Upper Atmospheric and Ionospheric Physics(4.3 Atmospheric Science)

4.3.1.3 Dynamics and Energetics of the Lower Thermosphere in Aurora
Dynamics and Energetics of the Lower
Thermosphere in Aurora (DELTA) campaign

Current understanding
The dissipation of energy controlling thetemperature plays an important role in thedynamics and energetics of the polar lower
thermosphere. Despite its importance, few
reliable observations of the neutral
temperature in the lower thermosphere wereavailable.

Our approach
We coordinated the complimentary
observations as follows:1) In-situ observation of the neutral
temperature and the auroral emission rateby the sounding rocket.
2) Remote observations of the ionosphericplasma by the EISCAT radar
3) Remote observations of thermospheric windand temperature with FPI (Fabry-PerotInterferometer)

Andøya Rocket Range

EISCAT TromsøRocket
NeutralTemp & Density

EISCAT radar
PlasmaE-field

In situRadioRocket-borne instruments
1) NTV (Nitrogen temperature)2) APD (Auroral Particle Detector)
3) AGL (Aurora Photometer)
4) FLP (Fast Langmuir Probe)5) NEI (Impedance probe)
6) CLP (Fixed bias probe)

DELTA
OpticalRocket Launch:0:33 UT 13 Dec 2004

FPINeutral
Temp & Wind

Ground-based instruments

FPIs
Skibotn & KEOPS

1) EISCAT radar (Tromsø Kiruna, Sodankylä)
2) Fabry Perot Interferometer (Skibotn, Kiruna)3) 4-wavelengths photometer (Tromsø)4) All-sky imager (Andøya, Tromsø, Skibotn,Kiruna)5) Sodium Lidar (ALOMAR)
6) MF radar and ionosonde (ALOMAR)

Kilpisjärvi

MuonioProjection alt.
120 kmEISCAT radar observation at Tromsø

SUMMARY

Auroral arc altitude determination by the two ASCimages

BHE70 – 140 K higher
than MSIS Tn

Ne500 KTi

• The EISCAT radar observation suggests that theobserved temperature enhancement is attributedto Joule heating.
• The FPI measurements indicate that the neutraltemperatures are close to the rotationaltemperature measured by the NTV at 120 km.
• The rotational temperature of N2 by the NTV at
95–140 km is 70-140 K higher than Tn fromMSIS, but consistent with the FPI observation.
• The horizontal wind divergence and upwardvertical wind were generated in response to theJoule heating event.

N2 rotational temperature4.3.1.4 Anomalous electron heating in the Sq current focus
Electron temperature increase (heating)at 110 km altitude(Oyama et al., 1993)

Electron temperature
probe

Electron temp. (Te)Suprathermal
Plasma analyzer
Altitude [km]Langmuir probe

Hot Te layer

Electric field probe

Te [K]• Enhanced Te layer at 97-102 km altitude• Significant Ne perturbation above the high Te layer.

Suprathermal plasma analyzer

We try to make in-situ measurementsof the plasma, electric and magnetic
field in the high Te layer by using thesounding rocket to elucidate theanomalous electron heating.

Power spectra of Ne

Magnetometer• In 3 cases out of9, significant
increase (several100 to 1000 K) of
the Te wasobserved at 100
km altitude at1100 MLT inwinter.

Our approachFBP Current (Ne)

Fixed bias probe• Thermal & suprathermal energy
range• Accurate detection of spacepotential• High energy resolution (~ 0.1 eV)

Vacuum gauge
Channel Electron MultiplierElectron acceleration mesh
Orifice and sweep voltage mesh
Sealing cap

π0

Scientific objective0000πππ

At 100 km (upleg)

At 138km (apoapsis)

At 100km (downleg)zDirect observation of thermal andB

suprathermal electrons to investigate
the heating mechanism in the focus of
mid-latitude Sq current system.

ππ0

Non-evaporable getter pump

10% of rocket spin
Wake region withrespect to themagnetic field lines

Enhancement of high energy
electrons at the height ~125km• Cyclic variation of Ne with thespin• No perturbation in the rocket
wake with respect to B
→ Existence of the fieldaligned electron beam?

SUMMARY(Fukushima, 1979)• High Te layer was observed in the Sq current focus.
• The Te was observed to increase by ~500 K at 97- 102 km altitude.
• Enhancement of the electron density perturbation was significantly observed in andabove the high temperature layer, which may be due to the field-aligned electron beam.