The Role and Contributions of Energetic Neutral Atom (ENA) Imaging in Magnetospheric Substorm Research

Pollock, C. J.; C:Son-Brandt, P.; Burch, J. L.; Henderson, M. G.; Jahn, J. M.; McComas, D. J.; Mende, S.; Mitchell, D. G.; Reeves, G. D.; Scime, Earl; Skoug, R. M.; Thomsen, Michelle; Valek, P. W.

doi:10.1007/978-94-010-0027-7_8

Cited by 9 publications

(9 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The images show that the ENA flux enhancement is weak-to-modest. More importantly, the enhancement is overall global and quasisimultaneous in MLT, and does not reveal any evidence for substorm-injected particles on the nightside; for substorm events, an ENA emission enhancement first occurs near midnight and then spreads toward the duskside all the way around to noon reflecting the ion drift effect, which is faster and clearer for higher energies than for lower energies [e.g., Pollock et al, 2003;Mitchell et al, 2001]. The lack of evidence for a substorm in the ENA response is consistent with the other observations discussed above.…”

Section: The 18 August 2001 Eventmentioning

confidence: 99%

“…These ENAs travel freely without being affected by electromagnetic fields in the magnetosphere, and they can be used to remotely measure the magnetospheric ions. This powerful tool for space plasma diagnostics has been used substantially for ring current study [e.g., Roelof, 1987;Henderson et al, 1997;Brandt et al, 2002a;Ohtani et al, 2006], for substorm or stormsubstorm relation research [e.g., Jorgensen et al, 2000;Reeves and Henderson, 2001;Brandt et al, 2002bBrandt et al, , 2002cReeves et al, 2004;Ohtani et al, 2005;Pollock et al, 2003], for oxygen studies [e.g., Lui et al, 2005;Mitchell et al, 2003;Nosé et al, 2005], and for other issues [e.g., Perez et al, 2004;Vallat et al, 2004]. Several spacecraft have made ENA observations, such as ISEE 1 [Roelof, 1987], Astrid [Barabash, 1995;Brandt et al, 1999], Geotail [Lui et al, 1996], POLAR [Henderson et al, 1997], Cassini [Mitchell et al, 1998] and IMAGE [Mitchell et al, 2000].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Energetic neutral atom response to solar wind dynamic pressure enhancements

et al. 2007

View full text Add to dashboard Cite

[1] We have investigated the response of the ring current to solar wind dynamic pressure (P dyn ) enhancement impacts on the magnetosphere by using energetic neutral atom (ENA) images obtained by the High-Energy Neutral Atom (HENA) imager on board the IMAGE spacecraft. In this work we present several events by distinguishing between pressure events where only the pure compression effects exist (without substorm effects) and those where the substorm is triggered by the P dyn enhancement, and we find notable differences between these two types of events. First, for the pure compression events, we present four events where the P dyn increases by $100% to $450% under northward interplanetary magnetic field (IMF) conditions. The P dyn enhancement results in weak-to-modest ENA emission increases in both the hydrogen and oxygen channels: The total ENA emission rate increases by $25% to $40% relative to averages over the 1-hour period prior to the P dyn enhancement impact. This ENA enhancement is due to ions adiabatically energized by the compression. The increased ENA emission rate drops as P dyn decreases, implying that the ENA responses are directly caused by the adiabatic compression and decompression process. Also, the pure compression events lead to overall global, quasi-simultaneous increases of ENA in contrast to pure substorm-induced ENA enhancements that are initially localized in the nightside region followed by the drift effect. Next we present two events where the P dyn enhancement was $100% and >300%, respectively, under strongly southward IMF conditions, IMF B z À10 nT, and a substorm was triggered. For both events the hydrogen and oxygen ENA emission increase is far more significant than that for the pure compression events, more than 100% even when the low-altitude contribution was excluded. This is primarily owing to energetic ions generated by the triggered substorm, although the compression effect itself occurs as well. Also, the ENA enhancement appears to be not as global in magnetic local time (MLT) as for the pure compression events, because of the predominant substorm effect that starts near midnight and spreads in MLT.Citation: Lee, D.-Y., S. Ohtani, P. C. Brandt, and L. R. Lyons (2007), Energetic neutral atom response to solar wind dynamic pressure enhancements,

