| 著者名 | Authors | 所属機関名 | 所属機関名(欧文) | |
| 1 | #斎藤/享 | Saito/S. | 名古屋大学太陽地球環境研究所 | Solar-Terrestrial Environment Laboratory, Nagoya University, Japan |
| 2 | 野澤/悟徳 | Nozawa/S. | 名古屋大学太陽地球環境研究所 | Solar-Terrestrial Environment Laboratory, Nagoya University, Japan |
| 4 | 藤井/良一 | Fujii/R. | 名古屋大学太陽地球環境研究所 | Solar-Terrestrial Environment Laboratory, Nagoya University, Japan |
| 5 | 松浦/延夫 | Matuura/N. | 名古屋大学太陽地球環境研究所 | Solar-Terrestrial Environment Laboratory, Nagoya University, Japan |
講演予稿:
これまでPedersen電流はイオンのみによって運ばれると考えられて
きた。しかし電場の強い条件下では、Farley-Buneman不安定によ
る波動が電子を散乱し、電子によるPedersen電流を生じさせる。
電子のエネルギーバランスを、EISCAT CPデータおよび種々の
モデルを用いることによって解析し、電子によって運ばれる
Pedersen電流を定量的に評価した。その結果、電場が非常に
強い場合には、電子による高度積分されたPedersen電気伝導度に
対する寄与は、イオンのそれの２５％に達することがあることがわ
かった。また、電子Pedersen電流の強い領域と、オーロラアークと
の関係についても述べる。
abstract:
In the ionosphere, there are two field-perpendicular
currents, Hall and Pedersen currents, respectively. Up to
now, it is believed that electrons would collide with
neutrals so rarely that Pedersen current would be carried
by ions only. The present study shows that it is not always
true, that is, electrons sometimes contribute to Pedersen
current significantly.
When the electric field is stronger than the threshold
value ( typically about 20 mV/m), electrons are heated up
by unstable Farley-Buneman wave through effective
collisions at a frequency comparable to the electron
gyrofrequency (e.g. Sudan, 1983), which means electrons are
strongly scattered.
When the electrons are strongly scattered, the direction of
electrons' drift would deviate from ExB direction resulting
in a dissipative Pedersen current carried by electrons.
Since the heating rate of electrons and electron cooling
rate must be balanced, it is possible to estimate how
strong electrons contribute to Pedersen current. We have
examined carefully the relationship between the observed
electric field and the other ionospheric parameters, such
as electron temperature, ion temperature, and electron
density. The present study shows that for very strong
electric field cases the height-integrated Pedersen
conductivity contributed by electrons becomes up to 25% of
those by ions. The electron heating events are often very
short-lived events. A relationship between the strong
electron Pedersen current events and auroral arcs will also
be presented.
Acknowledgment. We are indebted to the director and staff
of EISCAT for operating the facility and supplying the data.
EISCAT is an International Association supported by Finland
(SA), France (CNRS), the Federal Republic of Germany (MPG),
Japan (NIPR), Norway (NFR), Sweden (NFR) and the United
Kingdom (PPARC).
キーワード:
極域電離圏, 電流, 電子加熱, EISCAT, オーロラ
Keywords:
polar ionosphere, current, electron heating, EISCAT, aurora