Low‐altitude ion upflow observed by EISCAT and its effects on supply of molecular ions in the ring current detected by Arase (ERG)

2021 ◽  
Author(s):  
M. Takada ◽  
K. Seki ◽  
Y. Ogawa ◽  
K. Keika ◽  
S. Kasahara ◽  
...  
Keyword(s):  
Ring Current ◽  
Molecular Ions ◽  
Low Altitude

Properties of molecular ions in the ring current and their supply mechanism from the low-altitude ionosphere

2021 ◽  
Author(s):  
Kanako Seki ◽  
Masayoshi Takada ◽  
Kunihiro Keika ◽  
Satoshi Kasahara ◽  
Shoichiro Yokota ◽  
...  
Keyword(s):  
Detection Probability ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Density Ratio ◽  
Molecular Ions ◽  
Statistical Properties ◽  
Molecular Ion ◽  
Dst Index ◽  
Low Altitude ◽  
Fast Ion

<p>Molecular ions usually exist only in the low-altitude (< 300 km) ionosphere and cannot escape to space without a fast ion upflow/outflow to overcome a rapid loss due to dissociative recombination (e.g., Peterson et al., 1994). Thus, molecular ion escape from the terrestrial atmosphere to space can be used as a tracer of effective ion loss from the deep ionosphere. Reports on molecular ion observations in the ring current are limited to some event studies (e.g., Klecker et al., 1986) and their statistical properties are far from understood. Here we report observations by the Arase (ERG) satellite which enables definitive identification of molecular ions (O<sub>2</sub><sup>+</sup>/NO<sup>+</sup>/N<sub>2</sub><sup>+</sup>) by frequent TOF (time-of-flight) mode observations (Seki et al., 2019) and a simultaneous observation by the EISCAT radar and Arase to investigate the mechanisms to cause the fast upward ion transport in the deep ionosphere (Takada et al., submitted, 2021).</p><p>Statistical properties of molecular ions in the ring current are investigated based on ion composition measurements (<180 keV/q) by MEPi and LEPi instruments onboard Arase. The investigated period from late March to December 2017 includes 11 geomagnetic storms with the minimum Dst index less than -40 nT. The molecular ions are observed in association with geomagnetic disturbances with Dst < -30 nT. During quiet times, molecular ions are not observed. The tendency is consistent with previous observations. The molecular ions are observed mainly in the region of L=3.5-6.6 and clearly identified at energies above ~14 keV with molecular<sup></sup>to O<sup>+</sup> ion energy density ratio of the order of 1 percent. Detection probability of molecular ions in the ring current becomes higher with increasing size of geomagnetic storms (minimum Dst index). Their detection probability also tends to be higher during substorms as well as during high-speed solar wind period. The observation probability of the molecular ions in the ring current is comparable or higher than that in the high-altitude auroral regions, suggesting the importance of the subauroral zone. Existence of molecular ions even during small magnetic storms suggests that the fast ion outflow from the deep ionosphere occurs frequently during geomagnetically active periods. In order to understand the mechanism of the molecular ion supply to the magnetosphere, we will also briefly report on an event study of the ion upflow in the low-altitude (250-350 km) ionosphere observed by EISCAT during the storm main phase on September 8, 2017, when Arase observed molecular ions in the ring current.</p><p> </p><p>References:</p><ul><li>Klecker et al., Geophys. Res. Lett., 13, 632-635, 1986.</li> <li>Peterson et al., J. Geophys. Res., 99, 23257-23274, 1994.</li> <li>Seki et al., Geophys. Re. Lett., 46, doi:10.1029/2019GL084163, 2019.</li> </ul>

scholarly journals Outflowing protons and heavy ions as a source for the sub-keV ring current

2009 ◽  
Vol 27 (2) ◽  
pp. 839-849 ◽  
Author(s):  
T. T. Giang ◽  
M. Hamrin ◽  
M. Yamauchi ◽  
R. Lundin ◽  
H. Nilsson ◽  
...  
Keyword(s):  
Heavy Ions ◽  
Ring Current ◽  
Particle Interaction ◽  
Heavy Ion ◽  
Local Times ◽  
Cluster Data ◽  
Abstract Data ◽  
Low Altitude ◽  
Field Lines ◽  
Different Characteristics

Abstract. Data from the Cluster CIS instrument have been used for studying proton and heavy ion (O+ and He+) characteristics of the sub-keV ring current. Thirteen events with dispersed heavy ions (O+ and He+) were identified out of two years (2001 and 2002) of Cluster data. All events took place during rather geomagnetically quiet periods. Three of those events have been investigated in detail: 21 August 2001, 26 November 2001 and 20 February 2002. These events were chosen from varying magnetic local times (MLT), and they showed different characteristics. In this article, we discuss the potential source for sub-keV ring current ions. We show that: (1) outflows of terrestrial sub-keV ions are supplied to the ring current also during quiet geomagnetic conditions; (2) the composition of the outflow implies an origin that covers an altitude interval from the low-altitude ionosphere to the plasmasphere, and (3) terrestrial ions are moving upward along magnetic field lines, at times forming narrow collimated beams, but frequently also as broad beams. Over time, the ion beams are expected to gradually become isotropised as a result of wave-particle interaction, eventually taking the form of isotropic drifting sub-keV ion signatures. We argue that the sub-keV energy-time dispersed signatures originate from field-aligned terrestrial ion energising and outflow, which may occur at all local times and persist also during quiet times.

scholarly journals Evolution of low-altitude and ring current ENA emissions from a moderate magnetospheric storm: Continuous and simultaneous TWINS observations

2010 ◽  
Vol 115 (A11) ◽  
pp. n/a-n/a ◽  
Author(s):  
P. Valek ◽  
P. C. Brandt ◽  
N. Buzulukova ◽  
M.-C. Fok ◽  
J. Goldstein ◽  
...  
Keyword(s):  
Ring Current ◽  
Low Altitude

Discovery of energetic molecular ions (NO+and O2+) in the storm time ring current

1986 ◽  
Vol 13 (7) ◽  
pp. 632-635 ◽  
Author(s):  
B. Klecker ◽  
E. Möbius ◽  
D. Hovestadt ◽  
M. Scholer ◽  
G. Gloeckler ◽  
...  
Keyword(s):  
Ring Current ◽  
Molecular Ions

Statistical Properties of Molecular Ions in the Ring Current Observed by the Arase (ERG) Satellite

2019 ◽  
Vol 46 (15) ◽  
pp. 8643-8651 ◽  
Author(s):  
K. Seki ◽  
K. Keika ◽  
S. Kasahara ◽  
S. Yokota ◽  
T. Hori ◽  
...  
Keyword(s):  
Ring Current ◽  
Molecular Ions ◽  
Statistical Properties
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