Dynamics and Photochemistry of N2+ Ion in the Polar Ionosphere

Manabu Yamada, S. Watanabe （ Hokkaido Univ. ）N. Yoshida, Y. Takahashi （ Tohoku Univ. ）

Y. Ogawa and R. Fujii （ STEL, Nagoya Univ. ）

Molecular Ions observed by satellites

In situ observation DE1 satellite, Akeb

ono satellite, etc. Optical observation

MSX satellite

Molecular ions were observed at high altitudes of several thousands km.

DE1 satellite observed molecular ions at several RE.(Craven et al., 1985)

Why molecular ions exist at several thousands km altitudes?

Where is the source? (Altitude, MLT)How to move from low altitudes?

There are methods to observe ions near 1000 km altitudes where ions are heated/accelerated.

Rocket/Satellite．Radar : It is difficult to identify ion species．

Possibility of N ２+ ground based

observation.

Romick et al. [1999] Using MSX satellite, they

observed solar resonance fluorescence of N2

+ ion above 450 km at the Northern polar cap.

Romick et al. [1999]

A new method of ion upflow observation

Optical ground based observation of N2+

1st negative bands resonant scattering. We may monitor cusp structure. We may understand structure of ion heating

/acceleration region and mechanisms of molecular ion upflow.

Observation

Period:25 Nov. 2000 ～ 9 Dec. 2000

Location: Longyearbyen Auroral station

Geographic coordinate 78 ﾟ ,12′,086″N,15 ﾟ ,49′,893″E

Invariant latitude 75 ﾟ 18′N

Kp× 1127 UT 10:15 1217 UT 15:34 5- 3-～○ 1128 UT 15:50 1229 UT 03:19 5- 6+～◎ 1130 UT 10:13 1130 UT 15:09 1+ 2-～○ 1201 UT 14:57 1201 UT 16:34 2+○ 1201 UT 16:45 1202 UT 04:52 2 0～

1202 UT 10:17 1202 UT 11:54 1- 1+～× 1204 UT 14:35 1205 UT 06:12 1 2+～× 1205 UT 06:20 1205 UT 15:15 1 2～○ 1205 UT 15:30 1206 UT 06:17 1○ 1206 UT 06:20 1206 UT 11:41 2-

1207 UT 12:07 1207 UT 16:10 3+ - 2～1208 UT 04:00 1208 UT 07:40 3 3+～

○ 1208 UT 10:48 1208 UT 14:48 3 4～× 1209 UT 05:46 1209 UT 08:20 3+

Observation period

List of all observation

MLT =UT+4.09 [hour] =LT+3.02 [hour]

0

5

10

15

20

25

15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00

Universal Time

Kp

inde

x

2000/ 11/ 28 -

0

10

20

30

40

50

60

70

80

12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00

Universal Time

Kp

Inde

x

2000/11/28-

2000/12/01-

observation

observation

MAIS （ Multicolor All-sky Imaging System ）

Simultaneous observation of 2 wave lengths (6 channels)

427.8nm (N2+1st

negative)

557.7nm (OI)

Exposure: 1min.

Calculation1. Pick up geomagnetic

meridian data.2. Estimate the distance

until the aurora using a peak of 557.7 emission.

3. Obtain altitude profile of N2

+ emission.

Estimation of altitude profile

Assumption1. 557.7nm and 427.8nm are

emitted at same magnetic field line.

2. The peak of 557.7nm emission is 110km.

①

110km

②

③

Θpeak

B

T1

Estimation of N2+ produced by EUV

From data obtained at day time, we can know relation between solar zenith angle and intensity at the zenith.

To differentiate the data, intensities of N2+

emission at each altitude are estimated.

To estimate intensity profile of N2+ emission.

Intensity of N2+ emission

decreases 4 order with the increase of altitudes from 100km to 200km.

T２

Summary

N2+ 1st negative bands emission at several

hundred km altitudes in aurora region could be observed from ground.

We may be able to monitor ion dynamics in the topside ionosphere using N2

+ 1st negative bands emission.

To observe N2+ emission in the cusp region

Improve method of analysis and instrument of observation.

Acknowledgements

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).