Oxygen-hydrogen differentiated observations from TWINS: The 22 July 2009 storm

P. W. Valek, J. Goldstein, D. J. McComas, R. Iiie, N. Buzulukova, M. C. Fok, J. D. Perez

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


The 22 July 2009 magnetic storm is the first significant storm during the emergence of the recent prolonged solar cycle minimum. This moderate storm (minimum Dst approximately ≤ -78 nT) has received a good deal of attention in the community. We present here global observations of the H and O populations in the inner magnetosphere using Energetic Neutral Atom (ENA) observations from the TWINS mission. We develop and provide the methodology for separating H and O ENAs, based on mass dependent differences in the pulse height distributions of the microchannel plate (MCP) based detectors. We present the first composition separated H and O ENA images at central energies of 16 and 32 keV. We also show that TWINS has sufficient angular resolution to separate the High Altitude Emissions (HAEs) from the Low Altitude Emissions (LAEs). We observe that all ENA emissions in this energy range quickly rise, but the O ENAs have a larger relative increase, and stay at elevated levels much longer, well into the recovery phase. Key Points We present the first 16 and 32 keV global O and H ENA images Sufficient spatial resolution to differentiate between H and O HAEs and LAEs We identified key differences in the evolution of H and O during this storm

Original languageEnglish (US)
Pages (from-to)3377-3393
Number of pages17
JournalJournal of Geophysical Research: Space Physics
Issue number6
StatePublished - Jun 2013
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Space and Planetary Science
  • Geophysics


  • ENAs
  • Oxygen
  • magnetic storms


Dive into the research topics of 'Oxygen-hydrogen differentiated observations from TWINS: The 22 July 2009 storm'. Together they form a unique fingerprint.

Cite this