Iterative inversion of global magnetospheric ion distributions using energetic neutral atom (ENA) images recorded by the NUADU/TC2 instrument

Cao

et al. 2015

Sci. China Earth Sci.

Self Cite

Comprehensive records are available in ENA data of ring current activity recorded by the NUADU instrument aboard TC-2 on 15 May, 2005 during a major magnetic storm (which incorporated a series of substorms). Ion fluxes at 4-min temporal resolution derived from ENA data in the energy ranges 50-81 and 81-158 keV are compared with in situ particle fluxes measured by the LANL-SOPA instruments aboard LANL-01, LANL-02, LANL-97, and LANL-84 (a series of geostationary satellites that encircle the equatorial plane at ~6.6 R E ). Also, magnetic fields measured simultaneously by the magetometers aboard GOES-10 and GOES-12 (which are also geostationary satellites) are compared with the particle data. It is demonstrated that ion fluxes in the ring current were enhanced during geomagnetic field tailward stretching in the growth phases of substorms rather than after Earthward directed dipolarization events. This observation, which challenges the existing concept that ring current particles are injected Earthward from the magnetotail following dipolarization events, requires further investigation using a large number of magnetic storm events. . 2016. The causal sequence investigation of the ring current ion-flux increasing and the magnetotail ion injection during a major storm.

Section: Introductionmentioning

confidence: 99%

The causal sequence investigation of the ring current ion-flux increasing and the magnetotail ion injection during a major storm

Cao

et al. 2015

Sci. China Earth Sci.

Self Cite

“…[42] More recently, a method customized for NUADU data, which during ring current disturbances feature spatially sharply peaked bright emissions, was developed to retrieve the parent ion distributions [Lu et al, 2008]. The ENA images utilized in this procedure are first cleaned to (1) remove effects due to solar photons, (2) balance statistically noise responses between different detectors, and (3) correct polar overlaps in the fields of view of certain detectors.…”

Section: Methods Of Ion Distribution Retrieval Customized For Nuadu Datamentioning

confidence: 99%

“…Section 4 provides an overview of classical methodologies used to retrieve ion distributions from ENA images. An account of a method recently developed [Lu et al, 2008] to retrieve ion distributions from data measured by NUADU under disturbed geomagnetic conditions is outlined in section 4.2 and described in detail in Appendices A and B. This method is used to derive ion distributions in the ring current recorded by NUADU between 2330 and 2400 UT, 21 January, 0030-0100 UT, 22 January, and 0100-0130 UT, 22 January 2005.…”

Section: Present Studymentioning

confidence: 99%

Moderate geomagnetic storm (21–22 January 2005) triggered by an outstanding coronal mass ejection viewed via energetic neutral atoms

Dandouras

et al. 2010

J. Geophys. Res.

was accompanied by a coronal mass ejection which arrived at the magnetopause at ∼1712 UT, 21 January, and produced a strong compression-pressure pulse. Enhanced magnetospheric activity was stimulated. The associated development between <1800 UT and >02.19 UT on 21-22 January, 2005 of a ring current disturbance in energetic neutral atom (ENA) data, recorded aboard both the Double Star and the IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) spacecraft, is described. A magnetic storm from ∼1712 UT, 21 January, reached minimum Dst = ∼−101 nT at ∼0600 UT, 22 January, and its recovery phase endured until 27 January. ENA data indicate that the ring current experienced a deep injection of H + and O + ions at ∼1830 UT when IMF Bz was oriented southward. At this time, the ring current was strongly asymmetric, although later it became more symmetric. Bz turned northward at 1946 UT. From ∼0224 to ∼0612 UT on 22 January, Bz fluctuated such that it intermittently pointed southward (±10 nT). The moderate but extended response of the geomagnetosphere to the strong pressure pulse is explained by a slow evolution in the orientation of Bz under conditions of enhanced plasma sheet density. Modeling of dynamical parameters that represent various current systems that contributed to Dst revealed their individual characteristics. The changing geomagnetic field was also modeled. Comparisons with ENA data show that early asymmetric enhancements recorded in hydrogen and oxygen were accompanied by intensified external current systems that produced a magnetic field related compression of the magnetosphere. The gradual reduction in ring current asymmetry was complemented by the largely symmetrical configuration displayed by the corresponding, still intensified, modeled magnetic field.

“…Initial investigations showed that the DeMajistre inversion method is not suitable to use when processing NUADU data as the solutions thereby obtained tend to oscillate, and even to present negative values. Also, the strong coefficient of constraint required to be employed can act to smooth the inverted ion flux distribution unduly and, thereby, compromise the correct recovery of the region of maximum ENA emission [Lu et al, 2008;McKenna-Lawlor et al, 2010]. To overcome these problems, a custom designed method was developed (section 2) to retrieve ion distributions for NUADU measurements based on a kappa model (whereas the DeMajistre method employs an exponent model).…”

Section: Analysis Of Nuadu/ena Datamentioning

confidence: 99%

Comparisons between ion distributions retrieved from ENA images of the ring current and contemporaneous, multipoint ion measurements recorded in situ during the major magnetic storm of 15 May 2005

Barabash

et al. 2010

J. Geophys. Res.

Self Cite

[1] The Neutral Atom Detector Unit (NUADU) aboard the TC-2 spacecraft recorded energetic neutral atom (ENA) image data for >3 h during part of the main and recovery phases of a major magnetic storm on 15 May 2005. A custom designed, constrained linear inversion method was applied to retrieve ring current ion distributions in the ENA records out to L = 6.6. Comparisons were then made between the ion fluxes retrieved from these ENA data (energy ranges 50-81 keV and 81-158 keV) and complementary, contemporaneous particle fluxes measured in situ by Synchronous Orbit Particle Analyzer (SOPA) instruments aboard a series of geosynchronous satellites that were launched to encircle the equatorial plane at L ∼ 6.6 by the Los Alamos National Laboratory (LANL). The ENA data revealed the development of two emission peaks during the main phase of the storm which corresponded to the arrival from the magnetotail of a pair of particle injections. These injections reached, in each case, maximum value before the corresponding AL index amplitude peak was attained. The main phase of the storm concluded (Dst ≈ −256 nT) in the aftermath of this event pair, and the ring current ion fluxes thereafter gradually decayed over several hours (the storm recovery phase). This is the first time that the linear inversion method developed for NUADU data has been globally validated using multipoint in situ measurements made at different magnetic local times. It was found that the higher the derived flux values were on the duskside/nightside, the closer they were to the in situ measurements. The retrieved fluxes obtained on the duskside/nightside tended, however, to be still somewhat underestimated since the ENA measurements concerned were made around the outer edge of the ring current at an altitude where the magnetic field in the inner magnetosphere deviates from that dipole configuration assumed in the inversion procedure to pertain there. The two methods utilized to study ions during a large magnetic storm are complementary in that the retrieved ion fluxes provide high time resolution information concerning the changing, large-scale structure of ring current events, whereas in situ flux sampling presents "measurement truth" at particular locations within individual ring currents.