show abstract

Section: The 18 August 2001 Eventmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Energetic neutral atom response to solar wind dynamic pressure enhancements

et al. 2007

View full text Add to dashboard Cite

show abstract

“…Such data permit direct correlations to be made between globally integrated ENA images and the total energy of the ring current Jorgensen et al, 1997), while in addition, allowing the storm-time injection process to be visually tracked (Brandt et al, 2002b). Azimuthal asymmetry can be seen to evolve during a magnetic storm, reflecting the cumulative effects of ion drifts and the establishment and decay of the partial ring current (see, for example, Blake et al, 1995;Burch, 2003;Brandt et al, 2002a;Kozyra and Liemohn, 2003;Pollock et al, 2003). The drift of injected ions was first imaged by PO-LAR CEPAD/IPS, (Henderson et al, 2000).…”

Section: Low Altitude/high Altitude Ena Observationsmentioning

confidence: 99%

The NUADU experiment on TC-2 and the first Energetic Neutral Atom (ENA) images recorded by this instrument

McKenna‐Lawlor

Barabash

et al. 2005

Ann. Geophys.

View full text Add to dashboard Cite

show abstract

“…Remote ENA imaging of magnetospheric energetic ions was first demonstrated with IMP 7 & 8 and ISEE 1 observations of 50 keV ENAs [Roelof et al, 1985;Roelof, 1987]. Since then, ENAs have been used to remotely image the ring current during geomagnetic storms and substorms [e.g., Henderson et al, 1997;Pollock et al, 2003;Vallat et al, 2004], mostly from spacecraft at high altitudes, outside the trapped radiation belts. IMAGE extended the energies down to ∼1 keV [e.g., Mitchell et al, 2001;Pollock et al, 2001], and Astrid-1 made ∼26-37 keV ENA measurements in the polar cap and near the equator from low Earth orbit (LEO, ∼1000 km) [C: son Brandt et al, , 2002b.…”

Section: Introductionmentioning

confidence: 99%

Energetic, ∼5–90 keV neutral atom imaging of a weak substorm with STEREO/STE

Wang

Lin

Parks

et al. 2010

Geophysical Research Letters

View full text Add to dashboard Cite

[1] We present imaging and high resolution energy spectra of energetic ∼5-90 keV neutral atoms (ENA) of a weak geomagnetic substorm (Dst > −8 nT and AE ] 200 nT), made by the Suprathermal Electron (STE) instrument on the STEREO B spacecraft. Enhanced ENA emissions were observed coming from around local midnight near the equator with different spatial distribution and/or temporal behavior at ∼5-20keV compared to ∼20-90 keV. By forward modeling using a parameterized ring-current model, we show that the ENA images imply the parent equatorial protons have pitch-angle distributions peaked at 90°, an energy spectrum consistent with in situ proton measurements at geosynchronous orbit, and a spatial asymmetry with the maximum flux at midnight for 5-20 keV and at 2240 MLT for 20-90 keV. These are the first ENA measurements at ∼5 to 26 keV from low altitude, and the first for such weak activity. Citation: Wang, L.,

show abstract

The Role and Contributions of Energetic Neutral Atom (ENA) Imaging in Magnetospheric Substorm Research

Cited by 9 publications

References 38 publications

Energetic neutral atom response to solar wind dynamic pressure enhancements

Energetic neutral atom response to solar wind dynamic pressure enhancements

The NUADU experiment on TC-2 and the first Energetic Neutral Atom (ENA) images recorded by this instrument

Energetic, ∼5–90 keV neutral atom imaging of a weak substorm with STEREO/STE

Contact Info

Product

Resources

About