Direct interaction between the solar wind (SW) and the Martian upper atmosphere forms a characteristic region, called the induced magnetosphere between the magnetosheath and the ionosphere. Since the SW deceleration due to increasing mass loading by heavy ions plays an important role in the induced magnetosphere formation, the ion composition is also expected to change around the induced magnetosphere boundary (IMB). Here we report on relations of the IMB, the ion composition boundary (ICB), and the pressure balance boundary based on a statistical analysis of about 8 months of simultaneous ion, electron, and magnetic field observations by Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. We chose the period when MAVEN observed the SW directly near its apoapsis to investigate their dependence on SW parameters. Results show that IMBs almost coincide with ICBs on the dayside and locations of all three boundaries are affected by the SW dynamic pressure. A remarkable feature is that all boundaries tend to locate at higher altitudes in the southern hemisphere than in the northern hemisphere on the nightside. This clear geographical asymmetry is permanently seen regardless of locations of the strong crustal B fields in the southern hemisphere, while the boundary locations become higher when the crustal B fields locate on the dayside. On the nightside, IMBs usually locate at higher altitude than ICBs. However, ICBs are likely to be located above IMBs in the nightside, southern, and downward ESW hemisphere when the strong crustal B fields locate on the dayside.

We applied the Grad-Shafranov reconstruction (GSR) technique to Martian magnetic flux ropes observed downstream from strong crustal magnetic fields in the southern hemisphere. The GSR technique can provide a two-dimensional axial magnetic field map as well as the axial orientation of flux ropes from single-spacecraft data under assumptions that the structure is magnetohydrostatic and time independent. The reconstructed structures, including their orientation, allowed us to evaluate possible formation processes for the flux ropes. We reconstructed 297 magnetic flux ropes observed by Mars Global Surveyor between April 1999 and November 2006. Based on characteristics of their geometrical axial orientation and transverse magnetic field topology, we found that they can be mainly distinguished according to whether draped interplanetary magnetic fields overlaying the crustal magnetic fields are involved or not. Approximately two thirds of the flux ropes can be formed by magnetic reconnection between neighboring crustal magnetic fields attached to the surface. The remaining events seem to require magnetic reconnection between crustal and overlaid draped magnetic fields. The latter scenario should allow planetary ions to be transferred from closed magnetic flux tube to flux tubes connected to interplanetary space, allowing atmospheric ions to escape from Mars. We quantitatively evaluate lower limits on potential ion escape rates from Mars owing to magnetic flux ropes.

We applied the Grad-Shafranov (GS) reconstruction technique to Martian magnetic flux ropes observed by Mars Global Surveyor in order to estimate their spatial structures. This technique can provide a magnetic field map of their cross section from single spacecraft data, under the assumption that the structure is two-dimensional, magnetohydrostatic, and time independent. We succeeded in recovering the spatial structure for 70 events observed between April 1999 and November 2006. The reconstruction results indicate that the flux rope axes were mostly oriented horizontal to the Martian surface and were randomly distributed with respect to the typical plasma streamline. A subset of events with duration longer than 240 s was observed at solar zenith angles larger than 75• . These events all occur downstream from strong crustal magnetic field in the southern hemisphere, indicating an association between the crustal fields and the detected flux ropes. Using the shape and size of the flux ropes obtained from the GS reconstruction, we estimate lower limits on their volume that span 2-3 orders of magnitude, with larger flux ropes observed downstream from strong crustal magnetic fields. Estimated ion escape rates associated with flux ropes are of the order of 10 22 -10 23 ion/s, being approximately 10% of previously estimated escape rates during solar minimum.

