Observations of hard X-rays of auroral origin with Polar Patrol Balloons No. 8 and 10

In the Polar Patrol Balloon (PPB) project, two balloons named PPB-8 and -10 were launched in rapid succession to form a cluster of balloons during their flight on January 13, 2003, from Syowa Station, Antarctica. In order to make the two-dimensional images for auroral X-rays and to obtain the energy spectra of auroras with energy range from 30 keV to 778 keV, the same instruments for hard X-rays were installed on PPB-8 and -10, respectively. These detection systems observed several auroral X-ray events during the flight. In particularly on January 25, 2003, strong auroral events were detected at about 0919 UT by PPB-10 and at 0927 UT by PPB-8. The aurora observed by PPB-10 was observed after about 8 min by PPB-8 located a 650 km west of PPB-10. The energy spectra of the bright aurora at 0919 UT and 0927 UT for PPB-10 and -8 is obtained as E0 = (78+-5) keV and (70+-5) keV, respectively

High energy electron observation by Polar Patrol Balloon flight in Antarctica

We accomplished a balloon observation of the high-energy cosmic-ray electrons in 10-1000GeV to reveal the origin and the acceleration mechanism. The observation was carried out for 13 days at an average altitude of 35km by the Polar Patrol Balloon (PPB) around Antarctica in January 2004. The detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillation counters sandwiched between lead plates. The geometrical factor is about 600cm^2sr, and the total thickness of lead absorber is 9 radiation lengths. The performance of the detector has been confirmed by a test flight at the Sanriku Balloon Center and by an accelerator beam test using the CERN-SPS (Super Proton Synchrotron at CERN). The new telemetry system using the Iridium satellite, the power system supplied by solar panels and the automatic flight level control operated successfully during the flight. We collected 5.7×10^3 events over 100GeV, and selected the electron candidates by a preliminary data analysis of the shower images. We report here an outline of both detector and observation, and the first result of the electron energy spectrum over 100GeV obtained by an electronic counter

A convection enhancement event observed with the Polar Patrol Balloon #4

A convection enhancement event was observed with the Polar Patrol Balloon #4 which was launched at Syowa Station on December 26,1992. This event occurred during 1700-1900 UT on December 28,1992,when the balloon located in the afternoon sector of the sub-auroral zone. During this period, the amplitude of the southward electric field (E_S) increased from about 20mV/m to 50mV/m and then decreased to 20mV/m again. The northward component of the magnetic field variation (B_H) also increased from 200nT to 600nT, and then decreased to about 100nT. The maximum time of E_S lagged about 12 min after the B_H maximum time (t_). We could estimate the height integrated ionospheric electric conductivity from these horizontal electric field and magnetic field data. Before t_ Hall conductivity (σ_H) was about two times greater than Pedersen conductivity (σ_P), and after t_ σ_H decreased monotonously to become smaller than σ_P, while σ_P maintained a nearly constant value. Around t_ both σ_H and σ_P were enhanced by about 1.5 times in about 10min, and energetic particle precipitation was observed with the on-board X-ray counter. We could summarize this event as follows : there was stable enough particle precipitation to maintain σ_H before t_ : As E_S increased, the ionospheric Hall current increased, and B_H increased. Around t_ a large quantity of particles precipitated above the balloon, ionospheric conductivities and Hall current reached a maximum value, and thus the B_H reached a maximum value. After t_ σ_H and B_H decreased because the energy spectrum of the precipitation became softer, while E_S continued to increase. E_S reached a maximum value about 12min after t_. From the ground-based data in the southern and northern hemispheres and also satellite IMF data, it was concluded that this event was not an isolated disturbace confined just around the balloon location, but was a global feature of the ionospheric convection variation corresponding to the IMF fluctuation

Auroral X-ray image formings using three directional NaI (T1) telescopes at balloon altitude

This report presents the spatial distributions of auroral X-rays obtained by the balloon flight named AZCO-C1,which was launched from Norway in July 1985. A time sequence of auroral X-ray images were derived by using a set of three NaI (T1) scintillation counters for each of the three different energy channels : 22-35,35-55 and 55-88keV. The precipitation region of energetic particles and its modulations with time were well demonstrated, though the X-ray enhancements were only three times the background flux