkington, and A. A. Chan. 2016. "Dependence of EMIC wave parameters during quiet, geomagnetic storm, and geomagnetic storm phase times." Journal of Geophysical Research: Space Physics 121 (7): 6277–6291 [10.1002/2016ja022694]

    Halford, A. J., S. L. McGregor, M. K. Hudson, R. M. Millan, and B. T. Kress. 2016. "BARREL observations of a solar energetic electron and solar energetic proton event." Journal of Geophysical Research: Space Physics 121 (5): 4205-4216 [10.1002/2016ja022462]

    Carter, B. A., E. Yizengaw, R. Pradipta, et al. A. J. Halford, R. Norman, and K. Zhang. 2015. "Interplanetary shocks and the resulting geomagnetically induced currents at the equator." Geophysical Research Letters 42 (16): 6554-6559 [10.1002/2015gl065060]

    Blum, L. W., A. Halford, R. Millan, et al. J. W. Bonnell, J. Goldstein, M. Usanova, M. Engebretson, M. Ohnsted, G. Reeves, H. Singer, M. Clilverd, and X. Li. 2015. "Observations of coincident EMIC wave activity and duskside energetic electron precipitation on 18-19 January 2013." Geophysical Research Letters 42 (14): 5727-5735 [10.1002/2015gl065245]

    Breneman, A. W., A. Halford, R. Millan, et al. M. McCarthy, J. Fennell, J. Sample, L. Woodger, G. Hospodarsky, J. R. Wygant, C. A. Cattell, J. Goldstein, D. Malaspina, and C. A. Kletzing. 2015. "Global-scale coherence modulation of radiation-belt electron loss from plasmaspheric hiss." Nature 523 (7559): 193-195 [10.1038/nature14515]

    Woodger, L. A., A. J. Halford, R. M. Millan, et al. M. P. McCarthy, D. M. Smith, G. S. Bowers, J. G. Sample, B. R. Anderson, and X. Liang. 2015. "A summary of the BARREL campaigns: Technique for studying electron precipitation." Journal of Geophysical Research: Space Physics 120 (6): 4922-4935 [10.1002/2014ja020874]

    Brito, T., M. K. Hudson, B. Kress, et al. J. Paral, A. Halford, R. Millan, and M. Usanova. 2015. "Simulation of ULF wave-modulated radiation belt electron precipitation during the 17 March 2013 storm." Journal of Geophysical Research: Space Physics 120 (5): 3444-3461 [10.1002/2014ja020838]

    Halford, A. J., S. L. McGregor, K. R. Murphy, et al. R. M. Millan, M. K. Hudson, L. A. Woodger, C. A. Cattel, A. W. Breneman, I. R. Mann, W. S. Kurth, G. B. Hospodarsky, M. Gkioulidou, and J. F. Fennell. 2015. "BARREL observations of an ICME-shock impact with the magnetosphere and the resultant radiation belt electron loss." Journal of Geophysical Research: Space Physics 120 (4): 2557-2570 [10.1002/2014ja020873]

    Halford, A. J., B. J. Fraser, and S. K. Morley. 2015. "EMIC waves and plasmaspheric and plume density: CRRES results." Journal of Geophysical Research: Space Physics 120 (3): 1974-1992 [10.1002/2014ja020338]

    Blum, L. W., Q. Schiller, X. Li, et al. R. Millan, A. Halford, and L. Woodger. 2013. "New conjunctive CubeSat and balloon measurements to quantify rapid energetic electron precipitation." Geophysical Research Letters 40 (22): 5833-5837 [10.1002/2013gl058546]

    Millan, R. M., M. P. McCarthy, J. G. Sample, et al. D. M. Smith, L. D. Thompson, D. G. McGaw, L. A. Woodger, J. G. Hewitt, M. D. Comess, K. B. Yando, A. X. Liang, B. A. Anderson, N. R. Knezek, W. Z. Rexroad, J. M. Scheiman, G. S. Bowers, A. J. Halford, A. B. Collier, M. A. Clilverd, R. P. Lin, and M. K. Hudson. 2013. "The Balloon Array for RBSP Relativistic Electron Losses (BARREL)." Space Science Reviews 179 (1-4): 503-530 [10.1007/s11214-013-9971-z]

    Halford, A. J., B. J. Fraser, and S. K. Morley. 2010. "EMIC wave activity during geomagnetic storm and nonstorm periods: CRRES results." Journal of Geophysical Research: Space Physics 115 (A12): [10.1029/2010ja015716]

    Engebretson, M. J., J. L. Posch, A. J. Halford, et al. G. A. Shelburne, A. J. Smith, M. Spasojević, U. S. Inan, and R. L. Arnoldy. 2004. "Latitudinal and seasonal variations of quasiperiodic and periodic VLF emissions in the outer magnetosphere." Journal of Geophysical Research 109 (A5): A05216 [10.1029/2003ja010335]

                                                                                                                                                                                            
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