The penetration boundary of shocked solar wind (magnetosheath) into the Martian upper atmosphere is typically located at altitudes above 800 km. However, magnetosheath plasma occasionally penetrates into low altitudes below 400 km. Here we used Mars Global Surveyor magnetic field and electron observations from April 1999 to November 2006 to investigate the magnetosheath penetration events. We identified 1145 events and found that both solar wind dynamic pressure (P dyn ) and the orientation of the interplanetary magnetic field (IMF) control the occurrence of the events. The magnetosheath penetration events during low P dyn periods tend to be distributed in low latitudes of the northern hemisphere or where the crustal magnetic field is weak, while the event locations are widely distributed in terms of the latitude under high P dyn conditions. During low P dyn periods, a remarkable feature is that the observational probability is approximately 2.4 times larger during periods of the "away" IMF sector than during the "toward" sector. The northern hemisphere during the away sector corresponds to the upward electric field hemisphere due to the convection of draping solar wind origin magnetic flux tubes. These results thus indicate that the magnetosheath penetrations into Martian upper atmosphere more often occur in the upward electric field hemisphere than the downward hemisphere during low P dyn periods. Large-amplitude undulation excited by the Kelvin-Helmholtz instability in the upward electric field hemisphere is a candidate process to cause the asymmetric penetration during low P dyn periods. Another possibility might be the mirror-mode instability by the asymmetric distribution of planetary pickup ions.

Effects on reflectometer phaseφ and powerP fluctuation signals due to (a) asymmetries in the transmit-plasma-receive antenna geometry (misalignments), and (b) asymmetries in the plasma cut-off layer perturbations (distortions from sinusoidal or Gaussian) are studied using a two-dimensional (2D) physical optics model. Results show the onset of phase runaway with antenna misalignment and/or sawtooth type perturbations when the perturbation amplitude exceeds some critical value. For broadband (Gaussian) turbulence antenna misalignment leads to Doppler shifts in theφ spectrum-provided the reflectometer beam width w and spectral width k w of the turbulence are sufficiently large. Misalignment also generates coherence betweenφ andP at Bragg backscatter frequencies with quadrature (±π/2) phase difference. Sawtooth (asymmetric gradient) perturbations also generate phase-power coherence in quadrature, but at frequencies determined by w and k w , i.e. not Bragg. Cusped or spiky (asymmetric amplitude) perturbations generate asymmetric phase distributions (nonlinear phase offsets) and low-frequency phase-power coherence with 0 or π phase difference. The simulations indicate that a combination of antenna misalignment (or plasma tilt) and cusped reflection layer perturbations can account for a wide range of experimentally reported features in reflectometer signals. † On leave

Characteristics of a helicon ion source as a high current density ion source (abstract) Rev. Sci. Instrum. 73, 757 (2002);Extraction of high current Cr ion beam from a multicusp metal ion source Rev. Sci. Instrum. 65, 1269 (1994); 10.1063/1.1145030Ion species measurement of high current metal ion beams extracted from a multicusp ion source Rev.Highcurrent metal ion beam extraction from a multicusp ion source Rev.

A new method combining Li0-beam probing and spectroscopic techniques has been developed to measure local magnetic fields in a bumpy torus. A collimated thermal Li0 beam is injected into the plasma. The Zeeman pattern of the lithium resonance radiation (22S–22P, 6708 Å) is observed with a Fabry–Perot interferometer. The strength of the local magnetic field is determined from the splitting between two π components of the 22S1/2–22P1/2 transition with the spatial resolution of about 7 mm. The magnetic fields from 2 to 4 kG were measured with accuracy of ±2%. This method is applicable to plasmas of a line-integrated electron density below 5×1012 cm−2.

The ChubuSat is a Japanese microsatellite technology demonstration mission jointly depeloped by Nagoya university, Daido university, and medium or small-sized aerospace industrial companies in the Chubu area of central Japan. ChubuSat-2 is the second ChubuSat following ChubuSat-1 which was launched by the Russian DNEPR rocket on November 6, 2014. It was selected as one of the four piggyback payloads of the X-ray astronomy satellite ASTRO-H in 2014 summer, and will be launched by the H-IIA rocket from Japan Aerospace Exploration Agency (JAXA) Tanegashima Space Center (TNSC) in winter season of fiscal year (FY) 2015. The ChubuSat-2 mission is devoted to monitoring neutrons and gamma-rays in the ASTRO-H orbit which can be noise sources for ASTRO-H X-ray and soft gamma-ray observations. The mission involves solar neutron observations which were originally proposed by graduate students who joined the leadership development program for space exploration and research, a program for leading graduate schools at Nagoya University. In this paper, we describe the outline of the ChubuSat-2 satellite and the details of the mission instrument, the radiation detector (RD).